Laying of power cables and cable lines. Laying an electric cable in the ground: conditions and procedure for performing work Laying power electric cables

Laying cables in the ground is increasingly becoming the responsibility of DIYers. Organizations operating power and communication networks are now unable to maintain a planned-unprofitable army of fitters, and for this reason, the repair of unreliable air inlets is too expensive. In addition, now people are trying to build not by the road with pillars along it, in order to be closer to nature. In such conditions, it is often technically impossible to install an air entry into a building. However, laying a cable in the ground is much more expensive than a "air" device, but at the same time, it is do-it-yourself. Therefore, private homeowners spare no effort and time to ensure themselves a reliable electricity supply. This article is intended to explain how to properly lay your own cable in the ground.

Gordian knot

The power cable must be laid in compliance with applicable requirements and regulations, regardless of who leads it. The rules for the construction of power grids and their safe operation are regulated by a variety of regulatory documents from those having the force of law to sets of rules (SP) for the production of specific types of work and job descriptions for employees. Between them are intersectoral, sectoral, departmental and production rules in the rank of bylaws. These are not the fruits of bureaucratic rule-making. After all, as they say, it is a no brainer that the power supply of a residential building, hospital, metalworking workshop, train and ship cannot be organized uniformly. In this case, from the vaults at the top of the hierarchy, i.e. having the force of law, we need the Rules for the Installation of Electrical Installations of Consumers (PUE), with a continuous look at the Safety Rules for the Operation of Electrical Installations by Consumers (PTB).

"Holy Trinity": PTB, PUE, PTE(Rules for the technical operation of electrical installations of consumers) and their "colleagues" for electrical workers, constituting the "ruling elite" are written, like army regulations, in human lives and huge material losses. Due to the wide range of topics in them, it is far from always possible to find a direct answer to a question like: "What and how to bring the cable to this particular house, if such a tree is sticking out in front of it?" Sometimes a specialist with a higher electrical education, work experience of about 40 years and, in addition, the 6th working category of the cableman has to break his head - how can everything be done to make it work safely, reliably, and the owner's wallet is not turned inside out. This is the essence of electrical standards, as the essence of charters - to achieve victory at the cost of the least losses.

For example, Ch. 1 and 2 of the PUE of the 6th edition (the 7th is not yet fully completed). But looking for a cable brand for a specific job in the PUE is useless: everything that can be extracted is the cable must be operated according to the manufacturer's specifications, technical specifications for this type of product and be reliably protected from external influences. There is also a recommendation in clause 2.3.37 to use mainly armored cables, but they are expensive and far from equal in quality. At the same time, GOST 15845-80 "Cable products" (terms and definitions) reads (literally):

“CABLE PRODUCT - an electrical product intended for the transmission of electrical energy, electrical information signals or used for the manufacture of windings of electrical devices, characterized by flexibility.

ELECTRIC CABLE (Cable) - a cable product containing one or more insulated conductors (conductors) enclosed in a metal or non-metallic sheath, over which, depending on the conditions of installation and operation, there may be an appropriate protective cover, which may include the armor, and suitable, in particular for laying in the ground and under water.

ELECTRIC WIRE (Wire) - a cable product containing one or more twisted wires or one or more insulated conductors, over which, depending on the conditions of installation and operation, there may be a light non-metallic sheath, winding and (or) braiding of fibrous materials or wire, and not intended, as a rule, for laying in the ground ”.

"In particular" and "as a rule" in the document of force of law is the subject of a special conversation; one can only notice that the Russian Federation is not at the forefront of the world's leading powers. GOST 571.15-97 is formulated somewhat differently, but the problem - where and how to lay which cable - is not solved, and an error due to "in particular" and "as a rule" can cost life. Perhaps an accidental passer-by who has fallen under a step voltage. The owners are still responsible for the answer. now the wiring from the pole or TP (see below) to the house is their property. The principle of responsibility "home" died quietly along with the USSR.

One of the author's acquaintances during it said: “If I didn’t always know exactly when the charter should not be violated in any way, when it is possible, and when it is necessary, I would have resigned as a colonel. If I always did everything according to the charter, I would be dismissed by a major. And so - lieutenant general, and still serve! "

We in this publication do not intend to make anyone a general or even a sergeant. We will tell unprepared readers how to properly lay a cable in a trench so that the supervisory authority accepts the job, gives the go-ahead for operation, and then there are no problems with cable entry for at least 40 years. Not in the form of a tedious enumeration of the PUE items, which the inspector of the RES (electric grid region) knows anyway better than you, but what and how to do so that the same inspector nods his head approvingly and signs the commissioning certificate.

Procedure

Homeowners may need to lay an electric cable in the ground not only for power input equipment, but also for wiring it around the site in order to provide electricity to the following secondary consumers, in descending order of priority:

• Powering the water supply pump and other vital devices and units with electricity.
• Power supply for utility rooms.
• Security alarm and outdoor lighting connections.
• Lighting for the garden, gazebos and other resting places.
• Power supply for the pump and illumination of the fountain, pond and other decorative objects.
• Power supply to other secondary consumers.

Regardless of the nature of the consumer, the requirements for the supply of the power supply cable to it are unchanged, because the danger of electric shock, responsibility for its consequences and the cost of electricity are the same. In essence, only the connection diagram to the power supply is changing, see below, as well as about the smaller nuances of the "master" wiring on the site. The laying of the electric cable in the ground is carried out in the following order:

1. The material of the cable conductors is selected;
2. According to the consumption rate, the maximum consumed current and the connection diagram, the cross-section of the current-carrying conductors and their number are calculated;
3. According to local conditions, the type of cable is selected and its footage is calculated;
4. The presence of third-party underground utilities and obstacles on the path of the proposed cable route is determined, and methods of crossing / bypassing them are also determined;
5. Sketches of the cable route, entry into the building (exit from it for wiring through the site) and connection of secondary consumers for the site network are drawn up;
6. According to pp. 1-5, a work plan (PPR) is drawn up and approved by the local supervisory authority (RES, department of the municipality);
7. Digs / digs trench / trenches for cable / cables;
8. The inspector of the supervisory authority is called to accept the trench. The indicated shortcomings are corrected, a repeated call for acceptance is made, etc. until the trench is accepted;
9. Ro its acceptance works are carried out on the laying of the cable, possibly with supervision, see below;
10. After laying the cable, its electrical measurements are made by a specialist of the supervisory authority (their payment, as a rule, is included in the cost of acceptance);
11. In case of a favorable result according to clause 10, the cable is connected to the input-distribution device (ASU) or the input board (VSC) of the house. Secondary consumers are also connected to the network at the site. It is permissible to carry out works under item 11 independently;
12. Representatives of the energy supplying organization are called to connect the cable to the local overhead line, transformer substation (TP) and other power supply source. If the house will be powered from the TP, then the cable entry and connection is carried out only by employees of the power supply organization. In this case, the plan in the PPR (see below) should indicate how long you need to lead the trench yourself;
13. Upon connection to the power supply, a representative of the supervisory authority is called to perform a test switch-on and take the primary readings of the electricity meter;
14. According to the favorable result of clause 13, an act of acceptance and commissioning of the cable line (network at the site) is drawn up and signed by the inspector of the supervisory authority.

Note: if the house is connected from the air power supply, "from the pole", then PP. 12 and 13 can be combined and produced by an employee of the power supply organization with a working qualification, endowed with acc. powers from the supervisory authority.

Underground cable

Cu or Al?

That is, should I take the cable with copper or aluminum conductors? It would seem, what kind of question? Any household electrician knows that aluminum is bad and copper is good. In fact, it is bad - aluminum mixed with copper, tk. a contact potential difference arises on the twists, which is why they heat up. And as for the hidden wiring (cable in the ground is its kind), the requirements of the PUE in this case are quite definite, p. 2.1.49:

“For stationary electrical wiring, mainly wires and cables with aluminum conductors should be used. For exceptions see 2.1.70, 3.4.3, 3.4.12, 5.5.6, 6.5.12-6.5.14 [in 7th edition 6.6.15-6.6.20], 7.2.53 [in 7th edition edition 7.2.51] and 7.3.93 ".

A cable laid underground, if its ends are equipped with lugs that ensure reliable contact with the ASU / VSC terminal blocks, is not included in the list of exceptions. Are you surprised? Take 2 wires of the same diameter, copper and aluminum, and try to bend them. Which one is easier to bend? And now we bend-unbend until a break appears. Which one withstood more? It remains to remember that a cable in the ground is subject to slow mechanical stress from ground movements. Aren't you surprised now? PUE written by the smartest and most experienced people. There is, however, an option when copper in the ground will be more reliable: a cable with oxygen-free copper conductors. But it costs so much that it will be a little more expensive to lay a silver one.

Note, from the statements of the same familiar author:“Charters are written by brilliant people. Just think about it - to paint our whole life so that the last fucking ... it was clear! "

And one more argument in favor of aluminum conductors: a cable with them for the same power is lighter and will withstand a greater slope when laying. When crossing existing communications and avoiding obstacles (see below), this circumstance may turn out to be critical.

Section of veins

The calculation and selection of the cross-section of current-carrying conductors and wires are considered in Ch. 1 PUE. There is a table for the cable. 1.3.4. If we compare the results on it with those for calculating the cross-section of the house wiring conductors, see eg. video below, you get a clear overstatement towards the cable. Caused by this trace. reasons:

• The heat dissipation conditions in the ground are worse than in the wall.
• The cable sheath is thicker, which makes the heat dissipation from the cores even worse.
• The cores of the cable for the whole house are also thicker, i.e. the ratio of their surface to volume is less, which further worsens the heat dissipation.
• A cable in the ground is subject to mechanical stress, which is transmitted to its cores, incl.

Video: selection of cable cross-section, mistakes

Video: how to calculate the cable cross-section

Proceeding from this, the norms of the PUE for the cross-section of the conductors of the cable for electrical entry into the house are as follows: copper is not less than 12 sq. mm, aluminum at least 17 sq. mm . If the calculation for power / current gives a higher value, it should be taken. However, from practice, we can conclude that the current-carrying conductors of the cable for entering the house must be taken with a cross section of 20 sq. mm: cables with a minimum permissible cross-section of conductors account for more than 80% of ruptures due to ground movements. And along a vein of 20 squares at a current density of 5 A / sq. mm (this is normal for a private house), at 220 V, a power of 22 kVA can be transmitted, which is 2.2 times more than 10 kW, which a private household can consume, paying at the usual rate. The safety factor of 2.2 gives the service life of the entire bushing, which is practically equal to the service life of the cable; usually at least 40 years of age. The trace is also important. circumstance: "alternative" manufacturers, incl. domestic, systematically underestimate the cross-section of veins against the declared one. Therefore, a cheaper cable needs to be bought not on the Internet, but on the spot, and with a barbell.

Note: the district wiring from the house of the PUE of the previous editions is not unambiguously standardized. In practice, it is considered as a house / apartment one, given a consumption current 1.6-1.7 times greater than the real and the minimum permissible core section of a 3-wire cable 2.5 sq. mm, subject to the mandatory presence of protective grounding and automatic protective shutdown, see below.

Which cable to take?

A wide variety of underground cables are available on the market. Choosing a suitable cost for yourself, you need to be guided, in addition to the reputation of the manufacturer and seller (these days this is especially important), and by the design of the cable. It should include elements, composition and purpose, we will consider using the example of well-proven samples. Quite simply - take cables that are structurally similar to these.

Cables AVBbshV (conductors - aluminum) and VBbshV (copper conductors) for general purpose, i.e. for laying in normal conditions. Explanation of designations: A - aluminum conductors; B - PVC insulation; Bb - conventional type steel tape armor (2 tapes with 50% overlap) with a bituminous cushion, but without an additional plastic cushion; Shv - in a PVC hose.

Cables AVBbshv and VBbshV are produced with the number of cores 1, 2, 3 (for single-phase wiring with a separate grounding conductor PE), 3 + 1 (3 phases and a neutral of a smaller cross-section for 3-phase networks with a dead-earthed neutral), 4 and 5 - conductors for systems with insulated neutral. The conductors are round or sectorial, solid or twisted with a cross section of 2.5-626 sq. mm (solid) and 2.5-240 sq. mm (twisted). In AVBbShv and VBbshV with current-carrying conductors up to 6 sq. mm there is no bituminous cushion under the armor.

AVBbShv and VBbshV are intended for laying in the soil of normal bearing capacity (from 1.7 kg / sq. Cm) and normal chemical activity not watered, not subsiding and not excessively heaving. The permissible total slope along the entire length of the route depends on the material and cross-section of the conductors, but for capacities up to 10 kVA it will meet the norms if it does not exceed on the route up to 100 m with a length of 1:15 for aluminum and 1:20 for copper. The working temperature range of AVBbshv and VBbshV is from –50 to +50 degrees Celsius. They consist of (left and center in the figure):

1. Live conductors;
2. Core insulation;
3. Belt insulation made of PVC, tightening the bundle of cores;
4. Additional wrapping made of polyethylene terephthalate (PET) for cables with conductors from 6 sq. mm;
5. Bituminous cushion;
6. Armor;
7. External insulating hose - sheath.

Cables PvBbShp and PvBbPg (on the right in the figure) are deciphered as:

• PV - cross-linked polyethylene core insulation.
• Bb - regular 2-tape armor without a plastic cushion.
• Шп - external insulating polyethylene hose.
• PG - a polyethylene hose with additional sealing with waterproof tapes (swell in the presence of literally individual water molecules).

PvBbShp and PvBbPg are intended for laying in difficult conditions: in unstable, weak, chemically active and watered soils (except for swampy and swampy), up to laying in reservoirs with a stable hydrological regime and a stable bottom. PvBbShp and PvBbPg, like any other cables, must not be placed in the swamp. In a swamp, in exceptional cases, it is permissible, in the light on an overpass. PvBbShp and PvBbPg can be laid without additional protection measures in the area of ​​operation of stray currents (see below). The admissible slope of the route is up to 45 degrees in the section up to 30 m and up to 30 degrees in the section up to 100 m. The admissible temperature range is –50… + 50 Celsius; let's say heating up to 120 Celsius for 6 hours. Special installation conditions: strong tensile forces are unacceptable, therefore, when pulling sections over 30 m into a clean free channel, intermediate stockings must be used, see below. PvBbShp and PvBbPg tightening into channels with operating cables is possible in agreement with the supervisory authority and organizations operating other cables, and it is unacceptable to float into channels that have swum.

PvBbShp and PvBbPg are produced only for 3-phase networks with bundles of copper conductors 3 + 1, 4 and 5. The cross-section of conductors is 4-50 sq. mm solid (single-wire) and 16-240 sq. mm twisted from many wires. PvBbShp and PvBbPg consist of (on the right in the figure):

1. Live conductors;
2. Core insulation;
3. Supporting core made of fiberglass;
4. Spiral winding, tightening the bundle of cores - for cables with cores from 50 sq. mm;
5. Belt insulation, which serves as a damper cushion of armor at the same time;
6. Armor;
7. External insulating hose.

Note: Lead-sheathed cables are still being produced, since their real service life exceeds 100 years and they clutch more reliably than plastic ones (the reliability of a lead-based clutch is not less than that of a solid shell), but very expensive. If you fork out for this, remember - you must lay the cable in lead strictly horizontally!

Veins

Solid or twisted conductors of the cable are essential for the technology of their production, but it is also important when choosing a cable. Cables with twisted conductors are more reliable in moving soils, but light, loose and less pressing on the cable - sand, loam, light sandy loam, gravelly and gristly. That is why PvBbShp and PvBbPg are produced only in copper in PE: the coefficient of friction of copper on copper and on polyethylene is less than that of aluminum on aluminum and PVC; as you can see, even in the PUE there are no rules without exceptions.

More about the colors of the insulation of the veins. PCT / GOST once again gave birth to its standardization, but these births, like the previous ones, are premature. Firstly, the colors for 1-phase, 3-phase networks with isolated and solid-grounded neutral are not coordinated. Secondly, the market is full of foreign-made cables, whose manufacturers GOST is the flag of Moldova. Only the color of the PE grounding wire is exactly observed; we still have to remember about it - yellow with a longitudinal green stripe. The neutral color N is more or less observed - blue or blue. But at the same time, the sale is full of single-phase cable with black / brown and gray / white wires. Should it be used for interphase 380 V without zero? In general, when splicing cables, carefully observe PE and N, and tie the rest of the colors as far as possible to a previously laid cable or an existing one.

Wandering currents

Electric currents circulating in the ground are one of the most serious sources of cable accidents. destroy its outer shell and armor. In addition, stray currents can induce dangerous voltages on a cable disconnected from the power supply. The main sources of stray currents are rail electric transport and metallurgical production, but they are also provided by any electrical installation with a working ground, for example. baking oven. The USA is full of problems with stray currents from popular public laundromats there. Water pipes are also the source of stray currents: flowing water is a conductor moving with the Earth's magnetic field.

Best of all protects cables from stray currents so-called. anode protection, but this is a very difficult and expensive measure, incl. and for running costs: aluminum protectors need to be periodically replaced with new ones to replace those eaten away by electrocorrosion. Sufficiently effective protection against stray currents - laying the cable in a plastic hose in an insulating channel; both should be normalized to the degree of moisture diffusion, see below.

And if without armor?

An armored cable is much more expensive than an unarmored wire for the same power. At the same time, the armor protects the cable from rodents and manual digging, but it is powerless against earth-moving equipment (see below). With a lack of funds in the budget, the question is: is it possible to lay unarmored wires in the ground and, if so, which ones and how? - quite legitimate.

It is possible, but not all sorts and not randomly; several degrees of cable protection are required. First, HDPE pipes provide a fairly reliable protection against rodents and manual digging, see below. Second, the outer sheath of the wire must withstand the chemical activity of the soil and also be unattractive to rodents. Third, an unarmored wire can be laid in the ground in your area, where no one will dig without your knowledge, and you know exactly how the wires go. Fourth - outside the site, say, from the fence to the support with a switchgear (box, simply), the cable must be protected with a signal tape of increased width (see below) in combination with an additional protective layer; better - concrete, also see below.

It remains to figure out which wires can be put into the ground. PUNP, PUGNP and bad memory rubber KG (above in the figure) since 2007 has been prohibited from using in newly built networks due to the high accident rate they create. CG electricians of past times called each other the obscene name of a condom. VVG, AVVG, PVS, NYM (below in the figure) and others of a similar design (PVP, PBPP, etc.) have proven themselves well in internal wiring, but they cannot be put into the ground: their shells are not normalized for moisture diffusion. Simply - mechanically, a whole such wire in the ground can lock.

For laying in the ground from unarmoured wires, firstly, NYY-J is suitable, at the top in Fig. on right. Its thick outer shell is made of dense rubber or similar plastic; it is normalized in terms of diffusion and is unattractive to rodents, except for those who are completely mad from overpopulation. Analogs NYY-J are on sale, but you need to take them from a reliable manufacturer, with a certificate of suitability and a guarantee. For wiring from home to the site, in the presence of protective automation (see below), you can use PvPg (same place below); they can even supply power to the submersible pond filter motor. The moisture resistance of PvPg is provided by a sealing winding under the insulation of the cores and the outer shell, but rodents grind their teeth about it more willingly, therefore it is advisable to lay PvPg in the ground in a metal hose or HDPE corrugation.

Tricky notation

You have probably already noticed the addition of –ng to PvPg in Fig. This is the first of the additional property suffixes important for underground cable. -Ng means non-combustible, combustion does not spread over it when laid alone and in bundles. Suddenly an accident, it will be localized and elimination of its consequences, perhaps, will do without replacing the entire line.

The second thing is -hf (halogen free, no halogens). This suffix is ​​often used to counterfeit cable products in order to increase the cost. For example, the sale is full of VVG-hf. But, excuse me, what kind of "halogen free" can a PVC insulated cable have? The only thing that you can expect to buy from such a seller with a 100% quality guarantee is noodles for teapots.

As for other suffixes characterizing the toxicity of the insulation, the volume of gases emitted by it in the fire site, filling the cavities of the bundle of veins with talcum or non-combustible plastic powder (such a cable can be bent along a small radius), etc., they can be significant in internal wiring, but for a cable laid in the ground, they are not particularly important.

Note: the golden rule when choosing a cable yourself - do not take cables with oil and other hydrophobic filling! They are for special applications, and then hassles and unforeseen expenses will be unimaginable on their own site!

Alignment, Inputs, Intersections and Inputs

In this step, we will look at the alignment and the post-to-house building entry device. The features of the wiring of the power supply network for the site were partially indicated above, and we will deal with the rest further.

Track

It is strongly recommended to route the power cable in straight sections. Tracks - "guts" - a nightmare for electricians: they are highly accidents, and the consequences of accidents on them are difficult to eliminate. But it is also impossible to make the corners of the route straight: the bending radius of the cable must be from 20 of its diameters, and the cable must not touch the walls of the trench, see more about this below. How the corner of the cable route is correctly performed is shown in Fig. on right; for one cable, only the size A and the profile of the trench change, see also below.

Input and inputs

General diagrams of cable entries into the building are given on the next page. rice. On the left is an old typical one with steel pipe elbows. It is still widely practiced, despite serious shortcomings. First, stray currents are drawn to steel pipes. Second, when a building or cable shrinks in the ground or ground moves, the edge of the steel pipe can cut into the cable. As for the supposedly increased security of the overhead sections of the cable, with the current power tool and the economic feasibility of stealing electricity and non-ferrous metal, it is already a fiction.

Note: in this section, another advantage of cables with aluminum conductors is manifested - it is just as dangerous to steal them, but much less profitable than copper ones.

Much more reliable in modern conditions is a pipe for laying a cable made of low-pressure polyethylene (HDPE). The diagram of the cable entry in the HDPE pipes is given in Fig. in the center. Advantages of HDPE pipes for cable laying over other weights:

• HDPE is unattractive to rodents: it is too viscous and slippery for the point of the teeth.
• HDPE, provided the pipe joints are sealed with silicone, insulates the cable from groundwater and stray currents.
• HDPE pipes for cable laying are produced incl. with embedded in them "rods" - broaches made of steel wire.
• The cable goes into the HDPE pipe much easier and the probability of its damage when pulled into the channel is much lower.
• Due to their lightness and flexibility, a cable duct made of HDPE pipes can be assembled in the light (on the ground above), and then simply put it into a trench together.
• The overall strength and elasticity of corrugated HDPE pipes are quite high, especially double-walled ones. This practically excludes damage to the cable in the ground with a hand tool and several times reduces the likelihood of its rupture by earth-moving equipment.

Note: HDPE pipes for cable channels must be taken with a clearance diameter of at least 20 mm larger than the outer diameter of the cable. Bending radius of cable ducts - from 20 diameters of the thickest cable pulled into the duct.

On the right in Fig. a diagram of cable entry into a house on a pile or columnar foundation is given. Such a design of the electric cable entry at the dacha radically reduces the possibility of unauthorized connection from the outside in the absence of the owners.

Note: corrugated pipes of any type are often marketed under the general name "corrugation". In fact, the corrugated pipe for the cable is necessarily equipped with a standard broach inserted inside, and if the pipe is without broach, then this is a corrugated hose.

The design of its direct entry into the building should be the subject of special attention when developing the sketch of the cable route: most of the power supply failures are due to faulty cable entries into houses. In fig. given drawings of typical designs of cable entries into a house with a basement and a basement, and in fig. on the right, it is shown how the external entry into the subfloor through the base in the HDPE pipe is arranged. In this case, the sealing cuffs can be replaced with silicone sealant.

Intersections

When developing schemes for crossing existing communications by cable and avoiding obstacles, it is necessary, firstly, to minimize their number as much as possible. Practice shows unambiguously: it is better to buy excess cable in order to circle all the "mess" with it and at the same time straighten the route. In the future, the initial cost overrun is repaid many times over by saving on emergency recovery work. The design method “ahead of the curve, if only it is shorter” is one of the reasons for the collapse of the economy of “developed socialism”. Second, one should strictly adhere to the minimum permissible distances (a value that is opposite in meaning to the approach, but expressed in the same units of measurement) of the cable from the crossed objects and obstacles:

• From the foundations of the house, outbuildings, columns, supports, etc. - 0.6 m, except for the entrance to the building.
• From "own", "master" cables (wiring from the house to the site) - 0.1 m.
• From communications of third-party organizations (except for gas pipelines and heating mains), if the cable and existing communications for voltages up to 10 kV - 0.25 m, subject to mandatory agreement with the operators.
• From the underground gas pipe to the house (not the main one!) - 0.5 m.
• From the heating main - 2 m or, if there is an additional one on it. thermal insulation, which reduces the overheating of the immediately adjacent soil to 10 degrees or less - 0.5 m.

If the cable runs parallel to the pipeline in some section, its distance from the pipe must be kept from 0.5 m or, if the pipe is a heating main without additional insulation, at least 2 m. The cable running parallel to the pipelines must be laid away from the pipes, not below or above them.

Note: the value of 2 m was taken for a reason. This is double the width of the security zone of the cable (see below). For 2 m and further, a cable can be used to access any communications up to 10 kV without agreement with their operators.

Also, no closer than 2 m can be approached with a cable to the trees, see below. Typical schemes for crossing existing communications with a cable, except for the gas pipeline, are given in Fig. The cable crossing the collectors should be avoided in every possible way. Construction of the collector is an expensive and labor-consuming task. Even if the collector is buried normally, the cable above it turns out to be shallower than necessary for safety reasons.

Suddenly, the intersection according to the typical scheme fails, do not be wise, this is not the case when fresh ideas can be useful. Seek advice from a specialist of the supervisory authority, you still cannot do without this, see below. In some cases, it is possible to converge intersecting communications up to 10 cm and protect the cable instead of the pipe with a sheet of flat slate, etc. non-combustible non-fusible material. But - only in agreement with the supervisory authority. That is, you go to the RES or who is there supervising you, show the sketch: this is the problem, what to do? They explain to you, and you follow exactly as directed.

Crossing a gas pipeline with an electric cable

A special case is when a cable crosses a gas pipeline. At the same time, the distance is maintained, as a rule, without problems - the gas pipes are buried deep. But in the process of laying the cable, sparking and damage to the insulation of the gas pipe must be excluded. A typical diagram of a cable crossing a gas pipeline is shown in Fig. The supporting beam-log and hangers are removed only after full backfilling of the trench to the level of the top of the box. The box remains in the ground.

How to deal with trees

A garden, ornamental tree plantation or a piece of forest on the site is great. But, how, if it were wrong, to pass such a grove with a cable, without approaching the trunks closer than 2 m? A dense planting - nothing but a bypass. It is impossible to get around - you will have to abandon the underground input in favor of the air one. More or less reliable "air pipes" are built from self-supporting insulated wire - self-supporting insulated wire. If 1-2 trees interfere, then punctures (horizontal wells) can be made under the roots at a depth of 900 mm (T10-T15 trenches, see below). An asbestos-cement or steel pipe is laid in the puncture, protruding to the sides for at least 2 m counting from the trunk, but outside the root system.

A puncture in the ground under the cable is made with a special pneumatic tool for horizontal drilling - a mole. Cable operators avoid punctures without urgent need (for example, under the road) in every possible way, therefore specialized firms are wielding moles. Their work is expensive, and a puncture under a tree will be even more expensive, because the probability of losing a projectile in the roots is greater. In this case, if hard work is not a pity, you can pierce the channel under the cable (more precisely, the pipe for it) manually:

• On both sides of the tree, pits are dug from 2x1 m in plan and from 1.5 m in depth, oriented along the length along the route.
• The starting points of the puncture are marked by a compass or GSM indicator in the direction and a hydraulic hose level in depth.
• The puncture is made with a hand auger drill with sharply sharpened cutting edges alternately from 2 sides to the collapse.
• In the process of drilling, the horizontal position of the drill is periodically monitored.
• After hammering, the well is drilled again with the same drill with an elongated steel pipe with a rod, so that the puncture channel is obtained without a ledge.

Trenches

Profile of the most common power cable trench and cable laying scheme in it

The profile, dimensions and scheme of laying the cable in a trench, suitable for the entire moderate band of the Russian Federation and therefore the most common, are shown in Fig. on right. From the bottom and sides of the trench, there should not be any sharp, hard and other objects that could damage the cable, for example. living tree roots. That is why the “bare” trench must be inspected by a representative of the supervisory authority prior to the start of cable laying.

The sides of the trench in dense stable soils (clay, loam, dense heavy sandy loam, podzol) can be steep. In many cases, this makes it possible to do without manual digging, see below. Backfilling the cable with sifted excavated soil instead of sand is permissible in places with a standard freezing depth of less than 600 mm on loose loose dry soils - sand, sandy loam, fine rounded gravel and cartilage. You can save a lot on the purchase of sand.

A pipe (preferably asbestos-cement) cable is protected under any passages for self-propelled vehicles, even if it is a scooter path. Shocks and vibrations are transmitted into the ground deeply, strongly and can damage the cable. Removal of the pipe beyond the edge of the passage - from 1 m. The signal tape and the hard protective layer will be discussed below.

It is also impossible to reduce the cable laying depth to less than 700 mm in places with non-freezing soil for safety reasons, but in certain cases (see, for example, crossing patterns and a puncture under a tree), it may be necessary to deepen the trench, as in regions with a standard freezing depth over 900 mm. A diagram of a typical profile of a power cable trench with a table of dimensions and values ​​for calculating labor and material consumption is given in Fig.:

In the course of the route, the trench of one profile can go into another; then the slope of the transition section must be maintained within the specifications for the cable used.

Note: in permafrost soils, it is generally impossible to lay cables in trenches. Only in collectors or overpass.

"Signalka"

The signal tape (see the inset at the bottom left in the figure with the "supply" trench) has proven to be a very reliable means of protecting the cable and now it is allowed to lay power cables in trenches under the signal tape without additional protection with a hard covering. The standard width of the tape is 250 mm, but for a section of the route outside the boundaries of the household it is highly desirable to take a tape of a larger width, even expand the trench to 600 mm and lay the same tape.

The fact is that the "signaling" gives a reliable signal only to the operator of the bucket excavator, on the left in Fig. If a trench across your cable is being dug with a chain trench excavator (trencher; simply a bar) in the center, then when the chain brings up orange patches of tape 250 mm wide, the operator will have no time to stop the machine before the digger's teeth crash into the cable ... But in the case of a 600 mm tape, the time to pull the levers will be at least 5 seconds; this is enough for an attentive operator of average and below average skill, and the mechanic will have time to react to his actions.

The issue of a wide signal strip is all the more relevant since chain trenchers on the chassis of mini-excavators are rented with delivery to the work site, and you can learn how to operate them in half an hour (on the right in the figure). cable network on the site: a bar on a Bobcat chassis with a 13.5 kW engine with a 250-mm chain digs ordinary, not heavily clogged soils to a depth of 900 mm. And to enter the house with a bar, you can dig a pioneer trench, but keep in mind: only from the house to the border of the site. Otherwise, there will be a serious violation of traffic rules and land use rules if you do not have a tractor excavator driver's license and local authorities' permission to work with special equipment outside your territory.

Note: It is convenient to use a trencher to fill up a dug trench - the working body is lifted and driven back along the cable route by turning on the raking augers for reverse rotation. It remains only to tamp the resulting neat bed.

Brick or concrete?

Additional protection with brick protects the cable from careless manual digging, and reinforced concrete and from mechanized digging. The teeth of the chain digger do not take concrete, and the bucket excavator, having hooked the slab, crouches and twitches so that the drunk operator will wake up and wake up. Technique, so to speak, gives a pendel to a muddler. Protection with reinforced concrete may turn out to be cheaper than brick protection: any used slabs with a thickness of 40 mm or more, placed in a trench, are suitable for it, even if they have up to 10% of the reinforcement exposed at the edges.

Bricks for cable protection are laid tightly across the trench dry. For protection, you need to take a solid working brick (red). Silicate and facing bricks in the ground quickly degrade, releasing substances that corrode the cable sheathing. Additional solid cable protection is needed in the following areas:

• At the entrance to the building from the wall of the house or the edge of the blind area around it - by 2 m.
• For non-armored wire under driveways, despite the protective tube, with an offset equal to the offset of the pipe ends.
• At intersections with existing communications, if the standard cable burial is not maintained.
• Outside the boundaries of the site - highly desirable; if an unarmoured wire is laid, it is obligatory.
• On cable sections passing under a vegetable garden, flower bed, etc. places where earthworks are regularly carried out.

PPR

The cable work plan is like a hybrid project with a budget. The sketch of the PPR for the power cable should contain:

1. Explication of the site plan, indicating the location in the light (i.e., as if visible through the ground) and the depth of the existing communications;
2. Calculation of the cross-section of current-carrying conductors and justification of the choice of the type of cable;
3. Plan-diagram of the cable route with a section of the trench profile and a scheme for laying the cable in it. If the profile and / or the laying pattern along the route changes, cuts are needed for each section;
4. Diagram of the cable channel, if it is made in one piece from HDPE pipes;
5. Diagrams of intersections of existing communications and obstacle avoidance;
6. Scheme of cable entry into the building;
7. Connection diagram to the home ASU and protective automation (see below) - for the cable network from the house to the site;
8. Calculation of material and labor intensity of work. Their cost is not needed, it's up to you;
9. Schedule for the production of work by stages. Start / end dates can be specified relative, eg. "Within a day upon delivery by the distributor to the object"; "Immediately upon completion of item NN." The main thing is that all work is completed during the warm season. At an average daily temperature below +12, new cables are pulled only in exceptional cases with a special permit. If you know how to draw up network schedules of work, so much the better in all respects.

The sketch of the PPR must be correctly drawn up and reduced to a document subject to approval. There is no single form of PPR due to the same variety of cable laying conditions, there are only recommended samples. Therefore, with a sketch of the PPR, you need to go to the local supervisory authority and find out there how they need to be issued. If you have the skills of engineering graphics such as "handles-legs-cucumber", they will also prompt you where to go for the design, so that it was accepted.

The best way out in this situation is to humanly agree with a supervision specialist about a private consultation. This is not forbidden to them; to some extent, it is even encouraged - technical literacy is spreading among people, and a specialist has honest earnings and accumulates experience. Perhaps (in the outback - most likely), he will undertake to bring your PPR to mind. And he or his immediate superior will approve it. As a result, you will get an "iron" PPR without red tape and cheaper than knocking around firms.

Swarm and collect

The golden rule when laying cables with your own hands - do not lay in pieces and do not muffle! Only a cable splicer of at least 5th grade is capable of making a reliable connector on a power cable! Also, do not try to connect the pieces at the top with terminal blocks in the boxes - supervision will not accept, because it is easier to steal electricity from such connectors.

How to dig a trench is up to you, the track and profiles would be maintained. But before the start of the digging, it is necessary to carefully hammer the pits manually at the intersections until the intersected communications are exposed. A gas hole below 0.5 m from the depth of the cable being laid is clogged in the presence of a representative of the gas industry. They need to be notified of this in advance and, at their request, beat the entire pit under supervision.

In the case when the entry channel into the house is made of HDPE pipes, it is very often more convenient to assemble it at the top (in the light), tighten the cable, and put everything together in a trench. In this case, the L-elbows and the horizontal corrugation are laid out on the ground separately at some intervals. The cable is pulled all the way into the outgoing bend, leaving the "tail" for connection, then into a double-walled corrugation and another bend. After that, the channel is assembled and mounted in a trench.

Note: before starting work with the cable, it must be allowed to warm up / cool down to outside temperature for at least a day. If the cable is purchased in one piece on a drum, the integrity of its sheath is checked during the purchase. To do this, press the pin of the nipple on the free end of the cable. Conscientious manufacturers supply cables under excess air pressure. If the casing is intact, you will hear a hiss of escaping air. PvBbShp, PvBbPg and other cables for difficult conditions on a drum not under pressure - either defective or falsified.

How to tighten cables

For God's sake, do not look on YouTube videos, how the cable is pulled into the channel by the wires! The likelihood of an accident in the coming years from this increases not several times - by orders of magnitude! The cables are tightened with a special stocking, pos. 1 and 2 in Fig. Its almost complete analogue can be quickly made with your own hands from a pair of bent U-shaped soft steel wires with a length of 1.5 m and a diameter of 1.5-2 mm. The eye for broaching is obtained from the bends, and the tails of the wires, so that the homemade stocking does not slip when tightening and so that the channel does not scratch, is attached to the PVC cable with electrical tape.

If an intermediate pull-up of the cable is required, a split intermediate stocking is used, pos. 3. To it, if the cable is pulled into the channel, 2 broaches are needed: working and disconnecting (releasing), for which the fixing pin is pulled out. I mark the releasing broach with something very catchy, so as not to accidentally pull it until the end of the cable tightening.

If the channel is not assembled from pipes with standard broaches, a broach made of elastic steel wire is first introduced into it. For entry into the house and wiring around the site, its diameter, as a rule, is sufficient 2-2.5 mm. In channels with other cables, the cable is tightened with a broach made of a fiberglass rod with a rounded end, but for householders this is not an option, especially since it is much more difficult to work with a rod.

Pulling the cable into the elbows already installed in the trench and made in the old fashioned way is often difficult; there are other short but difficult canals. In this case, you can learn a 2-stage vacuum broach:

• A wad is made from a crumpled PE bag or a ping-pong ball and a fishing line is attached to it.
• The wad is introduced into the canal (it should not touch the walls) and sucked out with a vacuum cleaner from the other end.
• With a fishing line, a steel broach is pulled into the channel.
• Pull the cable through the channel.

"Snake" in the trench

The installation of the entrance to the house in the old-fashioned way begins with the installation of L-bends (drops) in the trench. Their bends are fixed above the bottom of the trench at a level of 10-12 cm with pairs of one-and-a-half bricks, etc. The descents are then securely attached to the wall of the house or post. If the entry into the house is through the basement, the opening with the entry pipes is cemented and those are made in the installation of the cable. break before setting with concrete solution 50% strength, approx. 3 days.

In the meantime, the bottom of the trench is covered with sand or sifted excavated soil (see above) to the level of the lower edges of the mouths of the sinks, and the bedding is carefully tamped. Then a cable is pulled into the lowering, starting from the outgoing bend (on the pole) and at the mouths it is wedged from contact with steel with detachable cuffs or scraps of dense rubber. In the latter case, the mouth is filled with raw rubber or silicone sealant. Also, when pulling the cable, it is necessary to ensure that there is no friction of its sheath on the sharp edges of the steel. To do this, before broaching, either special trays are inserted into the mouths, or, as tightly as possible, trims of plastic pipes, pieces of an irrigation hose, etc.

Then they lay the cable in the trench, but in no case tightly (on the left in the figure), so it is unacceptable. For thermal deformations, an allowance of 2-3% of the total route length must be given. But it is also impossible to let a "mad snake" with frequent bends touching the sides of the trench (in the center), this will only increase the accident rate of the site. The cable is laid in the trench, as shown on the right in the figure, with small smooth bends spaced at least 10 cm from the sides of the trench.If several cables are laid, their bends should be located in one direction with an offset of half the bend length.

With a channel made of HDPE pipes, the hassle is much less, regardless of whether the cable is tightened in advance in the light or by installing the channel in a trench. Here is the only "but": the arrow of the "snake" bends must be increased by the size of the diameter of the lumen of the horizontal pipe.

Fall asleep and protect

After laying the cable in the trench, it is backfilled to the level along the profile and laying pattern. It is not necessary to ram the backfill over the cable; it is enough to "slap" a little so that you can put a solid protection - bricks or concrete. Then they put a solid protection and cover them layer by layer with earth to the level of the signal tape, ramming without any special precautions. After laying the tape, the trench is filled up to the top in the same way. There should not be any extra land left, on the contrary, a bed should form above the trench. Over time, it will settle to ground level. Failure over the track a year later is a sign of its accident rate and the basis for applying sanctions to the owner / operator.

From home to site

The ability to do-it-yourself circuit breakers for cable wiring from the house around the site allows you to:

• Reduce the cross-section of the current-carrying conductors to the minimum allowable.
• Apply unarmoured wire.
• Reduce the volume and labor intensity of earthworks by narrowing the trenches and possibly using earthmoving equipment, see above.

All this significantly reduces the cost of the external wiring of the household, without at all reducing its safety and reliability, provided that it is divided into branches and equipped with protective automatics. It is also necessary that the house be equipped with a protective earth circuit. Typical division of the field wiring into branches:

1. Outdoor lighting, burglar alarms and LSS (for example, a water supply pump - 16 A machine;
2. Garage and outbuildings - automatic machine for 32 A;
3. Garden lighting, gazebo / resting area, fountain pumps, pond pumps, etc. - machine for 16 A.

In addition, all external circuits must be equipped with a general residual current device (RCD) of reduced sensitivity, for a current imbalance of 100 mA, see the diagram in Fig. Moreover, it is better to install not a high-speed electronic RCD, but a "stupid" slow electromechanical difavtomat. On the washing machine and the bathroom, you need to put an RCD more sensitive and faster, but this is another matter.

A network of long cables has a rather high intrinsic capacitance and electrical asymmetry of capacitive leakage when switched on. That is, with a too fast and sensitive RCD, a situation is possible when the external circuits simply cannot be turned on - he clicked the automatic switch on, the RCD slams and turns off. Also, the RCD should be with built-in thermal protection in order to cut off the outside, suddenly some circuit closes and gives an active leak. She is dangerous to life, and the counter starts spinning like crazy.

What if an accident?

There is no absolutely reliable technology, and there are no absolutely trouble-free cables either. An unplugged cable can retain its own capacitance and a dangerous voltage can be applied to the cable. Therefore, it is by no means possible to start emergency recovery work (ATS) immediately after the emergency section is turned off. By the way, if there is an accident at the entrance to the house, then an employee of the operator of the power grid must turn it off in the ASU on the pole; you will not get into the TP anyway. Suddenly there is a visible failure of the power cable or suspicion of it, you need to act on the trail. way:

1. Disconnect the emergency circuit breaker and hang the “Do not switch on!” Sign on its lever. People work! ”;
2. After at least 20 minutes, check the presence of voltage on the conductors with a tester or phase indicator (checked at the outgoing end);
3. If there is no voltage, remove the disconnected conductors / conductor from the terminal block of the machine and reliably connect to the bus / terminal block of protective grounding, or put a temporary grounding terminal on the bare parts of the conductors;

The cost of laying a cable in Moscow and the Moscow region depends on the type of installation, the amount of work and the complexity of the task. The company "Electricians-MSK" offers a full range of services for laying power cables and wiring. The use of modern technologies and equipment, as well as the high qualifications of our employees allow us to establish an acceptable cost of cable laying and guarantee an impeccable quality of performance of the assigned tasks.

The cost of laying a power cable and types of work

The cost of installing power cables directly depends on the chosen installation method. Employees of the company "Electricians-MSK", who have admission groups for all types of work, perform:

• Outdoor cable laying, the cost of which is significantly lower compared to the cost of hidden installation. In this case, the wire is attached with staples and clips.
• Concealed installation. The laying of the cable, the price of which is indicated in our price list, involves the chasing of the walls and the laying of the cable in hot-smoked partitions. The wire will be hidden from prying eyes, out of the reach of children and pets.
• Laying the cable in the cable duct. The best option for an office, a shopping center, a summer cottage: the cable is placed in a special box, and the owner of the premises can easily add an additional wire to the cable channel or repair the wiring.
• Trench installation of the power cable (a specific method of underground laying of the power cable is described in the project).
• Installation of overhead lines using porcelain insulators and guy wires.
• Laying of low-current cables (telephone, TV, alarm wires, etc.).

Price list for cable installation:

Installation of electrical cables is carried out in strict accordance with the requirements of the Rules for the installation of electrical installations by qualified specialists. A long-term guarantee is provided for all types of work. If necessary, our employees will assist in the process of preparing project documentation and obtaining the necessary permits, as well as help to purchase all the necessary equipment and consumables.

The power supply of any room or separate electrical installation begins with an input or power wire. There is no strict definition in the Electrical Installation Rules, the document only regulates the testing and installation of the power cable. In principle, any conductor that connects the supply substation to the input device can be attributed to this type of wiring.

The same category includes wires coming from the input device to distribution boards or cabinets. That is, the cable at the entrance to the entrance machine of your apartment, and the wire connecting the machine to your metering device (electricity meter), belongs to the power cable. If the meter is installed outside the switchboard, it is also connected to the circuit breakers using a power cable.

How to choose the right power wire

Overhead networks that supply power using electrical supports are not of interest to us. The most that you will have to face is the supply wire from the nearest pole to your private house.

Important! Do not confuse the diameter and cross section of the conductor. A section is an area!

This parameter is not a dogma. For example, the same 4 mm² wire is designed for a continuous load of 38 amperes. With a single-phase connection of 220 volts, this is already more than 8 kW of load. By setting the input protection to 32 amperes (with the appropriate specifications), you are getting closer to the maximum wiring possibilities. It makes sense to apply a cross-section of the power cable - 6 mm².

The figures considered refer specifically to the power wire. Subscriber wiring to sockets and lighting devices is made with a living area of ​​1.5 mm². An exception is the power group of outlets for a boiler, an electric oven, a washing machine. By the way, such wiring can also be attributed to power, but not by purpose, but by load.

A separate topic is color coding. The electrical installation rule prescribes the use of the following colors:

1. Working zero - blue color along the entire length of the conductor.
2. Protective earth - yellow-green insulation, colors are located along the wire.
3. Phase - there are no color coding requirements for single-phase connection.

Let's consider the third point in more detail. With a three-phase connection, each phase has its own color. This is important, because mixing up the phases means destroying the electrical installation. Therefore, PUE prescribe the following designations:

• A. phase "yellow"
• B. phase "green"
• C. phase "red"

For a single-phase connection (after a three-phase input), it does not matter between which phase and zero 220 volts are formed.

For reference: the European color marking of the phases differs from the requirements of the PUE.

In the vast majority of cases, you will have to install a single-phase power cable. Therefore, the complex marking of three-phase bushings should not confuse you.

Correct power cable routing

If the cable is laid separately from the power plant (switchgear) to the consumer input, only mechanical requirements must be met.

Along walls or supporting structures, wiring is secured with mounting clips. If the strength of the attachment points is in doubt, you can run the power cable along a guide: a bandage steel strip or a supporting cable.

Air routing (the cable hangs freely from one attachment point to another) requires either a strong supporting sheath or a suspension system. The most commonly used steel cable.

If the wire is self-supporting, special tension clamps are used. The cable at the point of approach to the wall or other structure is fixed in the fixture, and its free end is directed to the point of entry.

Power cable routing in trays is widespread. No fixtures are required, the wire is placed in a box and closed with a lid. There are only a few restrictions. Joint laying of power and low-current cables is regulated. Electrical Installation Rules. There are no hard prohibitions, with the exception of redundant power lines. They are laid separately.

The fact is that power cables (if they are not in steel armor connected to a protective earth) generate sufficiently strong interference. It is difficult to neutralize them using filters: when the load changes, the nature of the interference also changes. And the power cable is rarely under stable load.

Therefore, power, signal (communications, computer networks, television), and control lines must be separated. At least, on different sides of the box, and preferably in separate trays.

Regardless of the method of installation, the entry of the outdoor cable into the room is carried out using a curved pipe that prevents moisture from entering the room. The cable must enter it from the bottom up, otherwise moisture can get through the sheath into the inlet shield.

Splicing Power Wiring

Connecting power cables is not just about safety. Although a broken live wire will bring enough trouble. Poor splice can cause arcing under load, progressive increase in resistance, and rapid heating. Despite the non-flammable insulation, it can cause a fire.

In addition, poor contact at the splice leads to a loss of power in the cable, and the amperage may decrease.

It would seem, why use pieces of wire if you can stretch an unbroken chain. However, in reality, breaks occur (it is necessary to make an emergency splicing), and the cable may not be enough corny. So the question is: "How to connect the power cable?" worries many.

There are some simple rules:

Related Videos

Page 12 of 18

In the ground

In the ground - a trench 1-20 kV power cables are laid at a depth of 0.7 m, and 35 kV - 1 m from the leveling mark of the earth's surface and are placed closer to buildings in the sidewalk area. The shallow occurrence of power cable lines laid in the ground, their accessibility is often the cause of mechanical damage during earthworks. Protection of electrical power cables from mechanical damage is carried out with reinforced concrete slabs for cables of 20-35 kV along the entire length, and for cables up to 10 kV - with bricks or plates, while cables with voltages above 1000 V are protected throughout, and cables up to 1000 V - only in places of frequent excavations.

Rice. 21. Parallel laying of power cables up to 10 kV together with control cables.
1 - power cable up to 10 kV; 2 - control cables; 3 - soft soil or sand; 4 - brick or reinforced concrete slabs.
With parallel laying of cable lines up to 10 kV, the distance between them horizontally in the light, as well as between them and the control cables, is taken to be at least 100 mm (Fig. 21).
When laying cable lines with a voltage higher than 10 kV and up to 35 kV inclusive, the distance between them and other cables must be at least 250 mm. The distances given are the minimum in terms of mutual heating and the possibility of arc damage in case of damage.
The clear distance between power cables and communication cables, as well as between cables operated by various organizations, is set at least 500 mm. If, according to local conditions, the required distances cannot be maintained, then, by agreement between the operating organizations, it is allowed to reduce these distances to 100 mm, and between power cables with a voltage of up to 10 kV and communication cables (except for cables with a circuit sealed by high-frequency telephony systems) up to 250 mm provided that the cables are protected from arc damage. Protection
parallel laid cables from damage by an electric arc during a short circuit in the power cable is carried out by installing fireproof partitions between the cables.
The distance between the cable and the body of the cable line couplings is set to 250 mm. If it is impossible to maintain this distance, it is necessary to take measures to protect the cables closest to the coupling against damage (for example, installing a fireproof partition between the cable and the coupling, deepening the couplings, etc.).
When laying cables along buildings parallel to the construction line, the distance from the foundations of buildings to the nearest cable is set at least 600 mm.
According to the conditions of the minimum number of intersections, power cables laid along buildings are located in the following sequence from the building line: distribution line cable with voltage up to 1000 V, distribution line cable with voltage higher than 1000 V, power cable over 1000 V. This arrangement of the line does not lead to the need to relocate nearby cables lying in the trench.
When laying cables in the area of ​​green spaces, the distance from tree trunks to the nearest cable, according to the conditions for ensuring the safety of green spaces, is taken to be at least 2 m, and from shrubs - at least 1 m.
For a cable line located in parallel with a heat conductor, the clear distance between the cable and the heat conductor must be at least 2 m or the heat conductor is insulated throughout the entire area of ​​proximity to the cable line so that additional heating of the ground by the heat conductor in the place where the cables pass at any time of the year does not exceed 10 ° С for cable lines with voltage up to 10 kV and 5 ° С for 35 kV lines.
When laying cables in parallel with other pipelines, the horizontal distance between the cable and the pipeline is taken to be at least 500 mm, and with oil and gas pipelines at least 1 m.If, according to local conditions, this distance cannot be maintained, it may be reduced to 250 mm. at the same time, cables for protection against mechanical damage are laid in pipes throughout the entire approach area. Parallel laying of cables above pipelines and under pipelines (in the vertical plane) is not allowed.
When laying cables in parallel with railways, they are usually placed outside the road exclusion zone (Fig. 22, a). Laying cables within the exclusion zone (Fig. 22.6) is allowed only by agreement with the organizations of the Ministry of Railways, while the distance A (Fig. 22) between the cable and the nearest rail of the railway with diesel traction is assumed to be at least 3 m, and on electrified roads - at least 10 m.

Rice. 22. Laying cable lines parallel to railways.
a - laying the cable outside the right-of-way; b - laying the cable in the right-of-way; c - laying the cable parallel to the tram tracks; 1 - power cable; 2- railroad rail; 3- cuvette.
In cramped conditions, it is allowed to reduce the indicated distances, while the cables throughout the approach area must be laid in blocks or pipes. When laying a cable through electrified railways, insulating blocks or pipes (asbestos-cement pipes impregnated with tar or bitumen) are used.
When laying cables in parallel with tram tracks (Fig. 22, c), the distance from the cable to the nearest rail is set at least 2 m. In cramped conditions, this distance can be reduced, while the cables are laid in insulating blocks or pipes throughout the approach area.
Parallel to the roads of the 1st class (the width of the carriageway is 15 m with four lanes), as well as the II class (the width of the carriageway is 7.5 m with two lanes), cables are laid from the outside of the ditch at a distance of at least
1 m from it (Fig. 23). Reducing this distance is allowed in each individual case in agreement with the relevant road authorities.
If a cable line is laid in parallel with an overhead power line (OHL) with a voltage of 110 kV and above, the distance from the cable to the vertical plane passing through the outermost wire of the line is set at least 10 m.
The clear distance from the cable line to the grounding devices of the supports of overhead power lines with a voltage of more than 1000 V is taken to be at least 10 m.The distance to the supports of the line with a voltage of up to 1000 V should be 1 m, and when laying the cable at the approach section in the pipe, 0.5 m ...
The intersection of streets and areas with, as a rule, improved coverage by cable lines is carried out in blocks or pipes at a depth of at least 1 m. In order to reduce the length of the route, the intersection is performed perpendicular to the structure to be crossed.
When cable lines cross the entrances for vehicles to yards and garages, cables are laid in pipes, and when crossing dead-end industrial roads with low traffic intensity, as a rule, directly in the ground.

Rice. 23. Laying cables in parallel with highways.
1 - power cables, 2 - curb, 3 - ditch, 4 - carriageway of the road bed.
When cable lines cross railways and highways, cables are laid in tunnels, blocks or pipes along the entire width of the exclusion zone at a depth of at least 1 m from the road bed and at least 0.5 m from the bottom of drainage ditches. In the absence of an exclusion zone, the specified method of laying is carried out only at the intersection section plus 2 m on both sides of the roadbed.
At the intersection of electrified and DC electrified railways, cables are laid in insulating blocks or pipes. In this case, the crossing point is set at a distance of less than 10 m from the switches, crosses and points of connection of the suction cables to the rails.
In the case of the transition of the cable line to the air outlet of the cable to the surface, it is carried out no closer than 3.5 m from the foot of the embankment or from the edge of the canvas.
New cable lines laid in the ground usually intersect with existing previously laid lines, as well as with other underground structures. In places of such intersections, cables are protected from mechanical damage and the action of an electric arc in the event of its occurrence.
When power cable lines cross each other, high voltage cables are laid under low voltage cables,
At the intersection, the cables are separated by a layer of soil with a thickness of at least 500 mm (Fig. 24). If, according to local conditions, it is not possible to maintain this distance, then it is allowed to reduce it to 250 mm, provided that the cables are separated at the entire intersection plus 1 m in each direction with fireproof partitions-plates or pipe sections.
When cable lines cross pipelines, including oil and gas pipelines, the distance between the cable and the pipeline is taken to be at least 0.5 m.It is allowed to reduce this distance to 0.25 m, provided that the cable is laid at the intersection plus 2 m in each direction in the pipes.
When cable lines cross heat pipelines, the distance between the cables and the overlap of the heat pipe in the light must be at least 0.5 m; at the same time, the heat pipe at the intersection plus 2 m in each direction from the extreme cables is provided with such thermal insulation so that the ground temperature does not rise by more than 10 ° C in relation to the highest summer temperature and by 15 ° C in relation to the lowest winter temperature (Fig. 25). In the event of crossing the steam pipeline, the channel is completely filled with mineral wool at the intersection points and plus 2 m on both sides of the extreme cables. This measure is carried out in addition to the basic thermal insulation applied to the steam line. In the case when the above temperatures cannot be observed, the following are allowed: cable penetration up to 0.6 m instead of 0.7 m; the use of a cable insert of a larger cross-section; cables are laid under the heat pipe in pipes at a distance of at least 0.5 m from it.


Rice. 24. Mutual intersection of power cables.
a - with separation by a layer of earth; b - with their separation with bricks or reinforced concrete slabs; c - with the conclusion of one group of crossed cables into the pipe; 1 - high voltage cable; 2 - low voltage cable or low current cable; 3 - soil; 4 - brick or slab; 5 -pipe.
In the cramped conditions of the city, it is not always possible to deliver a drum with a cable to the place of its installation for rolling. Usually drums with a cable (they are preliminarily brought to the track, and left temporarily in the nearest yards and other places where they do not interfere with the movement of vehicles, pedestrians, and only by the time the cable is laid are rolled up to the trench and installed for unwinding. the sheathing in the direction of cable winding, indicated on the drums by an arrow, so that the coils of the cable tightly wound on the drum do not loosen and unravel when the drum is rolling. from boards laid along the rolling line, and provided that the cable is tightly wound on the drum, the upper end of the cable is securely fastened and the edges of the drum cheeks rise above the cable turns by at least 100 mm. the drum has not been hit by stones, bricks and other objects that can damage the cab. spruce.

Rice. 25. Cables crossing heat pipelines.
a - cables above the heat pipe; b - cables under the heat pipe; 1 - power cable; 2 - heat pipe; 3 - pipe; 4- thermal insulation.
The drum is installed in such a way that its rotation when winding the cable occurs against the direction of the arrow on the drum cheek. Then a steel shaft with a diameter of 60 mm is threaded through the axial hole of the drum with a drum mass of up to 2500; kg, a shaft with a diameter of 70 mm with a mass of up to 3500 kg and 75 mm with a drum mass of up to 5000 kg. Screw jacks are installed under the ends of the steel shaft, with the help of which the drum is raised 150-200 mm from the ground surface. The raised drum should stand firmly on the supports and rotate freely without moving along the shaft. Carefully, so as not to damage the upper turns of the cable, remove the casing. The nails remaining on the end face of the drum cheeks are removed or hammered so as to exclude the possibility of snagging, damage to the cable when the drum rotates, as well as the hands of workers rotating the drum.
For rolling out a cable from a drum weighing up to 3 tons, it is recommended to use a drum lifter (Fig. 26), the use of which speeds up the installation of the drum.


Rice. 26. Drum lifter.
1 - cable drum; 2 - drum lifter lever.
This design of the drum lifter compares favorably with the jacks discussed above in that it does not require drum outboarding, adjustment of each of the two supports of the installation. The drum lifter is brought under the steel axle threaded through the drum, leveled and, using it as a lever, raise the drum and give it the position and direction necessary for rolling the cable.
Before laying the cable, pre-fix, sprinkle with earth the pipes laid at the intersection or convergence with other underground utilities; prepare passages for entering (the cable to be laid into buildings through foundations and walls; remove from the trench © ode (if any), stones and level the bottom of the trench; fill 100 mm thick at the bottom of the trench with fine soft earth or rock sand and harvest along the route fine sifted earth or mountain sand for powdering the cable after laying, prepare and stack bricks or reinforced concrete slabs along the route to protect the cable after laying and powdering it.
The preparation of the trench for laying the cable is drawn up with an acceptance certificate for installation.
Cable laying work consists of the following technological operations, rolling the cable from the drum, laying the cable in a trench, removing the executive drawing, filling the cable with a layer of soft earth or sand with a thickness of at least 100 mm, laying coatings that protect the cable from mechanical damage, filling the trench.
When winding the cable from the drum by any of the methods described below, measures are taken to exclude the possibility of damage to the cable as a result of sticking tightly superimposed turns of the cable. When gluing adjacent turns and rapid rotation of the drum during unwinding, unacceptable bends and damage to the cable winding from the drum are possible. Therefore, the cable should be unwound at a minimum speed, and to regulate the drum rotation speed, it is braked if necessary. Experienced workers or electricians, standing at the drum, observe the correct winding of the cable, the timely tearing of adhered adjacent turns from each other. A worker standing at the drum picks up a coil of cable coming off the drum and, if glued to adjacent coils, forcefully tears it off from them. A break and damage to the cable when unwinding from the drum can also be due to the falling of the turns as a result of improper winding (usually when rewinding) or rolling the drum with incomplete use of its capacity for a considerable distance and violation of the rolling direction (against the direction indicated by the arrow).
In this case, the turn coming off the drum may be pinched by adjacent turns that have moved out of place. A worker standing at the drum must notice this in a timely manner, remove the jam, release the clamped coil, or temporarily stop the unwinding.
Cable rolling can also be performed from a moving vehicle, by pulling a drive or manual winch on rollers, manually pulling on rollers or manually without rollers.
When rolling out a cable from a drum installed on a transport moving at a speed of 0.6-1 km / h, the cable is laid in a trench at the same time. In this case, a vehicle can be a car equipped with a loader RKB-Z, a trolley of a cable conveyor TKB-5, towed by a car or a tractor, a special cable machine, as well as a car with cable jacks installed on it.


Rice. 27. Cable rolling on rollers using a winch.
1 - cable layer; 2 - roller; 3 - electric winch.

While rolling the cable from a conveyor or a car, rotation of the drum in accordance with the above should be done manually by experienced workers or fitters. Workers following the machine take the coiled cable and lay it on the bottom of the trench. The distance between the edge of the trench and the machine should be at least the depth of the trench for all soils except loam, where this distance is equal to the depth of the trench multiplied by 1.25. The method of unwinding and laying a cable from a moving vehicle is used in the field and in places where there are no other underground structures crossing the trench, and under which the unwound cable must be laid. The use of this method is also possible in the absence of obstacles to traffic along the route. In the cramped conditions of the city with its saturation with underground utilities, it is impossible to use the method of unwinding and laying cables from a moving vehicle. The disadvantages of this method are also the difficulties associated with loading the drum, installing the structure, jacks in the car body, and irrational use of the car.
The most widely used method of cable rolling by pulling it with a cable using a drive or manual winch on rollers. With this method, a drum with a cable is installed on a TKB-5 conveyor trolley or on conventional cable screw jacks at one end of the trench, and winches with a cable for pulling the cable at the other end of it.
Rollers for cable rolling on straight sections of the route are installed at the bottom of the trench at a distance of 3 to 5 m from each other, and corner rollers or a guide chute are installed at the turns of the route (Fig. 27). Fix the corner rollers or guide chute with braces so that they do not move when the cable is pulled.

Rice. 28. Clamp for attaching the cable to the cable.
1 - conical sprocket with three sector grooves; 2 - case; 3 - head; 4 - traction cable; 5 - casing; 6 - cable core; 7 - cable.
When laying several cables in one trench, the rollers are installed so that they do not interfere with the laying of the laid cable in its place at the bottom of the trench. The bend radius of the corner rollers and guide channels must not be less than the bend radius of the cable. After installing the drum with the cable, ensuring its free rotation along the rollers installed in advance, the steel cable of the winch is unwound, the end of which is passed through all intersections, and attached to the upper end of the cable unwound from the drum. At the ends of the pipes through which the cable is pulled (along the rolling process), detachable mounting funnels are installed to reduce friction when the cable enters the pipe channel.
The method of connecting the cable with the outer end of the cable is determined by the tensile force and, depending on the value of this force, the connection can be performed using a special wire stocking, a canvas belt, as well as directly by the conductors using a special clamp (Fig. 28). The permissible length of the pulled cable, at which it is possible to use a wire stocking or a canvas belt, depends on the weight and cross-section of the cable and is limited to a length of no more than 100 m for cable ends with a cross-section of 120-185 mm 2. The wire stocking is put on the cable sheath and is firmly fixed at the end with a wire bandage over the applied resin tape over a length of at least 500 mm.

Table 4
Estimated tensile forces per 100 m of cable

Note. The numerator shows the tensile forces for three-core cables with aluminum conductors, and the denominator - for cables with copper conductors.
The required pulling force on straight sections of the route depends on the mass of the cable (taken according to the data of the handbook for electrical cables) and the coefficient of friction, i.e.
P = kq,
where P is the cable pulling force; q is the mass of the cable; k - coefficient of friction,
The value of the coefficient of friction when unwinding and pulling the cable is: 0.8 when pulling “along the ground (the bottom of the trench); 0.25 when pulling on rollers, when sliding on the ground is excluded, since the number of rollers is installed in a sufficient number; 0.35 when pulling along the rollers, when sliding on the ground between the rollers is not excluded; 0.03-0.04-on ice.
Pulling forces per 100 m of cable for approximate calculations when laying heavy three-core armored cables with voltage up to 10 kV in a trench with a coefficient of 0.35 according to [L. 6] are given in table. 4.
The tensile strength of copper conductors is 26 kgf / mm, and aluminum multi-wire, respectively, 16 kgf / mm. The maximum permissible tensile force is taken equal to 7b of the strength of the cable cores.
The diameter of the steel cable, taking into account the tensile force for laying the cable, is selected according to the following data:

Let, for example, it is required to determine the tensile force of the construction length of 250 m of a cable with a cross section of 3X185 mm 2, voltage of 10 kV, of the ASB brand, laid on rollers.
Using the formula above, substituting the values ​​of the quantities, we get:

where 7763 kg is the mass of 1 km of cable length of the ASB brand with a cross-section of 185 mm 2 and a voltage of 10 kW; 0.35 - the value of the coefficient of friction in the presence of sliding of the cable on the ground between the rollers.
To take into account the additional effort required when starting off (starting movement),

The obtained value of the pulling force allows the choice of the cable diameter equal to 7.7 mm, as well as the lifting capacity of the winch.
The tensile strength of three-core cables with aluminum conductors will be:
185-3-16 = 8880 kgf.
The maximum permissible tensile force for the conductors for this cable is, respectively, equal to: P = 8880/6 = 1480 kgf, which, as can be seen, significantly exceeds the required tensile force P required for rolling out the cable we have adopted on rollers.
The choice of lifting capacity and winch drive for cable rolling, depending on the pulling forces and laying conditions, is made according to table. 3.
After attaching the cable to the upper end of the cable, they begin to roll the drum. Turning on the winch drive motor or rotating the winch manually, they provide the necessary pulling force for winding the cable from the drum, rolling it out to the rollers and the bottom of the trench. When rolling out a cable using mechanisms, the tension force acting on the cable is monitored using a dynamometer or other control device. With a manual drive, the winch is rotated smoothly, without jerking. The cable, which is unwound from the drum by pulling on the cable, must, without bends, freely sliding along the rollers, cross without entanglement and friction other underground structures located on its way higher along the marks.
If it is necessary to pull the cable through the pipes, along with the installation of installation funnels, measures are taken for preliminary cleaning, and, if possible, measures for blowing them. With a pipe length of more than 10 m, the cable being pulled is lubricated with grease.
When rolling out a cable using a cable and pulling winches, two experienced fitters should be at the drum and watch it unwind. If necessary, they slow down the drum or release a coil of cable that is stuck together or pinched by adjacent turns, coming off the drum. The winch with a drive (electric or auto-motor) has one worker who monitors the operation of the winch and controls the pulling force according to the dynamometer. If the cable is rolled out using a hand winch, then two workers are required to rotate it and control the pulling force. An experienced worker is assigned to monitor the end of the cable to be laid moving along the rollers, to direct it under the underground structures crossing the trench, as well as to communicate with the control of the winch and give a signal to stop or start the winch. The cable is rolled out at a speed of 0.6-1 km / h.
After the cable is rolled out, the winch stops, the cable is disconnected, and then the cable is removed from the rollers and transferred to its place at the bottom of the trench. The cable is laid along its entire length with normal slack, a snake, which compensates for changes in the cable length caused by temperature fluctuations in the cable during operation; in this case, the cable length will be approximately 2-3% longer than the trench length. When laying several cables in a trench, their ends are positioned so that the distance between the centers of the couplings (to be installed) is at least 2 m.
The above-described method of mechanized unwinding and cable laying is the simplest, most reliable and therefore has great advantages over other methods, especially on straight routes and in the presence of intersections, under which the cable unwinding from the reel must be laid.
If it is impossible for local conditions to apply rolling mechanisms and cable laying is done manually. When rolling and laying the cable manually, the drum is also installed at the end of the trench, and the cable is pulled by workers placed along the route, at the command of the work manufacturer. The number of workers with manual laying is determined based on the load on each worker, no more than 35 kg. When rolling out and laying the cable, make sure that the cable is not damaged as a result of unacceptable bends, twists, and for this at all critical places: at the drum, at the turn of the route, cable passage through pipes, at intersections with other underground structures - experienced workers or electricians should be posted. For a drum with a cable, it is necessary to have a brake in the form of a board, if necessary, pressed against the drum cheek, and experienced electricians should be supplied to control the drum rotation speed and monitor the correct cable winding. When laying the cable, they ensure the consistency and simultaneity of the actions of all workers along the entire front of work, for which it is recommended, for large gaskets, to have local radio installations on the route and carry out the command using a loudspeaker or telephone. The signal is also sent by flags and other conventional signaling means. The technology of manual cable laying is determined depending on the width of the trench and the presence of intersections with other underground structures in it along a wide trench (at least 0.5 m), workers carry the cable, moving along the trench, and in a narrow trench, workers carry the cable, moving along the edge of the trench. One of the workers takes hold of the end of the cable, and the people placed at the drum begin to rotate the drum. At certain equal intervals of 3-5 m (depending on the mass of the cable and based on the load of no more than 35 kg), the cable is picked up by workers who carry it in their hands, preventing the cable from dragging along the ground after the entire length of the drum has been rolled out, the end of the cable is laid to the bottom of the trench by the first worker, then successively by the second, third, and so on, until the entire cable is correctly laid at the bottom of the trench and in its place.
If there are intersections of the trench with other underground utilities, under which it is necessary to drag the cable, the workers are placed in the gap between two adjacent rollers on which the cable is laid. The workers, standing in place in a bent position, simultaneously and on command, gradually move the cable to be laid along the rollers, as shown in Fig. 29, a. The above-described method of manually unwinding and laying the cable, when the cable drum is installed at the end of the trench, has a significant disadvantage, since it requires a significant number of workers, especially when laying heavy cables.
If, however, the drum with the cable to be unwound and laid is placed not at the end, but in the middle of the trench, then the required number of workers can be reduced by about 2 times. With this method of rolling and laying the cable with the installation of the drum in the middle of the trench, the cable is unwound from the upper end of the drum and laid first in one side of the trench in the same way and in the same technological sequence, which were mentioned above, and then in the other side of the trench. In this case, the cable is wound not from above, but from the bottom of the drum with a loop brought through the drum (Figure 29.6). In the presence of underground structures, under which the cable to be laid should be laid, unwind the entire cable from the drum in a loop, bring the end of the cable under the first intersection and, standing still, gradually move the cable along rollers along the trench through all other intersections until there is the entire buttonhole is selected. Cable laying using loops can be carried out only in extreme cases by a qualified team of workers with extensive experience in cable laying, since this method is most likely to damage the cable as a result of unacceptable bends, kinks and twists. In the forced application of this method, laying on hinges and bends is placed on the most experienced disciplined workers or electricians.


Rice. 29. Laying the cable without the use of mechanisms (manually).
a - unwinding the cable from the drum and moving the cable along the rollers; b - unwinding the cable from the bottom of the drum with a loop inserted through the drum.
The arrangement of the drums with the cable along the route of the laying and the rolling of the cable is performed using the factory marking of the upper end of the cable, as follows. The construction lengths of the cable are laid sequentially one after the other, and the upper end of one drum is placed against the lower end of the other drum if the marking of the upper end of both drums is the same ("P" or "O"). If the upper end of one drum is marked "P", and the other is "O", then cable rolling from these drums should be performed with their upper ends towards each other.
When laying the cable, a reserve of cable ends along the length is required to complete the connection and termination, the device of compensators that protect the coupling from damage due to soil displacements, as well as temperature deformations of the cable. it was possible to mount a new coupling without the need to lay the insert and install two couplings. For cables up to 10 kV inclusive, the length of the cable stock in the joint joint compensators can be taken equal to 350 mm (which corresponds to half the length of the joint for the largest cable section of 240 mm 2 type CC-110, equal to 690 mm) and for cables 20-35 kV, respectively 400 mm.
The length of the reserve required for cutting and connecting the cable is determined depending on the method of making the connection with conductors of the same name (of the same color) or of unlike conductors (of different colors).
When constructing power cable lines, the connection of individual construction cable lengths to each other is usually performed with any cores without taking into account the colors, and phasing in order to ensure the same name of the phases with the RU busbars is performed during the installation of the termination. The reserve of the cable left by the ib ends (overlapping) during laying, depending on the method of making the connection, is:
when connecting with any cores of different colors

when making a connection with conductors of the same name of the same color

where I is the length of the pitch of the total twisting of the cable (mm), the value of which for power cables of large cross-section is 3000 mm; 3 - the number of phases (cores) involved in calculating the length of the stock at each end; 2- the number of cable ends to be connected.
When laying a cable with single-wire conductors of a large cross-section (150 mm 2 and more), having a rigid structure, it is necessary to replace this cable with a multicore cable of normal flexibility of the same brand at the site of entry of the line under construction into the building, the switchgear cell.
The use of rigid cables with single-wire conductors in the cramped conditions of switchgear of electrical devices is not always possible due to the small dimensions of the cells, leaning boards and assemblies and the difficulties arising in connection with this when installing the termination and performing the connection.
Above, various ways of unwinding and laying a cable were considered, as well as the reasons that cause damage to the cable.
When laying a cable with impregnated paper insulation, the most difficult, irreparable type of defect in work, leading to damage to the cable throughout its entire length, is the unwinding and laying at a negative temperature of the external environment of a previously unheated cable.
At negative temperatures below 0 ° C, the oil-rosin composition, which is impregnated with the paper cable insulation, loses its viscosity and lubricity. At the same time, the solidified mass does not lubricate, but glues the layers of paper insulation tapes. The bending of the cable during unwinding and laying under these conditions leads to rupture of paper insulation, a decrease in its electrical strength and subsequent electrical breakdown after the cable line is put into operation. Therefore, laying cables with impregnated paper insulation at temperatures below 0 ° C without preliminary heating is not allowed. The cable can be heated in a heated room, in a special heating house and by electric current. The most convenient, high-quality and fastest is the method of heating the cable with electric current.
This method consists in the fact that an electric current is passed through the conductive cores of the heated cable, the source of which is a power transformer with a power of 20 kV * A, a voltage of the primary winding of 220/380 V, and of the secondary winding from 7 to 98 V at 10 steps. The transformer is fixed in an annular frame, which makes it easy to transport. The value of the electric current passing through the conductors of the cable is set depending on the cross-section and voltage of the heated cable. The only drawback of this method is the need to break the sealing of the ends of the cable, since to create an electric current circuit, it is necessary to short-circuit the conductive cores of the inner end of the cable after they are cut, and connect the outer end to a current source - a power transformer.
After connecting the cable cores to each other, it is necessary to restore the sealing of the inner end of the cable by soldering a lead cap. The lead cap must be soldered in such a way that the short-circuited conductors do not reach the bottom of the cap by 30-40 mm, since at a shorter distance the cap can be torn by the conductors of the cable during its laying.
The outer end of the cable on the drum is cut under a temporary funnel and poured with a bitumen mass so that the place where the insulation of the conductors is cut is filled with the mass and spaced 50 mm from the surface of the mass poured into the funnel. It should be borne in mind that after warming up the cable and subsequent cooling, a vacuum is formed inside it, as a result of which intense suction of the outside air and humidification of the insulation is possible, if no tightness is created when sealing the ends of the cable. Therefore, after the end of the heating of the cable, the funnel is cut off and a lead cap is also soldered to this end of the cable.
When turning on the cable for heating, make sure that the load does not exceed the maximum permissible value for a given cable cross-section, taken from the tables of permissible loads for air, taking into account the correction factor for the air temperature during heating.
If several cables are laid in the trench, then it is possible to simultaneously warm up several drums from one transformer by connecting their conductive cores in series with each other and increasing the circuit voltage, respectively. If the cables to be heated have different cross-sections of conductors, then the maximum permissible current for heating is chosen over a cable with a smaller cross-section of conductors. When you turn on the cable for warming up using an ammeter, make sure that the current does not exceed the values ​​permissible for a given cable cross-section. Along with monitoring the current value, monitoring the temperature of the outer covers of the upper turns of the cable on the drum is established.
The temperature of the armor or metal sheath of the outer turns of the cable at the end of the warm-up should not exceed + 25 ° С for cables 20-35 kV, + 35 ° С for cables 6-10 kV and + 40 ° С for cables 3 kV and below. To monitor the heating temperature between the two upper turns of the cable, a thermometer is installed on the drum, the lower end of which is tightly pressed against the outer cover and insulated with felt or cotton wool. The cable is laid after the end of heating at the maximum possible speed (from 30 to 60 minutes, depending on the outside air temperature) so that the cable does not have time to cool down. In cases where the laying of the cable, carried out at a low temperature, for some reason is delayed and takes a long time, the cable is reheated before the start of unwinding, or the cable is laid "under current".
A heated cable should be laid in a trench like a snake, have a greater slack (3%) than a similar cable laid under normal conditions (that is, without heating), since it will stretch a little when it cools.
After the cable is laid, the correct placement of the cable in the trench, in the pipe provided for the intersection of passages, streets, as well as on the approaches and inputs to the switchgear of substations, compliance with the dimensions at the points of convergence and intersection of cable lines with each other, as well as with underground structures located in operation of other organizations.
To draw up executive drawings, they survey the route of laying and entering cables into the electrical room before backfilling the trench. In accordance with the requirements [L. 4] for topographic and geodetic works, executive drawings of the cable laying are signed by the surveyor who surveyed the route, representatives of the customer and the construction and installation organization. The correctness of the survey and the compliance of the executive drawing with nature after the control measurements and inspection are certified by the technical supervision. The as-built drawing of the route is included in the as-built documentation presented when the line is put into operation.
As a project for the construction of a cable line, as-built drawings for cable laying are made at a scale of 1: 500, and in some cases, where there is a large number of cable lines, at a scale of 1: 200 or even 1: 100. The location of each laid cable line is "tied" to permanent structures, which are usually buildings, and in areas where there are no permanent landmarks, reinforced concrete or metal poles (benchmarks) are installed at the rate of 100-150 m from each other on straight sections of the route, at all bends and at couplings.
The executive drawings also indicate the sections of the route where the cables are laid at a depth of more than 1 m and less than 0.7 m, the location of occupied and reserve pipes laid in connection with the convergence, intersections of other underground utilities.
After checking the quality of the laying, filling the cable with a layer of soft earth or sand 100 mm thick, laying slabs or red (non-silicate) bricks to protect the laid cable from mechanical damage, an act for hidden work is drawn up, drawn up by the construction and installation organization and the representative of the operating organization. The representative of the technical supervision gives permission to backfill the trench, while controlling the quality of the backfill, the thoroughness of the soil compaction over the laid cables.
Before covering the cable with a layer of earth or sand, laying protective plates or bricks, it is not allowed to leave the cable unattended due to interruption of work. The brick is laid on top of the cable backfill so that with one cable the middle of the coating is on the axis of the cable (in one layer across), and with a large number of cables, a continuous flooring is made from the coating with an exit in both directions beyond the outer cables of at least 50 mm.
Backfilling of the trench, as a rule, is carried out with soil previously removed from the trench, provided that it does not contain lumps of frozen soil, stones, construction waste, slag, etc. earth. On improved streets, city squares and in other areas with an improved road base, trenches and pits are covered with exclusively sandy soil in order to avoid subsequent subsidence after the restoration of the road surface. The final filling of the trench with soil and its compaction is carried out by mechanisms.

Ready to order?

Enter your phone number, comment, and our specialist will contact you!

EcoTechnologyGroup is laying power cables. The work uses modern technologies and equipment. All activities are carried out quickly, taking into account the characteristics of the landscape and ensuring the protection of communications from mechanical and temperature influences.

Experts carry out the installation of power wires of various types, classified according to a number of criteria:

• core material;
• rated voltage;
• design features;
• operating temperature range, etc.

Cable routing methods

• On trays. This installation technology provides an aesthetic appearance of the network, protection from aggressive environments and moisture. The choice of the tray is carried out taking into account the weight and cross-section of communications.
• In the trench. The channel is being prepared for laying the network in the ground. Next, backfill is made from below and backfill from above. 6 wires are allowed in the trench.
• In the pipes. They protect networks from damage. The technology is used to organize cable routes in places with unfavorable conditions (on aggressive soils, uneven surfaces, etc.).
• On overpasses. The structures are used for the installation of communications in permafrost conditions, in an aggressive environment.
• In special channels... They are made of brick or reinforced concrete and reliably protect the wiring from mechanical damage.
• In sewer structures... This method provides protection against mechanical stress, soil movement, electromechanical corrosion, temperature fluctuations.

We carry out installation work in Moscow and the Moscow region:

Prices for cable laying

Stages of cable laying

1. Preparation of structures for laying the cable route.
2. Rolling and wiring installation.
3. Connection of cores and installation of couplings.
4. Protection of the network from various damages and termination of communications.
5. Backfilling of trenches, closing of trays and channels.
6. Testing.