Proverbs and sayings about May HORIZONTALLY: 2. May will deceive - in ... will leave.4 ....
1. How to choose the right cable for fire alarm?
As you know, any device works efficiently and reliably only when it is working properly. This also applies to fire alarm cables. The condition of the cable itself determines both the period of its operation and the safety of people in the room where the fire alarm system is installed.
2. The main characteristics of the cable for signaling.
Until recently, the signaling cable looked no different from a regular telephone cable. But today the requirements are tougher. Changes have been made to the component and section. A prerequisite is the non-flammability of the cable with an open fire, a blazing flame.
Signaling cables are classified according to the type of current-carrying core: single-core and multi-core, flexible cables. Flexible multicore cable- products where several conductors act as a current conductor, which are intertwined with each other. Single-core products include products in which current flows through a solid conductor. The thickness of their section is proportional to the strength of the current for which it is designed.
Each type of cable has its own advantages and disadvantages. According to the new rules fire safety the wire must have the abbreviation "NG" on the coating, which means that it will not cause the spread of fire in a fire. Unfortunately, in modern industry it is difficult to find a material that would not ignite in a strong flame, however, a cable marked "NG" minimizes the consequences of ignition.
The abbreviation "LS" means that it emits a negligible amount of smoke. The abbreviation "HS" means that the cable contains no halogen. The use of the OPS cable violates the new fire safety requirements adopted in 2016.
3. How to choose the right cable for alarm installation?
In GOSTs and fire safety standards, it is written what equipment should be for an alarm system in public, educational, health and other institutions. Guided by these standards, you can choose a wire for signaling and for residential premises, as well as competently install the entire system. As they say, it is almost impossible to check the quality of the cable “in practice”. For these purposes, there are specialized laboratories. Under normal conditions, at most, you can set fire to a piece of cable and see how the fire spreads. If this is a quality product, then you will not feel bad smell, the smoke will not be black, and the cable winding itself will die out quickly.
4. How to properly install a fire protection system?
Pledge quality installation system is its installation in accordance with the norms and state standards. It is important to remember: - you can not increase the length of the cable within the range of one loop, - the wires after installation should not sag (for all types), - the cable with armored parts and protection is installed only in rooms where there is a high risk of fire, - a cable with copper windings can be use for installation, - after heat treatment, the wire loses about 10% of the length, - the minimum diameter is 0.5 mm., And the maximum value is determined from the table, taking into account the data on the reduction of voltage in the network, power surges.
The cable needs to be protected from weather conditions outside the building, on the street. It is best to let him underground or under a canopy, this will protect him from negative impact and extend the service life.
5. Be careful
On many sites you can find a manual for installing a fire alarm with your own hands, but this is absolutely impossible to do: - firstly, you have no knowledge and experience, - secondly, you risk your health or even life.
Without special knowledge, installing an alarm system can end tragically. System installation fire safety it is better to entrust the experts. At the same time, use only a factory-made system, since it meets all the standards and requirements, has passed all the necessary checks and will be able to work adequately in a critical situation, which cannot be said about a home-made system. When buying components and cables that do not meet the standards, you act at your own risk and fear: no one will guarantee the high-quality and reliable operation of such a system. Remember that without basic knowledge, only on the basis of the article you read, you will not be able to assemble a working fire safety alarm. To avoid undesirable consequences, it is better to contact competent people.
To date, the role of fire alarms is appreciated. More recently, it was installed only in special rooms where flammable substances are stored or produced.
Now, offices, residential apartments and even private houses are equipped with such a system. For the safety of property and life, a fire alarm can be installed by anyone. Specialists in this field have vast experience in design and installation.
Design and calculation
At the design stage, the number of detectors, control panels, annunciators is calculated, as well as the length cable route. The design is based on the area of the premises and the category of the building. Piece positions, as a rule, are calculated accurately, but the length of the cables is taken with a margin.
According to the norms of material consumption, 10% of the total volume of cable products must be taken into account for unforeseen expenses, such as bypassing architectural elements (columns, pilasters), changing the laying route, at the request of the customer, etc.
Due attention must be paid to the selection of cables, because it is through them that an important alarm signal is transmitted. If you choose low-quality products, then loss of communication is inevitable. The operation of the alarm system is largely determined by the speed of signal transmission from sensors to annunciators.
Per a short time information about a fire must go a long way, notifying special services of the appearance open fire. Cables in this case play the role of "roads". The worse the "road", the slower the signal moves. For the correct operation of the system, the cables must be selected in accordance with the project.
Required characteristics
According to Federal Law No. 123 of July 22, 2008, cables and wires of systems fire protection must remain operational in a fire, thereby ensuring the timely and safe evacuation of people. Based on this, each cable has several important technical characteristics.
The first and, perhaps, the main one is fire resistance - the ability of a cable to transmit a signal when exposed to open fire. Simply put, the system must work even during a fire. The time of complete combustion of the cable should be enough to evacuate people. The fire resistance limit can reach three hours.
The second characteristic is the degree of flammability. Construction Materials subdivided into combustible, slow-burning and non-combustible. To find out which group the cable belongs to, you need to look at its designation. For fire alarms, cables with the designation "NG" are used, which means non-combustible.
The third parameter is toxicity. Quite a specific feature. It is indicated as a percentage and shows the level of toxic substances in the air during the burning of the cable. As a rule, they are laid in children's, educational or medical institutions.
Fire hazard is the fourth of the indicators. The cable line of any system is connected to a current source, so ignition is also possible inside the core itself. This is due to incorrect calculation of the cross-sectional area or poor-quality cable.
Check and test
Cable products are tested in specialized laboratories. At the time of the test, normal voltage is applied to the cable, as well as a flame from a burner (at least 700 ° C). If within 180 minutes there was no failure in the signal transmission over the cable, then the test was passed.
When choosing the type of wiring, it is necessary to take into account the voltage in the network, moisture resistance and cross-sectional area. Cable products must meet the requirements of GOST R 53315-2009.
According to this normative document cable products must have the appropriate passports and certificates, as well as be marked in accordance with the technical specifications.
Cable products are usually divided into categories, according to the execution method:
- special performance. Laying such a cable is possible only after treatment with a flame retardant;
- performance "ng". For group laying in electrical installations of open type;
- version of the "ng-LS" type. For laying in closed electrical installations of industrial and residential buildings;
- version of the "ng-HF" type. Laying in a bundle is possible, in rooms where there will be at the same time a large number of people (concert halls, cinemas, offices);
- version of the "ng-FRLS" type. Such a power cable is laid in strategically important structures. It has the highest degree of fire resistance and explosion protection.
Cable line device
Any of the above cables has a similar design. Inside, there are conductive copper conductors packed in insulation - a special type of silicone rubber, which provides fire resistance and protection against mechanical damage.
Several cores isolated from each other, collected in one bundle, are called twist. The roll is wrapped in an aluminum foil called a screen. Its function is to protect the conductive wires from electromagnetic interference, which can cause false fire alarms.
A copper conductor is laid under the screen so that the fire alarm works without failures, even if the outer layers of the wiring are mechanically damaged. The outermost covering of the cable is called the sheath and is generally made of low fire hazard PVC materials. The cross-sectional area of the cable depends on the number of cores.
Cable installation is divided into single laying and group laying. With group laying, the distance between the cables is not more than 300 mm.
In the modern everyday life of the fire service, such a concept as the survivability of the system has appeared. It means the ability of the system to function during a fire. By international standards the minimum evacuation time is 30 minutes. During this interval, the system must alert the fire and correct the movement of the crowd to avoid panic.
A fire alarm system must not only detect, but also monitor the spread of fire, so cable products should not fail until the fire is completely extinguished.
The wiring is supplied in bays, which indicate the manufacturer, brand, length, and weight of the cable. A label with a seal on passing technical control is attached to the bay. When accepting the cable, it is necessary to pay attention to the tightness of the insulation and sheath.
During the operation of a fire alarm, it is necessary to carry out periodic checks of cable products for fire resistance, signal transmission, as well as mechanical damage to the sheath.
What to pay attention to?
Summing up, it can be noted following parameters when choosing a cable:
- category of the building in which the alarm will be placed. Defined by the project based on normative documentation(GOST, SP);
- manufacturer. Along with domestic manufacturers, imported copies are also represented on the market. They tend to be more expensive;
- cross-sectional area. The higher the voltage in the network, the larger the cross-sectional area should be;
- fire resistance. Must correspond to the purpose and category of the building;
- cable execution. Depends on the specificity of the building and the number of people in it.
To ensure the uninterrupted operation of the fire alarm, the sensors are connected to the warning devices and the dispatcher's console via wires (loop lines). The cables also transmit control messages, optical signal, etc. The types of fire alarm loops are divided according to their structure, the requirements for them are specified in SNiP and Federal Law No. 123.
Requirements for fire alarm wires
All the basic requirements for fire alarm loops are to ensure that the system is operational in the event of a fire for the required time. Ideally, the cable should have the same degree of fire resistance as the room.The terminal device of the loop is provided with constructive additional or any other fire protection.
According to the Federal Law, cable standards are regulated by a decree of 07/10/2012. In particular, it states:
- The resistance of the fire alarm loop must withstand exposure to an open flame for a given amount of time. At the same time, the operability of warning and signaling systems is maintained in full, until employees and visitors leave the building.
- It will help you choose cables corresponding to GOST. The designation of fire alarm loops is regulated in the Federal Law, therefore, the marking of the wire should be in without fail be present on the winding.
- Horizontal and vertical are protected by non-combustible structures and fire protection. The codes for laying fire alarm cables prescribe the use of wire with a heat-resistant winding. Inside the ceiling walls, voids and niches, installation is carried out in a corrugated pipe. When laying open fire alarms, non-flammable wire is used.
- The penetration of cable lines through the walls needs to be processed flame retardants. During work, joints are sealed and others. The method of laying through the walls is determined taking into account the technical characteristics of the building, its flammability. Compulsory laying in boxes is determined by the degree of fire hazard of the room.
- Laying with other cables is allowed, subject to the presence of a thermally insulating winding.
- Fire alarm maintenance should be carried out by a specialist, a representative of a company that installs warning systems.
To determine the location of a fire, it is necessary that all systems are in working order. For fire alarms, a cable resistant to exposed fire. The fire resistance limit is calculated according to the requirements of the PPB for load-bearing structures in room.
Types of loops for fire alarms
The choice of cable section, the maximum length of the substation loop and many other aspects are calculated after choosing the sensor connection scheme. There are several basic ways to accomplish this task:- Threshold systems with stub
. One control device, a monoblock, is able to serve no more than ten lines and sensors. The increase in capabilities is achieved by installing another loop control unit. The name of the system was due to the principle of operation used. Each sensor has its own sensitivity threshold. When it is reached, an alert is triggered.
The disadvantage of the threshold system is a large number of false signals. Laying together with other cables only exacerbates the situation. Another disadvantage is the impossibility exact definition fire places. The system notifies only of a line break, so the entire loop of the radial type has to be checked.
The advantage of the solution is the low cost of equipment and installation work. - Threshold structures with modular loop. Almost no different from the previous scheme. The difference is that the module used can control the operation of many lines at the same time. The loop parameters allow you to duplicate the alert signal by connecting two-threshold structures.
- Addressable analog lines. The system is controlled by the module to which the ring loop is connected. The difference between the addressable analog device is that the sensor itself does not decide on the presence of a fire, but simply transmits necessary information on the remote.
The system with the ring construction of loops allows you to screen out unnecessary information. The signal is duplicated and transmitted to the control panel. The analysis allows you to distinguish fire cases from cable breaks and other loop failures. Transit laying allows the use of cable lengths up to 2000 m. - Combined systems. To output a signal to the dispatcher, both threshold and analog equipment are used. Modern signaling, which takes into account all the shortcomings of the previous lines. The loop troubleshooting algorithm is facilitated by the use of a loop circuit.
Combined systems can be used both indoors and outdoors. In the second case, a shielded outdoor cable is used.
For some categories of premises, the PPB establishes certain restrictions on loops. Installation of exclusively non-flammable wire, inadmissibility concealed wiring, laying in a cable tray - these and other restrictions are described in SNiP 3.05.06-85 and VSN 116-87.
What cable is needed for PS
The brand of wire for installation is determined by the fire hazard category of the building and installed system alerts. The decision to use a thermal cable and other types of materials is made during the development of project documentation. When choosing a cable, the following indicators play an important role:
- Section calculation. insufficient power and throughput can lead to inaccurate sensor readings. In the case of threshold systems, a low-current cable can cause permanent false alarms.
- Sufficient cable protection. In addition to thermal insulation and the presence of a non-combustible winding, it may be necessary to reduce the sensitivity of the loop. In a normal situation, you can immediately use a protected wire. But if, due to oversight or other reasons, the PS fails due to the sensitivity of the cable, the insulation resistance of the loop is measured.
- Marking. The fire resistance limit of cables, the presence of shielding of the loop and other indicators should be indicated on the wire winding. The rules for marking cable lines also require that the coefficient of smoke and flammability be indicated.
- NG - non-combustible - has a classification in terms of fire resistance from A to D.
- LS - laying is recommended in explosive areas, as well as in a group tray. Do not spread harmful fumes during combustion.
- HF - when burning, they do not emit substances with high corrosive properties. Laying in a cable tray together with other signaling wires is allowed.
The norms for laying loops depend on the alarm system used and the current requirements of the FSP. The list of cables acceptable for use is given in SNiP and PUE. Violation of the recommendations leads to a malfunction of the PS.
If the cable does not meet the standards, upon detection of this, the inspector of the Ministry of Emergency Situations will write out an explanatory note and bring to administrative responsibility indicating the timing of the replacement of existing loops.
Methods for laying substation loops
Installation and Maintenance alarm systems are described in VSN 116-87, additional requirements are in SNiP 3.05.06-85. Among all the instructions, the following can be distinguished:
On the this moment There are many requirements for the cable products of the fire alarm system (SPS), the observance of which is prerequisite, since not only the reliability of the entire system, but also its efficiency will depend on this. The main thing to remember is that the weight of the cables of the fire protection system must not support and spread combustion, and must also maintain their integrity in fire conditions all the time while people are being evacuated.
According to the current legislation, the following requirements for fire resistance are put forward for cable products of fire-fighting complex systems:
- in fire conditions, all SPS cable loops for connecting fire detectors must not support and propagate combustion;
- in fire conditions, all cable loops for connecting sirens of the public address system of the 1st and 2nd types must necessarily remain operational all the time while people are being evacuated from the building, but not less than 15 minutes;
- in fire conditions, all cable loops for connecting loudspeakers of the public address system of the 3rd, 4th and 5th types must necessarily remain operational all the time while people are being evacuated from the building, but not less than 30 minutes;
- in fire conditions, all cable loops for powering the fire alarm system and control loops for other systems of the fire-fighting complex must necessarily remain operational all the time while people are being evacuated from the building, but not less than 30 minutes;
- in fire conditions, all cable loops for powering fire extinguishing systems must necessarily remain operational all the time while people are being evacuated from the building, but not less than 30 minutes, and for sprinkler and deluge systems, not less than 60 minutes;
- in fire conditions, all cable loops for powering the smoke removal system must necessarily remain operational all the time while people are being evacuated from the building, but not less than 30 minutes;
- in fire conditions, all cable loops that are designed to control fire elevators must remain operational all the time while people are being evacuated from the building, but not less than 30 minutes;
The choice of SPS cable products and the methods of its laying must comply with generally accepted state requirements, namely: GOST R 53315 and GOST R 53325.
1. information loops of the fire alarm system must be made of copper and not have twists along the entire length;
2. in areas where there is an increased electromagnetic background, optical transmission channels should be used;
3. the sheath of the cable used must not support and propagate combustion, as well as emit toxic gases;
4. the fire resistance of all cable products must not be lower than the time required to complete the task by the connected components of the system;
5. in the event that the SPS does not control any systems of the fire complex (alarm, extinguishing, smoke removal, etc.), it is allowed to use an ordinary telephone cable with copper conductors as loops for connecting fire detectors;
6. when designing the SPS, the cables of signal loops should be selected with a reserve of cores, not less than 10%;
7. connection of SPS loops to control panels(PPK) is recommended to be performed using junction boxes or cross-connects, direct connection is possible when the system has a capacity of no more than 20 radial loops;
8. SPS ring loops must be made with an independent cable, the beginning and end of which are connected to the corresponding terminals of the control panel;
9. the diameter of the copper cores of the wires used for SPS cable loops should be calculated depending on the length of the connection and the load power, but it should not be less than 0.5 mm;
- the power supply lines of the control panel of all systems of the fire-fighting complex, as well as the control lines of these systems, must comply with the above fire resistance requirements and be made with independent cables;
- power supply lines of the control panel of all systems of the fire-fighting complex, as well as control lines for these systems, are not allowed to be laid through fire hazardous premises and explosive zones;
- joint laying of low-current cable lines with voltage up to 60 V with power cables with voltage of 100 V and above is strictly prohibited;
- joint laying of low-voltage and power lines is allowed in different compartments of cable trays, while the fire resistance limit of the tray partition must be at least 25 minutes;
- parallel open laying of low-voltage, power and lighting lines is allowed at a distance of at least 0.5 m from each other (in the case of using screened low-current cables, the distance of their laying can be reduced);
- unshielded low-current cable can be laid at a distance of at least 0.25 m to single power wires;
- in the case when in the room where the fire alarm loops are laid high level electromagnetic radiation, they must be protected from interference;
- when using shielded cable products in SPS, the cable shield must be grounded along the entire length;
- external SPS networks must be laid in a special cable duct, or in the ground, in accordance with the PUE standards for laying cables in the ground;
- air laying of SPS cable products and laying on walls outdoors is not recommended, but is possible subject to all the requirements of state standards;
- SPS power lines (main and backup) must be laid separately, excluding the possibility of their simultaneous failure (their parallel laying along the walls of the premises at a distance of at least 1 m from each other is allowed, or joint laying in the case when one line is laid in a pipe from non-combustible material with a fire resistance limit of at least 75 minutes);
- if it is impossible to visually control the presence of power on fire detectors that are connected to one loop, it is necessary to provide a signal lamp at its end, which will signal a malfunction of the loop;
- in the case when the SPS controls the fire extinguishing system, all communication lines must provide the necessary reliability of data transmission.
When choosing a cable for a fire alarm system, in addition to the above requirements, you need to pay attention to ego marking and specifications. It is important to correctly calculate the following indicators:
- core cross section- an indicator that will affect the quality and range of signal transmission. When choosing a section, you need to know the load of the connected consumer, the signal transmission range and the cable material (mostly copper is used).
- shell protection level- fire resistance, toxicity, armor, screen, etc. The level of protection of the cable will depend on the characteristics of the place of operation and the specific purpose (power cable, signal cable, control cable, etc.).
- marking- a special designation on the cable sheath that indicates the degree of protection, the presence of a screen, toxicity, flammability, etc. For example, the marking "NG" indicates that the cable is non-flammable, "LS" - that it can be used in explosive areas, "HF" - that it does not emit toxic substances during combustion.
In addition to all these indicators and characteristics, do not forget about cable certification. All cables used in the fire alarm system must have a certificate of conformity valid at the time of installation of the system. In case of non-compliance of the cable loop with the current standards, the inspector of the Ministry of Emergency Situations will not allow the facility to be operated and will bring the management to administrative responsibility, which will subsequently lead to material waste to eliminate comments and undergo a new examination.
To avoid unnecessary waste and wasted time, it is better to contact the specialists of the company "", who have great experience in the installation and maintenance of fire fighting complex systems and provide you with a full range of services at affordable prices and with GUARANTEE for the work performed. Turning to us, you will significantly save your time and money.
The choice of the cross section of cables and wires is a mandatory and very important point in the installation and design of any circuit. electrical installation. For right choice cross-section of the power wire, it is necessary to take into account the value of the maximum current consumed by the load. The current values are easy to determine, knowing the nameplate power of consumers according to the formula: I \u003d P / 220.
Knowing the total current of all consumers and taking into account the ratio of the allowable for the wire current load(open wiring) per wire cross section:
- for copper wire 10 amps on the millimeter square,
- for aluminum 8 amps per millimeter square, you can determine whether the wire you have is suitable or if you need to use a different one.
When making hidden power wiring (in a pipe or in a wall), the values given are reduced by multiplying by a correction factor of 0.8.
It should be noted that open power wiring is usually carried out with a wire with a cross section of at least 4 square meters. mm based on sufficient mechanical strength.
The above ratios are easy to remember and provide enough accuracy for using wires. If you want to know with greater accuracy the continuous current load for copper wires and cables, then you can use the tables below.
The following table summarizes the data for power, current and cross-section of cable and wire materials,
for calculations and selection of protective equipment, cable and wiring materials and electrical equipment.
Permissible continuous current for wires and cords
with rubber and PVC insulation with copper conductors
Permissible continuous current for wires with rubber
and PVC insulation with aluminum conductors
Permissible continuous current for wires with copper conductors
with rubber insulation in metal protective sheaths and cables
with copper conductors with rubber insulation in lead, PVC,
Nairite or rubber sheathed, armored and unarmored
Permissible continuous current for cables with aluminum conductors with rubber or plastic insulation
in lead, PVC and rubber sheaths, armored and unarmored
Note. Permissible continuous currents for four-core plastic-insulated cables for voltages up to 1 kV can be selected according to this table as for three-core cables, but with a factor of 0.92.
pivot table
wire cross-sections, current, power and load characteristics
The table shows data based on the PUE, for selecting the cross sections of cable and wire products, as well as the rated and maximum possible currents of circuit breakers, for a single-phase household load most often used in everyday life
The smallest permissible sections of cables and wires of electrical networks in residential buildings
Recommended section power cable depending on power consumption:
- Copper, U = 220 V, single phase, two-core cable
- Copper, U = 380 V, three-phase, three-core cable
Load power depending on the rated current
circuit breaker and cable sections
The smallest sections of the conductive cores of wires and cables in electrical wiring
|
Cross-section of conductors, mm 2 |
||
|
conductors |
aluminum |
|
|
Cords for connecting household electrical receivers |
||
|
Cables for connecting portable and mobile power receivers in industrial installations |
||
|
Twisted two-core wires with stranded conductors for fixed laying on rollers |
||
|
Unprotected insulated wires for fixed indoor wiring: |
||
|
directly on bases, on rollers, clips and cables |
||
|
on trays, in boxes (except deaf ones): |
||
|
single-wire |
||
|
stranded (flexible) |
||
|
on insulators |
||
|
Unprotected insulated wires in outdoor wiring: |
||
|
along walls, structures or supports on insulators; |
||
|
overhead lines |
||
|
under awnings on rollers |
||
|
Unprotected and protected insulated wires and cables in pipes, metal sleeves and blind boxes |
||
|
Cables and protected insulated wires for stationary electrical wiring (without pipes, sleeves and blind boxes): |
||
|
for conductors connected to screw terminals |
||
|
for cores connected by soldering: |
||
|
single-wire |
||
|
stranded (flexible) |
||
|
Protected and unprotected wires and cables laid in closed channels or embedded (in building structures or under plaster) |
||
Cross-sections of conductors and protective measures for electrical safety in electrical installations up to 1000V
Click on image to enlarge.
Selection of the core cross-section for the SOUE cable line
General Comparative characteristics cables for local network
| cable type (10 Mbps = approx. 1 Mb per second) |
Data transfer rate (megabits per second) | Max official segment length, m | Max unofficial segment length, m* | Possibility of repair in case of damage / extension of length | Interference susceptibility | Price |
| twisted pair | ||||||
| Unshielded Twisted Pair | 100/10/1000 Mbps | 100/100/100 m | 150/300/100 m | Good | Medium | Low |
| Shielded twisted pair | 100/10/1000 Mbps | 100/100/100 m | 150/300/100 m | Good | Low | Medium |
| Field cable P-296 | 100/10 Mbps | -- | 300(500)/>500 m | Good | Low | high |
| Four-wire telephone cable | 50/10 Mbps | -- | no more than 30 m | Good | high | Very low |
| Coaxial cable | ||||||
| Thin coaxial cable | 10 Mbps | 185 m | 250(300) m | Bad Requires soldering | high | Low |
| Thick coaxial cable | 10 Mbps | 500 m | 600(700) | Bad Requires soldering | high | Medium |
| Optical fiber | ||||||
| single mode optical fiber |
100-1000 Mbps |
Up to 100 km | -- | Specialist required equipment |
Missing | |
| Multimode optical fiber |
1-2 Gbps | up to 550 m | -- | Specialist required equipment |
Missing | |
*- Data transmission over distances exceeding standards is possible when using high-quality components.
Characteristics of RF cables type RK - RG
| Cable brand | Int. diameter | Diam. isolation, |
External conductor | Shell | Weight, kg/km |
Attenuation- nie, |
Recommended length up to video cameras, no more, m |
Recommended connector for connection video cameras |
||||
| mate- rial |
n*d, mm | d, mm | mate- rial |
d, mm/% | mate- rial |
d, mm | ||||||
| RK-75-1.5-11 | M | 1*0,24 | 0,24 | 1.5 PE | OM | 0,08/60% | PE | 2,4 | 8,4 | 0,32 | 50 | BNC RG-58 soldering |
| RK-75-2-11 | M | 1*0,37 | 0,37 | 2.2 PE | OM | 0,1/92% | PE | 3,3 | 16 | 0,22 | 300 | BNC RG-58 soldering |
| RK-75-2-11a | M | 1*0,37 | 0,37 | 2.2 PE | OM | 0,1/75% | PE | 3,3 | 14 | 0,23 | 200 | BNC RG-58 soldering |
| RK-75-2-13 | LM | 7*0,12 | 0,36 | 2.2 PE | AML | 0,1/92% | PE | 3,3 | 14,7 | 0,2 | 350 | BNC RG-58 soldering |
| RK-75-3-32 | M | 1*0,6 | 0,6 | 2.7 WPE | OM | 0,1/90% | PVC | 4,6 | 28,4 | 0,12 | 450 | BNC RG-58, RG-59 |
| RK-75-3,7-322a | M | 1*0,6 | 0,8 | 3.7 WPE | AL+OML | 0.1/lm65% | PVC | 6 | 37,3 | 0,085 | 600 | BNC RG-59 |
| RK-75-4-11 | M | 1*0,72 | 0,72 | 4.6 PE | OM | 0,15/92% | PE | 7±0.2 | 63 | 0,08 | 600 | BNC RG-6 soldering |
| RK-75-4-11a | M | 1*0,72 | 0,72 | 4.6 PE | OM | 0,15/75% | PE | 6.2±0.3 | 40 | 0,13 | 600 | BNC RG-6 soldering |
| RK-75-4-12 | M | 7*0,26 | 0,78 | 4.6 PE | OM | 0,15/92% | PE | 7±0.2 | 63 | 0,09 | 600 | BNC RG-6 soldering |
| RK-75-4-15 | M | 1*0,72 | 0.72/td> | 4.6 PE | OM | 0,15/92% | PVC | 7±0.2 | 72 | 0,08 | 600 | BNC RG-6 soldering |
| RK-75-4-16 | M | 7*0,26 | 0,78 | 4.6 PE | OM | 0,15/92% | PVC | 7±0.2 | 72 | 0,09 | 600 | BNC RG-6 soldering |
| RK-75-4,9-322a | M | 1*1,1 | 1,1 | 4.9 PE | AL+OML | 0.15/lm65% | PVC | 7,15 | 51 | 0,06 | 750 | BNC RG-6 |
| RK-75-9-12 | M | 1*1,35 | 1,35 | 9 PE | OM | 0,2/90% | PVC | 12.2±0.8 | 189 | 0,06 | Trunk | - |
| RK-75-9-13 | M | 1*1,35 | 1,35 | 9 PE | OM | 0,2/90% | PE | 12.2±0.8 | 169 | 0,06 | Trunk | - |
| RG-59 | M | 1*0,81 | 0,81 | 3.66 WPE | AL+OML | 0,15/67% | PVC, PE | 6 | 31 | 0,085 | 600 | BNC RG-59 |
| RG-6U | coolant | 1*1,02 | 1,02 | 4.4 WPE 4.7 WPE |
AL+OML AL+OML |
0,15/32% | PVC, PE PVC, PE |
7 | 36 | 0,09 | 650 | BNC RG-6 crimp |
| RG-11 | coolant | 1*1,63 | 1,63 | 7.11 WPE | AL+OML | /60% | PVC, PE | 10,3 | 166 | 0,05 | Trunk | - |
Electrical resistance of two copper conductors of the loop, depending on the diameter of the core and length
Calculations by formulas more accurate than the tables, and are necessary in cases where the tables do not contain the necessary data.
Ohm's law allows us to display characteristics electrical circuits through the interconnection of four main components:
- A - current (in Amps)
- V - voltage (in Volts)
- R - resistance (in ohms)
- P - power (in watts)
The relationship of these components to each other is shown on the so-called "classic wheel" (see figure below)
This simple and handy diagram helps us understand the fundamental relationships in electrical circuits.
Wire resistance (in ohms) is calculated by the formula:
where ?
- specific resistance (according to the table);
I
- wire length, m;
S
- cross-sectional area of \u200b\u200bthe wire, mm 2;
d
- wire diameter, mm.
The length of the wire from these expressions is determined by the formulas:
The cross-sectional area of the wire is calculated by the formula
S \u003d 0.785 * d 2
Resistance R 2 at temperature t 2 can be determined by the formula:
R 2 \u003d R 1,
where ?
- temperature coefficient of electrical resistance (from the table);
R1
- resistance at some initial temperature t 1 .
Usually for t 1 take 18°C, and in all the tables given the value of R 1 for t 1 = 18°C.
The permissible current strength at a given norm of current density A / mm 2 is found from the formula:
I \u003d 0.785 *? * d 2
The required wire diameter for a given current strength is determined by the formula:
If the load rate? \u003d 2 a / mm 2, then the formula takes the form:
The melting current for thin wires with a diameter of up to 0.2 mm is calculated by the formula
where d
- wire diameter, mm;
k
- a constant coefficient equal to 0.034 for copper, 0.07 for nickel, and 0.127 for iron.
The wire diameter from here will be:
d \u003d k * I pl + 0.005
|
Material |
Resistivity, Ohm x mm2 |
Specific gravity, g/cm3 |
Temperature coefficient of electrical resistance |
Melting point, °С |
Maximum working temperature; °C |
| Copper | |||||
| Aluminum | |||||
| Iron | |||||
| Steel | |||||
| Nickelin | |||||
| Constantan | |||||
| Manganin | |||||
| Nichrome |
Testing of internal power wiring
Before switching on electrical installations under voltage and putting them into permanent operation, it is necessary to check whether the installation work and whether the wiring is ready for normal operation.
To do this, an external inspection of the mounted installation is carried out, the correctness of the connection diagrams is checked, after which the state of the electrical insulation is assessed by measuring its resistance with a megohmmeter.
The megohmmeter consists of a ratiometer and a generator direct current with a manual drive or with a rectifier to connect the device to the network.
When measuring insulation resistance, the device is connected to a de-energized circuit and the generator knob is rotated, bringing the rotational speed to the nominal, i.e. 120 rpm. Without reducing the specified frequency, the handle is rotated until the arrow of the device stops moving along the scale. The arrow at the same time shows on a scale the insulation resistance of the circuit connected in series with the device.
The insulation resistance of circuits and switchboards (for each section) with all devices and devices connected to the network is measured with a megger 500 …1000 V. The insulation resistance must be at least 500 kOhm.
Insulation resistance of electric motors, measured with a megger 1000 volts, must be at least 0.5 MΩ.
In lighting wiring, the insulation resistance is determined with a megohmmeter. 1000 volts, before screwing in the lamps with the connection of the neutral wire to the luminaire body. In each section, the insulation resistance is measured between the wires and with respect to earth. It must be at least 0.5 MΩ.
Download:
1. Program for calculating the length of the voice announcement broadcast line - For reading hidden text you need to login or register.
2. The program for calculating the wire section for warning lines - To read the hidden text, you need to log in or register. .
3. Program for calculating the power cable - To read the hidden text you need
