cable network damage repair
During the operation of cable lines, for certain reasons, cables, as well as couplings and end seals, fail. The main causes of damage to cable lines with voltage 1...10 kV are as follows:
Previous mechanical damage - 43%;
Direct mechanical damage by construction and other organizations - 16%;
Defects in couplings and end seals during installation - 10%;
Damage to cables and couplings as a result of ground settlement - 8%;
Corrosion of metal cable sheaths - 7%;
Defects in cable manufacturing at the factory - 5%;
Violations during cable laying - 3%;
Aging of insulation due to long-term use or overloads - 1%;
Other and unidentified reasons - 7%.
In accordance with the requirements of the Operating Instructions for power cable lines, current or major renovation cable lines with voltage up to 35 kV. Current repairs can be emergency, urgent and planned.
Emergency repairs are necessary when, after a cable line has been disconnected, consumers of all categories are left without voltage and there is no way to supply voltage via high or low voltage cables, including temporary hose cables, or when the backup line to which the load is transferred is unacceptably overloaded and consumption limitation is required. Emergency repairs are started immediately and carried out continuously in order to turn on the cable line in the shortest possible time.
In large urban cable networks and large industrial enterprises, for this purpose, emergency recovery services have been formed from a team or several teams that are on duty around the clock and, at the direction of the dispatch service, immediately go to the scene of the accident.
Urgent repairs are necessary if receivers of the first or second category are deprived of automatic backup power, and the remaining cable lines are overloaded, which leads to consumption limitation. At the direction of the energy service management, repair crews begin urgent repairs cable lines during the work shift.
Planned repairs are carried out according to a schedule approved by the management of the energy service. The cable line repair schedule is drawn up monthly based on entries in walk-through and inspection logs, test and measurement results, as well as data from dispatch services.
Major repairs of cable lines are carried out according to an annual plan, developed annually in the summer for the next year based on operational data. When drawing up a capital repair plan, the need to introduce new, more modern types cables and cable fittings. It is planned to repair cable structures and eliminate faults in lighting, ventilation, fire fighting equipment, and water pumping devices. The need for partial replacement of cables in certain areas that limit throughput lines or that do not meet the requirements of thermal resistance in changed operating conditions of the network with increased short circuit currents.
Repair of cable lines in operation is carried out directly by the operating personnel themselves or by the personnel of specialized electrical installation organizations. When repairing existing cable lines, the following work is performed:
Disconnecting the cable line and grounding it, familiarizing yourself with the documentation and clarifying the brand and cross-section of the cable, issuing a safety permit, loading materials and tools, delivering the team to the work site;
Execution of pits, excavation of pits and trenches, identification of the cable being repaired, fencing of the workplace and excavation sites, identification of the cable in the distribution center (TP) or in cable structures, checking the absence of flammable and explosive gases, obtaining a permit for hot work;
Admitting the team, puncturing the cable, cutting the cable or opening the coupling, checking the insulation for moisture, cutting off sections of damaged cable, setting up a tent;
Laying the repair cable insert;
Repair of cable couplings - cutting of cable ends, phasing of cables, installation of couplings (or couplings and terminations);
Completion of work - closing the doors of the switchgear, transformer substations, cable structures, handing over keys, backfilling pits and trenches, cleaning and loading tools, delivering the team to the base, drawing up an as-built sketch and making changes to the cable line documentation, report on the completion of repairs;
Cable line measurements and tests.
In order to speed up repair work on cable lines, pneumatic jackhammers, electric hammers, concrete breakers, excavators, and means for heating frozen soil should be used.
Repair work on cable lines can be simple, not requiring much labor or time, or complex, lasting several days. Simple ones include, for example, repairs of external covers (jute cover, polyvinyl chloride hose), painting and repair of armored tapes, repair of metal shells, repair of end seals without dismantling the body, etc. Simple repairs are carried out in one shift by one team (unit ).
More complex repairs involve replacing large lengths of cable in cable structures with preliminary dismantling of the failed cable or laying a new cable in the ground over a section of several tens of meters (in rare cases, hundreds of meters). Carrying out repairs is made difficult by laying a cable route through complex areas with many turns, with the intersection of highways and utility lines, the large depth of the cable, and the need to warm the ground in winter. When performing complex repairs, a new section of cable (insert) is laid and two connecting couplings are installed.
Complex repairs are carried out by one or several teams, and, if necessary, around the clock and with the use of earth-moving mechanisms and other means of mechanization. Complex repairs are carried out either by the energy service of the enterprise (city networks), or with the involvement of specialized organizations for the installation and repair of cable lines.
Repair of high-voltage cables up to 10 kV, repair of cable lines.
Comprehensive repair of 0.4 kV cable (basic) - from 52 thousand rubles.
Comprehensive repair of 6/10 kV cable (basic) - from 61 thousand rubles.
Repair of one place of cable damage 380 volts - from 6 thousand rubles.
Repair of one place of cable damage 6000/10000 volts - from 11 thousand rubles.
The highest quality of work for a very reasonable price - the choice of a real businessman!
The company's field team will detect the malfunction and professionally will fulfill cable repair, the need for which is due to any of the following reasons:
- Mechanical damage during work in the laying area;
- Defects present on the couplings, both connecting and end;
- Previously committed violations of installation technology;
- Movements and/or subsidence of the soil;
- Local overheating of structural elements made of metal;
- Cable line repair, the failure of which is due to hidden manufacturing defects;
- Aging of existing insulating shells due to long periods their operation or resulting overloads.
We provide prompt power cable repair services, operated under loads up to 0.4 kV, and also carry out a full range of repair work on high-voltage cables up to 6 kV inclusive. Our teams carry out basic options repair of 10 kV cable.
Moreover, all of the above is done exclusively with our own materials, the quality of which we are confident in. That's why they price is already included in the cost of the work we perform. The customer will not have to make any additional payments.
- Comprehensive cable repairs are carried out by our team in Moscow.
- Travel to other areas is also possible, but subject to prior agreement on the details of the work with the operator.
- Cable repair work is carried out depending on the cause of its damage and location.
- Our company’s mobile team will arrive at the site of the line damage within a short time after submitting the application and carry out all the necessary work.
- We guarantee high quality work at a reasonable price.
Comprehensive repairs and cable restoration carried out by the company's field team on site Moscow and Moscow region.
At the same time, work on repairing the power cable can be carried out using several methods, depending on the cause of the malfunction and the location of its detection. In each specific case power cable repair may include:
- search for a specific location of the malfunction (damage to the cable line), which is carried out step by step in several stages;
- excavation work to provide access to the damage site;
- performing the actual repair work (restoration of the armor cover, end seals, couplings, shells, etc.);
- carrying out tests of the restored area with registration of their results in the appropriate protocol.
Power cable repair(CL), which can be performed by us, in addition to the procedures listed in the price list, can be supplemented, at the request of the client, with the following technical activities:
- Detection of a specific short circuit point, break or other damage to a single cable and/or cable line up to 10 kV inclusive.
- Installation of end and/or connecting sleeves (heat shrink) for repair of 10 sq.m. power cable.
- Maintenance and repair of cable lines with the subsequent organization of monitoring their insulation for the presence of moisture.
- Carrying out testing and electrical measuring work to determine the presence of leakage currents in cable insulation and the integrity of the latter. With subsequent registration of the results in a protocol confirming them.
- High voltage cable repair on the territory of Moscow.
By ordering work from us, you save time, money and receive a guaranteed high-quality solution to your problem. We respect our customers and our own business reputation!
Repair of cable lines is carried out on the basis of data obtained during inspection and testing of cables. The peculiarity of cable repair is that the cables being repaired may remain energized or have a residual charge as if they were in service. In addition, they may be located near live cables that are energized. All this requires repair personnel to pay special attention not only to personal safety, but also to avoid damaging nearby cables, and therefore it is important to carry out repair work in the shortest possible time, since during repair work it is necessary to switch to less reliable temporary power supply circuits.
Repair work on cables often involves excavating cable trenches, because... more than 80% of cable failures and 90% of coupling failures occur when cable lines are laid in trenches. To avoid damage to nearby serviceable cables and other communications, it is necessary to have accurate information about the location of underground communications. After reaching a depth of 0.4 m, excavation may continue only with shovels. The use of jackhammers, crowbars and other tools for loosening the soil is strictly prohibited. If cables or any other underground communications are discovered during excavation work, the work is stopped and the person responsible for the work is notified. After opening, the exposed cables and couplings are secured on a board, which is suspended from the beams thrown across the trench.
The main repair work on cable lines can be reduced to three types: repair of cable armor, repair of lead cable sheath, repair of couplings and end seals.
In case of local destruction of cable armor, the defect is eliminated as follows. At the site of destruction, the remainder of the armor is removed, the edge of the armor is soldered to the lead sheath of the cable, which is coated with a bitumen-based anti-corrosion varnish. For cable lines laid in the ground, the armor cover is not repaired during operation. If there is a need to repair the lead cable sheath, then pay attention to the nature of the damage. If damage to the cable insulation and moisture penetration into the cable are excluded, the repair is reduced to restoring the lead sheath. To do this, a lead pipe is made 70-80 mm larger than the bare part of the cable. The exposed section of the cable is placed in a prepared lead pipe, the seam of which is sealed. In the same case, when penetration of moisture into the cable is not excluded, it is necessary to check the paper insulation of the cable in the defective area for the absence of moisture. Paper insulation tapes, removed from the cable at the point of damage, are immersed in paraffin heated to 150 o C. If there is moisture in the insulation, immersion of the insulation in paraffin will be accompanied by cracking and the release of foam from it. When it is established that moisture has penetrated under the lead sheath of the cable, the damaged section of the cable is cut out, a section is inserted in its place and two couplings are installed at both ends.
When repairing couplings, it is sometimes possible to avoid the use of cable inserts: by using new couplings of greater length (extended), which make it possible to increase the cable length. If the end sleeve fails, it is cut out or dismantled, then the cable insulation is checked for moisture content. If moisture has not penetrated into the cable, they are limited to installing a new or repairing a damaged coupling. If moisture penetrates into the cable, the defective section is cut out and a new end sleeve is installed.
Safety precautions. An important condition for ensuring the safety of personnel when repairing cable lines is to carry out work according to work orders and by at least two persons. Repair work may only be carried out after the cable being repaired has been completely disconnected. Checking that there is no voltage at its ends and posting “Do not turn on - people are working” posters in places where voltage can be supplied to the cable being repaired:
When repairing cable lines, you sometimes have to cut the cable or open the coupling. Such work can be carried out by first making sure that the cable is not live. The test is carried out with a special piercer equipped with an insulating rod.
During repair work in cable structures (tunnels, collectors, channels, etc.), as well as during excavation work to excavate cable routes, before starting work, using a special device, the absence of gases harmful to breathing is established. If they are detected, workers are not allowed to work until the gas is removed.
To avoid fires when repairing cables, heating the cable and filling the blowtorch with gasoline is allowed outside the cable structures.
When testing power cables DC high voltage from the kenotron installation, it must be fenced off and people must be removed from the work site before testing begins. The test facility must be grounded before testing. Cables should be connected and tested wearing dielectric gloves, standing on an insulating base. At the end of the DC cable test, all cable cores are discharged from the accumulated electric charge through the limiting resistance provided for this purpose in kenotron installations.
Control questions
1. How is the acceptance of hidden cables?
2. What is the frequency of maintenance work on cable lines up to 35 kV?
3. What is the time frame for inspection of cable lines?
4. What types of inspections are there?
5. What is the purpose of preventative testing?
6. Who sets the frequency of preventive testing and what is its frequency?
7. When are cable terminations inspected?
8. What is monitored when inspecting openly laid cables in cable structures?
10. What type of cable line laying accounts for the greatest number of failures?
11. How are couplings repaired?
12. What are the main conditions for ensuring safety when repairing cable lines?
During their operational life, various damage may occur on cable lines, which requires elimination. cable repair.
In accordance with the requirements of the “Instructions for the use of power cable lines. Part 1. Cable lines with voltage up to 35 kV” each cable line must undergo routine or major repairs.
Maintenance can be emergency, urgent and planned.
Emergency repair is such a repair when, after disconnecting the cable line, consumers of all categories are left without voltage and there is no way to supply voltage via high or low voltage cables, including temporary hose cables, or when the backup line to which the load is transferred is unacceptably overloaded and there is no the possibility of further unloading or whether consumer restrictions are required.
Urgent repair is such a repair when receivers of the first or especially important second category are deprived of automatic backup power, and for receivers of all categories, the load on the remaining cable lines causes their overload or limitation of consumers. Repair teams begin urgent repairs of cable lines at the direction of the energy service management during the work shift.
Planned repair is the repair of all cable lines not listed above, which is carried out according to a schedule approved by the management of the energy service. The cable line repair schedule is drawn up monthly based on entries in walk-through and inspection logs, test and measurement results, as well as data from dispatch services.
Major renovation cable lines are carried out according to an annual plan, developed annually in the summer for the next year based on operating data. When overhauling a cable line, perform partial or complete replacement of sections of the cable network, painting of cable structures, re-cutting of individual end funnels, cable couplings, replacement of identification marks, installation of additional mechanical protection in places of possible cable damage.
When drawing up a capital repair plan, the need to introduce new, more modern types of cables and cable fittings is taken into account. It is planned to repair cable structures and all work related to the serviceability of lighting, ventilation, water pumping devices, and fire fighting equipment. The need for partial replacement of cables in certain sections that limit the capacity of the lines or do not meet the requirements of thermal resistance in the changed operating conditions of the network with increased short-circuit currents is also taken into account.
Repair of cable lines in operation is carried out directly by the operating personnel themselves or by the personnel of specialized electrical installation organizations. When repairing operating cable lines, preparatory work is carried out, preparation of the workplace, and preparation for installation.
Cable line repairs are simple, which do not require much labor and time, and complex when repairs continue for several days
Complex repairs are carried out by one or several teams, and, if necessary, around the clock, using earth-moving mechanisms and other means of mechanization. Complex repairs are carried out either by the energy service of the enterprise (city networks), or with the involvement of specialized organizations for the installation and repair of cable lines
Installation cable sleeve performed if the cable insulation is broken. The coupling is intended to connect different types cable. The installation of a coupling is used when carrying out repair work on damaged cable lines to ensure a reliable and durable connection of different cables, insertion into the network, and relocation of the cable line.
Installation of the coupling on the cable must be carried out carefully, in compliance with technical requirements. If the coupling is installed unprofessionally, without following a certain technology, as well as if the cross-section is incorrectly selected or the voltage does not match, damage may occur. Regardless of what kind of couplings are used - connecting, transition or cable end couplings, they must be of high quality.
All repair work (installation of cable boxes, cable replacement, etc.) must be carried out by professional specialists who have access to such work and the appropriate experience.
Proper organization of maintenance work, professional repair power cable, proper installation of the coupling, timely identification of problem areas and defects ensure long-term operation of cable lines and their reliable uninterrupted power supply.
Maintenance and repair. To ensure uninterrupted operation of cable lines and automation, telemechanics and communication networks at signaling and communication distances, teams of cable workers and cable shops are organized. Cable shop workers monitor the technical condition of cable lines and networks, repair cables, terminal and intermediate devices, underground wells and cable ducts, prepare cable facilities for work in winter, and also repair damage to cables.
Planned and control electrical measurements of all types of cable at distances with large cable networks are carried out by employees of the RTU measuring group.
A certain procedure for maintenance and major repairs has been established.
During routine maintenance of cable lines, the condition of the cable route, cable structures, cable fittings (cabinets, boxes, plinths, various couplings, etc.) is checked and identified defects are eliminated. They ensure that excavation work that has not been agreed upon in advance is not carried out on the cable laying route, eliminate damage, take measures to protect the cable from corrosion, etc. More complex and labor-intensive work that cannot be performed by personnel conducting routine maintenance is carried out during major repairs of cable lines.
Major repairs are carried out according to pre-compiled projects and estimates. The estimates include relaying and replacing individual sections of cables with reduced core insulation resistance that cannot be restored. Major repairs are planned in advance and carried out by special teams for labor-intensive work.
At distances that have telephone sewerage, during major repairs, dilapidated cable wells are rebuilt, damaged channels are restored and additional channels are laid from asbestos-cement pipes.
The overhaul plan provides for deepening the cable trench in certain areas and connecting to the air pressure cable. They carry out work to protect against electrical and soil corrosion with the inclusion of drains, replace measuring posts, repair or replace faulty boxes, replace non-standard hatches with standard ones, take measures to isolate wells from water ingress, etc.
Upon completion of the work, the repaired sections of the cable line are accepted by a special commission.
Rice. 96. Installation diagram of type USKD-1
cable problems arise due to the penetration of moisture into it when the seal of the sheath is broken due to corrosion, violation of laying rules, poor-quality soldering of cable couplings and mechanical damage caused by soil displacements or careless excavation work on the cable route. To protect the cable from moisture penetration into it if the integrity of the sheath is damaged, the cable lines are kept under constant excess pressure, which allows you to control the tightness of the sheath and determine the location of its damage. In addition, in case of minor damage to the sheath, the gas flow escaping at the site of its damage prevents moisture from penetrating into the cable, which increases the reliability of cable lines.
When the cable is kept under constant excess pressure, the cable line is divided into sealed sections called gas sections. For multichannel communication cables, the length of the sections is usually equal to the length of the amplifying section of the high-frequency circuits. Gas-tight couplings are installed at the ends of the gas section, as well as at all branches from the main cable. Excessive gas pressure is created inside the gas sections.
There are two systems for maintaining cables under excess pressure: with automatic and periodic filling of cables with gas. On cable lines of multichannel communication of the MPS, the system with automatic filling is most widely used. In this system, automatic control and drying installations AKOU are placed at the ends of the gas section, and in Lately- USCD installations. Dry air is used as gas.
The USKD-1 type installation (Fig. 96) provides automatic supply of dry air to the cable, control of gas flow, and a signal about a leak and a decrease in pressure in the gas cylinder. From a high-pressure cylinder 1 (10, 15 or 20 MPa) (or from a compressor) through a high-pressure drying chamber 2, gas is supplied to a reducer 4 with a check valve (the check valve is necessary to disconnect the cylinder from the installation when the pressure drops to 2 MPa), then into the low pressure reducer 5, at the output of which a stable pressure of 50+ 2 kPa is formed, maintained automatically at a gas flow rate of no more than 3 m/min. Next, the gas passes through the low-pressure drying chamber 12, the pneumatic alarm 6 and the rotameters block 7. In the rotameters block, after passing through the humidity indicator 10, the gas enters the rotameters 9 to monitor the gas flow of each cable and through the fittings 8 into the cables. The safety of the installation is ensured by safety valves. The cable tightness control alarm is carried out using a pneumatic signaling device 6, and the pressure reduction alarm in the cylinder is indicated by an electric contact pressure gauge 3. The pressure gauge 11 controls the gas pressure supplied to the cable.
Equipment of the USK.D-1 type provides for the connection of an air monitoring device of the VKP-1 type to determine the area of leakage of the cable sheath based on gas flow.
The exact location of the shell damage is determined using tracer gases. To do this, a valve is soldered into the coupling closest to the border of the damaged area and the excess pressure is reduced (the valve is opened for 20-30 minutes). Freon is injected into the cable within 5-10 minutes at a pressure of 50-60 kPa. To ensure gas movement along the cable, dry air is pumped at a pressure of 50-60 kPa. 12-15 hours after the introduction of freon, they begin to inspect the route, for which purpose holes with a diameter of 2 cm and a depth of 25-30 cm are first made 1.5-2 m above the cable. Using a leak detector (a device that reacts to the presence of freon), an air sample is taken in pits. The maximum gas concentration will be directly above the cable damage.
The most typical damage to a cable in service is a gradual or sudden decrease in the insulation resistance between the cable cores and between the cores and the ground (metal sheath). The cause of these damages is the penetration of moisture into the cable if it is not kept under constant air pressure. Damages such as breakage of one or more cable cores, short circuit of part of the wires with each other or with the lead sheath are also observed.
First you need to accurately determine the location of the damage. If the cable is under excess air pressure, in a system with automatic feeding gas, it is enough to know the number of doses of gas supplied to the cable when its sheath is damaged. This is determined using automatic dispensers of AKOU or USKD installations located at stations bordering the damaged section of the cable. If the cable is not kept under excess gas pressure, the location of cable damage is determined by electrical measurements or using tracer gas. A more advanced method is to detect the location of the damage using freon, when the cable route in the area of its damage is precisely marked.
To find the cable route, it is most convenient to use a cable finder, which consists of a tone frequency generator that can operate in pulse mode and in continuous oscillation mode. One terminal of the generator is connected to the cable cores, which are grounded at the opposite end, and the other terminal is connected to ground. From generator alternating current passes through the conductors of the cable, the route of which is being sought, and returns along the ground to the generator. In this case, the current around the cores creates an alternating magnetic field, changing with a frequency of about 1000 Hz.
The cable trace indicator is the finder coil (ferrite antenna) connected to the input transistor amplifier tone frequency, the output of which is connected to the headphone. The ferrite antenna is mounted on a sector, which in turn is hinged on the finder handle (rod). By rotating the sector, the ferrite antenna can be rotated to a vertical and horizontal position, as well as fixed at angles of 30, 45 and 60°.
The cable route is first found by the maximum signal volume in the phone when the antenna axis is perpendicular to the cable axis, and it is refined by the minimum signal volume when the antenna axis is parallel to the cable axis.
After determining the cable route, on straight sections it is marked with poles installed every 5-10 m, on curved sections - at shorter intervals. Then, along the route, holes are made in the ground every 1.5-2 m - holes with a diameter of 1.5-2 cm and a depth of 30 cm and the location of the leak in the cable sheath is determined using freon. To do this, near the supposed place of damage to the shell, the connecting cast iron coupling is opened, and a valve is soldered into the lead coupling, through which from 400 to 800 g of freon is introduced under a pressure of about 60 10 3 Pa. Freon is introduced using a field installation for the introduction of tracer gas (PUVIG), consisting of a cylinder with freon, a drying chamber with a humidity indicator and two pressure gauges. Air is pumped from the ends of the cable, which accelerates the spread of freon. Freon spreads along the cable and through the place of damage to the sheath to the surface of the earth from 12-15 hours to one day, depending on the density of the soil.
After this time, the location of the shell damage is determined. To do this, use a battery-powered halide leak detector, consisting of a measuring unit, a power supply and a remote probe. Moving along the cable route, one by one insert the probe of the device into the previously prepared holes. At the point where the cable sheath is damaged, freon will accumulate in the pit and the halide leak detector will signal this. Having discovered where the cable sheath is damaged, they begin to repair it.
If other damage occurs in the cable (broken wires or short circuit between wires), the location of the cable damage is determined using electrical measurements.
Operation of cable lines and networks in winter conditions. To ensure trouble-free operation of cable lines and networks in winter conditions, a number of preventive measures and preparatory work are carried out even before the onset of cold weather. First of all, cable lines, networks and cable inserts are inspected, the weakest points are identified and the detected defects are eliminated. To check the condition of the operating cable, electrical measurements of the cable circuits are carried out. Carefully inspect cable termination devices (termination boxes, boxes, cable boxes, etc.). Check that the doors and covers in the cable boxes fit tightly, since if there are cracks in the winter, snow can get in there; inspect cable supports, supports and guy wires.
Before the onset of cold weather, the cable ducts are carefully checked. Particular attention is paid to ensuring that there is no water in the channels and sewer wells, which in winter, when frozen, can severely compress the cable laid in the channels and damage it. After inspecting the wells, the top manhole covers are sealed to prevent water and dirt from entering the well during autumn rains.
TO additional work Routine maintenance of cable lines and networks in winter includes: clearing snow from hatches of cable wells, distribution cabinets and other cable fittings installed outdoors; more careful monitoring to ensure that cracks do not appear in the cable mass that protects the end sleeves due to strong fluctuations in ambient temperature; ice chipping on underwater cables if, due to a significant drop in water level, the cable is frozen into the ice off the coast.
On cable and overhead lines that have submarine cable inserts, the condition of these inserts is inspected and it is determined whether there is a danger of damage to the submarine cable by ice drift. At local hydrometeorological stations, the time of the expected ice drift and the magnitude of the expected flood are determined. Strengthen cable supports that may be in the spill area. Before the onset of ice drift, in those places where the underwater cable is laid and there is a danger of its damage, workers and special teams are constantly on duty, provided with an emergency supply of materials, boats, etc. In sections of the route where landslides and soil erosion may occur, they also take measures to prevent damage - arrange drainage systems, etc.
