During the operation of cable lines (CL), damage may occur in cables, couplings or seals. The damage is in the nature of an electrical breakdown.

During routine repairs of cable lines, the following work is performed: inspection and cleaning of cable channels, tunnels, routes of openly laid cables, end funnels, connecting couplings, straightening of cables, restoration of lost markings, determination of the heating temperature of the cable and monitoring of corrosion of cable sheaths; checking grounding and eliminating detected defects; checking access to cable wells and the serviceability of well covers and locks on them; relaying of individual sections of the cable network, high voltage testing (for cables with voltages above 1 kV or checking insulation with a megohmmeter for cables below 1 kV), replenishing funnels and couplings with cable mastic, repairing cable channels.

During major repairs of cable lines, the following is carried out: partial or complete replacement (as necessary) 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.

Repair of cables laid in trenches. If it is necessary to replace the cable line or part of it, the opening of the improved coatings is carried out with electric concrete concrete S-850 or electric hammer S-849, motorized concrete concrete S-329, pneumatic concrete concrete S-358.

The covering material is thrown onto one side of the trench at a distance of at least 500 mm from the edge, and the soil onto the other side at a distance of at least 500 mm from the edge. The trench is dug straight, and at turns - expanded to ensure the laying of cables with the required radius of curvature.

Trenches, in the absence of groundwater and underground structures, are dug without fastening vertical walls to the depth indicated below (in m):

In sandy soils................................................... .............................................1

In sandy loams............................................. ........................................................ .........1.25

In loams, clays.................................................... ........................................1.5

In particularly dense soils................................................... ....................................2

Trenches in areas where people and vehicles move are fenced off and warning signs are installed near them, and additional signal lighting is installed at night. The distance between the fence and the axis of the nearest rail on a normal gauge railway track must be at least 2.5 m, and on a narrow gauge railway track - at least 2 m.

Before laying new cables in a trench, the following work is performed: secure the pipes in the trench at places where the route intersects and approaches roads, underground communications and structures; remove water, stones and other objects from the trench and level its bottom; make a 100 mm thick bedding at the bottom of the trench with fine earth and prepare fine earth along the route for dusting the cable after laying; bricks or reinforced concrete slabs are prepared along the route to protect the cable when such protection is necessary. Materials that are susceptible to rotting and decomposition in the ground (wood, sand-lime brick, etc.) cannot be used to protect cables.

At places of intersection and convergence with engineering structures, concrete, reinforced concrete, ceramic, cast iron or plastic pipes are used. Steel pipes are used only for passing a section of the route using the pound puncture method.

The laying depth for cables with voltages up to 10 kV from the planning mark should be 0.7 m. Before laying the cable, an external inspection of the upper turns of the cable on the drum is carried out. If damage is detected (dents, punctures in the turns, cracks in the mouth guard, etc.), cable laying is allowed only after cutting out the damaged areas, checking the insulation for moisture and soldering new mouth guards to the ends of the cable. During repair work, unrolling the cable from the drum is most often done using a winch.

Cables are laid with a margin equal to 1-3% of its length (snake), to eliminate dangerous mechanical stresses during soil displacements and temperature deformations, cable laying with a snake when pulled by a winch is carried out after finishing rolling from the drum during the process of laying the cable to the bottom of the trench. When laying cables in parallel in a trench, their ends, intended for subsequent installation of couplings, are positioned with a shift of the connection points of at least 2 m. At the same time, a reserve of cable ends is provided along the length necessary for checking the insulation for moisture, installing couplings and laying the compensator arc , protecting the couplings from damage in the event of possible soil displacements and temperature deformations of the cable, as well as in case of re-cutting of the couplings if they are damaged.

In cramped conditions with large flows of existing cables, it is possible to place expansion joints in a vertical plane, placing the couplings below the cable laying level. The number of couplings per 1 km of replaced cable lines should be no more than 4 pcs. for three-core cables 1-10 kV with a cross-section of up to 3 x 95 mm2, and 5 pcs with a cross-section of 3 x 95 * 2 x 240 mm2.

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 with high-voltage direct current 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 testing cables with direct current, all cable cores are discharged from the accumulated electrical charge through a 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?

Kirov Department of Education

public educational institution

primary vocational education

vocational school No. 23

GRADUATE WORK

TOPIC: maintenance and repair of cable lines

Completed by: student of group No. 35

Bobkov Yuri Alexandrovich

Checked by: teacher Sobolev V.A.

Introduction.

Power cables.

1 Arrangement of power cables.

2 Cable blocks, overpasses, galleries, collectors, trenches.

3 Selection and use of cables.

Determination of fault locations in cable networks

1 Types and nature of damage to cable lines

2 Structure of the damage location search system

3 Characteristics of high-frequency WMD methods

4 Characteristics of low-frequency WMD methods

Repair of cable lines.

1 General instructions for repairs.

2 Repair of protective covers.

3 Repair of metal shells.

4 Restoration of paper insulation.

5 Repair of current-carrying conductors.

6 Repair of couplings.

7 Repair of end couplings for outdoor installation.

8 Repair of end seals.

9 Repair of cable lines 0.38…10 kV.

Maintenance of cable lines.

Bibliography.

Application.

Introduction

As you know, the basis for a reliable power supply to consumers is the trouble-free operation of cable lines. Uninterrupted power supply to consumers of urban networks and industrial enterprises depends on new, progressive technological solutions adopted at the design stage and the use of modern cable fittings, on high-quality cable laying and strict compliance with all requirements for the operation of cable lines.

Despite the increasing quality of cable insulation, damage cannot be ruled out. Moreover, the specific amount of damage is a fairly stable characteristic of a certain class of electrical networks.

Locating fault locations (LPO) is the most difficult and often the most time-consuming technological operation to restore a damaged network element. This is the operational task of electrical grid dispatch services.

Expenditures on weapons of mass destruction constitute a significant part of operating costs in power grids. The share of capital costs for devices for weapons of mass destruction in total capital costs is relatively small. The introduction of advanced methods and means of weapons of mass destruction provides a significant economic effect. It consists of timely identification of weak points in cable lines by conducting preventive high-voltage tests, reducing power supply interruptions, reducing the volume of repair work and reducing the cost of excavation work in the summer. The set of operations to find damage and restore the functionality of the cable line is considered as a single interconnected system.

1. Power cables

1 Arrangement of power cables

Power cables are designed to transmit electricity used to power electrical installations. They have one or more insulated conductors, enclosed in a metal or non-metallic sheath, on top of which, depending on the laying and operating conditions, there may be a protective cover, and, if necessary, armor.

Power cables consist of conductive cores, insulation, sheaths and protective coverings. In addition to these basic elements, the design of power cables may include screens, neutral conductors, protective grounding conductors and fillers (Fig. 1.1).

Conducting conductors intended for the passage of electric current are main and zero. The main cores are used to perform the main function of the cable - transmitting electricity. Neutral conductors, designed to carry the difference in phase (pole) currents when their load is uneven, are connected to the neutral of the current source.

Protective grounding conductors are auxiliary and are designed to connect metal parts of the electrical installation that are not under operating voltage, to which the cable is connected... with the protective grounding circuit of the current source.

Insulation serves to ensure the necessary electrical strength of the conductive cores of the cable in relation to each other and to the grounded shell (earth).

Screens are used to protect external circuits from the influence of electromagnetic fields of currents flowing through the cable, and to ensure symmetry of the electric field around the cable cores.

Fillers are designed to eliminate free spaces between cable structural elements in order to seal, impart the required shape and mechanical stability to the cable structure.

Rice. 1.1. Cross-sections of power cables: a - two-core cables with round and segmented cores; b - three-core cables with belt insulation and with separate sheaths; c - four-core cables with zero core sector, round and triangular shapes; 1 - conductive core; 2 - zero core; 3- core insulation; 4 - screen on the conductor; 5 - waist insulation; 6 - filler; 7 - screen on the core insulation; 8 - shell; 9 - armored cover; 10 - outer protective cover

Sheaths protect the internal elements of the cable from moisture and other external influences.

Protective covers are designed to protect the cable sheath from external influences. Depending on the cable design, protective covers include a cushion, an armored cover and an outer cover.

The various cable designs are assigned letter suffixes.

Power cables with paper insulation, impregnated or depleted, are intended for use in stationary installations and in the ground at ambient temperatures from plus 50 to minus 50 ° C and relative humidity up to 98% at temperatures up to plus 35 ° C. They are manufactured for rated voltages of 1, 6 and 10 kV alternating current with a frequency of 50 Hz, but can be used in direct current networks (Fig. 1.2).

Rice. 1.2. Power cables: a - paper; and b - rubber insulation; 1 - outer cover; 2 - armor tape; 3 - cable yarn; 4 - cable paper; 5 - shell; 6 - waist insulation; 7 - filler; 8 - core insulation; 9 - conductor

Power cables with paper insulation, impregnated with a non-drip compound, are intended for laying on vertical and inclined sections of routes without limiting the difference in levels and operation at an ambient temperature from plus 50 to minus 50 ° C and a relative humidity of 98% at temperatures up to plus 35 ° C and are manufactured for voltages of 6 and 10 kV AC with a frequency of 50 Hz, but can also be used in DC networks.

Power cables with plastic insulation, in a plastic or aluminum sheath with or without protective covers, are intended for the transmission and distribution of electricity in stationary installations at a rated alternating voltage of 0.66; 1; 3 and 6 kV with a frequency of 50 Hz.

The cables can be used at ambient temperatures from minus 50 to plus 50 °C, relative air humidity of 98% at a temperature of plus 35 °C, including when laid outdoors with protection from solar radiation.

1.2 Cable blocks, overpasses, galleries, collectors, trenches

The main method of channeling electrical energy in industrial enterprises is cable lines. At large enterprises, the number of cable lines can reach up to 25,000 with a total length of up to 2,500 km. To accommodate such a number of cables, it is necessary to install special cable structures. The simplest and cheapest structure is an earthen trench, but since the number of damages with this method is about 40%, it is used less frequently compared to laying in special structures.

Enterprises rarely give preference to any one laying method and more often use mixed laying. The following structures are used:

Earthen trench. The depth of the trench from the planning mark for cables with voltage up to 10 kV should be 0.8 m, when crossing streets and squares - 1.1 m

Fig.1.1. Laying cables in a trench

A smaller trench depth (up to 0.6 m) is allowed when introducing cables into buildings, structures, as well as at intersections with underground structures, provided that the cables are protected from mechanical damage in sections up to 5 m long. The width of the trench when laying power cables in it is up to 10 kV is accepted to be no less than that indicated in the table. 1.2 and in Fig. 1.2. The cables are laid on the bedding and covered with a layer of fine earth on top,
free of construction waste and slag. The routes are marked with identification signs fixed on the walls of permanent buildings and structures or on angle steel posts (pickets). Signs are placed at corners and turns of the route, at places where couplings are installed, at intersections of communication routes (on both sides), and at entrances to buildings. Signs measuring 100 x 100 mm indicate the voltage sign (in red paint), the designation of the cable route, the distance from the structure (in numbers) and the direction to it (arrows), and the sign number (in black paint). The background of the sign is white.

Fig.1.2. Dimensions of the trench for laying cables 1...10 kV: B1 - size at the bottom of the trench; B2 - size at the surface of the earth; B3 - withdrawal zone

Examples of identification marks:

Fig.1.3. Cable signs: a - trench; b - cable coupling; c - turn the trench at an angle

Channel sizes:

Width - 600...1200 mm, height - 300...900 mm.

This installation method protects well from mechanical damage, but where metal or aggressive substances may be spilled, the construction of cable channels is not allowed (Fig. 1.5).

A cable tunnel is an underground structure (corridor) with supporting structures located in it for placing cables and couplings on them, allowing installation, repairs and inspections with free passage along the entire length (Fig. 1.6)

The CT is constructed from prefabricated reinforced concrete and the outside is covered with waterproofing. Depth - 0.5m.

Passages in cable tunnels, as a rule, must be at least 1 m, but it is permissible to reduce passages to 800 mm in sections no more than 500 mm long.

Rice. 1.4. Prefabricated reinforced concrete channels: a - tray type LK; b - from prefabricated slabs type SK; 1 - tray; 2 - floor slab; 3 - sand preparation; 4 - plate; 5 - base.

Fig.1.5. Options for laying cables in cable channels: a - arrangement of cables on one wall on hangers; b - the same on the shelves; c - the same on both walls on suspensions; d - the same on one wall on hangers, on the other on shelves; d - the same on both walls on the shelves; e - the same at the bottom of the channel

The tunnel floor must have a slope of at least 1% towards the catch basins or storm drains. In the absence of a drainage device, drainage wells measuring 0.4 x 0.4 x 0.3 m, covered with metal gratings, must be installed every 25 m. If it is necessary to move from one mark to another, ramps with a slope of no more than 15° must be installed.

The tunnels must be protected from the ingress of groundwater and process water and the drainage of soil and storm water must be ensured.

Tunnels must be provided primarily with natural ventilation. The selection of a ventilation system and the calculation of ventilation devices are made on the basis of heat emissions specified in the construction specifications. The temperature difference between the incoming and exhaust air in the tunnel should not exceed 10 ºС.

Ventilation devices must be automatically switched off, and air ducts must be equipped with remotely or manually controlled dampers to stop air from entering the tunnel in the event of a fire.

The tunnel must be provided with permanent means for remote and automatic fire extinguishing.

Sensors must be installed in the tunnels to detect the appearance of smoke and an increase in ambient temperature above 50 °C. Collectors and tunnels must be equipped with electric lighting and a power supply for portable lamps and tools.

Extended cable tunnels are divided along their length by fire-resistant partitions into compartments no more than 150 m long with doors installed in them with a width of at least 0.8 m. Doors from the outer compartments must open into the room or out. The door to the room must be opened with a key from both sides. The external door must be equipped with a self-closing lock that can be opened with a key from the outside. Doors in the middle compartments must open towards the stairs and be equipped with devices that secure their closed position. These doors open on both sides without a key.

The laying of cables in collectors and tunnels is calculated taking into account the possibility of additional cable laying in an amount of at least 15%.

Power cables with voltages up to 1 kV should be laid under cables with voltages above 1 kV and separated by a horizontal partition. It is recommended to lay different groups of cables, namely operating and backup voltages above 1 kV, on different shelves separated by horizontal fireproof partitions. Asbestos-cement slabs, pressed, unpainted, with a thickness of at least 8 mm, are recommended as partitions. The laying of armored cables of all cross-sections and unarmored conductors with a cross-section of 25 mm2 and above should be carried out on structures (shelves), and unarmored cables with a cross-section of conductors of 16 mm2 and less should be laid on trays laid on cable structures.

Cables laid in tunnels must be firmly secured at end points, on both sides of bends and at couplings.

To avoid installing additional couplings, you should select the construction length of the cables.

Each coupling on power cables must be laid on a separate shelf of the supporting structures and enclosed in a protective fireproof casing, which must be separated from the upper and lower cables along the entire width of the shelves by protective asbestos-cement partitions. In each tunnel and channel it is necessary to provide free rows of shelves for laying couplings.

To pass cables through partitions, walls and ceilings, pipes made of fireproof pipes must be installed.

Where cables pass through pipes, the gaps in them must be carefully sealed with fireproof material. The filling material must provide adhesion and be easily destroyed in the event of laying additional cables or their partial replacement.

Unarmored cables with a plastic sheath may be secured with brackets (clamps) without gaskets.

The metal armor of cables laid in tunnels must have an anti-corrosion coating. The distance between the shelves of cable structures when laying power cables with voltages up to 10 kV must be at least 200 mm. The distance between the shelves when installing a fire-resistant partition when laying cables must be at least 200 mm, and when laying a coupling - 250 or 300 mm - depending on the size of the coupling (Fig. 1.7).

Fig.1.6. Cable arrangement in the tunnel: a - rectangular section tunnel; b - circular tunnel; 1 - tunnel block; 2 - stand; 3 - shelf; 4 - lamp; 5 - zone of fire detectors and pipelines for mechanized dust collection and fire extinguishing; 6 - power cables; 7 - control cables

A cable collector is a structure designed for the general placement of cable lines, heat pipelines and water pipes.

The collector is constructed from reinforced concrete structures of round and rectangular sections. Circular collectors are made at a depth of no more than 5 m using a closed method. The collector is equipped with ventilation, pumps and is controlled from a control center. Telephone communication must be provided. Collector dimensions: diameter - 3.6 m; width - 2.5 m; height - 3.0 m (Fig. 1.9).

A cable block is a structure with pipes (channels) for laying cables with associated wells.

Cable blocks are constructed from reinforced concrete panels 6 m long with 2-3 channels inside made of asbestos-cement or ceramic pipes. The blocks are laid on a reinforced concrete pad and protected with waterproofing. The laying depth is not less than 0.7 m, and at intersections - not less than 1 m. The joints of the panels are filled with mortar, having previously placed a tow rope in the gap. Pass-through or branching wells are installed every 150 m. The minimum height of wells is 1.8 m. Laying in blocks is the most reliable, but less economical.

REPAIR OF CABLE AND CABLE LINES

1. GENERAL INSTRUCTIONS FOR CABLE REPAIR

During operation cable lines For certain reasons, cables, as well as couplings and terminations, fail.

Main causes of damage cable lines voltage 1-10 kV are as follows:

1. Previous mechanical damage - 43%.
2. Direct mechanical damage by construction and other organizations - 16%.
3. Defects in couplings and end seals during installation - 10%.
4. Damage to cables and couplings as a result of ground settlement - 8%.
5. Corrosion of metal sheaths of cables - 7%.
6. Defects in cable manufacturing at the factory - 5%.
7. Violations during cable laying - 3%.
8. Aging of insulation due to long-term use or overloads - 1%.
9. Other and unidentified reasons - 7%.

The average data for the last ten years in the Moscow cable network is presented.

In accordance with the requirements of the “Operating Instructions power cable lines. Part 1. Cable lines with voltage up to 35 kV each cable line must undergo current or capital repairs.

Current repairs can be emergency, urgent and planned.

Emergency repairs This is called 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 way further unloading or consumer restriction is required.

Emergency repairs are started immediately and carried out continuously in the shortest possible time and turn on the cable line and work.

In large city ​​cable networks and at large industrial enterprises, for this purpose, emergency recovery services have been formed from a team or several teams, which are on duty around the clock and, at the direction of the dispatch service, immediately go to the scene of the accident.

Urgent repairs This is called 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. To urgent cable line repair Repair teams begin at the direction of the energy service management during the work shift.

Scheduled repairs- this 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. Cable line repair schedule compiled 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 is 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 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, fire-fighting equipment, water pumping devices. The need for partial replacement of cables in certain areas that limit the capacity of lines or do not meet the requirements of thermal resistance in changed operating conditions of the network with increased currents is also taken into account short circuit

Repair of existing cable lines 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:

Preparatory - 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;

Preparation of the workplace - making pits, excavating pits and trenches, identifying the cable to be repaired, fencing the workplace and excavation sites, identifying 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;

Preparation for installation - admission of 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 a repair cable insert;

cable joint repair- cutting of cable ends, phasing of cables, installation of couplings (or couplings and terminations);

Registration of the 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, mechanization should be widely used when performing excavation work: pneumatic jackhammers, electric hammers, concrete breakers, excavators, means for heating frozen soil.

Special mobile cable workshops are used to transport repair crews

Cable line repairs There are simple ones that do not require much labor and time, and complex ones when the repair lasts several days.

Simple repairs include, for example, repairs of external covers (jute cover, PVC hose), painting and repair of armor tapes, repair of metal shells, repair of end seals without dismantling the housing, etc. The listed repairs are carried out in one shift by one team (unit).

Complex repairs include those when it is necessary to replace large lengths of cable in cable structures with preliminary dismantling of the cable that has failed, or to lay a new cable in the ground over a section several tens of meters long (in rare cases, hundreds of meters).

Repairs are complicated in most cases by the fact that the cable route passes through complex sections with many turns, with the intersection of highways and utility lines, with a large depth of cable, and also in winter, when it is necessary to warm the ground. When performing complex repairs, a new section is laid cable (insert) and two couplings are mounted

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.

2. REPAIR OF PROTECTIVE COVERS

Repair of external jute covering. A cable stretched through pipes, blocks or other obstacles, which has stripped off the impregnated cable yarn and the remaining outer covers to the steel armor, must be restored. Repair is carried out by winding with resin tape in two layers with 50% overlap, followed by coating this area with heated bitumen mastic MB 70 ( MB 90).

Repair of PVC hose and sheaths. The first method of repairing a polyvinyl chloride hose or casings is welding, which is carried out in a stream of hot air (at a temperature of 170-200 ° C) using a welding gun with electrically heated air (Fig. 1) or a gas-air gun (Fig. 2). Compressed air is supplied under pressure 0.98-104 Pa from a compressor, compressed air cylinder, portable unit with a hand pump.

Fig 1. Welding gun PS-1 with electrical heating: - nozzle for hot air outlet, 2 - heating air chamber; 3 - fitting for supplying compressed air, 4 - electrical wire

A polyvinyl chloride rod with a diameter of 4-6 mm is used as a welding additive.

Before welding, areas to be repaired must be cleaned and degreased with gasoline, foreign bodies must be cut out with a cable cutter and protruding edges and burrs must be cut off in places where the hose is damaged.

To repair punctures in small holes and cavities, the damage site in the hose or sheath and the end of the filler rod are heated for 10-15 seconds with a stream of hot air, then the jet is withdrawn, and the end of the rod is pressed and welded to the hose at the heating site. After cooling, making sure that the welding of the rod is strong by lightly tugging it, the rod is cut off.

To seal and level the weld seam, the repair area is heated until signs of melting appear, after which a piece of cable paper folded in three or four layers is pressed against the heated area by hand. For reliability, the operation is repeated 3-4 times.

To repair a hose or shell that has cracks, slits and cutouts, the end of the filler rod is welded to the entire area of ​​the hose at a distance of 1-2 mm from the damage site.

After making sure that the welding is strong, direct the air stream so that the lower part of the filler rod and both sides of the slot or slot are simultaneously heated. By pressing lightly on the rod, the latter is laid and welded along the crack or slot. Welding of the rod is completed in its entirety at a distance of 1-2 mm from the damage. Then the protruding surfaces of the rod are cut off with a knife and the welded seam is leveled.

Hose or sheath ruptures are repaired using polyvinyl chloride patches or cut cuffs.

The patch is made of plastic so that its edges overlap the tear site by 1.5-2 mm. The patch is welded along the entire perimeter to the hose, and then a filler rod is welded along the resulting seam, and the protruding surfaces of the rod are cut off and the seam is leveled at the welding site.

To repair a hose or sheath using a split cuff, cut off a piece of polyvinyl chloride tube 35-40 mm longer than the length of the damaged area, cut the tube lengthwise and put it on the cable symmetrically to the damaged area. The cuff is temporarily secured with polyvinyl chloride or calico tape with a pitch of 20-25 mm, the end of the rod is welded at the junction of the cuff with the hose (sheath), and then the rod is laid and welded around the end of the cuff. After welding both ends of the cuff to the hose (shell), remove the temporary fastening tapes, weld the rod along the cut of the cuff, cut off the protruding surfaces of the rod and make the final alignment of all welds.

According to the second method repair of PVC hoses and cable sheaths can be performed using epoxy compound and glass tape. The surface of the hose or sheath is pre-treated as indicated above, and additionally roughness is created on it using a hog file. The place of damage and beyond its edges at a distance of 50-60 mm in both directions is lubricated with epoxy compound K-P5 or K-176 with hardeners introduced into it. Four to five layers of glass tape are applied over the layer of epoxy compound, each of which is also coated with a layer of compound.

Temporary repairs to hoses and casings to prevent
penetration of moisture under the shell cable, and also to prevent the bitumen composition from leaking out from under the hose, it is allowed to carry out using adhesive polyvinyl chloride tape with a 50% overlap in three layers with the top layer coated with polyvinyl chloride varnish No. 1. According to the second method, temporary repairs are carried out with LETSAR tape in three layers with 50 % overlap.

Painting armor tapes. If, during inspections in cable structures on openly laid cables, damage to the armored covering of the cable is detected by corrosion, they are painted. It is recommended to use heat-resistant pentaphthalic varnishes PF-170 or PF-171 (GOST 15907-70*) or heat-resistant oil-bitumen paint BT-577 (GOST 5631-79*).

The best way to paint is to use a spray gun, or, if it is not available, a brush.

Repair of armor tapes. On openly laid cables, detected sections of destroyed armor tapes are cut off and removed. Temporary bandages are made in places where the tapes are cut. Next to the temporary bands, both tapes are carefully cleaned to a metallic shine and served with POSSu 30-2 solder, after which the grounding wire is secured with bands of galvanized wire with a diameter of 1-1.4 mm and soldered with the same solder. The cross-section of the grounding conductor is selected depending on the cross-section of the cable cores, but not less than 6 mm2.

When tinning and soldering armored tapes, solder fat is used. The duration of each soldering should be no more than 3 minutes. Temporary bandages are removed. An anti-corrosion coating is applied to the exposed area of ​​the shell.

In cases where mechanical impacts are possible on the cable section being repaired, one layer of armor tape is additionally wound around it, which is previously removed from the cable section with intact armor. The tape is wound with 50% overlap and secured with galvanized wire bands. In this case, the grounding conductor must be fluffed out along the entire length of the jumper in order to create a tight fit of the armor around the section of the cable being repaired

3. REPAIR OF METAL SHELLS

At damage to the cable sheath(cracks, punctures), when there is a leak of oil-rosin composition in this area, the sheath is removed from the cable on both sides of the damage site at a distance of 150 mm from the damage site. The top layer of the belt insulation is removed and checked for moisture in heated paraffin.

If there is no moisture and the insulation is not destroyed, the lead or aluminum sheath is repaired.

From sheet lead 2-2.5 mm thick, a strip is cut out 70-80 mm wider than the bare section of the cable and 30-40 mm longer than the circumference of the cable along the sheath. Two filling holes are made in the strip so that they are located above the exposed part of the cable. The strip is thoroughly cleaned of dust and dirt with a rag soaked in gasoline.

The removed semiconductive layer of paper and the top tape of the waist insulation are restored and secured with bandages made of cotton threads. The area is scalded with MP-1 cable mass.

A strip of lead is wrapped around the bare part of the cable so that it extends evenly to the edges cable sheath, and the edges of the resulting lead pipe overlapped each other by at least 15-20 mm. First, the longitudinal seam is soldered with POSSU 30-2 solder, and then the ends of the pipe are bent to the cable sheath and soldered to it.

For cables with an aluminum sheath, in the place where the lead pipe is soldered, the cable sheath is served with grade A solder. The coupling is filled with hot cable mass MP-1. After cooling and topping up, the filling holes are sealed. A bandage of copper wire is applied to the soldered area at the ends, turn to turn with a diameter of 1 mm with an outlet of 10 mm to the cable sheath and is soldered to the sheath. The repaired area is covered with resin tape in two layers with 50% overlap.

In the event that moisture has penetrated under the sheath or the belt insulation is damaged, as well as the core insulation, the section of cable is cut out along the entire length where there is moisture or damage to the insulation. Instead, a piece of cable of the required length is inserted and two connecting couplings are installed. The cross-section and voltage of the cable must correspond to the cut section.

You can use a different brand of cable for insertion, but its design is similar to the cut section.

4 RESTORATION OF CABLE PAPER INSULATION

In cases where the current-carrying conductors are not damaged, but the conductor insulation and belt insulation are damaged, but there is no moisture in it, the insulation is restored, followed by the installation of a split lead coupling.

The cable is excavated to such a length that it is possible to create sufficient slack in the cable to separate the cores from each other. After dividing the conductors and removing the old insulation, the insulation of the conductors is restored by applying paper rollers or LETSAR tape with pre-treatment with MP-1 scalding mass. A split lead coupling is installed and the longitudinal seam is first soldered, and then the coupling is soldered to the cable sheath.

This repair can be performed on horizontal sections of cable routes, where there is no increased oil pressure, since a coupling with longitudinal soldering has less mechanical strength.

5. REPAIR OF CURRENT-CONDUCTING CABLE CORES

If the cable cores break at a small length and it is possible to tighten the cable due to the “snake” made during installation, the usual repair of the lead or epoxy coupling is carried out. In the event that there is no supply of cable, extended connecting sleeves and couplings can be used. Repair in this case is carried out with one lead coupling. In all other cases, when repairing current-carrying cable cores, a cable insert is used and two lead or epoxy couplings are installed.

6. REPAIR OF CONNECTING COUPLINGS

Necessity coupling repair or the installation of the cable insert and two couplings is installed after inspecting the coupling and disassembling it.

In the event that a breakdown occurs from the soldering point of the conductor or from the sleeve to the body of the lead coupling and the destruction from the breakdown is small in size and the insulation is not moistened, the coupling is sequentially disassembled and the damaged part of the insulation is disassembled. Then the insulation is restored with paper rollers or LETSAR tape and scalded with mass MP-1. The split coupling body is installed, and all further operations for assembling the coupling are performed.

If a breakdown occurs in the neck of the coupling from the core to the edge of the shell and the insulation is not moistened, the coupling is disassembled. Then a section of the armor and sheath is cut to the length necessary for convenient separation of the cores. The insulation of the damaged core is restored and scalding is performed. The extended split lead coupling body is installed and all coupling installation operations are performed.

If it is impossible to make an extended coupling due to large damage, then cable insertion is used with the installation of two couplings according to the technology provided for in the technical documentation.

In most cases, damage to couplings occurs during preventive tests with increased voltage. And if repairs are not started immediately after determining the location of the damage, moisture begins to enter the coupling. In this case, repair of the damaged coupling is carried out by cutting out the defective coupling and cable sections. As a rule, the longer a damaged and unrepaired coupling lies in the ground, the longer the cable insertion has to be made for restoration when repairing a cable line.

7. REPAIR OF END COUPLINGS FOR OUTDOOR INSTALLATION

Outdoor terminations in most cases, they fail to work during rainy periods of the year or at high relative humidity and, as a rule, have large defects and destruction inside the coupling. Therefore, the damaged coupling is cut off, the cable insulation is checked for moisture, and if the paper insulation is not moistened, the coupling is installed in accordance with the requirements of the technical documentation. If the cable length at the end of the line has sufficient margin, then repairs are limited to installing only the end coupling. If the cable supply is not enough, then a cable of the required length is inserted at the end of the cable line. In this case, it is necessary to install connecting and end couplings.

Dismantled couplings can be used for re-installation. But to do this, it is necessary to clean the housing and all parts of the coupling from soot, wash them with gasoline and dry them.

IN outdoor terminations with a metal body, check the seals and tighten the nuts once a year during the entire period of operation. At the same time, inspect the contact connections and, if necessary, clean the contact surfaces and tighten the bolts.

Systematically (as needed according to the inspection results) the soldering areas, reinforcement seams and seals are painted with XB-124 enamel.

The surface of epoxy end couplings for outdoor installation must be painted with air-drying enamels EP-51 or GF-92HS during operation (once every 3-5 years, depending on local conditions). Painting is carried out in dry weather, having previously cleaned the surface of the coupling and insulators

The insulators of the terminations of external and internal installations, as well as the insulating surfaces of the terminations, must be periodically cleaned of dust and dirt with a lint-free cloth moistened with gasoline or acetone. Cable termination fittings in workshops of industrial enterprises and areas with conductive conductive materials should be subjected to more frequent cleaning. dust

The frequency of wiping and cleaning the cable end fittings at a given electrical installation is determined by the chief engineer of the local power company.

8. REPAIR OF END SEALS

If the termination body is destroyed and the cores in the spine are burnt out, the repair of the terminations is carried out in the same way as the repair of end couplings, with the exception that the termination body and parts cannot be reused.

End seal repair in steel funnels, when the insulation of the cores is destroyed, it is carried out in the following sequence - the destroyed insulation of the cores or that has become unusable (contamination, moisture) is removed from the cores, one layer of paper insulation is rolled up, winding is carried out in five layers with a 50% overlap with adhesive polyvinyl chloride tape or three layers of rubberized tape followed by coating with insulating tapes or paints. Instead of the indicated tapes, repairs can be performed using LETSAR tape (two layers) and PVC tape (one layer).

In case of cracking, peeling, partial failure and significant contamination of the filling composition, especially when these defects are accompanied by a noticeable displacement of the cores between themselves or towards the funnel body (which can in turn be caused by an incorrect position or absence of a spacer plate), the steel funnel should be completely refilled.

The old filling compound is removed (melted), the funnel is lowered down and cleaned of soot and dirt. A new seal is rolled up (under the funnel), and the funnel is put in place.

The neck of the funnel is wrapped with resin tape, and the funnel along with the cable is attached to the supporting structure with a clamp. The correct position of the porcelain bushings is checked. The funnel is filled with a filling compound (MB-70, MB-90).

Repair of PVC tape end seals is carried out in the presence of an impregnating composition in the spine or on the cores, in case of cracking and breaks of the tapes.

The repair technology consists of dismantling old tapes and winding new PVC or LETSAR tapes on the cores.

Epoxy End Seals Repair if the windings on the cores are destroyed, it is carried out with the dismantling of old tapes, restoration of new LETSAR tapes and additional filling of epoxy compound so that the tapes extend into the poured compound by at least 15 mm.

When the impregnating composition flows through the cable in the root of the seal, the lower part of the seal in a section of 40-50 mm and at the same distance the section of armor or sheath (for unarmored cables) are degreased. A two-layer winding made of cotton tape lubricated with an epoxy compound is applied to the grease-free section of the termination body and the adjacent cable section 15-20 mm wide. A repair mold is installed (Fig. 3), which is filled with epoxy compound.

Rice. 3. Installation of a repair form to eliminate leakage of the impregnating composition at the point where the cable enters the termination body:
1 - seal body, 2 - repair form; 3 - leak location

Rice. 4. Installation of a repair form to eliminate a leak at the point where the cores exit the casing:
1 - repair form; 2 - leak location, 3 - seal body

If the tightness is broken at the point where the conductors exit the termination body, the upper flat part of the termination body and sections of tubes or winding of conductors 30 mm long adjacent to the housing are degreased. A removable repair form is installed (Fig. 5 4), the dimensions of which are selected depending on the standard size of the seal. Filling the mold with the compound is done in the same way as in the previous case.

If the tightness on the conductors is broken, the defective section of the tube or conductor winding is degreased and a repair is applied.

Two-layer winding made of cotton tapes with generous coating of each turn of the winding with epoxy compound or LETSAR tape in three layers.

If the tightness at the junction of the tube or winding with the cylindrical part of the tip is broken, the surface of the bandage and the section of the tube or winding of the core with a length of 30 mm are degreased. A two-layer winding of cotton tapes is applied to the fat-free areas with a generous coating of compound on each turn of the winding. A dense bandage of twisted twine is placed on top of the winding and also coated with an epoxy compound.

In accordance with the requirements of RD 34.20.508 “Instructions for the operation of power cable lines. Part 1. Cable lines with voltage up to 35 kV,” current repairs can be emergency, urgent and planned.

Emergency repair - repair in which, after disconnecting the cable line, the voltage along 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 possibility of further unloading or consumer limitation is required.

Urgent repairs - repairs in which 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.

Electricity receivers of industrial enterprises are divided into the following groups:

Group 1 - three-phase current receivers with voltage up to 1000 V, frequency 50 Hz;

Group 2 - three-phase current receivers with voltage above 1000 V, frequency 50 Hz.

1st category of power supply- receivers, an interruption in the power supply of which may entail a danger to human life or significant material damage associated with damage to equipment, mass defects of products or long-term disruption of a complex technological production process.

Scheduled repairs - repairs of all cable lines not listed above, which are carried out according to a schedule approved by the management of the energy service.

A plan - a schedule for repairs of cable lines is drawn up monthly based on entries in the walk-through and inspection logs, test and measurement results, as well as according to 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 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, 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.

Cable line repairs can be simple, which do not require much labor or time, or complex, when the repair lasts several days.
Simple repairs include, for example, repairs to external covers, painting and repair of armor strips, repairs to metal shells, and repairs to end seals without dismantling the housing. The listed repairs are carried out in one shift by one team (unit).

Complex repairs include those repairs when it is necessary to replace large lengths of cable in cable structures with preliminary dismantling of the cable that has failed.

Let us consider in detail the technological process of repairing a high-voltage cable that failed during an emergency in winter, since it is during such repairs that the electrician’s working conditions are the worst. A diagram of the technological process for repairing a cable that failed in winter is presented in Figure 2.

Signal arrival

The signal is sent to the RES dispatcher on duty on the computer. Upon receipt of information about operational disturbances, the duty dispatcher of the distribution zone must: