Maintenance and repair of cable lines. Maintenance of linear cable structures. Inspection of cable duct routes

Cable lines for their purpose are divided into intrasite, local, intrazonal, trunk, international.

• intrasite - networks on the territory of one object (plant, oil depot ...), the purpose is to provide technological and industrial communication within the object. Example - There is a collection of storage tanks for liquid chemicals. The tanks have temperature, level and other sensors. The cable through which signals from the sensors are transmitted to the server room for monitoring and processing will be part of the on-site networks.
• local - cable lines between buildings in the city (different enterprises) or nearby settlements (townships, villages ...), purpose - providing communication at the local level, for example, telephone channels for connecting a departmental automatic telephone exchange to a city automatic telephone exchange.
• intrazonal - cable lines within one edge, area, purpose - to provide communication within this area.
• trunk - cable lines passing (connecting) more than one subject, the purpose is to provide communication between the subjects.
• international - cable lines passing through the border of states (s), purpose - providing communication between countries (Internet).

Composition

Cable lines consist of communication nodes, unattended regeneration (amplification) points - NRP, NUP, cable route.

• communication center - communication facility in which the equipment of transmission systems is installed. There are serviced, semi-serviced and unattended. In the serviced communication centers, there is a round-the-clock watch; engineering and technical personnel may be present during the day. During working hours, personnel are in semi-serviced units, and the unit is closed during off-hours. Maintenance of communication equipment in an unattended communication center is carried out according to a schedule or as needed. Physically looks like a building or block container.
• maintenance-free regeneration (amplification) points - points at which regeneration is carried out ( digital system transmission) or amplification (analog or digital transmission system) of the signal. Physically represents a container (for example, a barrel) buried in the ground at a shallow depth, in which a regenerator or amplifier is placed. A buried container usually has a superstructure (wood, brick, iron or reinforced concrete). The location of the regenerator or amplifier in the upper part of the superstructure is also found. Within the city limits, it is possible to locate the NRP / NUP in a building, at an underground metro station or in a switch cabinet.

In addition to the regeneration / amplification equipment, power supply equipment (external or remote), rechargeable batteries, heating, ventilation and air conditioning devices, lighting devices, telecontrol devices (air pressure control in the cable and in the cylinder, door closing control, etc.) covers, control of the presence of water in the chamber, temperature control, humidity control, power control), equipment for maintaining the cable under excessive air pressure, electric compressor units, compressed air cylinders.

• cable route (route) - a cable laid in the ground (most often outside a settlement), in a sewer (most often in a large settlement). This also includes cable wells, pits, signal posts and signs, lead-in cable rooms and other linear structures.

If a transmission system is mounted on a cable line, then we get a communication network.

Links

• Telephone network user guide (Russian)
• Guidelines for the preparation of work projects (PPR) for the construction of linear structures of trunk and intra-zone cable communication lines (Russian)

Wikimedia Foundation. 2010.

See what "Cable communication lines" are in other dictionaries:

communication lines - communication lines: transmission lines, physical circuits and line-cable communication structures. [Federal Law "On Communications", article 2, paragraph 7]. Source: GOST R 53111 2008: Stability of the public communication network. Requirements and Methods ... ...

Communication lines - 1. Transmission lines, physical circuits and linear cable communication facilities Used in the document: dated 07.07.2003 No. 126 FZ 2. Transmission lines, physical circuits and linear cable communication facilities Used in the document: Order of the Ministry of the Russian Federation on ... Telecommunication Dictionary

Power transmission lines (PTL) and overhead communication lines and technical means of control (LS) - 7.3.30. Power transmission lines (PTL) and overhead communication lines and technical means of control (LS) in undeveloped areas are recognized by dark parallel aerial photographs of shadows from supports *. Usually, the pictures show the farms themselves, ... ... Dictionary-reference book of terms of normative and technical documentation

Communication lines - 7) communication lines transmission lines, physical circuits and linear cable communication facilities; ... Source: Federal Law of 07.07.2003 N 126 FZ (as amended on 28.07.2012) On communication ... Official terminology

COMMUNICATION LINES - according to Federal law "On Communication" dated 07.07.2003 No. 126 FZ, - transmission lines, physical circuits and linear cable communication facilities ... Records management and archiving in terms and definitions

Radio communication lines formed by a chain of transceiver stations, allowing information to be transmitted over distances exceeding the confident transmission distance of one pair of transceiver stations. They successfully complement cable communication lines in cases of their ... Encyclopedia of technology

dispatch communication lines - 3.3 dispatcher communication lines: Communication lines (cable, wireless) intended for the exchange of information between dispatcher control devices and the dispatch console. A source … Dictionary-reference book of terms of normative and technical documentation

STO 70238424.29.240.20.011-2011: Power cable lines with a voltage of 110 - 500 kV. Organization of operation and maintenance. Norms and requirements - Terminology STO 70238424.29.240.20.011 2011: Power cable lines with a voltage of 110 500 kV. Organization of operation and maintenance. Norms and requirements: 3.1.1 continuous current load of the cable line: Maximum ... ... Dictionary-reference book of terms of normative and technical documentation

Coaxial transformers (transforming lines, series cable transformers, impedance transformers) sections of coaxial lines with characteristic properties designed to match resistances in microwave ... ... Wikipedia

The maintenance of cable lines (CL) includes revisions, inspections and repairs of equipment, as well as inspections of auxiliary structures. Inspections (rounds) are plannedand extraordinary(or special). Extraordinary inspections are carried out when conditions appear that can cause damage to the lines, as well as after them automatic shutdownseven if their work is not disrupted. Maintenance and repairs are carried out on the basis of long-term, annual and monthly work plans. During audits and inspections, preventive measurements are carried out and minor damages and malfunctions are eliminated.

Maintenance work includes:

Scheduled and extraordinary rounds and inspections of the cable line (the frequency of inspections is given

in table. 4.1);

Installation, replacement and inspection of end funnels and KL couplings;

Measurement of the resistance of wire connections - bolted, die and bolted transitional, as well as the junction of cable cores;

check of KL wells;

Works and measurements related to the verification of the structural elements of the cable line during their acceptance into operation;

Supervision of works carried out near power lines by third parties;

control over the signs indicating the cable line route;

Condition monitoring and replacement of numbering and warning posters;

Control over the temperature regime of cable sheaths.

Table 4.1

Cable lines, especially those laid in the ground, must be protected against corrosion. Although cables have protective anti-corrosion coatings, these coatings degrade over time, which can lead to an accident. Particularly large destructions of cable sheaths occur in soils with low electrical resistance and in places where electrified vehicles operate on direct current. To protect the metal sheaths of cables, cathodic polarization, electrical drainage and tread protection are used.

When different types damage, as well as damage associated with preventive tests with increased voltage, it is necessary to quickly repair cable lines in order to avoid disruption of the normal power supply circuit. Most often, mechanical damage to cable lines occurs during the production of various earthworks due to non-compliance with the requirements of the rules for the protection of electrical networks. Often the reason for the failure of a cable line is the breakdown of couplings and end couplings due to their poor installation.

The insulation of cable lines is tested using special high-voltage rectifiers. The minus from the DC source is fed to the cable core, plus to the ground. The condition of the cable is determined by the leakage current. When the cable is in a satisfactory condition, the leakage current when the voltage rises due to the charging of its capacity increases sharply, then quickly decreases to 10..20% of the maximum. The cable test results are considered satisfactory if no creeping discharges, surges of leakage current or an increase in its steady value were observed, and the insulation resistance, measured by a megohmmeter after the test, remained unchanged. In the presence of defects in the cable, insulation breakdown in most cases occurs within the first minute after applying the test voltage.

In the event of a breakdown of insulation from a core to a metal sheath (single-phase damage), the cables are repaired without cutting them, provided that the insulation is not moistened in excess of the norm. If the cable cores are damaged, this section is cut out, a new segment is inserted and two couplings are mounted.

The main cause of damage to cable glands is installation faults: defects in the soldering of the neck of the coupling or poor soldering of the filling holes, as a result of which the tightness of the coupling is broken; too sharp bend of the cable cores, due to which the paper insulation breaks and the sleeve loses its electrical strength; incorrect or insufficient filling of the coupling with a filling compound; poor-quality soldering of connecting sleeves or a grounding conductor, damage to the belt insulation at its edge, etc.

If the cable line is damaged, it is important to quickly and accurately determine the location of the fault. In this case, it is often possible to limit ourselves to a short cable insertion, since moisture from the soil does not have time to be absorbed into its sheath for a considerable length, and there is no need to carry out a large amount of work to open trenches, since the exact place of damage is known.

In an accident, the nature of the damage is first determined. The following damage is possible in cable lines:

Breakdown or breakdown of insulation, causing one core to short to ground;

Short circuit of two or three cores to the ground;

Closing two or three cores to each other in one place;

The closure of two or three veins among themselves in different places;

Break of one, two or three conductors without grounding;

Breakage of one, two or three conductors with broken ground;

Breakage of one, two or three conductors with unbroken grounding;

Floating breakdown of insulation.

Before starting work to identify the nature of the damage, the cable line is disconnected on both sides, checked for the absence of voltage and discharged by applying grounding to each phase. Most faults are determined by measuring the insulation resistance of each current-carrying conductor of a cable line in relation to earth and between each pair of conductors.

To determine the place of damage to the cable line, at first the damaged zone is very approximately allocated, and then the place for opening the line is specified in it. Relative methods are used to locate the damaged area, and the exact location of the damage is determined by absolute methods. Relative methods include methods: pulsed, oscillatory discharge, loop and capacitive. To absolute - induction and acoustic.

Impulse methodit is based on sending a probing electrical signal to the damaged line and measuring the time interval between the moments of its supply to the line and the return of the reflected pulse. The pulse is reflected from the place of the line break and by the time of the pulse return it is possible to judge the remoteness of the accident site from the place of signal application.

Oscillatory discharge methodbased on the measurement of the period (or half-period) of natural electrical vibrations in the cable that occur at the moment of breakdown of the damaged cable when a test voltage is applied to it. The oscillation period is proportional to the distance to the damage site.

Loop methodbased on measurements of the resistances of the cable cores from both sides using a DC bridge. The difference in readings allows you to determine the location of the damage.

Capacitive methodis based on measuring the capacitance of the broken core parts (between each core part and the sheath) using an AC bridge at a frequency of 1 kHz.

Induction methodbased on capturing the magnetic field above the cable through which the audio frequency current (800 ... 1000 Hz) is passed. Moving along the cable a receiving frame with a steel core, in the circuit of which the headphones are connected through the amplifier, the electrician finds the place of damage by the maximum level of the sound signal.

Acoustic method based on listening to sound vibrations from the surface of the earth, caused by a spark discharge at the site of damage.

Currently, there are many devices and devices for detecting cable line faults, based on the implementation of one or more of these methods.

Monitoring the technical condition of cable lines

The operation of cable lines has its own characteristics, since it is not always possible to detect defects in it by a simple inspection. Therefore, checks of the insulation condition, monitoring of the load and cable temperature are carried out.

Cables are the most difficult piece of electrical equipment in terms of insulation testing. This is due to the possible long length of cable lines, non-uniformity of the soil along the length of the line, and non-uniformity of cable insulation.

To identify gross defects in cable lines, they are produced at a voltage of 2500 V. However, the readings of the megohmmeter cannot serve as a basis for the final insulation condition assessmentas they are highly dependent on cable length and termination defects.

This is due to the fact that the capacity of the power cable is large and during the resistance measurement time it does not have time to fully charge, therefore, the megohmmeter readings will be determined not only by the steady-state leakage current, but also by the charging current, and the measured value of the insulation resistance will be significantly underestimated.

The main method for monitoring the condition of the insulation of a cable line is. The purpose of the tests is to identify and timely eliminate developing defects in cable insulation, couplings and terminations in order to prevent damage during operation. In this case, cables with a voltage of up to 1 kV are not tested with an increased voltage, but the insulation resistance is measured with a megohmmeter with a voltage of 2500 V for 1 min. It must be at least 0.5 MOhm.

Inspection of short cable lines within the same switchgear is performed no more than once a year, since they are less susceptible to mechanical damage and their condition is more often monitored by personnel. The overvoltage test of cable lines exceeding 1 kV is carried out at least once every 3 years.

The main method for testing the insulation of cable lines is check with increased DC voltage... This is because an AC unit has a much higher power under the same conditions.

The test setup includes: transformer, rectifier, voltage regulator, kilovoltmeter, microammeter.

When checking the insulation, the voltage from a megohmmeter or a test setup is applied to one of the cable cores, while the rest of its cores are reliably connected to each other and grounded. The voltage rises smoothly to the specified value and the required time is maintained.

The cable condition is determined by the leakage current. When its condition is satisfactory, the voltage rise is accompanied by a sharp increase in the leakage current due to the charging of the capacitor, then it decreases to 10 - 20% of the maximum value. The cable line is considered suitable for operation if during the tests there was no breakdown or overlap on the surface of the termination, there are no sharp current surges and a noticeable increase in the leakage current.

Systematic cable overloads, lead to deterioration of insulation and a reduction in the duration of the line. Underloads are associated with underutilization of the conductive material. Therefore, during the operation of the cable line, it is periodically checked that the current load in them corresponds to that established when the object was put into operation. The maximum allowable cable loads are determined by requirements.

The load of cable lines is monitored at the time determined by the chief power engineer of the enterprise, but at least 2 times a year. In this case, once the specified control is performed during the autumn-winter maximum load. The control is carried out by observing the readings of ammeters at the supply substations, and in the absence of them - using portable devices or.

Permissible current loads for long-term normal operation of cable lines are determined using tables given in electrical manuals. These loads depend on how the cable is laid and the type of cooling medium (ground, air).

For cables laid in the ground, the long-term permissible load is taken from the calculation of laying one cable in a trench at a depth of 0.7 - 1 m at an earth temperature of 15 ° C. For cables laid outdoors, the ambient temperature is assumed to be 25 ° C. If the calculated ambient temperature differs from the accepted conditions, then a correction factor is introduced.

The highest average monthly temperature of all months of the year at the depth of the cable is taken as the calculated ground temperature.

The calculated air temperature is the highest average daily temperature, which is repeated at least three times a year.

The long-term permissible load of the cable line is determined by the sections of the lines with the worst cooling conditions, if the length of this section is at least 10 m. Cable lines up to 10 kV with a preload factor of no more than 0.6 - 0.8 can be overloaded for a short time. Allowable norms overloads taking into account their duration are given in the technical literature.

For a more accurate determination of the load capacity, as well as when the temperature conditions of operation change, cable line temperature control... It is impossible to directly control the core temperature on a working cable, since the cores are energized. Therefore, at the same time, the temperature of the sheath (armor) of the cable and the load current are measured, and then the temperature of the core and the maximum permissible current load are determined by recalculation.

Measurement of the temperature of the metal sheaths of a cable laid openly is carried out with conventional thermometers, which are attached to the armor or lead sheath of the cable. If the cable is buried, the measurement is made with thermocouples. It is recommended to install at least two sensors. The wires from the thermocouples are placed in the pipe and led out to a convenient and safe place from mechanical damage.

The conductor temperature should not exceed:

for cables with paper insulation up to 1 kV - 80 ° С, up to 10 kV - 60 ° С;

for cables with rubber insulation - 65 ° С;

for cables in PVC sheath - 65 ° C.

In the event that the cable conductors heat up above the permissible temperature, measures are taken to eliminate overheating - they reduce the load, improve ventilation, replace the cable with a cable of a larger cross-section, increase the distance between the cables.

When cable lines are laid in soil that is aggressive towards their metal sheaths (salt marshes, swamps, construction waste), soil corrosion of lead shells and metal sheaths... In such cases, periodically check corrosive activity soil, taking samples of water and soil. If at the same time it is established that the degree of soil corrosion threatens the integrity of the cable, then appropriate measures are taken - eliminate pollution, replace the soil, etc.

Determination of places of damage to a cable line

Determining the locations of damage to cable lines is a rather difficult task and requires the use of special equipment. Work to eliminate damage to the cable line begins with establishing the type of damage... In many cases, this can be done using a megohmmeter. For this purpose, from both ends of the cable check the state of the insulation of each core in relation to the ground, the serviceability of the insulation between the individual phases, and the absence of breaks in the cores.

Determination of the location of damage is usually carried out in two stages - first, the damage zone is determined with an accuracy of 10 - 40 m, and then the location of the defect on the track is specified.

When determining the zone of damage, the causes of its occurrence and the consequences of failure are taken into account. The most often observed breakage of one or several conductors with or without grounding, it is also possible to weld a current-carrying conductor with a sheath with a long-term flow of a short-circuit current to the ground. During preventive tests, a short-circuit of a current-carrying conductor to ground, as well as a floating breakdown, most often occurs.

To determine the damage zone, several methods are used: pulse, oscillatory discharge, loop, capacitive.

Impulse method it is used for single-phase and phase-to-phase faults, as well as for wire breaks. The method of oscillatory discharge is resorted to with a floating breakdown (occurs at a high voltage, disappears at a low voltage). The loopback method is used with one-, two- and three-phase faults and the presence of at least one intact core. The capacitive method is used for wire breakage. In the practice of operation, the first two methods are most widespread.

When using the impulse method, enough simple appliances... To determine the zone of damage from them, short-term pulses of alternating current are sent to the cable. Having reached the place of damage, they are reflected and returned back. The nature of the cable damage is judged by the image on the device screen. The distance to the site of damage can be determined by knowing the travel time of the pulse and the speed of its propagation.

The use of the impulse method requires a reduction in the contact resistance at the point of damage to tens or even fractions of an ohm. For this purpose, the insulation is burned through by converting electrical energy supplied to the place of damage into heat. Burning is carried out permanently or alternating current from special installations.

Oscillatory discharge method consists in the fact that the damaged core of the cable is charged from the rectifier to the breakdown voltage. At the moment of breakdown, an oscillatory process occurs in the cable. The period of oscillation of this discharge corresponds to the time of the double travel of the wave to the place of damage and back.

The duration of the oscillatory discharge is measured with an oscilloscope or electronic millisecond watch. The measurement error by this method is 5%.

Clarify the location of cable damage directly on the route using an acoustic or induction method.

Acoustic method based on the fixation of ground vibrations above the place of damage to the cable line, caused by a spark discharge at the place of insulation failure. The method is used for damages such as "floating breakdown" and wire breakage. In this case, damage is determined in a cable located at a depth of 3 m and under water up to 6 m.

The pulse generator is usually a high voltage DC installation, from which pulses are sent to the cable. Ground vibrations are monitored with a special device. The disadvantage of this method is the need to use mobile DC installations.

Induction method finding places of cable damage is based on fixing the nature of changes in the electromagnetic field above the cable through the conductors of which current is passed high frequency... The operator, moving along the track and using a loop antenna, amplifier and headphones, determines the location of the damage. The accuracy of determining the location of the damage is quite high and amounts to 0.5 m. The same method can be used to establish the route of the cable line and the depth of the cables.

Repair of cables

Repair of cable lines is carried out according to the results of inspections and tests. A feature of the work is the fact that the cables to be repaired can be energized, and in addition, they can be located close to live cables that are energized. Therefore, personal safety must be observed, do not damage nearby cables.

Repair of cable lines can be associated with excavations. In order to avoid damage to nearby cables and utilities, at a depth of more than 0.4 m, excavation is carried out only with a shovel. If any cables or underground utilities are found, work is stopped and the person responsible for the work is notified. After opening, care must be taken not to damage the cable and couplings. For this purpose, a solid board is placed under it.

The main types of work in case of damage to the cable line are: repair of armor cover, repair of casings, couplings and end fittings.

If there are local breaks in the armor, the ends are cut off at the site of the defect, soldered with a lead sheath and covered with an anti-corrosion coating (bitumen-based varnish).

When repairing a lead sheath, the possibility of moisture penetration into the cable is taken into account. To check, the damaged area is immersed in paraffin heated to 150 ° C. In the presence of moisture, the dive will be accompanied by crackling and yen release. If the fact of the presence of moisture is established, then the damaged area is cut out and two couplings are mounted, otherwise the lead sheath is restored by placing a cut lead pipe on the damaged area and then sealing it.

For cables up to 1 kV, cast iron couplings were previously used. They are bulky, expensive, and insufficiently reliable. Epoxy and lead couplings are mainly used on 6 and 10 kV cable lines. Currently, when repairing cable lines, they are actively using modern heat-shrinkable couplings... There is a well-developed technology for installing cable glands. The work is carried out by qualified and trained personnel.

Terminals are classified into indoor and outdoor types. Indoors, dry cutting is more often done, it is more reliable and convenient to use. Outdoor end couplings are made in the form of a funnel made of roofing iron and filled with mastic. When carrying out routine repairs, the condition of the end funnel is checked, there is no leakage of the filling compound, and it is refilled.

Repair work of cable communication lines.

- previous mechanical damage - 43%;
- direct mechanical damage by construction and other organizations - 16%;
- defects in couplings and end fittings during installation - 10%;
- damage to cables and couplings as a result of soil settlement - 8%;
- corrosion of metal sheaths of cables -7%;
- cable manufacturing defects at the plant - 5%;
- violations during cable laying - 3%;
- aging of insulation due to long-term operation or overloads - 1%;
- other and unidentified reasons - 7%.
Repairs of cable lines are simple, not requiring large labor costs and time, and complex, when the repair takes several days.
Simple repairs include, for example, such as repairs of outer covers (jute cover, PVC hose), painting and repair of armored tapes, repair of metal casings, repair of end fittings without dismantling the body, etc. The listed repairs are performed in one shift by one team ( link).
Repairs are complicated in most cases by the fact that the cable route passes through difficult sections with many turns, with the intersection of highways and utilities, with a great depth of the cable, as well as in winter, when it is necessary to warm the ground.
In my graduate work, I considered the repair of power cables.

Maintenance of cable communication lines

The maintenance of cable communication lines includes maintenance and repair.
Maintenance is divided into routine (daily and periodic) and planned preventive.
With routine and scheduled preventive maintenance, the following is carried out:
- technical supervision of the state of the track and the implementation of the rules for the protection of national communications;
- technical supervision of all structures and the operation of automation, signaling and telemechanics devices;
- carrying out preventive work;
- control over the electrical characteristics of the cable;
- elimination of identified faults;
- provision of an emergency supply of cables, fittings and materials (including lightweight cables) to quickly eliminate damage on the line;
- maintenance of mechanisms, vehicles, devices, devices, tools and overalls necessary for carrying out planned preventive and emergency recovery work in good and efficient condition;
- elimination of accidents and damages;
- Carrying out security and explanatory work;
- installation of warning signs;
- preparation of linear structures for work in winter conditions and during floods;
- maintenance of technical records;
- prevention of damage associated with the performance of work on blasting ice, excavation of soil, cleaning the bottom of reservoirs, construction of structures in the area of \u200b\u200bthe cable line.
When carrying out technical supervision during operation, it is necessary:
- notify local authorities, authorities, organizations, enterprises, collective farms, state farms and construction sites, on the territory or near which the route passes, about the place of laying the cable and the need for them to comply with the rules for the safety of national communications;
- to carry out explanatory work among the population, workers of construction and other organizations and enterprises located along the cable line route, on the observance of safety measures when working in the security zone of the cable;
- hand over notifications to the relevant organizations and individuals about the passage of underground cables with a warning about responsibility for the safety of the cable during work;
- to install warning signs at the points of convergence of the cable with other above-ground and underground structures and in the areas of expected construction work;
- to carry out continuous supervision in the places of excavation and other works in the security zone of the cable and take measures to protect it from damage;
- to prevent landslides and erosion of soil along the cable route;
- monitor the condition of the measuring posts, signal and warning signs, instrumentation and other devices and eliminate the noticed deficiencies.
The operational personnel of the GTS is obliged to periodically inspect the sewer and cable structures and monitor their safety and serviceability, and, if necessary, eliminate the appeared
damage.

Maintenance of line-cable communication facilitiesCustomers include maintenance of fiber-optic communication cables and copper cables. The MAIN task of maintenance of linear communication facilities is to maintain them in a state of complete serviceability and readiness for use, as well as timely identification of emergency and damaged areas. The maintenance process of line-cable communication facilities is to carry out control measurements of the parameters of fiber-optic and copper cables, an external visual inspection of the laid cables for the detection of external damage and violation of the rules for laying cables in the sewer and along structures. Control measurements at line-cable communication facilities are carried out in accordance with the plans and schedules approved by the Customer (if necessary, in the presence of his representative). Based on the results of the measurements performed, Acts of Completed Work are drawn up, in which the measurement object, cables suitable for further operation and cables requiring repair are indicated, documentation is transferred based on the measurement results.

REPAIR OF CABLE AND CABLE LINES

1. GENERAL INSTRUCTIONS FOR CABLE REPAIR

During the operation of cable lines, for certain reasons, cables, as well as couplings and terminations fail.

The main causes of damage to cable lines with a voltage of 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 fittings during installation - 10%.

4. Damage to cables and couplings as a result of soil settlement - 8%.

5. Corrosion of metal sheaths of cables - 7%.

6. Defects of cable manufacture at the factory - 5%.

7. Violations during cable laying - 3%.

8. Aging of insulation due to long-term operation or overloads - 1%.

9. Other and unidentified reasons - 7%.

The average data for the last ten years in the Moscow cable network are given.

In accordance with the requirements of the "Instructions for the operation of power cable lines. H 1. Cable lines with voltage up to 35 kV "each cable line must undergo current or major repairs.

Current repairs 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 umbilical cables, or when the backup line to which the load is transferred is unacceptably overloaded and no possibility of further unloading or restriction of consumers is required.

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

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

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 them to overload or limit consumers. The urgent repair of cable lines is started by repair crews at the direction of the management of the energy service during the working shift.

Scheduled repair is the repair of all cable lines not mentioned above, which is carried out according to a schedule approved by the management of the energy service. The repair schedule for cable lines is drawn up on a monthly basis on the basis of entries in the walk and inspection logs, test and measurement results, as well as on the basis of dispatch services.

Overhaul of cable lines is carried out according to an annual plan developed annually in the summer for the next year based on operating data.

When drawing up a plan for overhaul, 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, devices for pumping water The need for partial replacement of cables in certain sections that limit the throughput of lines or do not meet the requirements of thermal resistance in changed network operating conditions with increased currents is also taken into account short circuit

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 operated cable lines, the following work is performed

preparatory - disconnecting the cable line and grounding it, reviewing the documentation and clarifying the brand and section of the cable, issuing a safety permit, loading materials and tools, delivering the team to the place of work;

preparation of the workplace - execution of pits, excavation of pits and trenches, determination of the cable to be repaired, fencing of the workplace and excavation sites, determination of the cable in the RP (TP) or in cable structures, checking the absence of flammable and explosive gases, obtaining a permit for hot work;

preparation for installation - team clearance, cable puncture, cutting the cable or opening the sleeve, checking the insulation for moisture, cutting off damaged cable sections, setting up a tent; laying of a repair cable insert;

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

registration of the completion of work - closing the doors of switchgear, transformer substations, cable structures, handing over the keys, filling pits and trenches, cleaning and loading tools, delivering the team to the base, drawing up an executive sketch and making changes to the documentation of the cable line, report on the completion of repairs;

measurements and tests of the cable line.

In order to speed up repair work on cable lines, mechanization should be widely used when performing earthwork: pneumatic jackhammers, electric hammers, concrete breakers, excavators, means for warming frozen soil.

Special mobile cable workshops are used to transport repair crews

Repairs of cable lines are simple, they do not require much labor and time, and difficult, when the repair takes several days.

Simple repairs include, for example, repairs of outer covers (jute cover, PVC hose), painting and repair of armor tapes, repair of metal casings, repair of end seals without dismantling the body, etc. The above repairs are carried out in one shift by one team (link).

Complex repairs include such repairs when it is necessary to replace long cable lengths in cable structures with preliminary dismantling of a cable that has gone out of operation 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 difficult sections with many turns, with the intersection of highways and utilities, with a large depth of the cable, as well as 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 COATS

Repair of outdoor jute cover. A cable stretched through pipes, blocks or other obstacles, having stripped impregnated cable yarn and the rest of the outer covers to the steel armor, must be restored.Repair is carried out by winding up with a resin tape in two layers with 50% overlap, followed by smearing this area with heated bitumen mastic MB 70 ( MB 90).

Repair of PVC hose and jackets. The first way to repair a PVC hose or sheaths is welding, which is carried out in a stream of hot air (at a temperature of 170-200 ° C) using a welding gun with electric heating of air (Figure 1) or a gas-air gun (Figure 2) Compressed air is supplied by pressure 0.98-104 Pa from a compressor, a compressed air cylinder, a portable unit with a hand pump.

Fig 1. Welding gun PS-1 with electric heating: - nozzle for hot air outlet, 2 - heating air chamber; 3 - connection for compressed air supply, 4 - electric wire

As an additive for welding, a polyvinyl chloride rod with a diameter of 4-6 mm is used.

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

To repair punctures of small holes and cavities, the place of damage in the hose or sheath and the end of the filler rod are heated for 10-15 s with a stream of hot air, then the stream is diverted, and the end of the rod is pressed and welded to the hose at the place of heating. After cooling, making sure of the strength of the welding of the bar by slightly twitching it, the bar is cut off.

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

To repair a hose or a sheath that has slots, slots and cutouts, the end of the filler rod is welded to the entire place of the hose at a distance of 1-2 mm from the damage site.

After making sure of the strength of the welding, 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 lightly pressing on the bar, the latter is laid and welded along the gap or slot. Welding of the bar is finished in the whole place at a distance of 1--2 mm from the damage. Then the protruding surfaces of the bar are cut with a knife and the welded seam is aligned.

Tears in the hose or jacket are repaired with PVC patches or cut cuffs.

The patch is made of plastic so that its edges overlap the gap by 1.5-2 mm. The patch along the entire perimeter is welded to the hose, and then along the formed seam, the filler rod is welded, and the protruding surfaces of the rod are cut off and the seam is aligned at the weld point.

To repair a hose or sheath using a split cuff, cut a piece of polyvinyl chloride tube 35-40 mm longer than the length of the damaged area, cut the tube lengthwise and put on its cable symmetrically to the site of damage. The cuff is temporarily fixed with polyvinyl chloride or calico tape with a pitch of 20-25 mm, the end of the bar is welded at the junction of the cuff with the hose (sheath), and then the bar is laid and welded around the end of the cuff. After welding both ends of the cuff to the hose (sheath), the temporary fastening tapes are removed, the bar is welded along the cuff cut, the protruding surfaces of the bar are cut off, and all welds are finally aligned.

According to the second method, the repair of PVC hoses and cable sheaths can be performed using an epoxy compound and glass tape. The surface of the hose or sheath is pre-treated as described above and is additionally roughened with a broom file. The place of damage and behind 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. Over the layer of epoxy compound, four to five layers of glass tape are applied, each of which is also coated with a layer of compound.

Temporary repairs to hoses and jackets to prevent

moisture penetration under the cable sheath, as well as to prevent the bitumen composition from flowing out from under the hose, it is allowed to perform using adhesive polyvinyl chloride tape with 50% overlap in three layers with the top layer coated with polyvinyl chloride varnish No. 1. According to the second method, temporary repairs are performed with LETSAR tape in three layers with 50% overlap.

Painting of armor tapes. If, during bypasses in cable structures on openly laid cables, the destruction of the armor covers of the cable by corrosion is detected, 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 with a spray gun or, if not, a brush.

Repair of armor tapes. On openly laid cables, the detected sections of destroyed armor tapes are cut off and removed. Temporary bandages are made in the places of the cut off tapes. Next to the temporary bandages, both tapes are thoroughly cleaned to a metallic sheen and served with POSSu 30-2 solder, after which the ground wire is fastened with bands of galvanized wire 1-1.4 mm in diameter 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.

For tinning and soldering the armor tape, soldering fat is used. The duration of each soldering should be no more than 3 minutes. The temporary bandages are removed. An anti-corrosion coating is applied to the bare section of the shell.

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

3. REPAIR OF METAL SHELLS

In case of 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 upper layer of belt insulation is removed and checked for moisture in heated paraffin.

In the event that there is no moisture and the insulation is not destroyed, the lead or aluminum shell is repaired.

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

The removed semi-conductive layer of paper and the top tape of the belt insulation are restored and secured with cotton thread bands. The section is pierced with cable mass MP-1.

A strip of lead is wrapped around the bare part of the cable so that it goes evenly onto the edges of the cable sheath, and the edges of the lead pipe formed overlap 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 at the soldering point of the lead pipe, the cable sheath is served with grade A solder. The sleeve is filled with MP-1 hot cable mass. After cooling and refilling, the filling holes are sealed. A copper wire bandage with a diameter of 1 mm with a 10 mm outlet to the cable sheath is applied to the place sealed at the ends and 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 insulation of the cores, the cable section is cut out to 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 couplings are installed. The cable cross-section and voltage must correspond to the cut-out section.

A different brand of cable for insertion can be used, but its design is similar to the cut out section.

4 RESTORING THE PAPER CABLE INSULATION

In cases where the conductive cores are not damaged, and the core insulation and belt insulation are damaged, but there is no moisture in it, the insulation is restored followed by the installation of the split lead coupling.

The cable is excavated to such a length that sufficient slack in the cable can be created to separate the conductors between themselves. After the veins have been separated and the old insulation removed, the conductor insulation is restored by applying paper rollers or LETSAR tape with preliminary treatment with MP-1 scalding mass. A split lead sleeve is installed and the longitudinal seam is first soldered, and then the sleeve is soldered to the cable sheath.

The specified repairs can be performed on horizontal sections of cable routes, where there is no increased oil pressure, since the longitudinal soldering sleeve has a lower mechanical strength.

5. REPAIR OF THE CURRENT CONDUCTORS OF THE CABLE

If the cable cores are broken at a short length and the cable can be tightened due to the "snake" made during the laying, the usual repair of the connecting lead or epoxy joint is performed. If there is no supply of cable, elongated connecting sleeves and sleeves can be used. In this case, the repair 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 connecting couplings are installed.

6. REPAIR OF CONNECTING COUPLINGS

The need to repair the coupling or the installation of a cable insert and two couplings is established after inspecting the coupling and disassembling it.

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

If a breakdown occurs in the neck of the sleeve from the core to the edge of the shell and the insulation is not moistened, the sleeve is disassembled. Then a section of the armor and shell is cut off to the length necessary for convenient breeding of the veins. The insulation of the damaged core is restored, and the repair is performed. The elongated split body of the lead coupling is installed, and all operations for mounting the coupling are performed.

If it is impossible to make an extended sleeve due to large destruction, then a cable insert is used with the installation of two sleeves according to the technology provided for in the technical documentation.

In most cases, damage to couplings occurs during preventive overvoltage tests. And if the repair is not started immediately after determining the location of the damage, moisture begins to flow into the clutch. In this case, the damaged coupling is repaired by cutting out the defective coupling and cable sections. As a rule, the more the damaged and not repaired joint lies in the ground, the longer it is necessary to insert the cable for restoration when repairing the cable line.

7. REPAIR OF OUTDOOR END COUPLINGS

Outdoor terminations in most cases go out of service during rainy periods of the year or when the relative humidity is high and, as a rule, have large defects and damage inside the coupling. Therefore, the damaged sleeve is cut off, the cable insulation is checked for moisture, and, if the paper insulation is not moistened, the sleeve is installed in accordance with the requirements of the technical documentation. If the length of the cable at the end of the line has a sufficient margin, then the repair is limited to the installation of only the termination. If there is not enough supply of cable, then the cable of the required length is inserted at the end of the cable line. In this case, it is necessary to mount the coupling and end sleeves.

Disassembled couplings can be used for re-assembly. But for this it is necessary to clean the body and all parts of the coupling from soot, rinse them with gasoline and dry them.

In outdoor end couplings with a metal body, once a year, during the entire operation period, check the seals and tighten the nuts. Simultaneously examine contact connections and if necessary, clean the contact surfaces and tighten the bolts.

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

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

Outer and outer end sleeve insulators indoor installationsand the insulating surfaces of the end fittings must be periodically cleaned of dust and dirt with a lint-free cloth] and soaked in gasoline or acetone. More frequent cleaning must be done on cable end fittings in workshops industrial enterprises and areas with conductive dust

The frequency of wiping and cleaning of cable end fittings on a given electrical installation is established chief Engineer local energy company.

8. REPAIR OF END BARS

In the event of the destruction of the termination body and the burnout of the cores in the spine, the repair of the terminations is carried out in the same way as the repair of the end couplings, except that the termination body and parts cannot be reused.

Repair of end fittings in steel funnels in case of destruction of core insulation is carried out in the following sequence - destroyed core insulation or deteriorated (contamination, moisture) is removed from the cores, one layer of paper insulation is wound, five layers are wound with 50% overlap of sticky polyvinyl chloride tape or three layers of rubberized tape followed by coating with insulating tapes or paints. Instead of the indicated tapes, the repair can be carried out using LETSAR tape (two layers) and PVC tape (one layer).

In case of cracking, peeling, partial leaving and significant contamination of the casting compound, especially when these defects are accompanied by a noticeable displacement of the cores between themselves or towards the funnel body (which may in turn be caused by an incorrect position or absence of a spacer plate), a complete re-pouring of the steel funnel should be done.

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

The mouth of the funnel is wound with resin tape and the funnel together with the cable is fastened to the support 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 end seals made of polyvinyl chloride tapes is carried out in the presence of an impregnating compound in the spine or on the veins, in case of cracking and breaks of the tapes.

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

Repair of epoxy end seals in case of destruction of windings on the veins is carried out with the dismantling of old tapes, restoration of new LETSAR tapes and additional pouring of epoxy compound so that the tapes go into the cast compound by at least 15 mm.

If the impregnating compound leaks through the cable in the spine of the seal, the lower part of the seal is degreased in a section of 40-50 mm and at the same distance a section of armor or sheath (for non-armored cables). A two-layer winding of cotton tape lubricated with epoxy compound is applied to the degreased 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.

Figure: 3. Installation of a repair form to eliminate leaks of the impregnating compound at the point where the cable enters the termination body:

1 - termination body, 2 - repair form; 3 - place of leak

Figure: 4. Installation of a repair form to eliminate the leak at the point where the conductors exit from the termination body:

1 - repair form; 2 - place of leak, 3 - sealing body

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

If the tightness on the veins is broken, the defective section of the tube or core winding is degreased and a repair one is applied.

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

If the tightness is broken at the place where the tube adjoins or winding to the cylindrical part of the tip, the surface of the band and a section of the tube or winding of the core with a length of 30 mm are degreased. On the fat-free areas, a two-layer winding of cotton tapes with abundant compounding of each winding loop is applied. On top of the reel, a tight bandage of twisted twine is applied and also coated with epoxy compound.