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Maintenance of switchgears. Organization of an electrician's workplace: characteristics, safety requirements, instruction

Maintenance of switchgears. Organization of an electrician's workplace: characteristics, safety requirements, instruction

One of the main tasks of operating switchgears is maintaining the necessary reserves for dynamic and thermal stability, throughput, and voltage levels in the device as a whole and in its individual elements. These tasks can be achieved with proper maintenance. distribution devices. During maintenance, switchgear devices are inspected, and during routine repairs, noticed faults that require disassembling the equipment are eliminated. Current repairs are carried out at the installation site of the equipment, while faulty parts are replaced, and after their replacement, switchgear devices are adjusted and tested.

Frequency of inspections of switchgears. The frequency of inspection is determined depending on the type of device, its purpose and form of maintenance. Approximate inspection times are as follows:

in switchgears serviced by shift personnel on duty at the substation itself or at home - daily. In case of unfavorable weather (wet snow, fog, heavy and prolonged rain, ice, etc.), as well as after short circuits and when a signal about a ground fault appears in the network, additional inspections are carried out. It is recommended to inspect the device in the dark once a week to identify possible corona discharges in areas of insulation damage and heating of live parts;

in switchgear substations with voltages of 35 kV and above that do not have permanent personnel on duty, the inspection schedule is drawn up depending on the type of device (closed or open) and the purpose of the substation. In this case, inspections are performed by the head of the substation group or a foreman at least once a month;

transformer substations and distribution devices of electrical networks with a voltage of 10 kV and below that do not have

duty personnel are examined at least once every six months;

extraordinary inspections at facilities without permanent personnel on duty are carried out within the time limits established by local instructions, taking into account the short circuit power and the condition of the equipment. In all cases, regardless of the value of the short circuit interrupted power, the circuit breaker is inspected after a cycle of unsuccessful automatic reclosing (AR) and tripping due to a short circuit.

All faults noticed during inspections of switchgears are recorded in the operational log. Faults that interfere with normal operation must be corrected the shortest possible time. The serviceability of backup elements of switchgear devices (transformers, switches, busbars, etc.) must be regularly checked, including them under voltage within the time limits established by local instructions. Backup equipment must be ready to be turned on at any time without any prior preparation. The frequency of cleaning switchgears from dust and dirt depends on local conditions. It is installed by the chief engineer of the enterprise.

Switch maintenance. External inspections of oil switches without shutdown are carried out taking into account local conditions, but at least once every six months, together with inspections of the switchgear. During inspections, the following is checked: the condition of the insulators, fastenings and contacts of the busbar, the oil level and the condition of the oil indicators; no oil leakage from the grid contacts of low-volume switches or through the gaskets of tank switches. The oil level of switches largely determines the reliability of their operation. It should not go beyond the oil gauge at temperatures environment from -40" to +40 °C. Increased level oil in the poles and a correspondingly reduced volume of the air cushion above the oil lead to excessive pressure in the tank when the arc is extinguished, which can cause destruction of the circuit breaker.

A decrease in oil volume also leads to destruction of the switch. It is especially dangerous in small-volume circuit breakers VMG-10, VMP-10. If the leak is significant and there is no oil in the oil sight glass, then the switch is repaired and the oil in it is replaced. In this case, the load current is interrupted by another switch or the load at this connection is reduced to zero. Abnormal heating of the arcing contacts of small-volume switches causes darkening and a rise in the oil level in the oil indicator glass, as well as a characteristic odor. If the temperature of the circuit breaker tank exceeds 70 °C, the circuit breaker should be repaired.

In areas with a minimum temperature below 20 °C, switches are equipped with automatic devices for heating the oil in the tanks. It is recommended to check the circuit breaker drives at least once every three (six) months. In the presence of automatic reclosure, testing for shutdown is advisable to carry out from relay protection with shutdown from automatic reclosure. If the switch fails to operate, it must be repaired.

During an external inspection of air circuit breakers, attention is paid to its general condition, the integrity of the insulators of the suppression chambers, separators, shunt resistors and capacitive voltage dividers of the support columns and insulating braces, as well as the absence of contamination of the surface of the insulators. Using pressure gauges installed in the distribution cabinet, the air pressure in the tanks of the circuit breaker and its supply to the ventilation are checked (for circuit breakers operating with automatic reclosure, the pressure should be in the range of 1.9...2.1 MPa and for circuit breakers without automatic reclosure - 1, 6...2.1 MPa). The switch control circuit provides an interlock that prevents the switch from operating when the air pressure drops below normal.

During the inspection, they also check the serviceability and correctness of the readings of devices signaling the on or off position of the switch. Pay attention to whether the dampers of the exhaust visors of the extinguishing chambers are securely closed. Visually check the integrity of the rubber gaskets in the connections of the insulators of the extinguishing chambers, separators and their support columns. They control the degree of heating of bus contact connections and hardware connections. When operating air circuit breakers, accumulated condensate is removed from the tanks 1-2 times a month. During the rainy season, the air supply for ventilation increases; when the ambient temperature drops below minus 5 °C, electric heating is turned on in control cabinets and distribution cabinets. At least twice a year, the functionality of the circuit breaker is checked by means of control tests for turning off and turning on. To prevent damage to the switches, check and tighten the bolts of all sealing connections 2 times a year (in spring and autumn).

Maintenance of complete switchgears. The operation of complete switchgears (SGD) has its own characteristics due to the limited overall dimensions of the cells. To protect personnel from accidental contact with live parts that are energized, the switchgear is provided with a lock. In stationary switchgear, screen doors are blocked, which are opened only after the circuit breaker and connection disconnectors are turned off. The withdrawable switchgear has automatic shutters that block access to the compartment of fixed disconnecting contacts when the trolley is rolled out. In addition, there is an operational lock that protects personnel when performing erroneous operations. For example, rolling out the trolley into the test position is permitted by blocking only after the circuit breaker is turned off, and rolling the trolley into the working position is allowed when the circuit breaker and grounding knives are turned off. Equipment is monitored through observation windows and mesh fences or inspection hatches covered with a protective mesh.

Inspections of switchgear without shutting them down are carried out according to schedule, but at least once a month. During inspections, the operation of lighting and heating networks and switchgear cabinets is checked; condition of switches, drives, disconnectors, primary disconnecting contacts, locking mechanisms; contamination and absence of visible damage to the insulators; state of secondary switching circuits; operation of switch control buttons. Systematically, depending on local conditions, clean the insulation from dust and contamination, especially in outdoor switchgear (KRUN). When inspecting complete switchgear devices KRU and KRUN, pay attention to the condition of the seals at the joints of metal structure elements; serviceability of equipment connection to the ground loop; availability of safety and fire extinguishing equipment; operation and serviceability of heating devices for KRUN cabinets; presence, sufficiency and normal color of oil in switches; condition of installation connections; heating of live parts and devices; absence of extraneous noise and odors; serviceability of alarms, lighting and ventilation. Simultaneously with the inspection, the correct position of the switching devices is checked. The equipment built into switchgear and switchgear switchgear is inspected in accordance with the operating instructions.

When operating the switchgear, it is prohibited to unscrew the removable parts of the cabinet, lift or open automatic curtains if there is voltage in those places to which access is blocked by them. In withdrawable-type switchgear cabinets, to ground outgoing lines using disconnectors built into the switchgear, you need to do the following: turn off the switch, roll out the trolley, check the absence of voltage on the lower disconnecting contacts, turn on the grounding switch, put the trolley in the test position.

The fuses in the auxiliary transformer cabinet can only be changed when the load is removed. When carrying out work inside the compartment of a roll-out cart on an automatic curtain, it is necessary to hang warning posters: “Do not turn on! People are working", "High voltage! Life threatening!" Only trained operating personnel can roll out the trolley with the switch and install it into the operating position.

It is allowed to roll the trolley into the working position only when the grounding switch is in the open position.

Maintenance of disconnectors. When adjusting the mechanical part of three-pole disconnectors, check the simultaneous activation of the knives. When adjusting the moment of contact and compression of the movable knives, they change the length of the thrust or stroke of the limiters and thrust washers, or slightly move the insulator on the base or the jaws on the insulator. When fully switched on, the knife should not reach the contact pad stop by 3-5 mm. The minimum force of pulling one knife from a fixed contact should be 200 N for disconnectors with rated currents of 400...600 A and 400 N for disconnectors with rated currents of 1000...2000 A. The tightness of the contacts of the disconnector is controlled by resistance DC, which must be within the following limits: for RLND disconnectors (35...220 kV) for a rated current of 600 A - 220 μOhm; for other types of disconnectors for all voltages with a rated current of 600 A - 175 μOhm, 100 A - 120 μOhm; 1500-2000 A - 50 μOhm.

During operation, the contact surfaces of the disconnectors are lubricated with neutral petroleum jelly mixed with graphite. The rubbing parts of the drive are coated with antifreeze lubricant. The condition of disconnector insulators is assessed by insulation resistance, voltage distribution on the steel elements of pin insulators or by the results of testing the insulator with increased power frequency voltage.

The drive block contacts, intended for signaling and blocking the position of the disconnector, must be installed so that the signal to turn off the disconnector begins to operate after the knife has passed 75% of the full stroke, and the signal to turn on - no earlier than the moment the knife touches the fixed contacts.

Maintenance of short circuiters and separators. Short circuiters are devices designed to artificially create a short circuit in cases where the current in the event of a fault in the transformer may be insufficient to trigger the relay protection. The short-circuiter is switched on automatically by an automatic drive when the relay protection is triggered, and is switched off manually.

When disconnecting power transformers without load, as well as automatically disconnecting damaged transformers, separators are used. The separator can be turned off automatically or manually; it can only be turned on manually using a removable handle. At 35...11O kV connections with separators and disconnectors installed in series, switching off the magnetizing current of transformers and capacitive currents of the line should be carried out by separators. Separators rated at 35 kV allow disconnection of ground fault current up to 5 A.

On average, for 10 km of a 35 kV overhead line, the charging current is 0.6 A and the ground fault current is 1 A.

Short circuits and separators are inspected at least 2 times a year, as well as after emergency shutdowns. During inspections, special attention is paid to the condition of insulators, contacts, and the grounding wire passed through the window of the current transformer. If traces of burning are detected, the contacts are cleaned or replaced. The duration of movement of the moving parts of a short-circuiter for voltages of 35 and 110 kV from the application of a pulse to closing the contacts should be no more than 0.4 s, and the duration of movement of the separator from the application of a pulse to the opening of the contacts should be 0.5 and 0.7 s, respectively.

During the operation of short circuiters and separators, special attention should be paid to the most unreliable components: open or insufficiently protected from possible contamination and icing springs, contact systems and hinge joints, as well as unprotected bearings protruding from the rear side.

When setting up the short circuit and separator, pay attention to the reliable operation of the separator blocking relay (BRO), which is designed for currents of 500...800 A. Therefore, with short circuit currents less than 500 A, the grounding bus should be replaced with a wire and passed through the current transformer several times . If this is not done, the BRO relay will tighten the armature indistinctly and thereby release the locking mechanism of the separator drive until the short circuit current is turned off. Premature shutdown of separators is one of the reasons for their destruction.

Current repairs of disconnecting devices, as well as checking their operation (testing), are carried out as necessary within the time limits established by the chief engineer of the enterprises. The scope of work on current repairs includes: external inspection, cleaning, lubrication of rubbing parts and measurement of contact resistance to direct current. Unscheduled repairs are carried out in the event of detection of external defects, heating of contacts or unsatisfactory insulation conditions. Adjustment of the short-circuiter and separator consists of checking the operation of the drive for turning on and off, checking the position of the knives and the installation of the tripping spring of the drive with the BRO blocking relay, adjusting the stroke of the electromagnet and relay cores.

Monitoring the condition of live parts and contact connections. The condition of live parts and contact connections of busbars and switchgear devices is checked during inspections. The heating of detachable connections in closed distribution devices is controlled using electric thermometers or thermal candles and temperature indicators. The operation of an electric thermometer is based on the principle of measuring temperature using a thermistor glued to the outer surface of the sensor head and covered with copper foil. The heating temperature of contact connections is determined using a set of thermal candles with different melting temperatures. Reversible, reusable films are used as thermal indicators, which change color when heated for a long time. The thermal indicator must withstand, without destruction, at least 100 color changes during prolonged heating to a temperature of 110 °C.

Maintenance of grounding devices. During operation, inspections, periodic checks and tests of grounding devices are performed in accordance with the recommendations of the PPR.

In areas of grounding devices subject to intense corrosion, more frequent measurement intervals are established. Unscheduled measurements of the resistance of grounding devices are carried out after their reconstruction or major repairs. The resistance of grounding devices is measured with special devices MS-08, M-416, F4103 or by the ammeter-voltmeter method. Schematic diagrams for switching on the MS-08, M-416, F4103 devices are shown on the covers of the devices or in the instructions. Metal rods with a diameter of 12...16 mm are used as auxiliary grounding conductors, which are driven into the ground to a depth of 0.5 m at a distance specified in the instructions.

SCHEMETECHNOLOGICALREPAIR PROCESSTRANSFORMER

The most vulnerable and often damaged part of a transformer is its HV and, less commonly, LV windings. Damage most often occurs due to a decrease in the electrical strength of the insulation on any section of the winding.

In transformers, bushings, switches, covers and other parts may also be damaged. The approximate ratio of damage to individual parts of the transformer is as follows:

windings and conductive parts - 53%;

switches -12%;

all other parts taken together - 17%.

Studies of the causes of emergency transformer failures have shown that accidents usually occur due to unsatisfactory maintenance and poor quality of repairs.

A transformer with damaged windings or other parts must be immediately taken out of service and repaired. The enterprise draws up an acceptance certificate with a list of defects attached and places an order. The documents record the order number, passport data, customer requirements, results of external inspection, verification tests and measurements. All defects discovered during the further process of disassembling the transformer are also recorded in the list of defects. Based on these data, the volume is determined repair work.

The most common process flow diagram for repairing three-phase oil-cooled transformers in electrical repair shops of most enterprises is shown in Figure 16.1.

In accordance with this scheme, a damaged transformer, located in a warehouse of faulty transformers, enters the fault detection and preparation department, which consists of three sections - disassembly and washing, diagnostics of windings and the mechanical part of the transformer. At the disassembly site, the transformer is cleaned, the oil is drained from its conservator, tank and oil-filled bushings, and then, having been convinced from the records in the accompanying documents and from preliminary tests that the transformer is malfunctioning, they proceed to its disassembly.

Damage to the external parts of the transformer (conservator, tank, fittings, outer part of the inputs, breakdown fuse) can be detected by thorough inspections, and damage to the internal parts - by various tests. However, test results do not always allow us to accurately establish the actual nature of the damage, since any deviation from the norm revealed as a result of tests (for example, increased no-load current) can be caused by various reasons, including a turn short circuit in the winding, the presence of a closed current loop through tightening bolts and pressing parts, incorrect connection of parallel windings, etc. Therefore, during the diagnostic process, as a rule, the transformer is disassembled and, if necessary, the active part is lifted, which allows not only to accurately determine the causes, nature and extent of damage, but also to determine those required to repair the transformer materials, tools and equipment, as well as time.

DISASSEMBLYANDDEFINITIONFAULTS

The sequence of disassembly operations in each case depends on the design of the transformer to be repaired. Modern transformers of domestic production, differing in power and design, and transformers produced in previous years, as well as those produced in the past and currently supplied by foreign companies, are being repaired; therefore, it is recommended to recommend any unified technological sequence for performing disassembly and repair operations of all incoming transformers impossible.

Before disassembling, check the completeness of the transformer received for repair (all assembly units and parts required for this design must be available), as well as the connection of its external parts, the integrity of the welds and connections, and the absence of oil leakage from the flange connections of the fittings to the tank.

First stage of disassembly. Disassembly begins with the removal of the gas relay, thermometer, expander, safety pipe and other devices and parts located on the transformer cover.

Having removed the relay, safety pipe and expander, disassembly continues, moving on to dismantling the transformer cover, which is carried out in compliance with precautions to prevent damage to the porcelain parts of the inputs of the HV and LV windings. The bolts removed from the entire perimeter of the cover, together with the washers put on them and the nuts screwed onto their threads, are washed, coated with anti-corrosion lubricant and, placed in boxes, stored for reuse when assembling the transformer.

The cover, freed from bolts, is slung using lifting eyes screwed onto the threaded ends of the lifting pins protruding from the cover and secured to the yoke beams of the upper yoke of the magnetic circuit. Transformers with a power of up to 4UU kV A usually have two lifting eyes; those of higher power have four. To lift the active part, special devices and slings are used that are designed for the weight of the load being lifted and have passed the necessary tests. When dismantling radiators and other large parts of an outdoor transformer, a truck crane is used as a lifting mechanism.

When lifting the active part of transformers with inputs located on the walls of the tanks, first disconnect the taps and dismantle the inputs, and then lift the active part of the transformer. The active part, lifted from the tank, is installed on a strong platform made of planed boards or on wooden beams so as to ensure its stable vertical position and the possibility of inspection, testing and repair.

Continuing disassembly, disconnect the taps from the inputs and the switch and check the condition of their insulation, the reinforcing seams of the inputs and the contact system of the switch (all noticed faults are recorded). Next, unscrew the eyelets from the vertical studs, remove the cover, take it to the side and lay it so that the glazing protruding under the cover is not damaged; the entries are protected from mechanical damage by covering them with rigid cardboard cylinders or wrapping them in clean burlap.

Second stage of disassembly, the most complex and labor-intensive, is the dismantling of the windings, the main operations of which are performed in the following sequence: remove the vertical studs, unscrew the nuts of the coupling bolts and remove the yoke beams of the magnetic circuit, loosen the upper yoke of the magnetic circuit, tying and arranging the packages of plates in the order in which they will be more convenient lay when mixing the upper yoke. Next, disassemble the connections of the windings, remove the taps, remove the wooden and cardboard parts of the wedging of the HV and LV windings and remove the windings from the rods manually (windings of a transformer with a power of up to 63 kVA) or using a lifting mechanism (windings of transformers with a power of 100 kVA and above) - first HV , and then NN.

After disassembling the transformer, inspect its external part. At the same time, check the cleanliness of the windings, paying special attention to the channels between the windings and the magnetic core. Identify by touch the places where the turns are weakened. In these places, as a rule, the winding insulation is damaged, charred as a result of interturn short circuits that are invisible from the outside. They check by external inspection the condition of the insulation, the absence of deformations and displacement of the windings or its turns, the presence of insulating gaskets, wedges, and spacers.

The main tasks of servicing switchgears (RU) are: ensuring specified operating modes and reliability of electrical equipment, compliance established order performing operational switching, monitoring the timely implementation of planned and preventive maintenance.

Reliability of operation is usually characterized by specific damage per 100 connections. Currently, for a 10 kV switchgear, this indicator is at the level of 0.4. The most unreliable elements of the switchgear are switches with a drive (from 40 to 60% of all damage) and disconnectors (from 20 to 42%).

The main causes of damage: breakdown and overlap of insulators, overheating of contact connections, breakdown of drives, damage due to incorrect actions of maintenance personnel.

Inspection of the switchgear without shutdown should be carried out:

    at facilities with permanent duty personnel - at least once every three days,

    at sites without permanent staff on duty - at least once a month,

    at transformer points - at least once every 6 months,

    Switchgear switchgear with voltage up to 1000 V - at least 1 time in 3 months (at KTP - at least 1 time in 2 months),

    after disconnecting the short circuit.

During inspections the following is checked:

    serviceability of lighting and grounding network,

    Availability protective equipment,

    oil level and temperature in oil-filled devices, no oil leakage,

    condition of insulators (dustiness, presence of cracks, discharges),

    condition of contacts, integrity of seals of meters and relays,

    serviceability and correct position switch position indicators,

    work alarm systems,

    proper heating and ventilation,

    condition of the premises (serviceability of doors and windows, absence of leaks in the roof, presence and serviceability of locks).

Extraordinary inspections of open switchgears are carried out in unfavorable weather conditions - heavy fog, ice, increased contamination of insulators. The inspection results are recorded in a special journal for taking measures to eliminate identified defects.

In addition to inspections, the equipmentswitching devices are subject to preventive checks and tests carried out in accordance with the PPR. The scope of the activities carried out is regulated and includes a number of general operations and individual work specific to this type of equipment.

Common ones include: measuring insulation resistance, checking the heating of bolted contact connections, measuring DC contact resistance. Specific tests include checking the timing and movement of moving parts, the characteristics of switches, the operation of the free release mechanism, etc.

Contact connections are one of the most vulnerable points in switchgears. The condition of contact connections is determined by external inspection, and during preventive tests - using special measurements. During an external inspection, pay attention to the color of their surface, the evaporation of moisture during rain and snow, the presence of glow and sparking contacts. Preventive tests include checking the heating of bolted contact joints using thermal indicators.

Basically, a special thermal film is used, which is red at normal temperatures, cherry - at 50 - 60°C, dark cherry - at 80°C, black - at 100°C. At 110°C for 1 hour it is destroyed and takes on a light yellow color.

Thermal film in the form of circles with a diameter of 10 - 15 mm or strips is pasted in a controlled place. At the same time, it should be clearly visible to operating personnel.

Busbars of 10 kV switchgear should not heat up above 70 °C at an ambient temperature of 25 °C. IN Lately to control the temperature of contact connections, electric thermometers based on thermal resistances, thermal candles, thermal imagers and pyrometers began to be used (operating on the principle of using infrared radiation).

Measurement of the contact resistance of contact connections is carried out for buses with a current of more than 1000 A. The work is performed with the equipment disconnected and grounded using a microohmmeter. In this case, the resistance of the section of the bus at the point of contact connection should not exceed the resistance of the same section (in length and cross-section) of the whole bus by more than 1.2 times.

If the contact connection is in unsatisfactory condition, it is repaired, for which it is disassembled, cleaned of oxides and contamination, and coated with a special anti-corrosion lubricant. Retightening is done with an adjustable torque wrench to avoid deformation.

Insulation resistance is measured for suspension and support insulators with a 2500 V megohmmeter, and for secondary circuits and switchgear equipment up to 1000 V - with a 1000 V megohmmeter. The insulation is considered normal if the resistance of each insulator is at least 300 MOhm, and the insulation resistance of the secondary circuits and equipment RU up to 1000 V - at least 1 MOhm.

In addition to measuring the insulation resistance, single-element support insulators are tested with increased power frequency voltage for 1 min. For low-voltage networks, the test voltage is 1 kV, in 10 kV networks - 42 kV. Multi-element insulators are monitored at positive ambient temperatures using a measuring rod or a rod with a constant spark gap. To reject insulators, special tables of voltage distribution along the garland are used. An insulator is rejected if it experiences a voltage less than the permissible one.

During operation, a layer of contamination is deposited on the surface of the insulators, which does not pose a danger in dry weather, but in drizzling rain, fog, or sleet it becomes conductive, which can lead to overlapping of the insulators. For elimination emergency situations insulators are periodically cleaned by wiping by hand, using a vacuum cleaner and hollow rods made of insulating material with a special tip in the form of curly brushes.

When cleaning insulators on open switchgears, use a jet of water. To increase the reliability of the insulators, their surface is treated with hydrophobic pastes that have water-repellent properties.

The main damage to disconnectors is burning and welding of the contact system, malfunction of insulators, drive, etc. If traces of burning are detected, contacts are cleaned or removed, replaced with new ones, bolts and nuts on the drive and in other places are tightened.

When adjusting three-pole disconnectors, check the simultaneous activation of the knives. For a correctly adjusted disconnector, the knife should not reach the stop of the contact pad by 3 - 5 mm. The force of pulling the knife from the fixed contact should be 200 N for a disconnector for rated currents of 400 ... 600 A and 400 N for currents of 1000 - 2000 A. The rubbing parts of the disconnector are coated with anti-freeze lubricant, and the surface of the contacts is coated with neutral petroleum jelly with an admixture of graphite.

When inspecting oil switches, insulators, rods, and membrane integrity are checked safety valves, oil level, color of thermal films. The oil level must be within the permissible values ​​on the level indicator scale. The quality of contacts is considered satisfactory if their contact resistance corresponds to the manufacturer's data.

When inspecting oil-volume switches, pay attention to the condition of the tips of the contact rods, the integrity of flexible copper compensators, and porcelain rods. If one or more rods break, the circuit breaker is immediately taken out for repair.

Abnormal heating temperature of the arc-extinguishing contacts causes darkening of the oil, a rise in its level and a characteristic odor. If the temperature of the circuit breaker tank exceeds 70 °C, it is also taken out for repair.

The most damaged elements of oil switches are their drives. Drive failures occur due to malfunctions of control circuits, misalignment of the locking mechanism, malfunctions in moving parts and breakdown of coil insulation.

Current repairs of switchgears are carried out to ensure the operability of the equipment until the next scheduled repair and involves the restoration or replacement of individual components and parts. Major repairs are performed to restore full functionality. It is carried out with the replacement of any parts, including basic ones.

Current repairs of switchgears with voltages above 1000 V are carried out as needed (within the time limits established by the chief engineer of the power enterprise). Overhaul of oil switches is carried out once every 6 - 8 years, load switches and disconnectors - once every 4 - 8 years, separators and short circuiters - once every 2 - 3 years.

Current repairs of switchgears with voltages up to 1000 V are carried out at least once a year on open transformer substations and after 18 months on closed transformer substations. At the same time, the condition of the end seals is monitored, dust and dirt are removed, as well as insulators are replaced, tires are repaired, contact connections and other mechanical components are tightened, light and circuit circuits are repaired sound alarm, measurements and tests established by standards are carried out.

Major repairs of switchgears with voltages up to 1000 V are carried out at least once every 3 years.

Usually Maintenance electrical installations is carried out monthly on the basis of the PPR developed according to the technical specifications. IN specific example I will describe the fullest scope of work; if there is no work in the work plan for the current month, then they are omitted and completed within the period specified in the work plan.

Inspection of electrical installation.

  • Electrical panels are inspected in working condition with consumers connected, that is, when there is a workload, the inspection begins with the main switchboard.
  • First, the integrity of cabinets, panels, serviceability of locks and integrity of seals are checked.
  • The next step is to inspect conductors and circuit breakers for burning, darkening and other visible defects, for example, broken levers or buttons.
  • The inspection is also carried out by ear, checking for the absence of crackling and buzzing.
  • The presence of tags on the cables and the presence and compliance of linear circuits in the electrical panel are checked.
  • Identified defects are photographed and recorded in the Maintenance Report.

After this, measurements are taken.

  • The load at the input is measured in phases and in the neutral using current clamps.
  • The temperature of the terminals at the switch and input circuit breaker, as well as at other connections in the main electrical panel, is measured.
  • The load and temperature of the connections at the input are recorded in the Maintenance Report; any connections or conductors with a temperature above 50C are also recorded in the Maintenance Report. Please note that the neutral at the input records both amperes and temperature.
  • Afterwards, all additional distribution boards according to a similar scheme, the only difference is that according to RShch, ShchO, ShchV, etc. The act records only conductors or circuit breakers whose temperature exceeds 50C.
  • The power section in ventilation, air conditioning and any other panels is inspected. Alarm systems are not inspected. UPSs are inspected but not serviced.

The device or electricity metering unit is inspected.

  • During the monthly inspection, a photograph is taken, readings at the time of inspection are recorded, and the integrity of the seals is checked. All these actions are needed to monitor performance, and not to take readings. The results are recorded in the monthly Maintenance Report.
  • During the annual audit, a special inspection report for electrical energy metering devices is used to record the inspection results.
  • The Certificate records the installation location (for example, main switchboard), type, model, serial number, checks the seals and the date of the last verification.
  • The operation for instrument transformers, if any, is repeated separately.
  • If there are transformers, the act indicates the approximate length of the connection wires and their cross-section, this is especially important if they are not in the same panel with the meter.
  • Photos are taken of the metering station close-up to see the seals and condition of the wires.

RCDs and differential circuit breakers are monitored for leakage.

  • Control is carried out by pressing the test button; before control, it is checked that the consumer is ready for a power loss.
  • If the RCD protects the line with server equipment, then such a check is not carried out without the person responsible for the operation of the computers or without a person who can temporarily turn off the computers.
  • The monthly maintenance report records all RCDs, both those that passed the test and those that failed. The marking of the shield (ShchO, ShchR) is recorded, and then all the RCDs that passed the test are numbered, similarly with those that did not pass.

All contact connections are drawn.

  • Pulling is carried out with the electrical installation completely switched off.
  • Without exception, all contact connections are drawn in all switchboards, including the power section in ventilation and air conditioning switchboards and other switchboards with automation. Switchboards with automation are usually not maintained until they break down; therefore, no one monitors the power part. Our task is to prevent it from burning.
  • The grounding contacts of electrical panels are carefully inspected for oxidation, except for the broach itself.
  • If oxidation is suspected, the contact is disassembled and cleaned with fine sandpaper.
  • If, as a result of broaching, connections were identified that were loosened by more than one turn, then such connections are recorded in the Maintenance Report for re-inspection.

Electrical panels are cleaned of dust.

  • Electrical panels are cleaned not only inside, but also outside, including the top panel. The top panel is wiped monthly, regardless of the PPR.
  • The vending machines are cleaned from dust using a brush and a vacuum cleaner. The brush is used either plastic (preferred option) or with a completely insulated metal part, regardless of what is used when the electrical installation is turned off.
  • Based on the results of cleaning, there should be no visible dust contamination on any surfaces in the electrical panel, which is verified using the photographs provided.
  • If the shield is heavily contaminated, for example, with grease or similar impurities that cannot be removed, then this will be recorded in the Maintenance Report for further coordination of the time of long-term shutdown of the electrical installation for complete cleaning using alcohol or other solvents.

The procedure for turning on the electrical installation.

  • First, all switched on machines, ouzo and difavtomats are turned off.
  • After this, the main machine or switch is turned on.
  • And only after this, gradually, with intervals between switching on, the load on all lines returns; the intervals depend on the rating of the circuit breaker on the connected line and the type of equipment connected to it. The goal must be to avoid coincidence of load peaks, which can overload the main circuit breaker and cause it to trip.

Photography is being done.

  • After complete completion of all work with the shields, photographs are taken
  • The switchboard equipment is photographed close-up, so that the inscriptions on the machines and the condition of the wires are visible. If necessary, the shields are photographed from top to bottom in several photographs.

Emergency lighting is checked.

  • To check emergency lighting, it must be connected to a separate switchboard or a group of switchboards, or have a separate distribution board. If this is not the case, then this is a violation and it is recorded in the Maintenance Act.
  • If the emergency lighting is powered from the landlord's network, it cannot technical reasons be checked when servicing the tenant's electrical installation. This fact must be recorded in each Maintenance Report during an emergency lighting inspection.
  • The test is carried out by turning off the circuit breaker of the emergency lighting line. The emergency lamps should light up or not go out depending on the type of connection. Light indicators must always be on and must not go out. In any case, after a power outage, all emergency lighting should work.
  • After the inspection, the supply of electricity to the line is restored by turning on the previously disconnected circuit breaker.
  • The Maintenance Certificate indicates the total number of lamps, as well as the separate number of those that worked and those that did not work, the same for the signs.
  • This information is also indicated in the Maintenance Log
  • For all non-working lamps, an additional check is carried out in order to determine the reasons for their failure:
    • checking the presence of phase and zero at the terminals of the lamp
    • the serviceability of the lamp lamp is checked by replacing it with a known good one
  • All non-functioning lamps and indicators are photographed to simplify subsequent identification during replacement and the fact of their malfunction is recorded in the Maintenance Log.
  • If the emergency lighting line is not allocated, then it can be checked by turning off all electricity at the site, as in the previous case, emergency lights should be on after a power loss. The absence of a dedicated line must be recorded in the Maintenance Certificate.

Additional work in progress

After completing the electrical installation maintenance work, additional work is performed, such as replacing burnt out lamps, repairing lamps, repairing or replacing switches or sockets. Such work can either be included in the contract or ordered additionally, but in any case, a list of these works can be provided to the electrician only by the person specified in the contract, appointed responsible for negotiations on the completion of the work.
Performance additional work in all cases, it is recorded by signing the Work Order.

After completion of all work, documentation is drawn up.

Safe switching operations in switchgear can be guaranteed if personnel strictly adhere to the following operating procedures:

  • 1) disconnecting live parts on which work is supposed to be carried out;
  • 2) disconnecting live parts that cannot be accidentally touched or approached at a dangerous distance;
  • 3) taking measures to prevent the erroneous supply of voltage to the work site;
  • 4) installation of warning posters;
  • 5) installation of temporary fences made of insulating materials;
  • 6) checking all terminals of disconnected equipment and all switch terminals for absence of voltage;
  • 7) grounding and short-circuiting of disconnected live parts on all sides from which voltage can be supplied;
  • 8) installation of a “Work here!” poster at the place of work.

Disconnection must be done in such a way that there are gaps between the disconnected and live parts that are energized, visible from all sides.

According to intersectoral labor safety rules, the following distances are determined from people, the tools they use, devices and temporary fences to electrical equipment, depending on the voltage values ​​of the installations (Table 8.2), as well as from mechanisms, lifting machines, slings and loads (Table 8.3).

Particular attention must be paid to the possibility of reverse transformation low voltage through transformers. To prevent this from happening, power and instrument transformers related to the equipment being switched off are also switched off on the low voltage side. In order to prevent spontaneous or erroneous activation of switches and disconnectors,

8.2. Distances from people, the tools they use, devices and temporary fences to live parts of electrical equipment at different voltages

8.3. Distances from mechanisms, lifting machines, slings, loads to live parts of electrical equipment at different voltages

If in the power circuits of the remote drives of the disconnected disconnectors, remove the fuses on both poles. All disconnector drives accessible to unauthorized persons are locked.

On all control keys and drives of switches and disconnectors, with the help of which voltage can be supplied to the place of work, the worker performing the shutdown hangs up posters: “Do not turn on - people are working!” When working on the line, posters are hung on the drives of linear disconnectors: “Do not turn on - work on the line!”

In the diagram of the dispatcher in charge of the shutdown, as many posters are posted as there are crews working.

Temporary fencing can be special solid or lattice wooden screens, products made of micanite, rubber and other insulating materials that are dry and well reinforced.

The need to install fences, their type, and installation method are determined depending on local conditions and the nature of the work. Posters are hung on temporary fences: “Stop - high voltage!”

After installing warning signs and temporary barriers, personnel prepare a set of portable grounds, attach them to the grounding wiring, and then test the parts of the installation intended for work to ensure that there is no voltage.

To check for the absence of voltage, use a voltage indicator. Immediately before the test, make sure that the indicator is in good working order by bringing it closer to live parts located nearby and known to be energized. These checks are carried out wearing dielectric gloves. When checking for the absence of voltage in open switchgears with voltages of 35 and 110 kV, a spark gap is attached to the working part of the indicator screwed onto the rod. If there is voltage, then light appears and sound signals(characteristic crackling sound). This check is done only in dry weather. After checking the installation for the absence of voltage, ground and short-circuit the current-carrying parts of all phases on which work will be carried out or from which voltage can be supplied to the part of the installation that is disconnected for work.

Grounding to the disconnected equipment is installed immediately after checking for the absence of voltage. In this case, it is not allowed to apply grounding without first connecting it to a grounding device. Portable grounding clamps are applied using a rod made of insulating material to the grounded current-carrying parts of all phases, then the clamps are securely connected using the same rod or directly with hands wearing dielectric gloves. After applying grounding, a poster is hung at the work site: “Work here!” Temporary portable grounding connections are made from bare, flexible stranded wires cross-sectional area of ​​at least 25 mm 2, tested for thermal stability.

When removing grounding, it is first removed from live parts and then disconnected from the grounding loop. The work order is closed after inspection of the equipment and the place where the work was carried out. Only after the work order is closed, the equipment is put into operation, having previously completed the following operations:

  • 1) disconnecting the grounding blades or removing portable grounding connections;
  • 2) insulation check;
  • 3) removal of temporary fences and warning posters;
  • 4) installation of permanent fences in place and removal of all posters posted before the start of work.

If several teams were working on a switched-off installation, then it can be turned on only after all crews have closed.

The serviceability of the insulation of equipment switched on after repair is checked with a megohmmeter. This allows you to identify insulation defects that are difficult to detect by inspection.

If a ground fault is detected, then before disconnecting the damaged section in closed switchgears, you must not approach the fault location at a distance of less than 5 m, and in open substations - at a distance of 10 m. The exception is cases when it is necessary to take measures to eliminate a ground fault or provide first aid to victims. In these cases, personnel must be very careful and use all necessary protective equipment.

In case of accidents with people, voltage can be removed from the relevant part of the installation without the permission of a superior operational personnel.

In electrical installations with voltage up to 1 kV, work on the busbars of switchgears, distribution boards, assemblies, as well as on the connections of the listed devices through which voltage can be supplied to the busbars, must be carried out in sequence. At dead-end connections, work may be carried out by order.

When working in electrical installations in which the voltage has been removed from all live parts, including the terminals of overhead lines and cable lines, provided that the entrance to adjacent electrical installations is locked (assemblies and panels with voltages up to 1 kV can remain energized), it is allowed to issue one work order for simultaneous operation on all connections.

The switchgear electrical equipment being repaired must be disconnected with a visible circuit break on all sides from where voltage can be supplied to it.

In electrical installations with voltages up to 1 kV, voltage is removed by turning off manually driven devices, and if there are fuses in the circuit, by removing them. If there are no fuses in the circuit, erroneous switching on of the device is prevented by locking the handles, locking the cabinet doors, and installing insulating pads between the contacts of the device.

When working on the equipment of a trolley or in a compartment of a switchgear cabinet, the trolley with the equipment must be rolled out into the repair position; Lock the curtain of the compartment in which live parts remain energized and hang a safety poster “Stop! Voltage"; Display a “Work here” sign on the cart or in the compartment where you will be working.

When working outside the switchgear on equipment connected to them or on outgoing overhead lines and cable lines, the trolley with the switch must be rolled out of the cabinet into the repair position, the curtain or doors must be locked and signs “Do not turn on!” must be posted on them. People are working" or "Don't turn it on! Work on the line."

In this case it is allowed:

  • - if there is a blockage between the grounding knives and the trolley with the switch, install the trolley in the control position after turning on these knives;
  • - in the absence of such a lock or grounding blades in the switchgear cabinets, install the trolley in an intermediate position between the control and repair positions, provided that it is locked with a lock. The trolley can be installed in an intermediate position regardless of the presence of grounding at the connection.

Installing a trolley with a switch in the control position for testing and working in control and protection circuits is permitted in cases where work outside the switchgear on outgoing overhead lines and cable lines or on the equipment connected to them, including mechanisms connected to electric motors, is not carried out or grounding is carried out in switchgear cabinet.

Repair work in electrical distribution installations up to 1 kV, taking into account their small dimensions, is carried out under the condition that live parts under voltage, which can be accidentally touched, are fenced off near the workplace. You must work in dielectric galoshes or on an insulating stand or mat; use the tool with insulating handles. It is prohibited to work in a bent position if, when straightened, the distance to live, unswitched parts is less than 0.6 m. It is unacceptable for unprotected live parts to be located behind the worker or on both sides.

Scaffolds and ladders must be in good working order. Application metal stairs forbidden. Work using ladders is carried out by two people, one worker should be at the bottom.

During the period of electrical repair work, it is prohibited:

  • - work with electrical tools that do not have double insulation and are powered by a voltage of more than 42 V;
  • - disassemble power tools and make any repairs to power tools.

The repair tool should be stored in a specially designated place. Electric soldering irons must be installed only on special metal stands.

To remove excess solder from the rod of an electric soldering iron, you must use a cotton cloth or an asbestos pad. Shaking the electric soldering iron is strictly prohibited. Cleaning the electric soldering iron rod and replacing it heating element can only be done when the soldering iron is disconnected from the mains and in a cold state.

When soldering or pulling wires from a connector, wear safety glasses to avoid splashing molten solder into your eyes or face. Particular care must be taken when tinning rigid wires and cable strands, which can spring back and splash molten solder. It is not allowed to immerse heat-resistant insulation and other materials that emit toxic volatile substances when heated, as well as wet materials, into a crucible with molten solder, as this may cause the release of molten solder. Check the strength of the crucible fastening to avoid its possible overturning, the serviceability and reliability of the crucible grounding.

Overhauls of equipment (RU) include external and internal inspections of all elements of the circuit; checking the state of insulation of devices and wiring; revision of all devices included in the scheme in accordance with the instructions for individual devices; checking relay settings; checking the operation of the entire circuit without turning on the power circuits; checking the operation of the entire installation in operation.

Routine repairs and inspections of devices that require more frequent checks than the entire installation as a whole are carried out according to a reduced program.

Unscheduled repairs and inspections are carried out after the accident has been eliminated.

Planned repairs are carried out in the following periods:

Boards, panels, cabinets and control assemblies.....................................1 time per year

Equipment for lifting and transport mechanisms............................2 times a year

Control relays, contactors, starters................................................. Monthly

Controllers, command devices...................Inspection - upon acceptance of a shift,

revision - during a planned shutdown of the mechanism (but at least once every 4-6 months) Automatic switches................................... ............................Monthly

Before starting repair work, the foreman must explain to the workers the features of a particular reactor plant and the situation on it. In particular, you should indicate:

  • - access routes to each workplace, the presence of dangerous zones;
  • - procedure for connecting electrical devices and tools;
  • - places and procedure for installing lifting equipment in the repair area;
  • - presence of existing electrical installations nearby and appropriate safety measures.

In turn, before starting work, electricians are obliged to:

  • - check the serviceability of your tools, equipment, devices and arrange them in an order that is convenient and safe for use;
  • - tidy up overalls and hats;
  • - inspect and prepare your workplace, remove unnecessary items.

Chopping-type devices are installed during repairs so that they cannot close the circuit spontaneously under the influence of own strength gravity. Switching device drives must clearly indicate the on and off positions. The equipment of switchgears, switchboards, and assemblies must be accessible for inspection, provided that the control panel is connected to the network. After equipment repairs, panels must be clearly labeled to indicate which unit they belong to. Such inscriptions must be on the front and reverse sides panels. All keys, buttons and control handles must have inscriptions indicating the operation for which they are intended (“Enable”, “Disable”, “Add”, etc.).

When repairing circuit breakers (switches), thoroughly clean the contact surfaces of the knives and sponges from dirt, soot and particles of melted metal. In case of severe melting, replace the jaws or knives with new ones, tighten all fasteners and hinge joints, check the condition of the springs and spring brackets; weakened springs are replaced with new ones. Make sure that the knives enter the jaws without impacts or distortions, but with some effort.

The contact surface of the sponge should fit snugly against the corresponding surface of the knife. A probe with a thickness of 0.05 mm should enter the space between the sponge and the knife to a depth of no more than 6 mm.

The depth of entry of the knives into the jaws is adjusted so that for a switch with a lever drive, the knives, when in the fully engaged position, do not enter 3 mm to the contact area of ​​the jaws. At the same time, the entire contact part of the knife should fit into the jaws. The non-simultaneous exit of the knives from the contact jaws should not exceed 3 mm.

Push-button stations, cam control devices, universal switches and limit switches do not require special adjustment. They only check the free movement of moving parts, touching and pressing contacts in the on position, and the compliance of universal switches and command devices with the contact circuits. The rollers of the control devices must rotate freely.

For contactors and magnetic starters, by turning them on by hand with the voltage removed, the ease of movement of the moving system is checked. If the shaft is stuck in the bearings, 3-4 drops are injected into the latter through special holes machine oil. If, after lubrication, the shaft rotates tightly, then it is necessary to eliminate the distortion in the bearings, for which the bolts securing the bearings are loosened and a position corresponding to free movement is found, then the fastening bolts are tightened again.

It is necessary to check the tightness of the armature and yoke of the magnetic system, thoroughly cleaning their end parts from dirt and rust, which avoids vibration and the associated increased wear of the device. The tightness of the anchor is checked with a probe 0.05 mm thick. The short-circuited damper turn in the core slot must be tightly clamped in its groove and must not have a break.

Mechanical interlocking should not prevent the interlocked devices from being fully switched on. When one device is turned on, you need to make sure that it is impossible to turn on the interlocked device.

Repair of switchgears and equipment with voltage over 1 kV. In a 6...10 kV switchgear with a single busbar system and any number of sections, when the entire section goes out for repairs, one work order is issued to work on the busbars and on all or part of the connections of this section. Admission to all workplaces of the section is carried out simultaneously; The team is allowed to disperse among different work places within this section.

It is prohibited to prepare for switching on or testing under voltage any connection of a section until the completion of work on the work.

One work order for the simultaneous or alternate performance of work at different workplaces of one or several connections without registration of transfer from one workplace to another with the dispersal of the team among different workplaces may be issued in the following cases:

  • - when laying and relaying power and control cables, testing equipment, checking protection devices, interlocks, automation, etc.;
  • - repair of switching devices when their drives are located in another room;
  • - repair of a separate cable in a tunnel, collector, well, trench, pit;
  • - repair of cables (no more than two), carried out in two pits or a closed-circuit switchgear and a nearby pit, when the location of the workplaces allows the work supervisor (supervisor) to supervise the team.

When carrying out work, all workplaces must be prepared before admission. If the team is dispersed among different work places, the following is allowed to remain: one or more team members with electrical safety group III, separately from the work performer; team members who will have to be separate from the work contractor; the latter must bring them to their workplaces and instruct them regarding work safety.

For safety reasons, before being allowed to operate switching devices with remote control, the following must be in place:

  • - the drive power circuits, operating current circuits and heating circuits are disconnected;
  • - the valves on the air supply pipeline to the pneumatic drives are closed and locked; the air present in them is released into the atmosphere, while the starting plugs (valves) are left in the open position;
  • - the closing weight or closing springs are brought into non-working position;
  • - posters “Do not turn on! People work" on the keys remote control and “Do not open! People are working” - on closed valves.

For test switching on and off of the switching device during its setup and adjustment, it is allowed, if the work order has not been delivered, to temporarily supply voltage to the operating current circuit and the power circuit of the drive, to the signaling and heating circuit, as well as to supply air to the drive and to the switch.

Installing removed fuses, turning on disconnected circuits and opening valves when supplying air, as well as removing “Do not turn on!” posters during testing. People are working" and "Don't open! People are working” is carried out by operational personnel or, with their permission, by the work performer. The person performing the adjustment or adjustment, or at his request, the operating personnel, is allowed to remotely turn on or turn off the switching device for testing.

After testing, if it is necessary to continue working on the switching device, a person from the operating personnel or with his permission from the work manufacturer must carry out the technical measures required for permission to work.

Climbing onto an air circuit breaker that is under operating pressure is permitted only during testing and adjustment work (adjusting dampers, taking vibrograms, connecting or disconnecting conductors from measuring instruments, identifying air leaks, etc.).

Climbing onto a disconnected air switch with an air-filled separator, when the separator is under operating pressure, is prohibited in all cases.

The moisture resistance (tightness) of air switches is checked under reduced pressure in accordance with factory instructions.

Before climbing onto the air circuit breaker for testing and adjustment, you must:

  • - disconnect the operating current circuits;
  • - block the local control button and starting valves (for example, disconnect the air duct pipes, lock the cabinets, etc.) or place an instructed team member near the switch, who would allow only the responsible person to operate the switch (after turning on the operating current), as directed by the work manager.

While people are on the air circuit breaker under pressure, stop all work in the control and distribution cabinets.

At the time of switching off and switching on air switches during testing, adjustment and testing, the presence of people near the switches is not allowed.

The test and adjustment worker (or a person authorized by him from the team) can give a command to perform operations with the circuit breaker after the team members have been removed from the circuit breaker for safe distance or to a shelter.

Before permission to work involving people staying inside air collectors, you must:

  • - close the valves on all air ducts through which air can be supplied, lock them, and hang posters on the valves “Do not open! People are working";
  • - release the air under pressure in the air collector, leaving the plug in its upper part and the drain valve open;
  • - disconnect the air supply duct from the air collector and install plugs on it.

A zero reading on pressure gauges on switch tanks and air collectors cannot serve as a reliable indication of the absence of compressed air. When removing manhole covers, immediately before unscrewing the bolts and nuts, it is necessary to ensure that there is actually no compressed air by opening the drain plugs (valves) or valves.

Drain plugs (valves) or valves may be closed only after screwing in the bolts and nuts securing the manhole cover.

In switchgear with equipment on roll-out trolleys, it is prohibited to penetrate into compartments that are not separated by solid lines without removing the voltage from the busbars and grounding them. metal partitions from buses or equipment directly connected to them. To work on outgoing cables, electric motors and other equipment directly connected to these cables, carts with switches are completely rolled out, cabinet doors or automatic curtains are locked and a “Do not turn on!” sign is posted on them. People are working."

The cables in the switchgear compartments are grounded. In cases where grounding is applied at the work site, it is not necessary to apply it in the switchgear compartments.

In case of work on cable funnels installed in switchgear compartments, the trolleys with switches are completely rolled out, and a poster “Do not turn on!” is hung on the doors or back wall of the compartment. People are working,” the automatic curtains are locked, and a sign “Stop!” is hung on the top curtain. Voltage". To access the compartment, remove the vertical partition inside the cabinet or back wall; on cables through which voltage can be supplied, check for its absence and apply grounding; a “Work here” poster is hung in the compartment. When working on switchgear equipment located on trolleys, they are completely rolled out and a “Work here” poster is placed on the equipment. During work in the compartments, a “Work Here” poster will be displayed inside the compartment.

After the cart is rolled out, the cabinet doors are locked and a sign “Do not turn on!” is hung on them. People are working." If there is no door, the automatic curtains are locked and a sign “Stop!” is hung on them. Voltage". When working on devices, relays, secondary circuits, etc. without rolling out carts with equipment, hang a sign “Do not turn on! People are working,” and at the work site there is a poster “Work here.”

The trolley with the switch can be installed in the test position in the following cases:

  • - for testing the switch and adjusting the drive, checking the relay protection of the connection;
  • - when preparing and assembling the diagram after completion of work and delivery of the work order;
  • - when working on the mechanical part of an electric motor or on the mechanism driven by it.

In this case, a poster “Do not turn on!” is hung on the locked cabinet doors. People are working."

Work in the switchgear room is carried out one by one and only on a trolley with equipment rolled out of the cabinet.

Rolling out a trolley with a switch or other equipment completely from the cabinet or into a test position, as well as rolling it in and installing it in place is carried out by an operating personnel worker with qualification group IV, individually or under his supervision, with a preliminary check of the disconnection of the grounding knives.

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