The image of electrician EVN cleaning the power line with high pressure water

With the criteria of improving the reliability of power supply, ensuring continuous power supply, minimizing the time of power loss for customers in daily life, production and business (ensuring SAIDI, SAIFI indicators, MAIFI), EVN has applied insulation insulation method of the grid operating with high pressure water (line hotline cleaning).

Cleaning the hotline is cleaning the insulation of the line, insulation of outdoor equipment in the substation when the device is carrying electricity. Hygienic environment is insulating water that is shot and washed with high pressure, the sanitation staff approach the electricity-carrying object through the insulation water.

Clean the line hotline.

Water used for cleaning is insulating water, ie water with high resistivity (or low conductive electricity). When this water flow is in contact with the power source, the leakage current will be <1mA. Water before pumping to clean the insulation must be treated including deionization, dust filter . to ensure insulation when firing on the grid is carrying electricity. Before each shot to clean the electricity and water, the insulation resistance must be measured. When moving from one working position to another, the insulation resistance of the water must be measured again. This is mandatory and important to ensure safety when firing water on a power grid.

All types of hotline cleaning work are performed when operators operate on earth potentials (on poles, on floors, on forklifts or on the ground), in contact with the electric carrying part through the insulated, pressurized water High force. The earth potential is the ground potential or above the column, on the operation floor, on the bucket, . with the ground. Employees working on the ground or on poles, on floors, on vehicles, . with grounding are considered employees with potentials with earth potentials.

Jobs allowed to clean hotline include: Cleaning insulation stand; Cleaning the insulating string (suspension insulator); Clean the insulation string; Cleaning insulation equipment hanging on electric poles and cleaning insulation of equipment in substations (except for cabinets, other types of cabinets).

Those who perform hotline cleaning must have a minimum level of electrical safety at level 4 and be fully equipped with personal labor protection, including: Workwear suits; Safety strap; Protective helmets, cloth gloves, canvas shoes, goggles; 1000V insulated gloves; and 22 kV insulated boots.

Cleaning substation hotline.

When performing hotline cleaning, only in normal weather conditions , work should not be carried out when there is a grade 4 or higher wind. Do not work when there is drizzle, thunderstorm, thunder, fog or when the environment has air humidity> 90% (> 85% with transmission net). When working, if you notice the possibility of thunderstorms and thunderstorms, you must stop the work immediately and withdraw from the scene. Do not work when there is insufficient light to see clearly the insulation and the electrical part.

Metal equipment, accessories and supplies involved in the cleaning of substation hotline and the line from 110kV or higher must be grounded. When cleaning the voltage line hotline to 35 kV, these devices may not need to be grounded.

Except for the water gun that has been pre-connected to the pipe and the nozzle, it is strictly forbidden to use metal objects on columns with length> 0.5m, non-metallic solid objects with length> 1m. When working on a high level, do not let guns, pipes and other objects reach out of the column body> 0.5m.

All overhead work items are pulled up inside the steel column with rope and pulley. The towing rope is arranged into endless pull rings, which are firmly positioned on both ends. Employees move on columns and when moving tools or metal parts onto a column, make sure not to approach the conductor with the distance specified in the following table:

With a voltage of 110kV, parts of metal equipment (such as cars, pumps, engines .) must be grounded. Grounding nozzle and safety grounding devices must be caught at 2 different points. People on the ground avoid contact with metal parts and ensure distance from the stand to the metal part> 3m (> 8m for transmission net) if not using insulated boots or standing on insulation mats. conduct work near a residential area or a place with a high density of people, there must be barriers at work, on the barricades hanging signs "STOP! RESISTANT DANGEROUS POWER" , those who are not on duty cannot into the work area.

Employees on the move and work on high must not carry metal personal items (watches, chains, cell phones, .), items for work as bait lines, keychains, sheaves, insulated gloves, goggles, etc. must be neatly put into personal bags.

Hotline cleaning is carried out in accordance with the Worksheet (in EVN's Electrical Safety Procedure) and the Worksheet (according to the separate form of the process) supervised and recorded by the commander of the hotline cleaning unit. Copy.

EVNCPC practice hotline cleaning at Hoi An.

When conducting hotline cleaning, a direct commander is required. Before conducting the work, the direct commander must check visually the insulated chains, vertical insulation of the equipment, if the insulation is cracked or broken more than 02 bowls, do not conduct cleaning. on that insulated chain.

The minimum distance from the nozzle to the charged element, the minimum resistivity (or maximum conductivity) of water, the minimum water pressure at the pump is determined according to the following table:

For transmission grids outside the distance safely from the nozzle to the grid, it is necessary to ensure the electric field intensity when working.

In order to protect the cleaning staff from insulating hotlines due to the influence of the electric field strength, special pants and shirts must be used when:

1. Working on the column with the electric field strength at which E> 5 kV / m and when the working time is greater than the time according to the formula T = 50 / E - 2 (hours) or when E ³25 kV / m;
2. If you have to wear specialized pants and shirts, before the staff goes to the column, the direct commander needs to check carefully the connections between the parts of the pants and shirt;
3. Sanitation of 500 kV grid insulation, recommending direct workers need to wear pants and vests to prevent electric field.

Equipment with large diameters and heavy contamination must arrange at least two nozzles with appropriate angles to clean at the same time, to avoid the phenomenon of one-sided cleaning, opposite surface contaminated with dirty water can cause discharge. When carrying out the cleaning work of the hotline completely or some insulation of the line must be cleaned in the direction from the bottom to the top. then gradually upwards.

Pay attention to the wind direction and washing angle. Shoot water with the wind. Limit splashing of water into unsanitary insulation. The water pressure of a large nozzle, which can cause injury to people and damage the surface of equipment and supplies at close range, is strictly forbidden to direct the nozzle to people, equipment and items while splash.

For composite and polymer insulators (including lightning protection valves, voltage transformers, current transformer), it is necessary to reduce the nozzle water pressure (- 5 bar) compared to cleaning ceramic or ceramic insulators. It is possible to reduce contact pressure by increasing the distance from the nozzle to the insulation.

When cleaning the insulated knife and fuse (FCO), care should be taken not to shoot water directly into the area where the cheek is connected to the insulated knife and the lead pipe itself. The equipment in the substation must not shoot water directly into the secondary wiring boxes. Where the wire is connected (earlobe), fixed wire to the insulator (neck tie), the three-phase cable heads should note that the pressure of the water jet can move the conductor, making short distance phase - phase, phase - soil causing discharge. With heavily contaminated insulation (moss, cement dust, coal dust, chemical dust, .), water should be shot at least twice, each separated by 5 to 10 minutes. When cleaning the appearance of electric light sparks on the insulation, direct the water beam to the point where the spark appears to clean and extinguish the halo.

A team when working at least 4 people, including: 1 person working on the high, 3 people working on the ground. Clearly assign tasks to each person on the high and the ground. High-flying people are equipped with safety strap, gloves, boots, glasses, hats, labor protection clothes, 3 people on the ground including: 1 person in charge of the motive, 1 side of the device, 1 person only Commander directly (cum supervisor). When preparing to splash water on the ground, stand away from the grounded metal or stand on an insulating carpet. When cleaning 110 kV lines with many circuits, high columns need to add a high-level assistant.

Cleaning hotline at transmission line.

How to clean the hotline support chain, stand insulation: With the single support chain (Figure 1) , the staff directs the gun hose into the bottom insulation bowl, when the pump has been operating enough water pressure, then shoot water, moving upwards follow the vertical heart of the insulated chain, when it comes to the top bowl, change the direction to quickly pull it down and stop firing at the bottom bowl. With the double support chain (Figure 2) , also perform from the bottom to the top but shoot the spilled water, back and forth between the two chains.

How to clean the hotline string: With the single-stranded string (Figure 3) , start shooting water from the outer insulation bowl (the side of the wire) and then slowly move it inside (the side of the column), changing the direction to pull out faster and end at the starting position. With the double-stranded string (Figure 4) , it is the same as the single-threaded string, but splashes water.

How to clean multiple hotline electric poles: Clean in turn from the bottom floor to the top floor; In the same floor, one side prioritizes cleaning the previous support string, the following string is truncated. In the same column (for example, outgoing column) there are many circuits, multiple voltages, managed by two or more units, when a unit conducts insulation cleaning, it must also comply with the hygienic principle from phase bottom up, not necessarily that line phase has the same management unit operating or not.

Clean the holine at the transmission TBA.

How to clean insulated equipment hanging on electric poles: Devices hanging on electric poles such as transformers, recloser, voltage transformer, current transformer, . if the insulation (busing) is arranged in a vertical position, then sanitation from the bottom up, if the insulation is arranged horizontally, clean from outside the conductor inside, perform sequentially from low to high.

How to clean equipment hotline in the substation: When cleaning equipment in the substation, it is necessary to pay attention to limit the water splashes to other unsanitary equipment, easy to create wet insulation, create water flow dirty, can cause electric discharge. Shoot the water down the wind, the equipment in front of the water shot should be cleaned first. Clean the device in turn from low to high; For equipment with a dielectric diameter cm 20 cm, use a water gun, perform cleaning from lower to top (Figure 5).

When the insulation is heavily contaminated and the device diameter> 20cm requires two simultaneous nozzles, two nozzles arranged at an angle of about 900, two nozzles operated by 2 staff, when the nozzle head pressure enough, shoot from the lowest part of the insulator, two taps simultaneously move upwards, to the top point of the insulation, the two taps move in the same direction to the bottom and end at the starting point. When lightly contaminated insulation can use a nozzle, shot into two at two different angles. Severe contamination is level C and D contamination according to ESDD standard (ESDD is the method of assessing the level of contamination of insulators according to the equivalent salt concentration), grade C:> 0.12 ÷ 0.24 mg / cm2, level D:> 0.24 mg / cm2).

When cleaning the insulated chains (busbar), perform the same as when cleaning the insulated string. With overhead equipment that can use dandruff vehicles, forklifts support staff to shoot water to the appropriate location. When cleaning the above insulated chains, it is necessary to pay attention to the equipment below, if the equipment is contaminated, it must be cleaned first. With gate column truss, steel structure busbar: when moving, lifting tools up and firing water always perform inside the column, beams. With a gantry column with 20m centrifugal concrete column: it is only allowed to climb up to a height of not more than 4m above the ground to clean insulation; Water pipes must be firmly fixed to the column body.

Contact information and dispatching work: Between the operator and the hotline unit, keep in touch by appointing a supervising representative in the field; Cleaning the hotline is not required to lock the auto-close function of the protective relay (F79); Cleaning the hotline does not change the status of grid operation and adjusting relays, so it is not necessary to carry out procedures for grid delivery with the regulation system at all levels but the operator must inform the moderation.

Preserving equipment, supplies and accessories for insulating hotline

All equipment, supplies and accessories for cleaning hotline insulation before use must check the certainty of mechanics and connection; Insulating articles must check the insulation (with valid insulating experiment minutes). After use, it must be cleaned, neatly arranged in storage, in a dry place; periodically check the maintenance of dynamic equipment, water treatment equipment.