Power cable line inspection content and cycle requirements
Cable inspection and maintenance is in order to grasp the cable operation status, timely detection and elimination of defects on the cable line and its ancillary equipment, check whether the environment around the cable to meet the requirements of the operating environment, in the cable failure to find faults in order to ensure safe and reliable power supply. Cable inspection is divided into regular inspection, special inspection and fault accident finding.
1.Patrol Safety Precautions
(1) Night patrol should carry lighting tools.
(2) Entering the cable tunnel, you should first check the oxygen content in the tunnel to prevent harm to the person; pay attention to the water situation in the tunnel to prevent poisonous snakes and other animals from causing harm to the personnel.
(3) When patrolling along the cable route, attention should be paid to the adjacent buildings and road obstacles.
(4) In case of lightning when patrolling, you should stay away from the patrolling equipment to prevent the lightning wave from invading the cable and causing injury to the person.
(5) cable line trip after the accident to find, the cable should be regarded as electrified equipment, find it is strictly prohibited to touch with their hands.
(6) After opening the cable cover should be sealed tightly.
2.Contents of the inspection
①
Check the appearance of the cable for corrosion, damage, hooks or brackets along the line for dislodging, and stacking of flammable, explosive and highly corrosive substances on and near the line.
The cable labeling is complete and clear, and the phase sequence is painted in accordance with the requirements.
②
Cable markers are complete and clear, with clear direction signs.
For each cable line laid underground, the road surface should be checked to see whether it is normal, whether there are any excavation marks, piles or whether the line marking stakes are intact.
And cable lines cross, parallel electric locomotive tracks of the cable connection line is good. There are no defects at the intersection of cable lines with railroads, highways and drainage ditches.
③
Underwater cables：
Check the condition of underwater routes once a year. When diving conditions permit, divers are dispatched for diving inspections, and when diving conditions do not permit, changes in the riverbed are measured.
④
Cables in trench and tunnel
The upper part of the outdoor cable trench should be slightly higher than the ground, covered with a cover made of concrete, the cable should be laid flat on the support and well drained, and the drainage of the trench should be checked after rain.
Tunnels and cable mezzanines should be checked to see if the holes are well sealed, whether the ventilation, drainage and lighting facilities are complete, and whether the fire protection devices are out of order.
Check whether the door locks of small rooms and terminal stations are open and closed normally and the door slits are tight, such as whether the import and export and the equipment to prevent small animals from entering the vents are complete, and whether the entry and exit channels are smooth.
Check whether there is water seepage and accumulation of water in the tunnels and manholes, remove the water when there is accumulation of water, and repair the leakage place, and report if it can't be repaired for the time being.
Check the condition of cables and joints in tunnels and manholes, and pay special attention to whether there is any oil leakage from cables and joints, whether the grounding is good, and if necessary, measure the grounding resistance and the potential of cables to prevent cable corrosion.
Check whether there are any bumps or serpentine abrasions on the cable bracket of the tunnel and manhole, and whether the bracket has fallen off.
Check the ventilation of the manhole cover and the manhole, whether there is any settlement and cracks in the manhole body, whether the position of the cables and joints are fixed normally, and whether the fireproof coating or fireproof tape on the cables and joints are intact.
Check whether the position of tunnel cables is normal, whether the joints have oil leakage, deformation, whether the temperature is normal, whether the fire prevention equipment is perfect and effective, and check whether the lighting of the tunnel is perfect.
Power wells, rows of pipes, tunnels, cable trenches, cable bridges, cable mezzanine and other ancillary equipment should be checked for metal components, such as brackets, grounding flat iron is rusted; for the spare rows of pipes should be dredged with special tools to check whether they have broken or not.
⑤Accessories and others
For cable terminals, the terminals should be checked whether there is any discharge phenomenon; whether the cable nameplate is intact; whether there is any cracking or ash accumulation in the heat-shrinkage, cold-shrinkage or prefabricated parts of the terminals of cross-linked cables; whether there is any heat or discharge phenomenon in the joints of the terminal lead wires, whether there is any de-welding of the grounding wires, and whether the outdoor cable protection tube of a section close to the ground is collided with by a car, and so on.
Multi-parallel cables should be checked for current distribution and the temperature of the cable sheath to prevent overloading of the cable or burning of the contacts due to poor contacts.
For single-core cables installed with protectors, after passing short-circuit currents, check the valves regularly for breakdown or burnt fusion. For GIS terminals special attention should be paid to check the barrel for discharge sound. Check the cable grounding box, cross-interconnection box, changeover box shell and grounding end without rust and corrosion, no water and moisture.
Single-core cable should monitor its metal sheath grounding line current, there is a large sudden change should be blackout for the outer sheath grounding current test to find the outer sheath damage.
3.Patrol cycle provisions
Regular inspection ：Cable line inspection should be combined with the results of the evaluation of the operating condition, and the inspection cycle should be adjusted appropriately
Non-scheduled inspection：
Cable lines should be fault patrol immediately after the occurrence of faults, with cross-interconnection of the cable line tripped, should be the same time on the line cross-interconnection box, grounding box patrol, but also to the same user power supply of other cable lines to carry out inspections to ensure the safety of power supply to the user.
Due to bad weather, natural disasters, external damage and other factors affecting the safety and stability of the power grid has special operational requirements, should be organized to carry out special inspections of operating personnel. Construction behavior around the cable line should be strengthened inspection, the cable line exposed to the excavation, should shorten the inspection cycle, if necessary, install temporary video monitoring device for real-time monitoring or arrange personnel to guard.
4.special patrol
Main Inspection Situation and Inspection Items
Cable lines are basically unaffected by the climate, but buried in the underground cable in the water after a long period of soaking is prone to moisture, insulation reduction, resulting in breakdown accidents. In the event of heavy rain, the cable should be special patrol.
Directly buried cable after the rain should be checked towards the area whether the drainage is smooth, collapse or surface temperature rise, if necessary, digging inspection.
Ground vibration after the cable is prone to distortion and deformation, cable tunnel deformation and collapse, cable joint deformation, damage to the cable. When there is a serious vibration of the ground or after an earthquake, the cable should be special patrol.
Tunnel laying should be checked in the tunnel drainage smooth situation, the four walls have no cracks, the bracket on the cable has no deformation. Cable joints, grounding boxes, terminal boxes are deformed and displaced.
When notified by the relevant municipal departments or notified by site personnel that there is construction above the cables or construction above the tunnel, the area where the cables are laid should be inspected on a daily basis. Check whether there are cracks and water seepage in the tunnel, whether the cable trench is deformed or has other debris, and whether the buried cable is dug out or damaged.
Precautions during special inspections
(1) When inspecting the cable trench during heavy rainfall, personnel should take measures to prevent flooding, and when the ground is vibrated, inspect the cables in the cable trench and confirm that there is no danger of collapse before going down the well for inspection.
(2) When inspecting at night, flashlight lighting should be sufficient. Pay attention to the head and feet.
(3) bad weather is generally not cable patrol, when the weather improves patrol cable, must pay attention to changes in the outdoor environment, retaining field, wall collapse, trees, towers toppling, water pits injection and other abnormal conditions may be harmful to the life of the equipment.
(4) rainy day special patrol cable to wear insulated boots, wear a raincoat, found that the cable has a fire, smoke, explosion, immediately leave the scene. Thunderstorms are not allowed to patrol.
5.fault patrol
Cable faults include ground faults, short circuit faults, and disconnection faults due to mechanical damage, lead wrap fatigue, cracking, and swelling, outdoor terminal head explosions, and cable intermediate joint explosions. In the event of a fault that causes the substation switch to trip, fault checking of the line is required.
For cable lines, in the event of a fault, should first understand the laying of the cable and cable direction, to understand the cable direction on whether there is construction or other special circumstances occur, easy to find out the point of failure as early as possible.
In the event of cable faults in cable tunnels, when entering the tunnel should check the oxygen content, there is an open fire, wear an anti-fog mask or positive pressure respirator, the use of fire extinguishers to extinguish the fire, if necessary, deactivate the power supply of the cable in the same tunnel, to prevent injury to the person.