power cable is widely used because of its low failure probability

As a part of power line, power cable is widely used because of its low failure probability, safety and reliability and flexible outgoing line. However, in case of failure, maintenance is difficult and dangerous, so special attention should be paid to maintenance and test.
1. Preparation before work
One type of work ticket shall be filled in for power cable power outage, and the second type of work ticket shall be filled in for work without power outage. Before work, the relevant route map, arrangement drawing and drawings of concealed works shall be consulted in detail. The cable name and signboard must be checked in detail to see whether they are consistent with those written in the work ticket. The work can be started only after the safety measures are correct and reliable.
 
2. Precautions in work
The cables to be repaired must be confirmed during operation.
There are two kinds of cables to be repaired:
(1) Cables with terminal head failure and obvious fault points on the surface of cable body. This kind of faulty cable has obvious fault signs and is easy to confirm.  
(2) Cables with no fault points exposed on the cable surface. For this kind of faulty cable, in addition to checking the data and verifying the cable name, it must also be identified with the cable identifier to distinguish it from other live cables in operation, especially when there are many cables in the same section, it is particularly important to strictly distinguish the cables to be repaired from other live cables. At the same time, it can also effectively prevent the wrong cable from being recognized due to the wrong hanging of the cable label, resulting in the accident of mistakenly disconnecting the live cable. Reliable safety protection measures must be taken for sawing cables. Before sawing off the cable, it must be confirmed that it is the cable to be cut off and the cable has no electricity. Then, it can work only after the grounded iron brazing rod with wooden handle (epoxy resin handle) is nailed into the cable core. The person holding the wooden handle shall wear insulating gloves and stand on the insulating pad, and special attention shall be paid to ensure the good grounding of iron brazing. If it is necessary to move the cable during work, be careful and avoid acting recklessly to prevent damage to other running cables. The cable head must be installed according to the process requirements to ensure the quality and avoid potential accidents. After the cable is repaired, the phase at both ends of the cable shall be carefully checked. The original phase color mark shall be removed first, and then the correct phase color mark shall be put on to prevent the new and old phase colors from being confused.
 
3 precautions during high voltage test
The high voltage test of cable shall strictly comply with the safety work regulations of electric power industry. Even in the case of poor on-site working conditions, the requirements for safety shall not be reduced at all. The division of labor must be clear, and the safety precautions shall be arranged in detail. A closed barrier or fence shall be installed at the test site, and the "stop, high voltage danger" shall be hung outward Sign board, and send someone to guard. In particular, the other end of the cable must also be guarded by personnel and keep the communication unblocked to prevent emergencies. The test device and wiring shall meet the safety requirements, and the operation must be standardized. Attention shall be focused during the test, and the operator shall stand on the insulating pad. When changing the line or at the end of the test, disconnect the test power supply, discharge, and short-circuit the high-voltage part of the high-voltage equipment to ground. During the high-voltage DC test, the cable shall be discharged to the ground several times and short circuited to ground at the end of each paragraph or test, and then the cable can be contacted.
 
4. Other precautions  
When opening the cover plate of cable well or cable trench, measures shall be taken to prevent traffic accidents. Fences shall be arranged around the well, obvious warning signs shall be made, and obstacles to prevent vehicles from entering by mistake shall be set. At night, the cable well shall be illuminated to prevent pedestrians or vehicles from falling into the well. Before entering the cable well, the turbid gas in the well shall be removed. The workers in the well shall wear safety helmets and take measures to prevent fire, water and falling objects. The wellhead shall be guarded by a specially assigned person.