Electric power cables, as part of the power transmission lines, are widely used due to their low failure rate, reliability, and flexible outlet options. However, once a failure occurs, the repair process can be challenging and risky, thus requiring special attention during maintenance and testing.
Preparation Before Starting Work
Power cable outage work should be filled out using a Type 1 work order, while work that does not require an outage should use a Type 2 work order. Prior to commencing work, detailed review of the relevant route diagrams, arrangement diagrams, and concealed engineering drawings must be conducted. The cable names and tags must be meticulously checked for correspondence with the work order. Work can only begin once proper and reliable safety measures are confirmed.
2. Precautions to Take While on the Job
Ensure that cables requiring maintenance are confirmed during work hours.
Cables requiring maintenance can be categorized into two types:
Cables with terminal head failures and obvious surface defects. Such fault cables have distinct signs and are easy to identify.
(2) Cables without exposed fault points. For such faulty cables, in addition to cross-referencing documents and verifying the cable name, it is mandatory to use a cable identifier to distinguish them from other live cables in operation, especially when there are numerous cables in the same cross-section. It is crucial to strictly differentiate between the cables that require maintenance and those that are live. This also effectively prevents accidents caused by mislabeling cable tags, leading to incorrect identification and accidental cutting of live cables. Sawing cables must have reliable safety protection measures. Before cutting, it must be confirmed that the cable indeed needs to be severed and that it is de-energized. Then, after a grounding rod with a wooden handle (made of epoxy resin) is driven into the cable core, work can proceed. The person holding the wooden handle should wear insulating gloves and stand on an insulating mat, with special attention to ensuring a good ground connection for the rod. If the cable needs to be moved during work, it should be done carefully, avoiding forceful actions, and preventing damage to other live cables in operation. The cable ends must be installed according to the process requirements, ensuring quality and eliminating any potential accident risks. After cable repair, the phases at both ends of the cable should be carefully checked. First, remove the original phase color markings, then apply the correct phase color markings to prevent confusion between old and new phase colors.
Cautionary Notes for High-Voltage Testing
Cable high-voltage tests must strictly adhere to the "Safety Regulations for Electric Power Industry Work." Even under poor working conditions on-site, safety requirements must not be compromised in the slightest. Responsibilities must be clearly defined, and safety precautions should be detailedly arranged. The test site should be equipped with enclosed barriers or fences, with a "Caution: High Voltage Hazard!" sign hung outside, and a person should be on guard. Especially, the other end of the cable must also be monitored, and communication lines must remain open to prevent any emergencies. The test equipment and wiring must meet safety requirements, and operations must be standardized. Attention should be focused during the test, and operators should stand on insulating mats. Upon completion of the wiring or test, the test power source should be disconnected first, discharged, and the high-voltage equipment's high-voltage section should be short-circuited to ground. During high-voltage DC tests, the cable should be discharged to ground several times after each segment or at the end of the test, and then it can be touched.
4 Additional Points to Note
When opening a cable well or trench cover, measures to prevent traffic accidents should be taken. The well should be surrounded by a fence, equipped with clear warning signs, and obstacles should be set up to prevent vehicles from accidentally entering. At night, the cable well should be illuminated to prevent pedestrians or vehicles from falling into the well. Before entering the cable well, the polluted air inside should be removed. Workers inside the well should wear hard hats and take fire prevention, water prevention, and measures to prevent falling objects from high above. A designated person should be on guard at the well opening.
