Four Steps to Maintaining Power Cables

Power cables are one of the indispensable materials for transmitting power energy, and are widely used in economic production. Once the cable fails, it will not only threaten the safe and stable operation of the power grid, but also cause economic losses to the enterprise, and in severe cases, it will cause a chain of destructive reactions. Therefore, how to quickly troubleshoot and solve faults and prevent the occurrence of faults has become a major issue in the power industry at present. The following editor will analyze the relevant problems in the operation and maintenance of power cables.

1. Test and acceptance of power cables and put them into operation

In the construction process, in addition to the handover test and preventive test, insulation test should also be carried out to identify and check the quality of cables and workmanship in all aspects of construction. Before laying, test on the cable tray to determine whether the cable is good or bad; after laying and before laying, test whether the cable is damaged during laying; test the cable head after construction to determine the quality of the cable head; Test before and after repair to determine the repair quality of the cable, the main contents of the inspection are as follows:

(1) The cables should be arranged neatly, the fixing and bending radius of the cables should comply with the design drawings and relevant regulations, the cables should be free from mechanical damage, and the signs should be installed complete, correct and clear. The terminals and intermediate joints of oil-impregnated paper insulated cables and oil-filled cables should be free of oil leakage;

(2) There should be no sundries in the cable trench and the tunnel, the cover plate of the cable trench should be complete, and the lighting, ventilation, drainage and other facilities in the tunnel should meet the design requirements;

(3) The marking pile of the directly buried cable should be consistent with the actual path, the spacing should meet the requirements, and the marking should be clear, firm and durable;

(4) The signs and night lighting devices on both sides of the underwater cable line and in the forbidden anchorage area shall meet the design requirements.

2. Precautions for cable line operation

(1) Do not overload or overheat for a long time. Therefore, do not ignore the monitoring of cable load current, external temperature, and joint temperature;

(2) The cable line feeder protection should not be put into reclosing. The faults of the cable lines are mostly permanent faults. If the reclosing action occurs, the accident will inevitably expand and threaten the stable operation of the power grid;

(3) After the feeder of the cable line is tripped, do not neglect the inspection of the cable. Focus on checking whether the cable path is excavated and whether the wires are damaged. If necessary, further inspection and judgment should be carried out through tests;

(4) Special attention should be paid to the operation and inspection of direct buried cables: the ground near the cable path cannot be excavated casually; the ground near the cable path is not allowed to scale heavy objects, corrosive substances, and temporary buildings; the cable path marker piles and protection facilities cannot be moved or removed casually ;

(5) The cable line must be re-tested before it can be put into use when it resumes operation after being deactivated.

3. Side-finding of cable faults

After the cable fails, the general side finding steps are as follows:

(1) Determine the nature of the fault: According to the phenomenon that occurs when the fault occurs and some simple tests, preliminarily judge the nature of the fault, determine whether the fault resistance is high resistance or low resistance, whether it is a flashover or a closed fault, whether it is a short circuit to ground, disconnection, Or a mixture of them, single-phase, two-phase or three-phase fault.

(2) Burn-through of the fault point: that is, the high-resistance fault or flashover fault is changed into a low-resistance fault through burn-through for rough measurement;

(3) Coarse measurement: use the instrument to measure the fault distance on one side of the cable, and use the cable line technical data to calculate the location of the fault point;

(4) Precise determination of the fault point: determine the precise location of the fault point by means of shock discharge acoustic measurement method, audio frequency induction method, and acousto-magnetic synchronous detection method.

Fourth, the operation and maintenance of cable lines

The operation and maintenance of cable lines is important to do three aspects of load monitoring, cable metal sleeve corrosion monitoring and insulation supervision. The main items include: conducting inspection and inspection of cable lines, preventive tests of cables, preventing external damage to cables, analyzing the causes of cable failures, cable Troubleshooting and wire fault repair, etc. If the cable is damaged, it is necessary to completely eliminate the cause of the fault before repairing or replacing the cable.