When using high-voltage fuses, what should we do if the fuse wire is blown? How can we check the cause?

       (1) Reasons for and inspection of one-phase fuse blowing:

       1) The fuse has mechanical damage or poor contact;

       2) The winding of the fused phase has a severe inter-turn short circuit;

       3) Metallic grounding or arc short circuit occurs in the load side line of the high-voltage current-limiting fuse and the lead wire of the transformer insulation bushing.

       After the fuse of one phase is blown, the transformer should be powered off for inspection. If no abnormalities are found, the fuse can be replaced. The transformer should be tested for power-on under no-load conditions. After the operation status of the transformer is monitored to be normal, it can be operated with load.

       (2) Reasons for and inspection of two-phase fuse failure:

       1) A two-phase metallic short circuit or arc short circuit occurs at the high-voltage wall bushing of the load side line or the primary side insulation porcelain of the transformer, resulting in fusing;

       2) Two phases in the primary winding of the transformer experience inter-phase short circuit or severe inter-turn short circuit in the two-phase winding;

       3) There is a two-phase short circuit at the secondary side lead of the transformer or a two-phase short circuit in the secondary side load, and the secondary side protection switch fails to operate.

       After the two-phase fuse is blown, first check the high-voltage lead and its insulation for any signs of discharge. For the high-voltage load switch, also observe and check the transformer for any signs of overheating, deformation, and oil spraying. Internal faults in the transformer can be determined by measuring the DC resistance of the three-phase windings with a DC bridge or measuring the insulation resistance. If it is confirmed that there is an internal fault in the transformer, it should undergo major repairs;

       (3) Reasons for and inspection of three-phase fuse failure:

       1) Three-phase metallic short circuit or three-phase arcing short circuit;

       2) The primary or secondary side of the transformer (load side of the drop-out fuse) line or the transformer experiences a three-phase winding short circuit or a three-phase short circuit occurs in the lead;

       3) Severe damage to the insulation between transformer core sheets or prolonged overload leading to overheating, resulting in the destruction of the transformer.

       After the three-phase fuse is blown, it is necessary to conduct a power outage inspection on the transformer. Only after troubleshooting can the fuse be replaced and power be tested. After no-load operation, it can be put into operation with load. The inspection and handling situation should be recorded in detail.

       Inspection method for fuse failure:

       After the fuse is blown, the power should be cut off for inspection. Check the primary and secondary leads, primary and secondary insulating sleeves, cable heads, etc. of the transformer for any terminal faults. If there are no faults, use a megohmmeter to check the insulation resistance of the line. Line inspection: Use a megohmmeter to check the insulation resistance of the transformer, and use a multimeter and bridge to measure the DC resistance of the windings. If there is a gas relay, analyze it based on its operation. If necessary, test the transformer oil, and perform a core inspection on the transformer as required.