Analysis and Treatment for Three-phase Current Imbalance in the 4 th String Line of 500 kV Part
Ting Wei substation is one of the 500 kV main network supporting points of the Shanghai Power Grid. 500 kV part adopts the 3/2 connection mode with a total of 7 string and 8 outgoing lines, and uses hybrid gas insulated switchgear （HGIS）. In view of the serious three-phase current imbalance, even phase- deficient operation for the 4th string line, failure analysis and troubleshooting are carried out. The main reason is the HGIS disconnector linkage deviation, which results in the disconnector closing not in place, the moving contact and stationary contact not full engagement. Part of the contact surface are melt due to overheating, resulting in increased contact resistance, and finally zero current. After a timely process by the manufacturers, the line is restored to normal operation.
NETL
NSTL
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