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Overvoltage Protection in Electrical Power Transmission Line

Overvoltage Protection in Electrical Power Transmission Line

• An overvoltage alarm (Ph-N as measurement mode) shall be set at 110% with delay of 0.5 Sec (220kV and 400kV Lines). For detection of any PT secondary circuit issue. (i.e. floating neutral condition)

• Over voltage protection with two stage trip (Ph-Ph as measurement mode) shall be configured in 400 KV system only. It shall be configured in main-1 or main-2 distance protection schemes.

• The low stage (Stage-1) shall be set in the range 110-112% (typical 110%) with the time delay of 4-7 Sec. However, time grading of 1-3 second may be provided between over voltage relays of double circuit lines. Longest time delay shall be checked with expected operating time of over fluxing relay of the transformer to ensure disconnection of line before tripping of transformer.

• The high stage (Stage-2) shall be kept in the range 140 – 150% with time delay of 100-150 msec.

• The overvoltage setting is to be kept same for transmission line at both ends.


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