400kV disconnection sequence
400kV disconnection sequence
(OP)
Dear all. On iste we have a three winding step-up transformer connceted to the grid of 400kV via a disconnector and a circuit breaker. The disconnector is between Step-Up transformer and circuit breaker. When we de-energize from the 400kV grid we are instructed to open first the circuit breaker and then open the disconnector in a period of 10 seconds maximum after the opening of the circuit breaker. I cant quite understand this logic. Can you help me on that?






RE: 400kV disconnection sequence
The reconnection sequence should be in reverse mode, first open ground switches (if any), close phase switches and then close circuit breakers to connect the system. This should be consider even for energize unloaded transformers and transmission lines.
Even thought some switches may be equipped with attachment such as arching horn, Quick-break whip device or vacuum interrupters to provides limited load-break capabilities the primarily function of disconnect switch is for visual isolation of energized parts.
See the enclosed link video of a 115 kV disconnect switches equipped with some of the attachment described above:
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RE: 400kV disconnection sequence