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How do you separate the ANSI 50 (Instantaneous phase overcurrent) from the ANSI 51 (delayed phase overcurrent) protection?

The ANSI 50/51 protection option in SEPAM relays combine both ANSI 50 instantaneous phase overcurrent protection and ANSI 51 delayed phase overcurrent protection.

In order to activate ANSI 50 protection, an instantaneous delay of 50ms must be set for the time delay. This is the lowest response time of the relay to a short-circuit fault. This includes Operating time + Overshoot time.


In order to activate ANSI 51 protection, a delay greater than 50ms must be set for the same parameter setting time delay. This will allow the end-user to use ANSI 51 delayed phase overcurrent protection.

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