ABB RELION 611 Series Technical Manual page 343

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1MRS757454 D

Technical Manual

A070972 V4 EN

Incorrect connection of trip-circuit supervision

A connection of three protection relays with a double pole trip circuit is shown in the

following figure. Only the protection relay R3 has an internal TCS circuit. In order to

test the operation of the protection relay R2, but not to trip the circuit breaker, the

upper trip contact of the protection relay R2 is disconnected, as shown in the figure,

while the lower contact is still connected. When the protection relay R2 operates, the

coil current starts to flow through the internal resistor of the protection relay R3 and

the resistor burns immediately. As proven with the previous examples, both trip

contacts must operate together. Attention should also be paid for correct usage of the

trip-circuit supervision while, for example, testing the protection relay.

Supervision functions