Figure 268: 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
1MRS758755 C
532 REC615 & RER615
Technical Manual
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