ABB 615 series Technical Manual page 849

1MAC059074-MB A
615 series ANSI
Technical Manual
A070972-ANSI V1 EN
Figure 432: 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 TCM 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.
Section 6
Supervision functions
843