ABB 615 series Technical Manual page 848

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Supervision functions

because of the voltage drop in R

feeding auxiliary voltage system which can cause too low voltage values over the TCM

contact. In this case, erroneous alarming can occur.

At lower (<48 V DC) auxiliary circuit operating voltages, it is recommended to use the

circuit breaker position to block unintentional operation of TCM. The use of the position

indication is described earlier in this chapter.

Using power output contacts without trip circuit supervision

If TCM is not used but the contact information of corresponding power outputs are

required, the internal resistor can be by-passed. The output can then be utilized as a normal

power output. When bypassing the internal resistor, the wiring between the terminals of

the corresponding output X100:16-15(PO3) or X100:21-20(PO4) can be disconnected.

The internal resistor is required if the complete TCM circuit is used.

GUID-548E2DC1-D16E-4BC2-803F-96FB5021DAC2-ANSI V1 EN

Connection of a power output in a case when TCM is not used and the

internal resistor is disconnected

Incorrect connections and use of trip circuit supervision

Although the TCM circuit consists of two separate contacts, it must be noted that those are

designed to be used as series connected to guarantee the breaking capacity given in the

technical manual of the protection relay. In addition to the weak breaking capacity, the

internal resistor is not dimensioned to withstand current without a TCM circuit. As a

result, this kind of incorrect connection causes immediate burning of the internal resistor

when the circuit breaker is in the close position and the voltage is applied to the trip circuit.

The following figure shows incorrect usage of a TCM circuit when only one of the

contacts is used.

and the operating coil or even voltage drop of the

1MAC059074-MB A

615 series ANSI

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