ABB RELION 620 Series Technical Manual page 880

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Supervision functions

drop of the feeding auxiliary voltage system which can cause too low voltage values

over the TCS 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 TCS. The use of the

position indication is described earlier in this chapter.

Using power output contacts without trip circuit supervision

If TCS 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 TCS circuit is used.

GUID-0560DE53-903C-4D81-BAFD-175B9251872D V3 EN

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

internal resistor is disconnected

Incorrect connections and use of trip circuit supervision

Although the TCS 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 TCS

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 TCS circuit

when only one of the contacts is used.

1MRS757644 F

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