Application - ABB 615 series Technical Manual

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Protection functions

Application

59N, 59G is designed to be used for ground-fault protection in isolated neutral, resistance

grounded or reactance grounded systems. In compensated networks, the pickup of the

function can be used to control the switching device of the neutral resistor. The function

can also be used for the back-up protection of feeders for busbar protection when a more

dedicated busbar protection would not be justified.

In compensated and isolated neutral systems, the system neutral voltage, that is, the

ground voltage, increases in case of any fault connected to ground. Depending on the type

of the fault and the fault resistance, the ground voltage reaches different values. The

highest ground voltage, equal to the phase-to-ground voltage, is achieved for a single-

phase ground fault. The ground voltage increases approximately the same amount in the

whole system and does not provide any guidance in finding the faulty component.

Therefore, this function is often used as a back-up protection or as a release signal for the

feeder ground-fault protection.

The protection can also be used for the ground-fault protection of generators and motors

and for the unbalance protection of capacitor banks.

The ground voltage can be calculated internally based on the measurement of the three-

phase voltage. This voltage can also be measured by a single-phase voltage transformer,

located between a transformer star point and ground, or by using an open-delta connection

of three single-phase voltage transformers.

59N,59G Input signals

59N,59G Output signals

Residual voltage

Block signal for activating the blocking mode

1MAC059074-MB A

615 series ANSI

Technical Manual

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