ABB 615 Series - Application

4.5.3.5 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.
4.5.3.6 Signals
Table 532: 59N,59G Input signals
Name
Type Default Description
VG/V0 SIGNAL 0 Residual voltage
BLOCK BOOLEAN 0=False Block signal for activating the blocking mode
Table 533: 59N,59G Output signals
Name
Type Description
TRIP BOOLEAN Trip
PICKUP BOOLEAN Pickup
Section 4 1MAC059074-MB A
Protection functions
630 615 series ANSI
Technical Manual