Section 4 1MAC309294-MB F
Protection functions
208 RER620
Technical Manual
blocked and the timers are reset. the “Block TRIP output” mode, the function operates
normally but the TRIP output is not activated.
4.3.3.5 Application
59N 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 zero
sequence voltage, increases in case of any fault connected to ground. Depending on the
type of the fault and the fault resistance, the zero sequence voltage reaches different
values. The highest zero sequence voltage, equal to the phase-to-ground voltage, is
achieved for a single-phase ground fault. The zero sequence 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 zero sequence 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.
4.3.3.6 Signals
Table 217: 59N Input signals
Table 218: 59N Output signals
Name Type Default Description
VN SIGNAL 0 Zero sequence voltage
BLOCK BOOLEAN 0=False Block signal for activating the blocking mode
Name Type Description
TRIP BOOLEAN Trip
PICKUP BOOLEAN Pickup
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