4.5.3.6 Application
ROVPTOV is designed to be used for earth-fault protection in isolated neutral,
resistance earthed or reactance earthed systems. In compensated networks,
starting 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 residual voltage, increases in case of any fault connected to earth. Depending on
the type of the fault and the fault resistance, the residual voltage reaches different
values. The highest residual voltage, equal to the phase-to-earth voltage, is achieved
for a single-phase earth fault. The residual 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 backup protection or
as a release signal for the feeder earth-fault protection.
The protection can also be used for the earth-fault protection of generators and
motors and for the unbalance protection of capacitor banks.
The residual 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 earth, or by using an
open-delta connection of three single-phase voltage transformers.
4.5.3.7 Signals
ROVPTOV Input signals
Table 805: ROVPTOV Input signals
Name Type Default Description
URES SIGNAL - Residual voltage
BLOCK BOOLEAN 0=False Block signal for acti-
vating the blocking
mode
ROVPTOV Output signals
Table 806: ROVPTOV Output signals
Name Type Description
OPERATE BOOLEAN Operate
START BOOLEAN Start
4.5.3.8 ROVPTOV Settings
Table 807: ROVPTOV Group settings (Basic)
Parameter
Values (Range) Unit Step Default Description
Start value 0.010...1.000 xUn 0.001 0.030 Residual overvolt-
age start value
Operate delay time 40...300000 ms 1 40 Operate delay time
1MRS759142 F Protection functions
REX640
Technical Manual
869
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