Residual Overvoltage Protection Rovptov - ABB REF615 Applications Manual

1MRS756378 D
5.5.3
5.5.3.1
5.5.3.2
5.5.3.3
REF615
Application Manual

Residual overvoltage protection ROVPTOV

Identification
Table 71: Function identification
IEC 61850 identification:
IEC 60617 identification:
ANSI/IEEE C37.2 device number:
Functionality
The residual overvoltage protection ROVPTOV is used in distribution networks
where the residual overvoltage can reach non-acceptable levels, for example, in high
impedance earthing.
The function starts when the residual voltage exceeds the set limit. ROVPTOV
operates with the definite time (DT) characteristic.
The function contains a blocking functionality. It is possible to block function outputs,
the definite timer or the function itself, if desired.
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 back-up protection of feeders for busbar protection when
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-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 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.
Protection functions
ROVPTOV
U0>
59G
Section 5
169