ABB RELION REX640 Technical Manual page 869

Protection and control

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1MRS759142 F

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.

ROVPTOV Input signals

Table 805: ROVPTOV Input signals

ROVPTOV Output signals

Table 806: ROVPTOV Output signals

ROVPTOV Settings

Table 807: ROVPTOV Group settings (Basic)

Values (Range)

0.010...1.000

Operate delay time

Technical Manual

Protection functions

Residual voltage

Block signal for acti-

vating the blocking

Residual overvolt-

age start value

Operate delay time