ABB Relion 670 Series Applications Manual page 225

1MRK 511 401-UEN Rev. K
HystAbsn : Absolute hysteresis set in % of UBase . The setting of this parameter is highly
dependent of the application. If the function is used as control for automatic switching of
reactive compensation devices the hysteresis must be set smaller than the voltage change
after switching of the compensation device.
9.3 Two step residual overvoltage protection ROV2PTOV
9.3.1 Identification
Function description
Two step residual overvoltage
protection
9.3.2 Application
Two step residual overvoltage protection ROV2PTOV is primarily used in high impedance
earthed distribution networks, mainly as a backup for the primary earth-fault protection of the
feeders and the transformer. To increase the security for different earth-fault related
functions, the residual overvoltage signal can be used as a release signal. The residual voltage
can be measured either at the transformer neutral or from a voltage transformer open delta
connection. The residual voltage can also be calculated internally, based on the measurement
of the three phase-to-earth voltages.
In high impedance earthed systems the residual voltage will increase in case of any fault
connected to earth. Depending on the type of fault and fault resistance the residual voltage
will reach different values. The highest residual voltage, equal to three times the phase-to-
earth voltage, is achieved for a single phase-to-earth fault. The residual voltage increases
approximately to the same level in the whole system and does not provide any guidance in
finding the faulted component. Therefore, ROV2PTOV is often used as a backup protection or
as a release signal for the feeder earth-fault protection.
9.3.3 Setting guidelines
All the voltage conditions in the system where ROV2PTOV performs its functions should be
considered. The same also applies to the associated equipment, its voltage withstand
capability and time characteristic.
All voltage-related settings are made as a percentage of a settable base voltage, which shall be
set to the primary nominal voltage (phase-phase) level of the power system or the high-
voltage equipment under consideration.
The time delay for ROV2PTOV is seldom critical, since residual voltage is related to earth faults
in a high-impedance earthed system, and enough time must normally be given for the primary
protection to clear the fault. In some more specific situations, where the residual overvoltage
protection is used to protect some specific equipment, the time delay is shorter.
Some applications and related setting guidelines for the residual voltage level are given below.
Bay control REC670
Application manual
IEC 61850
identification
ROV2PTOV
© Copyright 2017 Hitachi Power Grids. All rights reserved
IEC 60617 ANSI/IEEE C37.2
identification device number
59N
2(U0>)
IEC15000108 V1 EN-US
Section 9
Voltage protection
IP14546-1 v4
SEMOD54295-2 v6
M13809-3 v8
M13853-3 v8
219