Hitachi Relion 670 Series Applications Manual page 193

1MRK506375-UEN Rev. N
9.2.4 Setting guidelines
The parameters for two step overvoltage protection (O2RWPTOV) are set via the local HMI or
Protection and Control Manager PCM600.
All the voltage conditions in the system where O2RWPTOV performs its functions should be
considered. The same also applies to the associated equipment, its voltage and time characteristic.
There are wide applications where general overvoltage functions are used. All voltage related
settings are made as a percentage of a settable base primary voltage, which is normally set to the
nominal voltage level (phase-to-phase) of the power system.
The time delay for the O2RWPTOV can sometimes be critical and related to the size of the
overvoltage - a power system or a high voltage component can withstand smaller overvoltages for
some time, but in case of large overvoltages the related equipment should be disconnected more
rapidly.
Some applications and related setting guidelines for the voltage level are given below:
9.2.4.1 Equipment protection, transformers
High voltage will cause overexcitation of the core and deteriorate the winding insulation. The setting
has to be well above the highest occurring "normal" voltage and well below the highest acceptable
voltage for the equipment.
9.2.4.2 Power supply quality
The setting has to be well above the highest occurring "normal" voltage and below the highest
acceptable voltage, due to regulation, good practice or other agreements.
9.2.4.3 The following settings can be done for the two step overvoltage
protection
Common base IED values for primary current (IBase), primary voltage (UBase) and primary power
(SBase) are set in the global base values for settings function GBASVAL.
GlobalBaseSel: To select GBASVAL function for reference of base values.
ConnType: To set whether the measurement shall be phase-to-earth fundamental value, phase-to-
phase fundamental value, phase-to-earth true RMS value or phase-to-phase true RMS value.
Operation: For two step overvoltage protection Off/On.
UBase (given in GlobalBaseSel): Set as rated phase-to-phase voltage in primary kV. This voltage is
used as reference for voltage setting. O2RWPTOV measures selectively phase-to-earth voltages, or
phase-to-phase voltage chosen by the setting ConnType. The function will operate if the voltage gets
higher than the set percentage of UBase. When ConnType is set to PhN DFT or PhN RMS, the IED
automatically divides set value of UBase by 2. When ConnType is set to PhPh DFT or PhPh RMS,
set value of UBase is used. Therefore, always set UBase as rated primary phase-to-phase voltage of
the protected object. This means operation for phase-to-earth voltage over:
and operation for phase-to-phase voltage over:
>
U (%) UBase(kV)
EQUATION1993 V1 EN-US
Railway application RER670
Application manual
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Section 9
Voltage protection
M13852-4 v10
M13852-10 v3
M13852-16 v1
M13852-22 v11
(Equation 66)
187