ABB Relion 670 Series Applications Manual page 223

1MRK 511 401-UEN Rev. K
The time delay for the OV2PTOV 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:
The hysteresis is for overvoltage functions very important to prevent that a transient voltage
over set level is not "sealed-in" due to a high hysteresis. Typical values should be ≤ 0.5%.
9.2.3.1 Equipment protection, such as for motors, generators, reactors and
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.
9.2.3.2 Equipment protection, capacitors
High voltage will deteriorate the dielectricum and the insulation. The setting has to be well
above the highest occurring "normal" voltage and well below the highest acceptable voltage
for the capacitor.
9.2.3.3 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.
9.2.3.4 High impedance earthed systems
In high impedance earthed systems, earth-faults cause a voltage increase in the non-faulty
phases. Two step overvoltage protection (OV2PTOV) is used to detect such faults. The setting
must be above the highest occurring "normal" voltage and below the lowest occurring voltage
during faults. A metallic single-phase earth-fault causes the non-faulted phase voltages to
increase a factor of √3.
9.2.3.5 The following settings can be done for the two step overvoltage
protection
ConnType : Sets whether the measurement shall be phase-to-earth fundamental value, phase-
to-phase fundamental value, phase-to-earth RMS value or phase-to-phase RMS value.
Operation : Off / On .
UBase (given in GlobalBaseSel ): Base voltage phase to phase in primary kV. This voltage is used
as reference for voltage setting. OV2PTOV measures selectively phase-to-earth voltages, or
phase-to-phase voltage chosen by the setting
voltage gets lower than the set percentage of
RMS then the IED automatically divides set value for UBase by √3. When ConnType is set to
PhPh DFT or PhPh RMS then set value for UBase is used. Therefore, always set UBase as rated
primary phase-to-phase voltage of the protected object. If phase to neutral (PhN)
measurement is selected as setting, the operation of phase-to-earth over voltage is
automatically divided by sqrt3. This means operation for phase-to-earth voltage over:
>
U (%)
Bay control REC670
Application manual
×
UBase kV ( ) / 3
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ConnType . The function will operate if the
UBase . When ConnType is set to PhN DFT or PhN
Section 9
Voltage protection
M13852-10 v3
M13852-13 v1
M13852-16 v1
M13852-19 v6
M13852-22 v10
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