Equipment Protection, Such As For Motors, Generators, Reactors And Transformers; Equipment Protection, Capacitors; Power Supply Quality; High Impedance Grounded Systems - Hitachi Relion 670 Series Applications Manual

1MRK511407-UUS Rev. N
The time delay for the OV2PTOV (59) 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 grounded systems

In high impedance grounded systems, ground-faults cause a voltage increase in the non-faulty phases.
Two step overvoltage protection (OV2PTOV, 59) 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 ground-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-ground fundamental value, phase-to-phase
fundamental value, phase-to-ground RMS value or phase-to-phase RMS value.
Operation: Disabled/Enabled.
VBase (given in GlobalBaseSel): Base voltage phase to phase in primary kV. This voltage is used as
reference for voltage setting. OV2PTOV (59) measures selectively phase-to-ground voltages, or phase-
to-phase voltage chosen by the setting ConnType. The function will operate if the voltage gets lower than
the set percentage of VBase. When ConnType is set to PhN DFT or PhN RMS then the IED
automatically divides set value for VBase by √3. When ConnType is set to PhPh DFT or PhPh RMS then
set value for VBase is used. Therefore, always set VBase as rated primary phase-to-phase ground
voltage of the protected object. If phase to neutral (PhN) measurement is selected as setting, the
operation of phase-to-ground over voltage is automatically divided by sqrt3. This means operation for
phase-to-ground voltage over:
>
V (%)
EQUATION1713 V2 EN-US
Phasor measurement unit RES670
Application manual
×
VBase kV ( ) / 3
© 2017 - 2023 Hitachi Energy. All rights reserved
Section 9
Voltage protection
M13852-10 v3
M13852-13 v1
M13852-16 v1
M13852-19 v6
M13852-22 v11
(Equation 84)
157