ABB REC650 Applications Manual page 162

Section 7
Voltage protection
156
There is a very wide application area where general overvoltage functions are used. All
voltage related settings are made as a percentage of a settable base primary voltage, which
normally is set to the nominal voltage level (phase-to-phase) of the power system or the
high voltage equipment under consideration.
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:
Equipment protection, such as for motors, generators, reactors and
transformers
High voltage can cause overexcitation of the core and deteriorate the winding insulation.
The setting must be above the highest occurring "normal" voltage and below the highest
acceptable voltage for the equipment.
Equipment protection, capacitors
High voltage can deteriorate the dielectricum and the insulation. The setting must be
above the highest occurring "normal" voltage and below the highest acceptable voltage
for the capacitor.
High impedance grounded systems
In high impedance grounded systems, ground-faults cause a voltage increase in the non-
faulty phases. OV2PTOV (59) can be 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.
The following settings can be done for Two step overvoltage protection
GlobalBaseSel: Selects the global base value group used by the function to define (IBase),
(VBase) and (SBase).
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 .
OV2PTOV (59) measures the phase-to-ground voltages, or phase-to-phase voltages as
selected. The function will operate if the voltage gets higher than the set percentage of the
global set base voltage VBase. This means operation for phase-to-ground voltage over:
1MRK 511 286-UUS A
Application manual