Setting Guidelines - ABB RET670 Applications Manual

Section 3
IED application
3.8.2.2
516
thereby decreasing the voltage. The function has a high measuring accuracy and
hysteresis setting to allow applications to control reactive load.
OV2PTOV (59) is used to disconnect apparatuses, like electric motors, which will be
damaged when subject to service under high voltage conditions. It deals with high
voltage conditions at power system frequency, which can be caused by:
1. Different kinds of faults, where a too high voltage appears in a certain power
system, like metallic connection to a higher voltage level (broken conductor
falling down to a crossing overhead line, transformer flash over fault from the high
voltage winding to the low voltage winding and so on).
2. Malfunctioning of a voltage regulator or wrong settings under manual control
(symmetrical voltage decrease).
3. Low load compared to the reactive power generation (symmetrical voltage decrease).
4. Ground-faults in high impedance grounded systems causes, beside the high
voltage in the neutral, high voltages in the two non-faulted phases, (unsymmetrical
voltage increase).
OV2PTOV (59) prevents sensitive equipment from running under conditions that
could cause their overheating or stress of insulation material, and, thus, shorten their
life time expectancy. In many cases, it is a useful function in circuits for local or
remote automation processes in the power system.

Setting guidelines

The parameters for Two step overvoltage protection (OV2PTOV ,59) are set via the
local HMI or PCM600.
All the voltage conditions in the system where OV2PTOV (59) performs its functions
should be considered. The same also applies to the associated equipment, its voltage
and time characteristic.
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:
1MRK504116-UUS C
Application manual