Setting Guidelines - ABB REG670 Applications Manual

1MRK 502 071-UEN -
10.2.3
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
detection of abnormal conditions, which, in combination with other protection
functions, increase the security of a complete protection system.
High overvoltage conditions are caused by abnormal situations in the power system.
OV2PTOV is applied to power system elements, such as generators, transformers,
motors and power lines in order to detect high voltage conditions. OV2PTOV is used
in combination with low current signals, to identify a transmission line, open in the
remote end. In addition to that, OV2PTOV is also used to initiate voltage correction
measures, like insertion of shunt reactors, to compensate for low load, and thereby
decreasing the voltage. The function has a high measuring accuracy and hysteresis
setting to allow applications to control reactive load.
OV2PTOV 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. Earth-faults in high impedance earthed systems causes, beside the high voltage in
the neutral, high voltages in the two non-faulted phases, (unsymmetrical voltage
increase).
OV2PTOV 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) are set via the local
HMI or PCM600.
All the voltage conditions in the system where OV2PTOV 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 or the
high voltage equipment under consideration.
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
Section 10
Voltage protection
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