ABB Relion RES670, Applications Manual

Page: 183 / 382

9.2.2 Application
M13799-3 v9
Two step overvoltage protection OV2PTOV is applicable in all situations, where
reliable detection of high voltage is necessary. OV2PTOV is used for supervision
and 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.
9.2.3 Setting guidelines
M13852-4 v10
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,
1MRK 511 407-UEN C
Section 9
Voltage protection
Phasor measurement unit RES670 2.2 IEC 177
Application manual