ABB Relion 670 Series Applications Manual page 222

Section 9
Voltage protection
9.2.1 Identification
Function description
Two step overvoltage protection
9.2.2 Application
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
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.
216
IEC 61850
identification
OV2PTOV
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IEC 60617 ANSI/IEEE C37.2
identification device number
59
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SYMBOL-C-2U-SMALLER-THAN V2 EN-US
1MRK 511 401-UEN Rev. K
M17002-1 v8
M13799-3 v9
M13852-4 v10
Bay control REC670
Application manual