ABB Relion 670 Series Applications Manual page 224

Section 9
Voltage protection
IntBlkStValn : Voltage level under which the blocking is activated set in % of VBase . This setting
must be lower than the setting
that is, about 10%.
tBlkUVn : Time delay to block the undervoltage step n when the voltage level is below IntBlkStValn ,
given in s. It is important that this delay is shorter than the trip time delay of the undervoltage
protection step.
9.2 Two step overvoltage protection OV2PTOV (59)
9.2.1 Identification
Function description
Two step overvoltage protection
9.2.2 Application
Two step overvoltage protection OV2PTOV (59) is applicable in all situations, where reliable
detection of high voltage is necessary. OV2PTOV (59) 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
(59) is applied to power system elements, such as generators, transformers, motors and power
lines in order to detect high voltage conditions. OV2PTOV (59) is used in combination with low
current signals, to identify a transmission line, open in the remote end. In addition to that,
OV2PTOV (59) 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 (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).
218
Pickupn . As switch of shall be detected the setting can be very low,
IEC 61850
identification
OV2PTOV
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IEC 60617 ANSI/IEEE C37.2
identification device number
59
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Application manual