ABB Relion REQ650, Applications Manual

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Section 7 Voltage protection
7.1 Two step undervoltage protection UV2PTUV
7.1.1 Identification
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Two step undervoltage protection UV2PTUV
3U<
SYMBOL-R-2U-GREATER-THAN
V2 EN
27
7.1.2 Application
Two-step undervoltage protection function (UV2PTUV) is applicable in all
situations, where reliable detection of low phase voltages is necessary. It is used also
as a supervision and fault detection function for other protection functions, to increase
the security of a complete protection system.
UV2PTUV is applied to power system elements, such as generators, transformers,
motors and power lines in order to detect low voltage conditions. Low voltage
conditions are caused by abnormal operation or fault in the power system. UV2PTUV
is used in combination with overcurrent protections, either as restraint or in logic "and
gates" of the trip signals issued by the two functions. Other applications are the
detection of "no voltage" condition, for example, before the energization of a HV line
or for automatic breaker trip in case of a blackout. UV2PTUV is also used to initiate
voltage correction measures, like insertion of shunt capacitor banks to compensate for
reactive load and thereby increasing the voltage. The function has a high measuring
accuracy to allow applications to control reactive load.
UV2PTUV is used to disconnect apparatuses, like electric motors, which will be
damaged when subject to service under low voltage conditions. UV2PTUV deals with
low voltage conditions at power system frequency, which can be caused by the
following reasons:
1. Malfunctioning of a voltage regulator or wrong settings under manual control
(symmetrical voltage decrease).
2. Overload (symmetrical voltage decrease).
3. Short circuits, often as phase-to-earth faults (unsymmetrical voltage decrease).
1MRK 505 291-UEN A
Section 7
Voltage protection
155
Application manual