Voltage Protection - ABB RET670 Applications Manual

1MRK504116-UUS C
3.8
3.8.1
3.8.1.1
Application manual

Voltage protection

Two step undervoltage protection UV2PTUV (27)
Function description
Two step undervoltage protection
Application
Two-step undervoltage protection function (UV2PTUV ,27) 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 (27) 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
(27) 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 (27) 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 and setting hysteresis to allow applications to control reactive
load.
UV2PTUV (27) is used to disconnect apparatuses, like electric motors, which will be
damaged when subject to service under low voltage conditions. UV2PTUV (27) 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-ground faults (unsymmetrical voltage decrease).
UV2PTUV (27) prevents sensitive equipment from running under conditions that
could cause their overheating and thus shorten their life time expectancy. In many
IEC 61850 IEC 60617
identification identification
UV2PTUV
3U<
SYMBOL-R-2U-GREATER-THAN
V2 EN
Section 3
IED application
ANSI/IEEE C37.2
device number
27
509