Functionality - ABB REF615 Applications Manual

1MRS756378 D
5.5.1.2
5.5.1.3
5.5.2
5.5.2.1
REF615
Application Manual

Functionality

The three-phase overvoltage protection PHPTOV is applied on power system
elements, such as generators, transformers, motors and power lines to protect the
system from excessive voltages that could damage the insulation and cause insulation
breakdown. The three-phase overvoltage function includes a settable value for the
detection of overvoltage either in a single phase, two phases or three phases.
PHPTOV includes both definite time (DT) and inverse definite minimum time
(IDMT) operate time characteristics for the delay of the trip.
The function contains a blocking functionality. It is possible to block function outputs,
timer or the function itself, if desired.
Application
Overvoltage in a network occurs either due to the transient surges on the network or
due to prolonged power frequency overvoltages. Surge arresters are used to protect
the network against the transient overvoltages, but the IED protection function is used
to protect against power frequency overvoltages.
The power frequency overvoltage may occur in the network due to the contingencies
such as:
• the defective operation of the automatic voltage regulator when the generator is
in isolated operation.
• operation under manual control with the voltage regulator out of service. A
sudden variation of load, in particular the reactive power component, will give
rise to a substantial change in voltage because of the inherent large voltage
regulation of a typical alternator.
• sudden loss of load due to tripping of outgoing feeders, leaving the generator
isolated or feeding a very small load. This causes a sudden rise in the terminal
voltage due to the trapped field flux and overspeed.
If a load sensitive to overvoltage remains connected, it leads to the equipment damage.
It is essential to provide power frequency overvoltage protection, in the form of time
delayed element, either IDMT or DT to prevent equipment damage.
Undervoltage protection PHPTUV
Identification
Table 70: Function identification
IEC 61850 identification
IEC 60617 identification
ANSI/IEEE C37.2 device number
Protection functions
PHPTUV
3U<
27
Section 5
167