8.5.2 Application
SEMOD171876-4 v3
The trip of the circuit breaker at a prolonged loss of voltage at all the three phases is normally
used in automatic restoration systems to facilitate the system restoration after a major
blackout. Loss of voltage check (LOVPTUV) generates a TRIP signal only if the voltage in all the
three phases is low for more than the set time. If the trip to the circuit breaker is not required,
LOVPTUV is used for signallization only through an output contact or through the event
recording function.
8.5.3 Setting guidelines
SEMOD171929-4 v5
Loss of voltage check (LOVPTUV) is in principle independent of the protection functions. It
requires to be set to open the circuit breaker in order to allow a simple system restoration
following a main voltage loss of a big part of the network and only when the voltage is lost
with breakers still closed.
All settings are in primary values or per unit. Set operate level per phase to typically 70% of the
global parameter
UBase
level. Set the time delay
tTrip
=5-20 seconds.
8.5.3.1 Advanced users settings
SEMOD171929-8 v4
For advanced users the following parameters need also to be set. Set the length of the trip
pulse to typical
tPulse
=0.15 sec. Set the blocking time
tBlock
to block Loss of voltage check
(LOVPTUV), if some but not all voltage are low, to typical 5.0 seconds and set the time delay
for enabling the function after restoration
tRestore
to 3 - 40 seconds.
1MRK 511 358-UEN A Section 8
Voltage protection
189
Application manual
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