ABB Relion 670 series Applications Manual

• voltage controlled over-current
• voltage restrained over-current
In both applications a seal-in of the overcurrent function at under-voltage can be included
by configuration.
9.13.2.3 Undervoltage seal-in
In the case of a generator with a static excitation system, which receives its power from the
generator terminals, the magnitude of a sustained phase short-circuit current depends on
the generator terminal voltage. In case of a nearby multi-phase fault, the generator
terminal voltage may drop to quite low level, for example, less than 25%, and the
generator fault current may consequently fall below the pickup level of the overcurrent
protection. The short-circuit current may drop below the generator rated current after
0.5...1 s. Also, for generators with an excitation system not fed from the generator
terminals, a fault can occur when the automatic voltage regulator is out of service. In such
cases, to ensure tripping under such conditions, overcurrent protection with undervoltage
seal-in can be used.
To apply the VRPVOC(51V) function, the configuration is done according to figure
288.
As seen in the figure, the pickup of the overcurrent stage will enable the undervoltage
stage. Once enabled, the undervoltage stage will start a timer, which causes function
tripping, if the voltage does not recover above the set value. To ensure a proper reset, the
function is blocked two seconds after the trip signal is issued.
Trip output
OR
OR
t
ANSI12000183-1-en.vsd
VRPVOC (51V)
I3P*
I3P*
V3P*
V3P*
BLOCK
BLOCK
BLKOC
BLKOC
BLKUV
BLKUV
TRIP
TRIP
TROC
TROC
27 Trip
27 Trip
PICKUP
PICKUP
PU_OC
PU_OC
27 PU
27 PU
ANSI12000183 V1 EN
Figure 288: Undervoltage seal-in of current pickup
9.13.3 Setting guidelines
1MRK 506 369-UUS - Section 9
Current protection
Line distance protection REL670 2.2 ANSI 563
Application manual

ABB Relion 670 series Specifications

General

Brand	ABB
Model	Relion 670 series
Category	Protection Device
Language	English