Frequency Protection; Secondary System Supervision - ABB REC650 Product Manual

ABB
Bay control REC650
Product version: 1.1
transformers or measures it from a single
voltage input transformer fed from an open
delta or neutral point voltage transformer.
ROV2PTOV has two voltage steps, where
step 1 can be set as inverse or definite time
delayed. Step 2 is always definite time delayed.
Loss of voltage check LOVPTUV
Loss of voltage check (LOVPTUV) is suitable
for use in networks with an automatic system
restoration function. LOVPTUV issues a three-
pole trip command to the circuit breaker, if
all three phase voltages fall below the set
value for a time longer than the set time and
the circuit breaker remains closed.

7. Frequency protection

Underfrequency protection SAPTUF
Underfrequency occurs as a result of lack of
generation in the network.
Underfrequency protection SAPTUF is used
for load shedding systems, remedial action
schemes, gas turbine startup and so on.
SAPTUF is provided with an undervoltage
blocking.
Overfrequency protection SAPTOF
Overfrequency protection function SAPTOF is
applicable in all situations, where reliable
detection of high fundamental power system
frequency is needed.
Overfrequency occurs at sudden load drops
or shunt faults in the power network. Close
to the generating plant, generator governor
problems can also cause over frequency.
SAPTOF is used mainly for generation
shedding and remedial action schemes. It is
also used as a frequency stage initiating load
restoring.
SAPTOF is provided with an undervoltage
blocking.
1MRK 511 249-BEN -
Issued: February 2011
Rate-of-change frequency
protection SAPFRC
Rate-of-change frequency protection function
(SAPFRC) gives an early indication of a main
disturbance in the system. SAPFRC can be
used for generation shedding, load shedding
and remedial action schemes. SAPFRC can
discriminate between positive or negative
change of frequency.
SAPFRC is provided with an undervoltage
blocking.
8. Secondary system
supervision
Current circuit supervision
CCSRDIF
Open or short circuited current transformer
cores can cause unwanted operation of many
protection functions such as differential,
earth-fault current and negative-sequence
current functions.
It must be remembered that a blocking of
protection functions at an occurrence of open
CT circuit will mean that the situation will
remain and extremely high voltages will
stress the secondary circuit.
Current circuit supervision (CCSRDIF)
compares the residual current from a three
phase set of current transformer cores with
the neutral point current on a separate input
taken from another set of cores on the
current transformer.
A detection of a difference indicates a fault in
the circuit and is used as alarm or to block
protection functions expected to give
unwanted tripping.
Fuse failure supervision SDDRFUF
The aim of the fuse failure supervision
function (SDDRFUF) is to block voltage
measuring functions at failures in the
secondary circuits between the voltage
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