Frequency Protection; Secondary System Supervision - ABB REC650 Product Manual

Bay control REC650 ANSI
Product version: 1.2
voltage. When triggered, the function will cause an
alarm, switch in reactors, or switch out capacitor
banks.
OV2PTOV (59) has two voltage steps, where step 1
can be set as inverse or definite time delayed. Step
2 is always definite time delayed.
OV2PTOV (59) has an extremely high reset ratio to
allow settings close to system service voltage.
Two step residual overvoltage protection
ROV2PTOV (59N)
Residual voltages may occur in the power system
during ground faults.
Two step residual overvoltage protection
ROV2PTOV (59N) function calculates the residual
voltage from the three-phase voltage input
transformers or measures it from a single voltage
input transformer fed from a broken delta or neutral
point voltage transformer.
ROV2PTOV (59N) 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 (27)
Loss of voltage check (LOVPTUV, 27) is suitable for
use in networks with an automatic system
restoration function. LOVPTUV (27) 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 (81)
Underfrequency occurs as a result of a lack of
sufficient generation in the network.
Underfrequency protection SAPTUF (81) is used for
load shedding systems, remedial action schemes,
gas turbine startup and so on.
SAPTUF (81) is also provided with undervoltage
blocking.
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Overfrequency protection SAPTOF (81)
Overfrequency protection function SAPTOF (81) is
applicable in all situations, where reliable detection
of high fundamental power system frequency is
needed.
Overfrequency occurs because of sudden load
drops or shunt faults in the power network. Close to
the generating plant, generator governor problems
can also cause over frequency.
SAPTOF (81) is used mainly for generation shedding
and remedial action schemes. It is also used as a
frequency stage initiating load restoring.
SAPTOF (81) is provided with an undervoltage
blocking.
Rate-of-change frequency protection SAPFRC (81)
Rate-of-change frequency protection function
(SAPFRC,81) gives an early indication of a main
disturbance in the system. SAPFRC (81) can be
used for generation shedding, load shedding and
remedial action schemes. SAPFRC (81) can
discriminate between positive or negative change of
frequency.
SAPFRC (81) is provided with an undervoltage
blocking.

8. Secondary system supervision

Current circuit supervision CCSRDIF (87)
Open or short circuited current transformer cores
can cause unwanted operation of many protection
functions such as differential, ground-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, 87) 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.
1MRK 511 265-BUS B
ABB