7. Frequency protection
Underfrequency protection SAPTUF
M13349-3 v12
Underfrequency occurs as a result of a lack of generation in
the network.
Underfrequency protection SAPTUF measures frequency with
high accuracy, and is used for load shedding systems,
remedial action schemes, gas turbine startup and so on.
Separate definite time delays are provided for operate and
restore.
SAPTUF is provided with undervoltage blocking.
The operation is based on positive sequence voltage
measurement and requires two phase-phase or three phase-
neutral voltages to be connected. For information about how
to connect analog inputs, refer to Application manual/IED
application/Analog inputs/Setting guidelines
Overfrequency protection SAPTOF
M14953-3 v11
Overfrequency protection function SAPTOF 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 measures frequency with high accuracy, and is used
mainly for generation shedding and remedial action schemes.
It is also used as a frequency stage initiating load restoring. A
definite time delay is provided for operate.
SAPTOF is provided with an undervoltage blocking.
The operation is based on positive sequence voltage
measurement and requires two phase-phase or three phase-
neutral voltages to be connected. For information about how
to connect analog inputs, refer to Application manual/IED
application/Analog inputs/Setting guidelines
Rate-of-change frequency protection SAPFRC
M14965-3 v12
The rate-of-change frequency protection function SAPFRC
gives an early indication of a main disturbance in the system.
SAPFRC measures frequency with high accuracy, and can be
used for generation shedding, load shedding and remedial
action schemes. SAPFRC can discriminate between a
positive or negative change of frequency. A definite time delay
is provided for operate.
SAPFRC is provided with an undervoltage blocking. The
operation is based on positive sequence voltage
measurement and requires two phase-phase or three phase-
neutral voltages to be connected. For information about how
to connect analog inputs, refer to Application manual/IED
application/Analog inputs/Setting guidelines.
Frequency time accumulation protection FTAQFVR
GUID-020CE8CF-9BEA-455D-ACBD-13023B93B4D1 v4
Frequency time accumulation protection FTAQFVR is based
on measured system frequency and time counters. FTAQFVR
for generator protection provides the START output for a
particular settable frequency limit, when the system frequency
falls in that settable frequency band limit and positive
sequence voltage within settable voltage band limit. The
START signal triggers the individual event timer, which is the
continuous time spent within the given frequency band, and
the accumulation timer, which is the cumulative time spent
within the given frequency band. Once the timers reach their
limit, an alarm or trip signal is activated to protect the turbine
against the abnormal frequency operation. This function is
blocked during generator start-up or shut down conditions by
monitoring the circuit breaker position and current threshold
value. The function is also blocked when the system positive
sequence voltage magnitude deviates from the given voltage
band limit which can be enabled by
EnaVoltCheck
setting.
It is possible to create functionality with more than one
frequency band limit by using multiple instances of the
function. This can be achieved by a proper configuration
based on the turbine manufacturer specification.
8. Multipurpose protection
General current and voltage protection CVGAPC
M13083-11 v9
The General current and voltage protection (CVGAPC) can be
utilized as a negative sequence current protection detecting
unsymmetrical conditions such as open phase or
unsymmetrical faults.
CVGAPC can also be used to improve phase selection for
high resistive earth faults, outside the distance protection
reach, for the transmission line. Three functions are used,
which measures the neutral current and each of the three
phase voltages. This will give an independence from load
currents and this phase selection will be used in conjunction
with the detection of the earth fault from the directional earth
fault protection function.
Voltage-restrained time overcurrent protection VRPVOC
GUID-935E1CE8-601F-40E2-8D22-2FF68420FADF v6
Voltage-restrained time overcurrent protection (VRPVOC)
function can be used as generator backup protection against
short-circuits.
The overcurrent protection feature has a settable current level
that can be used either with definite time or inverse time
characteristic. Additionally, it can be voltage controlled/
restrained.
One undervoltage step with definite time characteristic is also
available within the function in order to provide functionality
for overcurrent protection with undervoltage seal-in.
1MRK 511 361-BEN B
Bay control REC670 2.1 IEC
Product version: 2.1
24
ABB
Summary of Contents for REC670 2.1 IEC
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