Frequency Protection; Secondary System Supervision - ABB Relion 650 Series Product Manual

Transformer protection RET650
Version 2.2
adjacent parts in a relatively short time. The function has
settable inverse operating curves and independent alarm
stages.
Voltage differential protection VDCPTOV
A voltage differential monitoring function is available. It
compares the voltages from two three phase sets of voltage
transformers and has one sensitive alarm step and one trip
step.
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.
The operation of LOVPTUV is supervised by the fuse failure
supervision FUFSPVC.

7. Frequency protection

Underfrequency protection SAPTUF
Underfrequency occurs as a result of a lack of sufficient
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.
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 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.
Hitachi Power Grids
Rate-of-change of frequency protection SAPFRC
The rate-of-change of frequency protection function
(SAPFRC) gives an early indication of a main disturbance in
the system. SAPFRC measures frequency with high
SEMOD153862-5 v7
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.
SEMOD171457-5 v8
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.

8. Secondary system supervision

Current circuit supervision CCSSPVC
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.
M13349-3 v13
Current circuit supervision (CCSSPVC) 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 inadvertent tripping.
Fuse failure supervision FUFSPVC
The aim of the fuse failure supervision function (FUFSPVC)
is to block voltage measuring functions at failures in the
secondary circuits between the voltage transformer and the
IED in order to avoid inadvertent operations that otherwise
M14953-3 v12
might occur.
The fuse failure supervision function basically has three
different detection methods, negative sequence and zero
sequence based detection and an additional delta voltage
and delta current detection.
The negative sequence detection is recommended for IEDs
used in isolated or high-impedance earthed networks. It is
based on the negative-sequence measuring quantities, a
high value of negative sequence voltage 3U
presence of the negative-sequence current 3I
The zero sequence detection is recommended for IEDs
used in directly or low impedance earthed networks. It is
based on the zero sequence measuring quantities, a high
value of zero sequence voltage 3U
the zero sequence current 3I
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