Frequency Protection; Multipurpose Protection; General Calculation; Secondary System Supervision - Hitachi Relion 670 Series Product Manual

Phasor measurement unit RES670
Version 2.2
OV2PTOV has a high reset ratio to allow settings close to
system service voltage.

8. Frequency protection

Underfrequency protection SAPTUF
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.
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.
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
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.
Frequency time accumulation protection FTAQFVR
Frequency time accumulation protection (FTAQFVR) is
based on measured system frequency and time counters.
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M13349-3 v13
M14953-3 v12
M14965-3 v14
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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.

9. Multipurpose protection

General current and voltage protection CVGAPC
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.

10. General calculation

Multipurpose filter SMAIHPAC
The multi-purpose filter function block (SMAIHPAC) is
arranged as a three-phase filter. It has very much the same
user interface (e.g. inputs and outputs) as the standard pre-
processing function block SMAI. However the main
difference is that it can be used to extract any frequency
component from the input signal. Thus it can, for example,
be used to build sub-synchronous resonance protection for
synchronous generator.

11. Secondary system supervision

Current circuit supervision CCSSPVC
Open or short circuited current transformer cores can cause
unwanted operation of many protection functions such as
1MRK 511 410-BEN P
M13083-11 v9
GUID-EB0B11C3-FF79-4B8D-A335-649623E832F9 v3
M12444-3 v10
Hitachi Energy