ABB RELION 670 Series Product Manual page 35

Transformer protection RET670 2.1 IEC
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
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
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.
ABB
8. Multipurpose protection
General current and voltage protection CVGAPC
The protection module is recommended as a general
backup protection with many possible application areas
due to its flexible measuring and setting facilities.
The built-in overcurrent protection feature has two
settable current levels. Both of them can be used either
with definite time or inverse time characteristic. The
overcurrent protection steps can be made directional
with selectable voltage polarizing quantity. Additionally
they can be voltage and/or current controlled/
M14953-3 v11
restrained. 2nd harmonic restraining facility is available
as well. At too low polarizing voltage the overcurrent
feature can be either blocked, made non directional or
ordered to use voltage memory in accordance with a
parameter setting.
Additionally two overvoltage and two undervoltage
steps, either with definite time or inverse time
characteristic, are available within each function.
The general function suits applications with
underimpedance and voltage controlled overcurrent
solutions. The general function can also be utilized for
generator transformer protection applications where
positive, negative or zero sequence components of
current and voltage quantities are typically required.
Voltage-restrained time overcurrent protection
VRPVOC
Voltage-restrained time overcurrent protection
(VRPVOC) function can be used as generator backup
protection against short-circuits.
The overcurrent protection feature has a settable
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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.
9. 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.
Current circuit supervision (CCSSPVC) compares the
residual current from a three phase set of current
1MRK 504 155-BEN F
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