Multipurpose Protection; Secondary System Supervision - ABB RELION 650 Series Product Manual

Transformer protection RET650 2.1 IEC
Thermal overload protection, two time constant
TRPTTR
If a power transformer reaches very high temperatures
the equipment might be damaged. The insulation within
the transformer will experience forced ageing. As a
consequence of this the risk of internal phase-to-phase
or phase-to-earth faults will increase.
The thermal overload protection estimates the internal
heat content of the transformer (temperature)
continuously. This estimation is made by using a
thermal model of the transformer with two time
constants, which is based on current measurement.
Two warning levels are available. This enables actions in
the power system to be done before dangerous
temperatures are reached. If the temperature continues
to increase to the trip value, the protection initiates a
trip of the protected transformer.
The estimated time to trip before operation is
presented.
Breaker failure protection CCRBRF
Breaker failure protection (CCRBRF) ensures a fast
backup tripping of the surrounding breakers in case the
own breaker fails to open. CCRBRF can be current-
based, contact-based or an adaptive combination of
these two conditions.
A current check with extremely short reset time is used
as check criterion to achieve high security against
inadvertent operation.
Contact check criteria can be used where the fault
current through the breaker is small.
CCRBRF can be single- or three-phase initiated to allow
use with single phase tripping applications. For the
three-phase version of CCRBRF the current criteria can
be set to operate only if two out of four for example,
two phases or one phase plus the residual current start.
This gives a higher security to the back-up trip
command.
CCRBRF function can be programmed to give a single- or
three-phase re-trip of its own breaker to avoid
unnecessary tripping of surrounding breakers at an
incorrect initiation due to mistakes during testing.

5. 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.
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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
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overcurrent protection steps can be made directional
with selectable voltage polarizing quantity. Additionally
they can be voltage and/or current controlled/
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.
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6. Secondary system supervision

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 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 algorithm is
recommended for IEDs used in isolated or high-
impedance earthed networks. It is based on the
negative-sequence quantities.
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.
The selection of different operation modes is possible
by a setting parameter in order to take into account the
particular earthing of the network.
A criterion based on delta current and delta voltage
measurements can be added to the fuse failure
supervision function in order to detect a three phase
fuse failure, which in practice is more associated with
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voltage transformer switching during station
operations.
1MRK 504 161-BEN C
SEMOD113820-4 v11
ABB