ABB RET670 Product Manual page 19

ABB
Transformer protection RET670
Customized
Product version: 1.2
The fuse failure supervision function basically has
three different algorithms, negative sequence and
zero sequence based algorithms and an
additional delta voltage and delta current
algorithm.
The negative sequence detection algorithm 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 voltage 3U without the presence of the
2
negative-sequence current 3I
The zero sequence detection algorithm 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 voltage 3U without the presence of the
0
residual current 3I .
0
For better adaptation to system requirements, an
operation mode setting has been introduced
which makes it possible to select the operating
conditions for negative sequence and zero
sequence based function. The selection of
different operation modes makes it possible to
choose different interaction possibilities between
the negative sequence and zero sequence based
algorithm.
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 voltage transformer switching
during station operations.
10. Control
Synchrocheck, energizing check, and
synchronizing SESRSYN
The Synchronizing function allows closing of
asynchronous networks at the correct moment
including the breaker closing time, which
improves the network stability.
Synchrocheck, energizing check, and
synchronizing (SESRSYN) function checks that
the voltages on both sides of the circuit breaker
are in synchronism, or with at least one side dead
to ensure that closing can be done safely.
SESRSYN function includes a built-in voltage
selection scheme for double bus and 1½ breaker
or ring busbar arrangements.
Manual closing as well as automatic reclosing can
be checked by the function and can have different
settings.
For systems which are running asynchronous a
synchronizing function is provided. The main
purpose of the synchronizing function is to
provide controlled closing of circuit breakers
.
2
when two asynchronous systems are going to be
connected. It is used for slip frequencies that are
larger than those for synchrocheck and lower
than a set maximum level for the synchronizing
function.
Apparatus control APC
The apparatus control functions are used for
control and supervision of circuit breakers,
disconnectors and earthing switches within a bay.
Permission to operate is given after evaluation of
conditions from other functions such as
interlocking, synchrocheck, operator place
selection and external or internal blockings.
Apparatus control features:
• Select-Execute principle to give high reliability
• Selection function to prevent simultaneous
• Selection and supervision of operator place
• Command supervision
• Block/deblock of operation
• Block/deblock of updating of position indications
• Substitution of position indications
• Overriding of interlocking functions
• Overriding of synchrocheck
• Operation counter
• Suppression of Mid position
Two types of command models can be used:
• Direct with normal security
• SBO (Select-Before-Operate) with enhanced
In normal security, the command is processed
and the resulting position is not supervised.
However with enhanced security, the command is
processed and the resulting position is supervised.
Normal security means that only the command is
evaluated and the resulting position is not
1MRK 504 117-BEN D
operation
security
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