ABB RET670 Product Manual page 18

Transformer protection RET670 ANSI
Pre-configured
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 grounded networks. It is based on the
negative-sequence measuring quantities, a high
value of voltage without the presence of the
negative-sequence current 3I
The zero sequence detection algorithm is
recommended for IEDs used in directly or low
impedance grounded networks. It is based on the
zero sequence measuring quantities, a high value of
voltage 3V without the presence of the residual
0
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.
9. Control
Synchrocheck, energizing check, and
synchronizing SESRSYN (25)
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, 25) 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.
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SESRSYN (25) function includes a built-in voltage
selection scheme for double bus and breaker-and-a-
half 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
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controlled closing of circuit breakers when two
asynchronous systems are going to be connected.
It is used for slip frequencies that are larger than
those for synchronism check 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 grounding switches within a bay. Permission to
operate is given after evaluation of conditions from
other functions such as interlocking, synchronism
check, 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
1MRK 504 118-BUS A
operation
security
ABB