ABB RELION RET670, Applications Manual

Page: 724 / 1016

example < 40% of rated voltage) before grounding and some current (for example <
100A) after grounding of a line.
Circuit breakers are usually not interlocked. Closing is only interlocked against
running disconnectors in the same bay, and the bus-coupler opening is interlocked
during a busbar transfer.
The positions of all switching devices in a bay and from some other bays determine the
conditions for operational interlocking. Conditions from other stations are usually not
available. Therefore, a line grounding switch is usually not fully interlocked. The
operator must be convinced that the line is not energized from the other side before
closing the grounding switch. As an option, a voltage indication can be used for
interlocking. Take care to avoid a dangerous
enable condition at the loss of a VT
secondary voltage, for example, because of a blown fuse.
The switch positions used by the operational interlocking logic are obtained from
auxiliary contacts or position sensors. For each end position (open or closed) a true
indication is needed - thus forming a double indication. The apparatus control function
continuously checks its consistency. If neither condition is high (1 or TRUE), the
switch may be in an intermediate position, for example, moving. This dynamic state
may continue for some time, which in the case of disconnectors may be up to 10
seconds. Should both indications stay low for a longer period, the position indication
will be interpreted as
unknown . If both indications stay high, something is wrong, and
the state is again treated as unknown .
In both cases an alarm is sent to the operator. Indications from position sensors shall be
self-checked and system faults indicated by a fault signal. In the interlocking logic, the
signals are used to avoid dangerous
enable or release conditions. When the switching
state of a switching device cannot be determined operation is not permitted.
For switches with an individual operation gear per phase, the evaluation must consider
possible phase discrepancies. This is done with the aid of an
AND-function for all three
phases in each apparatus for both open and close indications. Phase discrepancies will
result in an unknown double indication state.
15.3.1 Configuration guidelines
M13529-4 v4
The following sections describe how the interlocking for a certain switchgear
configuration can be realized in the IED by using standard interlocking modules and
their interconnections. They also describe the configuration settings. The inputs for
delivery specific conditions (Qx_EXy) are set to 1=TRUE if they are not used, except
in the following cases:
• 989_EX2 and 989_EX4 in modules BH_LINE_A and BH_LINE_B
• 152_EX3 in module AB_TRAFO
Section 15
1MRK 504 163-UUS A
Control
718 Transformer protection RET670 2.2 ANSI
Application manual