ABB REL650 series, Applications Manual

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• With basically zero current. The circuit is open on one side and has a small extension.
The capacitive current is small (for example, < 5A) and power transformers with
inrush current are not allowed.
• To connect or disconnect a parallel circuit carrying load current. The switching
voltage across the open contacts is thus virtually zero, thanks to the parallel circuit
(for example, < 1% of rated voltage). Paralleling of power transformers is not
allowed.
Grounding switches are allowed to connect and disconnect grounding of isolated points.
Due to capacitive or inductive coupling there may be some voltage (for 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.
11.5.3 Configuration guidelines
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
1MRK 506 334-UUS A
Section 11
Control
347
Application manual