Hitachi Relion 670 Series Applications Manual page 242

Section 12
Control
• 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.
Earthing switches are allowed to connect and disconnect earthing of isolated points. Due to
capacitive or inductive coupling there may be some voltage (for example < 40% of rated voltage)
before earthing and some current (for example < 100A) after earthing 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
earthing switch is usually not fully interlocked. The operator must be convinced that the line is not
energized from the other side before closing the earthing 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 both two phases in each
apparatus for both open and close indications. Phase discrepancies will result in an unknown double
indication state.
12.4.1 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 specific conditions (Qx_EXy) are set to
1=TRUE if they are not used, except in the following cases:
• QB9_EX2 and QB9_EX4 in modules BH_LINE_A and BH_LINE_B
• QA1_EX3 in module AB_TRAFO
when they are set to 0=FALSE.
12.4.2 Interlocking for line bay ABC_LINE
12.4.2.1 Application
The interlocking for line bay (ABC_LINE) function is used for a line connected to a double busbar
arrangement with a transfer busbar according to figure 92. The function can also be used for a
236
© 2017 - 2023 Hitachi Energy. All rights reserved
1MRK506375-UEN Rev. N
M13529-4 v4
IP14139-1 v2
M13561-3 v8
Railway application RER670
Application manual