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D E S I G N A N D F U N C T I O N O F T H E S W I T C H G E A R S Y S T E M A N D I T S E Q U I P M E N T
3.8 Protection against maloperation / interlock
dependencies (Figures 6/2, 6/5 and 7/1)
3.8.1 Interlocks in general
In order to prevent hazardous situations and
maloperation, a series of interlocks are provided
to protect the operators and the switchgear itself.
•
Protection against maloperation can be
implemented by the multifunction protection
and switchbay control unit REO 517
The circuit-breaker and three position switch can
be controlled directly at the panel and/or remotely,
for instance from the control room. Operation at
the panel is by selection on the REO 517 or
conventionally with push buttons and bar-type
annunciators in the mimic diagram.
•
Three position switch UX2TE-R and the
corresponding circuit- breaker type VD4 X-R are
electrically interlocked
-
In the case of manual operation of the three
position switch, a mechanical interlock can
become effective (optional)
•
Details of further interlocks/dependencies, e.g.
with neighbouring systems, can be found in the
relevant order documents for the system
concerned
•
The interlock polling (electrical only) between
panels, where implemented, is effected by loop
lines from panel to panel
Operation on failure of auxiliary power:
On failure of the auxiliary power, the devices can
be operated manually.
The details for the specific system are also to be
observed.
Where no mechanical interlock or optional interlock
is fitted, intervention in the interlock concept is
possible by opening the control cabinet door.
Emergency manual operation is possible by means
of a hand crank and mechanical push button.
Note
Perform all switching operations fully until the
defined limit position is reached!
•
Switch off the mcbs for the circuit breaker
release circuit and operating mechanism of
the three position switch
3.8.2 Function of the interlock between the circuit
breaker and the three-position switch
3.8.2.1 Interlocks in general
In order to prevent hazardous situations and
maloperation, a series of interlocks are provided
to protect the operators and the switchgear itself.
Note
If the operating mechanism for the three position
switch fail during a switching operation, when
the switch is in an intermediate position, the
electrical interlock between the VD4 X-R circuit-
breaker and the UX2TE-R three position switch
established by the REO 517 is effective. The VD4
X-R circuitbreaker could however be closed
mechanically when the low voltage compartment
door is open.
3.8.2.2 Mechanical interlock (optional)
In addition to the electrical interlock, a mechanical
interlock can be established between the circuit
breaker and the three position switch in a panel.
The interpanel interlock between the circuit
breaker and the three position switches in the
sectionaliser and riser panels is effected in the
riser panel by means of a blocking magnet.
Closing of the circuit breaker is prevented by the
blocking magnet on failure of auxiliary voltage
and when the three position switch is in an
intermediate position. Mechanical opening of
the circuit breaker is always possible when the
low voltage compartment door is open.
Access to the manual operating shaft of the three
position switch is blocked by a flap when the
circuit breaker is closed.
The mechanical interlock is effective even on
failure of auxiliary voltage.
3.9 Earthing a tee-off
3.9.1 Electrical operation using the multifunction
protection and bay control unit REO 517 or
the buttons on the panel front
Operating sequence for tee-off earthing:
•
Circuit breaker (-Q0) OFF
•
Disconnector (-Q1) OFF
•
Earthing switch (-Q5) ON
•
Test for off-circuit condition
•
Circuit breaker (-Q0) ON
•
Secure panel to prevent switching operations
-
Switch off the mcbs for the circuit breaker
and for the operating mechanism of the
three position switch
-
Lock the control cabinet door or secure the
mechanical OFF button for the circuit
breaker if necessary
•
Label the panel to indicate that earthing has
been effected
Cancelling the earthing:
•
Open the control cabinet door and switch on
the mcb release the OFF button for the circuit
breaker if necessary
•
Circuit breaker (-Q0) OFF
•
Earthing switch (-Q5) OFF
13
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