24
Circuit-breaker racking-in/-out must be carried out
gradually to avoid shocks which may deform the
mechanical interlocks and the limit switches.
The torque normally required to carry out rack-
ing-in and racking-out is
£
25 Nm.
This value must not be exceeded. If operations
are prevented or difficult, do not force them and
check that the operating sequence is correct.
Note
To complete the racking-in/out operation, about
20 rotations of the lever are required for circuit-
breakers up to 17.5 kV, and about 30 rotations
for 24 kV circuit-breakers.
When the circuit-breaker has reached the isolated
for test/isolated position, it can be considered to
be racked into the switchgear and, at the same
time, earthed by means of the truck wheels.
Withdrawable circuit-breakers of the same
version, and therefore of the same dimensions,
are interchangeable.
However, when different fitting of electrical
accessories is foreseen, for example, different
coding of the auxiliary circuit plug prevents
incorrect combinations between circuit-breakers
and panels.
The racking-in/-out operations must
always be carried out with the circuit-
breaker open.
7.5.1. Circuit-breakers with motor-driven
withdrawable truck (on request)
Test the motor-driven truck in the same way as
a truck with manual racking-in:
– turn off the truck motor circuit power supply to
lock it electrically;
– turn the crank handle (1) (fig. 9) to the desired
position.
Note
When the moving part moves, it makes the motor
turn, which, acting like a generator, can cause a
reverse voltage at the connection terminals.
7.3. Preliminary operations
– Clean the insulating parts with clean dry cloths.
– Check that the top and bottom terminals are
clean and free of any deformation caused by
shocks received during transport or storage.
7.4. Installation of fixed circuit-breakers
The circuit-breaker can be mounted directly on
supporting frames to be provided by the cus-
tomer, or on a special supporting truck (avail-
able on request).
The circuit-breaker, with supporting truck, must
be suitably fixed to the floor of its own
compartment by the customer.
The floor surface in correspondence with the truck
wheels must be carefully levelled.
A minimum degree of protection (IP2X) must be
guaranteed from the front towards live parts.
7.4.1. Mounting the circuit-breaker on trucks
constructed by other manufacturers
VD4 circuit-breakers which are not installed on
ABB trucks, but on trucks constructed by the
customer must be fitted with one or two additional
auxiliary contacts (activated by the mechanical
lock and by the circuit-breaker trip device)
entrusted with the function of interrupting the
shunt closing release circuit release (-MC).
In ABB trucks, this function is carried out by the
auxiliary contacts -BT1 and -BT2 which cut of
the release power supply during and before
activation of the mechanical lock of the screw
device for racking the truck in. This means the
shunt closing release power supply can only be
applied after activation of the mechanical lock.
In this way there is the certainty that no electrical
impulse can activate the shunt closing release
with the circuit-breaker in the intermediate
position.
7.5. Installation of withdrawable circuit-
breakers
The withdrawable circuit-breakers are preset for
use in UniGear type ZS1 and UniSafe switchgear.
For racking-in/racking-out of the switchgear, fully
insert the lever (1) (fig. 9) in the appropriate seat
(2) and work it clockwise for racking-in, and anti-
clockwise for racking-out, until the limit switch
positions are reached.
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