1
2
18
VM1
- USER MANUAL
Fig. 10
—
7. Operation
7.3.2. Interlocks in the case where ABB
withdrawable trucks are used
1) The VM1 circuit breaker can only be closed by
means of the logical input when a voltage of 24
V - 240 V AC/DC is applied (electric lock on
closing).
2) The VM1 circuit breaker can only be closed
when the withdrawable truck is in the test or
service position. In intermediate positions the
closing lock voltage is cut off by the auxiliary
contacts.
3) A mechanical interlock positioned on the
withdrawable truck prevents a closed circuit
breaker from being moved from the test
position to the service position.
4) MV1 circuit breaker can only be racked-in/
isolated if the locking electromagnet in the
truck is supplied and the apparatus (as well as
being open) is in the “READY” state.
7.2. Principle of extinction of the
vacuum interrupter
Given the relatively low static pressure of the
interruption chamber (between 10
-4
and 10
-8
hPa),
a relatively limited distance between the contacts
is required to obtain high dielectric strength. The
vacuum arc is extinguished on the first passage of
the current through natural zero.
Considering the limited distance between the
contacts, the high conductivity of the plasma of
metallic vapours, the drop in voltage of the arc
and, moreover, the short arcing time, the energy
associated with the arc is extremely limited,
therefore producing benefits for the useful life of
the contacts obtained and, consequently, for the
useful life of the vacuum interrupters.
7.3. Interlocks
7.3.1. Interlocks / protection against
malfunction (for withdrawable circuit
breakers for ABB switchgear)
A series of interlocks is provided to prevent
incorrect operations and/or malfunctions. The
interlocks are the following:
•
the withdrawable truck can only be moved from
the test/isolated position to the service position
(and vice versa) if the circuit breaker is open (this
means that first of all the circuit breaker must be
opened).
•
the circuit breaker can be closed if the
withdrawable truck is exactly in the defined test
position or in the service position (electric
interlock).
•
the circuit breaker can be opened manually in the
service or test position when it is not powered,
but it cannot be closed.
•
the switchgear is provided with devices which only
allow connection and disconnection of the plug
connector (1) (fig. 10) in the test/isolation
position.
Any detailed information regarding additional
interlocks, e.g. in connection with the earthing
switch operating mechanism, is given in the
specific order documentation.
Summary of Contents for VM1
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