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Trip-free interlock
Figure 28: Circuit breaker interlocks and
ground disconnect on page 29 shows the
devices providing the trip-free interlock
function. The purpose of the trip-free
interlock is to hold the circuit breaker
operating-mechanism mechanically and
electrically trip-free. The circuit breaker is held
trip-free during racking and whenever the
circuit breaker is between the TEST and
CONNECT positions within the switchgear
enclosure.
This interlock functions so that the circuit
breaker primary contacts can only be closed
when in the CONNECT position, in the TEST
position or out of the switchgear cell.
Rating interlock
Figure 28: Circuit breaker interlocks and
ground disconnect on page 29 shows the
rating-interlock interference plates mounted
on the circuit breaker frame.
The circuit breaker interference plates are
complemented by matching plates located in
the cubicle.
The interference plates (rating interlocks) test
the circuit breaker voltage, continuous
current and interrupting and momentary
ratings and will not allow circuit breaker
insertion unless the circuit breaker ratings
match or exceed the cell rating.
Type GMSG (not type GMSG-GCB) circuit
breaker rating interlocks
Type GMSG (not type GMSG-GCB) vacuum
circuit breakers rated up to 50 kA are
designed such that a single circuit breaker of
the maximum ratings (voltage, interrupting
rating and continuous current) can be
installed in any switchgear compartment. For
example, a type GMSG circuit breaker rated
15 kV, 50 kA interrupting and 3,000 A
continuous current can be installed in any
type GM-SG circuit breaker cell (except
generator circuit breaker cells) of equal or
lower ratings.
Type GMSG (not type GMSG-GCB) vacuum
circuit breakers rated 63 kA are designed such
that a circuit breaker can be installed in any
type GM-SG circuit breaker cell (except
generator circuit breaker cells) rated 63 kA
and of equal or lower voltage and continuous
current ratings.
Type GMSG-GCB (not type GMSG)
generator circuit breaker rating interlocks
Type GMSG-GCB (not type GMSG) generator
circuit breakers rated 40 kA are designed such
that the circuit breaker can be installed in a
generator circuit breaker cell rated 40 kA of
equal or lower continuous current rating.
Type GMSG-GCB generator circuit breakers
rated 50 kA or 63 kA are designed such that
the circuit breaker can be installed in a
generator circuit breaker cell of equal or
lower interrupting rating, and equal or lower
continuous current rating.
Circuit breaker frame
The frame of the type GMSG vacuum circuit
breaker contains several important devices
and features deserving of special attention.
These are the ground disconnect, the four
racking wheels and the four handling wheels.
Hazardous voltage and high-speed moving parts.
Will cause death, serious injury and property damage.
Do not by-pass interlocks or otherwise make interlocks inoperative.
Interlocks must be in operation at all times.
Read this instruction manual. Know and understand correct interlock
function. Check interlock function prior to inserting a circuit breaker
into a switchgear cubicle.
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