Siemens GMSG Instruction Manual page 33

Interlocks
Circuit breaker racking-interlocks
The vacuum interrupter/operator module,
the vehicle portion of the circuit breaker
and the racking mechanism in the
switchgear all cooperate to provide
important operational interlocking
functions.
1. Rating interlock
The rating interlock consisting of a
coded-interference plate is mounted on
the vehicle (refer to Figure 28: Circuit
breaker interlocks and ground
disconnect on page 29).
A mating-interference blocking plate is
mounted in the drawout compartment
(refer to Figure 29: Circuit breaker
compartment up to 50 kA shown on
page 30).
The two plates are mounted in
alignment and must pass through each
other in order for the circuit breaker
vehicle to enter the drawout
compartment. The interlock is coded to
test rated voltage, as well as
interrupting and continuous current
ratings.
Type GMSG 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 of
equal or lower ratings.
Type GMSG vacuum circuit breakers
rated 63 kA are designed such that a
circuit breaker can be installed in any
type GM-SG circuit breaker cell rated
63 kA and of equal or lower voltage
and continuous current ratings.
Vacuum interrupter/operator
Ground
disconnect
Figure 30: Interlock mechanisms on the type GMSG vacuum circuit breaker
2. Racking interlocks
A. CLOSED circuit breaker interlock
Figure 28: Circuit breaker interlocks
and ground disconnect on page 29
shows the location of the CLOSED
circuit breaker interlock-plunger on
the circuit breaker frame.
The purpose of this interlock is to
positively block circuit breaker
racking-operations whenever the
circuit breaker is CLOSED. The
plunger is coupled to the jack shaft
as seen in Figure 15: Stored-energy
operating mechanism, item 63 on
page 20. When the jack shaft rotates
to close, the interlock plunger is
driven straight downward beneath
the frame of the circuit breaker. The
downward projecting plunger blocks
racking operation when the circuit
breaker is CLOSED.
Racking Trip-free
mechanism interlock
release handle
Closed
circuit
breaker
racking
interlock
33