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Shown with outer-phase barriers removed
Figure 10: Upper and lower primary disconnects
16
Phase barriers
Figure 11: Type GMSG vacuum circuit breaker
on page 17 is a rear view of a type GMSG
vacuum circuit breaker that shows the outer-
phase (phase-to-ground) barriers. Interphase
barriers are not standard but may be provided
as an option. These glass-polyester insulating
barriers are attached to the circuit breaker
frame and provide suitable electrical
insulation between the vacuum-interrupter
primary circuits and the housing.
Stored-energy operating mechanism
The stored-energy operating mechanism of
the type GMSG vacuum circuit breaker is an
integrated arrangement of springs, solenoids
and mechanical devices designed to provide a
number of critical functions. The energy
necessary to close and open (trip) the
contacts of the vacuum interrupters is stored
in powerful tripping and closing springs. The
closing springs are normally charged
automatically, but there are provisions for
manual charging. The operating mechanism
that controls charging, closing and tripping
functions is fully trip-free. Trip-free requires
that the tripping function prevail over the
closing function as specified in ANSI/IEEE
C37.04-1999, clause 6.9 (for type GMSG) or
ANSI/IEEE C37.013, clause 6.3.8 (for type
GMSG-GCB). The operation of the stored-
energy mechanism will be discussed later in
this section.
The vacuum circuit breaker consists of two
sub-assemblies. The "interrupter/operator"
module is a unitized assembly of the three
vacuum interrupters, primary insulators and
operating mechanism. The second module,
the "vehicle", is the supporting drawout-
structure module for the operating mechanism.
The vehicle provides primary-stud extensions,
closed circuit breaker racking interlocks,
closing spring discharge feature and other
requirements needed to ensure safe and
reliable use during racking and during
operation. These two sub-assemblies will be
separately described.
Interrupter/operator module
The interrupter/operator module consists of
the three poles, each with its vacuum
interrupter and primary insulators, mounted
on the common motor or hand-charged
spring-stored energy-operating-mechanism
housing. This module is shown in Figure 12:
Interrupting/operating mechanism module on
page 17.
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