Mechanism - GE PVDB-28kV Instructions Manual

Section 3. Distribution Breaker
c
The cuITent transfonners are bolted to the top frame
with bolts through each comer and must be properly
centered around the bushing when installed.
3-1 High Voltage Compartment
The three phases in the high voltage compartment,
Figure 1, consist of porcelain bushings, bushing current
transformers, vacuum interrupters, insulating supports,
and connection bars.
3-3 Device and Terminal Board
Panels are provided in the low voltage compartment,
Figure 2, for mounting terminal boards for C.T. and
control wiring and control devices. A cut-out with a
cover plate is provided in the floor to permit conduit
connection for external circuits.
3-4 Mechanism
The trip-free operating mechanism is motor charged
and spring operated. The action of a closing cam, (Fig.
3, 5), driven by a closing spring causes closing of the
breaker contacts thru a toggle linkage. In closing,
energy is stored in the opening springs and the contact
wipe springs. Release of this energy by operation of the
trip latch causes breaker contacts to open.
Figure 1. High Voltage Compartment
The vacuum inten"Upters, their supports and the
operating mechanism comprise an inten"Upting module
which is essentially the same as the PowerVac circuit
breaker used in Metal-Clad Switchgear.
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The bushings are clamped to the roof of the housing.
The bushing core is centered in the air-filled porcelain
and rubber gaskets seal each end. Mter the bushings
have been clamped in place no further adjustment is
necessary when installing the connection bars
3-2 Bushing Current Transformers
Bushing cuITent transformers are used on these breakers
to provide a source of CUITent supply for operating
protective relays. Relaying transformers are of the multi-
ratio type having five leads which provide a wide range
of ratios. Ratio accuracy classification for standard
transformers are in accordance with ANSI C-57-13 and
NEMA SG-4, table 3-5 specifications.
Figure 2. Low Voltage Compartment-Mechanism Side
Additional mechanism features shown in Figure 2, are
the open<lose and charged-<lischarged indicators; oper-
ations counter, manual close and trip pushbuttons;
auxiliary switch; and padlock on the trip function. An
optional feature is the addition of a key interlock on the
trip function.
High accuracy. single-tap metering-type current trans-
formers can also be furnished. Ratio and accuracy
classification for standard transformers of this type are
also in accordance with ANSI C-57-13 and NEMA SG4
table 3-5 specifications.
Closing and opening operations may be controlled
electrically by a control switch on the breaker or remote
relaying. Mechanical control is provided by manual
close and trip buttons on the circuit breaker. The
closing spring may be manually charged, and a method
for slow<losing the primary contacts is available. The
mechanism will operate at the ac or dc voltage indicated
on the circuit breaker nameplate.
Performance data in the form of ratio curves are
available for all standard transformers of standard
ratios. These are supplied in an instruction book or can
be secured from the Switchgear Operation by giving the
proper references.
The manual charging system (Fig. 5, View A, 3) works
directly on the cam shaft where a one way clutch (Fig. 5,
View A, 7) driven by a manual handle provides rotation
of the ratchet wheel. Manual pumping of the handle
advances the ratchet wheel, and the holding pawl
Bushing cuaent U"ansfonners are mounted inside the
top frame. They are installed from underneath the top
frame and must be slipped over lower end of bushing.
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