24
Types SDV-R and SDV-R-AR distribution circuit breakers |
Instruction manual
Introduction
The type 3AH35-SDV-R vacuum circuit
breaker operator is intended for stationary
applications, such as in the SDV-R and SDV-
R-AR outdoor distribution circuit breakers.
The type 3AH35-SDV-R circuit breaker
operator conforms to the requirements of
ANSI/IEEE standards and IEC standards,
including C37.04, C37.20.4 and C37.010.
The SDV-R operator includes six vacuum
interrupters, a stored-energy operating
mechanism, necessary electrical controls, a
mechanism housing, and insulating barriers
between the vacuum interrupters.
This section describes the operation of each
major subassembly of the operator as an aid
in the operation, maintenance, and repair of
the SDV-R operator.
Vacuum interrupters
The operating principle of the vacuum
interrupter is simple. Figure 10: Vacuum
interrupter cutaway view is a section view of
a typical vacuum interrupter. The entire
assembly is sealed after a vacuum is
established. The vacuum interrupter
stationary contact is connected to the fixed-
end pole head of the circuit breaker. The
vacuum interrupter movable contact is
connected to the flexible shunt associated
with the pole carrier and to the mechanism
of the circuit breaker operator. The metal
bellows provides a secure seal around the
movable contact, preventing loss of vacuum
while permitting motion of the movable
contact along the axis of the vacuum
interrupter.
When the two contacts separate, an arc is
initiated that continues conduction up to
the next current zero. At current zero, the
arc extinguishes and any conductive metal
vapor that has been created by and
supported the arc condenses on the
contacts and on the surrounding arc shield.
The materials and shape of the contacts are
optimized to achieve the desired arc motion
and to minimize switching disturbances.
Primary connections
Each operator has three connection pads at
the vacuum circuit breaker fixed connection
(line-side connection), three connection
pads on the flexible connectors associated
with the movable contacts of the vacuum
interrupters for both the vacuum circuit
breaker and the ground switch (load-side
connection) and the fixed connection
(ground connection). Interconnecting bus in
the circuit breaker enclosure connects these
connection pads to the roof-bushing
terminals.
Phase barriers
Insulating barriers are attached to the circuit
breaker operator and provide suitable
electrical insulation between the vacuum
interrupter and primary conductors and the
circuit breaker enclosure.
Figure 10: Vacuum interrupter
cutaway view
A
Item
Description
A
Fixed-contact current
connection
B
Ceramic insulator
C
Arc shield
D
Fixed contact
E
Moving contact
F
Metal bellows
G
Guide
H
Moving-contact current
connection
B
C
D
E
F
B
G
H
Figure 11: Vacuum circuit breaker operator module
