Main features and advantages
n The immediate availability of stored energy
without any losses ensures constant contact
travel behaviour
n A minimum number of mechanical
components increases the reliability
n No seals or valves
n Accessible and clear arrangement of
components in the operating mechanism cubicle
n Easy access to all components without
obstruction, after lowering the outer housing
n The closing spring can be tensioned manually
n Maximum availability and reliability
n Minimal maintenance costs
Design
The principal components and the design can be
seen in Figure 1. The well-sized position and spring
tension indicators are readily visible through the
observation window in the door, and allow positive
identification of the breaker position, and of the
state of tension of the closing spring. The electrical
monitoring and control units are easily accessible
after opening the door. The electrical leads are all
taken to the terminal blocks. The sheet metal
housing including the door, can be removed for
ready access to all the internal components. The
closing and opening springs are arranged on the
two sides. All movements are frictionless damped
by means of a dashpot.
Mode of operation
The spring operating mechanism, the design of
which is shown schematically in Figure 2, consists
essentially of two tension spring systems. Closing
spring(5) is tensioned by means of the motor(13),
over the worm gear drive(21). This provides the
energy for a closing operation, which will tension
the opening spring(6) during the closing
operation.
Charging of closing spring
The main shaft(1) is rotated through 180 degrees
via the worm gear drive(21), by means of the
motor(13) or the hand crank(14), in this way
tensioning the closing spring(5).
Availability is of paramount importance for efficient
electricity supply. Reliability of lines, relays and high
voltage apparatus are important factors which
increase availability. With improved designs of SF6
high voltage circuit breakers, increased attention is
paid to reliability. International statistics, like Cigre’s
report, have shown that 80% of the failures in a
circuit breaker are of mechanical origin. Most of
these failures have been traced to the operating
mechanisms. The dynamic mechanical and
electrical performance of a circuit breaker is
complicated. Within milliseconds, the
operating mechanism has to change the circuit
breaker from a perfect conductor to a perfect
insulator. A failure in the operating mechanism may
result in a failure of the total breaking operation. The
FSA 1 operating mechanism is characterised by an
especially robust, simple, and thereby functionally
reliable design. It is suitable for three pole as well as
single pole application.
Closing operation
On a closing signal, the locking latch(7) is
released from the main shaft and closing spring(5)
discharges itself. In this way the transfer cams
rotate via the transfer lever(9). Switching shaft(2)
is actuated and the breaker closes,
simultaneously tensioning and locking the
opening spring(6). The motor(13) tensions the
closing spring(5) are every closing operation. It is
stopped via the motor limit switch(16).
Opening operation
On an opening signal, locking latch(8) is released
from switching shaft(2) and the opening spring(6)
discharges, thereby opening the breaker.
Auxiliary contacts(15) are mechanically linked
to the switching units and follow the breaker
operation exactly.
Mounting of the operating
mechanism
The operating mechanism cubicle (Figure 1),
containing the spring operating mechanism FSA 1
as well as the control and monitoring units is
easily attached to the circuit breaker. After
mounting, the mechanism cubicle to the pole
support the operating rod is coupled to the
breaker poles. In case of single pole operation the
control and monitoring elements are positioned in
each mechanism cubicle. Special provisions for
supporting the operating mechanism during
assembly are not required.
Maintenance
With minimal maintenance, the spring operating
mechanism FSA 1 offers distinct advantages,
which contribute to a reduction in operational
costs.
Lubrication of the transmission shafts and worm-
gears as well as the gear wheels is required for
the first time only after 2500 CO switching
operations, while an overhaul of the complete
operating mechanism should be carried out after
5000 CO operations.
