The switch is designed around puffer interrupters contained in a fully welded and
sealed 316 grade stainless steel enclosure filled with SF6 gas. The SF6 gas as the
insulating and arc quenching media together with the puffing principle ensure the
positive breaking of small currents, mainly active load currents, cable charging
current, magnetising current, etc. The extremely short arcing times (within half a
cycle) plus tulip type contacts with arc resistant material ensure the long switching
life and extended short circuit making capability. The interrupters are ganged
together and driven by an over-centering spring mechanism. This is operated either
manually or by a DC motor in a motor compartment below the tank.
All switches are fitted with a manual operating arm that allows hookstick operation
from ground level. By pulling on the appropriate side of the arm the load break
switch can be tripped or closed. The mechanism is "operator independent" so that
it does not matter how fast or slow the arm is moved by the operator.
A motor mechanism is used in feeder automation schemes to facilitate remote
control. The motor is fitted to the switch and its power is supplied from batteries
installed in the pole mounted control and communications cubicle. This cubicle also
houses the mechanism control and battery charging unit. A detachable control
cable is used to connect the cubicle to the switch.
The tulip contact with arc resistant material (Cu-W) ensures the long contact life
and high short circuit making capability.