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S T - E E A R T H I N G S W I T C H I N S T R U C T I O N M A N U A L
6
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3 Structure and function
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Earthing switches of series ST-E have three pairs
Figure 1: Example of
of earthing blades which are located on the
the active part of an
earthing switch
operating shaft and are able to move freely. The
mounted on a
pairs of earthing blades are electrically connected
switchgear panel
partition (without
to each other by a short-circuiting bridge and to
fixed earthing
earth potential at the bearing brackets by two
contacts)
stranded copper conductors. Driver levers and
toggle springs located between the bearing
brackets are used to transmit the force during
the switching process. Fixing the active part on
a torsionally rigid switchgear panel wall or
crossbeam provides it with the necessary stability.
The earthing contacts designed to suit the relevant
switch type are to be bolted to the conductor bars
supported on suitable insulating parts, e.g. pintype
insulators, on the opposite side and parallel to
each other, and the position adjusted until it
conforms to that show in the dimensional
drawings.
1 Driving shaft
2 Toggle spring
3 Actuating shaft
4 Earthing conductor
5 Short-circuiting bridge
6 Earthing blade
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Figure 1
1
2
3
The earthing switch has a snap action closing
mechanism which functions independently of
the rotation of the drive shaft. The switching
speed and torque achieved in this process are
independent of the actions of the operating
mechanism.
In the opening process, in contrast, the toggle
springs have no effect on the speed of contact
separation.
A ring lever or suitable manual or motorized
operating mechanism with the necessary torque
for the type of switch and an operating angle 90°
can be fitted for operation of the switch.
Note:
Always open earthing switches by turning until
the stop is reached.
The earthing switches can also be fitted with an
auxiliary switch for indication purposes.
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