ABB UniGear 500R - Optional Features and Applications

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4.6 Optional applications
4.6.1. Earthing switch for busbar earthing (Figure
43).
Earthing the busbar can also be carried out using an
earthing switch (mounted in a box), fitted on the top of
the switchgear.
 The earthing switch is mounted on top of the
switchgear, above the busbar compartment.
 The mechanism of the earthing switch is mounted
on top of the switchgear, above the low voltage
compartment.
Note:
The busbar earthing switch can be used only with 586
mm height of LV compartment.
WARNING
Care must be taken when operating the busbar
earthing switch. Before operating it, make sure
that the busbars are deenergised.
Figure 43: Earthing switch for busbar earthing.
1 Earthing switch
2 Mechanism of earthing switch
4.6.2. Voltage transformer for busbar measurement
Busbar voltage measurement can also be carried out
using a voltage transformer (Figure 44) detail 1,
mounted on top of the switchgear, above the busbar
compartment.
Figure 44: Voltage transformer.
4.6.3. Ith Limiters
The sensors consist of micro-switches positioned on
the top of the switchgear near the gas exhaust flaps of
the two power compartments (busbars and circuit-
breaker/cables) for the IEC version. For the ENA
version the sensors are positioned on the rear part on
the vertical flaps of the two power compartments.
The shock wave makes the flaps open and operates
the micro-switches connected to the shunt opening
release of the circuit-breaker. Reaction time is less
than 15 ms. The signal from the microswitch can be
sent directly to the circuit-breaker OFF trigger.
Rapid elimination of the fault, together with the metal
segregation between compartments and the use of
selfextinguishing materials, drastically reduces any
possible damage.
Figure 46: Auxiliary Ith limiter switch. It may be necessary
to move the auxiliary switches into their service position
when the lifting eyebolts have been removed.
The centre of the switch knob of the auxiliary switch must
benadjusted to the centre of the pressure relief flap hole.
1 Ith limiter
2 Pressure relief flap, made of steel sheet