ABB UniGear 500R - Page 62

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7.4.1. To operate the three-position disconnector
of the bus-section unit (Figure 106).
The two busbar systems can be isolated from each
other by opening either three-position disconnector
(Ds and Dd) (chapter 7.3). To connect the two busbar
systems together, both three-position disconnectors
(Ds and Dd) must be in the ON position and the
circuit-breaker (E) must be closed (chapter 7.3).
WARNING
Care must be taken when operating
disconnectors/earthing switches to avoid the
inadvertent paralleling of unequal busbar systems.
Before operation, make sure correct consent is
given.
To earth left-hand busbars
1. Ensure that all the units derived from the left
busbars are dead (three-position disconnectors in
the OFF position).
2. Set the three-position disconnector (Ds) of left unit
in the ON position (chapter 7.3).
3. Set the three-position disconnector/earthing switch
(Dd) of right unit in the EARTH position (see par.
7.3.3.).
Note:
Electrical tripping of the circuit-breaker is disabled
when the three-position disconnector is in the
EARTH position.
4. Close the circuit-breaker (E) to apply the earth
(chapter 7.1).
5. If necessary, secure the earth by fitting a padlock
onto the opening button of the circuit-breaker to
prevent unauthorised removal of the busbar earth
(Figure 89).
Figure 106: To earth left-hand busbars.
Ds Three-position disconnector
E Circuit-breaker
Dd Three-position disconnector
To earth right-hand busbars
1. Ensure that all the units derived from the right
busbars are dead ( three-position disconnector in
the OFF position)
2. Set the three-position disconnector (Dd) of the
right unit in the ON position (see par. 8.3.1.)
3. Set the three-position disconnector (Ds) of the left
unit in the EARTH position (see par. 8.3.3.)
Note:
Electrical tripping of the breaker is disabled when
the three-position disconnector is in the EARTH
position.
4. Close the circuit-breaker (E) to apply the earth
(chapter 7.1)
5. If necessary, secure the earth by fitting a padlock
onto the opening button of the circuit-breaker to
prevent unauthorised removal of the busbar earth
(Figure 89)
WARNING
Selecting the EARTH position of the threeposition
disconnector does not earth the busbars. To apply
the earth, the circuitbreaker must also be closed. A
padlock shall be fitted onto the opening button of
the circuit-breaker to prevent inadvertent removal
of the circuit earth (Figure 89).
Figure 107: To earth right-hand busbars.
Ds Three-position disconnector
E Circuit-breaker
Dd hree-position disconnector
7.4.2. Busbar earthing
The busbar earthing must be connected via the
circuitbreaker: the three-position disconnector
adjacent to the required busbar must be closed and
the three-position disconnector on the other side of
the circuit-breaker must be in the EARTH position.
The busbar earth is finally applied by closing the
circuit-breaker. In any case the two busbar systems
can never be earthed at the same time.
WARNING
Do not earth busbars without first obtaining
correct consent in order to be sure that the
busbars are dead.