Service Trucks; Earthing Truck Without Making Capacity; Earthing Truck With Making Capacity; Power Cable Test Truck - ABB UniGear ZS1 Instruction Manual

6.4 Service trucks

The service trucks are divided into four different types:

6.4.1 Earthing truck without making capacity

These trucks carry out the same function as the earthing switches without making capacity. Therefore
they do not have any capacity to earth the live circuits under fault conditions. They are used to ensure
fixed additional earthing, as required by the plant service and maintenance procedures, as a further
guarantee for personnel. The use of these trucks foresees removal of the switching device from the
switchgear (circuit-breaker or contactor) and its replacement with the truck. The units preset for use
of earthing trucks are fitted with a key lock which, if activated, prevents their racking-in.
This truck is available in two versions:
• main busbar system earthing;
• power cable earthing.
During the racking-in phase, the main busbar earthing truck only lifts the top shutter and earths the
contacts connected to the top branches (and therefore to the main busbar system) by means of the
switchgear structure.
During the racking-in phase, the power cable earthing truck only lifts the bottom shutter and earths the
contacts connected to the bottom branches (and therefore to the power cables) by means of the
switchgear structure.
These trucks can also be used in the bus-tie units. In this case, they earth the two sides of the main
busbar system.

6.4.2 Earthing truck with making capacity

These trucks carry out the same function as the earthing switches with making capacity. They consist
of circuit-breakers only fitted with top (main busbar earthing) or bottom (power cable earthing)
terminals. The contacts without terminals are short-circuited by means of a copper bar and connected
to earth by means of the apparatus truck. They keep all the characteristics of the circuit-breakers, such
as full making capacity and opening of the live circuits under fault conditions.
They are used to ensure extremely efficacious earthing on circuits stressed by a fault. They allow
opening and closing moperations to be carried out rapidly with remote electric control.
The use of these trucks foresees removal of the switching device from the switchgear (circuit-breaker
or contactor) and its replacement with the truck. The units preset for use of earthing trucks are fitted
with a key lock which, if activated, prevents their racking-in.
This truck is available in two versions:
• main busbar system earthing;
• power cable earthing.
During the racking-in phase, the main busbar earthing truck only lifts the top shutter and presets the
contacts connected to the top branches (and therefore the main busbar system) for closing to earth
by means of a control.
During the racking-in phase, the power cable earthing truck only lifts the bottom shutter and presets
the contact connected to the bottom branches (and therefore to the power cables) for closing to earth
by means of the control.
These trucks can also be used in bus-tie units. In this case, they earth the two sides of the main busbar
system.

6.4.3 Power cable test truck

These trucks allow the insulation tests to be carried out on the power cables without accessing the
feeder unit or disconnecting the cables from the switchgear.
The use of this trucks foresees removal of the switching device from the switchgear (circuit-breaker
or contactor) and its replacement with the truck.
During the racking-in phase, the truck only lifts the bottom shutter and, by means of the connectors
it is fitted with, allows connection of the test apparatus cables. This truck can only be used in the
incoming/outgoing units.

6.4.4 Isolation truck

The isolation truck allows the switchgear top and bottom contacts to be connected directly. Connection
is made extremely safe by using the poles of the HD4 circuit-breakers to insulate the connection bars
from the external environment.
In the incoming/outgoing units, it connects the main busbar system to the power cables, whereas in
the bus-tie units, to the two sides of the busbar system. This truck is used in the UniGear switchgear
to make incoming/outgoing units without circuit-breakers in radial networks, to make cable connec-
tions between two piece of switchgear placed in front of each other, and for constructing interconnec-
tion units and creating bus-tie-riser units with double insulation (in this case, both the units are made
from bus-ties, the first fitted with a circuit-breaker and the other with an isolation truck).
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