ABB MNS R, System Manual, Page: 6 / 28

4 ABB SACE
Construction and functional characteristics
Switchgear frame
The MNS R frame is based on
modular 2 mm thick still C sec-
tions, pre-drilled at a pitch of 25
mm. Each unit is based on
modular elements and consists
of:
– circuit-breaker compartments
– instruments compartments
– busbar compartment
– cable compartment.
All compartments are meccani-
cally segregated from the others.
The switchgear is pre set for
easy extensions on both sides.
Earthing
The switchgear is provided with a
continuous electrolytic copper earth-
ing busbar, with a cross-section suit-
able for the proper switchgear short-
circuit rating and pre-set on both
sides for connection to the earthing
network.
Are connected to the earthing busbar
- all the metallic structures of the indi-
vidual units;
- all not live metallic parts of the cir-
cuit-breakers;
- all CTs and VTs secondary earthing
connections.
All others not live metallic parts of the
apparatus are connected to the earth-
ing busbar by means of the unit me-
tallic structure.
The doors with apparatus installed are
connected to the structure by means
of flexible copper braids. All the
ground connections are made with
screws or bolts provided with gripping
washers.
ABB PC30 23-11-2009, 8:13 4