50
MOU NTI NG A N D OPE R ATI ON M A N UA L
I N D O O R A I R S W I TC H - D I S CO N N EC TO R , N A L /N A L F/ V R
18.3 Mechanical overhaul
For presently manufactured NAL switches if
below specified service conditions are met,
maintenance can be extended up to 15-years
intervals:
1. Apparatus must be transported and stored
in a genuine box.
2. Service conditions – installation:
a) apparatus must work in indoor application
under normal service conditions –
according to IEC 62271-1:2007 – p. 2.1,
b) apparatus must be installed by qualified
staff according to manufacturer’s
recommendation,
c) maximum values and numbers of the
making and breaking capacity as well as
1000 mechanical operations must not be
exceeded,
d) safe distances to earthed parts or to other
live parts or to other parts that may
become conductive in operating
conditions must be kept,
e) in special cases (e.g.: fault in the circuit
where the NAL/VR is installed or the
apparatus has been overloaded)
apparatus should be inspected,
f)
apparatus must not be installed vertically
with the hollow insulators at the bottom
which may cause water condensation in
hollow insulators and arc extinguishing
system,
Mechanical overhaul of the switch-disconnector
should be carried out after max. 1000 operations
or 15 years in service, (preferably by ABB’s staff).
18.4 Electrical overhaul in service
The frequency of overhaul depends also on the
number of operations and the magnitude of the
breaking current. After 100 operations at rated
current the main contacts, the arcing contacts
and the arc extinguishing chamber should be
inspected and replaced if one of below conditions
took place
• the tip of the arcing contact knives has dimin-
ished approx. 3 mm (minor damage might only
require polishing of the arcing tip),
• the fixed arcing fingers are burned or do not
make any contact,
• the width of the slot in the arcing chamber is
more than 8 mm.
If the copper is visible on any current bus part,
then this part should be replaced by new one.
_
CAUTION!
Eccentric bolt always must be perfectly
fitted inside the extruded socket on shaft
arm – it is not allowed to screw eccentric
bolt in middle position between teeth of
extruded socket. It is recommended to
rotate the eccentric bolt no more than one
“teeth” at one regulation operation.
_
CAUTION!
During switch-disconnector exploitation,
position of main contact may change
(parts wear) but it cannot be
simultaneously outside the operational
specification - maximum range of main
contact position is shown on Fig. 68b. All
four contact points on the main contacts
must be in touch with the fixed contacts.
