Draw Rod System - ABB GSB 245 Technical Manual

14 T R A N S F O R M E R B U S H I N G S T Y P E G S B T E C H N I C A L G U I D E

Draw rod system

The draw rod system offers the following advantages
compared to other methods used for high currents:
• No manholes required in the transformer tank.
• The bushing tube is used as a conductor.
• No special supports required in the transformer, as is the
case with plug contacts.
• Perfect guiding of the bushing into the transformer.
The center tube of the bushing is used as conductor. The
transformer leads are fitted with cable lugs, bolted to a
bottom contact. This contact is tightened to the lower end
of the bushing tube by a steel draw rod. The upper end of
this rod is bolted to a spring device, which consists of two
concentric tubes of different materials, designed to give the
required contact load at all temperatures. The draw rod is
divided into two parts at level with the flange. The lower
draw rod includes bottom contact, guide cone, rod and joint.
The upper draw rod consists of compensating device, rods,
joints, washer and nut.
Threaded
hole M8 for
pulling wire
25
Additional
joint on
request
H1
min 200
64 45
—
09 Draw rod system.
∅152.5
D2
125
L2
60
L5
Bottom contact type 1
M12 (4x)
(standard)
If required to meet the transport conditions, an additional
joint can be positioned at any desired level below the flange.
This must be stated in the order. The lower part with contact
and end-shield can then be secured to the transport cover
during transport and storage of the transformer.
Bottom contacts with 4 threaded holes for cable lugs are
available. The bottom contacts are made of copper in one
piece. There are standard end-shields for type 1 bottom
contacts available; see Standard end shield and Table 8. The
type 2 bottom contact is intended to use with customized
shields, using three M10 holes at diameter 125 mm for shield
assembly. Special bottom contacts are available on request.
—
Table 7. Draw rod system.
Cat. No. Type of draw rod
1ZSC999006 Lower draw rod
1ZSC999007 Upper draw rod
Bottom contact type 2
(only for customized end-shields
and draw rod)