ABB GSA-OO, Technical Manual

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12 TR A N S FOR M E R BUS H I NG S T Y PE G SA - OO T EC H N I C A L G U I D E
—
Conductor loading
Overloading of bushings
If the conductor for the bushing is selected for 120 % of the
rated current of the transformer, the bushing is considered
to be able to withstand the overload conditions stated in
IEC 60076-7 without further clarifications or tests,
according to IEC 60137.
Short-time current
The rated thermal short-time current (I
th
) is calculated
according to IEC 60137.
Table 7.
Conductor
Rated
current
A
Area
mm
2
Short-time current (I
th
)
kA, rms
Dynamic
current (I
d
)
kA, peak 1 s 2 s
Solid rod
Ø 58 mm 2500.. 1600 2642 100 100 315
Stranded
draw-lead
2000.. 1250 1200 89 63 157
The GSA-OO bushings is heat run tested with solid
conductors and 1200 mm
2 stranded cable. The test currents
together with calculated values for different stranded
cables are given in the table below:
Table 6.
Bushing Conductor
Tested permissible
current
Calculated
permissible
current
A
IEC
A
IEEE
A
LF 135 073 Solid rod ø 58 mm 2500 2500
Stranded cable
1200 mm 2 2000 2000
900 mm
2
1500
450 mm
2
1000
150 mm 2 500
LF 135 123 Solid rod ø 58 mm 2000 2000
Stranded cable
1200 mm
2
1600 1600
900 mm
2
1200
450 mm 2 850
150 mm
2
450
LF 135 145 Solid rod ø 58 mm 2000 2000
Stranded cable
1200 mm
2
1600 1600
900 mm 2 1200
450 mm
2
850
150 mm 2 450
LF 135 170 Solid rod ø 58 mm 2000 2000
Stranded cable
1200 mm 2 1600 1600
900 mm
2
1200
450 mm 2 850
150 mm
2
450
LF 135 245 Solid rod ø 58 mm 1600 1600
Stranded cable
1200 mm
2
1250 1250
900 mm 2 950
450 mm
2
650
150 mm
2
350