1. Designs have a 50,000 Amps RMS. Symmetrical Rating (except 3A 17.2kV, which was tested at 44kA maximum).
2. Current ratings shown in chart above are achieved by using a parallel combination of two fuses (order two fuses). To facilitate equal sharing of the
interrupting duty, the two fuses should be resistance matched (± 2%) and be mounted such that the current paths to and from each fuse are symmetrical.
3. Tabulated Maximum Total I
2
t values are for currents of 50,000 amperes at the nominal voltage of the fuse (except for fuses having a rated maximum
voltage of 8.8kV, in which case the maximum total I
2
t values are at 8.8kV). Fuses that have a rated maximum voltage higher than their nominal voltage
rating will have a higher I
2
t let-through when applied at voltages up to these higher values. For example, maximum total I
2
t values are increased by
approximately 30% when 8.3kV fuses are applied at 10kV and approximately 25% when 15.5kV fuses are used at 17.2kV.
4. Maximum total I
2
t values are reduced for currents below 50,000A. For example, at 10,000A, maximum total I
2
t values are approximately 15% less than
the published values.
5. Peak arc voltages quoted are for 50,000A currents at the rated maximum voltage listed. Reduced currents and voltages will reduce the peak arc voltage.
Consult the factory for further information.
6. Maximum continuous currents at higher ambient temperatures, and in confining enclosures:
These may be determined by derating the fuses by .2% per degree C over 25° C (for example, at 85° C the derating would be
60 x .2 = 12%, making the maximum continuous current of a 30A fuse 41 x .88 = 36.1A).
When fuses are applied in a confining enclosure, such as a drywell canister, additional derating of a fuse’s maximum continuous current is
necessary. Specifically, the maximum continuous current for fuses used in a dry-well canister, with the canister completely submerged in oil,
will be reduced by an additional 2% (3% for fuses having a rated maximum voltage of 8.8kV). When calculating the derating for temperature,
as described above, the temperature of the oil surrounding the canister should be used. For other types of enclosures, please consult the factory.
7. Reduction in the long time melting current of the fuses (approximately one hour and longer) due to higher ambient temperatures and use in enclosures
is the same as described above for “Maximum Continuous Current”. See time-current characteristics for melting characteristics in this time region.
8. The 2.2"-dia. 80A and 160A (paralleled 80A) fuses have an RMAT of 140° C at a reduced rated maximum voltage of 5.5kV.
www.tnb.com
United States
Tel: 901.252.8000
800.816.7809
Fax: 901.252.1354
Technical Services
Tel: 888.862.3289
H-73
Trans-Guard FX Fuse
Power & High Voltage —
Current-Limiting Fuses
Recommended Trans-Guard
®
FX Mounted in a Standard Drywell Canister in Oil (at a max. oil temp. of 100° C)
RECOMMENDED FUSE CURRENT RATINGS (AMPERES)
FUSE VOLTAGE
1-PHASE
TRANSFORMER
kVA
5.5kV
8.3kV
15.5kV
23kV
®
TRANSFORMER 1-PHASE VOLTAGE RATING (kV) PHASE-TO-GROUND
2.4
A
B
A
4.16
B
A
4.8
B
A
7.2
B
A
7.62
B
A
12
B
A
14.4
B
A
16
B
A
19.9
B
10
15
25
37.5
50
75
100
167
250
333
500
750
1000
6
b
8
18
20
30
50
65
100*
8
12
20
30
40
75
80*
8
12
18
25
30
65
80*
6
a
6
12
18
20
40
50
80*
8
b
12
b
18
20
25
50
80*
100*
3
6
10
18
20
30
40
65
8
10
12
20
30
50
60*
3
a
3
6
10
12
20
25
50
60*
100*
10
12
20
30
50
60*
3
a
3
6
8
12
20
25
50
60*
100*
8
12
b
20
25
40
60*
80*
3
a
3
a
3
6
6
12
18
25
40
60*
80*
8
10
18
20
30
50
80*
3
a
3
a
3
6
a
6
10
12
25
40
50
80*
10
b
18
20
25
40
60*
100*
3
a
3
a
3
6
a
6
8
12
20
30
40
60*
100*
12
18
20
40
6
a
6
a
6
a
6
a
6
a
6
8
18
25
30
50
Recommended 8.3kV Trans-Guard
®
FX Mounted in 15.5kV Drywell Canister in Oil (at a max. oil temp. of 100° C)
RECOMMENDED FUSE CURRENT RATINGS (AMPERES)
FUSE VOLTAGE
1-PHASE
TRANSFORMER
kVA
8.3kV
TRANSFORMER 1-PHASE VOLTAGE RATING (kV) PHASE-TO-GROUND
2.4
A
B
A
4.16
B
A
4.8
B
A
7.2
B
A
7.62
B
75
100
167
250
333
500
†
65
X
†
160*
80
80
160*
65
80
130*
160*
80
130*
160*
80
X
†
160*
80
130*
160*
65
65
X
†
130*
65
65
X
†
130*
X=Use an 8.3kV Drywell Canister. See top chart for fuse recommendations.
Notes:
Column A = 140–200% of transformer rating and Column B = 200–300% of transformer rating.
Fuses recommended in bottom chart must be mounted in a 15.5kV mounting code 5 drywell canister.
Recommended fuses meet inrush criteria of 12 times transformer full load current for .1 second and 25 times transformer full load current for .01 second. Fuses also meet cold load pickup
criteria of six times transformer full load current for 1 second and three times transformer full load current for 10 seconds.
* Indicates parallel fuse applications.
a Fuse allows greater than 300% of transformer rating.
b Fuse allows greater than 200% of transformer rating.
H-74
United States
Tel: 901.252.8000
800.816.7809
Fax: 901.252.1354
Technical Services
Tel: 888.862.3289
www.tnb.com
Trans-Guard FX Fuse
Power & High Voltage —
Current-Limiting Fuses
Recommended Trans-Guard
®
FX Mounted in a Standard Drywell Canister in Oil (at a max. oil temp. of 100° C)
RECOMMENDED FUSE CURRENT RATINGS (AMPERES)
FUSE VOLTAGE
3-PHASE
TRANSFORMER
kVA
5.5kV
8.3kV
15.5kV
23kV
®
TRANSFORMER 3-PHASE VOLTAGE RATING (kV) PHASE-TO-PHASE
2.4
A
B
A
4.16
B
A
4.8
B
7.2–7.96
A
B
A
8.32
B
A
12.47
B
13.2–14.4
A
B
A
20.8
B
22.9–24.9
C
A
B
A
34.5
C
B
15
22.5
30
45
75
100
112.5
150
200
225
300
500
750
1000
1500
2000
8
10
18
25
40
40
50
75
80*
6
10
18
20
40
50
65
80*
100*
8
18
20
20
25
40
40
65
100*
3
6
6
12
20
25
30
40
65
75
80*
8
b
12
18
20
25
30
40
50
80*
3
6
a
6
10
18
20
25
40
50
65
80*
8
12
b
12
18
20
25
30
60*
80*
3
a
3
6
a
6
12
18
18
20
30
40
50
80*
8
b
10
12
b
18
20
20
30
50
80*
3
a
3
3
6
10
12
18
20
25
30
40
80*
8
b
10
12
18
20
30
50
60*
3
a
3
a
3
a
3
6
8
10
18
20
20
25
50
80*
100*
6
10
b
12
b
12
20
30
50
60*
100*
3
a
3
a
3
a
3
6
8
8
12
18
20
25
40
60*
80*
8
8
12
20
25
40
6
a
6
a
6
a
6
a
6
a
6
a
6
6
10
12
18
25
40
8
12
b
18
25
40
50
6
a
6
a
6
a
6
a
6
a
6
a
6
a
6
8
10
18
25
40
12
18
20
40
50
6
a
6
a
6
a
6
a
6
a
6
a
6
a
6
a
6
6
8
18
25
30
Recommended 8.3kV Trans-Guard
®
FX Mounted in 15.5kV Drywell Canister in Oil (at a max. oil temp. of 100° C)
RECOMMENDED FUSE CURRENT RATINGS (AMPERES)
FUSE VOLTAGE
3-PHASE
TRANSFORMER
kVA
8.3kV
TRANSFORMER 3-PHASE VOLTAGE RATING (kV) PHASE-TO-PHASE
2.4
A
B
A
4.16
B
A
4.8
B
A
7.2–7.96
B
A
8.32
B
112.5
150
200
225
300
500
750
1000
1500
†
80
80
130
b
*
160*
65
80
X
†
130*
160*
65
X
†
160*
65
65
80
160*
80
130*
160*
65
80
130*
65
80
c
130*
160
c
*
80
c
130*
160
c
*
80
c
130
b
*
130*
80
c
130*
160
c
*
X=Use an 8.3kV Drywell Canister. See top chart for fuse recommendations.
Notes:
Column A = 140–200% of transformer rating and Column B = 200–300% of transformer rating.
Fuses recommended in bottom chart must be mounted in a 15.5kV mounting code 5 drywell canister.
Recommended fuses meet inrush criteria of 12 times transformer full load current for .1 second and 25 times transformer full load current for .01 second. Fuses also meet cold load pickup
criteria of 6 times transformer full load current for 1 second and 3 times transformer full load current for 10 seconds.
* Indicates parallel fuse applications.
a Fuse allows greater than 300% of transformer rating.
b Fuse allows greater than 200% of transformer rating.
c Recommendations limited to gndY-gndY transformers with no more than 50% delta connected secondary load. Phase-to-ground rated fuses are frequently recommended for gndY-gndY
three phase transformers. In some cases, the fuses recommended in bottom chart may be suitable for use with transformers that are not gndY-gndY (contact the factory further information).
