ure
Edison Electric Institute
Meeting #020
TSAC Round Table Question #19
April 5, 2005 Do you believe that the failure rate of
transformers is increasing within your
company?
17%
77%
6%
Increasing
Not Changing signifcantly
Decreaasing Do you believe that the failure rate of
circuit breakers is increasing within your
company?
29%
71%
0%
Increasing
Not Changing signifcantly
Decreaasing Do you have an active program to replace
aging substation transformers?
18%
82%
YES
NO What do you estimate is the percent
replacement rate of substation
transformers prior to equipment failure?
0
0.5
1
1.5
2
2.5
<1%
1-5%
>5%
Percent Replacement Rate
N
u
m
b
e
r
o
f
U
t
ilt
ie
s Do you have an active program to replace
aging substation circuit breakers?
65%
35%
YES
NO What do you estimate is the percent
replacement rate of substation circuit breakers
prior to equipment failure?
0
1
2
3
4
5
6
7
>1%
1-5%
>5%
Percent Replacement Rate
N
u
mb
e
r
o
f
U
t
ilit
ie
s What are the criteria used within your company
when considering replacement of substation
transformers and circuit breakers?
0
2
4
6
8
10
12
14
Age
Oil analysis
History of
equipment faults
Experience w ith
similar units
Other
N
u
m
b
e
r
of
U
t
ilit
ie
s How many spare transmission substation
transformers do you maintain with 345/500/765
kV primary?
0
1
2
3
4
5
6
7
8
9
<2%
2 - 4 %
>4%-6%
>6%
Percent Transmission Transformer Spares
N
u
m
b
e
r
o
f
U
t
ilt
ie
s How many spare transmission substation
transformers do you maintain with 115/138/161
kV primary?
0
1
2
3
4
5
6
7
8
9
<2%
2 - 4 %
>4%-6%
>6%
Percent Transmission Transformer Spares
N
u
mb
e
r
o
f
U
t
ilit
ie
s How many spare distribution substation
transformers do you maintain rated 10MVA
ONAN and smaller without LTC?
0
1
2
3
4
5
6
7
8
<2%
2 - 4 %
>4%-6%
>6%
Percent Distribution Transformer Spares
N
u
m
b
e
r
o
f
U
t
ilit
ie
s How many spare distribution substation
transformers do you maintain rated 10MVA
ONAN and larger with LTC?
0
1
2
3
4
5
6
7
<2%
2 - 4 %
>4%-6%
>6%
Percent Distribution Substation Transformer Spares
N
u
m
b
e
r
o
f
U
t
ilit
ie
s How many spare circuit breakers do you
maintain for 345/500/765 kV?
0
2
4
6
8
10
12
<2%
2 - 4 %
>4%-6%
>6%
Percent Circuit Breaker Spares
N
u
m
b
e
r
o
f
U
t
ilit
ie
s How many spare circuit breakers do you
maintain for 69/115/138/161/230 kV?
0
2
4
6
8
10
12
14
<2%
2 - 4 %
>4%-6%
>6%
Percent Circuit Breaker Spares
N
u
mb
e
r
o
f
U
t
ilit
ie
s Do you feel that your company has a sufficient
inventory of spare transmission substation
transformers?
67%
33%
YES
NO Do you feel that your company has a sufficient
inventory of spare distribution substation
transformers?
86%
14%
YES
NO Do you feel that your company has a sufficient
inventory of spare transmission circuit breakers?
73%
27%
YES
NO Do you feel that your company has a sufficient
inventory of spare distribution circuit breakers?
79%
21%
YES
NO