transformer outage rates, durations and … availability data...transformer voltage class: tads...

Outage Rates, Durations and Element g ,Availability: Transformer Automatic and Non-Automatic Outages by Voltage ClassAutomatic Outages by Voltage Class

Statistical Analysis Based on 2010-2013 TADS dataSvetlana Ekisheva Senior StatisticianSvetlana Ekisheva, Senior Statistician August 7, 2014

Transformer Voltage Class: TADS Definition 1

1. Element

The following are Elements for which TADS data are to beThe following are Elements for which TADS data are to be collected: 1. AC Circuits ≥ 200 kV (Overhead and Underground)

2 f i h 200 k l id l 2. Transformers with ≥ 200 kV low‐side voltage

3. AC/DC Back‐to‐Back Converters with ≥ 200 kV AC voltage, both sides

4. DC Circuits with ≥ +/‐200 kV DC voltage

An Element may also be referred to as a “TADS Element in the Manual. They have the same meaning.

htt // / /RAPA/t d /D t /2014 TADS Ahttp://www.nerc.com/pa/RAPA/tads/Documents/2014_TADS_Appendix_7%20041514.pdf

RELIABILITY | ACCOUNTABILITY2

Transformer Voltage Class: TADS Definition 13

• 13. Voltage Class

The following voltages classes will be used for reporting purposes:The following voltages classes will be used for reporting purposes: 1. 200‐299 kV

2. 300‐399 kV

3 00 99 k 3. 400‐499 kV

4. 500‐599 kV

5. 600‐699 kV

For Transformers, the Voltage Class reported will be the high‐side voltage, even though the cut‐off voltage used in the definition is referenced on the low side Voltages are operating voltagesreferenced on the low‐side. Voltages are operating voltages.http://www.nerc.com/pa/RAPA/tads/Documents/2014_TADS_Appendix_7%20041514.pdf


2010-2013 TADS: Transformer Counts by Voltage Class

Transformers by Voltage Class (TADS 2010‐2013)

4%23%

13%

60%

200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV

For the 200-299 kV voltage class only a subset of transformers (115.0 t f f 2010 2014) i t d i TADS


transformer-years for 2010-2014) is reported in TADS

Transformer Automatic Outages(TADS 2010-2013)

Number of Transformer Outages (2010‐2013)

243

193

250

300

136

105100

150

200

14

62

3110

4929

0

50

100

0200‐299 kV 300‐399 kV 400‐599 kV 600‐799 kV All Transformers

Automatic Sustained


Average Annual Automatic Outage Rateper Transformer: Testing Homogeneity

0 120.14

Annual Outage Rate per Transformer by Voltage Class: Automatic vs. Sustained Outages (2010‐2013)

0.12

0.090.08 0.08 0.080.09

0.070.06

0.080.070.08

0.10

0.12

0 00

0.02

0.04

0.06

0.00200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All Transformers

Automatic Outages Sustained

• All pair-wise annual automatic outage rate differences between voltage classes are not statistically significant

• All pair-wise annual sustained outage rate differences between lt l t t ti ti ll i ifi t


voltage classes are not statistically significant

Average Annual Outage Ratesper Transformer by Voltage Class (2010-2013)

TADS Transformers: Annual Outage Rates per Transformer(2010‐2013)

0.11.3

1.6

3.0

1.7

All Transformers

0.1

1.3

2.4

1.7

2.9

1.8

3.0

400‐599 kV

600‐799 KV

0.1

0.1

0.91.01.1

300‐399 kV

0.10.30.4

0.5

0 0 0 5 1 0 1 5 2 0 2 5 3 0 3 5

200‐299 kV


0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

All Outages Non‐Automatic Planned Operational Automatic Sustained

Average Outage Duration by Voltage Class (2010-2013)

Average Transformer Outage Duration (in Days) by Voltage Class (2010 2013)

17.6 17.2

14 6

17.7

16 0

18.0

20.0

by Voltage Class (2010‐2013)

9.5

14.6

11.6

8.010.0

12.0

14.0

16.0

0 3

6.95.3

3.35.1

0 5

3.5

8.0

5.7

2 0

4.0

6.0

8.0

0.3 0.50.0

2.0

200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All Transformers

Automatic Sustained Planned Operational


Automatic Sustained Planned Operational

Average Annual Non-Operational Time per Transformerby Voltage Class (2010-2013)

Average Annual Non‐Operational Time per T f (i D ) b V lt Cl (2010 2013)

13.414.0

16.0

Transformer (in Days) by Voltage Class (2010‐2013)

9.2 9.3 9.610.0

12.0

3.94.0

6.0

8.0

0.0

2.0



200 299 kV 300 399 kV 400 599 kV 600 799 KV All Transformers

Mean Time of Continuous Operationby Voltage Class (2010-2013)

Mean Time of Continuous Operation (Days) for a Transformer by Voltage Class (TADS 2010‐2013)

680.8

600.0

700.0

800.0

316.2300 0

400.0

500.0

202.2

116.8

206.2

0 0

100.0

200.0

300.0

All MTOCOs by voltage class are statistically distinct

0.0200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All Transformers


Mean Time of Continuous OperationExcluding Non-Automatic Outages (2010-2013)

Mean Time of Continuous Operation excluding Non‐Operational Outages for a Transformer by

V l Cl (i Y )

13 6

16.3

14.816.0

18.0

Voltage Class (in Years)

11.5

13.612.7

10.0

12.0

14.0

4.0

6.0

8.0

0.0

2.0



All MTOCOs by voltage class are statistically equivalent

Transformer Unavailabilityby Voltage Class (2010-2013)

Transformer Unavailability by Outage Type by Voltage Class (2010 2013)

0.4%

3 0%

3.5%

4.0%

Class (2010‐2013)

0.6% 0.3%

1.2%

0.5%0.2% 0.3% 0.3%

1.5%

2.0%

2.5%

3.0%

1.0%1.7% 1.9% 2.1% 1.9%0.01%0.01%

0.0%

0.5%

1.0%


Transformer Unavailability due to Sustained outages

Transformer Unavailability due to Operational outages


Transformer Unavailability due to Planned outages

Transformer Availabilityby Voltage Class (2010-2013)

TADS Transformer Availability (2010‐2013)

98.9%

98.5%

99.0%

99.5%

97.5% 97.5% 97.4%

97 0%

97.5%

98.0%

96.3%

96.0%

96.5%

97.0%

95.0%

95.5%



Transformer Unavailability by Year

Transformer Unavailability by Year ( )

3.00%

3.50%

(TADS 2010‐2013)

0.34%0.43%

0.57%

0.64%

0.33%

0.44% 0.06%

0.25%

1 50%

2.00%

2.50%

1.73%2.06% 2.18%

1.49%0.50%

1.00%

1.50%

0.00%2010 2011 2012 2013

Planned outages Operational outages Automatic sustained outages


200-299kV Transformers: Unavailability by Month

For the 200 299 kV voltage class only a subset of transformers (115 0


For the 200-299 kV voltage class only a subset of transformers (115.0 transformer-years for 2010-2014) is reported in TADS

Transformers: Unavailability by Month


Transformers: Availability by Month


AC Circuit vs. TransformerAvailability by Year

TADS Element Availability by Year

98.3%

98.1%98.0%

98.2%

98 0%98.2%98.4%98.6%

97.6%

97 1%97.2%

97.6%

97.4%97.6%97.8%98.0%

97.1%

96.6%96.8%97.0%97.2%

96.4%2010 2011 2012 2013

AC circuit Availability Transformer Availability


Outage Rates: Summary

• From 2010 to 2013, TADS contains records of 4,951 Transformer outagesTransformer outages 243 (5% of the total) are automatic outages; 193 (4% of the total) are sustained outages

3,794 (77% of the total) are planned outages and 914 (18% of the total) are operational outages

h l f i• The average annual outage rate per transformer is 1.7.

•By voltage class, the annual outage rate increases with lt l ith th ll t t t f 0 5voltage class, with the smallest outage rate of 0.5

outages per 200‐299 kV transformer and the biggest outage rate of 3 0 outages per 600‐799 kV transformer


outage rate of 3.0 outages per 600 799 kV transformer

Outage Durations: Summary

• From 2010 to 2013, combined Transformer outage duration was 75.5 years (out of 2871.8 transformer‐years): 7.7 years (10% of the total duration) was the duration of automatic sustained outages

53.4 years (71% of the total) was due to planned outages and 14.4 years (19% of the total) due to operational outages

• Average sustained outage duration over all voltage classes was 14 6 days the planned outage duration was 5 1 days and the14.6 days, the planned outage duration was 5.1 days, and the operational outage duration 5.7 days. There were significant differences in durations by outage types among the voltage lclasses.

• The annual non‐operational time per transformer was the largest for the 600‐799 kV (about 13 days) and the shortest for the 200‐


for the 600 799 kV (about 13 days) and the shortest for the 200299 kV (4 days), with the overall average of 10 days a year.

Transformer Availability: Summary

• Mean Time of Continuous Operation per transformer was on average 206 days g y The longest MTOCO was for a 200‐299 kV transformer (681 days)

The smallest MTOCO (117 days) was for a 600‐799 kV transformer

F th l t 4 ll t f il bilit b• For the last 4 years, overall transformer availability was above 97%.

• Transformer unavailability was on average 2.6% with the largest y g gunavailability of 3.7% for the 600‐799 kV voltage class

• 71% of overall transformer unavailability is due to planned toutages.


2010-2013 TADS Data

Transformer Outages (2010‐2013) 200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All TransformersNumber of transformers 115.0 667.3 1719.0 370.5 2871.8Number of Automatic Outages 14 62 136 31 243Number of Automatic Outages 14 62 136 31 243

Sustained 10 49 105 29 193Momentary 4 13 31 2 50

Total Automatic Outage Duration (Days) 3.4 465.0 1849.6 498.3 2816.4Average Sustained Outage Duration (Days) 0.3 9.5 17.6 17.2 14.6Annual Automatic Outage Rate per transformer 0.12 0.09 0.08 0.08 0.08Annual Automatic Outage Rate per transformer 0.12 0.09 0.08 0.08 0.08

Sustained 0.09 0.07 0.06 0.08 0.07Number of Non‐Automatic Outages 47 689 2888 1084 4708

Planned 38 605 2265 886 3794Operational 9 84 623 198 914

Total Non‐Automatic Outage Duration (Days) 443.5 5668.3 14132.7 4484.2 24728.7Planned 439.4 4185.7 11974.2 2890.8 19490.1

Operational 4.1 1482.7 2158.5 1593.3 5238.6Average Non‐Automatic Outage Duration (Days) 9.4 8.2 4.9 4.1 5.3

Planned 11.6 6.9 5.3 3.3 5.1Operational 0.5 17.7 3.5 8.0 5.7

Annual Non‐Automatic Outage Rate per transformer 0.41 1.03 1.68 2.93 1.64Planned 0.33 0.91 1.32 2.39 1.32

Operational 0.08 0.13 0.36 0.53 0.32


2010-2013 TADS Data (continued)

Transformer Outages (2010‐2013) 200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All TransformersTotal Number of Outages 61 751 3024 1115 4951Total Outage Duration (Days) 446.8 6133.4 15982.4 4982.5 27545.1g ( y )Average Outage Duration (Hours) 175.8 196.0 126.8 107.2 133.5Annual Total Outage Rate per transformer 0.53 1.13 1.76 3.01 1.72Transformer Unavailability due to Sustained outages 0.01% 0.19% 0.29% 0.37% 0.27%Transformer Unavailability due to Planned outages 1.05% 1.72% 1.91% 2.14% 1.86%Transformer Unavailability due to Operational outages 0.01% 0.61% 0.34% 1.18% 0.50%Transformer Availability 98.9% 97.5% 97.5% 96.3% 97.4%Mean Time of Continuous Operation per Transformer (Days) 680.8 316.2 202.2 116.8 206.2Average Annual Non‐Operational Time per Transformer (Days) 3.9 9.2 9.3 13.4 9.6


2010-2013 TADS Data (continued)

TADS Transformer Unavailability 2010 2011 2012 2013Automatic sustained outages 0.33% 0.44% 0.06% 0.25%Non‐Automatic Outages 2.08% 2.48% 2.75% 2.13%

Operational outages 0.34% 0.43% 0.57% 0.64%Pl d t 1 73% 2 06% 2 18% 1 49%Planned outages 1.73% 2.06% 2.18% 1.49%

All Outages 2.41% 2.92% 2.80% 2.38%Transformer Availability 97.59% 97.08% 97.20% 97.62%Number of Transformers 691.3 705.2 713.4 761.9Total hours 6055788 6177552 6266505.6 6674244Total automatic sustained outage duration (Hours) 20185 77 26994 18 3525 95 16887 2Total automatic sustained outage duration (Hours) 20185.77 26994.18 3525.95 16887.2Total non‐automatic outage duration (Hours) 125739.1 153402.9 172213.1 142133.5Total Operational outage duration (Hours) 20866.7 26309.5 35836.3 42714.2Total Planned outage duration (Hours) 104872.4 127093.4 136376.9 99419.4Total outage duration 145924.8367 180397.1 175739.1 159020.7


Statistical Methodology

• For comparison of the expected outage rates (year‐over‐year and for different voltage classes) the testing the homogeneityand for different voltage classes), the testing the homogeneity of Poisson frequencies was used

• The tests are valid under assumption of the Poisson distribution of the occurrences of outages

• For comparison of the mean times of continuous operations (MTOCO) the ratio tests for two exponential means were used(MTOCO), the ratio tests for two exponential means were used

• The tests are valid under assumption of the Poisson distribution of the occurrences of outages; and Time of Continuous Operation has the exponential distribution

• The null hypotheses on the equality of the expected outage rates and the equality of the mean times were tested at the


rates and the equality of the mean times were tested at the significance level of 0.05

Element Reliability Function

•


Reliability Calculation (Example)

•

t time (days) R(t)10 0.9520 0.9130 0 8630 0.86100 0.61365 0.16500 0 08


500 0.08

References

• P.G. Hoel. Testing the homogeneity of Poisson Frequencies. Annals of Mathematical Statistics (1945) pp 362‐368Annals of Mathematical Statistics (1945), pp. 362 368.

• L. Bain and M. Englehardt. Statistical Analysis of Reliability and Life‐Testing Models: Theory and Methods, Second Edition. CRC Press (1991)
