Outage Rates, Durations and Element g ,Availability: AC circuit 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
2010-2013 TADS: AC Circuit Counts and Miles by Voltage Class
9%
2%
AC circuits by Voltage Class (TADS 2010‐2013)
66%
24%
AC circuit miles by Voltage Class (TADS 2010‐2013)
51%
15%5%
29%
RELIABILITY | ACCOUNTABILITY2
200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV
Average Annual Automatic Outage Rateper Line: Testing Homogeneity
1.20
Annual Outage Rate per Line by Voltage ClassAutomatic vs. Sustained Outages (2010‐2013)
0.50
0.77 0.76
0.99
0.60
0 420.51
0.580.60
0.80
1.00
1.20
0.300.42
0.35
0.00
0.20
0.40
200 299 kV 300 399 kV 400 599 kV 600 799 KV All AC i i
All pair-wise annual outage rate differences between
200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All AC circuits
Automatic Outages Sustained
All pair wise annual outage rate differences between voltage classes are statistically significant except• 300-399 kV and 400-599 kV (All Automatic outages)• 400-599 kV and 600-799 kV (Automatic Sustained)
RELIABILITY | ACCOUNTABILITY3
400 599 kV and 600 799 kV (Automatic Sustained)
Average Annual Automatic Outage Rate per 100 Miles by Voltage Class (2010-2013)
Annual Outage Rate per 100 Miles by Voltage ClassA t ti S t i d (2010 2013)
2.23 2.202.06
2 00
2.50
Automatic vs. Sustained (2010‐2013)
1.48
1.161.31
1.201.00
1.201.50
2.00
0.68
0.50
1.00
0.00200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All AC circuits
Automatic Outages Sustained
RELIABILITY | ACCOUNTABILITY4
g
Average Annual Outage Ratesper Line by Voltage Class (2010-2013)
2 7
TADS AC Circuits: Annual Outage Rates per Line (2010‐2013)
0.6
2 9
1.8
12.0
2.1
13.0
2.7
600 799 KV
All AC circuits
0 8
1.0
1.7
2.9
2.53.2
400‐599 kV
600‐799 KV
0.8
0.8
1.51.7
2.5
300‐399 kV
0.51.92.0
2.5
0 00 2 00 4 00 6 00 8 00 10 00 12 00 14 00
200‐299 kV
RELIABILITY | ACCOUNTABILITY5
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00
All Outages Non‐Automatic Planned Operational Automatic Sustained
Average Annual Outage Ratesper 100 Miles by Voltage Class (2010-2013)
TADS AC Circuits: Annual Outage Rates per 100 Miles (2010‐2013)
2.16.2
14.1
7.4
15.2
9.5
All AC circuits
1 5
1.2
3.3
3.4
4.8
14.1
6.3
400‐599 kV
600‐799 KV
2.2
1.5
4.34.8
7.0
300‐399 kV
2.28.5
9.011.3
0 0 2 0 4 0 6 0 8 0 10 0 12 0 14 0 16 0
200‐299 kV
RELIABILITY | ACCOUNTABILITY6
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0
All Outages Non‐Automatic Planned Operational Automatic Sustained
Average Outage Duration by Voltage Class (2010-2013)
Average Outage Duration (in Hours) b V lt Cl (2010 2013)
87 8796 101
109
100
120
by Voltage Class (2010‐2013)
87 87
39
6471 74
68
50 4860
80
30 3339
15
0
20
40
0200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All AC circuits
Automatic Sustained Planned Operational
RELIABILITY | ACCOUNTABILITY7
Average Annual Non-Operational Time per Lineby Voltage Class (2010-2013)
Average Annual Non‐Operational Time per Line (in Days) by Voltage Class (2010 2013)
16.416.0
18.0
(in Days) by Voltage Class (2010‐2013)
7 5
10.5
10.0
12.0
14.0
5.8
7.56.8
4.0
6.0
8.0
0.0
2.0
200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All AC circuits
RELIABILITY | ACCOUNTABILITY8
Mean Time of Continuous Operationby Voltage Class (2010-2013)
Mean Time of Continuous Operation (Days) for an AC Circuit by Voltage Class (TADS 2010‐2013)
142 144
110
131
120
140
160
60
80
100
27
0
20
40
60
All MTOCOs by voltage class are statistically distinct except for 200-299 kV and 300 399 kV lines
0200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All AC circuits
RELIABILITY | ACCOUNTABILITY9
299 kV and 300-399 kV lines
Mean Time of Continuous OperationExcluding Non-Automatic Outages
Mean Time of Continuous Operation excluding Non‐Automatic Outages for an AC circuit
698
587700
800
by Voltage Class (in Days)
453 456387
587
400
500
600
0
100
200
300
All MTOCOs between voltage classes are statistically distinct except for 300 399 kV and 400 599 kV lines
0200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All AC circuits
RELIABILITY | ACCOUNTABILITY10
for 300-399 kV and 400-599 kV lines
AC Circuit Unavailabilityby Voltage Class (2010-2013)
AC Circuit Unavailability by Outage Type by Voltage Class (2010‐2013)
0.6%
3 5%
4.0%
4.5%
5.0%
0 2%0.4%
1.6%
0.2%
0.5%
0 2%2.0%
2.5%
3.0%
3.5%
1.4% 1.6% 1.9%2.4%
1.5%
0.1%0.2% 0.2%0.1%
0.2%
0 0%
0.5%
1.0%
1.5%
0.0%200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All AC circuits
AC circuit Unavailability due to Sustained outages
AC circuit Unavailability due to Operational outages
RELIABILITY | ACCOUNTABILITY11
y p g
AC circuit Unavailability due to Planned outages
AC Circuit Availabilityby Voltage Class (2010-2013)
Transmission AC Circuit Availability by Voltage Class (TADS 2010 2013)
98.4%
97.9%98.1%98.5%
99.0%
by Voltage Class (TADS 2010‐2013)
97.1%
96 5%
97.0%
97.5%
98.0%
95.5%
95.0%
95.5%
96.0%
96.5%
94.0%
94.5%
95.0%
200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All AC circuits
RELIABILITY | ACCOUNTABILITY12
AC Circuit Unavailability by Year
AC Circuit Unavailability by Year( )
2.50%
(TADS 2010‐2013)
0.15%0.20%
0.24%0.15%0.17%
0.21%0.12%
0.13%1.50%
2.00%
1.35% 1.53% 1.67% 1.52%0.50%
1.00%
0.00%2010 2011 2012 2013
Planned outages Operational outages Automatic sustained outages
RELIABILITY | ACCOUNTABILITY13
Planned outages Operational outages Automatic sustained outages
200-299kV Lines: Unavailability by Month
RELIABILITY | ACCOUNTABILITY14
300-399kV Lines: Unavailability by Month
RELIABILITY | ACCOUNTABILITY15
400-599kV Lines: Unavailability by Month
RELIABILITY | ACCOUNTABILITY16
600-799kV Lines: Unavailability by Month
RELIABILITY | ACCOUNTABILITY17
AC Circuits: Unavailability by Month
RELIABILITY | ACCOUNTABILITY18
AC Circuits: Availability by Month
RELIABILITY | ACCOUNTABILITY19
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
RELIABILITY | ACCOUNTABILITY20
Outage Rates: Summary 1
• From 2010 to 2013, TADS contains records of 79,887 AC circuit outagesAC circuit outages 17,428 (22% of the total) are automatic outages; 10,174 (13% of the total) are sustained outages
52,632 (66% of the total) are planned outages and 9,827 (12% of the total) are operational outages
h l li i• The average annual outage rate per line is 2.7.
•By voltage class, the annual outage rate increases with lt l ith th ll t t t f 2 5voltage class, with the smallest outage rate of 2.5
outages per a 200‐299 kV line and the biggest outage rate of 13 0 outages per a 600‐799 kV line
RELIABILITY | ACCOUNTABILITY21
rate of 13.0 outages per a 600 799 kV line
Outage Rates: Summary 2
•Unlike other voltage classes, the operational outage rate for a 600‐799 kV line is 3 times greater than therate for a 600 799 kV line is 3 times greater than the planned outage rate
•About 89% of all operational outages in the 600‐799 kVAbout 89% of all operational outages in the 600 799 kV Voltage class have the operational cause code System Voltage Limit Mitigation
RELIABILITY | ACCOUNTABILITY22
Outage Durations: Summary
• From 2010 to 2013, combined AC circuit outage duration was 543.5 element‐years: 45.8 element‐years (8% of the total duration) was the total duration of automatic sustained outages
443.6 element‐years (82% of the total) was due to planned outages and 54.1 element‐years (10% of the total) due to operational outages
• The average sustained outage duration over all voltage classes was 39 hours the planned outage duration was 74 hours andwas 39 hours, the planned outage duration was 74 hours, and the operational outage duration 48 hours. There were significant differences in durations by outage types among the l lvoltage classes.
• The annual non‐operational time per line was the largest for 600‐799 kV lines (about 16 days) and the shortest for the 200‐
RELIABILITY | ACCOUNTABILITY23
600 799 kV lines (about 16 days) and the shortest for the 200299 lines (6 days), with the overall average of 7 days a year
AC Circuit Availability: Summary
• Mean Time of Continuous Operation per line was on average 131 days y Longest MTOCOs were for a 200‐299 kV line (142 days) and 300‐399 kV line (144 days) which are statistically equal
The smallest MTOCO (27 days) was for a 600‐799 kV lineThe smallest MTOCO (27 days) was for a 600 799 kV line
• For the last 4 years, overall AC circuit availability remained close to 98% (the lowest of 97.97% was in 2012)
• AC circuit unavailability was on average 1.9% with the largest unavailability of 4.5% for the 600‐799 kV voltage class
• 82% of overall AC circuit unavailability is due to planned• 82% of overall AC circuit unavailability is due to planned outages.
RELIABILITY | ACCOUNTABILITY24
RELIABILITY | ACCOUNTABILITY25
RELIABILITY | ACCOUNTABILITY26
2010-2013 TADS Data
AC circuit Outages (2010‐2013) 200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All AC circuitsNumber of lines 19144.0 7040.1 2511.4 451.0 29146.5Total miles 430873.4 247430.1 128345.9 38443.1 845092.5A li l th ( il ) 22 5 35 1 51 1 85 2 29 0Average line length (miles) 22.5 35.1 51.1 85.2 29.0Number of Automatic Outages 9630 5446 1905 447 17428
Sustained 5654 2976 1283 261 10174Momentary 3976 2470 622 186 7254
Total Automatic Outage Duration (Years) 19.1 11.3 12.7 2.6 45.8Average Sustained Outage Duration (Hours) 29.7 33.4 86.8 86.9 39.4Average Sustained Outage Duration (Hours) 29.7 33.4 86.8 86.9 39.4Annual Automatic Outage Rate per line 0.50 0.77 0.76 0.99 0.60
Sustained 0.30 0.42 0.51 0.58 0.35Number of Non‐Automatic Outages 38917 11978 6154 5410 62459
Planned 36533 10573 4202 1324 52632Operational 2384 1405 1952 4086 9827
Total Non‐Automatic Outage Duration (Years) 287.0 133.6 59.5 17.7 497.7Planned 268.4 116.1 48.3 10.7 443.6
Operational 18.6 17.4 11.2 7.0 54.1Average Non‐Automatic Outage Duration (Hours) 64.6 97.7 84.7 28.7 69.8
Planned 64.4 96.2 100.8 70.8 73.8O ti l 68 2 108 6 50 1 15 0 48 3Operational 68.2 108.6 50.1 15.0 48.3
Annual Non‐Automatic Outage Rate per line 2.03 1.70 2.45 12.00 2.14Planned 1.91 1.50 1.67 2.94 1.81
Operational 0.12 0.20 0.78 9.06 0.34
RELIABILITY | ACCOUNTABILITY27
2010-2013 TADS Data (continued)
AC circuit Outages (2010‐2013) 200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All AC circuitsAC circuit Outages (2010‐2013) 200‐299 kV 300‐399 kV 400‐599 kV 600‐799 KV All AC circuitsTotal Number of Outages 48547 17424 8059 5857 79887Total Outage Duration (Years) 306.1 144.9 72.2 20.3 543.5Average Outage Duration (Hours) 55.2 72.8 78.5 30.3 59.6Average Annual Non‐Operational Time per Line (Days) 5.8 7.5 10.5 16.4 6.8Annual Total Outage Rate per line 2.54 2.47 3.21 12.99 2.74g pAC circuit Unavailability due to Sustained outages 0.1% 0.2% 0.5% 0.6% 0.2%AC circuit Unavailability due to Planned outages 1.4% 1.6% 1.9% 2.4% 1.5%AC circuit Unavailability due to Operational outages 0.1% 0.2% 0.4% 1.6% 0.2%Transmission AC Circuit Availability 98.4% 97.9% 97.1% 95.5% 98.1%Mean Time between Operations per Line (Days) 141.6 144.4 110.5 26.8 130.7
Annual Automatic Outage Rate per 100 miles 2.2 2.2 1.5 1.2 2.1Sustained 1.3 1.2 1.0 0.7 1.2
Annual Non‐Automatic Outage Rate per 100 miles 9.0 4.8 4.8 14.1 7.4Planned 8.5 4.3 3.3 3.4 6.2
Operational 0.6 0.6 1.5 10.6 1.2l l ilAnnual Total Outage Rate per 100 miles 11.3 7.0 6.3 15.2 9.5
RELIABILITY | ACCOUNTABILITY28
2010-2013 TADS Data (continued)
TADS AC circuit Unavailability 2010 2011 2012 2013AC circuit Availability 98.3% 98.1% 98.0% 98.2%Transformer Availability 97.6% 97.1% 97.2% 97.6%Automatic sustained outages 0.17% 0.21% 0.12% 0.13%
Operational outages 0.15% 0.20% 0.24% 0.15%p gPlanned outages 1.35% 1.53% 1.67% 1.52%
Non‐Automatic Outages 1.50% 1.73% 1.91% 1.67%
All Outages 1.67% 1.94% 2.03% 1.80%Number of AC circuits 6975.1 7149.7 7475.1 7546.6Total hours 61101876 62631372 65661278.4 66108216Total automatic sustained outage duration (Hours) 104700.4 132150.7 79682.8 84501.9Total non‐automatic outage duration (Hours) 916359.6 1084927.1 1254195.4 1103157.6Total Operational outage duration (Hours) 91232.2 126072.6 157794.4 99188.4Total Planned outage duration (Hours) 825127.4 958854.6 1096401.0 1003969.2Total outage duration (Hours) 1021059.98 1217077.8 1333878.1 1187659.5
RELIABILITY | ACCOUNTABILITY29
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
RELIABILITY | ACCOUNTABILITY30
rates and the equality of the mean times were tested at the significance level of 0.05
Element Reliability Function
•
RELIABILITY | ACCOUNTABILITY31
Reliability Calculation (Example)
•
i (d ) ( )t time (days) R(t)10 0.9320 0.8730 0 8130 0.81100 0.49365 0.08500 0 03
RELIABILITY | ACCOUNTABILITY32
500 0.03
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)
RELIABILITY | ACCOUNTABILITY33