1 sunrise powerlink and southwest powerlink reliability performance evaluation double line outage...
TRANSCRIPT
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Sunrise Powerlink and Southwest Powerlink Reliability Performance Evaluation
Double Line Outage Probability Analysis
March 6, 2008
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RPEWG and RS Recommendation
After reviewing SDG&E’s report, both the RS and RPEWG recommend that the proposed path (4 miles – 12 towers) for the Sunrise Powerlink and Southwest Powerlink double line outage analysis be approved for the category upgrade to Category D with cascading allowed.
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Step 1: Project (Facility) Description
SDG&E has proposed a new 500 kV transmission line called the Sunrise Powerlink (SRPL) that will connect the existing Imperial Valley substation, near El Centro, California to a new “Central” substation located in a central part of San Diego County.
The proposed path for the Sunrise Powerlink would be in the same right of way as the Imperial Valley - Miguel line for approximately 4 miles. This route would contain approximately 12 towers.
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Proposed and Alternative Paths
Proposed Path – approximately 4 miles Alternative Path – approximately 36 miles
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12 Tower Structures
Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7
Tower 50281 Tower 50280 Tower 50279
Tower 50273Tower 50276 Tower 50274Tower 50275
Tower 50277Tower 50278
Tower 50272 Tower 50271 Tower 50270
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Step 2: Outage Database – The Sample
SWPL is SDG&E’s only 500 kV transmission line, therefore outage data was collected on the Imperial Valley - Miguel portion of SWPL.
With thirteen years of outage data (1995 - 2007) available, SDG&E concluded that of the 44 forced outages on the Imperial Valley - Miguel line there was only one event that occurred on the proposed shared right of way during these years.
SDG&E determined that using historical 500 kV data from the Palo Verde Hub to North Gila Performance Category Upgrade Request report by Arizona Public Service (APS) would be appropriate.
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Step 3: Zero Events - Corrected MTBF
MTBF is 928 years
PT, PL, and PH are calculated using zero(0) events.
SDG&E feels that after reviewing the data from the Robust Line Design, the MTBF will tend towards this value.
Event Cause P1 (events/year) MTBF1 (years)
PT Historical Terminal 0 0
PL Historical Line 0 0
PIND Independent 0.0010 968.7053
PH Human 0 0
PB BF & M 0.0000458 21854.375
PTOTAL Total 0.0011 927.5895
Summary of Results (Corrected)
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One Event - Corrected MTBF
MTBF is 21 years PT , PL, and PH are calculated using one (1) event.
The reason that there are two sets of values for the MTBF, is because there is not enough data to calculate definite values.
Event Cause P2(events/year) MTBF2(years)
PT Historical Terminal 0.025 >40
PL Historical Line 0.0204 >49
PIND Independent 0.0010 968.7053
PH Human < .0013 >775
PB BF & M 0.0000458 21854.375
PTOTAL Total 0.0478 20.9301
Summary of Results (Corrected)
Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7
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Step 4: Risk Factor SummaryRisk Risk Factor
R1 Fire affecting both lines Low Risk
R2 One tower falling into another line Low Risk
R3 Conductor from one line being dragged into another line Low Risk
R4 Lightening strikes tripping both lines Low Risk
R5 Aircraft flying into both lines Low Risk
R6 Station related problems resulting in loss of two lines for a single event
Low Risk
R7 Natural disasters Low Risk
R8 Loss of two lines due to an overhead crossing Low Risk
R9 Loss of two lines due to vandalism/malicious acts Low Risk
R10 Flashover to vegetation Low Risk
R11 Single breaker failure causing loss of two lines Low Risk
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The exposure to the system is estimated to be, at worst case, 675 hours per year or 7.71% per year, based on planning scenarios.
However, the likelihood of this exposure due to operational conditions will be significantly less
Step 5: Exposure Analysis
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SDG&E Load Duration Curve
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% of Year
MW
2006 Actual Load 2006 Forecast Load2010 Forecast Load Load
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The results of the analysis indicated that to meet Category C criteria, a load drop scheme to reduce SDG&E import to approximately 3100 MW would be required for the N-2 loss of both 500 kV lines.
Thus, from an SDG&E import level of 4100 MW, approximately 1000 MW would need to shed.
The limiting factors are the thermal ratings of lines in CFE and SCE.
Possible voltage collapse was seen when imports were above 3700 MW.
Step 6: Consequence of an Outage
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Step 7: Report
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Performance Evaluation Conclusions The Proposed Path was recommended for Category D with
cascading because: Probability of occurrence is extremely low as indicated by MTBF
and Robust Line Design analysis. Cascading may occur under planning scenarios, but is not
expected during normal operating conditions. SDG&E importing approximately 4100 MW in 2010, 5000 MW load,
and only 900 MW of internal generation. SDG&E internal generation capability is expected to be almost 3000
MW in 2010. With an additional 400 MW of generation online the possibility of
cascading was significantly reduced
The proposed path is in the same right of way for 4 miles(12 towers).
The lines terminate at separate substations on the west end. The lines will have diverse and redundant relaying schemes.
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Project Timeline
RPEWG Approval December 19, 2007
Reliability Subcommittee Approval January 10, 2008
Planning Coordination Committee March 6, 2008
WECC Board of Directors April 2008