Transmission Network Performance Report 2005 - National Grid

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Transmission ReliabilityFY20051.5 Number of Disturbances• The following figure compares transmission outages distributed throughthe year for both FY2004 and FY2005. The blue line shows the outagesfor FY2004 and the red line shows the outages for FY2005. Thesenumbers represent the total number of disturbances, which were eithermomentary or sustained in nature.Figure 1-1: Cumulative Number of Outages by Month7006005004003002001000Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb MarFY2004 FY2005 5 YR AVG• The number of disturbances in FY2005 was higher than for FY2004.Although this represents a slight decrease in reliability performance overlast year, FY2005 performance was mostly consistent with the 5 yearAverage. This performance must be considered taking into account thatthe lightning season in FY2004 was significantly better than the 5 yearaverage while that in FY2005 was significantly worse.• The highest rate of incidence of outages occurred during warm weatherconditions with 58% of all outages occurring between May and August.Compared to FY2004, there was an increase of over 200% in lightninginitiated outages in FY2005 (an increase of 33% over the 5 YearAverage).• The following figure indicates the weekly profile of events in FY2005 inboth New England and New York. The green bars indicate the NewEngland events while the blue bars indicate New York events. Calloutsare used against weeks that had abnormally large number of outagesand identify the major causes for the performance. In FY2005 Lightningstorms were responsible for all the major event weeks.6 National Grid Performance Report
FY2005Transmission ReliabilityFigure 1-2: Weekly Number of Events in FY200560Weekly Number of Incidents - FY200550May 22-24,LightningNumber of Incidents403020Jul 2,LightningAug 20-21,LightningAug 29,Lightning100Wk1Wk3Wk5Wk7Wk9Wk11Wk13Wk15Wk17Wk19Wk21Wk23Wk25NEWk27Wk29Wk31Wk33NYWk35Wk37Wk39Wk41Wk43Wk45Wk47Wk49Wk51Wk53• TSAIFI is the average number of interruptions per circuit. It is calculated bydividing the total number of disturbances in a given period by the number ofcircuits. TSAIFI for FY2005 was 1.77. This indicates that each circuit had,on average, 1.177 disturbances last Year (equals 631 disturbances intotal). Of these disturbances 433 were momentary outages and 198 weresustained outages.Figure 1-3: 5 Year Trend of TSAIFITSAIFI1.41.21.00.80.60.40.20.0FY2001 FY2002 FY2003 FY2004 FY2005• With the exception of FY2004 which experienced a quiet lightningseason, TSAIFI for FY2005 is similar to performance in previous yearsand close to the 5 year average of 1.16.National Grid Performance Report 7
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Page 3 and 4: FY2005ContentsCONTENTSTransmission
Page 5 and 6: FY2005Transmission ReliabilityTrans
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Page 17 and 18: FY2005Transmission and CustomersTra
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Page 25 and 26: FY2005DevelopmentsDevelopmentsNatio
Page 27 and 28: FY2005DevelopmentsFigure 3-2 shows
Page 29 and 30: FY2005DevelopmentsThe lightning den
Page 31 and 32: FY2005DevelopmentsSome of the addit
Page 33 and 34: FY2005HVDCHVDCNational Grid Perform
Page 35 and 36: FY2005HVDCMost HVDC transmissions a
Page 37 and 38: FY2005Feedback andAdditional Inform
Page 39 and 40: FY2005Feedback and Additional Infor
Page 42: Feedback and Additional Information

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