Transend - Appendix 5 Renewal capital expenditure - Australian ...

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Table 3 – Circuit criticality ratings Circuit criticality Circuit criticality Renewal Capital Expenditure TNM-GR-809-0929 Issue 1.0, January 2009 Least critical Most critical 1 2 3 4 5 Number of circuits 7 6 5 11 24 53 Percentage of total 13% 11% 9% 21% 45% 100% Figure 5 presents a comparison of the criticality of the transmission circuits that contain Reyrolle 110 kV circuit breakers compared with the criticality of all transmission circuits. It shows that a large proportion of the transmission circuits that contain Reyrolle 110 kV circuit breakers tend to be critical, when compared to the entire transmission circuit population. Figure 5 – Reyrolle 110 kV circuit breaker comparison with the entire transmission circuit population 600 500 400 300 200 100 0 506 Low critcality 45 42 7 6 5 1.6 INVESTMENT DRIVERS 1 2 3 4 5 Criticality Index 144 High criticality Page 14 of 28 © Transend Networks Pty Ltd 194 UNCONTROLLED WHEN PRINTED 11 24 Overall Transmission Circuit s Reyrolle Type 110/ OS Circuit Breaker This section provides a summary of the key investment drivers for the key asset categories that comprise the selected 110 kV substation redevelopment projects that have been selected for review. It is important to note that the replacement of the Reyrolle 110 kV circuit breakers is only one component of the investment need and that the timing for each of the projects is driven by a range of asset management issues. A summary of the key assets that need to be replaced as part of the 110 kV substation redevelopments are presented in Appendix A1. Appendix A highlights the particular asset categories for each transmission circuit that have been identified as being in poor condition and need to be replaced. 1.6.1 Supply transformers The only 110 kV substation redevelopment project that includes the replacement of a supply transformer is the Arthurs Lake Substation redevelopment project. The Arthurs Lake Substation Condition Assessment Report (TNM-CA-809-0596) assesses the condition of the three singlephase transformers currently in service at Arthurs Lake Substation and also the identical singlephase system spare unit. The report has identified that the single-phase transformers: Total
Renewal Capital Expenditure TNM-GR-809-0929 Issue 1.0, January 2009 (a) are critical to ensuring a secure and reliable electricity supply to customers connected to Arthurs Lake Substation; (b) have inherent technical and design deficiencies that increase the transformers’ susceptibility to major failure if subjected to fault current or over-voltage conditions; (c) are in poor electrical and physical condition; and (d) have reached the end of their useful lives. The report recommends that the three single-phase units be replaced with a new three-phase unit. Following the decommissioning of transformer T1, disposal of the spare transformer located at Arthurs Lake Substation is also recommended. The transformers will be 65 years old when decommissioned. 1.6.2 Circuit breakers Transend has undertaken a comprehensive review of the condition of its Reyrolle 110 kV circuit breaker population. The review has identified that the Reyrolle 110 kV circuit breakers: (a) have a number of inherent technical and design deficiencies that have adversely impacted on transmission network reliability and availability; (b) are unreliable, in particular the air and insulating oil systems; (c) are maintenance intensive and costly to maintain when compared with modern equivalent units (preventive maintenance costs are approximately four times that of a modern equivalent circuit breaker); (d) require spare parts that are no longer available from the manufacturer’s agent; (e) require skilled personnel to maintain - the availability of skilled resources is declining due to an increased staff age profile and staff turnover; and (f) have reached the end of their useful service lives. Transend has determined the failure rates for its population of Reyrolle 110 kV circuit breakers based on their performance over the last 10 years. Transend has experienced 53 defects or failures over the last 10 years, of which four were considered major. The consequence of the defects and failures has varied from unplanned transmission circuit outages to undertake repairs to extended interruptions to electricity supply. 1.6.3 Instrument transformers The ongoing serviceability of instrument transformers (this category includes current transformers, capacitive and inductive voltage transformers) is impossible to predict with certainty. With certain types of instrument transformers, Transend’s experience is that maintenance does not have any material effect on preventing the occurrence of failures, in particular those that are explosive in nature. Moreover, routine condition monitoring does not always detect imminent failures. Even if it did, it is not practical, nor cost-effective to undertake the required condition monitoring activities at the frequency that would be necessary to pre-empt asset failure with any amount of certainty. Figure 6 presents an example of the voltage output profiles for two Ducon type PD 110 kV capacitive voltage transformers of the same type as those installed at Meadowbank and Palmerston substations. © Transend Networks Pty Ltd Page 15 of 28 UNCONTROLLED WHEN PRINTED
Page 1: APPENDIX 5 Transend, Renewal capita
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Page 14 and 15: Figure 4 - Overview of the Reyrolle
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Page 64 and 65: 6 BENEFITS The direct benefits of r
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7.2.3 DRAWBACKS The option has the
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Figure 2 - Option 3: single line di
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This option includes: � installin
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INVESTMENT EVALUATION SUMMARY 0BInv
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1 BACKGROUND 0BInvestment Evaluatio
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4.1 CIRCUIT BREAKERS 0BInvestment E
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0BInvestment Evaluation Summary TNM
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� reduced burden on spare parts m
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CONTENTS 0BInvestment Evaluation Su
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� replacement of the 110 kV Meado
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� reduced burden on spare parts m
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4.2 VOLTAGE TRANSFORMERS The 110 kV
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4.3 CURRENT TRANSFORMERS 0BInvestme
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The drawbacks for this option are t
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INVESTMENT EVALUATION SUMMARY 0BInv
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4.1.2 TUNGATINAH SUBSTATION 0BInves
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4.3.2 TUNGATINAH SUBSTATION The 110
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Tarraleah-New Norfolk No. 1 110 kV
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� the possibility of a 220 kV con
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Table 2 - Summary of Transend’s c
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3.2.2 110 KV BUS BAR PROTECTION SCH
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5. CUSTOMER CONSULTATION 0BInvestme
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Table 3 - Summary of NPV cost analy
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� loss of back-up protection func
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INVESTMENT EVALUATION SUMMARY TITLE
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INVESTMENT EVALUATION SUMMARY TITLE
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Burnie-Waratah 110 kV Transmission
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CONTENTS Burnie-Waratah 110 kV Tran
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1 BACKGROUND Burnie-Waratah 110 kV
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2.3 MAINTENANCE Burnie-Waratah 110
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Burnie-Waratah 110 kV Transmission
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