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

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Figure 6 – Capacitive voltage transformer output voltage profiles Renewal Capital Expenditure TNM-GR-809-0929 Issue 1.0, January 2009 The output voltage for asset 03001001 can be seen to increase dramatically within a very short period of time (within hours). This capacitive voltage transformer failed explosively, even though the condition monitoring results for this capacitive voltage transformer were satisfactory when it was last maintained. This event clearly illustrates that the risk of catastrophic failure is real and the rapid rate of deterioration that leads to explosive failure. It also highlights the negligible impact that maintenance activities have on preventing such failures, even with minimal time intervals between maintenance activities. The likelihood of instrument transformer failure increases significantly as the condition of the asset deteriorates as a consequence of ageing. Transend notes Nuttall Consulting’s view that ‘The safety risks associated with the explosive failure of post type insulators and voltage transformers have been known for some time (ie circa 2000 5 )’. In 1998, when Transend was established, it inherited a transmission system that had received minimal renewal investment in the preceding years. At that time it was well recognised that the transmission system required substantial investment to address the vast range of asset management issues presented by the asset base at that time. For this reason, Transend established long-term asset renewal programs that prioritised the targeted replacement of known ‘high risk’ assets. This approach is evidenced by the replacement of the 110 kV voltage transformers at Creek Road Substation, which, together with other targeted works, has allowed the redevelopment of the substation to be deferred by more than ten years. It should be noted that the voltage transformer and post insulator replacement programs commenced in 1999 and that Transend has replaced a large number of high risk assets in the current regulatory control period that are susceptible to explosive failure, and plans to continue to do so over the forthcoming regulatory control period. However, given the magnitude of investment required to address the identified issues and the issues associated with accessing the transmission system to undertake the required works, it is impractical to mitigate all of the risks in the short term. Effectively managing and prioritising the implementation of a complex, integrated works program has presented a considerable challenge, and will continue to do so over the forthcoming regulatory control period. Transend’s asset management policy requires that its assets be proactively managed such that they are operated safely and within prescribed technical limits. 5 Nuttall Consulting, Review of Transend Revenue Proposal Asset Renewal Capital Expenditure, November 2008 p61 Page 16 of 28 © Transend Networks Pty Ltd UNCONTROLLED WHEN PRINTED
Renewal Capital Expenditure TNM-GR-809-0929 Issue 1.0, January 2009 For these reasons Transend considers it vitally important that instrument transformers that are known to be in poor condition and are susceptible to failure be replaced at the appropriate time. In addition to mitigating a serious safety risk, the replacement of instrument transformers of obsolete technology significantly reduces the need for maintenance, thereby having a positive impact on maintenance costs and increasing transmission circuit availability. Transend has identified that it is more cost-effective over the asset life-cycle to install dead-tank circuit breakers that have integral current transformers, rather than live tank circuit breakers and post-type current transformers at 110 kV. For this reason, given the condition of the Reyrolle 110 kV circuit breakers that are associated with the current transformers included in the 110 kV substation redevelopment projects, it is prudent and efficient to install dead-tank circuit breakers that incorporate current transformers rather than replace the current transformers and circuit breaker separately. Transend’s practice is to install capacitive voltage transformers (this design allows the secondary voltages to be continuously monitored) that have composite insulation and pressure relief devices incorporated into the design at 110 kV. This approach mitigates the safety risks presented by voltage transformers and reduces the maintenance need. Transend’s comprehensive strategy for the management of instrument transformers over the asset life-cycle provides significant benefits in terms of addressing significant safety and reliability issues as well as providing optimum transmission circuit availability at a low cost. The 110 kV substation redevelopment projects include the replacement of the instrument transformer makes and types as presented in Tables 4 and 5. Of the instrument transformers identified for replacement, 60 percent will have exceeded their nominal service life of 45 years when decommissioned. The remaining units will be assessed for their suitability for re-installation elsewhere in the transmission network. Whilst age is not the sole factor for determining the need to replace instrument transformers, it provides a key indication of when the condition of the asset will have deteriorated to the extent that the likelihood of failure is increased. Table 4 – Replacement of current transformer makes and types Current transformer make / type Number of units Average age (years) Asea IMBA120 21 49 Asea Brown Boveri 236080 Asea Brown Boveri 236080 Laur Knudsen 60 47 © Transend Networks Pty Ltd Page 17 of 28 UNCONTROLLED WHEN PRINTED Comment 3 23 The condition of these units will be assessed and if deemed serviceable, they will be installed elsewhere in the transmission network. 57 13 These units were installed because of the need to replace units contaminated with polychlorinated biphenyl (PCB). The condition of these units will be assessed and if deemed serviceable, they will be installed elsewhere in the transmission network. Endurance Electric HS 6 39 These units will be retained as spares. Endurance Electric IC 115 3 48 Endurance Electric OD 6 39 These units will be retained as spares.
Page 1: APPENDIX 5 Transend, Renewal capita
Page 4 and 5: Renewal Capital Expenditure TNM-GR-
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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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CONTENTS 0BInvestment Evaluation Su
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� replacement of the 110 kV Meado
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4.2 VOLTAGE TRANSFORMERS The 110 kV
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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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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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