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

7.3 OPTION 3 - STAGED REPLACEMENT OF SELECTED ASSETS IN-SITU
7.3.1 SCOPE
0BInvestment Evaluation Summary
TNM-GS-809-0720
The scope for this option is essentially the same as Option 2, but implemented using a staged approach based on
transmission circuit criticality. This option includes:
� initial replacement of the following assets:
@ Sprecher and Schuh Type HPF 110 kV circuit breakers and associated assets (three bays);
@ other assets that have an assigned transmission circuit criticality rating of four or five (five bays); and
@ other assets that present a safety risk, including selected 110 kV current transformers (two three-phase sets); and
� defer replacement of remaining 110 kV assets by up to three years (two bays).
The capital cost of this option includes an initial $5.88 million ($June 2007) to replace critical assets and to address
safety issues followed by a deferred capital cost of $0.85 million ($June 2007) to replace remaining 110 kV assets three
years later.
7.3.2 BENEFITS
The benefits for this option are that it:
� allows Transend to achieve the capital expenditure objectives in the mid-term;
� addresses the safety issues associated with the 110 kV assets identified in section 4 of this document, in particular
the 110 kV current transformers;
� defers capital expenditure associated with lower criticality assets for up to 3 years;
� addresses the performance issues identified in section 4 of this document, with the exception of those transmission
circuits that have a criticality less than four; and
� reduces the ongoing maintenance requirements and costs associated with the site.
7.3.3 DRAWBACKS
The drawbacks for this option are that it:
� results in a higher initial capital cost than option 1;
� results in a higher overall capital cost than option 2, primarily due to contractor remobilisation and increased internal
costs;
� does not align with Transend’s policy to utilise dead tank circuit breakers when replacing 110 kV live tank current
transformers and circuit breakers for two 110 kV bays;
� reduced efficiencies in project delivery, in particular co-ordination of works associated with the Avoca Substation
transformer T2 installation project and asset replacement works; and
� will need additional transmission circuit outages to undertake the works.
7.3.4 CONCLUSION
This option is technically viable.
7.4 OPTION 4 - REPLACE SELECTED ASSETS IN NEW SWITCH BAYS
7.4.1 SCOPE
The scope for this option includes:
� replacement of the existing live tank circuit breakers with dead tank units that have integral current transformers.
The implementation methodology for this option includes constructing new transmission circuit bays and relocating
existing bays sequentially to new bays in order to minimise outage durations. It involves the following key stages:
- developing two new switchgear bays and one new bus-coupler bay;
- restringing the last span of the five transmission circuits into the adjacent bays; and
- extending the 110 kV bus bars to facilitate the installation of the bus coupler.
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