TransGrid has recently published a Project Assessment Draft Report (PADR) for maintaining compliance with performance standards applicable to Broken Hill substation secondary systems.
TransGrid has identified that the secondary systems at Broken Hill substation have reached a condition that reflects the end of serviceable life. As it is superseded by new technology at the manufacturer level and the existing technology becomes obsolete, spare parts become scarce and the ability of any primary asset connected to the substation to reliably operate will be at risk.
Broken Hill substation is a customer connection point supplying the Essential Energy networks in the area. It forms part of the wider South Western NSW network which supports renewable energy zone development and will continue to play a central role in supporting the flow of energy to the Far West region of NSW.
Provision of redundant protection schemes to ensure the transmission system is adequately protected is a Network Performance Requirement under Schedule 5.1 of the National Electricity Rules (NER), therefore the condition issues affecting the secondary systems at Broken Hill substation must be addressed. If the failure to provide functional secondary systems due to technology obsolescence is not addressed by a technically and commercially feasible credible option in sufficient time (by 2022/23), the likelihood of not recovering from secondary systems faults and not maintaining compliance with NER performance requirements will increase.
Continued deterioration of the secondary systems at Broken Hill substation will accelerate the depletion of spares which will lead to a situation where TransGrid is unable to operate the secondary systems in accordance with clause 4.6.1 of the NER. The proposed investment will enable TransGrid to continue to meet the standards for secondary systems availability set out in the NER, and to avoid the impacts of taking primary assets out of service. Consequently, it is considered a reliability corrective action under the RIT-T.
TransGrid published a Project Specification Consultation Report (PSCR) for maintaining compliance with performance standards applicable to Broken Hill substation secondary systems in December 2019. No submissions were received in response to the PSCR during the consultation period which closed in March 2020.
Since publication of the PSCR, TransGrid identified a need to re-scope one of the credible options (Option 4- Complete upgrade and renewal with 22 kV switchroom and 220 kV Secondary Systems Building), and identified one additional credible option (Option 5- Complete in-situ secondary systems and 22 kV AIS replacement). Consequently, as a result of this material change, TransGrid re-ran the NPV analysis including Options 1, 2 and 3, Option 4 (re-scoped) and the new Option 5.
In the NPV analysis, TransGrid used updated costs where applicable, as well as the latest inflation and discount rates.
The program of work to address the secondary systems at Broken Hill including complete replacement with 22 kV switchroom and 220 kV in-situ secondary systems (Option 4) is the preferred option presented in this PADR, both on the basis of net economic benefits, and being technically feasible. The other options put forward for consideration in the PSCR and the new Option 5 were estimated to have lower net economic benefits than the preferred option.
The estimated capital cost for Option 4 is approximately $18.34 million (-/+ 25%) in 2020/21 dollars. TransGrid is the proponent of the proposed network project.
In accordance with the requirements of the National Electricity Rules, a summary of the PADR is made available on the AEMO website. A copy of the Project Assessment Draft Report can be obtained from TransGrid’s website or by emailing RIT-TConsultations@TransGrid.com.au.
TransGrid welcomes written submissions on materials contained in this PADR. Submissions are due on 30 April 2021.