Transgrid has recently published a Project Assessment Conclusions Report (PACR) for maintaining compliance 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 As it is superseded by new technology at the manufacturer level and the existing technology becomes obsolete, spare parts become scarce and the ability of any primary asset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 220/22kV substation is a customer connection point supplying the Essential Energy networks in the area. Silverton Wind Farm also connects at Broken Hill substation, as well as Broken Hill Solar Plant. 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.
The Network Performance Requirements, set out in Schedule 5.1 of the NER, place an obligation on Transmission Network Service Providers (TNSPs) to provide redundant protection schemes to ensure the transmission system is adequately protected. Schedule 5.1.9(c) of the NER requires a TNSP to provide sufficient primary and back-up protection systems, including any communications facilities and breaker fail protection systems, to ensure that a fault of any type anywhere on its transmission system is automatically disconnected.
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 Assessment Draft Report (PADR) on 16 March 2021. Transgrid invited written submissions on the materials contained within the PADR and received one submission which highlighted some opportunities to improve the clarity of this PACR, specifically regarding the efficiencies provided by the timing of the works and clearer cost comparison of all credible options to better demonstrate that Option 4 (preferred option) is the most efficient and prudent way forward.
No additional credible options were identified during the consultation period following publication of the PADR. The following changes have occurred since the PADR which have not made an impact on the preferred option:
- updated the substation primary equipment investment cost in the base case and Options 1, 2, 3 and 5 to include remediating fault level limitations on the busbar to allow comparable assessment with Option 4,
- updated operations and maintenance costs,
- updated phasing of risk cost benefits to align with the timing of substation primary equipment investment; and
- removed unserved energy benefits from the NPV analysis.
The implementation of Option 4, a complete replacement with 22 kV switchroom and 220 kV in-situ secondary systems remains the most efficient technically and commercially feasible option to continue meeting NER requirements at this final stage of the RIT-T process.
The estimated capital cost of this option is approximately $18.3 million. Routine operating and maintenance costs are approximately $23,000 per year.
The works will be undertaken between 2020/21 and 2022/23. Planning (including commencement of the RIT T) commenced in 2019/20 and is due to conclude in 2020/21.The detailed design will commence in 2021/22 with procurement and delivery of the identified assets planned to occur during 2021/22. All works will be completed by 2022/23. Necessary outages of relevant existing assets will be planned appropriately in order to complete the works with minimal impact on the network.
In accordance with the requirements of the National Electricity Rules, a summary of the PACR is made available on the AEMO website. A copy of the PACR can be obtained from Transgrid’s website or by emailing RIT-TConsultations@Transgrid.com.au.