TransGrid has recently published a Project Assessment Conclusions Report (PACR) for maintaining compliance with performance standards applicable to Wagga 330 kV substation secondary systems.
The secondary systems at Wagga 330 kV 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 As it is superseded by new technology at the manufacturer level and the existing technology becomes obsolete, spare parts become scarce and the ability of the any primary asset connected to the substation to reliably operate will be at risk.
Located in the Riverina region of southern NSW, Wagga 330 kV substation forms part of the wider south-western NSW network which also 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 NSW1.
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 Wagga 330 kV 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 Wagga 330 kV 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 Wagga 330 kV substation secondary systems in June 2019. No submissions were received in response to the PSCR during the consultation period which closed in September 2019.
TransGrid considered four credible options that would meet the identified need from a technological and project delivery perspective.
Since the PSCR, TransGrid has:
- updated the discount rates used
- updated the inflation escalation
- removed unserved energy from the NPV analysis
None of these elements has made a material impact on the outcome.
Option 1 — complete in-situ replacement of all secondary systems assets at Wagga 330 kV substation— remains the preferred option.
The works for the preferred option are to be completed by 2021/22. The estimated capital cost of the proposed preferred option is $8.6 million +/- 25%. TransGrid is the proponent of the proposed network project.