TransGrid has recently published a Project Assessment Conclusions Report for maintaining compliance with performance standards applicable to Darlington Point substation secondary systems.
TransGrid has identified that the secondary systems at Darlington Point 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 As it is superseded by new technology at the manufacturer level and the existing technology becomes obsolete, spare parts become scarce and the ability of any primary asset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.
Darlington Point substation will continue to play a central role in the safe and reliable operation of the power system throughout and after the transition to a low-carbon electricity future. Located in the Riverina agricultural irrigation area inclusive of Leeton, the centre of the rice growing district in NSW, it forms part of the Southern New South Wales network which has been identified as an area of interest for new renewable connections. Darlington Point substation is a customer connection point supplying the Essential Energy 132 kV network in the Riverina region and is the starting point for the 220 kV network supplying Far West NSW and interconnects to Victoria at Red Cliffs.
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 Darlington Point substation must be addressed.
If the failure to provide functional secondary systems due to technology obsolescence, on the 220/330kV secondary systems components, 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. TransGrid has assessed that the 132kV secondary system assets do not warrant replacement within the same timeframe under this proposed project, and although benefits would be further derived from modernisation of monitoring and control systems it is considered non-prudent expenditure before 2022/23.
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 Darlington Point substation secondary systems in September 2020. In the PSCR TransGrid presented three credible network options that would meet the identified need from a technical, commercial, and project delivery perspective.
No submissions were received in response to the PSCR during the consultation period which closed in December 2020 and no additional credible options have been identified.
Since the time the PSCR was published, the cost estimate factors for Option 2 have been adjusted to reflect the latest estimated resourcing requirements to implement the preferred option. This resulted in an increase to the total cost estimate from $6.8m to $7.8m. TransGrid recalculated the NPV analysis for this PACR using the updated estimate for capital expenditure for Option 2 and the outcome had no impact on the ranking of the options.
Option 2 remains the preferred option at this stage of the RIT-T process. This option is estimated to have a capital cost of approximately $7.8 million ($6.3 million of this by 2022/23 for the 330kV and 220kV assets). Routine and operating maintenance costs are approximately $5,000 per year. TransGrid is the proponent of the proposed network project.
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