TransGrid has recently published a Project Assessment Conclusions Report for maintaining a reliable substation at Upper Tumut.
Established in 1959, Upper Tumut substation forms part of TransGrid’s southern NSW network. It connects approximately 616 MW of renewable hydro-electric energy generation, supports four transmission lines, and provides electricity flow paths between the Snowy Mountains, Canberra and Sydney.
Corrosion has been found on a large portion of the gantries at Upper Tumut substation. The corrosion of holding down bolts and structural components, or ‘members’, ranges from initial development through to loss of steel thickness (cross-sectional area).
Corrosion of holding down bolts is the key issue at this site and has been accelerated by the cracking of the concrete base plate plinths resulting from the repeated freezing and thawing of water inside cracks in the concrete.
If unaddressed, these issues may cause tower collapse; failure of steelwork, holding down bolts or baseplates; or failure of the whole substation.
TransGrid considered four credible options that would meet the identified need from a technological and project delivery perspective. Refurbishment of the holding down bolts and identified corroded steel members remains the most economical and preferred option at this stage of the RIT-T process.
No submissions were received in response to the PSCR during the consultation period which closed in June 2019.
No additional credible options that could deliver a material economic benefit were identified throughout the process and the outcomes of the economic analysis contained in the PSCR are maintained in this PACR.
The works for the preferred option are to be completed by 2020/21. The estimated capital cost of the proposed preferred option is $8.36 million ± 25%. TransGrid is the proponent of the proposed network project.
In accordance with the requirements of the Rules, a summary of the Project Assessment Conclusions Report is made available on the AEMO website. A copy of the Project Assessment Conclusions Report can be obtained from TransGrid’s website on the Regulatory Investment Tests page or by emailing RIT-TConsultations@TransGrid.com.au