TransGrid has recently published a Project Assessment Draft Report for maintaining reliable supply to Broken Hill.
Part of TransGrid’s south western transmission network, Broken Hill is currently supplied by a single 220 kV transmission line, ‘Line X2’, from Buronga.
When Line X2 is out of service due to a planned or unplanned outage, electricity supply to Broken Hill is supported by two gas turbines owned by Essential Energy to avoid involuntary load shedding (these turbines each have a nameplate rating of 25 MW). TransGrid relies on these gas turbines to meet the NSW Electricity Transmission Reliability and Performance Standards 2017 set by the NSW Energy Minister and regulated by the NSW Independent Pricing and Regulatory Tribunal. In accordance with these standards, Essential Energy’s gas turbines allow TransGrid to operate its network so as not to expect more than 10 minutes of unserved energy (EUE) per year at average demand.
Essential Energy notified TransGrid of its decision to divest the gas turbines located at Broken Hill. If no action is taken by TransGrid, this will result in the required reliability of supply to Broken Hill not being maintained, and involuntary load shedding when Line X2 is on planned or unplanned outage.
TransGrid considers this a ‘reliability corrective action’ under the RIT-T as the identified need is to ensure that the externally-imposed reliability standards for Broken Hill continue to be met.
TransGrid’s revenue determination for the 2018-2023 regulatory control period includes a contingent project for the reliability of supply to Broken Hill. This contingent project is to provide additional capacity to supply Broken Hill in an event that the total 220 kV and 22 kV load at Broken Hill exceeds the capacity of the back-up gas turbines owned by Essential Energy and EUE exceeds the allowance.
In order to efficiently avoid involuntary load shedding and meet the reliability standards TransGrid adopted a two-step approach.
Step 1 – Establish a short-term non-network support solution, via an Expression of Interest (EOI) process. This short-term non-network support solution will be required to be available:
- immediately; and
- until the long-term solution, which will be identified under this RIT-T process, is operational.
Step 2 – Establish a long-term solution via the RIT-T process. It may take up to three years for this long-term solution to be operational.
In November 2019, TransGrid issued an EOI for technology solutions to be considered as options in the RIT-T and also published the Project Specification Consultation Report (PSCR). The PSCR detailed the need to maintain reliable supply to Broken Hill and describes credible options to meet the need, including technical characteristics of a non-network option. Submissions to the PSCR and responses to the EOI closed on 31 January 2020 and were considered in the assessment of options in the PADR.
Stakeholder consultation on the PSCR has assisted greatly with developing and refining the credible options put forward in the PSCR. Specifically, consultation with third parties since the PSCR has enabled this PADR to assess the following five types of credible options:
TransGrid has put forward five types of credible options for consideration in this Project Assessment Draft Report:
- Option 1: four different non-network opex solutions fully provided by third parties (Option 1A, Option 1B, Option 1C and Option 1D);
- Option 2: a refined version, and cost for, acquiring the existing gas turbines from Essential Energy;
- Option 3: establishing new gas turbines at Broken Hill;
- Option 4: building a second single circuit 220 kV transmission line from Buronga to Broken Hill; and
- Option 5: three variants of the first group of solutions involving either shared ownership or ownership by TransGrid (Option 5A, Option 5B and Option 5C).
TransGrid welcomes written submissions on materials contained in the PADR are particularly sought on the credible options presented and from potential proponents of non-network options that could meet the technical requirements set out in the PADR. Submissions are due on 22 September 2020.
In accordance with the requirements of the Rules, a summary of the Project Assessment Draft Report is made available on the AEMO website. A copy of the PADR can be obtained from TransGrid’s website or by emailing regulatory.consultation@transgrid.com.au.