Regulatory Investment Test – Distribution – July 2025
The Eastern Cranbourne 66kV sub-transmission loop, supplying over 114,000 customers, is supplied by the Cranbourne Terminal Station (CBTS) and consists of seven zone substations—Lysterfield (LYD), Narre Warren (NRN), Pakenham (PHM), Officer (OFR), Berwick North (BWN), Lang Lang (LLG) and Clyde North (CLN). A new Pakenham South ZSS is expected to be commissioned by 2029. AusNet has identified increasing energy at risk in this network due to rapid demand growth in the South-East Growth Corridor. Forecasts indicate that maximum demand will exceed loop capacity by 2026 under summer 10% Probability of Exceedance (PoE) conditions and by 2028 under summer 50% PoE. The network's thermal constraints are expected to escalate, with demand reaching 332 MVA in 2026 and 390 MVA in 2027 under PoE10 conditions, exceeding the loop’s firm capacity (N-1) of 255 MVA, which was exceeded in 2023.
The Options Screening Report (OSR), which represents the first step in the RIT-D process in accordance with clause 5.17 of the National Electricity Rules (NER) and section 4.2 of the RIT-D Application Guidelines was published in February 2025. This report, the Draft Project Assessment Report (DPAR), is the second stage of the RIT-D process and provides information about the draft conclusions of the RIT-D.
One non-network proposal was received during the RIT-D OSR consultation phase.
The preferred solution is to install a new approx. 22km 66kV line of new 37/3.75 AAC line from Cranbourne Terminal Station to Officer zone substation. The estimated capital cost of the preferred option is $51.7 million (nominal).
AusNet welcomes written submissions on the credible options evaluation and draft conclusion presented in this DPAR. Submissions should be emailed to ritdconsultations@ausnetservices.com.au on or before 5th September 2025. In the subject field, please reference ‘RIT-D DPAR LD CBTS OFR’. AusNet’s preference is that these submissions would be published on its website and AEMO’s website. If you do not want your submission to be made public, please clearly stipulate this at the time of lodgement.
Assessments of the options and responses to this DPAR will be presented in the Final Project Assessment Report (FPAR), which AusNet expect to publish by November 2025.