TasNetworks has published the Project Assessment Conclusion Report (PACR) for Managing safe and reliable operation of Chapel Street Substation. Publication of this PACR represents the final step in the Regulatory Test for Transmission (RIT-T) process.
Chapel Street Substation is located in Hobart. Reflecting its location, Chapel Street is a critical substation in the network because it supplies electricity to approximately 12,772 customers across southern Tasmania and northern Hobart. In addition, Chapel Street Substation serves the Hydro Tasmania owned 450 MW Gordon-Pedder hydroelectric power generation system.
Chapel Street Substation currently operates with 11kV metal-clad switchgear with fixed type circuit breakers that were installed in 1983. Switchgear is critical to the reliable supply of electricity because it is used to collect and distribute electricity from feeder lines for transportation throughout the transmission and distribution networks.
TasNetworks has identified that the switchgear at Chapel Street Substation is approaching its end of life based on regular asset inspections and condition assessment. The switchgear is not designed for internal arc containment and in the event of an arc fault, the release of electrical energy can cause metal projectiles to be discharged from the switchgear along with heat and other byproducts. This can lead to harm to workers, surrounding equipment and cascading asset failures. As a result, TasNetworks’ extra high voltage (EHV) operators must wear special arc flash rated (Cat 4) personal protective equipment (PPE) suits to operate the switchgear. Whilst effective, it is the lowest form of risk and hazard control and the need to wear Cat 4 PPE is cumbersome and time consuming, increasing the time required to conduct maintenance tasks.
In addition, the existing switchgear has long been obsolete, leading to a growing scarcity of spare parts. The spare parts that TasNetworks maintained have been used in the existing switchgear and there are no more spare parts available. While TasNetworks maintains operational spares within the existing switchgear, using these spares for reactive replacement requires additional time, leading to longer outages.
Addressing the condition issues of the switchgear will enable us to manage reliability, financial, and safety risks at Chapel Street Substation. TasNetworks expects that addressing these issues will result in significant market benefits and, as such, we consider the identified need for this investment to be market benefits under the RIT-T.
We consider that there are two credible options from a technical, commercial and project delivery perspective that can be implemented in sufficient time to meet the identified need. This PACR has found that Option 1 is the preferred option at this stage of the RIT-T (consistent with the draft conclusion in the earlier PSCR).
Option 1 involves the replacement of the HV switchgear in the 2024-29 regulatory control period (and in particular by financial year 2025/26 latest by beginning of 2026/27).
The estimated capital expenditure associated with Option 1 is $6.19 million (in 2023/24 dollars).
The works are estimated to take place across financial years 2024/25 and 2025/26, with practical completion and commissioning by the beginning of financial year 2026/27.
A copy of the PACR can be obtained from either the TasNetworks website or by emailing our regulation team via regulation@tasnetworks.com.au. Parties wishing to raise a dispute notice with the AER may do so prior to 16th December 2024.
In accordance with the requirements of the Rules, a summary of this PACR has been made available on the AEMO website.