The substation consists of two 110kV/11kV dual LV winding transformers, which feed four 11kV buses. The project involved installing and conducting works to replace the four existing 11kV switchboards with new ABB switchgear. The works included structural modifications to the site itself, cable jointing/termination, electrical installation works, primary and secondary testing and commissioning.
After a competitive tender process, TasNetworks engaged Zinfra to carry out the works. Zinfra is a leading service provider which offers a range of engineering, project management, construction, operations and maintenance services to power and gas asset owners and other clients in the renewables, transport and resource sectors.
Through strong collaboration, Zinfra and TasNetworks were able to navigate challenges and deliver the upgrades on time and within budget.
Building relationships before the project
TasNetworks intended to replace existing oil filled switchgear with new air insulated switchgear with vacuum type Circuit Breakers at its North Hobart substation. With two transformers that have dual LV windings on site, there were 24 feeders in total for four buses which needed to be replaced as they had reached end of life.
After a tender process in August 2021, Zinfra was awarded the tender to help deliver the upgrade.
Project Manager at Zinfra, Andrew Hadley, said Zinfra was awarded the contract because of its already established relationship with TasNetworks through previous projects and works.
"Zinfra has got a lot of experience working with TasNetworks in the state, being one of their primary subcontractors for this type of work," Mr Hadley said.
But even before winning the contract, the Zinfra team were already engaging and consulting with TasNetworks to ensure the project design was as effective and efficient as possible.
"We do work closely with them in that pre-tender phase as well," Mr Hadley said.
"Even through the design phase, TasNetworks and their project managers would phone our team and bounce off some technical questions or ways of doing things to try and help develop that design."
With already established relationships, Zinfra and TasNetworks were able to collaborate more closely and share information.
"It's a small pool of subcontractors who do this work. We're all pretty comfortable bouncing ideas off each other and sharing information that helps them get the projects across the line," Mr Hadley said.
Approaching a complex project
Zinfra was responsible for providing timely and reliable works within the restrictions imposed by the type of the work.
The works commenced in October 2021 and were completed on time and within budget in April 2022.
The North Hobart substation is one of the main substations in the area, meaning it was important that works were completed to the deadline to prevent additional disruptions and outages.
"There's a lot of important customers connected through this substation. The planning phase of this had been going on for 12 months before works commenced," Mr Hadley said.
Construction Manager at Zinfra, Braydon Pace, said one of the challenges for the project was the procurement of materials in time for the start of the project.
"We did need to order some equipment from the mainland to deliver the project, and we managed this by getting our suppliers to deliver everything in stages.
"This ensures our suppliers aren’t overwhelmed, and keeps everything running smoothly."
Given the complexity of the project, the team encountered a variety of challenges, the largest concern being risk management. Working on a live electrical site requires significant planning and safety precautions to ensure workers are safe when conducting the upgrades and installations.
Mr Pace said managing how to work next to or on live equipment is always the most challenging part.
"There's a lot of risk assessments involved with doing the job safely and being able to do it on time," Mr Pace said.
"There were hold points throughout the project to prove that we could do it safely and keep the system going at all times, or as much of the system going as possible at all times."
The location of the substation also posed restrictions on the works.
"Being in the main part of North Hobart, it's a very tight constrained site, with difficult access off the main arterial road," Mr Hadley said.
"It was all really tight in there, but in the basement area, there were 36 new incomer cables and an array of existing feeder cables.
"The team did a really good job to be able to visualise how we needed to transform that from the start."
Managing safety before and during construction
Zinfra knew safety measures had to be thoroughly planned beforehand and maintained throughout the project to ensure works could be completed to the deadline.
"From the outset, we worked with the client to do a risk workshop and identify risks early in the piece," Mr Pace said.
Mr Hadley said that it's important to begin safety discussions prior to undertaking the work to ensure everyone is on the same page.
"We try to do all that at the start of the project or just before so the field guys, TasNetworks, our internal HSE business partners and all those involved have a good knowledge base to be able to develop risk registers," Mr Hadley said.
Zinfra was undertaking their own ISO accreditation audit at the time of this project, and it just so happened this project would be one of the projects reviewed as part of this audit.
"The external audit proved our readiness," Mr Pace said. "It was quite a major audit for us, that doesn’t happen often, so we had plenty of good feedback from that."
Utilising local expertise
By using local crews for the project, Zinfra were able to draw on local expertise and experience to provide effective works.
The construction crew used on site were all Hobart-based, with some support from Zinfra’s northern crew.
While using local crews offers financial benefits, they most importantly offer valuable expertise from having worked on Tasmanian electrical infrastructure, which may not be the case for mainland crews.
"Every state has got their own different systems and guidelines to go by, so it's nice to know you're using subcontractors that have built these things in the state for TasNetworks before and they know the expectations of the clients," Mr Pace said.
By drawing upon local knowledge and expertise, existing relationships and world-class safety practices, Zinfra and TasNetworks ensured that collaboration was the defining feature of this successful project.