Major network upgrade shores up Melbourne’s electricity supply

CitiPower and Powercor own and operate two of Australia’s largest electricity networks, supplying power to over 1.1 million Victorian households – including customers in Melbourne’s CBD and inner suburbs. Daly’s Constructions was recently involved in one of the most complex underground cable installation projects the Melbourne CBD has ever seen, working with CitiPower and Powercor to upgrade the city’s network as part of a major $250 million project involving Waratah Place Zone Substation.

A new joint bay being built around existing 66kV oil-filled cables (cut & capped) to connect onto new XLPE cables at Russell St. Waratah Place ZSS basement with newly installed cables

The Waratah Place Zone Substation project ensures that the network has a ‘double backup’ to withstand multiple outages and provide continuous supply to homes and businesses if unexpected events occur on major supply lines, such as extreme weather, fires, traffic accidents or infrastructure failures.

The rebuilt Waratah Place Zone Substation (WP ZSS) is the centrepiece of this project, which allows power to be diverted around the grid so the duration of a major power outage is limited to no more than 30 minutes.

Powercor Network Services, on behalf of CitiPower, engaged Daly’s Constructions to design and construct ten new 66kV underground cable circuits for the new WP ZSS.

These new circuits connect WP ZSS with five other substations in the CBD and nearby area, and ultimately serve to connect Waratah Place Substation to the three terminal stations that supply the Melbourne CBD: Richmond Terminal Station (RTS), Brunswick Terminal Station (BTS) and West Melbourne Terminal Station (WMTS).

This was achieved by diverting existing 66kV underground cables from various locations in the CBD to WP ZSS. New 66kV cables were jointed to existing cables at various locations along the busy Exhibition, Lonsdale, Russell and Little Bourke Streets, and at Waratah Place.

The scope of the works included: • Detailed design of the cable systems including civil, electrical, hydraulic (oil-filled cables) and temporary works • Installation of 10.5km of single core 66kV copper cables and 3.5km-long cable trenches through the

Melbourne CBD

• Relocation of existing services in Waratah Place (gas, water, power, sewer and telecom) to facilitate conduit installation while maintaining access for businesses • A 4m deep trench for the full width and 90m length of

Waratah Place with a retention system (consisting of bored piles provided by Powercor) to minimise structural risks to heritage-listed buildings with shallow foundations • Drilling from Lonsdale Street to Waratah Place and beneath the Little Bourke Street Chinese Monument including use of bespoke, purpose-built shoring systems • Construction of six new reinforced concrete joint bays up to 12m long by 3.2m wide including temporary works design. Three existing joint bays were re-excavated to connect new cables • Installation of 12 new cross-linked polyethylene (XLPE) to oil-filled transition joints connecting existing oil-filled cables (installed in the 1970s) with new XLPE insulated cables • Dismantling XLPE sides of the six existing transition joints (while keeping the oil side intact) and reconnecting them with new XLPE cables. This is a highly specialised task requiring extreme care and precision so as to not damage the sensitive components of the oil side of the joint. Due to the sensitivity of the task, special training was arranged for the jointers to simulate the dismantling process before on-site installation • Dismantling six existing XLPE joints and reconnecting them to new XLPE cables • Installation of 30 GIS (Gas Insulated Switchgear) terminations inside WP ZSS • Cutting and jointing into four existing oil-filled circuits, with the installation overseen by an overseas supervisor • Installation of new oil feeding tanks, associated accessories and testing. Unlike XLPE insulated cables, changes to oil-filled circuits require alterations to the oil feeding arrangements and pressure settings. Plant owned by Daly’s Constructions, such as an oil degasifying unit and other hydraulic testing equipment, were utilised for the works. A fluid systems engineer from the UK was brought over to supervise all hydraulic-related tasks • Completing all electrical and hydraulic pre-commissioning tests 4m deep trench at Waratah Place, retention system (bored piles) either side of the road, pedestrian and business access maintained between hoarding system and buildings.

WORKING COLLABORATIVELY TO KEEP THE POWER ON

The works commenced in 2016 where most of the civil works were completed on-site. Civil works were paused to cater for a major design change in the route to bring all cables in through the north and south side of Waratah Place instead of tunnelling from Russell Street.

Works recommenced in late 2018 with the relocation of utility services in Waratah Place. All civil works except for the joint bays were completed by the end of 2019.

Procurement of the 66kV joints and terminations was carefully coordinated to ensure compatibility as a variety of new and existing cable designs were used. There were seven different cable designs (four existing and three new) and as a result, eight different joint types were used.

Cable works began in March 2020 with a target completion of February 2021 to meet critical network operational timeframes. Nine circuits were initially planned to be commissioned before the 2020/21 summer.

This presented a major challenge to coordinate numerous resources and stakeholders to meet the tight schedule. Multiple crews were utilised for cable hauling, joint bay construction, jointing and terminating, oil-filled works and pre-commissioning activities.

The COVID-19 pandemic added a whole new complexity to an already challenging project, as Melbourne went through several lockdowns during this period.

While coordinating local resources, Daly’s Constructions managed to navigate through the pandemic with Melbournebased resources, as well as bringing in specialist overseas and interstate resources to complete the project.

The management of local and overseas staff during the height of the COVID-19 global pandemic required in-depth negotiations with the Department of Home Affairs and the Australian Border Force Commissioner.

By the end of October 2020, all ten circuits were completed four months ahead of schedule, marking a major milestone in delivering such a complex sub-transmission project.

According to Mark Daly, Director at Daly’s Constructions, “The success of the project delivery is due to the collaborative approach with the Powercor project team and other stakeholders, effective planning and Daly’s highly experienced and committed workforce.

“Weekly progress meetings and open communication ensured that all stakeholders were informed and that critical interfaces were well managed to deliver the successful outcomes.”

The Waratah Place Zone Substation upgrade was recognised as a Victorian Project Winner at the Australian Institute of Project Management’s 2020 Project Management Achievement Awards, which exist to acknowledge, honour and promote outstanding achievements in program and project leadership.

For more information, contact Daly’s Constructions on 03 9360 9485 or visit www.daly.net.au.

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