The new 2 x 5MW rectifier 66kV substation will support the 1,500V traction power supply in the area and is required to run the new fleet on the Central Coast and Newcastle rail line.
The works form part of TfNSW’s larger Power Supply Upgrade Program which involves construction of new electrical infrastructure and upgrades to substations, sectioning huts, overhead wiring and feeders across the Sydney Trains network - all required to meet expected power requirements of the future rail network.
This project at Gosford was by no means straightforward - the location, the site conditions, the surrounding environment, the local community, and proximity to the rail corridor and road infrastructure all meant the project had many challenges!
The small substation site is sandwiched between the railway corridor with its live overhead power lines and trains, Fagans Bay, part of Brisbane Water National Park, and ecologically significant mangroves. The Brian McGowan Bridge flies over another side of the site, ferrying a constant stream of traffic on the Central Coast Highway.
The ground, which is located only metres from the water’s edge, is sandy and unstable. A careful process involving extensive testing and sampling was needed to determine a suitable depth for the footings for the substation. Ultimately, forty piles drilled to a depth of up to eight metres were required.
The tight space proved challenging when using cranes to lift and manoeuvre the precast concrete walls, GIS (gas insulated switchgear) and other high voltage electrical equipment into place.
In-service railway lines
Working alongside the active rail line, with both up and down running mains and three active sidings, brought its challenges.
A large part of the project involved two underline crossings for the installation of conduits under the railway lines and the adjacent sidings. The works were conducted under stringent permit conditions and were a complex logistical exercise.
An underline crossing involved removing the rail lines and sleepers and installing concrete encased conduits to a depth of 3.2 metres.
The ground under the sidings was found to be "peppered with services", including communications, power, low voltage, water and signalling assets. It was extremely slow going and tough working at a depth of three metres. Not only were crews working carefully underground, but they had to be careful of the de-energised 1500v DC overhead line.
This project for TfNSW was the catalyst for Zinfra to attain Authorised Engineering Organisation (AEO) status with the transport agency.
On 1 August 2016, Zinfra was officially awarded AEO status.
Having the status of being an AEO enables Zinfra to produce and undertake engineering solutions for TfNSW with a significantly streamlined assurance process – saving time and resources to allow Zinfra to deliver more autonomously and efficiently.