Double-decker substation to prepare for Melbourne Metro

In order to maximise space and prepare for High Capacity Metro Trains, a custom-designed, multi-storey substation has been installed in Melbourne’s CBD.

In the heart of Melbourne’s Central Business District, a team of engineers and construction workers installed Victoria’s first ever modular traction substation to boast a ‘double-decker’ design.

The substation was custom-designed to squeeze onto a narrow strip of land near the major transport hub of Southern Cross Station.

Along with several others along the Cranbourne/Pakenham line, the Southern Cross ‘subbie’ forms part of a major upgrade being carried out in preparation for bigger High Capacity Metro Trains.

Multi-storey substations are rare in Australia. This structure was built off-site using prefab technology.

Two separate modules, each more than 25m long, were delivered to site all the way from South Australia, with one lifted on top of the other in a complex twelve hour operation.

The double-decker design aims to maximise space and help transport infrastructure keep up with Melbourne’s burgeoning population.

Rail substations take electricity from the existing power network and convert it into a form that can be fed through to trains.

Due to its location, the Southern Cross facility is electrically larger than most, containing around twelve kilometers’ worth of cabling compared to the average of eight or nine.

Humble from the outside, modern substations are built to high-spec standards, incorporating fail-safe mechanisms and vital communications connections to allow them to ‘talk to’ network control centres. Substations are also weather and fire proof.

Prefabrication to save time

Contractors were able to design and build the structure within a relatively short timeframe.

Power Manager, Evan Broughton, said the use of prefab technology meant the substation could be built off site at the same time as the foundations, saving time and eliminating the potential for weather delays.

“We were originally looking at constructing a traditional building in this locale, but the tight timeframe meant that the modular building method was the way to go,” Mr Broughton said.

“This substation was custom-designed for the footprint, to make optimal use of the space while allowing room for an access road.”

Mr Broughton said while he had seen a lot of prefabrication in construction throughout his career, a multistorey substation in the inner city takes it to a new level.

“Rail environments pose unique challenges and we need to monitor the movement of people, machinery and construction with absolute precision,” he said.

Dean Chaplin, a project manager for LAI Switchboards, one of Australia’s leading switchroom and substation providers, said the superstructure was essentially 100 per cent completed on arrival to site in Victoria and had to be centimetre-perfect.

LAI has delivered a series of new substations along the Cranbourne/Pakenham line and rates the Southern Cross job as their most complex, but also among the most efficient construction projects.

“The team effort was phenomenal. Every piece of communication had to be on point, and every action had to be quick,” Mr Chaplin said.

Construction snapshot

• Pre-fab substation module makes a 2.5-day journey from South Australia to Melbourne on the back of a 16 axel expandable platform trailer, measuring 31m long
• Trailer enters site and positions itself over crushed-rock foundation
• Foundation legs drilled and chem set in place
• Trailer removed in sections from underneath the buildings (as there wasn’t room to remove it all in one piece)
• Second module is delivered to site and subsequently lifted in place