Syncline Community Cable (SCC) is a proposed 525 kilovolt (kV) High-voltage Direct Current (HVDC) underground transmission line that will connect into the Melbourne Renewable Energy Hub (MREH) switchyard and into the northern part of VNI West at Jeffcott, near Charlton. It is being developed by Syncline Energy, a leading Australian owned and Melbourne based transmission and energy developer.

Transmission lines play a critical role in Australia’s energy supply by moving electricity from where it is generated, to where it is used. They also connect different states so they can efficiently share energy resources.

Approximately 100km of the underground line will be in the median strip of the Calder Freeway from MREH to Ravenswood, just south of Bendigo. Co-location in the median strip can be done safely and without limiting future road widening or plans for new interchanges. Using the freeway corridor allows SCC to deliver electricity to Melbourne from NSW and the State’s north-west without affecting urban areas or the rich cultural heritage and ecological values found throughout the Macedon Ranges.

From Ravenswood, for approximately 165km, the underground line crosses flat, cropping and grazing farm country to Jeffcot.

The fully underground transmission line will be supported by two converter stations, one at MREH and one at Jeffcot, and a cable-cable intermediate transition station in the median strip of the Calder Freeway near Ravenswood.

The trench design involves three cables in conduit. The depth and width of the trench will depend on the constraints of the land type.

In tight sections of the Calder Freeway median, a deeper, narrower trench will be used with a depth of up to 2.2 m and a width of up to 1.5 m.

Through agricultural land and unrestricted sections of the Calder Freeway median, a shallower, wider trench will be used with a depth of up to 2m and a width of up to 1.8m.

Topsoil will be replaced in the upper 400mm of the trench, allowing most farming activities to continue within the easement after construction.

Refer below to typical cross sections of cable placement within the trench.

Sections of the route with river and road crossings, as well as areas with high ecological and cultural value, will use Horizontal Directional Drilling (HDD) at depths of 8 to 16m. This avoids surface disturbance to flora and fauna and waterways during construction.

Where it is possible, the undergrounding of transmission lines has several advantages, including:

• Greater community support – putting transmission underground removes visual impacts and offers less disruption to agriculture.

• More reliable transmission – by reducing the risk of outage due to extreme weather events, and in particular high winds. In recent years, these have been known to topple overhead transmission towers in Victoria.

• Less fire risk – less opportunity to start a fire, and less affected by bushfires should they occur in the vicinity of the underground line.

• Greater ability to avoid valued areas – underground cables can manoeuvre around valuable areas (biodiversity, cultural heritage, dwellings etc.) to a greater degree than overhead lines and therefore, can avoid impacts. They can also be constructed using HDD, a form of tunnelling which avoids any surface disturbance.

The electricity grid needs to be expanded to support economic growth in Victoria, while also being reconfigured for the staged exit of coal-fired power stations that are reaching the end of their economic life. Syncline Community Cable is sized to transmit more than one quarter of Victoria’s electricity and will be key to the State’s energy supply for many decades to come.

Syncline Community Cable is an up to 2GW HVDC underground electricity transmission link that has been specifically designed to:

• Reinforce Victoria’s electricity network at the lowest possible cost to consumers when compared to the longer overhead 500kV HVAC alternatives

• Increase interconnector flows with New South Wales (NSW) by 25% (+2.3 GW)

• Increase Victoria’s renewable energy hosting capacity by 25% (+3.1GW)

• Support the priority Renewable Energy Zone (REZ) areas identified by VicGrid in its September 2024 Victorian Transmission Plan Guidelines.

The Syncline team assessed different cable configurations and voltages to identify the most reliable engineering design. We used historic performance data for cables in operation globally across different technology types, going back decades.

Syncline’s design voltage, of 525kV, has historically had a relatively low failure rate of 3.5% across the life of the Project (see chart below). This compares favourably to the overhead HVAC transmission alternative if ‘energy unavailability’ was calculated using a similar historic data set and including different voltages and conductor materials.

Compared to the historic data, HVDC technology has improved dramatically, and in particular the ability to monitor the cable route. This allows faults to be located and remedied before there is a worse failure. Syncline’s design will include this advanced monitoring and fault detection approach which should improve it's failure rate.

Improved network resilience

There is a need to make Victoria's transmission system more resilient to high impact low probability (HILP) events. A single storm in February 2024 resulted in the collapse of six high voltage over-head transmission towers near Anakie. That one event cost Victorian households and businesses more than $770 million.

Syncline's underground design is significantly more robust and the selected route is independent of the existing transmission corridors. The Project will significantly reduce the risk of HILP events (e.g. storms, fires) for Victoria's transmission system.

In addition to the reliability and resilience benefits, there will also be a cost saving for electricity consumers, from avoiding the costs otherwise needed in the next 20-years to make the State’s legacy overhead transmission more resilient.

60% lower energy losses

Our grid assessment has shown that Syncline's design, using HVDC technology operating at 525 kV, results in transmission losses that are up to 60% lower than the overhead HVAC transmission alternative. The Syncline Community Cable offers a more efficient, fully controllable and sustainable solution in terms of operational energy loss reductions.

Syncline Energy was founded in 2005. It has originated more than $5 billion of energy transition infrastructure assets, of which $1.7 billon is either under construction or in operation.

Syncline Energy has a track record of delivering critical energy infrastructure, including the Melbourne Renewable Energy Hub (MREH), one of the largest energy storage facilities in the world, financed by Equis, and delivered in partnership with the State Electricity Commission. MREH is currently under construction in Plumpton and is scheduled to be completed by June 2025.

The company has also delivered Bannerton Solar Park, a Victorian solar farm powering Melbourne’s tram network.

Syncline Energy is owned by Phil Galloway, who has an extensive history in project development, engineering and finance. This includes global executive roles at BHP for 10-years, engineering roles with Rio Tinto, banking roles at Credit Suisse First Boston in the electricity sector and energy market analyst roles at Esso.

The planning and engagement for the project is being led by Cogency Australia, along with a team of technical subconsultants.

High-Voltage Direct Current (HVDC) is a type of electricity transmission which differs from the more common type of electricity transmission of alternating current (AC).

HVDC transmission is commonly used for long-distance point-to-point connections, as it loses a lot less energy during the transmission process and can transmit more energy per installed cable. HVDC transmission requires costly ‘converter stations’ to connect to the existing grid, which makes it a point-to-point solution with no economic way to add solar and wind farms (for example) along the HVDC route.

HVDC transmission can more easily be put underground compared to AC connections, which is why the Syncline Community Cable selected this technology having assessed the cost/benefits of alternatives. Syncline Community Cable is not the first time HVDC technology has been used in Australia. Other examples include the undersea Basslink connection from Victoria to Tasmania and the underground Murraylink from Mildura to Red Cliffs in Victoria. The Victorian section of the proposed Marinus Link cable connecting Tasmania and Victoria is also proposed to be underground.

In Sydney, over 20km of underground 330kV HVDC cable has been installed as part of TransGrid’s Powering Sydney’s Future project. This was a highly complex construction project that runs under inner suburbs with multiple road and rail crossings.

Since these projects were installed, there have been further improvements in cable design and system monitoring, with the technology now providing similar or better reliability than many overhead HVAC transmission lines.

For the most part, the land above the cable can be used as before, in the same way water or gas pipelines cross large parts of rural Australia and are barely noticed by landowners or the community. The easement will allow for general farming activities to continue, including cropping and grazing but some restrictions on activities within the easement will apply, for example construction of a structure or a stock yard, or activities which would result in ground disturbance, such as deep ripping.

Following construction, an 8m wide easement will be applied to the land above the transmission line. This will provide protections to the transmission line and will allow for ongoing access for maintenance as required.

The Syncline Community Cable route was carefully selected to lower the cost of trenching and cable installation. This includes minimising sections of the route passing through river and road crossings, which require Horizontal Directional Drilling (HDD) and independent cable bridges.

In recent times, and for some projects greater than 100km long, the cost differences between undergrounding and overhead transmission towers have reduced. This makes HVDC a cost-effective solution where a point-to-point link is needed.

For Melbourne’s electricity supply from the north-west of Victoria and NSW, HVDC is the preferred solution to cross the outer suburbs, green wedge areas, surrounding bushland. In this densely populated and highly valuable area, overhead transmission, with its associated 80m high towers and 100m wide easement, would have too great an impact on communities and ecological and cultural heritage values.

HVDC technology is rapidly gaining traction internationally, with significant growth in the last 10 years. Refer below to a graph showing global capacity of HVDC as at August 2024.

The Syncline Community Cable is not the first time HVDC technology has been used in Australia, other examples include the undersea Basslink connection from Victoria to Tasmania and the underground Murraylink from Mildura to Red Cliffs in South Australia. The Victorian section of the proposed Marinus Link cable connecting Tasmania and Victoria is also proposed to be underground.

The Murraylink Project is a 176km HVDC cable which has operated in Victoria since 2002, it was completed in 39 months - from conceiving, designing, licencing, permitting, and building through to commissioning stage. It comprises a 150 kV bipolar HVDC cable with 220-megawatt (MW) capacity and is located in north-western Victoria.

Now owned by APA, the project was originally developed by Murraylink Transmission Company Pty Ltd in a 50/50 joint venture of TransEnergie (a subsidiary of Hydro Quebec) and SNC Lavalin – an international project developer.

Syncline Community Cable has been carefully designed over more than 18-months:

>> 1. Development of the reference design during Q4 2023 and Q1 2024

Aurecon developed the network model in PSS®E software, as used by the Australian Energy Market Operator (AEMO) and VicGrid. The software identified the key link that is needed to re-enforce Victoria’s network for the next few decades. Syncline Energy then identified the best technology for that link, having assessed the costs, benefits and technical readiness of different cable configuration and operating voltage.

Infrastructure Advisory Group developed the trench construction method and freeway interface requirements and Australia’s leading HVDC engineers provide the technical specifications.

Syncline Energy provided the reference design and construction method to relevant government departments which provided engineering feedback that was then incorporated into the proposed approach.

During this period, we finalised most of the route with landowners to minimise rock sections, other obstacles and HDD.

We met with EU, US and UK utility operators of HVDC links and discussed Syncline's procurement models, technical specifications and their operating history.

>> 2. Syncline issued the reference design as part of a market sounding in Q3 2024

We sought detailed engineering feedback from the Original Equipment Manufacturers (OEMs).

We selected two Tier 1 global suppliers, and they now lead the technical support for our work.

Syncline is also working with civil contractors that have extensive experience pulling cable, undertaking major civil works in Victoria and installing utilities in road corridors.

>> 3. Syncline appointed engineering firm DNV to review the design, procurement model and benchmark the prices received from the market in Q4 2024

DNV confirmed that Syncline’s capital expenditure and operational expenditure (development costs) aligned to global benchmarks for HVDC projects.

DNV’s work also assessed the cost/benefit of different BiPole and MonoPole configuration and alternative voltages (525kV, 400kV, 320kV) and established the 'grid forming' benefits of the AC/DC converters at each end.

During this time we developed a very detailed regulatory financial model for the Project with Deloitte and Lazard.

>> 4. Based on the tendered unit rates for construction and DNV’s feedback, we refined the route to a 30m wide corridor in Q4 2024 (this is ongoing)

At this point, Syncline had also completed the preliminary ecology and cultural heritage assessments across a 200m wide corridor to identify values and micro site the route, or proposed HDD to avoid impacts to river and road crossings. At this point, Syncline had also completed the preliminary ecology and cultural heritage assessments across a 200m wide corridor to identify sensitive areas and micro site the route, or proposed HDD to avoid impacts and other obstacles.

We are continuing to meet with landowners to micro site the route based on their operations and farm infrastructure needs.

>>5. We met with the market regulator to discuss the “largest credible contingency” for the design and the operating envelope for the converters (this is on-going)

>> 6. Syncline submitted the Environmental Effects Statement (EES) referral package to the planning regulators as a ‘draft for comment’ in Q1 2025

We are incorporating the department’s feedback prior to formally lodging the EES referral. This package includes preliminary noise, ecology, fire, cultural heritage, hydrology, visual and agriculture assessments.

As a Direct Current (DC) cable, SCC will not emit the 50 Hz electro magnetic radiation which is associated with radio interference and electrical charging of metal structures as occurs with AC overhead transmission. This makes DC an appropriate technology for co-location in road and rail corridors, something that is increasingly common in Europe and the US.

Within the Calder Freeway median strip, the cable will be buried to a depth of more than 1.4m in a trench that is less than 1.5m wide.

This means that it will have no impact on future lane widening and intersection plans.

During construction, two work fronts of approximately 10km each will progress north, with one starting at Holden Road and the other from Carlsruhe. These zones will be protected by concrete barriers and gawk screens, with temporary slip lanes developed from the out-bound freeway lane. Construction will take place over 18-months starting in 2027, this will mean:

• Speed restrictions for each of the 10 km sections dropping down to 80km/hr and locally to 40km/hr at access points.

• The conduit will be installed and backfilled in ‘one pass’ with the trench closed-up and the site returned to VicRoads as each 10km section is completed In 2030 works will re-commence, with each 1.2km cable drum to be dropped into the median strip by crane, pulled through the conduits and jointed.

• The cable enters the median strip about 3km north of Calder Park Drive, which means that the most congested part of the freeway through Keilor and Keillor North are not impacted by Syncline's road works.
  

SCC has evaluated all relevant sections of the Road Management Act 2004 (RM Act) and the Department of Transport and Planning Infrastructure Code of Practice - Management of Infrastructure in Road Reserves (Infrastructure Code of Practice).

Section 38 of the RM Act sets out that DTP must have regard to 'matters arising from consultation with the community, utilities … and other stakeholders' and 'facilitate the appropriate use of the road reserve for non-road infrastructure and the effective and efficient delivery or utility … services'.

Section 18 of the Infrastructure Code of Practice includes a Road Safety consideration to 'avoid installing non-road infrastructure longitudinally in freeway reserves' however it also notes that 'where there are exceptions to [this factor,] consideration should be given to undertaking a risk assessment on a case-by-case basis'.

SCC, as fully buried infrastructure, has no bearing on the other factors in Section 18 (being site distances, rigid structures, worker access) and a professionally developed safety assessment will be undertaken to ensure that the risks can be fully mitigated.

The Infrastructure Code of Practice requires that Syncline undertake the following studies:

• Complete Risk Assessment (Section 18), Emergency Management Plan (Section 15 of RM Act) and Risk Management Plan (Section 34)

• Review VicRoad's future development plans along the Calder (Section 20)

• Placement of cable at locations (Section 22), depths (Section 24) and spacing (Section 25) to minimise risks

• Preparation and execution of a Road Agreement (Section 33) supported by the Risk Management Plan (Section 34).