A reliable electricity network is an essential element for supporting growing areas. Parts of the inner Sydney network, which supplies electricity to more than 500,000 customers, are over 50 years old. To solve the problem of growing demand coupled with aging infrastructure, TransGrid is exploring non-network solutions to delay capital investment into costly network upgrades.

As the network approaches the end of its serviceable life and suffers from increased demand, TransGrid’s Powering Sydney’s Future (PSF) project will reinforce the power supply.

Part of the solution involves constructing a new 330kV, 20km long underground cable circuit between substations at Potts Hill and Alexandria.

As this is a large and complex project, TransGrid is deferring investment into the cable construction by procuring a variety of demand management solutions to reduce the risk of unserved energy to consumers for four years.

Building of the cable will begin in 2020.

The extent of the problem

A major cable failure in the inner Sydney network would take around eight weeks to solve. During that time, the network would experience significant load issues during peak demand periods.

Most of the load in the Sydney area is driven by the demand in the CBD, and the demand in the CBD is largely driven by air-conditioning, meaning that TransGrid’s non-network solutions will only be needed during the summer months.

TransGrid’s Energy Services Manager, Rachele Williams, said the project area is very highly populated, with many customers who highly value reliability of supply, such as hospitals and universities.

While the likelihood of a cable fault is statistically low, the risk increases as the cable ages, and the impact of a failure and power outage in Sydney’s CBD and surrounding suburbs would be very significant.

“It’s not just about people’s lights going out, or their fridge not being on, or their air-conditioning going off. An outage in this area could be detrimental to significant pieces of infrastructure, including Parliament House, the ASX and the main operational hubs for public transport,” Ms Williams said.

“There were similar instances in Auckland in New Zealand in 1997, which had a nine-figure economic impact.”

Special planning criteria

The PSF project is based in a part of Sydney that has a special planning criteria called Modified N-2, which means if you were to take away any two elements, the network would still need to be able to function.

“Most of the rest of our network only has an N-1 requirement. The way that we meet the Modified N-2 requirement is that we work together with Ausgrid, the distribution network, to achieve that higher reliability requirement,” Ms Williams said.

“The PSF project is looking at the future of the network in that area. There are a number of aging cables, and we would reasonably expect their condition to start to deteriorate. We need to cost-effectively ensure that the area has appropriate reliability, which is why we are targeting four years of non-network solutions and installation of a 330kV cable in 2022.

“If we don’t think about cost-effectiveness, we could just put six cables in, and that area could be really reliable. How do we balance not spending too much on the network, while still making sure that we don’t risk supply?

“It’s finding a balance between not increasing customers’ bills too much, and delivering good quality power.”

Two years in the making

One of the major parts of the project involves exploring all potential non-network solutions. In order to thoroughly understand the available options, TransGrid went above and beyond the requirements of the regulatory investment test for transmission (RIT-T) process, which took approximately two years, to ensure they could address the issue with confidence.

“Part of the RIT-T is demonstrating either a consumer benefit, such as bringing prices down, or a reliability benefit, which is what this particular project is driving at. Then we have to scope out all the things we can do to actually solve the problem,” Ms Williams said.

“A large part of it is about consultation. There are three different major documents that get sent out, inviting interested parties to make submissions. If they’ve got an idea that we haven’t considered we want to hear about it, and we ran quite a few workshops and market soundings in terms of seeking information from the industry about what would be available.

“We have also worked very closely with not just the regulator, but with other groups, such as Energy Consumers Australia and the Energy Users Association of Australia, to determine what would be an appropriate optionality in terms of the project.

“The demand management element of the project is a very significant part of making sure that we meet community expectations around looking for other options, and doing things that are innovative and different to the way that we’ve done them before.”

Non-network solutions

In October 2017, TransGrid put out an expression of interest for demand management solutions.

The five key non-network initiatives being investigated are:

  • Energy efficiency – technology changes that can enable the use of use less energy and while still achieving the same outcome
  • Demand response – working with customers to reduce energy use during times of peak demand
  • Reliability standards – agreeing to a different level of reliability (e.g. requiring fewer electricity network assets at the risk of more outages)
  • Local generation – installing local generation to help supply local energy and reduce the demand on the network
  • Network planning – reinforcing the network by renewing the existing underground cables or installing a new underground cable into Sydney

Ms Williams said TransGrid has seen a very strong response from non-network proponents in its early consultation, and there is a lot of potential for deferring the commissioning of network infrastructure through the use of non-network solutions.

In July 2018, TransGrid opened a tender to supply 20MW for the 2018-19 summer period.

“We got a very reliable, very dependable managed solution for the first block in the form of load curtailment, and what we found during the summer was that we’ve got a great building block that will support the development of our program,” Ms Williams said.

“In the event that we needed to reduce demand, we have contracts in place that say run your load curtailment system to take yourself off the grid and reduce your load.

“Those customers will have already installed devices so that in the event that the grid was to switch off and they were to experience an interruption to supply, they would be able to supply themselves.”

The road ahead

After the success of the first tender, the second stage will be the release of a new tender that will seek an additional 20-40MW for summers 2020-21 and 2021-22.

Prospective tenderers can find more information here .

“From here we will be going out with another tender, and that’s when we hope to be able to introduce some more innovative sources like renewable energy,” Ms Williams said.

“We’ve seen some volatility in forecasts, so having a program like demand management on the ground and running gives the business much more flexibility about what it does, and means we can say we’re not leaving Sydney at risk.”

After four years of demand management, TransGrid will commission an underground cable circuit between substations at Potts Hill and Alexandria. To minimise potential future disruption, the project includes installation of additional infrastructure to allow for a second cable circuit at a later stage.

For the majority of the 20km cable, TransGrid will dig a trench about 3m wide by 1.2m deep and install conduits before burying them and restoring the area.

The new cable circuit will mainly be installed underground with some cable bridges to cross rail lines and waterways. The proposed cable route includes work on the edge of Sydney Park near the City of Sydney Park Nursery Depot.

TransGrid is continuing to work with City of Sydney to minimise impacts to the park and will confirm the final location of the route as the project progresses.

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