Power System Strength
Strengthening South Australia’s power system
South Australia has become a world leader in renewable energy generation. This means that traditional synchronous generation sources, such as gas-fired units, now operate less often.
A secure power system needs adequate levels of system strength and inertia, which to date have been provided by traditional synchronous generators.
To maintain and manage the security of the power system this traditional source of system strength now needs to be provided by other means. In October 2017, the Australian Energy Market Operator (AEMO) declared a gap in system strength in South Australia, which requires ElectraNet to use its reasonable endeavours to address this gap on an ongoing basis.
System strength relates to the ability of a power system to manage minor fluctuations in supply or demand while maintaining stable voltage levels, ensuring stable and secure supply for customers. A lack of system strength on the power system brings with it an increased risk of system instability and supply interruptions.
ElectraNet has been investigating options to address this gap to ensure we can provide customers with a reliable and secure power system, while also keeping costs down. Options include entering into contracts with generators or installing synchronous condensers.
Following an analysis of these options through a generator tendering process and advice from independent energy market experts, the installation of synchronous condensers on the network has been determined to be the most efficient and least cost option.
A synchronous condenser operates in a similar way to large electric motors and generators. It contains a synchronous motor whose shaft is not directly connected to anything, but spins freely and is able to adjust technical conditions on the power system. Synchronous condensers are an important source of system strength and other services such inertia.
The implementation of a synchronous condenser solution has the support of AEMO, the AER and the South Australian Government. It is expected to be fully operational by the end of 2020.
Importantly, the solution is also anticipated to deliver a net saving to customers equivalent to $3 to $5 per year on a typical South Australian residential electricity bill from the time of commissioning, as it avoids the increasing costs being incurred by AEMO in directing and compensating existing gas fired generators to manage the gap.
Detailed technical analysis undertaken in consultation with AEMO and manufacturers to determine the number, size, specification and design of the synchronous condensers required to meet the system strength gap.
On 18 February 2019, ElectraNet was advised by the Australian Energy Regulator (AER) that it has determined that ElectraNet has performed an economic assessment that is equivalent to the Regulatory Investment Test for Transmission (RIT-T) and proportionate to the identified need. The AER also determined that the high inertia synchronous condenser solution identified by ElectraNet in its Economic Evaluation Report reasonably satisfies the economic evaluation requirement; i.e. the AER has effectively provided regulatory approval for the proposed synchronous condenser solution.
You can read the full report here: System Strength Economic Evaluation Report.
Before proceeding, our proposed solution still requires technical approval from AEMO (expected in coming weeks) and final revenue approval from the AER (later in 2019).
Further background details are also available in the project’s information sheet.
Likely synchronous condenser sites