Requests for expressions of interest for non-network solutions to address fault level shortfalls.


Under the National Electricity Rules (NER) the responsibility to resolve a fault level shortfall lies with the System Strength Service Provider, who is the Transmission Network Service Provider (TNSP) or jurisdictional planning body for the region. In Queensland, Powerlink is the System Strength Service Provider who must address these technical issues as efficiently as possible once they are identified.

REQUEST FOR SYSTEM STRENGTH SERVICES

On 9 April 2020, AEMO published a report 'Notice of Queensland System Strength Requirements and Ross Fault Level Shortfall' to the National Electricity Market (NEM) under Clause 5.20C.2(c) of the National Electricity Rules (NER). The report declares an immediate fault level shortfall at the Ross 275kV node, includes other pertinent technical information and advises that fault level services should be in place to meet this shortfall by 31 August 2021. The shortfall is currently forecast by AEMO to continue beyond 2024-25.

Powerlink commenced an Expression of Interest (EOI) process for both short and long term solutions to address the Queensland Fault Level Shortfall at Ross in April 2020 and submissions closed on 13 May 2020.

Powerlink received a very strong response to the EOI offering a range of system strength support services to address the fault level shortfall at Ross and have been working closely with AEMO on the proposed remediation approach.

In June 2020 AEMO approved the approach for the short-term, up until the end of December 2020. As a result, Powerlink entered into a short-term agreement with CleanCo Queensland to provide system strength services through utilising its assets in Far North Queensland.

Since that time, and based on the submissions received, AEMO has provided preliminary confirmation that subject to the final exchange of modelling and other details, inverter tuning could reduce the overall system strength requirement at Ross. Consequently Powerlink has entered into an agreement with Daydream, Hamilton, Hayman and Whitsunday Solar Farms in North Queensland to validate the expected positive benefits of inverter tuning during the daytime.

In addition, Powerlink continues to work on assessing long-term solutions to address the fault level short-fall.

Offers received as part of the EOI process remain current and it is anticipated the results of the assessment will be known by around late 2020 and Powerlink will provide a further update at this time. 
 

System strength is a measure of the stability of a power system under all reasonably possible operating conditions. It describes a system’s overall performance and its ability to recover quickly from sudden events.

Synchronous generators – like coal, gas and hydro power stations – provide system strength when they generate. System strength can also be provided by machines called synchronous condensers.

Asynchronous generators – like wind and solar – do not provide system strength and require system strength from another source.

While a system strength shortfall is very unlikely to impact the ongoing supply of electricity to customers in Queensland, it may limit an asynchronous generator's capability to export power to the grid. Queensland has a broad mix of generation types located across various regions in the state which can be accessed through our transmission network in the unlikely event that supply is impacted.

The Australian Energy Market Operator (AEMO) is responsible for setting the minimum required level of system strength throughout the National Electricity Market (NEM). When a region is identified as not having the required system strength, AEMO declares a shortfall.

As with other Market Notices, it is simply designed to send a signal to the market that a response is required.

AEMO periodically re-evaluates the required minimum fault levels throughout the NEM to minimise the risk of a sudden, widespread loss of supply due to an unforeseen event that impacts system strength.

AEMO has conducted electromagnetic transient (EMT) studies of the Queensland power system using the PSCAD product. This modelling includes detailed models of synchronous generators from major coal-fired, gas-fired and hydro power stations in Queensland. Only inverter-based plants not subject to the system strength remediation requirements were considered in this requirement determination.