On 16 April 2009 the Reliability Panel (Panel) published its final determination for the review of the mainland frequency operating standards during periods of supply scarcity.

In its final determination, the Panel has amended the frequency operating standards for the NEM mainland that apply in an islanded region during periods of load restoration. The minimum allowable frequency for a single generator contingency during load restoration following an islanding event is:

• 48.0 Hz for the Queensland and South Australian regions;
• 48.5 Hz for the New South Wales and Victorian regions; and
• in cases where an island incorporates more than one region, the critical frequency to be adopted is the maximum value of the critical frequencies for these regions.

Background

NEMMCO Request

On 6 November 2007 NEMMCO requested the Panel to review the frequency operating standards for the mainland of Australia during periods of supply scarcity associated with load restoration events. This request follows the investigations into the events involving the loss of supply in Victoria on 16 January 2007. In particular, NEMMCO is seeking clarification from the Panel as to whether it is intended, under the frequency operating standards, for sufficient generation to be held in reserve to cover the loss of a generating unit during periods of load restoration following a contingency event.

In its request, NEMMCO proposes that during periods of load restoration following a contingency event:

• on the mainland - that the load should be restored to the level of available generation less a pre-determined amount for frequency regulation, to ensure that the frequency would not fall below 47.5 Hz upon the loss of the largest generating unit; and
• in the case of Tasmania - that sufficient FCAS is available to manage the power system frequency within the frequency operating standard in the event of a credible contingency taking place.

NEMMCO's request includes substantial analysis in support of its recommendations including balancing the need to restore interrupted load with an increase in the risk of a cascading failure. 

On 18 March 2008, the AEMC approved terms of reference for the Panel to conduct this review as required under clause 8.8.3 of the National Electricity Rules. The Review was conducted in accordance with clause 8.8.3 of the National Electricity Rules. A notice indicating the commencement of this review was also published on 18 March 2008.

The Panel invited comments on this review from stakeholders, which closed on Friday, 2 May 08. The Panel received submissions from Powerlink, the ERAA and the NGF.

The submissions raised a number of issues and the Panel considered that it should consult on a draft report prior to finalising this review.

On 19 June 2008 the AEMC approved amended terms of reference that allowed the Panel to consult on a draft determination for this review, rather than proceeding directly to a final determination, as required by the original terms of reference. This amendment to the terms of reference did not change the requirement on the Panel to complete the review by the end of 2008.

On 24 September 08 the Panel published its draft determination for the review of the mainland frequency operating standards during periods of supply scarcity.

The AEMC further amended the terms of reference on 13 January 2009 to allow the Panel to seek additional advice from NEMMCO in respect of an issue that was raised through submissions on the draft determination.

To allow sufficient time for consultation on an explanatory note, given that the final advice from NEMMCO was a material change from the draft determination, the AEMC further amended the terms of reference on 3 March 2009 to allow the Panel to complete the review by 30 April 2009. On 6 March 2009 the Panel published an explanatory note seeking additional consultation on the specific issue of the frequency operating standards that apply in an islanded region. Specifically, the minimum allowable frequency for a single generator contingency during load restoration following an islanding event. The Panel did not receive any submissions on its explanatory note.