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Challicum Hills Wind Farm: Pacific Hydro claims information provided to AEMC by NEMMCO, “inaccurate and misleading”

Posted by gmarkets on 3 September, 2007

Lane Crockett, the General Manager of Development for Pacific Hydro, wrote in relation to NEMMCO’s supplementary submission to the AEMC dated 1 August 2007 “incorrect and inaccurate statements made by NEMMCO in its supplementary submission, and in particular those which relate to the Challicum Hills Wind Farm and its relationship to the V>SML_NIL_7 constraint equation”. NEMMCO used the example of Challicum Hills to illustrate a perceived need to include a distribution connected wind farm into central dispatch and thus have the ability to control its output. Pacific Hydro considered the information provided to the AEMC to be both inaccurate and misleading.

Overload risk: Murraylink run to zero at <300ms: The following paragraphs detail the actual operation of the Challicum Hills wind farm on the network system in western Victoria, and have been confirmed by VENCorp and Powercor. The 66kV line that runs in parallel with the Ballarat – Horsham 220kV line has always been at risk of overloading if the 220 kV line was tripped, which was the case prior to the connection of the Challicum Hills wind farm. As a result of this risk of overload, VENCorp required that the Murraylink interconnector be run back to zero in a very fast manner (<300ms). The speed of the run back scheme was such that Murraylink flow was assumed to be zero when assessing the Victorian thermal limits following a trip of the Ballarat – Horsham 220kV line. This applied for Vic to SA export conditions.

Ballarat North-Buangor 66kV limit in worse case conditions: VENCorp confirmed that the worst case conditions under which the Ballarat North – Buangor 66kV limit may apply where there was peak summer loading in the outer state grid, reduced import from Snowy or Vic export to Snowy, and the Challicum Hills wind farm output was at zero. It was important to note that any output from the Challicum Hills Wind Farm actively improved the loading limit on the line as it reduced the Horsham terminal station load and hence the loading on the Ballarat North – Buangor 66kV line, simultaneously increasing the allowable flow over Murraylink. Thus the post contingent distribution network loadings were actively reduced by the embedded generation of the wind farm.

The solutions to problems: When Pacific Hydro negotiated the connection of the wind farm with Powercor, the existing overloading of the line was taken into account. As a result of this, Pacific Hydro provided in the design a ring bus arrangement in the Buangor substation along with a split bus with dual Static VAr Compensators in the wind farm itself. Buangor became the point at which the 66kV line would be opened to avoid the overloading situation. When the circuit breaker at the substation was opened the wind farm splits in half, half the power goes to Ararat, half goes towards Ballarat North, both sides with appropriate voltage control devices. The generation therefore would reduce the power flow out of Ballarat North. Powercor Operations has full control of the circuit breaker. The line rating that Powercor provided to VENCorp was a continuous rating which gave the Powercor operator ample time in which it could operate the circuit breaker to avoid extended periods of high loading on the line.

Reference: Lane Crockett, General Manager Development, Australia / Pacific, Pacific Hydro, Re: Response to NEMMCO’s supplementary submission, 14 August 2007, Writers direct contact: lcrockett@pacifichydro.com.au ph: 03 9615 6490, http://www.aemc.gov.au/pdfs/reviews/Central%20Dispatch%20and%20Integration%20of%20Wind%20and%20Other%20Intermittent%20Generation/submissionssup/001Pacific%20Hydro%20Supplementary%20Submission.pdf

Erisk Net, 29/8/2007

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