Casuarina Zone Substation preliminary report

11 Nov 2008

The preliminary report is a thorough examination of the technical causes of the outages.

Power and Water will carry out the report’s three immediate recommendations, with two already in hand and the other starting straight away.

Andrew Macrides, Managing Director of Power and Water said, ‘The Preliminary Report sets out clearly how the oil circuit breaker at Casuarina failed and the causes of the other outages around that time. It reports a number of technical matters we can learn from.

‘I am pleased the Report confirms that the temporary access restrictions to substations were justified, that the prospects of wider outages are low and the decision to replace the whole switchboard is sensible.

‘We are looking forward to the draft and final reports. They will turn to the wider causes. I am sure Mr Davies will make recommendations on how we can improve our maintenance practices and the people, skills and training we will need to do that. I will make sure those recommendations are carried out as quickly as possible.

‘These were major events that inconvenienced many customers, however, the recovery effort was commended in the preliminary report and particularly the restoration after the oil circuit breaker exploded. I would again like to thank all the staff who helped achieve this.’

The preliminary report’s first recommendation is that ‘a rigorous condition assessment of all Zone Substation Distribution Switchboards (11 and 22kV) should be initiated immediately’ and that ‘a high level risk analysis should be undertaken to determine program priorities and timetable.’

This work started after Mr Davies, the Chair of the Inquiry, first arrived in Darwin. A major program, reporting directly to the Managing Director, has been set up to plan and carry the work out. The program will complete the condition assessment by the end of February 2009.

At many sites, staff cannot carry out work without first switching off all the equipment. The Preliminary Report endorsed this safety first approach. As the condition of the switchboards is assessed and as necessary repaired, it will be possible to lift these restrictions.

Where possible, Power and Water will plan these works so that, although the substation is switched off, there will be no customer outages. Where a customer outage is absolutely necessary, it will be as short as possible, taken at the least inconvenient time and plenty of notice given.

The Preliminary Report’s second recommendation is that ‘the efficacy of all frame leakage protection systems (or other high-speed busbar protection systems) should be verified and remediated, if necessary.’ This testing will start as soon as possible and be incorporated in the program described above.

The Preliminary Report’s third recommendation is that ‘immediate action should be taken to replace the Casuarina Zone Substation 11kV switchboard.’

The specification of the new switchboard and early planning for its construction is finished. The purchase of the new switchboard should be completed in the next few days, with final commissioning expected in June/July 2009.

In the meantime, a temporary switchboard will be installed at Casuarina substation before Christmas. It will restore the substation to what is known as a ‘secure state’, where most equipment shutdowns don’t affect customers.