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Airservices Australia acts on power failure report.



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17 August 2000 A129/2000

AIRSERVICES AUSTRALIA ACTS ON POWER FAILURE REPORT

Airservices Australia is acting urgently to implement the recommendations of the Quiggin Cook review of the power supply system at Sydney Airport.

The Deputy Prime Minister and Minister for Transport and Regional Services, John Anderson, called in senior managers from Airservices Australia for a briefing with the Quiggin Cook review team last week. Mr Anderson commissioned the review following the power failure at the airport on 1 August.

"The air traffic control system at Sydney Airport has to work all the time. The Airservices Board and senior management understands that the Government views the reliability of the Sydney Airport power supply as critical.

"Quiggin Cook reviewed the power failure and made 10 recommendations to reduce the risk of a similar power failure immediately and substantially. Quiggin Cook endorsed the actions taken by Airservices Australia and Sydney Airport to restore power following the outage, which included adjusting the protection devices on the mains transformers and the emergency generators, and installing an additional generator.

"Airservices is implementing the recommendations urgently, and is confident they will minimise the potential for future power outages at Sydney Airport. Airservices has done everything possible to enable the Sydney Airport control centre to operate smoothly through the Olympics period and beyond.

"Quiggin Cook is completing a comprehensive review of the power supply system and will be making additional recommendations for longer term improvements to the system’s reliability.

"I have directed Airservices Australia to upgrade the power supply system in the longer term so it meets industry best practice for similar critical installations. Sydney Airport has the best air traffic control system in the world, which must be backed up by a first-class power supply.

"Quiggin Cook noted that both the 6 July and 1 August power failures occurred when parts of the power supply system were disconnected for pre-Olympics maintenance. The maintenance work meant that some backup systems were not available to maintain supply when unexpected problems emerged. The critical pre-Olympics maintenance has now been completed.

"Quiggin Cook has advised that no further invasive maintenance and testing work should be carried out until after the Olympics. Airservices has accepted the recommendation. The few remaining projects and changes that are essential for the Olympics will be allowed to proceed, however, none of these involve the main and standby power to the operational systems.

"Airservices has installed a third backup generator to provide additional emergency power. Six experienced electrical maintenance staff are available at Sydney Airport and the shift rosters will be extended to cover the the entire 6:00am to 11:00pm non-curfew period.

"Quiggin Cook concluded that the mains power failure occurred after one of the two transformers supplying the control centre was disconnected for maintenance. The electrical load on the remaining transformer exceeded the limit set by its protection device and it shut down. Sydney Airport

immediately disabled the transformer’s protection unit, which rectified the cause of the failure.

"The duty backup generator started automatically, but shut down because it could not supply the full load. Airservices staff attempted to start the second generator manually, but it shut down as well. Quiggin Cook found that the protection devices on the generators had not been set correctly, but observed that Airservices had swiftly reset them properly.

"The air traffic control system continued to operate safely throughout the power failure on its emergency batteries, although the controllers had to restrict movements through the airport in case the power supply situation worsened," Mr Anderson said.

A129/2000 ATTACHMENT (16Kb PDF)

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© Commonwealth of Australia 2000 Last updated:  Thursday, 17 August 2000

1

Issue Quiggin Cook Recommendation Airservices Australia Response

Transformer Differential Protection

We do not consider that it is practical to complete this installation and commissioning in the short term. The review notes however, that this form of protection is necessary in the long term to limit any damage to a transformer during an internal fault as well as providing good discrimination against through faults and upstream devices.

The installation of CT’s on the incoming bus-bar of each switchboard would require substantial down-time and the commissioning would also result in an increased risk to the installation. The amount of down-time would be subject to a detailed review of the MSB segregation for work on live switchboards. This is a weakness with installations not based on a system plus system arrangement.

The transformers are well maintained, with regular oil tests provided and therefore the likelihood of an internal fault in the short term is remote.

The transformer differential protection was immediately disabled after the failure, thereby rectifying the cause of the mains failure.

The recommendation to defer installation of current transformers until after the Olympics has been accepted by both Airservices and Sydney Airports Corporation Ltd (SACL). The installation will take place as soon as possible thereafter.

We would recommend the decision to proceed with the planned maintenance/tests for Transformer 2. Completed. The planned maintenance was undertaken on 4 August.

It is imperative that specific temporary instructions and lock-out tags are put in place to keep the protection disabled until the responsible officer removes the instruction.

Agreed. SACL has indicated agreement to the fitting of lock-out tags and specific instructions, with written confirmation expected prior to a meeting between SACL and Airservices scheduled on 17 August.

2

Availability of Back Up In order to maintain an acceptable level of redundancy for the generators it is recommended that the temporary portable unit be

retained as it is presently connected, with specific, temporary instructions put in place for its operation. The following considerations are relevant to this recommendation:

• Generator B due for major service. • Undervoltage protection not yet tested with worst case UPS bypass load, which will be more onerous. • Longer-term concern is that the load base (due to the type and

size) is now too large for one generator due to the high proportion of technical load.

Agreed. A long term hire agreement for the additional (third) generator is in place, with temporary instructions and staff familiarisation being arranged.

Following the failure on 1 August, Airservices investigated the reasons for the generators not accepting load, and rectified their settings. They now work satisfactorily. Quiggin Cook has agreed with the finding by Airservices engineers that the protection devices connected to the two backup diesel generators were not set appropriately.

Quiggin Cook will be advising Airservices further on the load base issue.

Experienced staff that are familiar with the interim operation of the portable generator should be available during the peak periods.

Agreed. There are six electrical staff located at Sydney airport. Three are day workers and the others provide single person shift coverage from 6:00 am to 9:30 pm. From 28 August the shift will be extended to 11:00 pm, which will cover the full non-curfew period at Sydney.

The temporary generator should also be tested on the switchboard, which has not yet been tested. Completed. Testing of the temporary generator was completed during the curfew on 11 August. This

involved operating the generator into ‘A’ and ‘B’ switchboards and associated loads independently, and then with the generator supplying with the combined ‘A’ and ‘B’ loads.

It is recommended that the Generator B service is postponed unless there is evidence of substantial/catastrophic failure occurring for the anticipated duty up until the end of the Olympic period.

Agreed. The service has been suspended from the program. To be confirmed by analysis of the engine oil.

3

Static Switch and Rectifier Current Limitation Problem

The Static Switch and rectifier current limitation problem experienced in July needs to be fully resolved with the Manufacturer and tested (as to the exact nature of the rectifier problem and the static bypass failure). The UPS arrangement is not a true parallel redundant configuration and as such, it could be considered as a single point of failure if it were not for the further consideration that the critical service can operate with either half of the equipment subject to certain procedures being followed by Airservices.

Agreed. Airservices is continuing with engineering analysis of the root cause of the failure that occurred on 6 July, including working cooperatively with the manufacturer of the UPS system. Airservices has not yet established that the UPS static bypass failed.

The failure occurred while the total load was being switched to a single UPS for routine maintenance. This practice has been suspended pending completion of the analysis. Extensive testing has been carried out on the UPS systems in the normal operating configuration with no abnormality detected.

Postpone Invasive Maintenance and Testing

It is recommended that all invasive maintenance and testing is postponed up until the end of the Olympic period. It is acknowledged that there has been an extra ordinary amount of switching and maintenance recently, mainly due to the requirement to freeze all major switching activities during the build up to the Olympic Games.

Agreed. All critical maintenance across all systems which was brought forward is now completed. Routine non-invasive maintenance will continue. No additional project work on the main power supply and standby generators or UPS system is to occur before the Olympics. The few remaining (non-power system) projects that are considered essential for the Olympic effort are scheduled for completion by 28 August.

Circuit Breaker Further investigation is required into the reason for the Bus B, ATS circuit breaker trip that delayed operation of the Generator B during the failure. To date, the only explanation is that there is a control interlock with the transformer output circuit breaker located immediately upstream of the ATS. Quiggin Cook & Associates will need to liaise further with the maintenance staff to ascertain this.

Agreed. This fault is still being assessed as part of the internal engineering investigation. It has already been noted that visual indicators could be improved. Airservices suspects that an internal interlock inhibited manual operation of the Automatic Transfer Switch (ATS).