ELECTRA NET – WESTERN SUBURBS REINFORCEMENT PROJECT 275/66, 180MVA THREE PHASE UNITS.

This unit was de-commissioned for some time; it was stored at Morphett Vale East 275kV substation. The unit was disassembled for transport via a special low loader with 97 steering wheels and shifted across to the other side of Adelaide to the LeFevre new substation where the transformer under went a major refurbishment / commissioned.

This was a major contract with strict dead lines and time schedules, during this contract Lazer Tech2005 was on time and budget at every stage.

The "Senior Test Specialist" for ElectraNet was Mr John Tonkin, who inspected / tested prior to livening.

 

Transformer Services Undertaken

Every contract has been completed on time, within budget and to the satisfaction of the client.

OEL Traction Transformer at New Plymouth.

This 220KV Traction Transformer had been dismantled 2 years prior to being awarded the contract to reassemble it, requiring a great amount of flexibility, skill and inventiveness.

This unit was then tested in accordance with the IEC76 Standard, which included partial discharge testing.

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Interconnecting Units 60MVA uprated to 80 MVA, 220/33/16KV.

All eight units have been completed.

All quality assurance 'hold points' approved.

Work involved:-

• Complete dismantling
• Lead modification
• Winding repairs
• Major insulation modifications
• Diverter switch service
• Selector switch service
• Tap changer drive repairs
• Removal and service of all fittings
• Re-assembly of unit
• Dryout and oily tightening. (This unit is complex in regard to the tightening as it is both by clamping rings and wedging in the window.) Special techniques and jigs were developed to effect these complicated repairs.

The " Engineer to Contract" was Mr Graeme Fincher, who inspected at each 'hold point' and monitored the Total Quality.

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Converter transformer 62.5 MVA 16/110KV

Five units completed

All quality assurance 'hold points' approved.

Work involved:-

• Complete dismantling
• Major tank modifications and strengthening
• Recording all aspects of the unit
• Winding replacement
• Working to an extremely tight timetable as the windings had a time restriction placed on them as to the period they could be exposed to the atmosphere
• Dryout and oily tighten
• Final testing to IEC76 Standard including partial discharge testing.

The " Engineer to Contract" was Mr Graeme Fincher, who inspected at each 'hold point' and monitored the Total Quality.

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Aviemore Dry Type Generator Excitation Transformer

Two transformers failed.

Preliminary investigations carried out, recommendations discussed with Mr Graeme Fincher who inspected and approved the recommendations.

To ensure generation was not disrupted for long, one transformer was produced by using the undamaged coils from the two units. The remaining transformer had new redesigned windings manufactured and fitted. The unit was tested and placed successfully back in service, on time, to budget and to the client's satisfaction. As a result of this work, modifications were completed on all the units.

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Oamaru Supply Project 220/110/11kV 38/33.3/20MVA single phase units

These seven units were stored at Bunnythorpe Substation in the middle of the North Island, they were transported to Aviemore Power Station, and refurbished. They were then transported to Waitaki Power Station and installed in a new switchyard. This was a major contract that lasted two years. Our client had strict dead lines and time schedules and during this contract Lazer Tech was on time and budget at every stage.

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Waitaki T28 11/33KV

Gassing fault, releasing nitrogen after six months service. Lazer Tech was called in to suggest and implement a repair.

After discussions with the manufacturer, the unit was drained and put under a vacuum for an extended period. Two installation faults were also repaired.

This work was completed on an urgent basis and total client satisfaction was achieved.

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Aviemore Main generation Transformers 61MVA 220/11kV

These four units were in service for 25 years with no significant maintenance carried out, one unit started gassing. It was taken out of service and dismantled, every part of the winding assembly was found to be loose. The windings were that loose the coils were starting to uncoil. These units required a lot of design modifications to bring them back from near failure. All four in service units have been refurbished.

These units were very close to blowing up. This work has saved our client millions of dollars.

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Manapouri Power Station Transformer repair 105MVA 220/13.8kV

One unit started gassing very badly. When dismantled and inspected it was found the LV lead outs were overheating and burning. The lead-outs were redesigned and reinsulated. The oil flow was redirected to assist the cooling and the unit was reassembled, tested and returned to service. This unit was the last unit to be upgraded, and gave four years perfect service after its repair.

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Manapouri Power Station Transformer upgrade from 105MVA to 135MVA, 220/13.8kV

Our client made the decision to upgrade the seven transformers, Savigliano won the contract to supply and install these new windings using Lazer Tech as the sub-contractor to carry out the site work. This contract required the transformer to be completely dismantled and new insulation installed on the core Limb Stiffeners. This is a major engineering feat laying the core down and replacing this insulation.

There is also a large amount of tank strengthening required so the dry out vacuum will not damage the tank and lid. A new LV bus was manufactured and fitted with new CT’s. A Trafogaurd system installed for constant monitoring and guarding of the new transformer. Lazer Tech installed a trafodry unit and a DGA monitoring system on each transformer, both of these units were interfaced with the new PLC system.

This upgrade was done one at a time and spanned a total of 4 years.

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Rosebud Zone Substation Melbourne Australia 220/22/6.6kV 20MVA

This was the beginning of Lazer Tech contracting in Australia. Three units were refurbished on site.

These units were gassing to fault conditions. Lazer Tech found earthing faults and overheating of the core. These units were very old so Lazer Tech repaired and dried them to the best condition to guarantee the client another 10 years of service.

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Glen Waverley Zone Substation Melbourne Australia 220/22/6.6kV 20/27MVA

Two units were refurbished on site at this substation. This was a unique and challenging job as the two units were contained behind a brick enclosure. Lazer Tech devised a method of repairing these units behind the enclosure, and built a special oven to suit the area. Both of these units were repaired and refurbished to the client’s complete satisfaction.

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Ohau A Transformer 73.33MVA, 220/13.2kV.

First unit to be refurbished at Ohau A, this unit is a Tyree transformer, designed with a bell type case, with the tap changer drive exiting the tank at the bottom. This unit was leaking oil very badly. The main part of the contract was to stop this unit leaking oil. When it was dismantled the top insulation on the windings was found to be split. This did not allow the correct pressure to be on the windings and these were found to be loose. New insulation was manufactured and installed, the unit was reassembled and returned to service.

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Ashburton Electricity 5MVA 33/11kV three phase unit blown winding.

This unit was de-tanked when Lazer Tech was asked if we could repair this unit. It had suffered a major fault when one tapping winding had blown to earth. Our recommendation was to dismantle the winding and inspect the damage on the HV and LV windings before a decision was made to repair or scrap the unit. The HV and LV were in reasonable condition and a new tapping winding was manufactured and installed. This unit was rebuilt to new condition and is now in service and performing excellently.

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Network Waitaki

Lazer Tech has refurbished eight units for this power network ranging from 3 to 10 MVA. We have developed a relationship where an open book contract sees all transformer maintenance and refurbishment is assigned to Lazer Tech. The client is happy with the professional service and the competitive rates.

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Other work undertaken.

Although Lazer Tech specialises in Transformer refurbishment we have been in the high voltage maintenance industry for many years. The following is a list of other work we have undertaken during this time. This is not a complete list as some jobs are too small to mention.

• Main Generator rotor coil repairs at Ohau A Power Station
• Installation of resistor banks at Benmore
• Installation of new 11kV and 400v reticulation at Cobb River Power station.
• Installation of new gate control equipment at Twizel and Cobb.
• Maintenance lighting contracts on Aviemore, Benmore and Waitaki Power Stations
• Oil sampling and testing of all South Island Transpower owned transformers for three years before policy changes within Transpower removed this contract.
• Installation of dewatering pumps and controls.
• Manufacture seismic restraints for earthquake protection on transformers at Manapouri
• Manufacture and install new pipework and coolers at Waitaki to change the transformers from water-cooled to forced air radiators.
• Assisted ABB with Generator assembly at Ohau A
• Remove and install new generator cooling water pipes
• Install, wire and commission auxiliary generator at Benmore headgates.
• Assist ABB with the manufacture of seismic restraints at Benmore

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