Transend - Appendix 5 Renewal capital expenditure - Australian ...

0BInvestment Evaluation Summary
TNM-GS-809-0720
Moisture ingress in the insulating oil degrades the winding insulation and increases the risk of explosive failure. While
Transend has not experienced any major failures of Balteau voltage transformers, other Australian transmission
companies have reported explosive failures of Balteau voltage transformers of a similar design. The explosive failure of
a voltage transformer presents a major safety risk to employees and contractors working in the vicinity of the voltage
transformer at the time of failure.
The EHV Voltage Transformer Asset Management Plan (TNM-PL-809-0614) recommends that Balteau type UEV110
voltage transformers be replaced.
Ducon voltage transformers
Ducon type PD 110 kV voltage transformers are approaching the end of their service lives, have inherent design
deficiencies and are susceptible to explosive failure. Transend has experienced explosive failures of Ducon 110 kV
voltage transformers at Palmerston Substation in 2001 and at Avoca Substation in March 2008. Both failures resulted in
a fire of the voltage transformer. Figure 3 presents an image of a failed Ducon 110 kV voltage transformer and porcelain
fragments in the switchyard.
Figure 3 – Explosive failure of a Ducon 110 kV voltage transformer at Avoca Substation (March 2008)
Ducon voltage transformers that were manufactured prior to 1973 incorporated a unique gasketing system where a
neoprene rubber gasket was encased within a lead sheath to protect the rubber from the insulating oil. As the units age,
the lead sheath becomes susceptible to creeping inward causing lead to fall inside the unit, or the rubber to be exposed to
the insulating oil which hardens the rubber and results in deterioration of the oil seal.
The EHV Voltage Transformer Asset Management Plan (TNM-PL-809-0614) recommends that Ducon type PD voltage
transformers at Meadowbank Substation be replaced.
The average preventive maintenance costs associated with 110 kV voltage transformers at Meadowbank Substation is
$5 500 per three phase set.
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