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

4.1 CIRCUIT BREAKERS
0BInvestment Evaluation Summary
TNM-GS-809-0720
The 110 kV circuit breakers (five units) installed at Knights Road Substation are Reyrolle type 110/OS/10 units. The
‘Reyrolle Type 110/OS/10 110 kV Circuit Breaker Condition Assessment Report’ (TNM-CR-806-0772) assesses the
condition of Reyrolle circuit breakers and recommends that the units at Knights Road Substation be replaced. The circuit
breaker condition assessment has been based on key asset management considerations including technical, design,
reliability, condition, maintenance, spares and contingency planning, life-cycle and environment issues. The condition
assessment report provides details of the many failures and defects associated with Reyrolle 110 kV circuit breakers,
including those installed at Knights Road Substation. The condition assessment report has identified that the Reyrolle
circuit breakers:
� have a number of inherent technical and design deficiencies that have adversely impacted transmission circuit
reliability and availability;
� are unreliable, in particular the air and insulating oil systems;
� are maintenance intensive and costly to maintain when compared with modern equivalent units;
� require spare parts that are no longer available from the manufacturer’s agent;
� require skilled personnel to maintain - the availability of specialised maintenance resources is declining; and
� have reached the end of their useful service lives.
All other transmission companies in Australia and New Zealand have already replaced their population of Reyrolle type
110/OS/10 circuit breakers, or are in the process of doing so, for the same reasons outlined above. Transend’s reasons for
replacing this type of circuit breaker are no different to those of other industry participants.
The Reyrolle circuit breakers at Knights Road Substation will be 53 years old when decommissioned.
The preventive maintenance costs associated with the 110 kV circuit breakers include:
� circuit breaker maintenance: $7,900 per circuit breaker (six yearly);
� insulating oil costs: $4,200 per circuit breaker (six yearly);
� compressor maintenance: $1,000 per compressor (six-monthly for the two compressors at Knights Road Substation);
� silica gel maintenance: $500 per circuit breaker (two yearly); and
� pressure inspection costs: $300 per circuit breaker (three yearly).
In addition, the average historic repair cost for a failure or defect associated with a Reyrolle type 110/OS/10 circuit
breaker is $4,730.
Further information on the circuit breaker population can also be found in the Extra High Voltage Circuit Breaker Asset
Management Plan (TNM-PL-809-0541).
4.2 VOLTAGE TRANSFORMERS
The 110 kV voltage transformers in service at Knights Road Substation (six single phase units) are ASEA type EMFA
120 units that were manufactured in 1962. The voltage transformers at Knights Road Substation have high percentage
power factor readings, which indicate excessive moisture in the insulating oil and likely degradation of the winding
insulation. Voltage transformers of this type have failed explosively in the past. The explosive failure of a voltage
transformer presents a major safety risk to employees and contractors, should they be working in the vicinity of the
voltage transformer at the time of failure. In addition, a major voltage transformer failure would inevitably cause
significant disruption to electricity supply.
The EHV Voltage Transformer Asset Management Plan (TNM-PL-809-0614) recommends that the ASEA type EMFA
120 voltage transformers at Knights Road Substation be replaced because they are in poor electrical condition, are
susceptible to major failure and are an obsolete design. The voltage transformers will be 53 years old when replaced.
The average maintenance costs associated with 110 kV voltage transformers is $5,500 per three phase set.
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