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

4.1.2 TUNGATINAH SUBSTATION
0BInvestment Evaluation Summary
TNM-GS-809-0720
From 1999 to 2003, Transend replaced six English Electric 110 kV air-blast circuit breakers that presented a significant
safety risk because they were susceptible to explosive failure. The circuit breakers were only installed temporarily using
available spare units because of the impending substation redevelopment project. One of the explosive failures that
occurred at Tungatinah Substation caused a statewide blackout in 1979.
The 110 kV circuit breakers installed at Tungatinah Substation include the following types:
� ABB type LTB145D1 - one unit (age 13 years);
� Mitsubishi 100-SFMT-40E - six units (average age 11 years); and
� Siemens 3AP1DT - two units (average age 9 years).
The circuit breakers currently in service at Tungatinah Substation will be redeployed elsewhere in the transmission
network.
4.2 DISCONNECTORS AND EARTH SWITCHES
4.2.1 ASSET CONDITION
The 110 kV disconnectors installed at Tarraleah Switching Station and Tungatinah Substation comprise the following
types:
� Acelec types 06732 and HDBE;
o Tarraleah - three units (average age of 58 years); and
o Tungatinah - two units (average age of 55 years).
� Essantee types 05533, 05551, 05552 and 09279
o Tarraleah - 11 units (average age of 58 years); and
o Tungatinah - 14 units (average age of 56 years).
The average maintenance costs associated with the 110 kV disconnectors at Tarraleah Switching Station and Tungatinah
Substation are $3,000 per disconnector.
Details of each disconnector type can also be found in the Extra High Voltage Disconnector and Earth Switch Asset
Management Plan (TNM-PL-809-0606).
Acelec disconnectors
The Acelec disconnectors are in very poor condition and are susceptible to thermal failure of the conductive braids. This
type of disconnector is difficult to maintain due to a complex fixed contact arrangement. In addition, a number of
disconnectors are mounted on girders and/or underhung approximately 10 metres above ground level, requiring
additional resources to maintain.
Any spares required to sustain this type of disconnector in service needs to be locally manufactured or salvaged from
decommissioned units.
In the past, a serious safety incident occurred at Tarraleah Switching Station when a post insulator associated with a
girder-mounted 110 kV disconnector mechanically failed while it was being operated. The failure resulted in parts of the
disconnector falling to the ground and narrowly missing the Field Operator who was operating the device.
The Acelec type 06732 disconnectors are designed for operation at 88 kV and do not provide the required electrical
clearances for compliant operation at 110 kV.
Essantee disconnectors
The Essantee disconnectors are in very poor condition and need to be replaced. The units are susceptible to thermal
failure of the conductive braids. The disconnectors have also experienced failures of the operating linkage, preventing
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