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

0BInvestment Evaluation Summary
TNM-GS-809-0720
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).
4.3.1 ACELEC TYPE HDB5L
The Acelec disconnectors are in 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 need to be locally manufactured or salvaged from
decommissioned units.
The current rating of the type HDB5L disconnectors is 800 Amps, resulting in disconnectors D129, E129 and K129 at
Creek Road Substation being circuit limiting equipment, however this limitation currently does not constrain the
associated transmission circuits.
4.3.2 ESSANTEE TYPE 05552
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
the disconnector from operating; seizing of pivot joints, preventing contacts and disconnector from closing; and contact
misalignment due to weakened springs and worn pivot joint assemblies.
The Essantee disconnectors are designed for operation at 88 kV and do not provide the required electrical clearances for
compliant operation at 110 kV.
4.3.3 STANGER TYPE TTT
The Stanger disconnectors are in poor condition and need to be replaced. The units are an obsolete design, do not have
available spare parts and have exceeded their assigned service life.
4.3.4 TAPLIN TYPE D751
The Taplin disconnector A429 at Creek Road Substation is in acceptable condition. However, the unit is mounted on a
girder approximately 10 metres above ground level and requires additional resource effort to maintain. The unit will be
retained for spares.
4.4 VOLTAGE TRANSFORMERS
The 110 kV voltage transformers installed at Creek Road Substation comprises the following types:
� Balteau type UEV110 - three units (average age of 29 years); and
� Trench type 123/3 units - 18 units (average age of 9 years).
In 2000, a number of 110 kV voltage transformers (Brown Boveri TMZF and Asea Type EMFA) that were in extremely
poor condition were replaced to eliminate the likelihood of explosive failure and to sustain the performance of the
substation prior to the redevelopment of Creek Road Substation 110 kV. The replacement units were manufactured by
Trench and are in acceptable condition. The units will be assessed for their suitability for redeployment elsewhere in the
transmission network following their decommissioning as part of the redevelopment project.
The Balteau 110 kV voltage transformers are of an obsolete design and are in poor electrical condition. They have high
percentage power factor readings, which indicate excessive moisture in the insulating oil and likely degradation of the
winding insulation. 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 Voltage Transformer Asset Management Plan (TNM-PL-809-00614) recommends that the units should be
progressively replaced over the next five years.
© Transend Networks Pty Ltd 6 of 17