RECENT PROJECTS - NEWLANDS COAL MINE (North Queensland).
The Newlands Coal Mine invited AVS to sample 50 pole structures to determine the serviceability of their oldest 200 pole assets.
The Newlands mine has approximately 1200 wood poles with voltages ranging from 66 kV to 11 kV. These pole based assets are up to 24 years old. They are visually inspected annually, however, due to changes in mine ownership, ground-line inspection records have not been accurately maintained. The mine has had one pole failure in the last twelve months. The management of Newland's electrical assets were keen to assess the condition and risk of their asset. To that end, Newlands Coal invited AVS to evaluate twenty-five percent of their main 66 kV pole structures servicing the Newlands coal mine.
For this project we have used limit state design methodology to evaluate the structures with NZS/AU Standard 4676 (2000) "Structural Design Requirements for Utility Service Poles" [1] and ESAA/AU HB C(b) 1 (1999) [2]: "Guidelines for design and maintenance of overhead distribution and transmission lines".
Structures were assessed using the
ground-line scanning technique to determine the residual strength at ground
line. The residual strength was determined as a percentage of the structures
original strength given the structures strength group and size attributes. Then
the structures were assessed using a 'serviceability index' calculation with
consideration to the structure's load profile. In this project we calculated
the 'serviceability index' for all poles.
In our assessment it is critical that all load and structure information is associated with a directional bearing. These bearings are based on along-line and across-line coordinates from 0 - 360 degrees. To assess the applicable load of a structure we measure the following attributes:
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Given the number of assets servicing the mine an initial total assessment would have taken an estimated six (6) man months. It was a priority that Newlands management was able to determine the risk associated with these assets. To that end, we recommended a statistically random sample of twenty percent (50 poles) of the mine's oldest poles be targeted for assessment and analysis. This initiative was initially more expensive than a unit rate for total assessment, however, it expedites the process of risk evaluation.
Project outputs and benefits.
The outputs of this project included, but were not be limited to:
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The immediate tangible benefits for mine management were:
Termite activity can be identified at the time of inspection. AVS is able to identify accelerated deterioration when a structures decay rate is compared to the mine's average annual decay rate. There were a couple of structures that had accelerated decay rates. One pole, for example, was only a few years old and the annual deterioration rate was 3.2% verses the average of 0.68%. This would not have been identified by other inspection processes. It was erect to replace a pole that failed due to termite attack. Unfortunately this new pole was erected next to the old pole and old butt left in the ground. You can imaging the joy when the termites realised that someone had erected a new home for them after their old home was demolished. AVS was able to identify the poles with termite activity and recommend an appropriate strategy.
AVS continues to work with the Newland
Mine. Tony Cervai, the Elecrtrical Manager was extremely happy with the project
results and for a reference can be contacted on (07) 49405264.
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