Case Studies
BHP Olympic Dam – Roxby Downs, South Australia
Safearth are currently undergoing thorough earthing system baseline testing spanning across the entire BHP Olympic Dam operations. So far, this has included processing or metallurgical plant HV assets, as well as mine surface and mine underground HV assets. Planning is also underway to assess HV assets as part of the network for the Roxby Downs township.
The Challenge
Safearth has a long-standing relationship with mining giant BHP, specifically at their WA and NSW-based operations. During this time, Safearth have developed Earthing System Management Plans (ESMP) to assist with managing and monitoring the complex earthing arrangements that often make up a mine’s electrical network. When BHP Olympic Dam approached us for earthing testing of their vast network, we were excited for the opportunity to kick-start an ESMP with them, but also provide earthing system baseline testing (ESBT) and training courses tailored to their needs. BHP are starting to adopt the Safearth ESMP across all its operations.
The Solution
To kick start the ESMP and ESBT, Safearth conducted a weeklong site visit, visiting assets across the metallurgical (processing) and mine surface and mine underground areas. Assets visited included the main incoming supply 275/132/11kV switchyard, an electrorefining substation part of the copper production process, and a raised bore fan and substation that assists with ventilation and supply to the underground mine.
At select assets, Safearth conducted visual inspections, loop impedance testing, DC continuity integrity testing and current injection performance testing.
What happened next?
During this site visit, BHP site personnel discussed results from recent routine loop impedance testing conducted by BHP. Safearth were asked whether the results meant remediation was required, as ohmic targets were defined and the results were higher than these targets. Safearth began to conduct loop impedance testing of their own via an AEMC 6146 and discovered their measurements were below these ohmic targets.
Should BHP switch to the AEMC? Or should a form of remediation be carried out?
Upon further investigation, Safearth determined that depending on the brand of meter, the frequency at which the measurements were recorded can create differing results. Refer to the image below.
What should BHP do? In short, the advice provided was that regardless of the brand utilised to conduct the loop impedance testing, rather than set an ohmic target to determine if remediation is required, utilise the results to monitor condition over time. If the numbers start deviating from the previously tested results, open the investigation further.
This is just one example of how Safearth go above and beyond for their clients.
Extra information from an interview with Safearth’s Consulting Engineer Riley Blackwell:
How long did the project take?
A lot of time goes into working at a site like Olympic Dam due to the hazardous environment (chemicals, processes, machinery, forklifts!) and multiple different work groups across processing and the mine end. As such, before stepping foot onsite, Safearth personnel are required to complete one day of online inductions, half a day onsite of classroom inductions and orientation and weeks of planning and discussion. Once approved, Safearth typically spend 5-6 days onsite to test ~3 to 4 asset areas at a time (which by the end of it is about 15-20 substations/transformers/switchrooms).
Which Safearth equipment did you use onsite?
Safearth utilise their full suite of test equipment and test gear, including CS3 DC Continuity Meter and AX1 Current Injection Amplifier and MI3 Tunable Multi Meter. Other branded equipment includes AEMC Clamp on Tong Loop Impedance and Megger’s Det 2/3 Soil Resistivity Tester.
Did you work with other companies on this project? Did this create complexities or new learning experiences?
No different companies for each project, but each site visit has meant different work groups at BHP. Whilst each planner had a different way of doing things, ultimately, each site visit has been successfully planned and executed – credit to BHP for this.
Was this project complex, unusual, technically different, was access difficult, more staff needed, remote location?
For such a complex site, you would think this entails complex testing methods and strategies. Quite the opposite, as the HV earthing system performance for individual assets is driven more by the upstream/downstream connections to the plant/structures rather than the local buried earth grid.
Furthermore, accessing different areas at first glance can be difficult at a site such as this due to different work groups, hazards or restrictions. As such, thorough planning and ongoing discussions with BHP planners and especially the site crew have been vital to ensuring the safety of Safearth personnel and to ensure valid results can be achieved for BHP right across the site.
By Riley Blackwell, Consulting Engineer – Safearth
If you need expertise and advice from the world-recognised earthing system experts, we’d love to assist you in your earthing and lightning protection ventures. We’ll be with you every step of the way. Contact Safearth today!