In August 2016 BHP, BHP set up a temporary power station at its Yandi mine site to provide power during a scheduled outage. Power Engineering Services engaged Aptus Power to test the performance of the earthing system at this temporary power station.
Aptus Power successfully conducted the following test as part of this review:
- Earthing system impedance
- Touch and step voltages
- Voltage contours
- Transferred voltage hazards
- Equipment continuity checks
All equipment earth bonds were adequately connected to the earthing system. Aptus Power identified a storage container that was sitting off the earthing system while having an earth connection. Due to this arrangement a high touch voltage onto the container was present and exceeded the tolerable touch voltage limit for a natural surface. Aptus Power recommended crushed rock to be installed around the container to mitigate this specific hazard. Crushed Rock (or Blue Metal) is a high resistivity layer which results in lower currents flowing through the body when a human comes in contact with a live object under fault conditions. In this case the crushed rock was sufficiently lifted the tolerable touch voltage limit above the measured touch voltage making it safe for human contact.