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Process Reliability

When this gold mine operator contacted AEE, gold production was punctuated by unexplained Motor Control Centre outages in the processing plant.

After visiting the facility and meeting the electrical staff, AEE developed the following remediation work package for application in each of the plant’s substations:

  • Identify and re-programme all motor protection relays in which the earth fault elements had been inadvertently disabled several years earlier,
  • On all LV feeder circuits rated at 100 Amps or more, install earth fault protection in one of the following forms:
    • A replacement MCCB with integral earth fault protection, or
    • A standalone earth leakage relay supplied by a core balance CT.
  • On sump pump feeders and other circuits deemed to have a high electric shock risk, install earth leakage protection schemes with target trip values of 30 mA sensitivity and instantaneous speed of operation.
  • On 4,000 Amp MCC incomer circuits, replace the existing unreliable stand by earth fault protection schemes supplied by measuring class CTs with IEC60255 compliant relays supplied by protection class CTs.

AEE took responsibility for the design and procurement, supervised installation and commissioned the new work. The resulting improvement in substation reliability has been proof of the efficacy of AEE’s solutions.

AEE provided other services to this client including:

  • an arc flash hazard analysis at the power stations, process plant and other parts of the mine infrastructure,
  • short circuit studies for new distribution substations,
  • replacement ACB settings,
  • load flow studies for new underground mine developments,
  • a relay replacement project on the tie transformer linking the main and back up power stations,
  • stability studies for the avoidance of pole slipping between generators at the main power station and generators at the back up power station