Remote Mining Facility-REA Energy Case Study
REA Energy, a 5,000 member co-op headquartered in Indiana, Pennsylvania.
- Multiple coal mines located on a single circuit
- Customer flicker complaints
The two mining operations were located in the same area, approximately three miles apart. Each used continuous miners to push several AC motor-powered cutting heads into coal seams to remove material. Profitability is proportional to output, and miners push the cutters as close to locked rotor as possible before withdrawing them from the coal-face to regain speed.
For flicker mitigation purposes, each site was modeled as a series of independent motor loads. The large motors (powering cutter heads) were modeled as motor loads varying from idle to near locked rotor conditions. The other motors (conveyors equipped with reduced voltage soft-starters) were modeled as randomly-varying loads going from no load to full load. Steady state loads such as mine ventilation and pumping systems were ignored for flicker analysis, but were included for power flow, power factor, and harmonic analyses.
With one mine in-service, customer complaints began to increase. A second mining company requested service, and both companies had indicated plans to increase load. In addition, the REA had also received notice from a third mining operation that was planning to locate in the same area. All the mine operations would be served from the same 12.47 kV circuit fed from a 46 kV substation.
Considering how to address the flicker, the REA was aware that typically these small mines in Appalachia last three to fifteen years. Even if reconductoring the 12.47 kV line would yield acceptable flicker mitigation, it would also result in a permanent high ampacity upgrade to a circuit that would have a maximum use of only seven years.