Energy
Energy audit reveals efficiency lessons from underground mine
A recent energy audit at an Indian underground coal mine highlights critical lessons in managing power factors, contract demand, and electrical efficiency for heavy industrial users.
Key points
- Power factor drops below 0.90 triggered financial penalties at the Khairaha Underground mine.
- Exceeding contract demand limits resulted in higher billing rates due to grid strain.
- Distribution transformers operated most efficiently within a 40 to 60 per cent load range.
ESI Africa reported that a detailed energy audit at the Khairaha Underground mine in Sohagpur, India, has uncovered significant insights into managing electrical systems for heavy industrial machinery. Continuous Miner machines at the facility can consume over 91,000 kWh monthly, making power management a critical operational factor.
Managing power quality and demand
The audit examined how power factors and contract demand impact industrial overheads. When the mine's power factor fell to 0.892 in November 2022, it incurred a one per cent cost penalty, whereas a power factor of 0.953 in July 2022 earned a rebate. Additionally, the facility regularly exceeded its 2,350 kVA contract demand, peaking at 2,900 kVA in June 2022, which triggered higher billing rates for exceeding threshold limits.
Equipment efficiency and diagnostics
Researchers found that the mine's large distribution transformers achieved peak efficiency when operating between 40 per cent and 60 per cent load. Advanced diagnostic tools also identified elevated current harmonic distortion in specific circuits, such as a lighting transformer and a main switch feeder, while thermal imaging showed no abnormal component heating. To address these inefficiencies, the study recommended installing an Automatic Power Factor Controller to stabilise power factors and filter harmonic pollution.
Original reporting
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