Electrical Flicker in a Rock Quarry

THe Situation and Problem

A rock quarry is located in a rural area where the medium voltage (12.5kV) utility electrical supply to the quarry also feeds a number of local residential communities. The quarry installed two large rock crushing machines and following their installation, the residents of the local communities complained to their electrical utility that they were experiencing significant power quality issues including the premature failure of some electric and electronic equipment.

THe Analysis and Diagnosis

The utility installed power quality monitoring equipment and determined that there were neighborhood power fluctuations and electrical flicker which they traced back to the quarry. When starting the rock crushers at the start of a work shift there would be a requirement for reactive power (kVAR) input that exceeded the capacity of the utility supply, resulting in a voltage sag on the network. This could also happen occasionally during the day if large rocks were being crushed or if both rock crushers came under peak load simultaneously. Wide variations in load resulted in the creation of electrical flicker

THe Solution

Omniverter supplied two outdoor Power Flow Lite (PFC) units which provide the needed kVAR’s with a power electronic solution that does not use any large capacitors. The PFC’s automatically detect any power fluctuations and respond within less than a cycle to provide the needed reactive power. They also continuously monitor and correct power factor despite large power variations. The outdoor houses are located inside the quarry in very dusty conditions. They have to withstand wide variations in temperature, so they are insulated steel structures with integral heating and air conditioning to provide clean air for the electrical equipment.

THe Impact and ROI

The utility has stated that the installation has been very successful. They continue to monitor power quality and the neighborhood residents have ceased to complain about their power quality. An alternative solution for the utility would have included a new medium voltage supply line over several miles which would have cost many times the cost of the PFC solution.

Do you have an unusual power quality problem? Is your electrical utility complaining about Your plant affecting their system.

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