The impact of current harmonics on the power factor of a low voltage distribution system – A Case Study

In modern factories, capacitor banks are not the most effective solution for Power factor improvement !!

 

This study was carried out to identify and rectify, what initially seemed to be a malfunction of a power
factor correction capacitor panel (PFCCP) (Power factor improvement). However during the study it was identified that the problem was not due to a malfunction of the PFCCP, but due to the failure to identify the impact of the harmonics on the power factor, at the design stage. In this case study we will analyze the problem and try to find out a theoretical explanation comparing the data gathered at site.


Kekirawa water supply scheme has two 132kW pumps to pump the water from Yodha Ela to the water treatment plant. The two pumps are controlled by two Variable Speed Drives rated at 132 kW working in duty/standby basis.

There is a Motor Control Panel Board located inside the pump house consisted of the VSDs and other control and switch gear. There is a separate Main Incoming and Distribution Panel Board which supplies power to the Motor Control Panel and auxiliary power to the pump house.
Auxiliary power of the pump house consist of four florescent lights, two socket outlets, an overhead crane, indication bulbs and exhaust fans of the panel boards. As the crane is used only for a maintenance work of the pumps, and the lighting and socket outlet power is negligible comparing to the pump power, it is safe to assume that the total power consumption of the installation at any given moment is 132kW. Also this load is a nonlinear load supplied through a VSD.


There is a Power Factor Correction Capacitor Bank integrated in the Main Incoming and Distribution Panel. We were informed that the Power Factor Correction Capacitor Bank is not correcting the power factor as expected and it has not reduced the electricity bill.

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