Voltage Sag Case Study – Pharmaceutical Company

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This is a synopsis of power quality case study regarding the phenomenon of Voltage Sag experienced at a pharma plant. A pharmaceutical company site in Dublin had been experiencing some critical sags at their incoming supply.

Read more about the power quality issues faced, and learn what solutions were offered by Powerpoint Engineering Ltd.


A pharmaceutical company based in Dublin had two power quality analyzers (Unipower UP2210) installed on the LV side of their two 10kV Main Incoming Supplies. The site had been experiencing some critical sags at their incoming supply. The supply authority had advised that they had experienced no issues on their supply that matched up with the occurring power quality events on site.

The Unipower PQ Secure Software for the installed analyzers yielded conflicting reports. Supply #1 indicated that the incoming supply was the origin of the Voltage Sag, whilst supply #2 indicated that the voltage sag was actually being caused by the connected load at the plant.


After consultation with Powerpoint Engineering, it was advised that the conflicting PQ Secure reports  were possibly accurate. It was suggested that there was a large connected load which was generating large inrush currents causing the voltage supply to sag. The supply to this load was being disturbed and the connected power quality analyzer recognised the direction of the voltage sag event – i.e. from the load.

The voltage sag was so severe that it was causing the high voltage supply to be affected, and therefore affecting also the other supply . The plant had also purchased a portable Power Quality Analyzer (Unipower Unilyzer 901). This portable power quality analyser is used to identify the source of this recurring sag event.

Remedial action was taken on the connected equipment, and good power quality was restored to the plant.

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