Perform power quality audits of your factory... without any measurement equipment

Power quality is the bottom line of every efficient industrial process or commercial service. As productivity and operation costs depend on reliability and quality, power quality has become a strategic issue for the operating, maintenance and management departments of every industrial or commercial site. Nevertheless, power quality relies not only on your energy distributor but also on your own distribution network and characteristics of your equipments. Measuring and controlling are therefore two key elements of optimal electric distribution system and preventive maintenance. Power quality measurement requires measure equipments, time and skills. As these three elements are seldom to be gathered, distribution network are usually not enough controlled. Apparently regular disturbances such as flicker, motors shut down, or triggering of protection equipment, might actually reveal the existence of more important electrical disturbances, with risks of loss of production or data, pre-ageing and overheating of equipment, or even equipment damage. Before asking for an outside help, which might cost you a lot of money, you should learn to identify symptoms - they might lead you to the possible origins of power quality disturbances:

• Random process equipment shut down is usually related to voltage dips or atmospheric surges.
• Process shut down may indicate atmospheric surges, harmonics, power interruptions or HF spikes.
• Equipment damages are related to atmospheric surges, harmonics, inter-harmonics, HF spikes, continuous component or three-phase unbalance.
• Overheating and noise from equipment are usually symptoms of voltage dips, over voltage, harmonics, inter-harmonics, or zero sequence harmonics.
• Flickering of lighting indicates either flicker disturbances (rapid voltage fluctuations) or short power shut down.
• Motors disturbances (e.g. inverse motor torque or abnormal noise and vibrations) are typical symptoms of unbalanced phase, voltage dips, harmonics, or frequency fluctuations. Motors shut down might indicate the existence of a continuous component.
• Unaccountable tripping of protection systems is typically related to continuous component.
• Triggering of arcs are consequences of atmospheric surges, zero sequence harmonics, long voltage interruptions, HF spikes or EMC.

Thus, you can learn a lot of your distribution network quality simply by paying more attention to your equipments operation. Once electrical disturbances possible origins have been identified, their cause needs to be treated. This point will be covered in a new coming SE Blog post. For further information, please report to Schneider Electrics “Cahier technique” n°199, Power Quality and GIMELEC publications.