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Keeping track of power quality

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Power quality is not a problem to be shirked, says Brendan Beaver, UK manager of Metrel, supplier of electrical test solutions.

With the increased complexity of the network, we are all having to pay more attention to the quality of power the distribution companies deliver to our installations and the effect that our installations have on their supply.

Distributed generation and the widespread use of electric motors, etc, are all adding to the distortion of what used to be a simple sine wave. And with this, sensitive electronic equipment, such as variable speed drive motors, can malfunction or even lock up. Even lighting can be noticeably affected.

A number of companies sell a range of power quality analysers and loggers. Indeed, Metrel offers a line of Class S to Class A power quality analysers and loggers, which are immensely capable and modestly priced, for those who have who wish to invest in stand-alone equipment to make specialist studies of facilities.

However Metrel’s versions of the installation multi-function tester, MI3155 and MI3152, offer installers and engineers a cost-effective alternative for basic power analysis. Not as powerful as the standalone instruments, both these testers are capable of measuring total harmonic distortion (THD) for voltage and current to the 12th harmonic. They can both measure active power (P), reactive power (Q), apparent power (S) and power factor (PF). The results can be quickly and easily committed to the tester’s on-board memory for future reference. All very usable as a baseline measurement for future trouble-shooting and to confirm the installation is not affecting the network negatively.

An added bonus for the engineer who is not habitually doing power quality studies; both testers have clearly readable help screens, to serve as a reminder of the connections that are required to do the measurements.

When you hear things like 3-phase motors can draw significantly more energy than specified from the network if there is a voltage imbalance, the extra energy means unnecessary heating and that could lead to damage of the motor and even more cost; it makes you think.

Given our preoccupation, these days, with energy efficiency, an installation tester with power quality capabilities, for a similar price as an ordinary tester, seems a wise investment.


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