• • • RENEWABLE TECHNOLOGY • • •
Six ways to cut facility costs by measuring power quality
It is widely known how power quality measurements carried out on motors and drives can improve the efficiency of electrical systems and keep costs as low as possible. However, there are several hidden issues relating to energy usage within facilities that can incur significant additional costs while also causing equipment damage and disruptive downtime, says Markus Bakker, field application engineer, at Fluke Corporation
B
y focusing on the following six specific power quality measurement areas, it’s possible to unveil these hidden issues
and cut costs while also improving overall facility performance.
Unbalance With a balanced, three-phase system, the phase voltages and currents need to be either equal or extremely close in terms of amplitude and phase. Any unbalance in these areas can lead to diminished performance levels or even premature failure. Poor motor performance occurs because of anti-torque and premature motor failure because unbalance causes excessive heating of coil wires. The biggest costs that can be incurred relate to
motor replacement and lost income caused by circuit protection trips, as well as the associated downtime and labour costs to fix the problem. But
unbalance also affects energy costs as they reduce motor performance. One of the best ways of identifying voltage
unbalance issues in advance is to look at the voltage that is measured at the connection to the public electricity network (service entrance). Under the EN50160 power quality standard, voltage unbalance, as a ratio of negative to positive sequence components, must be less than 2% at the point of common coupling. If the voltage is not well balanced at the service entrance, the power in the entire facility is unbalanced and must be fixed as soon as possible by the distribution network operator. Unbalance can be present at one single load
only, or a branch in the internal electric infrastructure, for example an electric motor or even an array of motors. So it’s good practice to check the input voltage and input current on the
34 ELECTRICAL ENGINEERING • NOVEMBER 2022
understanding that the unbalance of these two parameters should not exceed 2% and 6% respectively. Current unbalance is a direct consequence of voltage unbalance, and if the voltage is balanced, then current unbalance is caused by and unbalance in the loads.
Total harmonic distortion Measuring total harmonic distortion (THD) identifies how much of the distortion of voltage or current is due to harmonics in the signal. While it is normal to have some current distortion, anything over 5% on any phase warrants further investigation. If this level of distortion is not dealt with, it can
cause such issues as high current flowing into neutral conductors, motors and transformers running hot (which shortens insulation life), poor transformer efficiency (or the need to use a larger
electricalengineeringmagazine.co.uk
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