While responsibility of power quality lies with all three, grid company, equipment mfr and consumer, precise and standard measurements correlate all..

Power systems essentially involve three stakeholders, grid company that builds, owns and operates networks (could be different if owner, supply and operator are separate companies, as it is in some developed markets), consumers or industrial establishments who use electricity supplied through the network and equipment manufacturers who make the equipment which are used by consumers or industrial establishment.

If there is any network asset or equipment that gets damaged or stops operation in the network, industrial facility or consumer premises, it could be either due supply company issue e.g. network is so weak that whenever a big load in a neighboring industrial facility starts, it leads to a voltage dip in the area impacting all equipment's in the vicinity, it could be due to an industrial consumer who draws excessive harmonic current from the network and thereby distorts bus voltage and troubles all other customers connected to the bus and impacts intervening network assets also or it could also be that equipment that got damaged or stopped working was not compatible to work in the environment that it was installed or did not meet immunity as prescribed in its guiding standards.

So, there are at least three measurements involved, supply quality, equipment immunity and disturbance that consumer feeds and power quality measurement in all these three have to be "consistent, using same method that can be correlated" in the sense that equipment immunity is better than what is promised by supply network or disturbance that consumer may feed in network is less than what may cause any issue to either network equipment's or to any other consumer connected to PCC and supply company gives supply that meets specific quality attributes.

Extending the point, it's essentially about measurement, either about supply quality or equipment immunity or measure of disturbance that any consumer might be feeding into the network and "methods that are used". These are very different from general measurements and so measurement methods are much more precisely defined and results are sensitive to the methods adapted e.g. for harmonic measurement for up to 2 kHz, IEC 61000-4-7 specifies 10 cycles gap less, not even 200 ms (frequency is hardly ever exact 50 Hz!!) so that sampling starts at zero crossing and ends at zero crossing with a specific shape of sampling window, calculation periodicity as small as half cycle for sag/ swell evaluation, aggregation periods of 10 cycles and so on. These precise measurement methods are defined in standards e.g. IEC 61000-4-30 class A, IEC 61000-4-7 and these form a common thread whether we talk about compliance assessment for grid company, so these are referred in standard like EN 50160, whether we talk about compliance assessment of an industrial consumer, so these are referred in IEEE 519-2014 or whether we talk about equipment immunity. There are different measurement methods for higher order harmonic measurements in 2-9 kHz and beyond 9 kHz up to 150 kHz which are prescribed in informative annex of standards so for these ranges multiple methods maybe getting used by multiple instruments giving non-comparable results and even some radio interference standards like CISPR 16 which may not be practical for in-situ measurements.

So, next time when you have a set of power quality measurements data, be attentive to the measurement method that has been used, whether it is intended to be indicative in nature or something that's aligned to measurement standards and so can well be used for contractual purpose, compliance assessment and so on...

May please reach us for more information or discussions, we will be eager to attend, because better understanding on power quality is good for all and more so in the changed grid scenario where "everything is more and more electronics, so sensitive to power quality and at the same time may well be contributing to deteriorating power quality in the networks..."

#powerquality #standards #measurementmethods #distribution #transmission #powersystem #changedgridscenario