Harmonic detection and filtering - Schneider Electric

3.2 Procedure for harmonic analysis of adistribution systemMeasurements are carried out on industrial and commercial sites as a:b preventive measure:v to obtain an overall assessment of the extent of the problem (map of thedistribution system)b remedial measure:v to determine the origin of a disturbance and devise solutions to correct theproblemv to check that the solutions implemented actually produced the desiredeffect.Operating modeVoltage and current measurements must be carried out:b at the power sourceb on the incoming busbars of the main distribution switchboardb on each of the outgoers leaving the main distribution switchboard.When the measurements are carried out, it is necessary to have precise informationon the conditions, in particular the status of capacitor banks (ON or OFF, number ofstages connected).On the basis of analysis results, it may be necessary to:b derate any future equipment installedorb quantify the protection and harmonic-filtering solutions that must be installedb compare the values measured to the reference values of the utility (harmonicdistortionlimits, acceptable values, reference values).Use of measurement devicesThe devices show both the instantaneous effects and the long-term effects ofharmonics.Correct analysis requires integrated values over time spans ranging from a fewseconds to a few minutes, for observation periods of a few days.The required values are:b the amplitude of voltage and current harmonicsb the individual harmonic distortion of each order, for both current and voltageb total harmonic distortion for both current and voltageb where applicable, the displacement between voltage and current harmonics of thesame order and the phase of the harmonics with respect to a common reference (thefundamental voltage, for example).17