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3 Acceptable limits, recommendations and standards3.1 General limitsc synchronous machines: permissible statorcurrent distortion = 1.3 to 1.4%;c asynchronous machines: permissible statorcurrent distortion = 1.5 to 3.5%;c cables: permissible core-shielding voltagedistortion = 10%;c power capacitors: current distortion = 83%,corresponding to an overload of 30% (1.3 times therated current); overvoltages can reach up to 10%;c sensitive electronics: 5% voltage distortion witha maximum individual harmonic percentage of3% depending on the equipment.3.2 Standardised limitsThe series of standards (IEC 61000) forelectromagnetic compatibility define certain limitsconcerning harmonics, mainly:c IEC 61000-3-2 which define the limits ofharmonic emissions for equipment consuming lessthan 16 A per phase (except for certain categoryof equipment indicated in the standards).The case of equipment consuming over 16 A perphase is examined in the technical spec. IEC/TS61000-3-4 and should finally be determined bythe projected standards IEC 61000-3-12.c IEC 61000-2-2 which defines compatibilitylevels for harmonic voltages in public LV powersupply systems (see fig.4 ).c IEC 61000-2-4 which defines compatibilitylevels in industrial networks.We would remind that compatibility level doesnot define an absolute limit. There remains someprobability to be slightly beyond the fixed level.Another standard, EN 50160, gives thecharacteristics of voltage supplied by a utilitynetwork.In France, EDF proposes a contract for largeconsumers called "Emeraude" which consists ina reciprocal commitment: a quality commitmentby EDF against limitation of pollution due to theconsumer.Odd harmonics Odd harmonics Even harmonicsnon multiples of 3 multiples of 3Harmonic Harmonic Harmonic Harmonic Harmonic Harmonicorder voltage order voltage order voltagen % n % n %5 6 3 5 2 27 5 9 1.5 4 111 3.5 15 0.3 6 0.513 3 21 0.2 8 0.517 2 >21 0.2 10 0.519 1.5 12 0.223 1.5 >12 0.225 1.5>25 0.2+0.5x25/nFig. 4 : compatibility level for individual harmonic voltages in low voltage distribution networks (IEC 61000-2-2).Cahier Technique Schneider Electric no. 152 / p.8