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V (V & %)I (A)35011 %823 5 7 9 11 13 HFig. 28 : harmonic voltage spectrum of a5.5 kV network equipped with a capacitorbank alone.3 5 7 9 11 13 HFig. 29 : spectrum of the harmonic currents flowing inthe capacitors for a network equipped with a capacitorbank alone.8.2 Reactor-connected capacitor bankThis equipment is arbitrarily tuned to 4.8 f 1 .Harmonic impedance (see fig. 30 )The network harmonic impedance curve, seenfrom the node where the harmonic currents areinjected, exhibits a maximum of 16 ohms (antiresonance)in the vicinity of harmonic order 4.25.The low impedance, of an inductive character, ofthe 5 th harmonic favours the filtering of the 5 thharmonic quantities.Voltage distorsion (see fig. 31 )For the 5.5 kV network, the individual harmonicvoltage ratios of 1.58% (7 th harmonic), 1.5%(11 th harmonic) and 1.4% (13 th harmonic) maybe too high for certain sensitive loads. Howeverin many cases the total harmonic voltagedistortion of 2.63% is acceptable.For the 20 kV network, the total harmonicdistortion is only 0.35%, an acceptable value forthe distribution utility.Z (Ω)Capacitor current load (cf. fig. 32 )The total rms current load of the capacitors,including the harmonic currents, is 1.06 times thecurrent rating, i.e. less than the maximum of 1.3.This is the major advantage of rea ctorconnectedcapacitors compared to the firstsolution (capacitors alone).V (V & %)190.6 %501.58 %481.5 %451.4 %3 5 7 9 11 13 HFig. 31 : harmonic voltage spectrum of a 5.5 kVnetwork equipped with reactor-connected capacitors.15.6I (A & %)3424 %~ 4.254.8H35 7 9 11 13 HFig. 30 : harmonic impedance seen from the nodewhere the harmonic currents are injected in a networkequipped with reator-connected capacitors.Fig. 32 : spectrum of the harmonic currents flowing inthe capacitors for a network equipped with reactorconnectedcapacitors.Cahier Technique Schneider Electric no. 152 / p.23