Hi again, Can/are zig zag connections used on the secondary side to avoid triplen harmonics flowing further up the power system? Lets say 3rd harmonics are flowing up the power system from some loads connected to phases a,b,c and the neutral. Since 3rd harmonic are all in phase, the ampere-turn created will cancel in a zig zag connection and thus not couple to the primary and further up the power system? This pdf: http://static.schneider-electric.us...ansformers/Harmonic Mitigating/7400DB0301.pdf says on page 12 and 13: "With all of the triplen harmonics in phase with each other, by vector analysis, the triplen harmonic currents produce ampere-turn fluxes that cancel each other such that no currents are induced in the primary winding. For this to work, the triplen harmonics must be real currents and not mere mathematical identities derived by the Fourier Transformation." The last sentence in bold kind of confuses me.