Grounding Riddle No.36 – Grounding Transformers

The zigzag connection is a three-phase connection and is constructed as shown in Figure below. There are three pairs of windings, each having a 1:1 turns ratio. The left-hand set of windings shown in the figure is a conventional Y connection, a?-b?-c?, with the neutral N brought out. The open ends of the Y are electrically connected to the right-hand set of windings as follows: a?connects to the right-hand winding paired with to the b?-N winding, b?connects to the right-hand winding paired to c?-N winding, and c?connects to the right-hand winding paired to the a?-N winding. The opposite ends of the right-hand windings are brought out as the phase terminals a, b, and c. If three currents, equal in magnitude and phase, are applied to the three terminals, the ampere-turns of the a?-N winding cancel the ampere-turns of the c?- c winding, the ampere-turns of the b?-N winding cancel the ampere turns of the a?-a winding, and the ampere-turns of the c?-N winding cancel the ampere turns of the b?-b winding. Therefore, the transformer allows the three in-phase currents to easily flow to neutral. If three currents, equal in magnitude but 120

Ok, it seems the mentioned zero sequence current is grounding transformer no load current and must not mistake with fault zero sequence current. Indeed you can write: 1244 = 3R₀.(266.7/2)² R₀=0.023 Ohm

Sorry,thanks a lot for your good comment, indeed it should be 3 not 2, because we can write: I_n= 3 x I₀