Second zero-sequence mode

In Table 1.6, the first kind of distribution corresponds to the so-called zero-sequence mode and is mode 0 in the same polarity case and mode 3 in the opposite polarity case. If the line is single circuit, there is no opposite polarity mode, and the first kind of distribution is the same as mode 0 distribution, which was explained in Section I.4.4.I. Mode 0 is often called the first zero-sequence mode (earth-return mode), and mode 3 is called the second zero-sequence mode (intercircuit zero-sequence mode). 

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