Line measurement of positive, negative and zero sequence parameters of transmission lines with mutual inductance

Positive and negative-sequence usually are ignored only zero-sequence considered on line measurement of the parameters of transmission lines with mutual inductance. This is based on the assumption that distance between phases is much less than the distance between lines. However, for multi-circuits lines on the same tower with strong electromagnetic coupling, the assumption conditions are not met. In this paper the existence of positive, negative and zero-sequence (PNZS) mutual impedance is proposed in the case that distance between phases is not less than distance between lines. For the first time, the method to calculate the PNZS mutual inductance is studied based on electromagnetic theory. The results of a practical example indicate that positive and negative-sequence affect the line measurement of transmission lines with mutual impedance parameters positively, but the influence is small, and they can be neglected in most cases. So the research provides fundamental basis on engineering application.