Calculation problems for double-circuit transmission lines sharing the same tower
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For lines with dual circuits on the same tower (where there are dual circuits on each tower from the first tower to the last), all parameters are the same; should such a line be counted as one line or two lines?
Of course it’s a two-wire circuit. When considering the parameters, the positive-sequence mutual inductance can be ignored as it is small, while for the zero-sequence impedance, the mutual inductance must be taken into account as it has a significant impact. If measured in practice, grounding and not grounding both ends of the other circuit also has a significant impact on the circuit. To replicate actual conditions, measuring the zero-sequence mutual inductance is more accurate when both ends of the other circuit are not grounded.