Method for measuring inter-phase mutual capacitances of long-distance extra-high voltage double-circuit lines on same tower

The invention discloses a method for measuring inter-phase mutual capacitances of long-distance extra-high voltage double-circuit lines on a same tower. The method is suitable for measuring the inter-phase mutual capacitances of the double power transmission lines on the same tower at the frequency of 50 Hz, wherein the distance between the power transmission lines is more than 240 kilometers, and the method is also suitable for measuring the inter-phase mutual capacitances of the short-distance lines. The method includes the steps that firstly, inter-phase mutual capacitance values at two frequencies are acquired, wherein up-down absolute error values of the two frequencies are equal with the frequency of 50Hz as the midpoint; the two inter-phase mutual capacitance values are added and then are divided by two, and then the inter-phase mutual capacitance mean value at the two frequencies is obtained, wherein the mean value is the inter-phase mutual capacitance at the frequency of 50 Hz. Compared with the prior art, the method has the following advantages that a traditional measurement method is changed, the influence of the lines on ground capacitances and interference of power frequency are taken into account in the wiring mode and algorithms, errors of the inter-phase capacitances measured through the method are reduced especially in the long-distance power transmission lines, and the engineering requirement is met.