The invention provides an asymmetric
power transmission line parameter on-line measuring method. The method includes following steps: step 1, synchronous measuring apparatuses are arranged at two ends of a measured line,
voltage and current signals at two ends of the measured line are measured in a synchronous manner via the synchronous measuring apparatuses, and m (m>=2) different measurements are performed; step 2,
Fourier transform of m groups of
voltage and current signals at two ends of the measured line obtained by step 1 is performed, m groups of
power frequency voltage phasors and current phasors at two ends of the measured line are calculated, and the phasors comprise voltage and current phasors at head terminals of the measured line from the first group to the mth group and
voltage phasors and current phasors of bottom terminals; step 3, self admittances Ya, Yb, and Yc of A, B, and C phases of the measured line and mutual admittances Yab, Ybc, and Yac of each phase are calculated; and step 4, self impedances Za, Zb, and Zc of the A, B, and C phases of the measured line and mutual impedances Zab and Zbc of each phase are calculated. According to the method, parameters of the
self impedance and the self
admittance of each phase and parameters of the mutual impedances and the mutual admittances between the phases, parameters of positive-sequence and zero-sequence impedances and admittances, and parameters of sequence
coupling impedances and admittances between sequences can be calculated.