Subject of research: methods for selective determination of an outgoing line with a single-phase earth fault based on the relative measurement of higher harmonics. Purpose of research: to develop a method for software filtering of high-frequency components and a method for identifying a line with a single-phase ground fault. Object of research: distribution networks 6-35 kV. Methods of research: wavelet-transformation of zero-sequence currents and voltages. Main results of research: the article proposes the idea of using the wavelet transform to organize software filtering of the zero-sequence current in order to increase the sensitivity of the admittance protection. On the basis of the wavelet transform, a modernization of the algorithm for determining a power line with a single-phase earth fault is proposed according to the principle of relative measurement of the energy of the spectrum of higher harmonics. The paper proposes to determine the energy of the spectrum by the wavelet coefficients of the discrete wavelet transform.