Study of protection scheme for transmission line based on wavelet transient energy

Wavelet transient energy is proposed to be the criterion of protection for distinguishing internal or external fault on transmission line in this paper. The modal voltage and current are decomposed by Daubechies 4 wavelet in both time and frequency. The different decomposition coefficients on different scales reflecting different frequency information are used to calculate the transient characteristic of voltage and current. The transient characteristic is then utilized to obtain the transient energy of the fault that is employed to identify the fault position. Simulation results show that the proposed protection scheme based on transient energy is applicable and encouraging. It is independent of fault type, switching angle and generation mode; not influenced by recloser and lightning surge. Single-line ground fault with high fault resistance can also be detected correctly. The proposed protection scheme has good selectivity, reliability and sensitivity.