Research on travelling wave transmission characteristics in distribution network

The impacts of mixed line, distribution transformer and multi-branch lines on travelling wave transmission characteristics are analyzed quantitatively. When fault travelling wave signal arrives at the mixed-line interface, complex reflection and refraction occurs. And its influences on travelling wave detection are studied. Mathematical model of distribution transformer is built. Actual transformer parameters are used to calculate its cut-off frequency. The transfer characteristics that distribution transformer transfers fault travelling wave head are studied. The effects of multi-branch lines on reflection and refraction are analyzed. The amplitude of voltage and current travelling wave is in relationship with the number and wave impedance of lines, and it is analyzed quantitatively in the paper. In the last, by using the EMTP simulation software, the model is built to verify the correctness of the described conclusions. The theory provides a strong theoretical support for accurate detection of travelling wave in the distribution network, as well as travelling wave protection and fault travelling wave location.