Traveling wave protection based on asynchronously sampled time difference of arrival of modulus traveling waves in per unit line length

Traditional traveling wave protection schemes are susceptible to many factors such as network topology change, environment interference and inaccurate identification of wave fronts, which may lead to mal-operation of protection. In addition, most traveling wave protection schemes need accurate synchronous measurement which adds to the implementation cost. This paper proposes a traveling wave protection for high voltage power grids based on the time difference of arrival (TDOA) of zero-mode and aerial-mode traveling wave. First, the time difference of arrival of the modulus voltage traveling waves (MVTWs) asynchronously sampled at each bus is captured. With the minimum TDOA, the key bus and fault area can be firstly determined. Then, the TDOA of the line in per unit length is defined as the ratio between the difference of the TDOAs at both terminal buses and line length. Finally, as for one case that key bus connects with no other bus, the line corresponding to the minimum TDOA of all the lines in the fault area is determined as the fault line. As for the other case, the calculated line length should be compared with the actual one to detect the fault line. PSCAD/EMTDC is used to conduct fault simulations and the calculation results verify that the proposed scheme is not affected by fault resistances, inception angles and distances. In addition, the operation time of the scheme does not exceed 20 ms, which makes it applicable for actual power grid protection.