Pilot Protection Scheme for Collection Line of All-DC Offshore Wind Transmission System

To adapt to the development of long-distance offshore wind power, the all-DC transmission system based on DC collection and DC transmission has emerged. However, due to the addition of power electronic components and the influence of weak boundary characteristics of transmission lines, new requirements have been put forward for relay protection. The paper firstly proposes a topology structure of the all-DC system and analyses its fault characteristics. Then, a pilot protection method of collection line based on Kendall correlation coefficient is proposed for the given topology. This method utilizes the current correlation at both terminals of the line to select the faulty zone and faulty pole simultaneously. Finally, the performance of the proposed protection scheme is verified on the MATLAB/SIMULINK platform, and the results show that under different fault conditions, the selection of the faulty area and faulty pole can be reliably completed under a sampling window length of 1.2ms, meeting the rapidity requirements of all-DC system. It can withstand 20dB of noise interference and a certain transition resistance, and has advantages on its simple algorithm and low sampling frequency requirements.