Improved distance protection for wind farm transmission line based on dynamic frequency estimation

The frequency of the fault current fed by the wind farm may deviate from the fundamental frequency after the line fault. This characteristic seriously affects the performance of the traditional distance protection. This paper proposes an improved distance protection method based on dynamic frequency estimation. After the protection is started, the dynamic frequency is estimated by multiple signal classification algorithm firstly. The distance criterion is not activated until the estimated frequency is close to the fundamental frequency. Accordingly, the influence of the frequency deviation of the fault current on the traditional distance protection is prevented. The delay time of the protection can be significantly shorted compared with the fixed-delay method due to the fast estimation of the transient frequency. Finally, the RTDS simulation model is built to validate the correctness of theoretical analysis and superiority of the proposed method. The fault recording data of practical engineering is also discussed to further verify the feasibility of the proposed method.