Faulty line detection method based on improved Hilbert-Huang transform for resonant grounding systems

Detecting a line experiencing single-phase-to-ground fault in a resonant grounding system is difficult due to weak fault current and low differentiation between the faulty line and healthy line. To overcome this difficulty, a novel faulty line detection method based on improved Hilbert-Huang transform is proposed in this article. The method consists of two parts: Hilbert marginal spectrum method (HMSM) and high frequency component method. HMSM is used for faulty line preliminary detection. Using this method, the zero-sequence current of each feeder is decomposed into several intrinsic mode functions, which represent the components of signals at different time scales by ensemble empirical model decomposition. Then, the Hilbert marginal spectrum energy of the characteristic frequency band of each feeder is calculated, and three feeders with the greatest energy are selected as the preliminary result. High frequency component method is then used to further distinguish feeder fault and busbar fault and provide a final detection result. It first reconstructs high frequency signals of the zero-sequence current, and then detects the faulty line by comparing the polarities of the signals. Simulation results show that the new method can precisely detect a faulty line in various fault conditions.