Directional high-resistance earth fault detector based on zero-sequence components and wavelet transform

Distance relays are subject to fail to detect some earth faults since the fault resistance is usually much more in the earth faults rather than the ph-ph faults. Typically a traditional zero-sequence-based method is used to detect a high-resistance earth fault. However, this method fails to detect some high-resistance earth faults. On the other hand, it may trip under normal conditions where there is a little unbalance. This paper introduces a new method utilizing both zero-sequence components and wavelet transform to detect high-resistance earth faults. This method does not trip under normal conditions due to unbalancing whereas it is very sensitive to high-resistance earth faults. It will be shown by using proper simulations that the proposed method is fast and reliable.