high impedance fault detection in power transmission lines using hilbert transform and instantaneous frequency

Power transmission lines are vital components of today's power systems. these power lines transmit the electricity produced in power plants in high volume and with very low losses to distant areas so that it can be reached consumers through distribution networks. in fact, these lines are the intermediary between major energy producers and distribution networks. accordingly, these transmission lines are of great importance and must be protected appropriately with a suitable protection system. distance relays are widely used to protect these lines due to their convenient coordination characteristics and simplicity. high impedance faults (hifs) can be a critical challenge for distance relays due to their low current amplitude and similarity to conventional events in power systems, such as capacitive bank switching. therefore, this paper presents a new approach based on the instantaneous frequency variations obtained from the current rms to detect hifs. this method detects hifs by calculating a detection index (di) and considering a threshold value. the proposed method was tested using digsilent and matlab software in an ieee standard 39-bus network. the presented results evidently demonstrate that the proposed method is suitable for detecting hif and low impedance faults (lifs). in addition, this method has a proper performance during capacitor bank switching and can well distinguish between hifs and capacitive bank switching. moreover, the presented method is resistant to noise and is also capable of detecting the faulty phase.