Early detection of tree faults

Faults due to falling trees happen frequently. At the moment a tree falls on a transmission line, the impedance path of the tree is not fully conductive. Therefore, the tree resistance at these early stages is very high and hard to detect. As time passes, the conductivity of the tree increases (less fault resistance Rf) till the point where Rf is low enough for the protection algorithms to detect. This phenomenon could happen in both High Voltage and Medium Voltage networks. This paper focuses on the application of the protection function proposed in [1] for early detection of faults; especially tree faults. Tree faults with fault impedances up to 106 Ω can be detected. This very high value of impedances corresponds to very early stages of formation of the fault. Another important feature of the function in addition to detection of High Impedance Faults (HIF) is its security against non-fault phenomena like power swing, voltage instability and load encroachment. A comparison between the proposed function and conventional percentage differential relays shows superiority of the proposed approach. Other advantages are discussed throughout the text.