Can compensated networks be an alternate solution to reduce the risk of ground faults causing forest fires?

Abstract

Ground faults are the most common type of fault in a distribution network. The current seen by the protection relay during a ground fault event largely depends on the impedance of the fault circuit and applied system grounding principle. Therefore, detecting a ground fault effectively and accurately becomes challenging under certain circumstances. A small percentage of ground faults have a very large impedance. They are comparable to load impedance and consequently have very little fault current. These high-impedance faults do not pose imminent danger to power system equipment. However, they are a substantial threat to human beings and properties; people can touch or get close to conductors carrying large amounts of energy. Such ‘wire down’ faults have resulted in causing wild forest fires in some parts of the world with large scale devastation of vegetation and property.There are various technologies available, which can limit the amount of energy released when a ground fault occurs and thus reduce the risk of fire ignition. This paper studies the properties of resonant grounding, also known as compensated networks, which is the prevailing technology globally to limit ground fault current magnitude. The paper also discusses a unique approach to detect ground faults based on Multifrequency admittance principle (67YN). 67YN provides selective directional ground fault protection for any high-impedance grounded networks, that is, for compensated, ungrounded and high resistance grounded systems. It can be applied for the ground fault protection of overhead lines and underground cables. The operation of 67YN is based on novel multi-frequency neutral admittance measurement utilizing Cumulative Phasor Summing (CPS) technique. This concept provides extremely secure, dependable and selective ground fault protection in compensated networks.