Directional earth fault protection can be effectively used to detect capacitively coupled earth fault current and block protection operation in these circumstances. Directional earth fault protection can be used for grading of non-radial feeders, but are most commonly used on radial networks to differentiate between real downstream faults and sympathetic capacitive currents. Go back to Contents Table ↑ 5.3 Current Reversal. 3: Operating zone example for DEF on resistive earthed networks. July 31st, 2018, Information from Noja Power. A special application problem occurs together with directional earth fault schemes communicating in a permissive overreaching (POR) scheme. These new relays consolidate several directional elements in one hardware package to … However, high-impedance ground fault detection is difficult in multigrounded four-wire systems, in which the relay measures the ground fault current combined with the unbalance current generated by line phasing and configuration and load unbalance. 1: Earth fault current paths in a resistively earthed network. 4: Earth fault in an unearthed network. The product line up offers applicable relays for ZVT or EVT systems. Directional Earth Fault. In a resistance earthed or solidly earthed network, this will be the largest component of the fault current is this resistive component. By staying here you are agreeing to our use of cookies. Earth faults are unique in that the fault current path also includes a capacitive component where the fault current leaves at the fault site, and returns via all the other connected feeders in the reverse direction. The Reyrolle 7SR45 Argus self-powered/dual powered non-directional overcurrent and earth fault relay. earth fault) with inverse time and definite time delay functions. When earth faults occur, a new circuit is completed as the foreign interference creates an earth path. Fig. An output contact matrix allows start or trip signals from the protection stages to be routed to the desired output contact. Submit your inquiry and we will contact you. KCEG 152. January 8, 2019. If the inductance in the transformer earth matched the capacitance of the network, and there was no resistance fault path, then earth faults would be reduced to almost zero. It is interesting to note that the zero sequence voltage angle is 180° out of phase (is a negative value) with the normal condition positive sequence. On detection of a fault, the relay will start, trip the circuit breaker, provide alarms, record fault data, etc., in accordance with the application and the configured relay functions. Earth fault magnitude, and its complexity, can be briefly summarised as: The key to understanding DEF is to visualise and understand the fault current path, so that protection selectivity can be set appropriately. The directional earth-fault relay can also be used for the earth-fault protection of power genera-tors and large motors. Like Directional Overcurrent, Directional Earth Fault (DEF) is used to differentiate between different fault types to ensure that co-ordination between protection devices such as distribution circuit breakers and reclosers is maintained. This principle is referred to as “Selectivity” in protection engineering. Earth fault current can be capacitively coupled to adjacent feeders and flow backward towards the substation bus causing false protection operations. From this, we can also see that the overcurrent RCA does not necessarily match the earth fault RCA. Modern techniques today include active compensation, devices which deliberately measure and inject compensation of energy to balance the fault and bring the current at the fault site to very low levels. ABB's website uses cookies. Vo connection) KCEG 242. With the Io/Vo measurement indicator it is possible to make suitable settings. The fault recording function makes it possible to investigate the cause of fault at an early stage. Since there is no apparent resistive earth path, this implies that single line-to-ground faults tend to have a low magnitude, but it certainly doesn’t mean that the lines are safe to touch. In E6 or E8 cases ground faults coordinate together for a myABB account to access of! You are agreeing to our use of cookies “Selectivity” in protection design software to the. These typically require specialist calculation and are beyond the scope of this,! The earth fault relays are directional voltage the more capacitance is available Sign up for a single line ground! 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