Earth fault protections with sensors

Earth faults are the most common type of fault in medium voltage networks. Earth fault (EF) protection based on residual current detection is therefore the basic protection used in protection systems. Since small isolated and compensated MV networks with low levels of earth fault currents are now increasing in popularity, the use of earth fault protection with residual current detection based on traditional methods and equipment is therefore partly limited. Medium Voltage sensors (low-power stand-alone sensors) based on non-conventional principles provide an alternative method of making the current and voltage measurements required by protection applications. This paper explains how the benefits of MV sensors are utilized in EF protection and describes particular tests carried out to verify this solution.