Re(Yo)Im(Yo)Susceptance forwardOPERATEOPERATEConductance forwardOPERATESusceptance reverseOPERATEConductance tilt Ang >0Susceptance tilt Ang <0Conductance reverseGUID-0A34B498-4FDB-44B3-A539-BAE8F10ABDF0 V1 ENFigure 168: Combined non-directional overconductance and non-directionaloversusceptance characteristicThe non-directional overconductance and non-directionaloversusceptance characteristic provides a good sensitivity andselectivity when the characteristic is set to cover the totaladmittance of the protected feeder with a proper margin.4.2.4.6 ApplicationNeutral admittance protection provides a selective earth-fault protection functionfor high-resistance earthed, unearthed and compensated networks. It can be appliedfor the protection of overhead lines as well as with underground cables. It can beused as an alternative solution to traditional residual current-based earth-faultprotection functions, for example the IoCos mode in DEFxPDEF. Main advantagesof EFPADM include versatile applicability, good sensitivity and easy settingprinciples.As a start condition for the neutral admittance protection, the residual overvoltagecondition is used. When the residual voltage exceeds the set threshold Voltage startvalue, an earth fault is detected and the neutral admittance calculation is released.In order to guarantee a high security of protection, that is, avoid false starts, theVoltage start value setting must be set above the highest possible value of UoSection 4 1YHT530004D05 DProtection functions330 615 seriesTechnical Manual
