It is usual practice to protect 85% of the winding. 196) is supplemented by another differential relay 87T that acts on external faults to 87TG. An external fault in the star side will result in current flowing in the line current transformer of the affected phase and at the same time a balancing current flows in the neutral current transformer, hence the resultant current in the relay is therefore zero.So this REF relay will not be actuated for external earth fault. Restricted earth fault protection is a type of earth fault protection which looks for earth fault between two sets of current transformers (hence restricted to that zone). The restricted earth fault protection … Technical implementation 3.1. A restricted earth fault relay would therefore, if no special measures were taken, sen-se an “earth fault current” that does not exist on the primary side. Restricted Earth Fault Operation Under normal conditions and by application of Kirchhoff’s laws the sum of currents in both current transformers (CTs) equals zero. A fault … The combined restricted earth-fault and residual earth-fault relay SPAJ 115 C is intended to be used for the earth-fault protection of power generators, motors and transformers. For restricted earth fault relays, both sensitivity and stability tests are necessary, as these relay schemes may be subject to through-fault … Restricted Earth Fault Relays. Based on logic: Differential; Unbalance; Neutral Displacement; Directional; Restricted Earth Fault; Over Fluxing; Distance Schemes; Bus bar Protection; Reverse Power Relays; Loss of excitation; Negative Phase Sequence Relays … Voltage restraint over current relay; लॉजिक के आधार पर. Geoff Macangus-Gerrard, in Offshore Electrical Engineering Manual, 2018. Connection scheme The flexibility of REF 542plus allows the relay … The relay contains two energizing input circuits, that is, a differential earth-fault current circuit and a residual earth-fault … If there is an earth fault between the CTs … ۳۰: رله حفاظتی اتصال زمین (ولتاژ باقیمانده) (residual voltage) earth fault relay ۶۴ Please notice that the restricted earth fault relay (87TG in IEEE Std 242-1986 Fig. Distance (impedance relay) Distance protection detects both voltage and current. Practical experience has shown that a relay … Hence it is called restricted earth fault protection. It is self-evident that the differential relay … "The Restricted Earth Fault Relay Operation_Impact of Current Transfprmer Knee Voltages," The International Journal Of Engineering And Science (IJES), Volume 2, Issue 12, 2013. restricted earth fault ۶۴ n87 این رله در زمانی که در محدوده کار رله اتصال زمین به وجود آید، عمل میکند. Hence the relay coil remains unprotected in this scheme. Restricted Earth Fault Protection of Transformer. The RADHD relay therefore contains a filter circuit which will attenuate the dc component. 10 Restricted Earth-Fault Protection in 1MRS756411 REF 542plus Application and Setting Guide REF 542plus 3.