A Comprehensive Method or Determining the Performance of Distance Relays

This paper presents a comprehensive method of determining the performance of distance relays along the lines indicated above which may be summarized as follows: 1. A general method by which the performance of any of the types of distance elements in common use may be determined from the effective impedance presented to the element. 2. A tabulation from which the effective impedance presented to any type of distance element under any condition of fault may be obtained in terms of the effective line impedance between the relay and the fault and 4 quantities which are characteristic of the system setup and location of the fault with reference to the relay. These quantities may be determined approximately by the use of a d-c calculating table setup. 3. A method for including the effect of fault resistance in the determination of the effective impedance presented to the relay. 4. Methods by which the performance of standard directional elements under fault conditions may be determined. 5. An extension of the general method to enable the expression of the operating time of CZ relays in terms of the effective impedance presented to the relay. 6. An extension of the general method to include the performance of distance relays connected for protection against single-phase-to-ground faults.