Directional Characteristics of Distance Relay Mho Elements: Part I - A new Method of Analysis

A general study of the effect of line loading on the response of mho elements oth reverse faults has necessitated the development of an alternate method of representing the response of various types of mho elements. This paper reviews the usual methods and establishes the basis for an alternate method. With this new method, the response of any type of mho element is represented by impedances that are viewed with respect to a characteristic circle passing through the origin and the reach point on the R-X plane. This characteristic is the same for each element and is invariant with power system parameters and the fault type. Since the calculation of an impedance only is required, this method lends itself to general computer analyses of mho element response as well as to manipulation of expressions obtained from power system network analysis.