A probabilistic method for the design of power grounding systems

An improved multivariable, probabilistic method for the safety analysis of power grounding systems is presented. The application of this method is demonstrated in four examples. The first three examples illustrate the practical evaluation of one new and two existing substation grounding grids when the substation is connected to an overhead distribution system. The fourth example ascertains the relative impact of a difference between the S curve of IEC Publication 479 and Dalziel's equation for the allowable body current used in ANSI/IEEE Std 80-1986 on the validity of an exposure model based on the requirements of Std 80. In this example, the statistical data on ground faults have been taken from actual system records. Further possible refinements of the exposure model are discussed     

Progress in step and touch voltage equations of ANSI/IEEE Std80-historical perspective

This paper describes the evolution of safety criteria and the development of basic formulae for evaluation of the step and touch potentials in AC substations, from 1961 to the present time. Refinements proposed for the 1996 edition of ANSI/IEEE Std 80 are presented in a broader context of the continuing development of this popular IEEE Guide. Examples of a typical grounding design illustrate the difference in evaluation procedures given in the 1961, 1986 and 1996 (proposed) editions, and their practical impact on making the design safe