A NEW METHOD AND INSTRUMENT FOR TOUCH AND STEP VOLTAGE MEASUREMENTS

This paper describes a new method and instrument for measuring touch a nd step voltages near a grounding system, for example in and around a substation. The hardware, software, and testing procedures are an exte nsion of the smart ground multimeter, developed under EPRI sponsorship . The instrument injects a transient electric current between the grou nd under testing and an auxiliary ground, and it measures ground poten tial differences (GPDs) at up to six locations. The GPD measurements a re processed with software which rejects external noise using correlat ion methods. Subsequently, statistical estimation methods are used to extract the touch or step voltages from the thousands of measurement p oints normalized with the system short circuit capability. Knowledge o f the short circuit capability of the substation allows the quick meas urement of the touch and step voltages.