A new method and instrument for touch and step voltage measurements

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