Method for Evaluating Human Exposure to 60 HZ Electric Fields

This paper describes a method that has been successfully used to evaluate human exposure to 60 HZ electric fields. An exposure measuring system that uses an electric field sensor vest and data collection instrumentation is presented. Exposure concepts and activity factors are discussed and experimental data collected with the exposure system are provided. This method can be used to measure exposure to a wide range of electric field intensities from less than 1 V/m to more than 10 kV/m. Results may be translated to characterize various exposure indices (time histogram of unperturbed field, surface fields, internal current density, total body current, etc). The exposure measuring system includes a sensor vest, a data collection instrument, and a readout device. Fig. 1 shows the complete system in use. Lineman conductive suit cloth with 25 percent stainless steel yarn was sewn over a common vest or jacket. The vest collects field induced current that would normally be collected over part of the body. This current flows through data collection instrumentation that is carried in the vest pocket. The instrumentation contains ion transfer integrators that accumulate a charge proportional to the exposure (kV/m??h) for each of five different ranges of electric field. The vest calibration is performed for a reference condition, consisting of a person erect and grounded in a uniform electric field. The relation between vest current and other body electrical quantities has been determined, so that the exposure can be translated from equivalent field into other quantities of interest.