Numerical evaluation of currents induced in a worker by ELF non‐uniform electric fields in high voltage substations and comparison with experimental results

Abstract

An ungrounded human, such as a substation worker, receives contact currents when touching a grounded object in electric fields. In this article, contact currents and internal electric fields induced in the human when exposed to non-uniform electric fields at 50 Hz are numerically calculated. This is done using a realistic human model standing at a distance of 0.1-0.5 m from the grounded conductive object. We found that the relationship between the external electric field strength and the contact current obtained by calculation is in good agreement with previous measurements. Calculated results show that the contact currents largely depend on the distance, and that the induced electric fields in the tissues are proportional to the contact current regardless of the non-uniformity of the external electric field. Therefore, it is concluded that the contact current, rather than the spatial average of the external electric field, is more suitable for evaluating electric field dosimetry of tissues. The maximum induced electric field appears in the spinal cord in the central nervous system tissues, with the induced electric field in the spinal cord approaching the basic restriction (100 mV/m) of the new 2010 International Commission on Non-Ionizing Radiation Protection guidelines for occupational exposure, if the contact current is 0.5 mA.

Electric fields induced inside numerical human model standing on ground plane with elevated arms in uniform electric field at power frequency

“…In case of the erect position, that is, at the standard analysis condition, analytic results for induced currents in numerical human models were already reported . Particularly, Dawson and colleagues reports induced currents in different horizontal cross‐sections of a human model with the body height of 1.77 m. Generally, in low frequency region, short‐circuit current (current flowing from feet to ground) is known to increase in proportion to the product of squared body height and frequency . Thus we converted the results of literature to the body height of 1.73 m and frequency of 50 Hz adopted in this study, and compared the converted values with results of this study in Table .…”

“…Results of numerical analysis of induced electric fields in models under the standard condition were presented in many reports . On the other hand, there are also reports dealing with nonstandard conditions such as nonuniform electric field and nongrounded human models; in any case, electric fields induced in human body are weaker as compared to the standard condition.…”

Difficulties in applying numerical simulations to an evaluation of occupational hazards caused by electromagnetic fields

“…Such an influence of conductive objects on electric field distribution was presented in the Tarao et al’s investigations. [ 21 ]…”

Electric Fields Induced inside Numerical Human Model Standing on Ground Plane with Elevated Arms in Uniform Electric Field at Power Frequency

“…4,9 Particularly, Dawson and colleagues 4 reports induced currents in different horizontal cross-sections of a human model with the body height of 1.77 m. Generally, in low frequency region, short-circuit current (current flowing from feet to ground) is known to increase in proportion to the product of squared body height and frequency. 5,9,19 Thus we converted the results of literature 4 to the body height of 1.73 m and frequency of 50 Hz adopted in this study, and compared the converted values with results of this study in Table 2. As can be seen from the table, induced currents in every horizontal cross-section agree well in both cases.…”

“…Results of numerical analysis of induced electric fields in models under the standard condition were presented in many reports. [2][3][4] On the other hand, there are also reports dealing with nonstandard conditions such as nonuniform electric field 5,6 and nongrounded human models 4,7 ; in any case, electric fields induced in human body are weaker as compared to the standard condition.…”