Walking Electrification on Floor of High-Rise Building and Reduction Method of Human-Body Potential

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It is almost impossible to predict when the electromagnetic interferences (EMIs) of high-tech information equipment due to an event of electrostatic discharge (ESD) may happen. Particularly in the high-rise intelligence buildings, the wide use of high-polymers and air-conditioning facilities promotes such the EMI occurrence, which has brought about serious situations. We received grant-in-aids from 2001 to 2002 for scientific research to cope with the above-mentioned problem. As a result, we elucidated the mechanism of walking electrification on the floor of high-rise buildings, and grasped quantitatively the attenuation characteristics of human-body (HB) potential, which leads to providing effectively preventive means against EMIs caused by ESD events. The outline of the findings obtained in this study is as follows.In 2001, we proposed a new equivalent circuit model in order to predict the floor surface potential due to the induced charges on the floor, and verified its validity. For … More the footstep surface potentials that have never been measured so far, we tried to measure them with a newly developed measurement meter of two-dimensional footstep surface potentials, which consists of placement in line of commercially available potential meters. Comparing the measured waveforms of the footstep surface potential with those calculated using the equations derived from the equivalent circuit model, we found that the time change of the measured surface potential after the floor kick has the same trend as the calculated one. This finding implies that the equivalent circuit model can predict not only charge leak to the floor surface from the shoe sole landing on the floor but also leak process fo floor charges induced on the footstep for the shoe kicking the floor. Due to working failure of the footstep surface potential meter developed here, however, we could not obtain accurately the surface potentials, which did not enable us to confirm the quantitative verification of the proposed equivalent circuit model.In 2002, we improved the footstep surface potential meter and investigated the validity of the equivalent circuit for the charge leak process on the floor in comparison with the measurement of the floor surface potential. We first derived an equation in the Laplace domain for the footstep surface potential when the charged HB kicks the floor, and calculated the potential from the numerical inverse Laplace transformation. Also we measured simultaneously the HB and footstep surface potentials, changing the HB charge voltage. Comparing the measured potential waveforms with those calculated form the equivalent circuit model, we found that there is good agreement between the measured and calculated attenuation characteristics of the HB potential nomalized to the HB charge voltage. On the other hand, the measured attenuation characteristics of the footstep surface potential normalized to its initial potential approximately agreed with the calculated results regardless of the HB charge voltages, while we observed that there are some discrepancies between the measured and calculated initial footstep surface potentials and also that the measured potentials are not always proportional to the HB charge voltages. This may be because when kicking the floor, the charge occurs between the shoe sole and floor and it charges the floor capacitance, which results in changing the floor potential.The future subject is to grasp quantitatively the charge appearing due to walking on the floor and its dynamic time behavior. Less