| Title |
Evaluation of the Accuracy of Grounding Impedance Measurement of Grounding Grid |
| Authors |
Jong-Hyuk Choi ; Young-Chul Choi ; Dong-Cheol Jeong ; Dong-Seong Kim ; Bok-Hee Lee |
| Keywords |
Ground Grid ; Ground Impedance ; Earth Mutual Resistance ; AC Mutual Coupling |
| Abstract |
Recently, the common grounding systems are adapted in most large structures. Since the ground resistance is insufficient to evaluate the performance of grounding systems, it is needed to measure grounding impedance. Even though the methods of measuring grounding impedance of large grounding systems are presented in IEEE standard 81.2, but they have not been described in detail. In this paper, we present the accurate method of measuring grounding impedance based on the revised fall-of-potential method and measurement errors due to earth mutual resistance and ac mutual coupling depending on locating test electrodes at remote earth were examined for the 15[m]×15[m] grounding grid. As a result, the measurement error due to earth mutual resistance is decreased when the distance to auxiliary electrodes increased. To get rid of measurement errors due to mutual coupling, the potential lead should be installed at a right angle to the current lead. When the angle between the potential and the current leads is an acute angle or an obtuse angle, the mutual couple voltage is positive or negative, respectively. Generally, the measurement errors due to mutual coupling with an obtuse angle route are lower than those with an acute angle route. |