International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME 156 CALCULATION OF GROUNDING RESISTANCE AND EARTH SURFACE POTENTIAL FOR TWO LAYER MODEL SOIL Hatim Ghazi Zaini Taif University, Faculty of Engineering, Electrical department h.zaini@tu.edu.sa ABSTRACT For two layer model soil, the calculation of apparent resistivity is considered very important issue since the absent of a specified method to find it. Some empirical resistivity formula is used in this paper to present the apparent resistivity of the two layer model soil. A current simulation method technique which is a practical technique for calculating the grounding resistance (R g ) as well as the Earth Surface Potential (ESP) of the grounding grids in two- layer model soil which based upon the apparent resistivity of the two layer soil and simulating current sources is used. it is analogous to the Charge Simulation Method. The validation of the method is described by a comparison with the results in literatures. Index terms--Grounding grids, two-layer soil, current simulation method, Computer methods for grounding analysis, System protection. I. NOMENCLATURE P aij = Potential coefficient matrix related to apparent resistivity P 1ij , P 2ij Potential coefficient matrix related to resistivity of layer 1 and 2 respectively I j =current source at point j V i = voltage at evaluation point i  a =apparent soil reistivity  1 =soil reistivity of layer 1  2 =soil reistivity of layer 2 d =distance between current source point and evaluation point in original grid d' =distance between current source point and evaluation point in image grid J =current density (A/m 2 ) F =field coefficient zz i & zz j = the dimension of the contour point and current source in z direction respectively R g =grounding resistance d 0 = the depth to the boundary of the zones, INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING & TECHNOLOGY (IJEET) ISSN 0976 – 6545(Print) ISSN 0976 – 6553(Online) Volume 3, Issue 3, October - December (2012), pp. 156-163 © IAEME: www.iaeme.com/ijeet.asp Journal Impact Factor (2012): 3.2031 (Calculated by GISI) www.jifactor.com IJEET © I A E M E