Soil Resistivity Evaluation and Grounding System Resistance

This chapter contains the factors affecting the soil resistivity and grounding resistance such as the soil moisture content, soil mineral content and soil temperature. It discusses the methods of measuring of soil resistivity and grounding resistance using Wenner method. Method to obtain the required samples for obtaining accurate site resistivity is presented. Soil resistivity measurement procedure is given in this chapter. The chapter contains three electrode method or fall-of-Potential method, dead earth method, and ground resistance testing existing systems using ‘Selective' Clamp-on-Measuring of high voltage transmission towers feet resistance. Methods of calculating the apparent soil resistivity of Multi-Layers, apparent soil resistivity of two layers and apparent soil resistivity of three layers are presented in this chapter.

Transient Response of Grounding Systems

This chapter describes a model used to simulate lightning current. Comparison of different approaches used for lighting simulation has been mentioned. Transmission line approach has been chosen to simulate the grounding system behavior under lightning condition. Two different types of the grounding system have been studied under lightning conditions vertical driven electrodes and buried grids. This chapter draws attention also to the following points: equivalent circuit of a vertical ground rod on lightning condition, sensitivity analysis of soil parameters and grounding rod dimensions, equivalent circuit of grounding grid on lightning conditions and sensitivity analysis of soil parameters and grounding grid dimensions.

Cathodic Protection of Grounding Grids

This chapter contains the corrosion theory of grounding electrodes and basic electrochemistry in corrosion reactions. It contains also the forms of substation grounding grid corrosion (uniform corrosion, pitting corrosion, galvanic corrosion, microbial influenced corrosion), survey on corrosion rate of substation grounding grid, copper and steel corrosion rates, corrosion protection methods (coating, cathodic protection [CP]). The chapter contains also the methods of applying cathodic protection in grounding grids, anode selection, anode spacing, and impressed current in the grounding grid cathodic protection. Finally it contains the required information for design grounding system cathodic protection and sacrificial anode (galvanic) cathodic protection system design steps.

Step and Touch Voltages and Grounding Potential Rise (IEEE and IEC)

This chapter contains safety criteria according to IEEE Standards, step and touch voltage criteria, reduction factor, simplified equations for mesh and step voltage, application of step and mesh potential in safe earthing system design, safety criteria, IEC 479-1 STD, permissible touch and step voltage according to IEC 479-1, Optimum Compression Ratio (OCR), test and verify, approximated analysis to calculate voltage profile using apparent soil resistivity, Scaling factor, test and verify the approximated method—Ground Potential Rise (GPR) of faulty substations having equal and unequal spacing grounding grids conductors. This chapter draws attention also to the following points: Infinite Series Potential (I.S.M.) expressions in three dimensions and calculations of three dimensions potential rise.

Grounding Connections

This chapter sheds light on the following: TT system (earthed neutral), automatic disconnection for TT system, TN system (exposed conductive parts connected to the neutral), TN-C system, TN-S system- TN-C-S system, IT system (isolated or impedance-earthed neutral), IT system (impedance-earthed neutral), grounding transformer connection and design, grounding of industrial and commercial generators, Zigzag grounding transformer earthed systems (solid grounding, resistance grounding, reactance grounding, resonant grounding (ground-fault neutralizer), location of system grounding points selection and grounding locations specified by the NEC and multiple power sources. The chapter contains also the different methods used in determining the levels of short circuit current. It contains also details about the grounding through resistances for transformers and generators and reactances for overhead transmission lines.

Design of Grounding System

This chapter contains the types of grounding systems, single ground rod, single strip end connected, single strip center connected, radial grounding, single radials, equipotential mesh electrodes, radial grounding, multiple radials, and grid electrodes grid with ground rods, ring electrode, and grounding chain. It contains also the method of calculating single grounding electrode system resistance, length/depth of the ground electrode, diameter of the ground electrode and number of ground electrodes to obtain the required grounding system resistance. The chapter contains the grounding nomograph, example worksheet using nomograph, design of multiple grounding electrode in straight line and ring systems, examples layout and graph, multiple grounding electrode system are presented. It contains also calculating methods of multiple grounding electrode system resistance of different configurations. Color code technique to calculate the design parameters of the grounding rods is also presented.

Design of Grounding Grid According to IEEE Standards

This chapter contains the following points: design procedure of grounding system according to IEEE 80, methods for calculating the grounding grid resistance (Dwight's formula, Laurent and Niemann, Sverak's equation, Schwarz's Formula, Dawalibi, Mukhedkar's Formula, Chow and Salama's Formula, Nahman's Formula and Heppe's Method). It contains also the design of charts of grid earthing system and application of step and mesh potential in safe grounding system design. This chapter draws attention also to the following points: Grounding resistance of grounding system in non-homogeneous soil, calculations of maximum step and mesh voltages, estimation of minimum buried grid conductor length and finally computerized analysis in grounding design.

Grounding System Installation

This chapter includes the following points: Methods of installing ground rods, chemical ground rod, chemical treatment of soil lessens seasonal variation of electrodes, soil treatment, trench method of soil treatment, lengthen of the earth electrode in the earth, use multiple rods, Ground Enhancement Material, (GEM), grid installation and conductor materials of grounding system. This chapter draws attention also to the following points: ground rod life expectancy, ground rod annual cost, grounding rods accessories and applications, grounding rods installation methods, chemical grounding rods, copper versus stainless steel electrodes, variation on grounding resistance system by seasonal variation effects and finally how to improve the earthing resistance.