Electrical Power Engineering Chapter 3: Earthing & Grounding

Learn how fault currents cause ground potential rise on towers, and distinguish step potential from touch potential along potential lines to assess safety inside and around substations.

Explore ground potential rise, earth electrode placement, and transfer and touch potentials near live cables; compare site versus external conductor effects on worker safety.

Calculate earth conductor resistance using resistivity, length, diameter or width, burial depth, and compare strip versus round conductors for earthing design.

Calculate plate resistance from area and the equivalent radius using the given dimensions and resistivity. Note that plates are usually avoided due to cost and complexity, but can improve contact.

Calculate the resistance of a closed loop earthing system by deriving an equivalent circle radius from the loop area and incorporating conductor depth and diameter, using the example values.

Learn to estimate the minimum earth resistance of a mesh grid without earthing rods by treating it as a solid plate, using area, burial depth, and conductor length formulas.

Explore two methods for calculating the equivalent resistance of mesh earth grids with earthing rods: a simple length-based estimate and a detailed rod-resistance approach considering burial depth and proximity effects.

Learn how to determine the cross section of earth conductors using K factors and temperature limits, comparing copper, aluminum, and steel through current density calculations.

Compute touch and step voltage limits for substations by evaluating metal-to-metal touch voltage and body-path currents, using body weight, fault duration, and surface insulation multipliers.

Calculate mesh and step potentials in earthing design to assess ground fault safety and ground potential rise, using flowcharts and regulatory limits for touch and step potentials.

Explore a comprehensive earth system design for earthing, guiding data gathering, connector sizing, and calculations of ground potential rise, touch and step potentials, with iterative design adjustments.

Follow general safety rules for earthquake measurements by testing on sunny days to reduce lightning risk, wear high voltage insulated gloves and footwear, and avoid energized or underground metallic structures.

Soil resistivity varies with soil type, moisture, temperature, and mineral content; salt levels and moisture affect resistance, guiding measurements and return path depth for long transmission lines.

Explore soil resistivity measurement using the variation of depth method, a three-point approach deploying current injection and voltage probes to reveal top and bottom layer resistivities.

Explore the four-point method for measuring soil resistivity with Wenner–Schlumberger probes, detailing equal spacing, current and voltage probes, and depth considerations for layer analysis.

This lecture explains the dead earth method for measuring earth resistance, shows electrode connections, and explains how high resistance yields large errors, noting that two-point methods are preferable in practice.

Master the three-point method for earth resistance measurement using three measurements with different rod pairs. Compute the resistance with the R1, R2, and R3 readings using the described formula.

Explore the fall of potential method for earth resistance measurement, using current and potential probes to locate a constant-resistance zone while avoiding proximity effects.

this lecture presents the equilateral triangle method for earth resistance measurement, placing probes to form equilateral triangles and comparing mirrored measurements, and compares it with the follow potential method.