Citation

Syed Abdullah, Syarifah Amanina (2025) Influence of soil resistivity on soil ionisation process in grounding systems under impulse conditions. PhD thesis, Multimedia University.

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Abstract

Grounding system is influenced by various parameters, which include its main parameters; soil resistivity and ground electrode dimensions. Under transient conditions, grounding systems exhibit complex behaviours characterized by nonlinear resistance caused by soil ionisation and inductive effects. While prior studies have investigated these phenomena, inconsistencies in test setups, particularly the remote earth’s arrangement, require further investigation. This study experimentally analyses these effects through high impulse tests by utilising a 300 kV impulse generator, and steady-state measurements by using Fall-of-Potential method, alongside simulations to model transient responses. The influence of remote earth configurations (separated distance away and circulated around the grounding systems) were tested, confirming its impact on the results. CDEGS and PSpice simulation studies were conducted to gain more theoretical understanding of the inductive and capacitive oscillations observed from the impulse response and also to observe the electromagnetic interference between the remote earth and the grounding electrode under test respectively. The CDEGS simulations quantified 80 m as the optimal distance for minimizing ground potential rise (GPR) and magnetic interference (83% GPR reduction, 95.3% M-field reduction). Subsequent impulse tests on varied soil resistivities and electrode configurations revealed that high-resistivity soils exhibit higher non-linear resistance reduction, up to 90 % due to ionisation. Critical ionisation thresholds (Ec), determined through transmission tower and single-rod field measurements, ranged 13 to 4100 kV/m, depending on soil type and moisture content (clay, sand, and gravel), further validating these trends. PSpice simulations incorporating non-linear resistance, inductance, and capacitance successfully replicated experimental observations: inductive components produced delayed rise times and negative-polarity discharges, while capacitive effects generated hazardous voltage oscillations. This study provides practical guidance for impulse testing and grounding design by identifying three critical factors: proper remote earth setup, soil ionisation with non-linear resistance behaviour (including Ec), and accurate grounding system modeling of non-linear resistor with inductive and capacitive effects. Field and simulation results confirm their importance, particularly in high-resistivity soils, for ensuring effective lightning protection and high-voltage system performance.

Item Type:	Thesis (PhD)
Additional Information:	Call No.: TK3227 .S93 2025
Uncontrolled Keywords:	Electric currents—Grounding
Subjects:	T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK3001-3521 Distribution or transmission of electric power
Divisions:	Faculty of Artificial Intelligence & Engineering (FAIE)
Depositing User:	Ms Nurul Iqtiani Ahmad
Date Deposited:	10 Jun 2026 03:58
Last Modified:	10 Jun 2026 03:58
URII:	http://shdl.mmu.edu.my/id/eprint/16100

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