Grounding Design For New Types Of Tower Foundations And Grounding Electrodes

It is common practice to use conductive concrete to encase the steel reinforcement cage within tower foundations.This enables the current to disperse from the pile foundation into the surrounding soil,resulting in improved resistance reduction.However,the intricate nature of the steel reinforcement cage structure poses significant challenges when attempting to accurately model the internal construction of the pile foundation.Furthermore,the computational complexity increases substantially.In light of these challenges,this paper presents a novel approach to calculate the grounding resistance of reinforced concrete pile foundations acting as natural grounding bodies.A comprehensive grounding model,combining the pile foundation and grounding device,is developed,and the dissipation of current in this model is analyzed under both power frequency and impulse conditions.The specific research inquiries conducted are as follows:Firstly,this paper proposes a calculation method for the grounding resistance of reinforced concrete pile foundations,which have complex structures and large computational requirements.Finite element analysis software was used to establish a calculation model for the grounding resistance of reinforced concrete pile foundations.Based on the principle that the dispersion resistance and axial impedance are equal,the radius,resistivity,and magnetic permeability parameters of the equivalent conductor were determined.The impact of factors such as the resistivity of concrete and soil,the number of main reinforcements,and lightning surge conditions on the equivalent process was analyzed to determine the applicability of the equivalent method.A comparison was made with two commonly used approximate equivalent methods,providing a simulation method for subsequent research on natural grounding body dispersion of pile foundations.Secondly,the dispersion analysis between pile foundation and grounding devices was conducted under power frequency conditions.The influence of the resistivity of conductive concrete on the grounding current distribution was explored.The grounding current ratio and shielding effect relationship between different pile foundation lengths and the length of the horizontal extension grounding body were studied.A combined grounding scheme for the pile foundation and grounding device was proposed to meet the engineering standard limit requirements for tower grounding resistance,providing theoretical and technical support for the design,construction,and acceptance of tower grounding projects for transmission lines.Finally,the combined grounding characteristics of the pile foundation and grounding device were analyzed under lightning impulse.Considering that the existing formula for calculating the effective length of lightning impulse is only applicable to a single horizontal grounding device,this study calculates the actual effective length of the external horizontal grounding device under different pile foundation lengths when the pile foundation and square tower base participate in the grounding condition,and the results are more universal.In addition,combined with the current distribution of pile foundation and grounding device under the standard lightning current waveform,this paper analyzes the impact of soil resistivity,pile foundation length,and external horizontal grounding device length on the current wavefront time,providing a reasonable explanation for the change in effective length of the external horizontal grounding device.Finally,combined with the effective length of the external horizontal grounding device and the lightning grounding resistance,the feasibility of the combined grounding scheme of the pile foundation and grounding device is further evaluated.