461 / 2022-03-15 23:10:46

Configuration analysis of transmission tower grounding systems

soil resistivity,Transmission line tower,grounding,soil structure,ground resistance

Purpose/Aim

The present study proposes some alternative ground electrode layouts and geometries for transmission tower earthing and investigates the efficiency of the proposed models under high soil resistivity conditions for alleviating the problem of high ground resistance level. Aim of this work is the establishment of a new possible grounding method for tower foundation earthing which will respond efficiently to the high annual variances of soil resistivity attributed to soil humidity, temperature, salts, and soil structure.

Experimental/Modeling methods

The work refers to grounding methods applied to the transmission line (TL) towers of high and ultra-high voltage in the Greek power transmission system and analyzes the purpose of the low ground resistance value required in the international grounding practice. The study modifies the geometry of existing tower foundation electrodes, already used in the Greek transmission system, in order to produce and propose a new foundation electrode layout with the same length to the existing one and with no further cost burden. The proposed electrode model is investigated for its adequacy and efficiency under various soil conditions and structures employing proper software tools and considering single or two-layer soil model. Mathematical analysis also describes the effect of soil structure (resistivity variation dew to moisture and underground stratification) on the resistance of the studied grounding systems.

Results/discussion

The study is completed by comparing the results of the various simulations and quoting conclusions about the effectiveness of the proposed grounding layout and the potential of its establishment as a new tower foundation grounding of the transmission lines. The results show that the proposed grounding model seems to respond adequately to variable soil conditions which is really intended for this work.

Conclusions

Useful conclusions are drawn concerning the behavior of the proposed grounding system in a two-layer soil structure. More specifically, the behavior of the proposed layout is studied for two cases of the soil model with the upper layer obtaining higher and lower resistivity value than the lower one. The proper configuration of the electrode geometry results in a consistent annual performance regarding the ground resistance value of the tower foundation grounding.