Seasonal Variations of Tower Footing Impedance in Various Transmission Line Grounding Systems

Touch voltages are more likely to appear on long-distance pipelines that lie in shared corridors with transmission lines. The touch voltage level varies with soil resistivity and can become hazardous while maintenance is being undertaken, necessitating risk assessment. Therefore, a novel approach is proposed that achieves better accuracy in the risk assessment of hazardous touch voltages appearing on pipelines than current approaches. The proposed approach incorporates soil resistivity measurements taken over a 1-year period, allowing for the derivation of soil models, touch voltage hazard profiles versus time and, thus, a probability reduction factor that can be integrated into a probabilistic risk calculation. Using a probability reduction factor is a key aspect to improving the accuracy of risk assessment, allowing pipeline asset operators to clearly identify whether or not, risk mitigation action is required. Further, the proposed approach allows appropriate risk mitigation actions to be identified. The efficacy and significance of the proposed approach are demonstrated through a case study on an area of land near a shared gas pipeline and transmission line corridor. The case study results show how appropriate safety levels can be achieved by adjusting the number of work day per year and temporary protection settings.

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“…The Wenner test should ideally be carried out on the soil of a large volume of undisturbed earth [25].…”

Section: The Development Of the Seasonal Soil Modelmentioning

confidence: 99%

A novel approach to touch voltage risk assessment for gas pipelines in shared transmission corridors

Chan

Baguley

Madawala

2022

IET Science Measure & Tech

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“…model is a technique for determining how a reflection affects an electric signa is the simplest and most accurate of the PSCAD distributed branch models, the fact that it is not frequency-dependent [57,58]. Therefore, the tower surge impedance of each segment was determine (2). The parameter of the RL circuit representing the attenuation of the tra was computed based on the equation where 1, 2, 3 … , , and surge impedance between each cross arm and cross arm to earth in ohms total tower height in m, ℎ is the height of the top segment in m, ℎ is the tower middle segment in m, ℎ is the height of the tower bottom segment in damping resistance in ohms (Ω), is the damping inductance in Henrys attenuation coefficient (in this study it is 0.8) and is a damping coeffic unity.…”

Section: Tower Modelmentioning

confidence: 99%

“…, , and h were calculated using (3) to (6). Therefore, the tower surge impedance of each segment was determined employing (2). The parameter of the RL circuit representing the attenuation of the traveling waves was computed based on the equation where i = 1, 2, 3 .…”

Section: Tower Modelmentioning

confidence: 99%

“…A high lightning current will be produced by a direct lightning strike to the tower structure and will flow along the tower into the earth. Consequently, the impulse potential will be highly detrimental and will subsequently affect the tower and the earthing device efficiency [1][2][3][4][5][6]. The system failure due to BFO is measured as a back-flashover rate (BFR) that is typically related to high tower footing impedance and soil resistivity.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Lightning Current Parameters and Earthing System Designs on Tower Footing Impedance of 500 kV Lines

et al. 2021

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This paper presents an optimum earthing system design for improving the lightning performance of a 500 kV transmission line for its sustainable operation. The study includes an interpretation of the soil profile and compares the results between default and new earthing arrangements for improving tower footing resistance and tower footing impedance. An evaluation of the tower footing resistance (TFR) and impedance (Ri) before and after earthing improvement was carried out. Moreover, the effects of TFR and Ri, also known as low and high-frequency earthing, respectively, based on a specification of TFR and soil resistivity (SR) ranges at various sites were also considered. The analysis was carried out using the SESCAD tool of Current Distribution Electromagnetic Field Grounding and Soil Structure Analysis software (CDEGS) and PSCAD/EMTDC software for low and high frequency earthing, respectively. From the analysis, the results showed that the new earthing arrangement reduced the TFR by 74.11% for Tower T40, 75.71% for Tower T41 and 80.83% for Tower T42. For Ri, the results also demonstrated that the values were significantly decreased below the TFR during a high frequency operation due to the soil ionisation phenomenon that took place during the lightning. All these improvements are now being investigated and studied in all 500 kV networks in Malaysia, where lightning is considered as a major threat in relation to power outages.

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“…The study began with the creation of a comprehensive soil model by using the RESAP computation module. RESAP is dedicated to developing an equivalent soil structure model based on soil resistance measurements [58]. In detail, RESAP is dedicated to designing and interpreting analogous earth profile models based on soil resistivity or apparent resistance data as measured.…”

Section: Soil Modellingmentioning

confidence: 99%

Impact of Earthing System Designs and Soil Characteristics on Tower Footing Impedance and Ground Potential Rise: A Modelling Approach for Sustainable Power Operation

et al. 2021

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Improving a tower earthing system by reducing the impedance is an effective solution to prevent back flashover from occurring and thus maintaining the sustainable operation of power supply. Knowledge of the soil and earthing structure is an important element when designing an earthing system and to determine the parameters of a transmission line (TL). This paper presents the computation of soil structure interpretation based on several earthing designs using current distribution, electromagnetic interference, grounding, and soil structure analysis (CDEGS) software. The results showed that each tower has a multi-layer soil structure and it was also found that the soil resistivity at the surface layer strongly affected the earthing impedance. Subsequently, it was demonstrated that soil structure and the earthing design arrangement are the two parameters that significantly affected the ground potential rise (GPR). This aspect affects the resistance and impulse impedance of a tower and thus influences the performance of the TL system when subjected to lightning strike, which is undoubtedly one of the major culprits of power outages in Malaysia.

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Seasonal Variations of Tower Footing Impedance in Various Transmission Line Grounding Systems

Cited by 4 publications

References 9 publications

A novel approach to touch voltage risk assessment for gas pipelines in shared transmission corridors

A novel approach to touch voltage risk assessment for gas pipelines in shared transmission corridors

Influence of Lightning Current Parameters and Earthing System Designs on Tower Footing Impedance of 500 kV Lines

Impact of Earthing System Designs and Soil Characteristics on Tower Footing Impedance and Ground Potential Rise: A Modelling Approach for Sustainable Power Operation

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