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

2021 ◽  
Vol 13 (15) ◽  
pp. 8370
Author(s):  
Nur Alia Farina Mohamad Nasir ◽  
Mohd Zainal Abidin Ab Kadir ◽  
Miszaina Osman ◽  
Muhamad Safwan Abd Rahman ◽  
Ungku Anisa Ungku Amirulddin ◽  
...  
Keyword(s):  
Electromagnetic Interference ◽  
Soil Structure ◽  
Lightning Strike ◽  
Sustainable Operation ◽  
Power Operation ◽  
Two Parameters ◽  
Sustainable Power ◽  
System Designs ◽  
Ground Potential ◽  
Modelling Approach

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.

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

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4736
Author(s):  
Nur Alia Farina Mohamad Nasir ◽  
Mohd Zainal Abidin Ab Kadir ◽  
Miszaina Osman ◽  
Muhamad Safwan Abd Rahman ◽  
Ungku Anisa Ungku Amirulddin ◽  
...  
Keyword(s):  
Electromagnetic Field ◽  
High Frequency ◽  
Soil Structure ◽  
Analysis Software ◽  
Soil Resistivity ◽  
Major Threat ◽  
Lightning Current ◽  
Sustainable Operation ◽  
Before And After ◽  
System Designs

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.

scholarly journals Modelling runoff at the plot scale taking into account rainfall partitioning by vegetation: application to stemflow of banana (<I>Musa</I> spp.) plant

2009 ◽  
Vol 6 (3) ◽  
pp. 4307-4347 ◽  
Author(s):  
J.-B. Charlier ◽  
R. Moussa ◽  
P. Cattan ◽  
Y.-M. Cabidoche ◽  
M. Voltz
Keyword(s):  
Soil Surface ◽  
Plant Canopy ◽  
Flood Events ◽  
Runoff Generation ◽  
Flood Hydrograph ◽  
Rainfall Depth ◽  
Relative Water ◽  
Two Parameters ◽  
Runoff Production ◽  
Modelling Approach

Abstract. Rainfall partitioning by vegetation modifies the intensity of rainwater reaching the ground, which affects runoff generation. Incident rainfall is intercepted by the plant canopy and then redistributed into throughfall and stemflow. Rainfall intensities at the soil surface are therefore not spatially uniform, generating local variations of runoff production that are disregarded in runoff models. The aim of this paper was to model runoff at the plot scale, accounting for rainfall partitioning by vegetation in the case of plants concentrating rainwater at the plant foot and promoting stemflow. We developed a lumped modelling approach, including a stemflow function that divided the plot into two compartments: one compartment including stemflow and the relative water pathways and one compartment for the rest of the plot. This stemflow function was coupled with a production function and a transfer function to simulate a flood hydrograph using the MHYDAS model. Calibrated parameters were a "stemflow coefficient", which compartmented the plot; the saturated hydraulic conductivity (Ks), which controls infiltration and runoff; and the two parameters of the diffusive wave equation. We tested our model on a banana plot of 3000 m2 on permeable Andosol (mean Ks=75 mm h−1) under tropical rainfalls, in Guadeloupe (FWI). Runoff simulations without and with the stemflow function were performed and compared to 18 flood events from 10 to 130 mm rainfall depth. Modelling results showed that the stemflow function improved the calibration of hydrographs according to the error criteria on volume and on peakflow and to the Nash and Sutcliffe coefficient. This was particularly the case for low flows observed during residual rainfall, for which the stemflow function allowed runoff to be simulated for rainfall intensities lower than the Ks measured at the soil surface. This approach also allowed us to take into account the experimental data, without needing to calibrate the runoff volume on Ks parameter. Finally, the results suggest a rainwater redistribution module should be included in distributed runoff models at a larger scale of the catchment.

scholarly journals Mechatronic simulator of lever driven wheelchairs

2013 ◽  
Vol 27-28 (3-4) ◽  
pp. 65-69
Author(s):  
Włodzimierz Choromański ◽  
Krzysztof Fiok ◽  
Andrzej Potyński ◽  
Grzegorz Dobrzyński
Keyword(s):  
Work Conditions ◽  
Point Of View ◽  
Wheelchair Propulsion ◽  
Disabled People ◽  
Propulsion Systems ◽  
Wheelchair Users ◽  
The World ◽  
Two Parameters ◽  
System Designs ◽  
Training Station

Development of the lever-driven wheelchairs by different authors resulted in creating various lever-human work conditions in which disabled people propel their wheelchairs. This fact implies varying efficiency of human’s work during lever wheelchair propulsion. In order to assess which of the world-wide proposed lever propulsion systems is the most efficient from the humans’ work point of view a proper simulator was designed. Here described test stand offers the possibility to perform various ergonomic tests, it can also become a training station for the lever wheelchair users. Since the main differences in world known lever propelling system designs concern the lever length and levers axis of rotation position on the wheelchair, the wide regulation of these two parameters, was a decisive factor in designing the mechatronic simulator.

scholarly journals Impact of Lightning Protection Grounding System on the Ground Surface Potential of Substations

2022 ◽  
Vol 2148 (1) ◽  
pp. 012049
Author(s):  
Tingji Chen ◽  
Lian Yang ◽  
Weibing Gu ◽  
Haiyang Gao ◽  
Junchi Zhou ◽  
...  
Keyword(s):  
Ground Surface ◽  
Steel Structure ◽  
Metal Structure ◽  
Lightning Strike ◽  
Lightning Protection ◽  
Peak Time ◽  
Lightning Flash ◽  
Grounding System ◽  
Multiple Electrodes ◽  
Ground Potential

Abstract Grounding device is an indispensable facility for lightning protection of buildings. Nowadays, SGCC (State Grid Corporation of China) is promoting steel structure substations, which are made of metal as a whole including the roof. There are now several grounding approaches when the roof was struck by a lightning flash, including external grounding, nearby grounding, separate grounding and common grounding. This paper took a metal structure substation in Nanjing as an example and calculated its ground potential in case of different grounding system. We came to such conclusions: 1) For substations of separate grounding system, the ground potential after a lightning strike could reach as high as 743.5kV and 230kV with a single earthing electrode and multiple electrodes respectively. 1000μs after the strike, the ground potential is 91.57 kV, which is still a significant threat to humans and equipment inside. 2) Nearby grounding and external grounding are both common grounding system. The peak of ground potential after a lightning strike is 101.4kV and 109kV respectively, much lower than that of separate grounding system. They also have similar waveform and peak time. 3) 3500μs after the lightning strike, the ground potential all over the grid is around 36V. 4) Separate grounding is not a sound choice of grounding system for steel structure substations. From the perspective of cost and discharging capacity, nearby grounding is the most reasonable scheme for a steel structure substation.

SIGNIFICANCE OF SOIL-STRUCTURE INTERACTION IN SEISMIC RESPONSE OF BUILDINGS

2019 ◽  
Vol 1 (Special Issue on First SACEE'19) ◽  
pp. 43-54 ◽  
Author(s):  
Naveed Anwar ◽  
Abinayaa Uthayakumar ◽  
Fawad Ahmed Najam
Keyword(s):  
Seismic Performance ◽  
Soil Structure ◽  
Seismic Analysis ◽  
Soil Structure Interaction ◽  
Approximate Methods ◽  
Practical Applications ◽  
Structure Interaction ◽  
Explicit Consideration ◽  
Seismic Response Of Buildings ◽  
Modelling Approach

In current design office practice, a commonly used modelling assumption is that the base of a building structure can be idealised with fixed support conditions, thereby neglecting any effects from soil-structure interaction (SSI). Various recent studies, however, have shown that the explicit consideration of SSI effects in seismic analysis of buildings structures may significantly affect the predicted seismic demands and resulting structural performance. This study addresses some key issues and practices in the area of SSI and its effects on the dynamic response and seismic performance of buildings. It is also intended to demonstrate the significance of considering SSI effects in structural modelling and analysis while providing key insights into practical applications in real projects. Using a forty storey example building, the effect of considering SSI on the predicted seismic performance is demonstrated. For the purpose of comparison, five detailed computer models (one without considering any SSI effects, two models with SSI modelled using indirect approach, and two models with SSI modelled using direct approach) of the example building were constructed and subjected to various input ground motions. It is observed that depending upon the modelling approach used, the consideration of SSI effects may affect the predicted seismic performance in varying degrees. Moreover, the direct modelling approach presented in this study may provide improved results compared to various approximate methods.

Effects of Various Earth Grid Configurations on Ground Potential Rise Caused by Lightning Strike

2019 ◽  
Vol 1 ◽  
pp. 14-20
Author(s):  
F.P. Madrin ◽  
H. Widyaputera ◽  
E. Supriyanto ◽  
Z.A. Malek ◽  
M.A.A. Taib ◽  
...  
Keyword(s):  
Mesh Size ◽  
Electrical Equipment ◽  
The Other ◽  
Lightning Strike ◽  
Potential Hazard ◽  
Other Hand ◽  
Grounding Grid ◽  
Significant Difference ◽  
Ground Potential ◽  
Grid Mesh

Ground Potential Rise (GPR) caused by lightning strike is a potential hazard for electrical equipment inside an oil and gas refinery plant. In order to mitigate the risk, horizontal grounding grid is applied. The best mitigation is to install a grounding grid with mesh size as small as possible. This condition requires a high cost. In order to obtain the optimal mesh size, a series of simulation of a grounding grid with mesh size variations on GPR caused by lightning strike has been carried out. CDEGS software was used to observe the GPR with various mesh size from 6.5 x 6.5 m to 20 x 20 m. Simulation results show that the maximum transient GPR rises as the grounding grid mesh size is increased, while the GPR distribution throughout the grounding grid area does not change much for different mesh sizes. In the other hand, decreasing the grid size would mean that more conductors are required, hence the cost would increase accordingly. The result shows that grid sizes from 6.5 x 6.5 m up to 20 x 20 m have no significant difference in term of GPR. In term of cost, 10 x 10 m does not show significant difference with 20 x 20 m, on the other hand, there is a significant difference for grid sizes 1 x 1 m to 10 x 10 m. From the results, grid sizes between 10 x 10 m up to 20 x 20 m are still applicable as stated in Petronas Technical. To comply with proper GPR value, additional protection devices are needed to protect the electrical equipment from potential damage.Keywords –GPR, grounding grid, mesh size

Lightning Strike Protection and EMI Shielding of Fiber Reinforced Composite Using Gold and Silver Nanofilms

2018 ◽  
Author(s):  
Praveen K. Bollavaram ◽  
Muhammad M. Rahman ◽  
R. Asmatulu
Keyword(s):  
Carbon Fibers ◽  
Electromagnetic Interference ◽  
Weight Ratio ◽  
Lightning Strike ◽  
Surface Conductance ◽  
Composite Panels ◽  
Fiber Reinforced ◽  
Lightning Strikes ◽  
Composite Sandwich ◽  
Metallic Nanofilm

Carbon fiber reinforced composites are very much imperative to future-generation aircraft structures. However, lightning strike protection (LSP) and electromagnetic interference (EMI) are main concerns. Carbon fibers have very good mechanical properties with the best strength-to-weight ratio, but they are very poor conductors of electricity. These fibers must be reinvented to increase the surface conductance to provide high electrical conductivity to the aircraft structure. The present study deals with preparing composite sandwich structures of carbon fibers used for commercial nacelle applications subject to lightning strike effects with different metallic nanofilm of gold (Au) and silver (Ag) measuring approximately 100 nm. These metallic nanofibers were co-cured on the top layers of composite panels during vacuum curing process. In our laboratory, lightning strike results for a composite sandwich structure using nanofilms were obtained to observe lightning strike damage and structural tolerance necessary to observe the damage tolerance capability. Resistance of composite panels with metallic nanofilm under various strains was studied. It was found that resistance of the metallic nanofilm increased under strain. The voltage was found to be low; hence, an increase in current would help to reduce the damage on composite panels due to lightning strikes, and the same theory would be applicable to EMI. No EMI was absorbed or reflected in the nanofilm using the P-static test. When lightning strikes were applied to composite coupons, the resulting damage from the currents was reduced on those with metallic nanofilms.

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