Transient Voltages on Grounding Grids buried in Stratified Soils

2020 ◽  
Author(s):  
Anderson Anderson R. J. de Araújo ◽  
Walter L. M. de Azevedo ◽  
José Pissolato Filho ◽  
Jaimis S. L. Colqui ◽  
Sérgio Kurokawa
Keyword(s):  
Power Systems ◽  
Electric Circuit ◽  
Lightning Strikes ◽  
Vector Fitting ◽  
Full Wave ◽  
Vertical Electrode ◽  
Radiation Theory ◽  
Lightning Discharges ◽  
Grounding Grids ◽  
Transient Voltages

Grounding grids (GG) play a fundamental role in the protection of personnel and prevention of damages in equipment during surge transients on substations caused by lightning discharges on power systems. In this context, a precise GG modeling must consider several factors such as the arrangement and the soil compacted in stratified layers. This paper proposes a lumped approach for GG buried in several stratified soils to compute the transient node voltages when subjected to lightning strikes. The vertical and horizontal electrodes are modelled separately by lumped circuit approach. The vertical electrode impedances buried in a stratified soil are computed by the numerical Method of Moments (MoM) in the full-wave electromagnetic software FEKOR , directly in frequency domain, and then, an electric circuit is obtained by the Vector Fitting technique. The horizontal electrodes are modelled based on the electromagnetic radiation theory, where each segment of the electrode can be regarded as a lamental currentcarrying conductor. Lightning currents of fast and slow-front waveforms, are employed in the simulations. Results show that when stratified soils are considered, the differences of the transient voltage peaks, in comparison with the ones calculated for the homogeneous soil is more pronounced as the thickness of soil decreases.

scholarly journals Computation of Lightning Voltage Surges on Tall and Conventional Transmission Towers

2020 ◽  
Author(s):  
Anderson R. J. de Araújo ◽  
Claudiner M. de Seixas ◽  
Bamdad Salarieh ◽  
Sérgio Kurokawa ◽  
Behzad Kordi
Keyword(s):  
Power Systems ◽  
Forest Canopy ◽  
Electric Circuit ◽  
Voltage Response ◽  
Transmission Tower ◽  
Lightning Strikes ◽  
Grounding System ◽  
Vector Fitting ◽  
Transmission Towers ◽  
The Time Domain

Transmission tower modelling is very important to assess the electromagnetic transient caused by lightning strikes in power systems. In this context, conventional tower models are very well studied in the literature. However, there are few studies on tall transmission towers which have been receiving great attention recently due to their own characteristics. Tall transmission towers are built on river crossings and/or over dense forest canopy to reduce environmental impact in these areas. In this paper, the voltage surge caused by an incidentlightning at the top of the conventional and tall towers are determined. For both structures, a lumped electric circuit approximated by Vector Fitting technique is proposed which takes into account the tower-footing grounding system buried in different homogeneous soils. The results show a clear difference in the time domain voltage response for the conventional and tall transmission towers which is more pronounced as the soil resistivity increases and/or the tower becomes taller.

scholarly journals Grounding System Modeling and Evaluation Using Integrated Circuit Based Fast Relaxed Vector Fitting Approach, Considering Soil Ionization

2020 ◽  
Vol 10 (16) ◽  
pp. 5632
Author(s):  
Maziyar Fakhraei ◽  
Mehrdad Mahmoudian ◽  
Eduardo Manuel Godinho Rodrigues
Keyword(s):  
Integrated Circuit ◽  
System Modeling ◽  
Model Verification ◽  
Lightning Strikes ◽  
Grounding System ◽  
Vector Fitting ◽  
Grounding Grids ◽  
Electro Magnetic ◽  
Soil Ionization ◽  
System Frequency

Since high voltage transmission line towers or wind turbines structures are installed in high-altitude areas, it is essential to achieve a high overvoltage protection system against direct and indirect lightning strikes collisions. The lightning current must be discharged quickly into the protective earth, to prevent the dangerous over-voltages formation and define a reference voltage node. This paper presents a novel model to assess the behavior of the grounding system, based on Pocklington integral equations under lightning magnetic fields and variations in soil ionization, in which an explicit circuit-based vector fitting RLC admittance branches are proposed. The frequency-dependent behavior of grounding system frequency response and soil ionization effect is modeled in time domain, straightly to implement into the electro-magnetic transient program (EMTP). The model verification contains horizontal, vertical, and their combinations of grounding grids to represent the complete investigations under lightning strikes. The harmonic impedance mathematical formulations and principles are derived based on a rational function, that could be applicable on ground potential rise (GPR) investigation.

scholarly journals Computation of Transient Voltages on the Interconnected Grounding Grids

2020 ◽  
Author(s):  
Walter Luiz Manzi de Azevedo ◽  
Anderson Ricardo Justo de Araújo ◽  
José Pissolato Filho
Keyword(s):  
Transmission Line ◽  
Power Plants ◽  
Electromagnetic Transients ◽  
Electrical System ◽  
Reliable Operation ◽  
Natural Conditions ◽  
Lightning Strikes ◽  
Grounding Grids ◽  
Transient Voltage ◽  
Transient Voltages

Grounding grids play a fundamental role to provide safety during electromagnetic transients and reliable operation of any electrical system under normal conditions. In this context, when lightning strikes a transmission line, surge currents will propagate to the electrical substations where grounding grids must dissipate these impulsive currents into the soil. Grounding grids are composed of horizontal bars welded with vertical forming a large mesh. Additionally, the interconnected grids are largely employed to guarantee safety for personnel and equipment in facilities. Due to several natural conditions, horizontal bars can be damaged and compromise the performance of the grounding grid in power plants. In this paper, transient voltages are computed for whole and damaged grids when lightning strikes a transmission line. Results have shown that there is a difference in the transient voltage peaks in these two conditions. To decrease these voltages, vertical rods are installed in the border of the grounding grids, which has been shown as an effectivesolution to lower these voltage peaks in the damaged grounding grids.

scholarly journals First ground-based observations of sprites over southern Africa

2018 ◽  
Vol 114 (9/10) ◽  
Author(s):  
Stanislaus Nnadih ◽  
Mike Kosch ◽  
Peter Martinez ◽  
Jozsef Bor
Keyword(s):  
South Africa ◽  
Southern Africa ◽  
Dielectric Breakdown ◽  
Electrical Discharges ◽  
Lightning Strikes ◽  
The World ◽  
Lightning Discharges ◽  
Northern Cape ◽  
Cloud To Ground Lightning ◽  
Peak Value

Sprites are the optical signatures of electrical discharges in the mesosphere triggered by large lightning strikes associated with thunderstorms. Since their discovery in the late 1980s, sprites have been observed extensively around the world, although very few observations of sprites from Africa have been documented in the literature. In this paper, we report the first ground-based recorded observations of sprites from South Africa. In 2 out of the 22 nights of observations (11 January and 2 February 2016), about 100 sprite elements were recorded from Sutherland in the Northern Cape, comprising different morphologies (carrot (55%), carrot/column (11%), unclassified (21%), column (13%)). The sprites were triggered by positive cloud-to-ground lightning strikes, which had an average peak value of ~74 kA and were observed at distances from ~400 km to 800 km. The estimated charge moment change of the lightning discharges associated with these events was in agreement with the threshold for dielectric breakdown of the mesosphere and correlates well with the observed sprite brightness.

scholarly journals Analysis of the Incidence of Direct Lightning over a HVDC Transmission Line through EFD Model

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 555 ◽  
Author(s):  
Ednardo Rodrigues ◽  
Ricardo Pontes ◽  
João Bandeira ◽  
Victor Aguiar
Keyword(s):  
Finite Elements ◽  
Electric Field ◽  
Power Systems ◽  
Transmission Line ◽  
Lightning Strikes ◽  
Shielding Failure ◽  
Hvdc Transmission ◽  
Hvdc Line ◽  
Four Levels ◽  
Electrogeometric Model

HVDC systems are becoming more common worldwide, specially in Brazil, since the adoption of such system for Itaipu’s hydroelectric complex in the 1980’s. Today, the country has the Xingu-Estreito bipole, with length of 2375 km. This system crosses a region with high lightning incidence, a phenomenon which causes faults in power systems. The most widely used model for the positioning of the arrestor cables over a transmission line is the electrogeometric model. This model, however, does not take into account the different potentials over the structure’s surface, and therefore presents significant inaccuracies when assessing the risk of lightning strikes on structures such as a HVDC line. This work then used the Electric Field Deflection (EFD) model with the aid finite elements. Four levels of lightning are assessed (I, II, III and IV), with current peaks of 3.9, 5.4, 10.1 and 15.7 kA. It was verified that the positive pole tends to attract most of the lightning with shielding failures width (SFW) of 12, 8, 4 and 0 m. It was then proposed to move the arrestor cables horizontally. The study indicates that this horizontal shifting of the cables in 5 and 8 m toward the side with larger chance of direct incidence reduces the shielding failure widths in 50% for peak current of 3.9 kA and almost eliminates the strikes for lightning with peak currents of 5.4, 10.1 and 15.7 kA.

Special Issue “Lightning discharges and their effects on power systems and structures” (SIPDA 2017)

2019 ◽  
Vol 177 ◽  
pp. 105978
Author(s):  
Fridolin Heidler ◽  
Alexandre Piantini ◽  
Marcos Rubinstein ◽  
Qing Yang
Keyword(s):  
Power Systems ◽  
Special Issue ◽  
Lightning Discharges

scholarly journals Calculation of lightning surges on the high voltage lines. Case of 220 kV line: Ngo -Brazzaville in Congo

2017 ◽  
Vol 6 (1) ◽  
pp. 13
Author(s):  
Rodolphe Gomba ◽  
Alphonse Omboua
Keyword(s):  
Power Lines ◽  
Protective Equipment ◽  
Worst Case ◽  
Lightning Strikes ◽  
Lightning Current ◽  
Wave Forms ◽  
Lightning Discharges ◽  
Voltage Wave ◽  
High Level ◽  
Insulation Coordination

The importance of line Ngo-Brazzaville (220 kV, 207 km) requires operators to avoid cuts that can increase the risk of instability. We see it is quite rare that a storm that occurs in areas crossed by this line will not cause triggering. Note that due to lightning discharges are the main causes of unscheduled outages of Congo's power lines; we ignore this during the peak values of voltage wave forms that result. In regions with high level keraunic like Congo, reducing insulation failures due to lightning is a concern in the management of overheads lines. This article clarifies the peak values of the voltages that can be achieved on the network in order to build the operators as to the precautions on the insulation coordination of protective equipment related to lightning. For these calculations surge of atmospheric origin (case of lightning), we considered the bi-exponential function and Heidler function for modeling the wave of the lightning current. This methodology led us to specially treat the effects of direct lightning strikes that constitute the worst case because they generate most destructive shock wave that indirect lightning strikes.

scholarly journals Real-Time Flexibility Assessment for Power Systems with High Wind Energy Penetration

Mathematics ◽  
2021 ◽  
Vol 9 (17) ◽  
pp. 2056
Author(s):  
Anna Glazunova ◽  
Evgenii Semshikov ◽  
Michael Negnevitsky
Keyword(s):  
Power Systems ◽  
Wind Energy ◽  
Real Time ◽  
Renewable Energy Sources ◽  
Electric Circuit ◽  
Critical Issue ◽  
Electric Power System ◽  
Electricity Production ◽  
High Wind ◽  
Operational Conditions

To reduce the reliance on fossil fuel-based generation, many countries expand the use of renewable energy sources (RES) for electricity production. The stochastic and intermittent nature of such sources (i.e., wind and solar) poses challenges to the stable and reliable operation of the electric power system (EPS) and requires sufficient operational flexibility. With continuous and random changes in the EPS operational conditions, evaluating the system flexibility in a standardized manner may improve the robustness of planning and operating procedures. Therefore, the development of fast algorithms for determining system flexibility is a critical issue. In this paper, the flexibility of the EPS with high wind energy penetration is calculated in real time. In this context, the EPS flexibility is understood as the ability of the system to maintain a balance under irregular and short-term active power variations during a specified time by using the flexibility resources. The EPS flexibility calculation relies on a deterministic method developed to qualitatively and quantitatively assess the EPS readiness to changes in load. Accurate wind power forecasts and the observance of the electric circuit law when solving the optimization problem allow for determining the actual value of the EPS flexibility during a considered time.

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