Ebrahim A. Badran

A phase-controlled STATCOM benchmark model for power system studies using ATPdraw

This paper introduces a detailed model for the inverter-based shunt reactive power compensator. The proposed model of the STATic COMpensator (STATCOM) consists of two six-pulse converters connected in series on the ac side. The phase control technique is implemented. The main parts of the compensator system are modeled as separate parts. So, the model can be used as a benchmark model for power system studies including the STATCOM using the ATPdraw version of the ElectroMagnetic Transients Program (EMTP-ATP). The proposed model verification has been undertaken by the use of published results..

Investigation of Lightning Electromagnetic Fields on Underground Cables in Wind Farms

Due to the current spreading of wind farms all over the world and their vulnerability to lightning strikes, it is important to investigate the lightning electromagnetic transients in wind farms. Underground cables are one of the essential parts in wind farms that link the turbines with the electrical grid. This paper investigates how the ground conductivity and relative permittivity, struck wind tower position, and rise time of lightning current influence the lightning electromagnetic fields impinging the underground cable sheath. The three-dimensional finite-difference time-domain method is implemented for this study. The lightning current through the cable sheath and its associated electric field can be effectively mitigated by connecting the grounding systems of the wind towers by underground bare wires called as counterpoise. Accordingly, the mitigation effect of counterpoise on the lightning current through the sheath and its associated electric field is also investigated. The results show that the lightning current through the cable sheath and its associated electric field is higher with lower ground conductivity. Moreover, it is revealed that the effect of both ground permittivity and struck wind tower position on the associated electric field and the sheath current is dependent on the ground conductivity.

FDTD Calculation of Transient Electromagnetic Fields in the Grounding System of Wind Towers Due to Direct Lightning Strikes

Lightning protection system (LPS) for wind power generation has become an important public issue due to greatly increasing installations of wind turbines (WTs) worldwide. Grounding system is one of the most important components required for appropriate LPS for WTs. Although the finite-difference time-domain (FDTD) method for solving Maxwells equations is difficult for computing earth potential rise (EPR) and transient grounding resistance (TGR), this method is used in this paper to compute EPR and TGR for different configurations of the grounding system of WTs because FDTD method can efficiently deal with the three-dimensional geometrical configurations of an investigated structure unlike electromagnetic transient programs (EMTP).

Influence of Highly Resistive Ground Parameters on Lightning-Induced Overvoltages Using 3-D FDTD Method

It is important for the proper insulation design of the distribution system that lightning-induced overvoltages ( LIOVs) are accurately computed. This paper investigates the impact of ground resistivity, considering wide range up to 20 kΩm, on LIOVs impinging an overhead line due to nearby return stroke using the three-dimensional finite difference time domain (3-D FDTD) method. The investigation considers two values of both ground permittivity as well as the rise rate of lightning current. Subsequently, it is inferred that the influence of both ground permittivity and rise rate of lightning current on the peak values of LIOVs depends on the ground resistivity. Furthermore, horizontal conduction and displacement current densities are also calculated on the ground surface under the line to analyze the behavior of ground surface impedance. Consequently, it is deduced that the behavior of the impedance changes from inductive to capacitive at high values of ground resistivity, thus increasing the time to the peak value of LIOVs. The peak values of LIOVs computed using the 3-D FDTD method are compared with those calculated using Darvenizas formula. It has been revealed that this formula considerably underestimates the peak values of LIOVs at high values of ground resistivity. Thereby, an interpretation is presented for the reason of this underestimation from an electromagnetic perspective. Accordingly, Darvenizas formula is appropriately modified to improve the computation accuracy.

Computation of Peak Lightning-Induced Voltages Due to the Typical First and Subsequent Strokes Considering High Ground Resistivity

It is essential that the insulation system of the overhead distribution lines should be properly designed to ensure their immunity against lightning-induced overvoltages (LIOVs) caused by nearby return strokes. Therefore, accurate calculation of the peak values of LIOVs is important for the insulation design. In this paper, a formula is proposed to calculate the peak values of LIOVs for both first and subsequent strokes. The typical waveforms of the first and subsequent return strokes are adopted for this study considering a wide range of ground resistivity, from 0.25 to 20 k

A detailed model for the STATCOM using ATPdraw

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An ANN-Based Approach for Lightning-Caused VFT Detection in GIS

m. The 2-D finite-difference time-domain method associated with the Agrawal coupling model is employed for the calculation of LIOVs. In addition, the effect of ground permittivity on the peak values of LIOVs is also investigated. Finally, the proposed formula is applied to calculate the annual number of flashovers per 100 km of the overhead line.

Induced Voltages on Overhead Line by Return Strokes to Grounded Wind Tower Considering Horizontally Stratified Ground

This paper introduces a detailed model for the static compensator (STATCOM). The proposed model consists of two six-pulse converters connected in series on the ac side. The dc sides of the two converters are connected in parallel and share the same dc capacitor. The phase control technique is implemented. The main parts of the compensator system are modeled as separate parts. So, the model can be used as a benchmark model for the STATCOM using the ATPdraw of the electromagnetic transients program (EMTP-ATP). The proposed model verification has been undertaken by the use of published results.

Enhanced fault ride through performance of self-excited induction generator-based wind park during unbalanced grid operation

This paper introduces an artificial neural network (ANN) approach for the detection and identification of lightning-caused very fast transient (VFT) in gas insulated substation (GIS). VFT in GIS can be due to faults, lightning and switching operations. VFT in GIS has to be located and classified as soon as possible to start the processes of reconfiguration and restoration of the normal power supply. A practical case study is investigated in Talkha 220-kV GIS which represents a critical generation point in the Egyptian Electric Power Network. The layout of the Talkha 220-kV GIS is discussed and modeled using ATP/EMTP. The ANN-based approach is built and trained. Finally, the proposed approach is tested using bolt ground faults, high impedance faults, and lightning on the connected transmission lines. The results ensure the success of the proposed approach to classify and discriminate the faults and the lightning-caused VFT.

Analysis and Suppression of Back-Flow Lightning Surges in Onshore Wind Farms

Wind power plants are one of the most widespread sources of electric energy during the last few decades. Wind towers are quite often exposed to lightning strikes due to their tall height and long blades. In this paper, the lightning-induced voltages (LIVs) on a three-phase overhead line are computed for both first and subsequent strokes to a nearby grounded wind tower using the three-dimensional finite-difference time-domain method with homogeneous and horizontally stratified grounds. The horizontal electric fields are computed on the line and on the ground surface considering the transient grounding and characteristic impedances of the struck wind tower. The impact of the existence of wind tower on LIVs and horizontal electric fields is illustrated by removing the tower (i.e., return stroke to the ground surface). Finally, the influence of ground permittivity on the peak values of LIVs is investigated.