A study on surge simulation techniques based on the numerical electromagnetic computation method and development of a multipurpose surge simulation code VSTL

Graphical user interface of VSTL

Fig.1 Graphical user interface of VSTL

Lightning surge analysis plays a major role in the prediction of overvoltage distributions due to lightning strikes. Conventional methods used for lightning surge analysis are based on circuit theory, and in the conventional methods, a calculation model is composed of lumped- and distributed-constant circuit elements. The circuit-theory-based calculation methods cannot be rigorously applied to surge problems involving three-dimensional structures such as towers and buildings. It has been already well known that the numerical electromagnetic field computation method, which solve Maxwell's equations directly, is an effective tool for such surge problems. The FDTD (finite difference time domain) method is advantageous over the other numerical electromagnetic field computation methods for treating intricately shaped conductors and electrical parameters and structures of the ground soil. However, since the FDTD method was developed mainly in the field of antenna and microwave analysis, it has been necessary to develop various calculation techniques for applying the FDTD method to practical lighting surge simulations.
We have developed a highly accurate method of modeling a thin wire such as an electric wire and the elements of a structure, since the consideration of thin wires is inevitable in lightning surge analysis. In addition, we have developed a technique for controlling the development speed of the return stroke current to simulate lightning strikes, and for representing lightning arresters and arcing-horn flashover phenomena with nonlinear characteristics.
Using the above technique, we have developed a multipurpose surge simulation code called VSTL (Virtual Surge Test Lab.) based on the FDTD method for practical use. As shown in Fig. 1, VSTL is equipped with a GUI (graphical user interface), which is useful for preparing three-dimensional calculation models more easily and showing calculated results. In addition, using VSTL, we have performed simulations of the potential rise of a transmission tower struck by lightning, the surge propagation of a bus in a substation, lightning-induced voltages on a distribution line, the transient potential rise of a grounding grid, and so on, and have confirmed the validity of the calculated results by comparing them with measured results or results calculated by other methods. VSTL is now widely used by electric power companies, universities and in industry.


Publications

[1] K. Tanabe, “A Method for Computational Analysis of Transient Resistance for-Grounding Systems Based on the FD-TD Method”, IEEJ Transactions on Power and Energy, Vol.120,No.8/9,pp1119-1126,2000
[2] T. Noda, nd S. Yokoyama, “Development of a General Surge Analysis Program Based on the FDTD Method”, IEEJ Transactions on Power and Energy, Vol.121,No.5,pp625-632,2001
[3] T.Noda, and S.Yokoyama, “Thin Wire Representation in Finite Difference Time Domain Surge Simulation”,IEEE Trans.on Power Delivery,Vol.22,No.5,pp.72-72,2002
[4] T.Noda,R.Yonezawa,S.Yokoyama,and Y.Takahashi, “Error in Propagation Velocity Due to Staircase Approximation of an Inclined Thin Wire in FDTD Surge Simulation”,IEEE Trans. on Power Delivery,2004
[5] T.Noda,A.Tatematsu, and S.Yokoyama, “Improvements of an FDTD-Based Surge Simulation Code and Its Application to the Lightning Overvoltage Calculation of a Transmission Tower”,International Journal of Electrical Power & nergy Systems,2007
[6]A. Tatematsu and T. Noda, “A Method for Avoiding Numerical Instability in FDTD-based Surge Simulations and Its Application to Representation of Thin Wires”,IEEJ Trans. PE,Vol. 129,No. 6,pp. 776-782,2009
[7]A. Tatematsu and T. Noda, “Development of a Technique for Representing Lightning Arresters in the Surge Simulations Based on the FDTD Method and Its Application to the Calculation of Lightning-Induced Voltages on a Distribution Line”,IEEJ Trans. PE,Vol. 130,No. 3,pp. 373-382,2010
[8]S. Matsuura, A. Tatematsu, T. Noda, and S. Yokoyama, “A Simulation Study of Lightning Surge Characteristics of a Distribution Line Using the FDTD Method”,IEEJ Trans. PE, Vol. 129, No. 10, pp. 1225-1232,2009
[9]A. Tatematsu, K. Yamazaki, K. Miyajima, and H. Motoyama, “A Study on Induced Voltages on an Aerial Wire due to a Current Flowing through a Grounding Grid”,IEEJ Trans. PE, Vol. 129,No. 10,pp. 1245-1251,2009
[10]T. Noda, “A Tower Model for Lightning Overvoltage Studies Based on the Result of an FDTD Simulation”,IEEJ Trans. PE, Vol. 127, No. 2, pp.379-388,2007

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(Fundamental Technology)

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