Efficiently computing the electrical parameters of cables with arbitrary cross-sections using the method-of-moments (original) (raw)
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2017
The per-unit-length capacitance of sector-shaped cables has been shown to remain relatively constant when operating in power system frequencies (up to 1MHz) making it possible to approximate it using closed-form expressions with reasonable accuracy. Numerical evaluation of frequency dependent resistance R and inductance L parameters of these types of cables remains computationally expensive. In this paper, the method-of-moment (MoM) discretization of the proximityand skin-effectaware formulation known as the surface-volumesurface electric field integral equation (SVS-EFIE) is optimized and applied for extracting the R and L parameters of circular and sector-shaped cables. While the proposed method guarantees to provide reliable data by iteratively achieving a desired accuracy, it also increases the efficiency of the MoM significantly. This makes the proposed method a suitable candidate for electromagnetic transient programs where rapid and accurate computation of the electrical para...
ArXiv, 2013
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Journal of Control, Automation and Electrical Systems, 2017
A full computer-based methodology is proposed for electromagnetic transient simulations in power cables characterized by an arbitrary cross-section geometry. The frequency-dependent parameters of the cables are calculated using finite element method, and the three-phase cable modeling is carried out using modal decoupling and fitting techniques. The multiconductor representation of a sectorshaped cable is possible from the calculation of a constant and real modal transformation matrix, resulting four independent propagation modes (three phases and cable shield), which are modeled from the inclusion of frequency effect in the classic Bergeron method. The currents and voltages are expressed as a system of differential equations, which are presented as state equations and solved using numerical inte
Proximity-Aware Calculation of Cable Series Impedance for Systems of Solid and Hollow Conductors
IEEE Transactions on Power Delivery, 2014
Wide-band cable models for the prediction of electromagnetic transients in power systems require the accurate calculation of the cable series impedance as function of frequency. A surface current approach was recently proposed for systems of round solid conductors, with inclusion of skin and proximity effects. In this paper we extend the approach to include tubular conductors, allowing to model realistic cables with tubular sheaths, armors and pipes. We also include the effect of a lossy ground. A noteworthy feature of the proposed technique is the accurate prediction of proximity effects, which can be of major importance in three-phase, pipe type, and closely-packed single-core cables. The new approach is highly efficient compared to finite elements. In the case of a cross-bonded cable system featuring three phase conductors and three screens, the proposed technique computes the required 120 frequency samples in only six seconds of CPU time.
IEEE Transactions on Power Delivery, 2014
The availability of accurate and broadband models for underground and submarine cable systems is of paramount importance for the correct prediction of electromagnetic transients in power grids. Recently, we proposed the MoM-SO method for extracting the series impedance of power cables while accounting for skin and proximity effect in the conductors. In this paper, we extend the method to include ground return effects and to handle cables placed inside a tunnel. Numerical tests show that the proposed method is more accurate than widely-used analytic formulas, and is much faster than existing proximity-aware approaches like finite elements. For a three-phase cable system in a tunnel, the proposed method requires only 0.3 seconds of CPU time per frequency point, against the 8.3 minutes taken by finite elements, for a speed up beyond 1000 X.
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Abstruct-Radiated electromagnetic fields are produced by currents in cables or transmission lines interconnecting various circuits. An elegant method of computing the resultant electromagnetic field, produced by several radiating current elements, is given. The current in each radiating cable is first found from a time-domain simulation algorithm and this may be a steadystate or transient current. The radiated field is then calculated by assuming a radiating transmission line can be treated as a chain of short radiating dipoles. The problems associated with the calculation of the near-zone term at low frequencies and the overall response near the radiator are clarified. The proposed technique is fully evaluated and compared with other methods.
Modeling of Arbitrary Shaped Cables Using Novel Single Source Integral Equation Formulation
This paper proposes a novel method for calculation of frequency dependent parameters for any arbitrary shaped cable based on a new integral equations formulation and its Method of Moment solution. The proposed approach accurately considers both skin and proximity effects. The computation of series impedance matrix using this method is described for a sector-shaped cable example. The frequency domain impedance calculations are compared with alternative techniques such as finite element and sub-conductor methods. Time domain simulation results for open and short circuit terminations are also compared with sub-conductor technique.
2014
A Surface Admittance Approach For Fast Calculation of the Series Impedance of Cables Including Skin, Proximity, and Ground Return Effects Utkarsh R. Patel Master of Applied Science Graduate Department of The Edward S. Rogers Sr. Department of Electrical & Computer Engineering University of Toronto 2014 The accurate calculation of broadband series impedance of power cables is required to predict transients induced in power systems. Since modern power cables have complex geometries with hundreds of tightly packed conductors, existing techniques to compute their series impedance are either inaccurate or very slow. This thesis presents MoM-SO, a fast and accurate technique to compute the per-unit length impedance of cables made up of solid and hollow round conductors placed inside a tunnel in a multilayer ground environment. MoM-SO employs a surface-approach to solve for the impedance. In this approach, only fields on the boundaries of the conductors are discretized and calculated. As s...
2015
In this paper, we present a comprehensive study on the influence of proximity effects on electromagnetic transients in underground power cables. Existing simulators for electromagnetic transients (EMT) neglect proximity effects when computing cable parameters. It has been demonstrated that, in some scenarios, this approximation can result in significant errors on the predicted transients. The goal of this study is to identify the scenarios where proximity effects must be taken into account, and the error that one may incur if such effects are neglected. The study is performed using the recently-proposed MoM-SO method for the determination of cable resistance and inductance. MoM-SO accurately predicts skin, proximity, and ground effects over the frequency range of interest for transient analyses, with an accuracy comparable to time-consuming finite element calculations. The study considers cables of different type and geometry under multiple excitation scenarios. Results elucidate th...
2013 17th IEEE Workshop on Signal and Power Integrity, 2013
We present a fast and fully-automated algorithm to extract the series impedance of cables with round conductors, such as USB and HDMI cables. Our solution combines the method of moments with a surface admittance operator, and is much more efficient than a finite elements approach. Moreover, it is fully automated, owing to an adaptive scheme to automatically determine the discretization of the geometry in order to provide accurate results. Numerical tests on several types of cable demonstrate the excellent accuracy and speed of the proposed method.