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The asymptotic model is applied to analyze the high-frequency electromagnetic coupling problem of the multiconductor transmission lines (MTLs). To efficiently calculate the current of MTLs in the nonuniform electromagnetic field, an extended asymptotic model combined with matrix pencil method (MPM) is proposed in this article. In the proposed method, the complicated electric field is analytically expressed using an MPM signal model first. Then, considering the basic theory of the moment of method (MOM), the previous solving process of the asymptotic model is optimized in this article to adapt to the requirements of multiple calculations. Finally, the asymptotic model is extended to calculate the current excited by the equivalent plane wave component of the signal model with a good efficiency and accuracy. Moreover, calculating the transient response by the inverse fast Fourier transform (IFFT), several numerical examples with typical nonuniform electromagnetic fields are presented to validate the reliability of the extended asymptotic model.

Transmission lines are very important in electrical systems. High-frequency electromagnetic fields can couple to overhead lines. Once the wavelength of the high-frequency electromagnetic field is smaller than the height of the transmission line, the classic transmission line theory is no longer applicable. Although the traditional full-wave numerical algorithm can solve this problem, it is not efficient. Moreover, transmission lines often have multiple vertical ends and complex line layouts. In order to solve these problems, this article proposes a theoretical and effective method to solve the coupling of high-frequency electromagnetic fields with partial discontinuity transmission lines with scatterers in the presence of lossy ground. The asymptotic method with high computational efficiency is adopted, and the concept of scatterer is brought into the asymptotic method to consider more complex circuit structures. Numerical examples verify the accuracy and efficiency of the proposed method.

Due to the difficulty in collecting samples of certain effect levels, the class imbalance problem is a challenging issue in vulnerability assessment. The class imbalance problem would cause deviation of likelihood function and thus deviate the result of vulnerability assessment. Conventional assessment method ignoring it would lead to over- or under-estimation. In this article, we propose the improved kernel density estimation (IKDE) to address this issue. The proposed method first calculates the probability density function of each effect level sample. Then, the spatial characteristics are introduced in the likelihood function to reduce the impact of the class imbalance problem. The parameters in IKDE are determined by Markov Chain Monte Carlo and the probabilities of each effect level can be obtained at last. Through simulations with different class imbalance degrees and sample sizes, we illustrate the effectiveness of the proposed IKDE. Finally, a case study is carried out to assess the vulnerability of 10 kV distribution transformer excited by nanosecond electromagnetic pulse.

In this article, we propose a nonintrusive pulsed radiated susceptibility testing approach based on the long-line crosstalk setup. The objective is to reproduce the pulsed electromagnetic field coupling effect for wiring harness systems. The proposed test setup explores the crosstalk between parallel wires and imposes an additional pulse-driven wire to couple the interferences onto the wire under test. The transmission line model is exploited to represent both crosstalk and the pulsed field coupling process, demonstrating that equivalence can be achieved within a limited clearance time in general, provided the driven wire exceeds a critical length. In addition, rigorous equivalence can be obtained for particular incidences, such as broad-side illumination and end-fire excitation, under the condition of matched auxiliary equivalent terminals. Comparing this to state-of-the-art pulse injection approaches, the crosstalk-based testing method ensures the exact reproduction of field coupling effects without necessitating driven pulse predistortion, this characteristic underscores its robustness for pre-compliance pulsed field radiated susceptibility testing. Additionally, by considering a canonical double exponential interference, a pilot experiment is conducted to verify the equivalent rationale and feasibility of the proposed approach.

Large-scale pipeline networks may be subject to wide-area and spatially nonuniform external electromagnetic interference. This paper presents a generalized and efficient algorithm for the calculation of inductive and conductive coupling to pipeline networks based on the two-port equivalent circuit. In the modified transmission line model of the pipeline, the external inteference are characterized by using only longitudinal voltage sources. In addition, the nonlinear polarization of coating breakdown is incorporated into the circuit model of the network. The linear pipe segments can be independently reduced to the equivalent-pi circuit with analytical parameters, which enables model order reduction of the network. Such techniques can be applied to arbitrary nonuniform excitation fields. Several test cases are used to illustrate the response characteristics of pipelines excited by interference with different spatial patterns, including geomagnetic disturbances and HVDC earth return currents.

This article investigates how the accuracy of fault location estimated from a transmission line's natural frequencies is affected by imperfect modeling of HVDC power-converter stations. These systems include a large number of devices each with specific frequency-dependent characteristics, as filters, reactors and surge protection systems. While it is well-known that location errors may ensue from inaccurate termination models, it is not clear to what extent location accuracy is affected when neglecting one or more of these devices. Results show significant differences depending on the kind of transmission line and the reactor inductance. Including reactors is found not to completely avoid errors, proving the need to take into account the reactive behavior of the converter, which strongly varies according to the HVDC technology. A notable source of errors is level repulsion between station and line resonances, a phenomenon observed when the converter station presents self resonances, e.g., due to DC filters and stray capacitances in reactors. Significant loss of sensitivity to the fault position is found in these cases, impairing fault-location resolution. The first, or dominant, natural frequency of the line is more strongly affected by all these phenomena, suggesting that the standard choice of using the dominant resonance may not be an optimal strategy. Higher-order resonances are instead found to be more robust against inaccurate converter models, and appear to be more suitable for accurate fault location in case of uncertainties about the converter model.