A Time-Domain Multiport Model of Thin-Wire System for Lightning Transient Simulation

In order to analyze the lightning transient of a thin-wire system, a time-domain method of reducing the thin-wire conductor system into an equivalent active multiport network based on the partial-element electric-circuit model is presented in this paper. A modified-mesh-current (MMC) approach is developed, uses node charge and mesh current as its variables, and takes into account both capacitive coupling and inductive coupling among conductors. Equations given by MMC are expressed in a state-space form. These equations are reduced to an active multiport network model using the trapezoidal scheme. The active multiport network is described by a constant-input-conductance matrix and a vector of currents that are updated using passed values. The multiport network can easily interface with linear and nonlinear components in an electromagnetic transient program. Since the proposed method requires only one-time calculation of the inverse of the system matrix, it is more efficient in comparison to the conventional full-wave method in the frequency domain. For a large system, well-established model-order-reduction techniques can be applied to the MMC formulation to reduce it to a small scale one. The proposed method is validated by comparing its results with NEC-calculated ones and published field measurements. Finally, the method is used to simulate two lightning-strike scenarios.