Lightning trip-out risk evaluation of a 220kV transmission line in Shiyan
The lightning trip-out accidents of Shiyan transmission lines occur frequently. The lightning parameters, lightning faults and geography of 220kV shi-xuan transmission line have been collected. The lightning striking simulation model has been built by using electromagnetic transient calculation software ATP-EMTP and multi-wave impedance model. The lightning withstanding level of tower and the lightning trip-out rate have been calculated. The actual operation of the transmission line has been considered in order to evaluate the risk of lightning trip-out. The results can provide guidance for the lightning protection of transmission linewhich locates in mountains.
Novel approach for determining spots of critical lightning performance along transmission lines
A novel approach is proposed for determining critical spots along transmission lines, concerning lightning performance. It takes into account two localized factors: stroke density and response of line structures to lightning currents. The methodology employs data supplied by lightning location systems and also information about line parameters in order to rank, by means of a severity index, the specific towers along line, which deserve protective actions. The procedure was applied to a real 230 kV line. The results, in terms of first ranked towers, were compared to the history of line outages, as indicated by a fault locator. The results were in very good agreement. This denotes the potential of the proposed approach for general application.
ABCD matrix analysis of propagation of gaussian beams through Kerr media
Abstract A new formalism and a nonlinear ABCD matrix, derived from the aberrationless theory of self-focusing, are introduced to treat the propagation of gaussian beams in materials with Kerr nonlinearity. The analysis of propagation of gaussian beams shows that the effect of the Kerr medium can be interpreted, to the first order in the beam power, as due to a lens and propagation over a negative distance. The latter effect has been named self-shortening. The formalism has been applied to find the optimal focusing condition for the maximum nonlinear effects and to the calculation of gaussian modes in resonators containing a Kerr medium.