HEMP-Induced Transients in Transmission and Distribution (T And D) Lines

摘要

The corona effects on the early-time induced transients on the transmission and distribution (T and D) lines are calculated based on two different corona models. Three different sources of excitation of the lines are considered, which include a HEMP plane wave, a localized voltage source, and a current injected at a point on the wire. The induced current and charge are calculated and compared with some available experimental data and with the results of Baum's model. The results illustrate that the corona generally reduces the peak value of the induced current as much as 30% of the value and decreases the rate of rise by about 40%. The HEMP-induced stresses across dielectric insulators in some typical electric power systems are also calculated. The insulators that are considered are line supports in T and D line poles, and transformer bushings in distribution and power transformers. Different elevation and azimuthal angles of HEMP incidence with two different values of ground conductivity are considered. The HEMP-induced ''potential difference'' across the line support and air gap in the transmission lines and the HEMP-induced open-circuit voltage across transformer bushings are calculated. The ''potential difference'' across the line support and across the air gap can be as high as 7 MV. The rise time of the ''potential difference'' is about 110 ns, and the fall time is about 2 to 3 mu s. The open-circuit voltage across transformer bushings can be as large as few tens of MVs and the rise time is in the order of 100 ns and the fall time 800 ns. (ERA citation 11:001278)