Arrester Protection of High-Voltage Stations Against Lightning

1. A graphical method for evaluating the effect of nonstandard lightning surge voltages on equipment insulation has been presented and applied in the course of the study. The method is considered to be sufficiently accurate in measuring the relative effect of surge voltages to be extremely useful in such a study. The method is simple to understand and very easy to apply to surge evaluation. 2. Typical station configurations were studied at several system voltage levels and in each case the equipment insulation levels and lightning arrester ratings commonly used were employed. 3. The results of the study are summarized in Table V where suggested lightning arrester locations are indicated for the 16 cases that were studied and discussed in detail earlier. The locations suggested for lightning arresters represent, in some cases, greater separation distances from transformers than recommended heretofore. The study has assumed perfect shielding of the station from direct lightning strokes and that surges originate at a point 1/ 2 mile from the station. It must be pointed out that considerations of switching surge overvoltages, such as may occur upon deenergization of a transformer, might require the location of arresters between the circuit breaker and transformer. It is also to be pointed out that the study has considered voltages occurring in the station and has not treated the problem of protecting the incoming line side of the circuit breaker when in the open position. 4.