Electromagnetic shielding of a system computer in a 230-kV substation

The results are reported of a project designed to reduce the magnitude of transient high-frequency electromagnetic field disturbances near 230-kV line disconnect switches by structural shielding. A reduction in peak transient electric fields from 600 volts per meter to an equipment specification value of 1 volt per meter at the site of a large computer installation has been obtained. The transient field waveforms and measurement methods are described.