Investigation of electric fields of EHV substations

60-Hz and 24-kHz capacitive and monopole probes and testing techniques were developed for full-scale and model ground level electric field strength measurements for EHV substations. A model of an existing 345-kV substation was designed and built. The model was energized using a three phase 24-kHz regulated source. Comparison of corresponding test points shows that the agreement between substation and model measurements is good. Large amounts of model test data can be taken in a short time. Energized scale models can be used in a substation design tool so that the electric field may be mapped and, if necessary, modified. A successful and useful predictive tool has been developed that can handle the three-dimensional complex substation electric fields. Further development will result in a widely available and flexible analog design tool.