A new approach to the measurement characterization of electromagnetic interference caused by substation transients has been developed. A data acquisition system for measurements has been designed and constructed for field use with a bandwidth capability exceeding 100 MHz. Measurements have been taken from staged operations in substations and the resulting data analyzed using specialized computer programs developed for this project. The measurement techniques are presented and the analysis procedures explained in detail. The transients caused by equipment operations in several substations have been studied resulting in an understanding of the expected or 'typical' amplitudes and frequencies of the resulting noise. Suggestions as to equipment tests and 'withstand' levels have been made. An appendix includes raw and analyzed data for research use.