All nuclear plant instrumentation connected at installation points to low-voltage power circuits will be exposed to electric fast transients induced by power switching and lightning. Unwarranted interruption of instrumentation due to transients may result in serious loss through bothersome activation of a plant's engineering safeguards. In this study, in situ responses of a digital wide-range neutron monitor is studied in terms of real-time disturbances during electric transients. Using correlation analysis, a systematic methodology between transient responses and steady-state electromagnetic emission spectra has been developed and justified to be useful for transient isolation. Moreover, results of various on-site approaches to improve the electromagnetic compatibility of safety-related instrumentation are discussed.