A Complete Electrical Shock Hazard Classification System and Its Application

The Standard for Electrical Safety in the Workplace, National Fire Protection Association (NFPA) Standard 70E, and the relevant Occupational Safety and Health Act electrical safety standards evolved to address the hazards of 60-Hz power that are faced primarily by electricians, linemen, and others performing facility and utility work. This leaves a substantial gap in the management of electrical hazards in research and development (R&D) and specialized high-voltage and high-power equipment. Examples include lasers, accelerators, capacitor banks, electroplating systems, induction, dielectric heating systems, etc. Although all such systems are fed by 50/60 Hz ac power, we find substantial use of dc electrical energy and the use of capacitors, inductors, batteries, and radio frequency power. The electrical hazards of these forms of electricity and their systems are different than for 50/60 Hz power. Over the past 18 years, there has been an effort to develop a method for classifying all of the electrical hazards found in all types of R&D and utilization equipment. Examples of the variation of these hazards from NFPA 70E include high voltage can be harmless if the available current is sufficiently low; low voltage can be harmful if the available current/power is high; high-voltage capacitor hazards are unique and include severe reflex action, effects on the heart, and tissue damage; and arc flash hazard analysis for dc and capacitor systems is not provided in existing standards. This work has led to a comprehensive electrical hazard classification system that is based on various research conducted over the past 100 years on analysis of such systems in R&D and on decades of experience. Initially, national electrical safety codes required the qualified worker only to know the source voltage to determine the shock hazard. Later, as arc flash hazards were understood, the fault current and clearing time were needed. These items are still insufficient to fully characterize all types of electrical hazards. The new comprehensive electrical hazard classification system uses a combination of voltage, shock current available, fault current available, power, energy, and waveform to classify all forms of electrical hazards. Based on this electrical hazard classification system, many new tools have been developed, including work controls for these hazards, better selection of PPE for dc work, improved training, and a new Electrical Severity Ranking Tool that is used to rank electrical accidents and incidents with various forms of electrical energy.