When OSHA updated 29 CFR 1910.269 and merged almost all of its requirements with 1926 Subpart V, the requirement to protect employees from step potential was enhanced. In the months following the publication of the final rule, this change was rarely mentioned in the major webinars conducted by several prominent utility industry groups, so I want to take this opportunity to cover what you need to know.
First, let’s talk a bit about the basic fundamentals of Ohm’s law and Kirchoff’s law of current division in order to ensure you understand the seriousness of step potential hazards. Ohm’s law states that electricity will take any and all conductive paths, and Kirchoff’s law of current division states that the amount of current flow is dependent on the resistance and impedance in the current path.
As I travel around and conduct training, I find that many electric utility employees – much like me in the 1970s – do not understand these and other basic laws of physics that determine the number of hazards we face. The human body is not much more than a 1,000-ohm resistor when put into an electrical circuit. If a human body is placed in an electrical path/circuit, the amount of electricity that enters the body is about 50 volts AC. During this type of occurrence, the soles of normal work boots and shoes will provide an employee a small amount of protection, but if the employee were to kneel down and touch a vehicle grounded to a system neutral, or place a hand on a grounded object, the amount of protection would be significantly reduced.