10-15-04 -- WORKSITE PRIMARY SHOCK PROTECTION
WORKSITE PRIMARY SHOCK PROTECTIONThomas E. Glavinich, D.E., P.E.
The University of Kansas
The electric power industry recognizes the need to protect workers, aloft and on the ground, from dangerous voltages that can occur during construction and maintenance operations on overhead transmission and distribution lines. Current regulations, codes, and standards require the establishment of equipotential zones that use grounding and bonding to minimize the possibility that a worker is exposed to dangerous voltage differences. However, there is little direction available regarding how to establish these equipotential zones. Methods used to ground mobile construction equipment vary throughout the electric power industry and are often based on industry custom and local practice. Protecting workers on the ground needs to be standardized and based on a scientific approach that takes into account both the actual hazards and the physical conditions at the worksite.
This research project will produce a consensus industry standard for protecting linemen, groundmen, and equipment operators from “primary shock” hazards during overhead line construction and maintenance operations. The Institute of Electrical and Electronic Engineers (IEEE) defines primary shock as “a shock of a magnitude that may produce physical harm” such as ventricular fibrillation, respiratory tetanus, and muscle contraction. Originally, this project focused on grounding to protect workers on the ground. However, research into current industry practices indicated that isolation and insulation are also being used to protect workers both in lieu of and in conjunction with grounding at the worksite. As a result of these findings, the ECF Project Steering Committee expanded the scope of this project to include isolation and insulation as well as grounding.
Line workers face increasing daily hazards due to the changing transmission and distribution work environment. It is no longer enough to protect workers from accidental energization of the line on which they are working or accidental contact with an energized line. Higher voltages and load currents, more congested right-of-ways (ROW) including multi-circuit transmission corridors and underbuild on existing structures, and increasingly restrictive utility shutdown policies all result in dangerous induced voltages that must also be addressed. Complicating this issue is the fact that the type of work being performed, the electrical characteristics of the system that the work is being performed on, and the physical conditions at the worksite vary greatly and can have a significant impact on the dangers posed and protective methods used to mitigating those dangers.
Due to the size and complexity of the topic, this research project has been divided into three phases. Phase I, to be completed during 2004, involves establishing the need for better worker protection, investigating current industry practices, and developing a field testing program. Phase II will begin in 2005 and will include field and laboratory testing as well as computer simulations to evaluate current and proposed practices for protecting workers under varying site conditions. During Phase III in 2006, the research team will develop a recommended practice for protecting workers on the ground from primary shocks during overhead line construction and maintenance operations.