Complaints related to contact voltage for pedestrians and animals have long been an area of concern and subjective interpretation for utilities, regulators, and the public.

  • Humans and animals have experienced electric shock in urban areas when they come in contact with objects that contain or are nearby faulty electrified wiring
  • Humans occasionally complain of perceptible tingling sensations while swimming in pools that have inadequate or degraded equipotential bonding connections
  • Dairy farms must be designed with electrical standards that provide reasonable confidence that animals are not exposed to voltages above their perception levels
  • Public Marinas and other areas with electrical service extending into bodies of water commonly post warning signs to discourage or dis-allow swimming in such locations

While not all of these conditions are lethal or detrimental to health or safety, it is better to err on side of caution and avoidance (when encountering a possible shock scenario) until trained or certified personnel can determine the cause and relative risk of such scenarios. If any of these situations or similar situations are encountered and you are unsure of the source of the shocking, it is advisable to take necessary steps to keep humans or animals away from the area of concern (best handled by calling local authorities for publicly accessible locations) and additionally contacting the local electric service provider so they can assess the situation.

Sources of stray and contact voltages range from induction of voltage onto metallic infrastructure--such as conduits, water pipes, and gas pipes--to unanticipated current paths created by grounding configurations and connection impedances. Although steady-state 60-Hz stray voltage and elevated NEV issues have been a long standing concern, the increasing use of nonlinear (or harmonics-generating) electronic equipment--such as variable-speed drives, personal computers, and residential appliances--is continually adding to these elevated voltage potentials. Additionally, momentary or transient neutral-to-earth voltage and its impact have become a more recent topic of study. In light of these developments, there is a need to establish a collaborative effort to standardize proper measurement protocols, to better understand the coupling issues related to stray voltages, and to evaluate cost-effective solutions. In particular, these efforts must encompass all aspects of stray and elevated voltages to include 60-Hz, proliferation of harmonic loads, and issues related to transient voltage loads.

Research Summary

Each year since 2004, EPRI research in this area has considered the most important concerns associated with elevated neutral-to-earth and metallic-object-to-earth voltages at human and at animal contact points by promoting consistent and repeatable assessment methodologies, sponsoring workshops, and creating a repository of case studies and general information. These and other project efforts are geared toward expediting problem identification and resolution.

The project results are distilled on this Web site to promote the widespread dissemination of research results where that information benefits affected parties. The areas where this Web site provides that information include:

  • Measurement equipment and protocols
  • Mitigation techniques and devices
  • Modeling and simulation approaches
  • Impacts on humans and animals
  • Approaches for understanding limits and levels of concern
  • Links to relevant industry information
  • Select case studies

Since the mid-1980s, EPRI has been assessing nuisance shocking related to contact voltages, beginning with elevated voltage potentials on gas pipelines, publications on shocking occurring at swimming pools, and comparisons of animal sensitivities to stray voltage. EPRI has sponsored testing on dairy cows, field investigations, laboratory testing, and power-system modeling to better understand the impacts of parametric variations on stray voltage levels. EPRI is extremely appreciative of the electric utilities that sponsored this research and of the organizations that have conducted credible human and animal physiological research in contribution to the industry's understanding of the subject matter.