Monitoring and remediation of on-farm and off-farm ground current measured as step potential on a Wisconsin dairy farm: A case study

ABSTRACT

Ground current commonly referred to as “stray voltage” has been an issue on dairy farms since electricity was first brought to rural America. Equipment that generates high-frequency voltage transients on electrical wires combined with a multigrounded (electrical distribution) system and inadequate neutral returns all contribute to ground current. Despite decades of problems, we are no closer to resolving this issue, in part, due to three misconceptions that are addressed in this study. Misconception 1. The current standard of 1 V at cow contact is adequate to protect dairy cows; Misconception 2. Frequencies higher than 60 Hz do not need to be considered; and Misconception 3. All sources of ground current originate on the farm that has a ground current problem. This case study of a Wisconsin dairy farm documents, 1. how to establish permanent monitoring of ground current (step potential) on a dairy farm; 2. how to determine and remediate both on-farm and off-farm sources contributing to step potential; 3. which step-potential metrics relate to cow comfort and milk production; and 4. how these metrics relate to established standards. On-farm sources include lighting, variable speed frequency drives on motors, radio frequency identification system and off-farm sources are due to a poor primary neutral return on the utility side of the distribution system. A step-potential threshold of 1 V root mean square (RMS) at 60 Hz is inadequate to protect dairy cows as decreases of a few mV peak–peak at higher frequencies increases milk production, reduces milking time and improves cow comfort.

KEYWORDS:

• Ground current
• stray voltage
• uncontrolled electricity
• high-frequency voltage transients
• dirty electricity
• step potential
• PNEV
• dairy farm

Acknowledgments

We thank the farmer for providing us with information on animal health and milk yield and for allowing us to do this research on this Wisconsin dairy farm.

Declaration of interest

The authors alone are responsible for the content and writing of this article. Stetzer, Leavitt and Goeke are professional consultants who monitor, evaluate and mitigate ground current problems. Havas has no conflict of interest.

This research was approved by Trent University’s Research Ethics Board and consent to publish this information was obtained from the farmer involved in this case study.

Notes

¹ Voltage or currents do not stray. “Current will travel along the path of least resistance” (Ohm’s Law) and “current will take any and all paths” (Kirchoff’s Law).