As a power engineer and manager of power quality, EMF and stray voltage issues at a large investor owned electric utility in the Mid-Atlantic region, I've been involved in my own share of stray voltage investigations over the years and have thus taken a great interest in the ongoing issues at our neighboring utility cited in Mr. Smith's recent accounts. As a result of the ongoing issues in Mr. Smith's area, a local stray voltage ordinance was recently passed and there has been talk of statewide legislation being introduced. These recent attempts to regulate stray voltage have come about due to the highly emotionally charged environment and without sound technical or scientific basis. Added to the confusion have been the opinions of some apparent stray voltage experts that have suggested the need for radical changes to the infrastructure of electric utilities - changes that will not likely resolve many of the stray voltage cases that exists and will only lead to significantly higher costs to utility consumers.
While some of the simple tests identified in your response will help determine if the problem is on premise or not, they will not definitively point to the cause of the problem as being with the utility. Stray voltage, being technically a result of stray or inadvertent current flow in the earth or grounding path, typically involves numerous complex issues of bonding and grounding related to both on premise and off premise systems and facilities including those of non-electric utilities and neighboring properties.
Mike Holt's Comment: I agree that stray voltage can be the result of on premises and off premises conditions including those of non-electric utilities and neighboring properties. On way to determine that the elevated voltage on metal parts is caused by the electric utility is to simply measure the voltage of the utility secondary neutral (disconnected from the meter) to earth. If the elevated voltage is still there, then the issue is most likely related to the electric utilities primary neutral. If the voltage on the secondary neutral is no longer elevated, then the cause is probably not from the electric utility primary neutral.
Take for example,
one case of ours involving a neighbors abandoned well piping system that was serving
as a conductive path for current and voltage when a deteriorated Romex cable made
contact with the piping in their basement. The result was that the earth in the
vicinity of the abandoned well and a neighbors pre-fabricated hot tub were energized
at potentially life threatening voltage and current. When the hot tub owner made
contact between his un-bonded paving stone patio surface that the hot tub had
been installed upon and the grounded water surface, a ground path was made for
The problem with
hot tubs and stray voltage may not be totally coincidental. Consider that a hot
tub is really just a very small swimming pool. However, because hot tubs are generally
a pre-fabricated product listed by UL, the National Electrical Code really only
addresses the supply connection aspects of its installation. Whereas, the installation
and construction of a swimming pool requires that all metal objects near the pool,
and especially the steel reinforcing placed in the concrete pool decking, be bonded
to the pool grounding system no such requirement exists for a concrete or other
Mike Holt's Comment: The bonding requirements of pool equipment [680.26] does not remove stray voltage, it just masks it so people don't notice it. The bonding requirements in the NEC for spas and hot tubs are the same as for swimming pools [680.42(B)]. However, because pre-fabricated products are placed on concrete that can't be bonded to the spa/hot tub, the stray voltage can't be masked. Let be sure we understand that the bonding requirements of the NEC [680.26] is intended to reduce voltage gradients (mask stray voltage) in the pool area, not assist to clear a ground fault.
We've seen these problems in a number of hot tub installations and once the owner establishes a bond between the steel reinforcing in the concrete decking and the premise grounding system, occurrences of stray voltage are dramatically reduced.
Mike Holt's Comment: The stray voltage is not removed. The steel in the concrete is now energized to the stray voltage level; therefore the difference of potential between the metal parts of the spa or hot tub is reduced to a value below the perception level. But the voltage is still there. All one has to do to prove this, is to measure the voltage from the metal parts to the earth a few feet away from the concrete.
This is not to say that stray voltage issues are limited to hot tub installations alone. We've seen the well-intended but poorly coordinated efforts of others as the source of some problems. For instance, take a natural gas, petroleum or water pipeline constructed of cathodically protected metal piping installed in a longitudinal occupancy with electric facilities over a great distance. This arrangement can cause a capacitive electric charge to be developed on the insulated pipe over its distance. If intentionally or inadvertently grounded, this trapped charge is allowed to find a path to earth possibly creating a voltage gradient around the point of earth contact. Now place a neighbors well grounded swimming pool and electrical service adjacent to the where the pipeline has come into contact with earth and stray current will try to flow between the pipeline and the premise and utility grounding systems. Potentially hazardous current and voltage conditions may result. Providing a low impedance bonding path between both grounded systems reduces the levels of stray voltage to virtually imperceptible levels.
And of course, other conditions in both the customer's premise and the facilities of the utility may give rise to the inadvertent flow of ground current. Some of these causes include reversed neutral and ground connections in premise electrical wiring systems, deteriorated neutral conductors in the utilities overhead or underground primary distribution system or the low voltage service conductors to residences or the customer owned service cable, unbalances in the utility distribution system due to load or defective voltage regulating equipment, and possibly 3rd harmonic currents arising out of having a large population of lightly loaded single phase distribution transformers at very light load conditions.
Deficiencies in a utilities overhead primary multi-grounded neutral system are generally not a major contributing factor due to the multiplicity of neutral current paths and bonding with the grounding systems of other non-electric utility systems that may occupy the same pole structures.
Mike Holt's Comment: Greg, you do more of these investigations than I do, so I'll not argue your comment that "Deficiencies in a utilities overhead primary multi-grounded neutral system are generally not a major contributing factor". I'll not argue that stray voltage can be cause by many reasons other than the electric utility. My point is that when it is caused by the utility (we measure the voltage from the secondary neutral to ground), how do they respond? The Power Quality department of the electric utility has the resources to determine the cause of the stray voltage. It's really not that hard to determine if it's cause by the premises wiring, the neighbor, or the utility system. But will the utilities legal department or the bean counters allow them to solve the problem if it's utility produced?
Finally, we continue to watch with great interest the ongoing debate and development of emotionally driven ordinances and legislation aimed at legislating stray voltage and current phenomena. To date, the ordinances enacted and legislation proposed, both local to us and in states such as Wisconsin and Utah, have lacked technical clarity, a rational approach and reasonable scientific basis. That is unless a proposal has been made to change the laws of physics or repeal Ohm's law.
Mike Holt's Comment: If a high-impedance or open neutral of the primary neutral causes the problem, all the utility has to do is fix the problem. If it's caused by the neighbor's water heater element, then this can be fixed as well. It's really just a matter of finding out who's providing the voltage. Greg, you sound like a really smart guy and it appears that your utility "solves" the issues with the customers. But, there are utilities out there that have terrible systems, due to a lack of system maintenance (and it's not going to get better, lets not go there). Legislation? Hey, I don't like government rules anymore than the next one, but something needs to be done to get some of these utilities to fix their primary system neutrals. What about underground concentric neutral cables that are failing!?
Gregory L. Olson, P.E., CPQ
Principal Engineer - Power Quality
Electric Process & Performance
Public Service Electric & Gas Company
80 Park Plaza, MC T14A
Newark, NJ 07102-4194
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