Agricultural specialists have known for some time that low-level non-lethal voltages inadvertently applied to dairy animals can cause mastitis, affect animal behavior, and reduce milk production. More recently, these voltages have been known to cause problems in swine parlors, poultry houses, water fountains, swimming pools, and homes.
Various studies have shown that voltages as low as 0.5 volts can be detected by animals that are very wet, such as a dairy cow that has been washed down before milking. There is evidence that humans are susceptible to a threshold voltage of approximately 1 volt when wet. Thus, voltages below 10 volts, which the electrical industry has previously dismissed as non-issues, are now being more closely scrutinized and solutions pursued.
These low voltages have many sources and several common names, such as extraneous voltage or more generically stray voltage. Numerous studies and findings have identified methodical and logical methods for identifying the sources of the problems and eliminating them.
On-site voltages caused by wiring problems and electrical equipment defects can be isolated by turning the service entrance switch off. Then, operation of individual circuits and equipment can identify specific problems. Examples include failed water heater elements, defective electric motors and pumps, and damaged wiring insulation. The portion of the voltage that remains on the ground system after the service entrance main is turned off is obviously off-site in origin. However, neutral-to-earth voltage that increases with on-site load may also be considered off-site if it is due to increased load on the primary neutral. This phenomenon can lead to confusion when attempting to resolve the overall problem. Proper wiring and good equipment practices can eliminate all on-site problems.
Several sources of voltages can originate off-site. Regardless of the source, stray voltage must be identified and eliminated. Common off-site sources include the power supplier neutral, telephone ground, cable television, cathodic protection on buried pipelines, and faulty electrical equipment on another site. The most common off-site source is the power supplier neutral, which can often be the entire source of stray voltage or contribute only a portion. This neutral primary current-caused contribution may well be above the 0.5-volt threshold and must be eliminated by appropriate, safe, and cost-effective methods.
Electric power suppliers often utilize a multi-grounded distribution system. Both three and single phase power lines are equipped with a neutral to return current to their substation. Even expertly balanced three phase lines cannot eliminate all current flow on the neutral, and single phase loads cause further imbalance. Electric current requires a voltage drop to push it along a conductor. As load on the line builds, there is a proportional increase in voltage, resulting in a small voltage usually present on power line neutrals. While not normally representing any lethal hazard, this voltage may cause problems in highly sensitive situations like a dairy parlor or swimming pool.
Power line neutrals are grounded at every service, transformer, and at least four times per mile, causing voltage on the primary neutral to vary as load and grounding electrode resistance change. Ground resistances change with soil moisture, losing conductivity in dry weather and regaining it with moisture. The greatest electrical loads occur in extreme temperature conditions, typically on a hot dry summer day, when the neutral grounding system has its lowest current-carrying capacity, increasing the voltage on the neutral. This results in voltage problems from power line neutrals appearing and disappearing in a seemingly mystical fashion, with load variations adding to the confusion. Although it may go away, there is no assurance of what it will cause. A loose neutral connection can cause stray voltage, and a fault at another service may contribute as well. A poor primary neutral connection can be masked by the customer's grounding system, giving no obvious signs of a problem unless a stray voltage check is made. This is a neutral-to-earth voltage and can be easily measured with any voltmeter and a remote ground.
Electric power distribution systems typically require the primary and secondary neutrals to be interconnected for two reasons:
However, this interconnect applies any voltage on the primary neutral to the secondary neutral, following the secondary neutral into the service entrance panel neutral bar, through the bonding jumper required by the NEC, to the equipment grounding bar, and from there to every piece of grounded electrical equipment in the facility.
The electrical system would be fine if the interconnection of the primary and secondary neutrals were removed, eliminating any voltage entering from the primary neutral. However, this is not permitted as it would allow a potentially dangerous situation.
The BLOCKER, a neutral isolation device, is placed in the interconnection of the primary and secondary neutral. It has approximately 2000 ohms resistance at 6 volts and drops to approximately 1500 ohms at 9 volts. At 11 volts, its resistance drops dramatically to less than 1 ohm, acting like a switch that has closed. Since a properly configured and wired distribution system almost never has neutral-to-earth voltages in excess of 6 to 8 volts, the BLOCKER is virtually an open circuit, “blocking” the neutral-to-earth voltage from entering a customer’s service. If the neutral-to-earth voltage exceeds 11 volts, a fault or other failure has occurred, and the BLOCKER acts as a short circuit, connecting the neutral for safety with the BLOCKER in the “shorted” mode. With years of field experience and hundreds installed throughout the U.S. and Canada, these units have proven to be extremely durable and reliable.
A typical response when encountering off-site stray voltage is to drive additional grounds on the premises. However, given the numerous grounds along the multi-grounded distribution system, the addition of even a few grounds is not likely to reduce the stray voltage significantly. In reality, if the entire grounding complex were duplicated, the voltage would only be reduced by half.
The equipotential plane has been used in dairy parlors for protection within a small confined area. It does nothing to eliminate the source of the stray voltage and corrects nothing in the milk parlor, waterers, outside electric heaters, etc. Neutral sources can be safely guarded against by installing the BLOCKER, which costs much less than a single problem caused by a loose wire on the equipotential plane. Overall, the BLOCKER is a cost-effective device that retains system safety and reliability while eliminating troublesome neutral-to-earth “stray voltage.”
The RONK BLOCKER has proven to be an effective and economical device for eliminating stray voltage problems originating from the power supplier's primary neutral while providing secondary fault protection and access to the secondary grounding system for dispersal of lightning. It offers protection for dairies, homes, swimming pools, fountains, swine parlors, and poultry installations.
Contact our Sales team for more information on the RONK line of BLOCKERS: 1-800-221-7665
