logo.gif (9533 bytes)

Stray Voltage Caused By The Electrical Utility:

Stray Voltage caused by the Electrical Utility is so common and the damage cost is so high, that utilities should be required to install neutral isolation devices on all transformers serving dairies and other livestock operations.

The Electrical Utility causes stray voltage when they connect the neutral on the primary side of the transformer serving the farm to the neutral on the secondary winding of the transformer. This is the standard connection specified in the National Electrical Safety Code (NESC) which governs the utilities. The National Electrical Code (NEC), which covers the on farm wiring, requires that the secondary neutral be hard wired to the buildings water system, structure and electrical ground rod. Therefore, the voltage level of the building structure and water system is elevated to the voltage level of the primary neutral conductor on the utilities electrical distribution network. This voltage can be significant and is the primary cause of Stray Voltage on a farm.

The origin of the stray voltage problem lies in the fact that Electrical Utilities do not make a distinction between the function of the Neutral (the grounded conductor) and a Ground. The Electrical Utilities in conjunction with the IEEE has developed the National Electrical Safety Code (NESC). This code requires them to ground the primary neutral conductor at least four times per mile distribute electricity across the countryside. Electrically, the ground rods are actually resistors ranging from 10 to several hundred ohms. The actual resistance depends upon the moisture content and conductivity of the soil. The utilities deliberately design their systems to use the earth as a secondary neutral conductor.

The voltage on the primary neutral increases as the distance from the substation increases. Each ground rod tends to reduce the voltage by diverting some of the neutral current into the earth. The current splits between the neutral wire and ground rod in accordance with ohms law. The primary neutral voltage at the end of the distribution line can be 20 volts or more depending on the combined load on the distribution line and the conductivity of the earth. The NESC requires the Electrical Utility to connect the primary neutral to the secondary neutral on each transformer serving a customer. The National Electrical Code (NEC) which governs the on farm wiring, requires that the secondary neutral be grounded to the water pipes for every building being served. Effectively the SAFETY CODES have required us to hard wire our water system directly to the neutral on the primary distribution side of the transformer. This is the primary cause of Stray Voltage on a farm.

The second cause of Stray Voltage is more subtle and relates to the ground rods injecting some of the neutral current into the earth. This current must flow back to the point where the substation neutral is grounded or to a ground connected to an opposing phase from the same transformer bank. The earth currents that result from utilities grounding their neutrals causes a widespread 60 cycle electrical field and voltage gradient to be present at most locations in the United States. This statement can be easily verified by driving metal rods into the earth 100 feet apart and measuring the voltage between them.

If the utilities primary neutral wire opens for any reason, the total primary neutral current will diverted to flow through the ground rods including the customers piping. The utilities primary distribution voltage is usually above 4,000 volts. Therefore, when the neutral conductor feeding the transformer opens, the neutral voltage at the transformer can rise to very high voltage levels. The voltage levels on grounded surfaces the farm rise to the same level and can cause severe electrical shock to humans and can even kill animals. Most power companies cannot automatically detect this condition. This is one of the conditions that can cause stray voltage to appear on wells and structures that have no electricity connected to them. This is another good reason for the utilities to add a ground wire to their distribution wiring and stop grounding their neutrals anywhere except at the substation.

The earth currents always take the path of least resistance back to the substation. The concrete and steel structure of a building or metal pipes can provide a low impedance bridge for the earth current. In some cases, ground currents flowing through the building can generate stray voltage even when there is no electrical connection to the building. This condition can be caused by a number of things including broken primary neutral wires, interaction between substations and faulty utility company equipment. It usually requires a highly skilled engineer with good test equipment to isolate and solve this type of Stray Voltage problem.

It is an undisputed fact that Stray Voltage is caused by the Electrical Utilities connecting the primary and secondary neutrals on their transformers. The cost to isolate them is only about $100.00. WHY doesn't the Utility simply isolate the neutrals on all farms? I have not been able to find a single engineer that was able to give a technical justification for connecting the primary and secondary neutrals other than "it has always been done this way"! Unfortunately, the utilities' will probably not change the way they do things in my lifetime.

Visit the following pages for a more detailed study of stray voltage.

What is Stray Voltage?

How Can Stray Voltage be Caused by Farm Wiring?

How Do I Test for Stray Voltage?

How Do I Protect Myself from Bogus Stray Voltage Testing?


 

For Help or more information, call John Bass at

952/544-5377.

Email: help@BassEngineering.com

Click Here to Search Our Web Site:

Bass Associates Inc.
13533 Larkin Drive, Minnetonka, MN 55305
Phone: 952/544-
5377


Copyright 1998 Bass Associates Inc. Last modified: July 28, 2015