GROUNDING ELECTRIC FENCES - Extension

Fencing Systems for Rotational GrazingGroundingGrounding Electric FencesTom Cadwallader and Dennis CosgroveUniversity of Wisconsin-Extension1

GROUNDING ELECTRIC FENCESBy far the most common reason forfailures in what appears to be a properlyconstructed, insulated and electrifiedfencing system is inadequate grounding.The Importance of ElectricalFlowBefore recommendations can be madeas to the best type of grounding systemto put on a fence, its important tounderstand why one is needed andwhat can reduce its effectiveness.In an electric fencing system, electricityneeds to complete a circuit in order todo its job. The similarity between theelectricity that is delivered by the electriccompany and the electricity that is sentout on an electric fence is that bothwant to complete the circuit and headhome. The difference is that theelectricity coming in from the powercompany needs to be confined withinthe wires and has a ground rod forprotection while the electric fencedepends entirely on ground rods as aroute for the electricity to return to theenergizer. Inadequate grounding for afence will not only limit the amount ofelectricity that is able to flow throughthe system, it will also cause theelectricity that does flow to try and findan alternative route back to theenergizer, thus creating a stray voltagerisk. Even though an energizer has thepotential to deliver power, it is theground return system that provides asafe pathway from the fence back to theenergizer and is critical to the success ofthe entire system. The size of theenergizer, the grounding material itself,soil type and soil moisture can all play aroll in designing an effective groundingsystem.The Effect of Soil Conditionson Electric Fence GroundsThere are a variety of recommendationsmade as to the amount and type ofgrounding that an electric fence needsin order to provide an adequate flow ofelectricity. Recommendations can rangefrom as simple as hooking the energizerearth return to an existing metal fenceor ground rod to driving in 3 feet ofground for every joule of energizerpower. Both recommendations may beright for a particular power unit undersome very general circumstances.However, as stated previously, theactual amount of ground and thedesign of the grounding system isdependent on several variables. Twoimportant ones are soil type andmoisture. Some may remember a simplesecondary school science experimentthat demonstrated that neither dry sandnor distilled water were very goodconductors of electricity. But if youpoured the water into the sand it carriedan electrical current quite well.This same principle holds true ingrounding a fence system. Regardless ofthe recommendation, the only area of aground rod that is able to pick upelectricity is that portion that is in moistsoil. An eight-foot ground rod that is insix feet of dry sand and two feet ofsaturated is essentially only a two-footground rod. Four eight-foot ground2

rods in six feet of dry sand and two feetof saturated are not equal to 32 feet ofground but closer to eight. On the otherhand a system may perform beautifullywith less grounding than recommendedif the rods are placed in a low wet spotthat is high in minerals and organicmatter.Knowing the types of soil conditionsthat are prevalent throughout the timeof year that the fence is in operation isextremely important. And like anything,build it for the worse case situation, notthe best.Effect of Energizer Size andTesting the SystemThere are a number of low impedanceenergizers on the market today that aredesigned to deliver as much as 60 ampsof electricity onto a fence at the peak ofits pulse, and perhaps even more undersome circumstances. Considering thatthis amount of power is more electricitythan is flowing through most homes atany given time and is delivered to thefence in somewhere between .0003 and.0005 seconds, the ground rods need alarge amount of surface area exposed tomoist soil in order to adequately pick upthe current.The larger the energizer in terms of theamount of electricity it is able to deliver,in joules1, the more effective groundingthat is required. The recommendationby some fence manufacturers of threefeet of ground rod for every joule ofenergizer power may be more thanadequate under most situations. But,regardless of the recommendation, it is agood idea to check the systemperiodically. The way to do that is to puta heavy load on the fence by groundingft out with a good conductor, such as ametal rod, and then check the voltageon the ground system by hooking afence voltage tester between a metalstake and one of the ground rods. Ifanything near or over1000 volts is flowing between the stakeand ground rod, the ground system isinadequate. In the middle of thesummer, with dry ground and heavydew, I have been able to pick up nearly1500 volts on the ground system of myown fence that was built 25% largerthan what was recommended. Groundrods are cheap and ft better to overbuildthan underbuild. It won't be a waste oftime or money.Materials to Be Used ForGroundingMost electric fence manufacturerssuggest using 1/2 to 3/4-inch diameter,six to eight foot galvanized rods andclamps for grounding. Electriccompanies on the other hand havetypically specified the use of copper fortheir ground systems. Both will work butthere are a few cautions.First of all, heavily galvanized steel willresist corrosion for long periods of timein a variety of soil conditions but theywill lose some conductance when theydo corrode. Copper and copper cladsteel will resist corrosion indefinitely inthe soil and will still maintain goodconductance even when corroded.Aluminum corrodes in soil and shouldnever be used for ground connections.The second thing to consider besidesthe attributes of the different metalsthemselves in making a groundingsystem is the problem of using differenttypes of metals within the system itself.3

Regardless of the type of metal used it ismore important to use the same type ofmaterial throughout the system. Eachmetal has different properties not only intheir ability to conduct electricity butalso in how much they expand andcontract under large power surges andchanging temperatures. If you areusing galvanized electric fence wire tocarry the electricity back to the energizerfrom the ground rods it would probablybe wise to stick with a galvanized steelsystem. But remember, if you decide togo with copper, be consistentthroughout!Placing the Ground Rodsand Making theConnectionsOnce you choose the type of metal tobe used for the ground rods, andbought enough to adequately groundthe size energizer you intend on using,the next step is placement. Here againthere are a couple of things to consider.First of all an effort should be made totry and segregate the electricity that isflowing back and forth to the fence fromthe main service panel and othercircuitry. There is a tremendous amountof electricity flowing and it is wise to tryand keep the two Systems separated asmuch as possible.The actual placement of the groundrods is dependent on where a majorityof the fence is in relation to theenergizer. The ground rod systemshould be thought of as a big antenna.The closer the system is to the areawhere most of the electricity is expectedto flow back from, and the more spreadout the system is, the better.The general recommendation for thedistance between multiple ground rodsby most fence manufacturers anddistributors has been to place the rodsabout ten feet apart. The NationalElectrical Code recommends placingrods in multiple ground rod systemstwice the length of the rods apart. Forexample, two eight-foot ground rodsshould be placed at least 16 feet apart.What is ideal for an electric fence may ormay not fall within theserecommendations but it is a good placeto start. The important thing toremember is to keep the rods spaced farenough and even enough to act as agood electrical "antenna".Once the rods are in place the next stepis to connect them all together. Startingfrom the energizer to the first groundrod, use properly insulated electric fencelead-out wire designed to handle thelarge amounts of electricity flowingthrough the system. This will helpsegregate the electricity coming back tothe energizer from the groundingsystem of the main service panel andalso keep the wire from coming incontact with other metal objects whichcould them become part of the systemand actually carry small amounts ofelectricity. Aboveground structures canalso provide another route forlightening to enter the system.After the first ground rod it is up to theindividual whether they want to makethe connections between additionalrods with insulated or uninsulated wire.Regardless of what wire is used, alwaysuse the same gauge, or larger, wire thatis used in the rest of the fence system.The actual connection between theground rods and the wires betweenthem is extremely important. From4

purely a maintenance standpoint,ground rod connections should bemade where they can be easily checkedusing approved ground rod clampsmade of the same material as the metalsit is connecting. Every spring a routinemaintenance practice should includetaking apart the ground rodconnections and cleaning them toremove corrosion. Throughout thesummer and winter the metals expandand contract continually allowingcorrosion to occur that will reduceconductance. A little time and a wirebrush can keep the system in goodworking order.ConclusionElectric fencing is a pain barrier. And inorder to effectively use some of thenewer fencing materials on the markettoday that allow easy and flexiblefencing, the flow of electricity throughthe system depends on not onlyadequate power being placed on thefence, but an effective earth or groundsystem that allows the power to flowunimpeded.Constructing an adequate groundsystem is critical to the success of anymodern, low impedance electric fencesystem.5

Electric fencing is a pain barrier. And in order to effectively use some of the newer fencing materials on the market today that allow easy and flexible fencing, the flow of electricity through the system depends on not only adequate power being placed on the fence, but an effective earth