Safe-Fence Electric System - BASIC PRINCIPLES
In all electrical devices there are two basic components, the positive field and the negative field. The positive field is the active power or current flow of electricity consisting of voltage and amperage. The negative field in most common forms of electrical applications is the medium that connects the positive field back to itself establishing the flow of power (commonly referred to as ground or earth). The easiest way to envision this is with a light switch. When the switch is on it connects the positive wire to the negative wire allowing power to flow through the bulb and illuminate. In electric fence the positive is connected to the fence material and the negative is connected to the earth or soil. Relating electric fence power to the imagery of the light switch, when the animal, who is standing on the negative field (earth) touches the positive field (fence) it is like the light switch and the light bulb combined. Its body connects positive to negative and is also illuminated at the same time.
Supplying power to an electric fence is a much greater challenge than powering a household device. Voltage, which is the driving force of amperage, degenerates when it meets resistance. In our household devices the path that electricity must follow is clean and direct, usually over a very short distance. In electric fence applications however, electricity must flow from the fencer through the fence, into the animal and back through the ground over an undetermined distance with very poor conductive conditions. The voltage can deteriorate in these conditions to the point of becoming inadequate. It is important to understand that the animal will only feel the amount of power that returns to the fence charger through the earth regardless of the amount of power in the fence. Therefore fence chargers must produce enough voltage to accommodate deterioration and still be effective.
Studies conducted by PAMI, a Canadian testing organization, indicate that it requires approximately 700 volts to penetrate the hair, hide and hoof of short-haired livestock. When fencer power falls below 700 volts the animal will not feel a shock because the voltage is to low to break down the impedance of the animals body. We recommend a minimum of 2000 volts of active fence power to insure effectiveness.
WHY USE ELECTRIC FENCE
Electric fence is the most effective form of livestock control for one very simple reason. It offers the same kind of natural emotional response that large animals are accustomed to in the herd environment. In other words in every herd of large animals there is a pecking order. The genetically dominant animals in many cases, regardless of size, become the accepted leader. The lessor animals of the herd respect that position. When an animal with a lessor social position challenges the dominant authority they are met with an immediate and sometimes violent response. Electric fence treats these animals in a manner that they naturally respect. A shock from a low impedance fencer is quite intense and establishes the same emotion in the animal as if it were kicked or bitten by the herd boss, but without potential injury.
With the exception of barbed wire, electric fence is the most economical fencing that can be installed. Considering that the shock of the fence is the greater deterrent and not brute strength, the need for elaborate bracing is unnecessary except with high tensile wire.
Reduced repair and maintenance of electric fence also adds to the economical value. Over long periods, electric fence requires far less consumption of time and money to maintain over most rigid products.
Fence load is a combination of many factors. The length of the fence, the number of strands and condition of the wire or tape, splices in the wire, connections, broken insulators that create shorts, and foliage growing on the fence all contribute to fence load. Proper fence design, construction and maintenance, along with an adequately powered fence charger, makes for an effective, economical means of livestock control.
An electric fence is a less-than-ideal environment on which to conduct electricity. Along the course of the average fence there are many conditions which will divert or impede the flow of electricity. Collectively, these conditions are known as fence load.
Weeds or vegetation growing on the fence line are the most common culprit contributing to a heavy fence load. Green plants draw voltage and amperage from the fence to the earth. Other circumstances can rob the fence of voltage and amperage. Cracked or broken insulators, or insulators of poor design will allow electricity to leak to the fence post and return to earth. Sagging or broken wires can contact uninsulated wires or the ground. Wet weather will magnify all of these problems. When enough conditions exist to draw all of the electricity produced by the fence charger from the fence, the fence is said to be "shorted out."
Rusty wire, poor splices, or wire of insufficient diameter to carry the flow of voltage and amperage also contribute to fence load. These problems do not draw voltage and amperage to earth, but they do impede the flow of electricity along the fence, contributing to the fence load.
Even the length of the fence contributes to the fence load. The longer the fence, the less ability (or greater capacitance) it has to store the energy supplied by the charger. On very long fences, capacitance can be a major contributor to fence load.
Proper construction with quality components, installing an adequately powered fence charger, and good management practices are the key to keeping fence load under control.
Improper grounding is the cause for 90% of the problems experienced with electric fence. Think of the ground system as an underground antenna, the more electricity it is capable of collecting the greater the shock sensation the animal will recognize.
We recommend 3 - 6 foot ground rods spaced 10 feet apart for proper fence charger grounding. We want to ensure that you have maximum fence efficiency.
A good way to test ground rod efficiency is to place a metal rod, 12 to 18 inches long, in the ground about 3 feet from the ground rod. With a volt meter contact the short rod to the ground. If you read more than 500 volts you need to add another ground rod or replace the ones you have with longer ones.
In areas where heavy snow and ice are an issue, you may need to take additional grounding measures. Most people don't realize that neither snow nor rainwater will conduct electricity. Frozen ground also reduces the flow of current. When animals are to be left out in electric fenced areas during frozen snowy conditions you can improve the electric fence function by running a 12 1/2 gauge wire, on or just below the surface of the ground, connected to the fence posts. This wire is attached to the ground terminal of the fencer thereby creating maximum conductivity when the animal touches the fence, even in snow.
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