Interference and Induction explained...

INTERFERENCE

Radio and telephone interference problems can occur, particularly in areas with poor radio reception .

Clicking on the radio or telephone can be caused by:

The energizer being too close to the mains power earth.

• A bare earth wire touching the building.
• A poor mains power earth.
• Loose connections in the energizer or plugs..
• The electric fence running parallel to telephone or power lines.
• Poor or rusty joints on the fence line.
• Damaged cut-out switch or cracked insulators.
• A broken cable under a gateway.
• Vegetation arcing / touching the fence
• Any mechanical short.

To detect if the fence is causing the problem disconnect the fence and the earth wires from the energiser and switch the energiser on. If the clicking stops the problem is on the fence line or earth. If the clicking continues then the problem is either in the energiser or the mains power supply. Check the plugs. If the problem is in the mains power supply the clicking will stop immediately the when the energiser plug is pulled. If the problem is in the energiser an extra click will be heard after the energiser plug is pulled.

INDUCTION

Induction is a phenomenon associated with High Voltage wires whereby a small current is transmitted through the atmosphere to adjacent neutral wires. Induction can be detected in an item by using a volt meter, or when the item is touched, one can feel a small shock.

Induced voltage can be detected on :-

Conventional fences carrying offset or lead-out wires

The wire between the strain insulator and the strainer post

Metal gates

Milking parlour railing

Showers

Induction is linked to poor earthing and can be prevented or eliminated by earthing the offending item.

Induction does not affect the voltage on the fence line.

Training Animals to Respect Electric Fences

TRAINING ANIMALS TO RESPECT ELECTRIC FENCES

An electric fence is both a physical and a psychological barrier. All animals therefore need to be trained to respect these fences. It is therefore imperative that they receive a good shock the first time they make contact with the fence

Below are some tried and tested methods of introducing game to electric fences :-

1) Power up the electric fence as construction proceeds. This should be done on a daily basis. The reasons for doing this are :-

(i) It will ensure that the more inquisitive animals receive a good shock the first time they make contact with the fence. This will help reduce the time needed to train your animals as the leaders will either communicate, or the herd will sense, that their new perimeter is hostile.

(ii) It will reduce the incidence of damage to the fence line caused by animals testing it while it is off. Besides causing damage the fence, your animals will also lose respect for it and then it will take you longer to train them when the fence line is switched on.

(iii) It will enable you to check for faults as construction proceeds. It is very frustrating switching on a newly erected electric fence and then having to walk kilometres of fence line looking for faults.

2). Pad wipe the live wires with molasses. As a rule of thumb live wires should be situated at nose height to the animals you intend to control. A simple way of attracting the animals to sniff the live wires is to wipe some diluted molasses onto these wires. The animals will soon learn, via their damp muzzles, what electric fencing can do.

4) Install flashing neon lights on the fence.

Commonly called live lights, these lights draw the power needed to make them flash from the energiser's pulses. These flashing live lights improve fence line visibility and this in turn prevents nocturnal feeders, such as hippos, from blundering into the fence. Live lights will also enable you to see at a glance if your fence is working. Alternatiely, cans or aluminium strips can be attached to the fence wires to improve visibility.

5) Maintain power on the fence line at all times

Unlike on a stock farm where domesticated animals soon become accustomed to electric fences, on a game reserve one encounters a variety of species, and also changing populations of the same species, which will vary in size, age, and sex. These variations will result in different behavioural responses to the electric fence. Furthermore, the wilder an animal, the more sensitive it appears to be to an electric fence and the sooner it will detect if an electric fence is switched off. So rather than let your animals detect that the electric fence is switched off and have them break out, make sure that your electric fence is switched on at all times. The installation of live lights, or a simple electric fence voltage monitor, will also enable you to continuously monitor your fence line and be sure that the power is on. It is advisable to keep a spare energiser module as a standby.

6) Consider the Season.

Time of year and season will also influence your animal's response to an electric fence. In the dry months one is faced with the problem of poor soil conduction and inefficient ground earthing. It is better to introduce animals to electric fencing during the wetter months.

7) Keep the fence line clean and well cleared.

This will not only reduce voltage and power losses but it will also help prevent animals from blundering into the fence line. A strip three meters wide, on either side of the fence line should be kept clear of bush and trees and the grass kept short. A herbicide may be sprayed directly under the fence line but beware of causing erosion in hilly areas. Game will come to associate this well cleared strip with a shock.

8) Electrify trans-location Bomas.

Just as livestock farmers use a well fenced, electrified, training camp to introduce new animals to electric fencing, so too should the game farmer. By attaching electric wires onto the interior of your boma you can train your animals in the boma to respect electric fences. These offset electrified wires should only be switched on once the animals have settled down in the Boma.

All animals need to be trained to respect electric fencing. It is therefore important that animals that are being introduced to electric fencing are given time and space to learn that their new perimeters are hostile.

Basic Fault Finding Procedure

BASIC FAULT FINDING PROCEDURE

1. Disconnect energiser from the fence line and using a voltmeter or fence compass, test the voltage on the terminals.

• If the voltage is normal, the energiser is functioning properly (proceed to 2).
• If not, install another energiser and return the faulty one to your dealer for repair.

2. Reconnect the energiser to the fence.

3 Check the earth system for:

• Rust
• Loose connections
• Insufficient earth stakes

4 Check that the lightning diverter is not faulty / blown.

• If faulty, it should be replaced
• If functioning correctly, proceed to 5.

5 Proceed to the first cut out switch and open it (switch off)

6. Using the voltmeter or fence compass, check the voltage on the live section of fence (energiser side):

• If voltage is low the fault is between this switch and the energizer.
• If voltage is normal, close the switch (switch on) again and proceed to the next switch.

7. Continue with this procedure until the fault is found.

8. Always check the voltage on both sides of gates and the lead-out.

9. While walking the fence keep an eye open for:

• Broken or tangled wires.
• Excessive competition from vegetation.
• Trees or branches across the wire.
• Loose or corroded connections.
• Dirty or cracked insulators.
• Listen for "popping" as you walk along the fence.

10. The closer you get to the fault / short the lower the voltage reading will become. Beyond the fault the voltage may increase again -if not a dead short.

Electric Fence Safety

SAFETY

You should always treat an electric fence energiser with respect. An electric fence energiser can deliver a very powerful shock, which may be harmful to children or pets under some conditions.

• Electric fences should be installed and operated so that they cause no electrical hazard to persons, animals or their surroundings.
• Electric fence constructions, which are likely to lead to entanglement of animals or persons, should be avoided.
• Barbed or razor wire should not be electrified.
• A non-electrified fence incorporating barbed wire or razor wire may be used to offset electrified wires of an electric animal fence. The supporting devices for the electrified wires should be constructed so as ensure these wires are positioned at a minimum distance of 150mm from the vertical plane of the non electrified wires. The barbed/razor wire should be earthed at regular intervals.
• Never use electric fencing where it is likely to be touched by children or infants. This applies especially near swimming pools or dams where they are likely to be on wet ground with bare feet.
• Energisers should, if possible, be installed inside a building in a position free from the risk of mechanical damage. If mounted outdoors, they should be mounted on a substantial structure in a position free from the risk of mechanical damage.
• Never use any part of your household wiring or plumbing as an earth for your electric fence.
• Each electric fence energiser should be fitted with a separate earth electrode and this should not be connected to any other earthing device.
• A minimum distance of 10m should be maintained between the energiser earth spike and any other earthing system such as the power supply system protective earth or the telecommunication system earth.
• An electric fence should not be supplied from more than one energiser or from independent fence circuits of the same energiser.
• The gap between two separate electric fences with different energisers should be at least 2m.
• If this gap is to be closed, this should be effected by means of an electrically non conductive material.
• Crossings with overhead power lines should be avoided wherever possible. If such a crossing cannot be avoided, it should be made underneath the power line, and as nearly as possible at right angles to it.
• Connecting leads and electric fence wires should not cross above overhead power or communication lines.
• If an electric fence has to be installed in the vicinity of an overhead power line, the vertical distance between any fence wire or connecting lead and the surface of the earth should not exceed 2 metres.
• If connecting leads and electric fences are installed near an overhead power line the clearances shall be:
• Power Line Voltage: Under 1000 volts - Clearance: 3 Metres
• Power Line Voltage: 1000 - 33,000 volts - Clearance: 4 Metres
• Power Line Voltage: Over 33,000 volts - Clearance: 8 Metres
• Fence wiring should be installed so that it is well away from any telephone or telegraph line or radio aerial.
• An electric fence, when installed in such a position that members of the public might reasonably be expected to touch it, should be identified by suitable signs clamped to the conductor or fastened to the posts at intervals not exceeding 90 metres.
• The sign should have a size of at least 200mm x 100mm. The inscription on the sign should take the form of either the recognised symbol, or the words “ELECTRIC FENCE”. The inscription should be indelible and any lettering should have a height of at least 25mm. It is recommended that the basic colour of the sign be yellow with black inscription.
• Connecting leads that are run inside buildings should be effectively insulated from the earth structural parts of the building. This may be achieved by using double insulated high voltage HT cable.
• Connecting leads should not be installed in the same conduit as the mains supply wiring, communication cables or data cables.
• Where the electric fence energiser is used to supply a system of conductors for deterring birds from roosting on buildings, no conductors should be connected to earth. A switch should be installed to provide a means of isolating the energiser from all poles of the supply and clear warning notices should be fitted at every point where persons may have ready access to the conductors. The notice should bear the words “LIVE WIRES” in block letters not less than 13mm high. The letters should be red in colour on a white background and the size of each notice should not be less than 62mm x 50mm overall.
• In periods of extreme fire danger there is a possibility that your electric fence may start a fire. This possibility is greatly reduced if you connect your fence to the low-power terminal of the energiser during the danger period.
• Lightning strikes during thunderstorms are common. You may have kilometres of carefully insulated fence wires on your property, which will conduct the electricity straight back to your energiser. Apart from the obvious fire risk, this will certainly damage or destroy the energiser. You should disconnect the energiser from the fence, and unplug it from the power source for protection during electrical storms.

EARTHING

Earthing is the most important component of an electric fencing system. In practice, most problems which occur with electric fences are caused by poor earthing.

For an electric fence to be effective the circuit must be completed. When an animal touches the fence wire the circuit is completed (closed) through to the ground, or to the earth return wires, and the current flows back, via the earth pegs, to the earth terminal of the energizer. This current flow must be good in order to deliver a decent shock to the animal. Therefore, it is imperative that the energiser is well and truly earthed. Soil that is very dry, sandy or pumice will not conduct the electric current as effectively as clay or slightly damp soil. In these less than ideal conditions, it is more difficult to get an adequate earth system to ensure the animal receives the maximum shock. It is best to choose a damp area for earth installation where possible.

The 4.3.2.1 earthing rule:

This general rule suggests you use a minimum of FOUR galvanised stakes placed THREE meters apart from each other, each TWO metres long (underground) and connected by ONE continuous wire.

It is also important to place the earthing system as close as possible to the energizer and at least 10 meters from any power supply, earth stake, underground telephone or power cable. Never connect two or more energizers to the same earth peg. Don’t use copper earth stakes with galvanised wire as this will cause electrolysis at the joins. The earth system should not be allowed to touch any building. Never connect the energizer earth to the water supply. For best results a location with permanently moist ground, such as near a stream, dam, trough, or septic absorption trenches or water tank overflow.

Purpose manufactured earth stakes are the easiest to use and consist of either galvanized steel rods or angle iron. The stakes are connected to each other and to the earth terminal of the energiser, using galvanized nuts and bolts. Alternatively, a length of galvanized water pipe can be used, but it is harder to drive in and is difficult to connect to the earth wire satisfactorily.

INTERMEDIATE EARTHING

On long fence runs, and in dry areas, there may be insufficient moisture within the soil to provide adequate current flow through the earth return system. In these situations, a fence return system is used. Earth connections are then made at regular intervals along the length of the fence. This is achieved by simply connecting the earth wires to additional earth stakes, periodically spaced. Connections should be made using line clamps and insulated cable or steel wire. Where possible intermediate earths should also be established in moist ground (eg, near a dam or stream).

TESTING THE FENCE EARTH RETURN

A poor or inefficient earth system will restrict the flow of electrons or current around the circuit. To test the earth, drive a galvanised earth state at least a meter into the ground and at least a meter away from the nearest earth stake of the fence system Then using a Digital Volt Meter measure the voltage between this installed earth peg and the nearest earth peg attached to the energiser earth system. Bring the fence line voltage down to 2K v or less by placing several steel stakes between the live wire of the fence and the ground, at least 100M away from the earth system. On a clean well-insulated fence there is very little current flow so in order to test the earth it is necessary to create current flow creating a short or leakage path. Ideally there should be no reading on the volt meter. A reading of up to 200 volts, provided the fence is shorted to below 2000volts, is acceptable. If the voltage is higher than 200 volts then the earth return wire must be checked for loose connections and / or more earth stakes must be installed along the fence line. These additional stakes must be coupled to the earth return wire.

DO’S & DON’T’S OF EARTHING

DO

Use at least 4 galvanised earth stakes each at least 1.5M long.

Drive the earth stakes into the ground at least 3M apart.

Connect the earth stakes together using a single length of insulated undergate cable or fencing wire.

Clamp the cable securely to the earth stakes

Install the earth stakes:

In moist or damp soil.

Close to the building or along the fence line for protection

At least l0M away from any mains power supply, earth stakes, underground telephone cables, power cable or water pipe.

DON'T

Connect two or more energizers to the same earth peg.

Allow any part of the earth system to touch a building i.e. bare wires.

Connect the energizer earth to mains electricity or telephone earths.

Connect the earth system to water mains.

Remember, surveys have shown that over 80% of electric fencing systems suffer from inadequate earthing. So, spend a little extra time on this important aspect of your electric fence and enjoy many years of trouble free fencing.

ELECTRIC FENCE COMPONENTS

ELECTRIC FENCE COMPONENTS

An electric fence system is made up of four components:

• The energiser
• The earthing system
• The leadout
• The fence line

If any one, or more, of these components is faulty or defective, then the whole system will be defective.

Linking the four components of an electric fence together provides the circuit through which the current will flow

The energiser

An energizer is an "electron pump" that converts an A.C. or D.C. electric power source into high voltage pulsed energy. The power source can be either 220 Volt mains power or a 12 Volt battery supply.

When comparing an energizer to a water pump:

Voltage = Pressure

Amps = Flow ( volume )

The power output of an energizer is measured in Joules. The output Joule capability of an energizer is a measurement that can be used to compare energisers and can be likened to Horsepower of an engine.

The earthing system

The earthing system refers to the galvanised metal stakes that are placed in the earth near the energizer. The metal stakes in the ground are part of the circuit that is completed when the animal touches the wire. The completion of the circuit is what allows the animal to get a shock. It is essential to have an effective earthing system. Soil that is very dry, sandy or pumice will not conduct the electric current as effectively as clay or slightly damp soil. In these less than ideal conditions, it is more difficult to get an adequate earth system to ensure the animal receives the maximum shock. It is best to choose a damp area for earth installation where possible.

The lead out

The lead out is the high conductive insulated cable or wire that connects the energizer to the fence. It is important to have a lead out that is able to deliver the full power of the energizer to the fence. If the fence is several hundred meters from the building where the energizer is installed cable should be used to get the power to the outside of the building.

The fence

It is important for your fence to be well insulated to ensure the voltage remains constant along your entire fence system. Insulators, to which the wire is attached, provide protection from losing voltage as a result of the wire coming into contact with the post and being lost to the ground, i.e. ‘shorting out’. The quality of the fence and insulators will determine its effectiveness. Generally, for wildlife, conventional non-electric fences are re-enforced by attaching offset brackets and an electrified wire to the side of the fence.

Definitions of electrical terms used in association with Electric Fencing

DEFINITIONS

These definitions of electrical terms are frequently used in association with electrical fencing. While all the definitions are correct in content, details necessary to make the definition rigorous have frequently been omitted for clarity.

• Electricity: A flow of electrons around a circuit.
• Electric Charge: This is the quantity of electricity -literally the number of electrons. Charge is measured in coulombs.
• Voltage: The electrical pressure that forces electrons around a circuit. A voltage is necessary before any current can flow.
• Current: The rate at which electrons are flowing in a circuit. Current is measured in amperes, but this is commonly shortened to amps.
• Power: Power in electrical form has the same sense as power from an engine. It is the ability to do work at a certain rate and is measured in watts. Power is voltage multiplied by current.
• Energy: Electrical energy is the ability to provide power for a period of time. It ismeasured in joules, a joule being one watt of power developed for one second. Similarly 1000 watts for one hour is a kilowatt-hour or one unit, the basis of local authority power charges. One kilowatt-hour is equivalent to 3,6 million joules.
• Conductor: A material through which electrons will readily flow (all metals are conductors).
• Insulator: A material that strongly resists the flow of electrons through it.
• Circuit: A conducting path around which electrons may flow.
• Resistance: Opposition by an electric circuit to the flow of electrons. Whenever a current flows in a resistor, energy is lost in the form of heat. Resistance is measured in ohms.
• Inductance: Opposition by a circuit to rapid changes in electric current. Energy is not lost but stored in an inductor.
• Capacitance: Opposition by a circuit to slow changes in electric current. Energy is not lost but is stored in a capacitor.
• Impedance: Opposition by a circuit to current flow due to the effects of resistance, inductance and capacitance. Whenever a current flows through an impedance, there is a voltage developed across it. If this impedance is the effective internal impedance of an electric fence energiser, or the impedance of an earth or lead out wire, the voltage developed across it would be considered to be a loss.

How and Why Electric Fencing Works!

HOW ELECTRIC FENCING WORKS

An electric fence system consists of an electric fence energiser, a fence wire or combination of wires supported on insulators, fixed on posts. These together with the EARTH system, form a pulsed high voltage OPEN LOOP with the animal being the completing link.

An electric fence works by “educating” your animals so that they learn to associate touching the fence with receiving an unpleasant shock. The effectiveness of the fence is the SHOCK, in both the meanings of the word. This is the same principle as barbed wire, but it presents a much more powerful deterrent with very little danger of physical damage to your stock. The source of the shock is the energiser. The energiser provides regular pulses of electricity to the fence. These intermittent high voltage pulses flow from the energiser, along connection cable to the fence, and then along the length of the fence. A pulsed electric current is sent along the fence wire, about one pulse per second, from an energizer which is earthed. When the animal touches the fence it completes the circuit between the fence and the ground and receives a short, sharp but safe shock. The shock is sufficiently memorable that the animal never forgets. The strength of the shock the animal receives depends upon the power available from the energiser, and the total resistance of the circuit.

WHY ELECTRIFIED FENCES WORK

Electric current (AMPS) only flows when a circuit is completed between a positive and negative terminal.

An electric fence circuit is made on a larger scale. The energizer fence terminal (positive) is connected to the insulated fences wires, and the energizer earth terminal (negative) is connected to galvanised metal stakes driven into the ground.

The same 'circuit completion' is necessary before the animal gets a short, sharp but safe shock. An animal standing on the ground and touching the electrified wires will complete the circuit like the closed switch above. The shock is sufficiently memorable that the animal never forgets.

Because the electric fence is also a psychological barrier, it does not require great strength to be effective. However, it must be well designed and constructed to absorb some pressure from animals and wind. The energizer must have enough power for the length of the fence and for the animals being controlled.

An Introduction and the advantages of Electric Fencing

An electric fence is a psychological and physical barrier that keeps wildlife or farm animals in and unwanted animals and vermin out - even over long distances. There is nothing new about using electricity to control animals. For over seventy years farmers have been using electric fences to control their livestock and as long ago as 1952 records show that Uganda State Forestry department used electric fences to protect young seedlings from being damaged by African wildlife. The mechanical "tick tock” high internal impedance type energisers used back then were however unable to overcome much competition from vegetation and thus could only power relatively short lengths of fence line. The technological advancements in solid state electronics during the 1970's resulted in the development of the modern low internal impedance high powered energisers in use today. These modern energisers are capable of powering many kilometres of multi strand electric fencing and the electric fence has now become a truly effective management tool that is being used successfully around the world to control all species of wildlife. Today very few conservation organisations do not incorporate electric fencing in their wildlife management programs. However, despite the successes achieved in Africa and elsewhere around the world, electric fencing still has its detractors. While most people swear by it there are still a few who do not believe it works effectively. The reason for this is simple. Those who understand and apply the basic principles of electric fencing when constructing their electric fences will reap the benefits of electric fencing, while those who do not apply these principles will never get their fence to work effectively. Finally. while economics will obviously be an important consideration when planning any electric fencing project, guard against being too thrifty and of basing major decisions on price considerations alone.

ADVANTAGES OF ELECTRIC FENCING

Electric fencing offers the following benefits:

1. Low cost

An electric fence can perform the same task as a conventional fence using much less material.

2. Easy to build

Lower wire strains and generally lighter construction make much quicker and easier construction, especially in difficult terrain.

3. Durability

Electric fences are not subjected to the same physical pressure from animals, and can therefore be expected to have a greatly extended service life. The life of old fences can be considerably extended using electric fencing.

4. Universal application

Electric fencing will contain all types of animals. Educated stock develop greater respect for electric fencing than for any other type of fence.

5. Flexibility

There is no quicker or easier way to effectively subdivide a paddock for controlled grazing than with an electric fence.

6. Low maintenance

Once your fence is properly installed and your stock are trained, the maintenance requirements of electric fencing are little different from conventional fences.

7. Less stock damage

The shock from your electric fence causes no physical damage to hides and pelts. If your stock is forced through the fence by bushfires or dogs, they are at less risk than with a conventional fence.