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Voltage, Current, Energy and Power

Most people are more familiar with mechanical and fluid systems than with electrical. While we use the words Voltage, Current, Power and Energy in everyday speech the electrical concepts that these words describe may not be widely understood.
Let's compare electricity to a more familiar water analogy. Voltage is like Pressure, Current is like water Flow. You cannot have flow without some pressure, but if the tap is off you can have pressure without flow.
Energy is a measure of the work done (like moving a heavy object), Power is rate of energy transfer. Energy (in any system) is measured in Joules.
For a more information see Electric fence ratings, terminology and units
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Joules

The Joule is a measure of energy. You may be more familiar with kilowatt hours because that is how we are charged for electricity usage. We are being charged for energy, which makes sense. For a bit of trivia 1 kW.h = 3.6 megajoules!
There is some debate as to how electric fence energisers should be rated. Ratings are necessary of course, it's good for competition so the customer can make a informed choice between products.
Pulse energy is a sensible choice, but there are two ways of stating it, stored and output!
Those brands using "stored" sound like they have larger energy levels. It's a bit like audio speaker or amplifiers ratings, peak music power output (PMPO) and RMS power. You may be surprised to learn that a 200W PMPO speaker is actually only as good as a 3W RMS one.
The difference between stored and output Joules in electric fence energisers is not that large. A reliable rule of thumb is for every 1J stored an energiser will deliver about 0.75J output. So a 15 Joule stored energiser is about the same as a 10 Joule output energiser.

Stored Joules

Stored Joules is a measure of the amount of electrical energy stored in the main capacitor just before each pulse.
The Formula is J = 1/2CV^2.
Where J is the stored joules, C is the main capacitor size in Farads, V is the peak charge voltage and ^2 means squared.

Output Joules

Output Joules is a measure of the amount of electrical energy transferred to a particular load per pulse. If output Joules is quoted without the word peak, you can assume it is the peak or maximum that unit is capable of into any load.
The Formula is J = integral from 0-T of v(t)^2/R.
Where J is the output joules, T is the pulse length, v(t) is the voltage time curve and R is the load resistance.

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Low voltage problems

Think carefully before running leadout cable underground for more than 20m. Underground cable places a capacitive load on the energiser about 10 times greater than a similar length of standard fence. This can lead to a lower then expected voltage on the fence. A more common problem, however, is insufficient earthing. I can’t stress enough how important a good earth is. If you are not getting high enough voltage on a fence (and you’re sure there are no faults) try adding more earth stakes. It's probably the simplest thing to do anyway, and it’s surprising how often it makes a difference.
If you have a Power Probe (R) or a standard electric fence voltmeter you can test your earth.
With the Power Probe simply place the tip of the probe on the top of the earth stake and place your other hand on the ground as far away from the earth as possible (stretch).
If you are using a leaded voltmeter put one lead on the earth stake and use small temporary earth rod for the other.
If the reading is over 0.3kV your earth is probably not good enough.
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Fault Finding on Multiple Live Wires

The following assumes you have a Directional Fault Finder .
It is good practice to have several live wires, especially on main feeder lines. If the fault is some distance away the current flowing to the fault may be equally shared on two (or more) live wires. When there are two (or more) live wires the user should test both (or all) live wires in the same way. Situations will occur where all the fault current is flowing in one wire, and even where the direction is different from one wire to the next. In all cases following the largest current reading will result in the least time.
If you are building a new fence with multiple live wires I recommend joining the live wires together before and after each strainer. This will increase the voltage on long fences. The only time not to do this is if you intend to disconnect the lower wire in times of heavy growth or snow.
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Problems With Digital TV Reception

Electric fences can cause problems with Digital TV reception, especially in marginal signal areas. Here are some ways that the problem can be minimised:

• Check all fence connections on the live wires, especially on main feed lines where the current is higher. Use galvanised connection bolts rather than simply twisting wires together. Poor fence connections that arc can generate large amounts of electrical noise which will interfere with wireless equipment.
• Check for fence faults. Any fence fault which causes even tiny amounts of arcing (wet grass or succulent weeds touching the live wire for example) will again generate electrical noise. If you have a directional fault finder you will save yourself time here.
• Check the electric fence earth (ground). Poor grounding can also cause an electric fence to emit excessive electrical noise. Also check that your fence earth stake is separated from your mains power ground. Having an electric fence ground too close to the earth stake of your mains power can cause noise to be injected directly into your TV or digital set top box through electrical outlets in your home.
• Running a Bi-polar fence will help minimize the problem. In a Bi-polar system the voltage on individual wires is lower, which means less noise will be transmitted from the fence (which is acting as a huge antenna). Also, because the voltage on one wire is positive and the other wire is negative (balanced) the any noise which is generated will be cancelled out to a certain extent.
• Upgrade your antenna, add a mast head amplifier or reposition the antenna so that it is higher and more likely to get a better signal.

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Auto-Sync ™ (Pakton Technologies' Press Release)

OVERVIEW

Auto-SyncTM is a patent pending new method of synchronising electric fence energisers designed by Pakton Technologies of Queensland, Australia. Auto-SyncTM detects when something, or someone, touches the wires from two different electric fences and synchronises the output pulses so that the potentially dangerous condition of receiving more than one pulse per second is avoided. Although international safety standards require a 2.5 metre gap between live wires powered from two different unsynchronised energisers, through neglect or ignorance, this is often not adhered to. For example live wires running down both sides of farm dividing fences are a common site in rural Australia. Where electric fences are used for perimeter security this problem can also occur at the corner between two or more neighbouring fences. Through intelligent design, Auto-SyncTM is able to detect a significant cross coupled signal on the fence live wire and determine if the signal was caused by another energiser. If so it will synchronise its own high voltage pulse to match the timing of the other fence. An Auto-SyncTM energiser can synchronise with any other brand of energiser provided that energiser conforms to international standards regarding pulse timing.

WHY ARE SYNCHRONISED ELECTRIC FENCES IMPORTANT?

The magnitude and frequency of the electric pulse is restricted by safety standards such as IEC60335.2.76. This limitation is specifically intended to ensure that the shock received from the energiser (and hence the fence) is safe for humans. An important part of the safety requirement is that the person receives no more than one shock per second. When the pulses are one second or more apart the human body treats them as separate events and the heart is unaffected. Receiving more than one pulse per second, especially for a prolonged time, can interrupt the natural rhythm of the heart. While it is very unlikely that someone would voluntarily touch an electric fence for a prolonged time, it is possible, especially if they were to become entangled in the fence. If a person were to touch with a live wire on the fence with one hand and another live wire on another fence with the other hand they would receive a shock from both fences and if the energisers powering those fences are not pulsing at the same time (synchronised) the person will receive more than one shock per second. If however the two energisers were synchronised so that the pulses occur at the same time (or at least within 10 milliseconds of each other) the person will only receive one shock per second and be in less danger.

APPLICATIONS FOR AUTO-SYNC

Auto-SyncTM will be applied progressively to Pakton products from 2011 onwards. The owner will notice that the Auto-SyncTM energiser will tick in synchronous time with any other energiser whose signal is “picked up” on the live wire. This could lead to the energiser seeming to miss a beat every now and again as it detects and synchronises to another unit. Auto–SyncTM will also be applied to Pakton’s security electric fence energisers as a “fall back” synchronisation method. For larger multi-energiser systems, Pakton security energisers are already able to be synchronised using Pakton’s patented Group Synchronous Pulse technology. Auto-SyncTM will be particularly effective where smaller premises are protected by single energisers and where neighbouring properties also have security electric fences. The added safety of the Auto-SyncTM energiser will be particularly useful on farms where neighbours also use electric fences on the dividing fence. It will also be helpful on large properties where several energisers are used for different parts of the same farm. Many farmers choose to use more than one energiser for the following reasons.

• It reduces the area which a fault will affect.
• Medium powered energisers, say up to 12 Joules, are less expensive to buy or repair and it is easier to afford a spare.
• Using multiple smaller energisers is increasingly being seen as a safer alternative to high powered units. The safety of the highest powered units has been questioned. As a result in Europe the very large energisers have now been banned.

For more information contact sales@pakton.com.au or see www.pakton.com.au
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