Electric Fence Power Probe®
Commonly Asked Questions

Contents

1. How can I check the lead out cable or an underground cable?
2. What if there is more than one fault on the fence?
3. What about fences with two or more live wires?
4. What about BI-POLAR electric fences?
5. What is the difference between voltage and current?
6. Why does the Power Probe give high readings when its near the energiser?
7. My telephone clicks, does this mean I have a fault on my electric fence?
8. Why do electric fences make the telephone click?
9. How do I make sure my fence is properly grounded?

1. How can I check the lead out cable or an underground cable?

Checking insulated cables and underground cables.

Sometimes the power from the energiser doesn't even make it to the fence. The lead out wire may be shorting out somewhere between the energiser and the fence connection. Underground wires and wires which run past or through metal shed walls commonly cause problems.

To test for this place the power probe over the live lead from the energiser (try to do this at least 30cm from the energiser itself). Note the current reading (the current can be read through an insulated cable, the voltage cannot). Next take a reading where the lead out connects to the fence. If significantly (5 Amps) more current flows into the wire than comes out then there is a leak in between. The same technique may be used on underground cable by checking for a difference in current flowing into and out of the underground section.

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2. What if there is more than one fault on the fence?

When finding multiple faults, use these rules:

1. Always start at the lead out (close to the energiser)
2. Always follow the wire showing the highest current reading.

After following one direction and finding the fault go back to the lead out wire (or first intersection). Then follow the second fault direction etc.

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3. What about fences with two or more live wires?

If the fault is a long way away the fault current will usually be equally shared amongst parallel live wires. As you get closer to the fault then the wire with the fault on will carry the highest current. It is possible for some very surprising readings with multiple live wires. For example you may have the top wire reading 5 amps to the right and the next lowest reading 5 amps to the left. This could mean that this section (between strainers) is fed from the top and the lower wire is connected to it only at some later point.

There are many ways of powering multiple live wires. Some connect all live wires together at both sides of each strainer (and take one live connection around). Some take each live wire separately around strainers. With the former system you may easily disconnect sections, with the latter you may easily disconnect one live wire (e.g. the lowest).

Following the fault arrows will always lead to the fault. Follow the wire with the highest current reading. If the Digital Power Probe stops showing an arrow because the current is shared amongst many live wires proceed to the end of that section and take readings where it recombines there.

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4. What about BI-POLAR electric fences?

With the Digital Power Probe:
The Digital Power Probe has been especially designed to make fault finding on a BI-POLAR fence easier then ever before. The power Probe senses that it is being used on a BI-POLAR fence after you have touched it on both positive and negative lines. After this the Digital Power Probe will actually indicate which polarity (positive or negative) you are on. If the Power Probe is placed on the positive live wire the colon in the centre of the display will light, i.e. you will see "5.4 : 03". This enables you to be sure of which polarity wire you are on. The Power Probe will get the direction of the fault correct even when you swap from positive to negative live wires as it knows which one you are on. The only time the Power Probe will become confused is if there is a short directly between the positive and negative live wires, in this case the resulting voltage on both wires close to the fault may be zero or slightly positive or negative. The Power Probe indicates that it is longer 100% sure of which direction is correct by flashing the arrow lights.

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5. What is the difference between voltage and current?

About Voltage and Current.
Electricity can be compared to water in that, to move water (Electrons) along pipes (wires) we need to push it with a pressure (Voltage) to produce a flow (Current). If you had a large leak in a water pipe there would be a flow of water from the pump which produces the pressure to the leak.

A short circuit is like a big leak and by following the current flow the POWER PROBE will lead directly to the fault.

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6. Why does the Power Probe give high readings when it is near the energiser?

Measuring the voltage of an energiser at the energiser terminals may give misleading readings. Holding the POWER PROBE near an energiser will usually give a large current reading due to the magnetic field from the energiser transformer. The POWER PROBE has a very sensitive magnetic field pickup which will be swamped by the large field from the energiser transformer. This effect can extend to about 30cm from the energiser.

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7. My telephone clicks, does this mean I have a fault on my electric fence?

It may, however be your neighbour's fence. To find out whose fence is responsible simply turn yours off, if the clicking goes away then it is to blame.

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8. Why do electric fences make the telephone click?

An electric fence energiser places a short sharp pulse of very high voltage on the live wires. This pulse contains radio frequency energy. If there is an arcing (spark) short circuit on the fence then there may be more radio frequency noise on the live wires and the spark itself will emit radio frequency noise.

If the electric fence and telephone lines run parallel to each other then the fence acts as an aerial and some of the radio frequency energy is transferred. The amount of energy transferred depends on a lot of factors.

1. How sharp the 'front' of the pulse is from the energiser, all manufactures are starting to lessen the emissions of Radio Frequency noise in line with new international EMC standards.
2. How much current is flowing in the wire, this is why fences with faults on cause more noise.
3. How moist the air and ground is.

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9. How do I make sure my fence is properly grounded?

Place a short on your fence from live to earth, about 10m away from the earth you want to test. A quick way of doing this would be to connect the live wire to an earth wire which is touching a star picket.
Kneel down next to the main earth stake. Place the tip of the POWER PROBE on the top of the earth stake, and put your free hand on the ground about a metre away from the stake. If your fence is properly earthed, the voltage reading on the probe should read close to zero volts. If you get a reading of over 0.5kV, you may need more earth stakes. Every kV on your earth stake means a kV less on your live wires.

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