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What Does An Earth Leakage Clamp Meter Do?

Earth leakage is the term applied to current that flows through the protective ground conductor and into the ground, ie. to Earth. This can happen in any electrical installation and most commonly in the insulation surrounding conductors and in the filters which protect electronic equipment. This can be a problem in domestic, commercial or industrial settings because leakage current can cause intermittent tripping of electrical equipment. This can be disruptive to processes and more importantly, dangerous to the person using the equipment, and in extreme cases, accessible conductive parts can see a rise in voltage.

This leakage is caused by old or damaged insulation, which means the resistance is lower and allows more substantial current to flow. The longer capacitors will also have a higher capacitance, which causes more leakage current.

The earth leakage clamp meter and how it works

earth leakage clamp meter picture

Using an earth leakage clamp meter you will be able to if not eliminate, at least minimise the effects of the current that leaks, while also quantifying the leakage current and identifying the source.

The clamp meter works by locating the jaws around a conductor in the installation you need to test. The meter will then read the current and the value it reads depends on the strength of the magnetic field surrounding the conductor. It is important that the jaws of the meter are kept clean and are tightly closed around the conductor when testing, this is so that the jaws are protected and can measure low current levels accurately. Leakage current is shown in milliamps on the clamp meter.

Essentially, the clamp meter needs to detect the magnetic field around the conductor. This could be single core cable, a wire armour cable or the paired phase and neutral conductors of a single-phase circuit. Or it could be all the live conductors of a three-phase circuit.

Where the earth leakage clamp meter is usedearth leakage test

The clamp meter is therefore used to measure the currents passing through a conductor under test, and this could be a wide range of alternating or changing currents. This can be done quite methodically, and hence, using a clamp meter is an effective and reliable way to troubleshoot the location of your earth leakage problem. Once found, this enables you to re-distribute loads around the installation in a more balanced way. 

A clamp meter is most commonly used to measure earth leakage from RCDs, to minimise the risk of them tripping, which of course is a big problem when you are relying on RCDs to be an effective safety tool.  Certain regulations state that the total leakage current should not exceed 30% of the RCD-rated residual current. The total leakage current is the leakage current in the protective conductor plus the earth leakage current. A clamp meter is the most accurate and reliable way to measure the leakage current in this example.

Test Instrument Solutions have a range of hand-held earth leakage clamp meters which offer practical benefits to the user as well as effective and reliable readings. So, contact the our sales team to discuss which instrument would best suit your needs.

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