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Electricians' question
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Is it possible to measure earth current leakage on a Megger, or is a clamp meter the only way?
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For more on marking an answer as the "Best Answer", please visit our FAQ.The problem with using a clamp meter is their accuracy at low currents. The most accurate method is to break the earth path and insert an ammeter in line. This technique could result in a hazardous situation with the meter impedance (albeit quite low) in the earth path.
Most PAT testers will perform this measurement on individual appliances – but I guess your question relates to wiring installations and the earth leakage due to the electrical equipment within the building.
Most PAT testers will perform this measurement on individual appliances – but I guess your question relates to wiring installations and the earth leakage due to the electrical equipment within the building.
I stand corrected by Bright Spark.
I regularly use clamp meters in my work, mostly in the 1A-50A range and was not aware that they are now available with mA ranges – this one looks just the job for a sparky wanting to investigate earth leakage circuit breakers breaking.
http:// www.eba y.co.uk ...0&ha sh=item 33675d6 76f
But I don’t believe it has an accuracy of 2% on a 2mA range (as claimed).
I regularly use clamp meters in my work, mostly in the 1A-50A range and was not aware that they are now available with mA ranges – this one looks just the job for a sparky wanting to investigate earth leakage circuit breakers breaking.
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But I don’t believe it has an accuracy of 2% on a 2mA range (as claimed).
Having said the above product would be suitable to investigate nuisance tripping of ELCB’s – one additional feature (not on this product) would be the ability to display (hold) the peak current. This would allow confirmation of a suspected current spike, causing the trip to operate.
Something to bear in mind is that ELCB’s operate by detecting an imbalance in the current between the supply and return conductors – quite a neat trick when you consider that they are detecting a difference of 30mA in a total load of 30A (they do not directly measure the earth conductor current). Some are prone to operate due to the intermittent operation of inductive loads (such as a drill), possibly due to the resulting electrical noise.
Something to bear in mind is that ELCB’s operate by detecting an imbalance in the current between the supply and return conductors – quite a neat trick when you consider that they are detecting a difference of 30mA in a total load of 30A (they do not directly measure the earth conductor current). Some are prone to operate due to the intermittent operation of inductive loads (such as a drill), possibly due to the resulting electrical noise.