MEASUREMENT TECHNIQUES
Measuring Ground Currents
 

Correctly measuring ground and/or residual current (the more correct name for "earth leakage current") is of prime concern as one must determine the characteristics of the current e.g. whether the residual current is capacitive and/or resistive.

But first,

If there was one thing I had the power to ban from existence it would be the low-current clamp-on ammeter! Some companies even have the audacity to refer to them as "earth leakage current clamps". They are useless in determining residual current issues. They firstly do not have the speed to pick up any high speed noise, and/or a means to tell you what it is you're measuring! (apart from RMS current, that is).

OK, I'll settle for allowing their use to determine there is a form of current flowing through, for example, a circuit protective conductor (CPC), but that's about it. Don't for one moment think they are accurate or will provide any means of problem identification. Once it is determined a current is flowing, it requires more appropriate kit to go the rest of the road!



READ FIRST

There are two requirements that must be fulfilled before you even think of starting.

  1. You must have the proper kit! I know this sounds logical, but I have seen people try to measure residual current with a current clamp fed in to a multimeter or a low-current clamp-on style ammeter. As said, you cannot do this. You will only be fooling yourself.

  2. You must understand the readings being shown to you (by the proper kit, naturally!). Too many electrical engineers "sign off" an installation when there has been a serious error because they "discarded" the current reading - "oh, on a building this large, we'd expect a current like this", or, "it is a lot of IT equipment so a high leakage is no call for concern". All I can say is "hmm!"

If, and only if these two items can be satisfied, then proceed with pleasure. If not, then please send me an order number to come and do the proper job for you.

Measuring Residual Currents  >>


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© 19.10.04