Testing a Lightning Protection Grid with a Clamp on Ground Tester

[mikelp]

I recently purchased a clamp on ground resistance tester made by AEMC Instruments. It was purchased on the advice of an industry engineer. I have yet to use it, but wondered if anyone else had any experience with this type of instrument for the purposes of testing the grid and mechanical connection integrity on different parts of the grid. I have read the instructions that came with the tester, though no part therein expressly addresses the testing that I wish to do. As the lightning protection grid in question was installed by my company, I can be assured that the grid is solidly fastened to the main electrical ground rod system which in turn is bonded to the utility neutral connection in the main switchgear. According to the directions supplied with the tester, the theory of proper operation of this tool relies on that connection to the system power neutral bond connection.

The model # is AEMC 3731. If any one has experience good, bad or words of wisdom to share on the utilization of this tool for the purpose I intend to employ it, please do not hesitate. I welcome all feed back.

Regards,

MP

 

[alehman]

Searth this forum for several threads on clamp-on resistance testers. To obtain meaningful results, they must be used with great care and a thorough understanding what is being measured. You must assure that the conductor where you are measuring is the only matallic path between the two electrodes being tested.

AEMC's web site has some articles on how to properly apply these instruments.

 

[jghrist]

The tester is for testing ground resistance not mechanical connection integrity.

 

[mikelp]

By the fact that you do not need to disconnect wires to test them, would that not in fact be testing the mechanical connections? Perhaps "mechanical Integrity" was a poor choice of words when in fact I meant to say that it would be evaluating the continuity of the grounds via the splices therefore indicating good or bad mechanical connections.

 

[jghrist]

I'm not sure how you would test continuity. If you measured the resistance of the whole grid and got 3 ohms, then measured one part and got 5 ohms, this doesn't prove that the parts are connected. They could be disconnected with the first part alone having a 3 ohm resistance and the second part alone having a resistance of 5 ohms. Or, they could be connected with the entire grid having a resistance of 3 ohms and the second part alone having a resistance of 5 ohms.