Hello. I am a little bit confused about the validity of a earth measurement using a clamp unit (Fluke 1630-2).
On one of the Megger Clamp-on Ground Testing manual - see link(https://www.instrumart.com/assets/Megger-Clamp-On-Guide.pdf), it is specified that:
"The clamp-on method is effective only in situations where there are multiple grounds in parallel. It cannot be used on isolated grounds as there is no return path. Therefore, it cannot be used for installation checks or commissioning new sites."
I am not sure what it is reffering to by isolated ground... This would mean that if you disconnect the earth bar from the earth rod before measuring, your measurement will not be valid ? P.S. I have just bought a Fluke 1630-2 Earth Ground Clamp tester.
What does "return path" mean in this context?
..and will the clamp work on a de-energised system with only 1 or more electrodes which are inter connected?
I have also read on other source that:
"Earth resistance measurements with the bar closed will then be incorrect due to the presence of this de facto earth electrode. This may lead to an excessively high earth resistance value later on (if a metal duct is replaced with an insulating material, for example). Consequently, unless you are sure that there is no de facto earth electrode, you must open the earth bar for any earth resistance measurements"
On one of the Megger Clamp-on Ground Testing manual - see link(https://www.instrumart.com/assets/Megger-Clamp-On-Guide.pdf), it is specified that:
"The clamp-on method is effective only in situations where there are multiple grounds in parallel. It cannot be used on isolated grounds as there is no return path. Therefore, it cannot be used for installation checks or commissioning new sites."
I am not sure what it is reffering to by isolated ground... This would mean that if you disconnect the earth bar from the earth rod before measuring, your measurement will not be valid ? P.S. I have just bought a Fluke 1630-2 Earth Ground Clamp tester.
What does "return path" mean in this context?
..and will the clamp work on a de-energised system with only 1 or more electrodes which are inter connected?
I have also read on other source that:
"Earth resistance measurements with the bar closed will then be incorrect due to the presence of this de facto earth electrode. This may lead to an excessively high earth resistance value later on (if a metal duct is replaced with an insulating material, for example). Consequently, unless you are sure that there is no de facto earth electrode, you must open the earth bar for any earth resistance measurements"
