Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This one, concerning how to carry out touch voltage measurements, is answered by Fluke:
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| Fluke's 165X series multifunction tester. |
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Question: Can you please tell me how to measure touch voltage in domestic and commercial premises?
Answer: The touch voltage is usually defined as the difference in potential between a point on the earth's surface, where a person is standing, and an exposed metallic structure (present or future) within reach of that person. Since all metallic structures within a substation should be bonded to the grounding grid, touch voltages are calculated by computing the difference in potential between the grounding grid and earth surface points.
ANSI/IEEE Standard 80-2000 (North America) and IEC 479-1 (Europe) provide methodologies for determining maximum acceptable touch and step voltages, based on the minimum current required to induce ventricular fibrillation in a human subject. This is typically 50V in commercial and domestic premises, and 25V in agricultural areas. Therefore, typical instruments used to measure touch voltage will not measure exact values but only warn you if the limit has been exceeded. Instruments, such as the SM300 socket tester, and most recent multifunction testers like the Fluke 165X series, can make touch voltage measurements.
To see many more Q & A in Voltimum UK's Experts Area, please click on the link: www.voltimum.co.uk/consult.php?universe=consult.index.questions
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