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IAEI Magazine | Author: Jeff Jowett
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Jeff Jowett

Jeffrey R. Jowett is senior applications engineer with Megger in Norristown, Pennsylvania. He has written numerous trade journal articles, conducted training of distributors’ sales staffs and customers, and given seminars, training sessions and talks to various electrical societies [including InterNational Electrical Testing Association (NETA) and National Joint Apprenticeship Training Committee (NJATC)], and to those open to the general industry public. He is a member IEEE, and is on the committee for the revision of Standard 81, Recommended Guide for Measuring Ground Resistance and Potential Gradients in the Earth. He has been employed for more than thirty years in electrical test and measurement instrumentation; first with Biddle, then AVO International and now Megger.


Testing 600-V Cable

There are a variety of technologies and methods used to test the insulation of wire and cable, including high-potting, very low frequency (VLF), power factor, partial discharge, time-domain reflectometry (TDR), and "thumping.” Like a visit to the doctor’s office, each test examines the test item in a different way and looks for a different response from the insulating material. Which test(s) and how many to employ is a judicious decision to be made by a skilled technician. This article will focus only on the most basic and fundamental test, insulation resistance. There is still debate among industry professionals regarding the value of testing, when and how often, what techniques and voltages to employ, and so on. Differing opinions and advice are available in the literature. This article is based on the acceptance of testing as being of fundamental value.