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Proceedings Paper

Infrared thermography and overloaded neutral conductors
Author(s): John McComb; Hector E. Niebla
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Paper Abstract

Present findings of two recent case studies. One involves transformer failures on three computer-stores within eight hours of their grand opening. The second discusses the findings during an infrared thermography-training course for electric utility engineers of a transformer vault serving an industrial customer. Both of these deal with overloaded neutral conductors. Historically, the average neutral conductor carried only the imbalance of the current between the phases of a three-phase system. This current was typically small in relation to the load being served. In fact, for economic reasons many neutrals were installed smaller than their associated phase conductors. Today however, certain types of loads (non-linear loads such as computers) and certain transformer connections (4 bushing single phase with a collector bus) cause the neutral to have up to three times as much amperage as the phase conductors. This paper will discuss the conditions under which such loading occurs and further investigate steps that can be taken/recommended should an infrared test indicate an overloaded neutral conductor.

Paper Details

Date Published: 19 March 1999
PDF: 5 pages
Proc. SPIE 3700, Thermosense XXI, (19 March 1999); doi: 10.1117/12.342294
Show Author Affiliations
John McComb, Florida Power & Light (United States)
Hector E. Niebla, Florida Power & Light (United States)


Published in SPIE Proceedings Vol. 3700:
Thermosense XXI
Dennis H. LeMieux; John R. Snell, Editor(s)

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