Page 192 - Intro Predictive Maintenance

Thermography 183

Other Problems

• Broken strands. These hot spots are found at the support and at the cable
termination.
• Spiral heating. This is found on stranded wire, which is heavily oxidized.
The problem will show up as a hot spiral from one connection to another.
There is a load imbalance between the strands, which results in a poor
connection.
• Ground conductor. Usually there are no hot spots on a ground conductor.
They do show up, however, as hot spots when there is abnormal leakage
current to the ground. Be suspicious about such spots. Always point them
out in the inspection report.
• Parallel feeders. A cold cable indicates a problem when parallel conductors
are feeding the same load.

APPENDIX 8.1 Abbreviations
DT Delta temperature. The delta notation represents the difference in two
temperatures.
m Electrical units for ohms. Also used to describe microns in the
infrared electromagnetic scale.
°C Degrees Celsius
°F Degrees Fahrenheit

APPENDIX 8.2 Glossary

A/D conversion The conversion of continuous-type electri-
cal signals varying in amplitude, frequency,
or phase into proportional, discrete digital
signals by means of an analog–digital
converter.

Absorptivity Ratio of the absorbed to incident electro-
magnetic radiation on a surface.
Ambient temperature Ambient temperature is the temperature of
the air in the immediate neighborhood of
the equipment.

Analog data Data represented in continuous form, as
contrasted with digital data having discrete
values.
Atmospheric absorption The process whereby some or all of the
energy of soundwaves or electromagnetic
waves is transferred to the constituents of
the atmosphere.