Second-Harmonic Contactless Method for Measurement of RMS Current Using a Standard Infrared Camera.

This article presents a new method for measuring rms values of alternative current (ac) in power lines using an infrared (IR) camera. An IR camera registers thermal images in time with an appropriate frame rate in order to calculate the spectrum of the temperature signal of a power cable. For the European standard, the amplitudes of the harmonics for $f \approx ~100$ Hz correlate to the power dissipated in a conductor. The fast Fourier transform (FFT) and rms analysis for different current values were performed. The obtained results allow plotting the calibration curve of temperature changes versus the rms values of the current flowing in wire. They confirmed the linear relation between the 100-Hz spectral component of the temperature and the square value of the rms current. This method has unique advantages. It is noncontact and makes it possible to estimate the rms current regardless of the ambient background radiation and convection cooling conditions having a significant impact on overhead lines, in particular. [ABSTRACT FROM AUTHOR]