AC Leakage In Third Harmonic Current Tester

<third harminics leakage current>

Eh?

The third harmonic is a waveform distortion, at three times the fundamental frequency, that is an expression of the departure of a waveform from a pure sine-wave shape at the fundamental frequency. To use a musical analogy, the G in the second octave above middle C is its third harmonic. Harmonics can be measured using a frequency-domain instrument such as a spectrum analyser.

Leakage current in an electrical system is the difference between the vector sum of the instantaneous currents on each phase conductor and the instantaneous current vector in the neutral conductor. This current appears in the earth conductor and its presence is mostly used to determine and isolate an insulation fault among the other conductors. A simple ammeter placed in the earth conductor would measure this current, though it needs to be carried out under closely-controlled conditions to prevent user electric shock.

Without further information, they are two unrelated concepts.

The missing information that you asked for, is the "arrestor" that tecspert did mention ie. surge-arrestor; these are non-linear devices that conduct more as the 50Hz (or 60Hz) sine voltage increases. The surge-arrestor will conduct exponentially increasing amounts of current as the 50Hz sine voltage goes through its peaks. This leakage current can have high levels of 3rd harmonic (and other odd harmonics). It is therefore useful to measure the 3rd harmonic content of current through the surge-arrestor to test its health and also monitor whether the correct surge-arrestor type has been installed.

We may be able to help you... take a look at our website and drop me an email, and we can talk about physical configurations and other requirements etc.

www.suretech.co.za

NeilJ