Demodulated Waveforms: Arcing

Arcing is one of the most destructive processes associated with Electromagnetic Interference analysis. It is a relatively high-energy discharge of current and is seen many times in combination with lower-level discharge types such as gap discharge and corona. It’s primary characteristic is a high-energy discharge with a broad base rather than a sharp peak with a narrow base.

Arcing is sometimes interpreted as gap discharge because in many cases, the arc is across a conductor gap. However, arcing tends to be more erratic than a pure gap discharge signature and has more energy content. As the system deteriorates, the arcing patterns can get very close together.

This type of signature, seen quite often in the higher frequency bands, are attributed to issues in the Generator Output Bus (Isolated Phase bus, Segmented Bus, Non-segmented Bus, Cable Bus) and can be due to bad connections at the bus transitional areas (flex links, bolted connections).

If this arcing signature is seen in the lower frequencies, it could be attributed to loose connections on power rectifier circuits and exciter connections.

If this arcing signature is seen in the middle frequencies, it could be attributed to cracked strands, bad braze joints, and bad connections on internal phase connections. It is rare to see this signature in the middle frequencies, and it would be high concern for the health of the generator internals.

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