Demodulated Waveforms: Random Noise

In general, random noise is created by contamination of some kind.

For example, in a motor, random noise developed due to salt contamination on the windings, and in a generator, it was from water/algae contamination. In the motor example, only the middle two bands were affected. For the motor, survey data was only taken up to 10 MHz. In the generator example, all frequency bands were affected due to the severe nature of the contamination.

For random noise events you generally get a broad area of interest.

In general, there is no voltage dependence (i.e. sine wave pattern like corona).

In some cases, in the excitation frequency band, you need to be aware of the random noise process that is between the exciter SCR/Thyristor spikes. As dirt and contamination builds on the voltage regulator/exciter diode area, the random noise levels between the diode pulses increase. This Indicates that the excitation area should be cleaned in an upcoming outage.

Monitor Liquid Level detector usage to help determine if this signal is caused by water leakage into the component.

While this condition may seem to be benign, the contamination can lead to insulation degradation which leads to full insulation failure.

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