Three Phase sine wave with 1050 Hz ripple

Set up to check the signal strength of the Zellweger ripple injection plant.
I use a 2 channel oscilloscope with the 3rd channel at the lower part of the screen as I can not center the third channel.
The 1050 Hz can be seen sliding over the sine-wave
Ripple voltage is around 6 Volts @ 1050 Hz. superimposed upon the 11kV / 240 Volts supply.

Видео Three Phase sine wave with 1050 Hz ripple канала RODALCO2007