Earthing

There is one thing I don't quite understand: if you ground one leg of the instrument transformer supplying, for example 110V AC on secondary side, how voltage sinusoide will be? Full sinusoidal shape or just half of the sinusoide because every time voltage changes direction that leg is grounded and voltage will be zero. What is the true?

 

[UKEng]

You will get a full sinusoidal voltage waveform.
If you take the earth point of the transformer as the reference point then - On one half cycle the other leg is 110V (RMS) more positive than the earth point and on the other half cycle the leg is 110V (RMS) more negative. The potential difference is the same on both half cycles which is what you are interested in. The polarity of the voltage determines which direction the current will flow in and in a purely resistive circuit will result in a sinusoidal current flowing in phase with the voltage.

This is a simplistic view but I hope it helps.

Chunky (UK)