Question

Which one of the following types of instruments can be used to determine the r.m.s value of ac voltage of high magnitude (10kV) and of any wave shape?
1. Moving iron instruments
2. Dynamometer type instruments
3. Induction instruments
4. Electrostatic instruments

Answer 1

Correct Answer - Option 4 : Electrostatic instruments

Electrostatic voltmeters are used to measure very high voltages and they offer very high accuracy. These can be used up to 100 kHz without serious loss of accuracy.

Hence electrostatic voltmeters are most suitable to measure upto 500 kV AC voltage.

Deflecting torque is given by

\(T = \frac{1}{2}{V^2}\left( {\frac{{dc}}{{d \theta }}} \right)\)