o Primary winding connects in series with line carrying the current to be measured.
o Primary consists of very few turns causing no appreciable voltage across it.
o Secondary winding has larger number of turns.
o Ammeter is connected directly across the secondary terminals.
o Thus, a current transformer operates its secondary nearly under “short circuit” condition.
o One of the terminals of secondary winding is earthed to protect equipment and personnel in the vicinity in the event of an insulation breakdown.