Contents
POTENTIAL TRANSFORMERS

Insulation Resistance test a in the case of C.Ts may be carried out. For P.Ts suitable for use between phase  and ground, this test is meaningless as the Insulation Resistance recorded shall be that of lower end of the  primary which is at near earth potential. For conduction of I.R. test on such P.Ts. only 1 kV meggar may be  used.

Insulation Resistance of secondary may be measured, as in the case of C.Ts. by using a  1kV meggar.

The ratio of the P.T. may be ascertained by applying a small voltage to the primary and   measuring the proportional voltage appearing across the secondary. Here again the recorded ratio may not be exactly same as the ratio indicated on the label because of the difficulty of recording two voltmeters’ readings simultaneously.

If considered feasible, polarity test on P.T. windings may be carried out by using a 1.5 dry battery cell as in the case of C.Ts.