Polarity: Each CT should be tested individually in order to verify that the
polarity marked on the primary and secondary windings are correct. The
measuring instrument connected to the secondary of the CT should be a high
impedance voltmeter or a moving coil ammeter, with centre zero. A low voltage
battery is used in series with a push-button switch in order to energise the
primary. When the breaker is closed the measuring instrument should make a
small positive deflection, and on opening the breaker there should be a negative
deflection, if the polarity is correct.