Editing Current transformer (section)

===Phase shift===
Ideally, the primary and secondary currents of a current transformer should be in phase. In practice, this is impossible, but, at normal power frequencies, [[phase shift]]s of a few tenths of a degree are achievable, while simpler CTs may have larger phase shifts. For current measurement, phase shift is immaterial as [[ammeter]]s only display the magnitude of the current. However, in [[wattmeter]]s, [[electricity meter|energy meter]]s, and [[power factor#Measurement techniques|power factor]], phase shift produces errors. For power and energy measurement, the errors are considered to be negligible at unity power factor but become more significant as the power factor approaches zero. The introduction of electronic power and energy meters has allowed current phase error to be calibrated out.<ref>{{Cite web|url=https://ctlsys.com/support/ct_phase_angle_correction/|title=CT Phase Angle Correction – Continental Control Systems|website=ctlsys.com|language=en-US|access-date=2017-09-21}}</ref>