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Module 2 : Current and Voltage Transformers

Lecture 7 : CT Saturation and DC Offset Current

7.2	CT Saturation due to DC - Offset Current
	We now plan to show that CT can saturate on dc offset current. Also, we plan to show that the resulting distortions in the CT secondary current can be unacceptably high. While doing this analysis, we will neglect ac symmetrical component. Note that when a CT core is saturated, it cannot replicate the ac component as the strong mutual coupling between primary and secondary is lost.

		First consider an ideal CT excited by the dc offset current source. An ideal CT will faithfully replicate the primary current waveform on the secondary side. Hence, the secondary current would be given by and the voltage developed across CT secondary would be given by Typical voltage waveform is shown in fig 7.4.