The Over current coefficient (Ksi) of a current transformer can be defined in terms of its rated primary and short time withstand current as follows:

Knowing the value of this factor allows us to know whether a CT will be easy to manufacture or otherwise as follows:

• The lower Ksi is, the easier the CT will be to manufacture.
• A high Ksi leads to over-dimensioning of the primary winding's section; the number of primary turns will therefore be limited together with the induced electromotive force; the CT will be even more difficult to produce.

Released for: Schneider Electric Saudi Arabia