1. If any reason CT secondary is kept open the very high load current is passing through the primary winding of CT which will create the Strong magnetic field 2. This Strong magnetic field will be link to the Secondary winding of the CT 3. If no current flows in secondary, no ampere turns are produced by the secondary circuit. 4. For CT Secondary there are large no of turns, magnetic field also strong So as per Faraday's law the very high voltage will be induced in CT.
At the same time
➢ The operator can get electrical shock of that voltage
➢ The CT insulation may Failure
➢ The ratio error and phase angle errors are likely to be much increased by such misconnection.