Open Circuit In A CT Secondary

If the primary circuit has current flowing the secondary circuit should never be opened.  This can cause very high voltages to occur due to the Ampere-Turns of the primary that start magnetizing the core.  This results in the core being saturated through a large portion of the cycle.  When a transformer core is saturated, it is a nontransformer.   Consequently, the transformer acts as a transformer only during a short period above and below the zero to maximum in the opposite direction.  While it is acting as a transformer it will cause very high voltage peaks.    The voltage may not appear very high when the measurement is taken with an RMS Volt-Meter but a Peak Volt-Meter would indicate a much higher peak value.  The peaks can be sufficient enough to cause death.