CT Secondary Overvoltage Protector

Current transformers (CTs) are widely utilized in power systems for primary measurement and control purposes. The secondary side of a CT operates in an approximate short-circuit state, yielding a negligible output voltage. However, during operation, if the secondary circuit becomes open-circuited—or if the primary winding is subjected to abnormal currents (such as lightning currents, resonance currents, or capacitor charging currents)—overvoltages reaching several thousand, or even tens of thousands, of volts can be generated on the secondary side. This not only compromises the insulation integrity of the secondary system but can also drive the CT into saturation, leading to burnout, and may even pose a grave threat to the safety of personnel.

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