Product Overview Current transformer (CT) is widely used in power system for primary measurement and control. During normal operation, the secondary measurement of the transformer is in an approximately short-circuit state, and the output voltage is very low. When the secondary winding is open or an abnormal current flows in the primary winding (such as lightning current, resonance overcurrent, capacitor charging current, inductor starting current, etc.), overvoltages of thousands or even tens of thousands of volts will be generated on the secondary side. This not only causes damage to the secondary system insulation, but also causes the transformer to be overexcited and burned, and even endangers the lives of workers. Using the CTB series current transformer over-voltage protector can effectively prevent accidents caused by the open circuit of the secondary side of the current transformer.