Design of a novel Rogowski coil with function of overcurrent protection

Gas discharge includes many pre-discharge current pulses with rise time of several nanoseconds and amplitude of several milliamperes. The breakdown current after pre-discharge process can reach up to several kiloamperes. To measure pre-discharge current safely and accurately, a novel current transducer should be developed. The scheme that a transient voltage suppressor (TVS) paralleled with self-integral resistor of Rogowski coil was adopted and a novel Rogowski coil with the function of overcurrent protection was designed. The parameters of integral resistor and overvoltage protection device were optimized by many experiments. The results showed that the integral resistor should decrease when the measuring sensitivity was satisfied, and the optimal value of resistance was 10Ω∼50Ω. The response time of overvoltage protection device should be smaller than rise time of measurement current. The distributed capacitance of TVS, which could not exceed 0.5nF∼1nF, should decrease when the peak current of Rogowski coil was larger than breakdown current of the circuit. The test results show that the newly developed Rogowski coil can measure current with a rise time smaller than 5ns and amplitude of several milliamperes accurately, and can also protect posteriori measuring equipment when large current up to several kiloamperes appears.