Characteristics of the D-Dot Sensor for Measurement of High Voltage Pulse of a Water-Insulated Transmission Line

The characteristics of the differential-output D-dot sensor, which is employed to diagnose the voltage pulse across the water-insulated component of the pulsed power accelerator, are investigated by theory, circuit simulation, and experiments. The leakage current from the D-dot sensor to the inner electrode of the measured component will degrade the low-frequency response property of the monitor. The lower level of the water medium resistivity the worse performance of the sensor's low-frequency response property will be. The actual lower-limited response frequency of the D-dot sensor is not related to the sensor itself but is mainly determined by the resistivity of the water. These are not only deduced from theory but also approved by the experimental results. Circuit simulation results suggest that the D-dot sensor without consideration of the leakage current will over-evaluate the amplitude and rise time of the voltage pulse across the water-filled element. We have proposed a method to make compensation for such an effect by using a passive resistor-capacitor (RC) integrator instead of the numerical process suggested previously. It is approved both by circuit simulation and experimental results that the output of the D-dot sensor post-processed by the RC integrator could give accurate measurement results providing that the time constant of the RC integrator is identical to the characteristic time of the D-dot sensor.