Application Cases

Experiment Name: Application of High-Voltage Amplifier in the Analysis of Surface Tracking Corrosion Degree Based on Insulation Resistance

Experiment Objective:
To evaluate the tracking resistance performance of ethylene-propylene rubber (EPR) according to tracking test standards, extract characteristic quantities of tracking faults, study fault diagnosis methods for tracking, and assess the surface tracking condition of EPR.

Experimental Equipment:
EPR samples with varying degrees of tracking treatment, ATA-7020 high-voltage amplifier, three-electrode system, drying oven

Experimental Content:
Based on the tracking tests, the insulation performance of each EPR sample was measured after the tests. The insulation resistance was analyzed using volume resistance, polarization-depolarization current, and return voltage. First, the volume resistance, polarization-depolarization current, and return voltage of each sample were measured in a drying oven under different measurement voltages and temperatures. Second, the influence of different fault levels on volume resistance, polarization-depolarization current, and return voltage was analyzed in detail. Finally, the insulation resistance obtained from different measurement methods was compared to verify the reliability of the methods.

Experimental Procedure:

(1) Polarization-depolarization current of EPR:
The figure below shows the measurement circuit for polarization-depolarization current. During the depolarization process, the current flowing through the EPR insulation is capacitive, with a magnitude in the pA range. Therefore, accurate measurement of the depolarization current requires high-performance equipment. In the measurement system, a KEITHLEY-6517B was selected as the ammeter, and an ATA-7020 high-voltage amplifier was chosen as the high-voltage DC power supply. This DC source has the advantage of low noise, ensuring the reliability of the measured data. A three-electrode structure was used for measurement, where the high-voltage terminal and measurement terminal were used for polarization-depolarization current measurement. The host computer saved the real-time data transmitted from the 6517B via the serial port.

Figure: Measurement Circuit Diagram

(2) Return voltage of EPR:
The return voltage method is based on dielectric response theory and is a way to characterize dielectric polarization in the time domain. During measurement, the return voltage is less susceptible to external electromagnetic interference, providing relatively stable results that are easy to observe.

Figure: Measurement Circuit Diagram for Return Voltage

The measurement circuit for return voltage is shown in the figure. The DC voltage source used was the ATA-7020 high-voltage amplifier, with a voltage value of 400 V selected for measurement. The voltage measurement range of the KEITHLEY-6517B voltage measurement unit fully met the measurement requirements. After measurement, the host computer saved the real-time data transmitted from the 6517B via the serial port.

Experimental Results:

(1) Influence of tracking size:
In the initial stage of discharge, as the degree of tracking corrosion increased, both the initial current and the discharge rate during the depolarization process gradually increased. The more severe the tracking corrosion, the higher the stabilized current value at the end of depolarization decay. The experimental results show significant differences in the depolarization current curves of the different samples. The depolarization current decay exhibited a concave point throughout the entire depolarization process.

Figure: Depolarization Current at Different Tracking Development Stages

Figure: Depolarization Current at Different Tracking Development Stages in Logarithmic Coordinates

(2) As the degree of tracking corrosion and insulation contamination increased, the volume resistance of EPR gradually decreased, while the polarization-depolarization current and return voltage gradually increased. This indicates that the magnitude and variation of insulation resistance, polarization-depolarization current, and return voltage can reflect the insulation fault condition.

Figure: Return Voltage at Different Tracking Corrosion Levels

Figure: Return Voltage at Different Carbon Powder Contamination Levels

Figure: Specifications of the ATA-7020 High-Voltage Amplifier