Application Cases

Experiment Name: Research on Nonlinear Characteristics of Dielectric Response in Transformer Oil-Paper Insulation and Its Time-Frequency Domain Conversion Method

Research Direction: Dielectric Response, Nonlinear Characteristics

Experimental Principle: For time-domain and frequency-domain dielectric response testing, the most important aspects are the generation of the excitation voltage and the acquisition of the response current. It is essential to ensure the accuracy and distortion-free nature of the input and output waveforms, and to确定 (确定, determine) that the effective signal is not masked by electromagnetic interference in the environment.

Testing Equipment: Data Acquisition Card, ATA-7030 High-Voltage Amplifier, Weak Current Preamplifier, Gear-Shifting Communication Control Circuit

Experimental Procedure:
Using a LabVIEW test program, a digital waveform is output and converted via digital-to-analog conversion to obtain the model waveform. The analog excitation voltage signal is amplified by a high-voltage amplifier and applied to the insulation under test. The acquired current signal is effectively amplified and filtered. The voltage and current signals are then synchronously acquired, converted via analog-to-digital conversion to the computer, and the dielectric response parameters are calculated in LabVIEW. The basic working principle is shown in the figure.

Figure: Schematic Diagram of the Test System

Experimental Results:
First, the polarization currents of oil-paper insulation with different moisture levels were tested. In the polarization current test, based on the target minimum conversion frequency of 1 mHz, the test time was set to 3201 seconds. Since oil-paper insulation macroscopically behaves as a capacitive system, the response current create an  effect  at the instant the step voltage is applied. This segment of data does not reflect the polarization characteristics of the oil-paper insulation and was therefore . To ensure sampling accuracy, the excitation voltage and response current signals were synchronously sampled at a sampling rate of 1000 Hz during the sampling process. However, using such a high sampling rate over such a long sampling time would result in excessively large amounts of sampling data, which is  for calculation. Therefore, the sampled data was resampled at a rate of 0.01 Hz to obtain the final sampling results. The polarization current test results for oil-paper insulation with different moisture levels over 3200 seconds, totaling 320,000 points, are plotted as shown in the figure below.

Figure: Polarization Current Test Results

Figure: Specifications of the ATA-7030 High-Voltage Amplifier