Application Cases

Experiment Name: Study on Space Charge Distribution in Polyethylene under Alternating Electric Fields

Testing Equipment: High-voltage amplifier, piezoelectric sensor, oscilloscope, electrodes, etc.

Figure 1: Structural Diagram of the Alternating Space Charge Test Platform

Experiment Process:

I. Alternating High-Voltage Source

The alternating high-voltage source provides the high-voltage electric field environment required for sample testing. A high-voltage amplifier is used, which requires a low-amplitude control signal as input. The high-voltage amplifier amplifies the control signal and outputs it.

II. PEA Test Platform

As shown in Figure 1, the PEA test platform includes components such as electrodes, sensors, and amplifiers. The alternating voltage is connected to the upper electrode via a metal rod, which is insulated and passes through the electrode housing. To optimize the electric field distribution at the interface and prevent corona discharge at the tip, a voltage equalizing sphere is used. The pulse source is connected to the side BNC interface of the electrode, and the pulse is coupled to the sample via capacitor C0. Capacitor C0 also isolates the alternating high voltage to protect the pulse source from damage. The entire electrode is tightly contacted with the sample after being fixed with fasteners and can be conveniently disassembled when replacing the sample. A semiconductor thin film is placed between the upper electrode and the sample to optimize the electric field distribution and absorb upward-propagating acoustic waves from the sample, reducing the impact of reflected acoustic waves on the measurement results.

III. Data Acquisition Module

A high-performance oscilloscope rapidly acquires and saves space charge at different phases under the alternating electric field. The data volume of space charge collected under the alternating electric field is large, and due to data transmission speed limitations, this paper adopts an offline processing method. The acquired space charge signals are first stored in the oscilloscope and then processed on a computer using specialized software for averaging and recovery.

IV. Design of Measurement System Structure

Figure 2: Schematic Diagram of the Alternating Electric Field Space Charge Measurement System

The basic principle of the PEA method for alternating electric field space charge testing is shown in Figure 2. The high-voltage power supply provides the alternating electric field, and the pulse source provides pulse excitation. Both the alternating and pulse electric fields are coupled onto the sample under test. The mechanical acoustic waves generated by the space charge in the sample are converted into electrical signals by the sensor, amplified, and saved in the oscilloscope. The charge quantity and location of the space charge are determined by the intensity and propagation arrival time of the detected electrical signals.

V. Test Software

Test software was developed based on LabVIEW, integrating parameter settings within the software. The computer connects to the oscilloscope, pulse source, and function generator via twisted pair and RS232 serial interfaces to achieve unified control.

Experimental Results:

The components of the alternating electric field space charge measurement system, except for the pulse source, were designed and compared: a function generator and high-voltage amplifier were used to produce alternating high voltage; a test platform was designed to quantify space charge into electrical signal outputs; a high-performance oscilloscope was selected for space charge signal acquisition after comparing digital signal averagers and oscilloscopes; a pure resistive voltage divider was designed to monitor the voltage applied to the sample.

All modules and components were integrated to build a complete alternating electric field space charge test system. The measurement system can achieve space charge measurement, acquisition, and saving at 20 to 60 phase points within a single 50 Hz cycle, with the phase span of the pulse cluster applied at each phase point being within 2 degrees.

Voltage Amplifier Recommendation: ATA-7030

Figure: Specification Parameters of the ATA-7030 High-Voltage Amplifier

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