A High-Speed Dynamic Measurement System for Transient Space Charge in Insulation Materials

It is of great significance for insulation design, reliability evaluation, and new material development to obtain the transient evolution process of space charge in insulation materials by actual measurement. With the development of hardware technology in recent years, it is possible for high-speed, dynamic, and continuous space charge measurement. This article adopts an oscilloscope with 500 MB storage, a high-frequency pulse power supply (up to 1 MHz), and the high-speed dynamic measurement of space charge is realized based on the PEA method. Meanwhile, in the strong electric field conditions, the average sampling mode is no longer used, reducing the time interval of the measured waveform. But the signal-to-noise ratio becomes worse and corresponding strategies for signal recovery is put forward as well. In this paper, transient space charge is measured in the polyethylene or oil-paper insulation samples under the conditions of DC prebreakdown test, high temperature, and polarity reversal. It is found that a large amount of space charge, including packet-like space charge, could inject and migrate in millisecond time scale, and caused severe distortion and oscillation of the electric field inside the insulation. The high-speed dynamic space charge measurement technology and system introduced in this paper provide an important perspective to solve the bottleneck problem in the research of transient process of insulation materials.