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| Analysis of Charge-Carrier Transport Characteristics of Transformer Oil-Based Nanofluids |
| Dong Ming, Yang Kaige, Ma Xinyi, Hu Yizhuo, Xie Jiacheng, Xu Guanghao |
| College of Electrical Engineering Xi'an Jiaotong University Xi'an 710049 China |
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Abstract Adding nanoparticles to traditional transformer oil can improve the heat exchange properties and enhance the dielectric withstand characteristics. The research on the charge-carrier transport characteristics of these transformer oil-based nanofluids (TNFs) can explain their improved insulating characteristics and clarify the mechanisms dictating these modifications. In this paper, the conduction current and velocity field of TNFs under high electric field excitation were measured for the first time, and the charge-carrier transport characteristics were analyzed. According to the magnitude of the applied electric field, the transport process can be divided into three stages: Ohmic, tunneling, and space charge limited current (SCLC) stages. In the Ohmic stage, the electric field strength is very low, and the addition of nanoparticles increases the conduction current and the number of carriers. In the tunneling stage (medium-to-high electric field strengths), the predominant charge carriers in the TNFs change from ions and colloidal particles to electrons emitted from the electrode. The thickness of the Schottky barrier at the metal-liquid interface increases on the addition of nanoparticles, which reduces the number of electrons that pass through to the interface region. The field strength required for electron transmission is enhanced, and the insulation strength is improved. In the SCLC stage (very high electric fields), the carrier mobility is reduced because the trap density of TNFs is larger and the electrical discharge is suppressed.
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Received: 09 August 2019
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2020, Vol. 35 
