Design of Dielectric Constant Sensor for Transformer Oil Condition Detection Based on All-Metal Metamaterial

This paper proposes an all-metal metamaterial based highly sensitive sensor for the microwave section of transformer oil condition. The sensor's resonator part belongs to the Complementary Split Ring Resonator (CSRR) structure. The sensing principle of the structure is realized by utilizing the electrical properties in the transformer oil. The difference between waste transformer oil and clean oil will cause the resonant frequency of the resonator in the sensor to change. The transformer oil conditions can be detected by detecting the sensor's resonant frequency. The simulation results show that when the dielectric constant changes from 2.9 of clean oil to 2.7 of waste oil, the resonant frequency of the sensor increases from 8.184GHz to 8.486GHz, and the resonant frequency difference is about 300MHz, which is relatively higher than the reported sensor. Further experimental research on the sensor will be carried out, and fine-grained detection, such as water content in transformer oil will be considered.

I. Introduction

Metamaterial is a kind of artificial material composed of various elements in repeated forms, whose physical properties are determined by a specific structure rather than the composition of the material itself. By changing the size, geometry and arrangement of the component units can produce extraordinary physical properties that natural materials do not have. For example, it has negative permeability, negative permittivity, negative refractive index, inverse Cherenkov effect, and inverse Doppler effect. The concept of metamaterial can be traced back to 1968 when the Soviet scientist Veselago theoretically proved the possibility of metamaterial [1]. Due to the limitations of experimental conditions at that time, metamaterials were not formally realized in the early 21st century. Over the next two decades, researchers conducted many different studies around metamaterial. The emergence of metamaterial has brought new solutions to the optimization design of devices in different fields, such as antennas [2], absorbers [3], polarization conversion [4], cloaks [5], and sensors [6].