Dissolved hydrogen detection in power transformer based on etched fiber Bragg grating

Abstract

Due to aging and degrading of insulation oil in power transformers, dissolved hydrogen, as a typical fault gas, would produce accompanied by discharges or overheating. Palladium (Pd) film deposited on the surface of chemically etched fiber Bragg grating (FBG) as sensing element by magnetron sputtering process is proposed in this paper. Volume expands when Pd film with 560nm thickness absorbs hydrogen molecules and wavelength shift caused by the strain could be measured. In this principle, hydrogen of low concentration can be obtained through wavelength shift of FBG. Different aspects have been taken into consideration including membrane thickness, polyimide coating and cladding diameter to obtain satisfactory sensitivity. Experimental results in the lab showed that this developed hydrogen could detect 30 μL/L at 1 pm approximately, which proved to be a prospective sensor as a on-line method to be utilized in power transformers.

Overview and Partial Discharge Analysis of Power Transformers: A Literature Review

“…Generally, hydrogen gas detection is preferred over other detections due to better accuracy. During overheating and discharges, if the hydrogen gas level rises above the warning value, the internal insulations need to be diagnosed [109]. Several types of research have employed FBG sensors inside the tank with the normal operating temperature (60°C to 90°C) for detecting the hydrogen gas concentration.…”

Survey of different sensors employed for the power transformer monitoring

“…Therefore, sensors that detect these gases are useful for transformer monitoring. Although there are devices that detect all these gases, H 2 is the most important one to be measured and is sufficient in many cases [49]. It must be noted that some gas sensors can be directly put in the oil while some works only in the gas phase.…”

Tilted Fiber Bragg Grating Sensor Using Chemical Plating of a Palladium Membrane for the Detection of Hydrogen Leakage

“…Moreover, due to the flammable and explosive nature of hydrogen, the use of optical fiber detection can be much safer. Currently, various types of hydrogen sensors based on optical fibers have been proposed, including fiber Bragg gratings (FBG) [3,4], specially treated fibers (side polishing fiber [5] and singlemode-multimode-singlemode fiber [6]), and micro-cantilever beam fiber Bragg grating [7], as well as TFBG sensors using the SPR effect [8]. Most of the sensors use a palladium (Pd) metal membrane as the hydrogen sensing element, due to its strong ability to absorb hydrogen [7].…”

“…For the preparation of the thin layer of metal coating, the magnetron sputtering method is commonly used [3,4,8,11,12,13,14]. A uniform layer of metal can be formed on the surface of the short fiber by rotating it during the sputtering.…”