An acoustic sensor for partial discharge detection based on a polymer diaphragm and a single-mode-multimode-single-mode optical fiber composite structure is proposed. A multi-mode optical fiber with a length of 5 cm is implanted between single-mode optical fibers as an acoustic sensitive unit. When light enters the multi-mode optical fiber from the single-mode optical fiber,it will excite higher-order modes to form interference,so as to achieve acoustic sensing. The optical fiber is embedded in a polymer diaphragm to improve its sensitivity.Experimental results show that the acoustic sensing sensitivity of the sensor in air can reach -30.8 dBm(0 dBm is defined as 1 V/μBar ). Partial discharge acoustic sensing tests are conducted on the sensor in air and oil according,and the results the IEC 60270 standard,and the results prove the feasibility of the solution. Due to its advantages of simple structure,low cost and immunity to electromagnetic interference,the sensor is expected to be applied in areas such as partial discharge detection of power equipment.
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