Research On Strain Characteristics Of 110kV Oil-Immersion Transformer Based On BOTDA

Transformer is an important part of power system,winding failure is the main type of transformer failure,winding deformation is an important hidden danger of failure.Therefore,it is important to obtain timely and accurate strain information of transformer windings and the operating status of transformers.At present,the winding status is mostly checked by regular shutdown and offline inspection,which cannot meet the need of online real-time information acquisition.Distributed fiber optic sensing technology has developed rapidly in recent years,which can realize distributed sensing of strain on monitoring objects and has the advantages of anti-electromagnetic interference and high sensitivity.The study of distributed detection of transformer strain based on Brillouin Optical Time Domain Analysis(BOTDA)has both theoretical basis and application value.In this paper,the feasibility of using Brillouin Optical Time Domain Analysis for distributed strain detection of transformer windings was investigated as follows.Firstly,the fitting method of Brillouin spectrum was studied,and a double-peak fitting algorithm was proposed to achieve sub-resolution detection,which effectively improved the event resolution and spatial resolution of the BOTDA system,enabling the system to detect small deformations more sensitively and obtain deformation information more accurately.It also provided a basis for the application of distributed fiber optic sensing technology in transformer windings with relatively small dimensions.Subsequently,the actual winding deformation as a function of fiber optic deformation was studied to determine the strain transfer rate.Through the analysis and comparison of different arrangements and positions of the sensing fiber composite transformer winding model,the best arrangement was deter mined to be wrapping the fiber on the outside of the winding,and the strain transfer rate of the fiber was studied based on this arrangement.The feasibility of applying the BOTDA system to transformer winding strain detection was verified,and the accura cy of the detection results was improved.Finally,a prototype of sensing fiber composite 31.5MVA/110 k V oil-immersed transformer was developed,focusing on the arrangement and protection method of the fiber inside the transformer,the location and reliability of the flange based on the above work.After successfully passing the factory test,the prototype was subjected to short circuit shock test to verify the strain sensing performance of the fiber and the accuracy,stability and reliability of the BOTDA system during the short circuit.The strain detection with a spatial resolution of 20 cm was achieved inside the transformer on account of BOTDA,which verified the engineering feasibility of applying BOTDA to transformer winding deformation detection and pr ovided a new idea for online monitoring of transformer winding deformation.