The temperature distribution and deformation of the transformer windings cannot be measured in a distributed manner by the traditional method and failure location cannot be performed. To solve these problems, we present a transformer winding temperature and strain based on a distributed optical fibre sensing detection method. The design of the optical fibre winding composite model is developed and simulated winding temperature rise test and local deformation test distinguish between measuring the winding temperature and the strain curve. The test results show that the distributed optical fibre can transmit wire strain efficiently. Optical fibres, in the process of winding, have a certain pre-stress. Using the Brillouin–Raman joint measuring method, one can effectively extract the optical fibre temperature and strain information and measure the length of the winding direction of the temperature and strain distribution curve to a temperature measurement precision of ±2 °C and strain detection accuracy of ±50 με. The system can carry out local hot spot and deformation localisation, providing new ideas for the transformer winding state monitoring technology.

Winding overheating is a common fault in a transformer. To detect the temperature, the most widely used method is a point-type measurement, but traditional measurement methods cannot obtain the whole temperature distribution in a transformer. Taking this into consideration, a new method with which to measure the temperature of transformer windings was proposed. Based on Raman scattering, a new fibre-optic composite winding model was developed. The feasibility of the model was verified by electrical as well as temperature, field simulation and power frequency resistance testing. To assess the practicality and accuracy of the new model, a distributed optical fibre temperature measurement platform was built, and a series of experiments were designed. According to the data collected, the temperature measurement error based on the method could be limited to 1 °C while the positioning accuracy error was within 1 m, which meant that the new approach can satisfy the requirements of transformer winding temperature measurement and locate hot spots in the winding.

Transformer internal thermal monitoring exists huge blind areas, and it is difficult for traditional methods to get fully distributed temperature in real time. In this contribution, the distributed optical fibre sensor was creatively applied inside an operating 35 kV oil-immersed transformer which is also qualified for actual power grid operation through the ex-factory tests. Furthermore, the full-region temperature along the windings and iron limbs were firstly monitored in a spatiotemporally continuous manner and the hotspots were also closely traced, fluctuating at 90% of the highvoltage winding height (80% for low-voltage winding) during the whole process of the heat-run test. Corresponding Finite Element Method (FEM) for thermo-fluid field calculation was then utilized for deeper analysis. On the former basis, the actual detected temperature distributions (both spatial and temporal) were compared with the International Electrotechnical Commission traditional model and some modifications were suggested based on the real time measured data. This novel online monitoring application and the detailed internal thermal information may provide a solid reference for the delicate management of power transformers, which also offers a new horizon for the online monitoring in electrical apparatus industry.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

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