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Highlights • Temperature field models of a 110 kV buried submarine cable are established. • Temperature distributions of cable with global insulation degradation are presented. • Temperature distributions of cable with local insulation degradation are presented. • Submarine cable insulation is evaluated based on optical fiber's temperature rise. • Influences of related factors on optical fiber's temperature rise are investigated. Abstract To effectively monitor the insulation state of the optic-electric composite submarine cable, the finite element numerical model for the temperature field of a 110 kV YJQ41 × 300 mm2 buried submarine cable was constructed in COMSOL, based on its thermoelectric coupling module. The results were validated by the improved IEC 60287 standard method and the optimal size of the physical dimensions of the model was obtained. On the basis of study of the effects of ambient temperature, buried depth, soil thermal conductivity, heat transfer coefficient of seawater and ampacity on the optical fiber's temperature in normal insulation state, the optical fiber's temperature rise in different levels of global insulation degradation was investigated. The results reveal that, when the cable insulation is globally degraded, the relative temperature rise of optical fiber is proportional to dielectric loss factor. Comparatively, the ambient temperature has little influence on it. A formula for estimation of dielectric loss factor based on relative temperature rise and ampacity of cable is presented. According to the formula, a method for evaluation of the submarine cable insulation degradation based on relative temperature rise of optical fiber is proposed. By tuning the structure and electrical parameters of a part of cylinder area in the insulation layer of submarine cable, the cable with different local insulation states was modeled by the combination of ATP and COMSOL. The effects of ambient temperature, volume resistivity of insulation degradation area, ampacity of cable and the size of the degraded area on the maximum relative temperature rise of optical fiber were investigated. When the cable insulation is locally degraded, the maximum relative temperature rise of optical fiber is inversely proportional to the volume resistivity of the insulation degradation area. It is proportional to the central angle of the insulation degradation area and increases with the square of length of the insulation degradation area. If the threshold of the relative temperature rise of optical fiber is set to 1 °C, the range of optical fiber's temperature rise caused by local insulation degradation decreases exponentially with volume resistivity of the insulation degradation area and always has a spatial scale of meters for the cases with severe insulation degradation, which is similar to the spatial resolution of optical fiber distributed temperature sensing system based on BOTDR (Brillouin Optical Time Domain Reflectometer). This work can be taken as a reference to evaluation and location of insulation degradation of submarine cable based on temperature rise of optical fiber. [ABSTRACT FROM AUTHOR]

It is difficult to accurately measure internal temperature of power capacitor. To accurately measure internal and external temperatures of an operating capacitor, a capacitor temperature measurement system based on fiber Bragg grating (FBG) temperature sensors is developed. First, technical parameters of the sensors and the optical sensing interrogator are determined according to the practical situations. Second, the sensors are calibrated using a highly accurate thermostatic bath, and their reproducibility is checked. Third, in combination with ENLIGHT software, the temperature measurement system based on FBG sensors is set up. Finally, three BAM6.56-556-1W high-voltage film capacitors are manufactured, and the FBG sensors are put into a high-voltage film capacitor and placed on its shell, the temperature distribution of the capacitor in the thermal stability test is measured. The corresponding temperature field model of the capacitor under the same conditions is created and solved in Fluent. The simulation results are consistent with the measured results, which validates the temperature measurement system. This paper fixes the problem of internal temperature measurement for high-voltage film capacitor which can be taken as a reference to online monitoring of power capacitor temperature. [ABSTRACT FROM AUTHOR]

Temperature field simulation for self-healing power capacitor makes sense to the capacitor optimization and improvement of capacitor’s rated voltage and capacity. On the basis of reasonable simplifications and assumptions for capacitor structure, a 3-D temperature field numerical simulation model for a self-healing power capacitor is formulated in Fluent 15.0. The ambient temperature is set to 55 °C, and the applied voltage is ac 400 V. The temperature distributions of the shell and core of the self-healing capacitor are obtained. The results reveal that the temperature of the core is 2 °C–3 °C higher than that of the shell. The highest temperature of the shell locates on the large side surface, and the temperature of the large side surface is higher than that of the small side surface. To validate the above simulation, a self-healing capacitor is manufactured and thermal resistance sensors are used to measure the temperature in the thermal stability test. The simulation is validated by the experiment. Finally, the influences of the ambient temperature and applied voltage on the temperature rise are investigated. This paper can be taken a reference to the self-healing capacitor operation, maintenance, and even the optimization of its internal structure and material. [ABSTRACT FROM PUBLISHER]