Study on Influence of Trees around 10 kV Distribution Line

Considering the complexity of the geographical surroundings and the height of 10 kV distribution line, the impact of trees on the lightning performance can not be ignored. A model of lightning position judgment and overvoltage calculation based on the concept of striking distance is built. With the theory of orthogonal test, the main factors of trees' influence on lightning performance are figured out. The results indicate that the location of trees is the main factor. In practical engineering, suitable management of vegetation can improve the lightning performance and reduce the lightning failure of 10 kV distribution line.

Dynamic thermal rating assessment of oil-immersed power transformers for multiple operating conditions

In this article,the dynamic thermal rating assessment method of oil-immersed power transformer with multiple operating conditions is proposed,considering the constraints of hot spot temperature(HST),top oil temperature,losses of life and the maximum allowable current of on-load tap changer(OLTC)or bushing,which can determine the dynamic load curves under different operating conditions and give the most sensitive constraints to limit the dynamic load capacity.To improve the accuracy of HST estimation,the temperature estimation model is also improved and the thermal parameters are optimised using the HST measured by optical fibre.Finally,several application examples are studied for transformers in different scenarios.The results show that the normal cyclic dynamic transformer rating(DTR)is mainly limited by the losses of life when the ambient temperature is high,and the average load factor can be increased to 0.82 with a maximum load capacity of 1.23.The main limiting factor of short-term DTR is the OLTC or bushing current constraint,and the average load factor can be increased to 1.00.The maximum load capacity of the transformer under both operating conditions is 23%and 50%higher than its rated load capacity,indicating that the transformer still has a large load potential available.

Charge Transport in Oil Impregnated Paper Insulation Under Temperature Gradient Using Transient Upstream FEM

Charge transport in oil impregnated paper impacts the insulation performance of a transformer.This paper proposes a simulation method for the charge transport in oil impregnated paper insulation.The transient upstream finite element method(FEM)is applied to the transport equations of bipolar charges for establishing a numerical simulation model of charge transport in oil impregnated paper insulation.The method is validated by experimental results.The charge transport and electric field distribution in single-layer oil impregnated paper insulation under different temperature gradients is simulated.The trends of the simulation results are seen to agree with the corresponding experimental results.This paper conducts exploratory research into the simulation of charge transportation phenomenon in oil impregnated paper,and is of importance to the design of oil impregnated paper insulation.

民具的研究与展示

受西欧学术的强烈影响,近代的日本逐步认识到作为普通生活用具的民具实为重要的文化遗产。这一认识与日本的人文科学以及艺术观念的形成有着密切的关系。基于前述认识,在19世纪民具成为探寻庶民生活文化的重要民俗学研究资料。此外,在发现民具审美价值的同时,还形成了"民具"与"艺术"相互结合的"民艺"概念。民具,无论是作为民俗研究资料,还是美术品,均具有日本或日本人的精神价值。究其历史,无论是民具的材料还是制作技术,在很大程度上与异域文化有着不可分割的关系。从这个意义上来说,通过民具还可以研究国际交流史。在全球化、国际化不断发展的今天,从国际视角研究民具所内涵的世界文化融合亦是重要的研究方向。