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In the face of the global environmental problems of increasing energy consumption and increasing greenhouse gas emissions, China has taken the responsibility of emission reduction and formulated and promoted a series of policy measures to deal with climate change. Power industry is a key industry in greenhouse gas emissions, power grid enterprises as the core business of the power industry, will actively realize energy saving and emission reduction in the power industry and promote the development of low-carbon economy. Based on the characteristics of the power industry and the characteristics of the operation of the power grid enterprises, this paper identifies the greenhouse gas emission sources of the grid enterprises from three aspects: direct greenhouse gas emissions, indirect greenhouse gas emissions from electric power and other indirect greenhouse gas emissions. At the same time, the method of accounting for greenhouse gas emissions is put forward for each emission source.

Under harmonic condition, transformer loss is significantly higher than that of traditional calculation method. It is necessary to re analyze the resistance model of transformer winding in harmonic environment. In this article, the harmonic loss model of transformer winding considering skin effect and proximity effect is established, and the characteristics of the conductor resistance of transformer winding are obtained by electromagnetic field principle analysis; the conductor resistance of typical harmonic current is measured by experiment, and the effectiveness of the model in reflecting the winding loss under harmonic condition is verified, which makes the load loss of transformer The calculation is more accurate.

There is a growing demand for electricity recently. With the advances of technology, many impact and nonlinear loads are widely used in the distribution network and the increase of the number of single-phase power users will inevitably cause the power quality problems such as harmonics and three-phase unbalance. Therefore, the loss of the low-voltage distribution network is also increased rapidly, so it is of great significance to consider the loss of low-voltage distribution network under the disturbance of composite power quality. In this paper, firstly the calculation formula of additional losses caused by power transmission line and transformer in harmonic and three-phase unbalance is deduced, then the extra loss produced by the key equipment when two kinds of power quality problems exist at the same time is gotten. The accuracy of theoretical formula is verified in MATLAB/SIMULINK simulation platform. Secondly, the simulation data of the additional loss generated by the key equipment when the harmonics and the three-phase imbalance exist at the same time and the additional loss when they exist alone are comprehensively analyzed. The results show that the additional losses caused by the simultaneous existence of the two are less than those caused by the single existence of the two. The sum of the additional losses does not satisfy the simple superposition principle.

The leakage magnetic field of the transformer is related to the design, manufacture and operating performance of the transformer. The size and distribution of the leakage magnetic field determines the short circuit reactance of the transformer, the eddy current loss of the winding, the eddy current loss in the metal structure, and the electromagnetic force on the winding under normal and faulty operating conditions, and to a large extent determine temperature rise of the winding and transformer Other parts. Eddy current loss caused by Transformer winding leakage magnetic field accounted for a larger proportion of additional losses and will produce local transformer overheating, life shortened. The error of traditional empirical formula calculation method about the transformer winding eddy current loss is large, in order to accurately calculate the transformer winding eddy current loss. Based on the ANSYS finite element analysis method, we establish the finite element model of the dry-type transformer, analyze the distribution of the magnetic flux leakage of the transformer and obtain the eddy current loss distribution and loss value of the transformer. The comparison between the theoretical calculation and the simulation results of the eddy current loss shows that the calculation method of the finite element analysis method is more accurate.

Energy and environmental issues have become one of the major problems in the world today and due to its unique environmental advantages renewable energy thus become the best choice for all around the world. With increasingly more renewable energy such as wind farm or photovoltaic power plant connected to the grid, power quality issues begun to emerge which in turn resulted in great impact on our power grid. As there are a variety of power quality control methods, it is necessary to establish a feasible evaluation system to help us make decisions. This paper presents a comprehensive system that combines both subjective and objective methods by using grey relational analysis which reveals how close between ideal sample and target method. At the end of this paper, an example of selecting the reactive power compensation according to the field measured data is given.