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Compared with the existing winding deformation detection technologies, such as the frequency response method and short-circuit reactance, the vibration analysis method can effectively detect the loose state of windings. This paper has carried out mechanism analysis and experimental study on the change of winding modal characteristics caused by two kinds of defects, analyzed the transmission characteristics of three-phase double winding transformer winding vibration in the transformer oil and structure, studied the influence of pad falling off, plastic deformation and other defects on the mechanical state of the winding, calculated the winding short-circuit vibration signals corresponding to different mechanical states, and extracted the vibration characteristics that can effectively reflect the mechanical state of the winding. The research conclusion can provide an important basis for transformer fault diagnosis.

After transformers suffer from short-circuit impact, their mechanical performance decreases significantly. This article establishes a two-wire vibration model to represent the coupling between forces and mechanics and analyzes the transient vibration signals of a 400 V transformer during 22 short-circuits impact. To illustrate the cumulative effect of short-circuits, the vibration entropy, and energy ratio of the main vibration frequency and half frequency are adopted. The results show that transient vibration signals of transformer in short-circuits contain half frequency components, such as 25 Hz and 75, etc., and with the increase of the number of short-circuits, plastic deformation exists in insulation material, which leads to the loss of winding clamping pressure, the reduction of natural frequency, and the upsurge of parametric resonance. With the increase of short circuits, the vibration entropy and half-frequency energy ratio increase, and the main frequency energy ratio decreases. After winding completely lose the axial stability, the vibration entropy and half frequency ratio decrease, and the main frequency ratio increases. The conclusion is of great significance to the analysis of the cumulative effect of short circuits on power transformers.

Capacitor voltage transformer is an important power equipment in substation, which is with great significance to the safe operation of substation. This paper summarizes and analyzes the common problems in the process of technical supervision of capacitor voltage transformer, and the oil level window of electromagnetic unit is improved to avoid the disadvantage of oil level inspection inconvenient of capacitor voltage transformer. Inclined angle between oil level window and electromagnetic unit is 60°. The oil level window is large, and the material with aging resistance and high transparency is selected. The problems existing in the oil level inspection of CVT electromagnetic unit are effectively solved and the safe and stable operation ability of equipment is enhanced by improving oil level window.

Electromagnetic voltage transformers are widely used in 35kV and below substations. The safety of the equipment directly affects the stable operation of the system. Based on an example of a 10kV voltage transformer burned out, this paper deeply analyzes the fault causes, and puts forward preventive measures to ensure the safe and reliable operation of the power system and reduce the occurrence of over-voltage accidents.

This paper Initial on the solar parabolic trough collectors…Semi-insulated voltage transformers are widely used in power distribution network. The safety of their own equipment directly affects the safe and stable operation of power system. In this paper, the fault diagnosis and analysis process of a semi-insulated voltage transformer is described in detail. In this paper, the fault course and the condition of the fault equipment are introduced at first, and then the cause of the fault is clarified through the electrical test and disassembly analysis combined with the action protection condition. Finally, the preventive measures for the daily operation and maintenance of the equipment are put forward.

Dry-type current transformer is widely used in substation, equipment safety directly affects the stable operation of power grid. This paper analyzes a burning accident of a 10kV dry-type current transformer, the fault diagnosis and analysis process are elaborated in detail. Through the test and disassembly inspection of the fault current transformer, the fault causes are analyzed in depth, and the preventive measures are proposed.

With the advantages of small volume, light weight and high accuracy, the epoxy pouring current transformer is widely used in power systems of 35kV and below. The safety of its own equipment directly affects th1e safe and stable operation of power systems. This paper details an insulation breakdown fault of the epoxy pouring current transformer. The cause of the fault is clear and definite. In the manufacturing process of the current transformer, in order to make the primary copper winding located in the middle of the secondary winding, an insulating support block is installed between the primary winding and secondary winding in a fixed position. Then, in the pouring process, the insulating support block has not fully fused into an organic whole with the surrounding insulating medium, leaving a gap around the insulating support block. The insulating performance of the current transformer is reduced, which leads to the insulation breakdown after running for a long time. Based on this fault, the research on manufacturing technology of pouring current transformer is carried out, and the fault prevention measures are put forward.

In this paper, the influence of mutual opposition error between the standard secondary line at the end of the test bench and the tested secondary line in the error test of voltage transformer is analyzed, and the corresponding solutions are proposed for the wrong wiring.

In recent years, primary and secondary integration of distribution switchgear has been widely used in the distribution network. In the future, primary and secondary integration will become the mainstream development trend of power distribution switchgear, especially in 2021, the State Grid Corporation of China will issue a new type of primary and secondary integration standardization. The typical design plan of power distribution switchgear have added two configuration methods: electronic transformer and digital transformer. So the traditional independent test method of power distribution automation terminal or power distribution switchgear are no longer applicable to the current new-type primary and secondary fusion standardized power distribution switchgear. At the same time, there is no standard basis for direct reference. This article mainly analyzes the key test items for performance verification of primary and secondary fusion power distribution switchgear, and propose corresponding test detection methods.

Capacitance parameter extraction of converter system is crucial to analyze the voltage distribution of valve tower under different overvoltages (such as lightening, partial discharge, etc) in HVDC converter station. According to the actual dimension of valves, the Method of Moments(MOM) based on the point matching method is applied to extract the capacitances, including the self-capacitances and the mutual capacitances between the valve modules in the valve hall. Firstly the surfaces of conductors are meshed into small area elements, and the surface charge density of each element is considered as a constant. Then the potential coefficient matrix corresponding to elements can be achieved by MOM. The capacitance matrix can be acquired through matrix transformation. The proposed method is flexible and fast compared to the Finite Element Method (FEM) and Boundary Element Method (BEM), since it is unnecessary to solve the conductor surface charge and the electric field. The calculation results agree very well with the capacitance testing experiments.