The Research On On-load Automatic Capacity Regulating Distribution Transformer

Energy conservation of power system is an important part to build China into a moderately prosperous society in an all-round way. Particularly, the rural grids have large qualities and large areas, Energy conservation is both bearing on the quality of electricity for thousands of households, but also a principal factors to directly affect the power companies economic benefits. As is known to all, transformer loss accounts for the majority of the distribution grids loss, and the larger capacity of the transformer, the more no-load loss and load loss.In our rural power grids, power require fluctuating with season changing have characteristics of load decentralization, strong seasonality, lower average loading rate, and so on. In busy farming season, transformer frequently run under overload and in off-season, some transformers load rate is lower, another transformers almost have no-load, all of these lead to many transformers run "oversized power", which relatively increase transformer no-load loss and result in a large number of unnecessary waste of power resources. And "mother transformer"will significantly increase investment.At present, unload capacity regulating distribution transformer are used in most areas, because of many power workers not mastering the correct ways, capacity regulating function of distribution transformer has not been fully utilized. Sometimes the load increases to high capacity, but transformer capacity do not run under high capacity, which frenquently lead to transformer burning accidents. Unload capacity regulating distribution transformer change capcity under unoperation, which affects the reliability of power supply and need high operation and management retuirements, all of these limit widely using in the large range.Therefore, on-load capacity regulating transformer has been gotten all-pervading application step by step in distribution networks in recent years. But its capcity regulating switches are made up of mechanical and dynamoelectric components, whose speed of capacity regulating is low, and arc is produced easily, as well as its fault ratio is high all long. The function of on-load capacity regulating is then affected badly. The development of power electronic technology makes it possible to carry out tap shift by using microprocessor to control directly power electronic switch. Mechanical capacity regulating technology is replaced by quick and arcless power electronic capacity regulating technology is the development trend in this field.On the basis of analysis of energy conservation principle of capacity regulating distribution transformer, the economic benefit is calculated in aera whose power consumption singificantly different from peak to valley and region whose peak and valley loads freguently rotate and rural aeras whose power consumption is seasonal concentration according to the measured dynamic day and month load data, and it was put forward that a new technology scheme of arcless on-load automatic capacity regulating regarded power electronic switch as the key part in this paper. The feasibility of arcless on-load capacity regulating is demonstrated and its switch layouts are also given. Based on that, the key technologies of arcless on-load capacity regulating are analyzed and the design of arcless on-load capacity regulating switch is given too.Finally, The simulation model of the scheme was established using PSCAD/EMTDC, which is the professional tool for power system simulation software. Simulation study and analysis for the shift and transition of power electronic switches was carried through, and the feasibility of this scheme was validated primarily.