Optimized Operation Of Multi-type Transformer And Its Protection

The power transformer is a key equipment to the power grid and its economic andreliable operation plays an important role in the efficiency and stability of the entire powersystem. Although transformers are mainly used to transmit power and change the voltage,there are still many types under different workplaces. Transformer itself consumes activepower loss at work and the loss is related to load factor, so the most efficiency way can befound and we call it the transformer economic operation. But nowadays the transformeroperation practice doesn’t depend on the economic operation because of the lack ofadequate awareness of the principle and the low accuracy for the transformer parameter.The2nd harmonic restraint criterion is used to distinguish transformer inrush and internalfaults in normal alternating current system. But the effect is not so good when the samemethod is put into use on converter transformer. The harmonic characteristic of the inrushcan be weakened and the current has lots of harmonic part when internal faults happen dueto the AC/DC field. A variety of problems may occur during the operation of transformerand the fault of multipoint of the iron-core is relatively common. The traditional way fordetecting this fault may produce abnormal result when the transformer is working undercomplex power grid circumstances. Based on the problems mentioned above fortransformer, some research has been done to improve the economic and stability fortransformer, and the details are as below:The formula for calculating the power loss of transformer is established. Thecomprehensive power loss is used to determine the transformer economic operation. Theway to determine transformer economic load coefficient is presented and economicoperation area is divided based on the coefficient. It has three zones, that is the besteconomic operation zone, the economic operation zone, the worst operation zone. Theprocess to determine the economic operation for two-winding transformer under paralleland split operation is analyzed. The real parameter for transformer has a little differencefrom that on the nameplate and data fitting based on the online real time information isused to revise the parameter. The difference between before and after revising is presented.The fundamental converter transformer model is established based on the actualparameter from southern power grid. The reason of the mal-operation of the differentialprotection caused by transformer inrush is analyzed. A method that can distinguish the inrush and the internal fault on converter transformer is presented based on thecharacteristic of converter transformer and simulation proves its correctness.The limitation of traditional method on multipoint grounding of the iron-core isanalyzed and the interference under complex power grid is the primary cause. Accordingto that, increasing the number of the relative detection items and using bayes network isproposed to enhance the correctness for detecting multipoint grounding fault.