Study On Technology Of Inrush Current Restraining For 2×1140MVA Transformer In Ninghai Power Plant

In the power system for charging no-load transformer is a common mode of operation,when the charge switching instant in transformer power supply side will often produce high impact current,the amplitude is equal to rated value several times to ten times,the impact current is called inrush current.Due to t he presence of inrush current,often makes the transformer because differential protection misoperation and charging failure and the transformer energisation can lead to adjacent units of the active power and reactive power fluctuation and threat to the unit operation safety.Ninghai power plant in the two phase of the main transformer no-load charging occurs when the differential protection of the wrong action,the phenomenon of power fluctuations adjacent to the unit.More serious is that the larger transformer inrush current can also cause damage to the transformer firmware,shorten the life of the transformer.The recent group of a power plant on power transmission transformer,because of the impact caused by excessive current transformer damage,Ninghai Power Plant Phase II 5 main transformer also because of electric shock caused oil chromatographic analysis of abnormal.Therefore,how to reduce the harm caused by the inrush current of the transformer has become an urgent problem to be solved.Firstly,this paper theoretically explains the reasons,characteristics and hazards of the transformer inrush current,and deeply analyzes the phenomenon of the protection malfunction caused by the inrush current in Ninghai power plant.Then through analysis of transformer remanence,magnetic bias,steady-state flux transformer and power supply switching on-off voltage phase angle between the relationship and found that the transformer remanence and bias mutual g principle to suppress the inrush current technology.Finally,the surge suppression technology is applied in the 2 stage of the two stage of Ninghai power plant,and the effectiveness of the technology is verified by the actual live impact test of the transformer.In the remanent magnetization and magnetic bi as mutual g principle of surge suppression technology,Ninghai Power Plant Phase II of the main transformer no-load closing excitation inrush current is restricted to less than rated current,solving the problem caused by the magnetizing inrush current in Ninghai Power Plant.