Research on transformer self-adaptive protection principle based on equivalent equation

This paper puts forward a new transformer self-adaptive protection principle. The principle is based on equivalent equation. The principle mainly includes three components: parameter estimation unit, high speed protection unit and fault component protection unit. When there is serious fault in transformer, the high speed protection unit can act quickly. When there is weak fault in transformer, the high speed protection unit may refuse to act. Then the protection threshold of the fault component protection unit will be set online. When the action is greater than the threshold, the fault component protection unit will act. If the both protection unit don not act, there would be external fault for transformer. The external fault can impact to the transformer. The windings parameter may be changed. Then the parameter estimation unit will work. The parameter estimation unit can on-line identify the windings parameter by using least square algorithm. The winding parameters are calculated to update the original parameters. Test result indicates that the principle is immune from magnetic inrush. For serious faults in transformer, the action speed of protection is high. For weak faults in transformer, the sensitivity of protection is high. Transformer winding parameters and the threshold value of protect can online be obtain. The principle is self-adaptive protection.