Relay Coordination Theory Study And System Development Of Transformer Protection

The correct operation rate of transformer protection is low for a long time in China, miscoordination is one of the main reasons. Now, there is no setting calculation software adapted to transformer protection. Therefore, researching on such software has great academic value and economic benefits. This thesis devote to research on theoretic problems and key technical problems, such as setting principles of transformer backup protection, principles and methods in fault calculation and operation mode combination, realization of setting system and its versatility.This thesis studies the principles and methods of setting calculation of transformer grounding backup protection and phase backup protection, analyses the particular instance that the zero-sequence circle current exists in transformer zero-sequence over-current protection, provides the definitely definition and explain of the direction of the zero-sequence circle current. Then, this thesis researches on deadlock between transformer zero-sequence over-current relays and puts forward the valid methods to break the deadlock. The problems exist in configuration of transformer grounding backup protection is studied, and the method to improve the configuration is put forward.The mathematical model of transformer in fault calculation is researched. In order to gain immediate and definite results, means that taking the ratio as the complex number when the node admittance matrix is forming is adopted. A method of operation mode constraints is proposed aimed to dealing the relevancy of operation mode changes of component and the changes of transformer neutral point, which could effectively combine auto-calculation and the experience of practical operation.In addition, a transformer protection setting calculation system is structured based on optional principles and self-redefinition of the protective relay module by summing up the setting principles of transformer backup protection and setting items of the protection devices. Then, the framework of the system is introduced and self-redefinition of setting principles and its extensibility is discussed. Finally, the thesis illuminates the procedure of transformer protection setting calculation by a example.