Fault Unbalanced Current And Detecting System Of Dry-type Air-core Reactor

Dry-type air-core reactor has been widely applied in the modern electrical power system,for which has technological superiorities such as low price,simple structure,light weight,linear reactance value,little wastage and convenient protection.It has the functions of power compensation,ultra-high-voltage transmission filter,neutral ground,surge current and short circuit suppression.It is an important facility to guarantee the security of electrical power system and the stability during operation.However,failure often occurs to the reactor,such as short circuit,breakage,turn-to-turn electro-discharge,which influences the stable operation seriously.So it is necessary to check the faults of rector.At present,there are several checking methods such as impedance checking,temperature checking,and zero sequence power,which are not enough reliable and sensitive.Thus,it has high practical value to come up with a more sensitive checking method to guarantee the function of reactor and the stability of electrical power system.At first,as to the weakness of checking insensitivity in checking faults during the operation of reactor,this essay offers a checking method to solve the unbalanced current due to the breakdown of reactor.This method makes use of the symmetry in Dry-type air-core reactor structure,by measuring the unbalanced current after the convergence of the dry-type air-core reactor fault with bus-bar to check if it is breakdown.Secondly,the physical model of the single-wrap four-winding dry-type air reactor is established.Based on this,the mathematical model of the bus-bar current is obtained by analytic method.The physical model and the corresponding mathematical analysis model include five types: fault-free,single-turn short circuit,two-turn inter-turn short circuit,multi-winding inter-turn short circuit and broken wire.The above five models are used to calculate the bus-bar current of the dry-type air reactor,and the matlab simulation rule is used to simulate the distribution law and the phase change law of the unbalanced current of the bus-bar before and after the fault.The results show that the unbalanced current method is more effective than the zero sequence power direction protection method,and it is found that the fault between the two windings is the most difficult to detect.Finally,this paper studies the two-winding inter-turn short-circuit model,which is the most difficult to detect from steady-state and transient,and analyzes the steady-state data and transient waveform of the bus-bar current,and obtains the unbalanced current and short-circuit position The feasibility of the fault imbalance current method is further verified.And according to the dry hollow fault unbalanced current method to build a wireless detection system.This study is of great significance for both the failure detection of the air reactor and the reactor’s manufacture.