Research On Adaptive Reclosure And Adaptive Current Protection Technologies

The adaptive reclosure method can identify the fault property,and also avoid the damage caused by reclosing on the permanent fault,which ensures the safety of the entire power system stability.As to the single-circuit high voltage transmission lines,the current adaptive reclosure methods present have the disadvantages of long time judgment,low differentiation,which rely on the fault phase terminal voltage of low measurement precision.As to the parallel high voltage transmission lines,since that the fault types are so many and the fault characteristics are so complicated,the complete adaptive reclosure methods applicable to all the possible fault types have not been proposed.Meanwhile,as the rise of the permeability for DGs(distributed generations)in the distribution network,the efficient adaptive protection technology has got a lot of attentions.And because of the non-linear characteristic of the DG control method,the simulation velocity of distribution network with DGs is limited.Aiming at the shortage of the above problems,this paper makes the following research which includes:1.This paper analyzes the fault characteristics of the fault phase in the single-circuit and parallel transmission lines under different fault property,respectively.Considering all the possible fault types,this paper analyzes the fault characteristics of the fault phase voltage and the shunt reactor current in single-phase and three-phase adaptive reclosure.And this paper also analyzes the zero input and zero state response of the fault phase voltage of different fault properties under the ground faults and cross-line faults.2.Considering the possible fault types and reclosure modes,this paper proposes the single-phase adaptive reclosure and three-phase adaptive reclosure.Based on the reference model for the recovery voltage equivalent model of transient faults,the single-phase adaptive reclosure methoduses the shunt reactor current to identify the fault property;the results show that the method can accurately identify the fault property and the fault arc time.While the three-phase adaptive reclosure method utilizes the differential mode currents of the shunt reactor to identify the permanent fault.A lot of simulation results show that the single-circuit adaptive reclosure method can effectively identify the fault property.3.This paper divides all the fault types in parallel transmission lines into ground faults,cross-line faults with different phases and cross-line faults with same phases or interphase faults.And the fault phase voltage characteristics of different fault property are analyzed,which are verified by the EMTP simulations.Based on the theory analyzed above,the adaptive reclosure applicable to all the possible fault types of parallel lines is proposed,and also the method to calculate the setting value is presented in detail.The integration of fault-phase's recovery voltage is used for identifying permanent grounded faults;the integration of the difference of the fault-phase's recovery voltage is used for identifying permanent cross-line ungrounded faults with different phases.The simulation results verify the effectiveness of the method.4.This paper applies the adaptive reclosure scheme of parallel lines with shunt reactors into actual protection devices,and proposes reclosure sequential scheme,preventing reclosing on the permanent fault and reducing the reclosing time of transient faults.Combined with the actual dynamic model test,this paper gives a systematic analysis on adaptive reclosure behavior of the metallic faults,faults with transition resistance and evolving faults,which verifies the effectiveness of the scheme.5.As to the problems of adaptive protection,this paper applies the random robust optimization method to estimate the Thevenin equivalent parameters behind the DGs,realizing the adaptive setting of the current instantaneous fault protection,which can adapt to the changes of system operation modes.And this paper also proposes a method combining the dynamic phasor method with the SPRIM model reduction,which shortens the simulation time.