Study On The Influence Of Transient Characteristics Of TPY Current Transformer On Differential Protection

Current transformer is an important equipment connecting primary and secondary systems.Protective current transformer is mainly used to provide action basis for relay protection when abnormal operation or equipment failure occurs.At present,standard CT,transformer calibrator,elevator,current load box,voltage regulator and other test equipment are often used to evaluate the characteristics of protective level current transformer.The operation is tedious,and the steady-state characteristic index of current transformer is usually only obtained,and the transient characteristic analysis is lacking.In order to evaluate the performance of current transformer conveniently,improve the measurement accuracy of protective level current transformer,and improve the technical ability of relay protection device,it is necessary to establish simulation model based on physical objects.This paper takes the TPY class(open air gap transient protection level)current transformer widely used in power system as an example,establishes the mathematical model of the steady state and transient state of the protective class current transformer,and analyses the transformer characteristics of the TPY class current transformer under the high remanence or DC bias environment,so as to study the influence of the TPY class current transformer on the relay protection.At the same time,the error calculation method of TPY current transformer is given,and reasonable and feasible error compensation and transient characteristic improvement measures are put forward.Finally,the accuracy of the mathematical model is verified by real object.The established mathematical model is transplanted to PSCAD digital simulation platform to realize electromagnetic transient simulation under three conditions: changing input current without fault,changing load impedance characteristics under fault and multiple fault reclosure.The influence of transient characteristics of TPY current transformer on line differential protection is analyzed in the form of digital simulation,and protection is carried out on the basis of this.Performance analysis and capability improvement.In the extension project of Luping 500 kV substation,TPY winding is used for newly added line protection,bus protection and circuit breaker protection,while 5P30 current transformer is used in the previous project.In order to prevent malfunction caused by differential current caused by inconsistent CT characteristics of bus protection,TPY and 5P30 current transformers are connected to differential current after bus differential protection at the same time.The characteristics are analyzed,and guidance suggestions are provided for operators to ensure the safe and stable operation of the system.Finally,according to the aforementioned digital simulation model,the characteristic parameters involved in the characteristic evaluation are introduced,and the corresponding experimental and data analysis methods are designed to obtain the corresponding parameters.Through the combination of physical test and simulation data,the steady-state performance and transient performance of current transformer are analyzed to quantify the influence of its transmission performance on relay protection,promote the progress of protection technology,optimize the configuration scheme of current transformer in smart substation,improve the design of smart substation,and reduce the construction cost of smart substation.