Power Line Fault Diagnosis And Transformer State Assessment Based On Electrical Quantity Information

With the development of China’s economy,the structure of China’s power system is more complicated,the voltage level is getting higher and higher,and the connection between the power grids in different regions is closer.At the same time,affected by the system itself and external factors,The probability of failure of power grid and power equipment increases.The damage to the stable operation of power system caused by the untimely handling of faults is also increases.For the diagnosis after the grid fault,the traditional methods are mostly based on the switching information,that is,the action information of protection and circuit breaker.With the gradual improvement of the construction of smart grid,the application of integrated dispatching data platform in all aspects of power grid will be more mature.Based on this,not only can the switch information such as protection and circuit breaker be obtained,but also the multi-source fault information from SCADA and WAMS systems can be easily obtained.In this way,we can get rid of fault diagnosis relying only on switching variables,and make full and reasonable use of multi-source and heterogeneous fault information,which will also make the fault diagnosis results of power grid more accurate.At the same time,these multi-source information also provides information sources for more accurate state assessment of electrical equipment.In this context,the following work has been done in this paper:(1)This thesis introduces the research background of the subject and several common fault diagnosis methods for power grids at home and abroad.SCADA system,WAMS system,relay protection information system and fault recorder information system are introduced.These different information sources can be applied in the field of power network fault diagnosis,which also introduces information sources for transformer condition assessment based on phasor measurement unit proposed later.(2)Based on the information sources that the power grid can provide,the characteristics of the power grid fault diagnosis and transformer state assessment and the extraction methods of each characteristic parameter are introduced.This paves the way for the fault diagnosis of power grid and the condition evaluation of transformer.(3)A method for diagnosing grid faults based on electrical quantity data is proposed.The D-S evidence theory is improved by means of weighted average method.Then the feature information of power grid fault diagnosis is fused as the evidence body to obtain the comprehensive fault reliability.Finally,the diagnosis decision is made based on the fuzzy Cmeans algorithm,and the final result is obtained.(4)A hierarchical evaluation method of transformer state is proposed.For transformer with obvious state change,the state change of transformer is reflected by the index based on transformer efficiency.In the case of no obvious state difference,the fuzzy comprehensive evaluation method based on multi-feature information is adopted to realize transformer state evaluation.