Research On Digital Differential Relay Protection Of Smart Substation

Smart substation in the smart grid trend is now the research focus,and will become one of the main development directions of smart grid.Along with the development of the smart substation,theautomation system oftraditional substation will gradually get off from the pattern.With the development of smart grid technology,data synchronization has faced a new challenge: the collection of electric quantity of the traditional substation is simulated,and the data transmission is from the electro-magnetic current transformer and the voltage transformer to the protection device.Smart substation effectively changed the traditional substation construction and operation mode.An important embodiment of smart substation is the digital process of layers devices,and one of their characteristics is that the information of operation of the power grid achieves digital output to the microcomputer protection device.Since the realization of the digital main transformer differential protection and optical fiber differential protection,it is different from the traditional substation of the situation.Therefore,it is necessary to reconsider the issue of data synchronization.The data synchronization of differential protection is related to the reliability of differential protection.If the data is out of step,it will bring some accident to differential protection.As for the data synchronization problem of optical fiber differential protection and the main transformer differential protection in smart substations,this paper conducts research and achievements as follows:First,this paper discusses several differential data synchronization methods in the traditional mode.The limitations and shortcomings of the traditional mode differential data synchronization methods are analyzed.An improved interpolation method is proposed based on the traditional optical fiber differential interpolation method,which can be applied to digital line optical fiber longitudinal differential protection and digital main transformer differential protection.Second,the data synchronization method is proposed that it can be measured in real time and adapt to the variation of the delay of the optical fiber longitudinal differential channel.The principle is discussedin detail.The time delay can be compensated perfectly.The synchronous precision is not affected by the change of the channel transmission delay.Besides,the reliability of the proposed method is less affected by the channel.The two sides are not divided,with the status and the equal processing mechanism.And an example of the smart substation of the Hua Tie Substations is providedto discuss the digital differential protection.At last,the data synchronization method based on the delay measurable switch is studied,and a high level of data synchronization isachieved.