李娜 电气07K7班 071912010314 英文翻译原文.pdf

Scheme for integrated protection based on digital substation Li Peng 1 Qin Lijun 2 Digital Electricity and Energy Saving Research Center North China Electric Power University Beijing China 1982coolbingo 1 qin3388 2 Abstract With the development of digital substation technology sampled value and status information can be transmitted through optical fibers and shared within the substation Therefore digital substation provides conditions for the study of integrated protection Accordingly this paper proposes a scheme for integrated protection and mainly describes a method of real time database modeling for integrated protection Keywords digital substation integrated protection real time database I INTRODUCTION The developments of intelligent electronic device and digital communication have brought substation automation technology into a new stage which is called digital substation In digital substation analogue signals switch state control orders can be transfer into digital information This digital information can be transmitted through the distributed communication network based on IEC 61850 standard and shared in the digital substation So digital substation will have a significant impact on protection a The system architecture of a protection system may change IEC 61850 provides communication services that may be used to exchange binary information between IEDs Intelligent Electronic Device With that the wiring between the relays used to implement the protection schemes can be eliminated b The hardware and software design of protection equipment may change IEC61850 includes communication services to transmit samples from current and voltage transformers As a consequence process I Os can be eliminated from the relay hardware a protection relay may change to a pure computing device c The standard language and the use of a communication interface instead of physical wires will be conducive to integrate the functions of protection measurement and control fault recorder etc Based on the characteristics of digital substation as well as the above impact this paper proposes a scheme for integrated protection This scheme can achieve various protective functions of the substation as well as the functions of measurement and control fault recorder This scheme uses integrated configuration to achieve centralized management of the protection and can be combined with the redundant information adjacent protection to synthetically determine the operation of the protection Thereby it can improve the reliability of protection and also simplify the hardware settings and reduce the cost of investment II SCHEME FOR INTEGRATED PROTECTION As shown in Figure 1 this scheme of integrated protection is composed of three hardware components Merging Unit MU Intelligent Execution Unit IEU Integrated Protection Unit IPU the functions as follows Merging Unit It collects voltage and current information from the electronic transformer and converts them into digital signals then transmits them to the IPU Intelligent Execution Unit It controls the circuit breakers and switch collects switch status information and then transmits them to the IPU Integrated Protection Unit It is a platform for integrating all the protection of substation and stores the sampled value from MU and IEU Figure1 Scheme of integrated protection Figure1 describes the scheme of integrated protection In this scheme the sampled value from MU and the switch status information from the IEU are storage in the IPU Protection Algorithm of the IPU computes these values and combines with the switch status information to determine the operation of the protection Then the operation signals are translated into messages These messages such as the trip command of breaker or alarm message are transmitted to the IEU to determine the operation of the breakers In this program Integrated Protection Unit is dual configuration Two devices are each other s back Meanwhile the functions of measurement and control fault recorder can also be integrated into the IPU 2010 International Conference on Electrical and Control Engineering 978 0 7695 4031 3 10 26 00 2010 IEEE DOI 10 1109 iCECE 2010 1017 4189 2010 International Conference on Electrical and Control Engineering 978 0 7695 4031 3 10 26 00 2010 IEEE DOI 10 1109 iCECE 2010 1017 4189 At present the research of MU and IEU has gradually matured and has been applied to digital substation Consequently the key to achieve this integrated protection program is the research of the IPU III INTEGRATED PROTECTION UNIT Integrated Protection Unit needs to receive large amounts of real time sampled data from all IEDs To complete these sampled data processing and storage we need to establish a real time database It can be said that real time database is the core of the Integrated Protection Unit Figure2 Configuration of Integrated Protection Unit As shown in figure2 the configuration of IPU is composed of three parts real time database RTDB historical database protection program Their functions are as follows Real time database It receives the sampled data from electronic transformer and IEU and completes sampled data processing and storage Historical database The real time data from RTDB can be compressed and the compressed data as historical record is stored in historical database for inquiry Protection program It includes a variety of protection algorithms which are real time computing the sampled data Calculation results combine with the switch status information to determine the operation of the protection and then transmit the operation signals to the IEU The realization of an Integrated Protection Unit is based on real time database platform The real time database for IPU should have the following characteristics a Real time performance Real time data and transaction of the RTDB have strict timing constraints real time performance is a basic requirement for RTDB b Appropriate scheduling policy The choice of scheduling policy should be able to meet the requirements of transaction priority and time synchronization c Data Retrieval The sampling period of the relay protection is very short So the speed of data retrieval should be higher to meet the requirements of time limit d Comply with IEC61850 standard Data structures of the RTDB as well as the establishment of data and services must be based on the various data and service model which are defined in the IEC61850 standards such as Server Logical Device Logical Node etc Therefore the design of the real time database structure for Integrated Protection Unit must be based on the above requirements IV STRUCTURE OF REAL TIME MAIN MEMORY DATABASE BASE ON IEC61850 The design of Main Memory Database based on the IEC61850 standard includes three aspects logical structure storage structure and transaction scheduling strategy A Logic structure The IEC61850 standard defines the Substation Configuration description Language SCL It mainly describes the configuration and parameters of IDE communication system and its configuration and the structure of substation system So the database modeling based on the IEC61850 standard needs to analyze SCL Then we can dynamically create and manage data structures of RTDB according to the layer and contents of SCL and create object oriented data and services according to the definition of corresponding class in the IEC61850 class libraries By means of analyzing the structure and composition of SCL the elements of SCL can be expressed as multi branch tree nodes But multi branch tree structure is very complicated and not convenient for storage and searches So we need to transform SCL multi branch tree structure into binary tree structure to increase the retrieval speed in order to satisfy the requirement of real time performance In the multi branch tree structure of SCL we analyze the child nodes of logic nodes one by one and create corresponding binary tree nodes In this way those nodes will be created and added as child nodes of the binary tree Finally we can create a binary tree structure model layer by layer which is shown in fig 3 Figure3 The structure of binary tree of SCL B Storage structure The logic structure of real time database is binary tree structure Its storage modes contain sequential storage binary 41904190 linked list trigeminal linked list etc Sequential storage is fit for the storage of complete binary tree storage It is beneficial to determine the relationship between nodes but not beneficial to the deletion or insertion of node And it also wastes memory space Linked list is fit for the storage of ordinary binary tree It uses pointer to create multidirectional linked list and is very flexible and convenient to insert or delete node Considering the demands of real time database this article adopts trifurcate chain table structure based on binary tree As shown in fig 4 Using this storage structure can quickly and accurately judge the structural relation between random two nodes in the structure tree and can insert or delete nodes quickly Figure4 Storage structure of trifurcate chain table structure based on binary tree C Transaction scheduling strategy At present real time transaction scheduling mainly adopts the priority based scheduling scheme According to the requirements of real time performance transactions can be divided into urgent transaction real time transaction and non real time transaction In terms of dynamic priority we make those transactions mentioned above serializable and then form three scheduling sequence While the transaction scheduling the urgent transactions sequence must be executed preferentially And we use the scheduling protocol which is based on the first come first service principle in order to make sure that the urgent tasks can be finished in time V MODELING REAL TIME DATABASE FOR IPU After completing the real time main memory database modeling Data Objects and their corresponding services should be added to the appropriate location of the database structure Because this real time database is used for IPU we consider adding the corresponding data objects to the main memory data base on the functional structure of integrated protection As shown in figure5 integrated protection mainly has transformer protection line protection and capacitor protection In figure5 server represents servers of IED which own different functions LD represents logical device which is composed of logical nodes and their accessorial service LLNO is logical node and it represents public data of logical device such as nameplate status information of device etc LPHD represents public data of physical device which owns logical nodes such as the nameplate of physical device and status information LN represents the function of physical device Figure5 Functional structure of integrated protection Take transformer protection for example there are four servers under the transformer protection a In Server1 logical device LD1 contains TCTR and TVTR which represent respectively current transformer and voltage transformer and accomplish collection of current sample and voltage sample b Server2 contains two logical nodes CSWI and XCBR CSWI is the logical node of switch controller it controls the on off conditions XCBR is the logical node of breaker it is applied for the modeling of breakers which have function of cutting short circuit current This server mainly describes the control and functions of breakers c LD3 and LD4 are logical devices in Server3 Those two logical devices together can achieve the function of protection and measure LD3 is defined as protective function The logical nodes of PDIF PHAR PLOC PTRC and RADR respectively achieve the function of current differential instantaneous trip protection harmonic restraining instantaneous over current protection trip conditions of protection and disturbance records LD4 corresponds to the measure function d In Server4 LD5 corresponds to human machine interface function The logical node IHMI in the LD5 represents the function local settings and manual operation Figure5 mainly describes the structure of transformer protection which is similar to the line protection and capacitor protection Add all of the corresponding logical nodes into real time main memory database of binary tree structure In this way the construction of real time database for IPU can be accomplished layer by layer Now we take the logical node TCTR for example to explain the specific process 41914191 1 According to the SCL document we create a DOM Document Object Model tree structure and then create the corresponding binary tree node by parsing the DOM layer by layer until we get the logical node TCTR Then we search for the LN node whose attribute Value equal to TCTR in the Data Type Template of the DOM So the child node of this LN node is also the child node of TCTR Afterward we parse the child nodes of the LN node one by one and add them as the child nodes of the TCTR and create a binary tree structure layer by layer In the end we can get a binary tree structure of the Data Objects DO of the TCTR 2 According to identifier attribute value of each child nodes of the Data Objects we search for the class whose name is same to the identifier attribute value in the IEC61850 class library and instantiate this class in the memory 3 We convert the pointer of the Data Object which is instantiated in the memory into the void type of pointer and assign the value of this pointer to the PtrObject property of the child node of Data Object In this way the pointer of Data Objects in the memory is saved in pointer field of the corresponding child node Finally the data structure of memory database is linked to the Data Objects In accordance with the above method all the logical nodes can be added to the binary tree structure of the memory database Meanwhile these logical nodes compose the LD logical device according to the appropriate functions combination and then different LDs compose Servers according to certain orders Thereby the construction of real time database for IPU can be accomplished layer by layer VI CONCLUSION The integrated protection is the development direction of the relay protection in digital substation Research of integrated protection based on digital substation has great significance However it should be noted that the study about integrated protection has just started and has many difficulty The theory of this paper is not very mature and need for further research REFERENCES 1 Christoph Brunner The impact of IEC61850 on protection IET 9th International Conference on17 20 March 2008 pp 14 19 2 HE Shi en LIU Jun Impacts of IEC 61850 digital substation on relaying protection Power S