Real-time Performance And Reliability Of The Communication System Of Smart Substation

The smart substation (SS) has provided standard and reliable supports for smart grid. As theneural system of the SS, the communication network is the links that bonds all kinds of IEDstogether, and its real-time performance and reliability determine the availability of the smartsubstation. Modeling and analyzing the performances of the network system by differentintelligent models can effectively improve the reliability of the whole system. The followingachievements have been obtained through theory analysis and simulation experiments.This paper has constructed the mathematical models for inner data flow in SS to analyze thecomposition of the transmission delay non-determinism of messages, and made simulationexperiments by using OPNET. The paper also discussed the influence of VLAN to the real-timeperformance of the communication network of SS, and the results have showed that theapplication of VLAN in network of SS can decrease the time delay of messages, control thespread of the broadcast storm, and improve the security of the system.This paper has researched the delay-non-determinism caused by queuing in the buffers ofSMU on emergency based on multi-server queuing theory, and deduced the analytic relationsbetween the buffer size, loss rate of package, and delay, by which, we can compute the buffersize of the SMU in station-level under the requirements of message loss rate and time delay. Thesimulization expreriment has showed that the theoretical method is correct and effective.This paper has proposed the integrative information transmission method based on the fractalleaky bucket and classification of service mechanism, which uses fractal leaky bucket to controlthe data flows those have Self-Similar characteristics, and uses the network calculus theory tocalculate the upperbound of transmission delay and statistical delay distribution. The method cannot only determine wheacher the End-To-End transmission delay is within the time limits, butalso objectively assess the pessimism degrees of the upperbound by statistical delay distribution,and all of this can provide better theoretical analysis tool for the construction of communicationnetwork under the requirements of time limits.This paper has constructed the fuzzy reliability model for the single bay-layer in process-level and introduced T-S fuzzy gate to construct the fuzzy fault tree of communication system of SS. By TS-FTA, we can deduce the fuzzy possibility of system failure from the fuzzy failure rateof basic events. This can not only solve the non-determinism of failure probability of eachcomponent and failure mechanism of the whole system, but also enrich the reliability evaluationmethods on communication system of SS.This paper has put forward the running state evaluation method of communication networksof SS based on tree augmented na ve possibilistic network classifier. By using the deteriorativedegree of each index which influences the running state of network as the attributes set, fourrunning states as the classes set, the proposed method used the index weight and ridge-shapeddistribution to describe the fuzzy memberships of a real instance to a class. Experiments hasshown that the method has better classification accuracy and can effectively solve the non-determinism in the state evaluation of network of SS.Researching the characheristics of application and technology of communication system ofSS, establishing the unite architecture of the communication system, analyzing it’s applicationmechanism of information and real-time performance and reliability, taking reasonable technicalmeasures to adapt to the application and development of the pilot project of SS, are veryimportant for the construction of smart grid.