STANDARDIZATION OF SERIAL LINKS REPLACING PARALLEL WIRING TO TRANSFER PROCESS DATA: APPROACH, STATE AND PRACTICAL EXPERIENCE

摘要

One result of the deregulation of the energy market isrnthat the need for the automation of substation is morernand more of interest. The basis for the total automationrnis today not fully given. One reason is that automationrnneeds sensors to get the topical state of the wholernprocess. But today there is no economical way tornconnect all these sensors to the control level. Anotherrnreason is that novel electronic current and voltagerntransducers as well as other intelligent control andrnmonitoring equipment for switchgear apparatus’rnprovide such a mass of process data that these can nornlonger be transported to the bay level by parallelrncopper wiring. Therefore standardised serial fiber opticrncommunication systems are used to interface thernprimary apparatus’ (process level) to the control andrnprotection functions on bay level. An overview of thernfunctional requirements for such serial communicationrnsystem is provided in this contribution. Among thernfunctional requirements, defined in terms of abstractrncommunication services to be supported by therncommunication system, two time critical ones arernidentified: (1) the service to exchange binaryrninformation used e.g. to transmit trip commands; (2) thernservice to transmit the raw data (samples) from thernelectronic transducers.rnA brief refresh of the approach followed in the currentrnstandardisation activities within IEC TC57 and in cooperationrnwith IEEE / EPRI is presented. Differentrnconcepts for the architecture of the communicationrnsystem are discussed. The range of concepts includes arnhierarchic architecture with two communication levelsrn(station bus and process bus), a mixed architecturernincluding dedicated point to point links as well as arnstation wide, flat communication network. The solutionsrnfor the implementation of the abstract services arernexplained with a focus on the time critical ones. Whilernthe non-time critical services are implemented on a fullrn7-layer OSI reference model stack, the time criticalrnservices are using an architecture with a reducedrnnumber of layers.rnThe main part of the contribution consists of a detailedrnreport on verification activities and field experiences.rnThe usability of the solutions as proposed in thernstandards series has been evaluated in a number ofrntheoretical verification steps including simulation ofrntypical system configurations. This has been followed byrnvarious practical verifications in prototypernimplementations and demonstrations with equipmentrnfrom different vendors both from Europe as well as fromrnUS.rnThe paper will conclude with an outlook. The standardsrnseries will provide the capability for a stepwisernmigration from a conventional to a fully integratedrnsubstation automation system. Automation solutionsrnwith increased functionality, which will be possible byrnusing the new communication technology as proposedrnby the future standards, are discussed.