Abstract
M.Ing. (Engineering Management)
The research is about the comparative study between IEC61850 and the conventional DNP3 protocol in as far as the practicability of their application in the modern substation environment is concerned. IEC61850 is a fairly new international standard and technology that entails numerous progressions to traditional Substation Automation Systems (SAS). Currently in South Africa, the major electricity supply utility, Eskom, has predominantly employed Distributed Network Protocol 3 (DNP3) technology for communicating data between protection and control devices. This protocol does not possess all the desirable attributes for use in the Smart Grid (The world is shifting towards smart grid operations). For instance, with IEC61850 the secondary power circuits are simplified by replacing clusters of wires in a substation with a simpler piece of equipment called a process bus. Faster performance speeds can then consequently be realized using Ethernet and Generic Object Orientated Substation Event (GOOSE) messaging in the new substation network which in turn results in a more reliable power system.
It is often a challenging task to evaluate the feasibility of the new technology such as IEC61850 when there are only few known cases of its implementation. There are numerous suggestions as to how IEC61850 should be implemented in the industries however; there is currently no one procedure that has been proven to be the best. In the face of this, IEC61850 has proven to be the future of communications in the power system protection environment. The numerous benefits of IEC61850 overshadow the currently utilized traditional protocols such as DNP3.
The Design alternatives analysis is thus conducted in this research to determine if power utilities can do away with the traditional DNP3 platforms in the name of introducing the revolutionary IEC61850 technology in their plants. A Monte Carlo approach is employed for comprehensive analysis of the design alternatives. All the inputs to Monte Carlo analysis are evaluated using the Simple Additive Weighting (SAW) strategy as a deterministic model within Monte Carlo to evaluate the probability of IEC61850 being the most preferred technology over DNP3. The inputs to Monte Carlo analysis are the weights of the technology selection criteria. The weights are computed from randomized judgement/comparison matrices using a Visual Basic (VBA) code in Excel. The design alternatives base rates within SAW analysis are determined through application of theory and laboratory experiments results. Intelligent Electronic Devices (IEDs) were used in the laboratory to evaluate the performance and characteristics of both IEC61850 and DNP3 technologies. The whole Monte Carlo procedure from determination of criteria comparison matrices to determining the probability of IEC61850 being the most preferred technology, is carried out by a VBA code complied in Microsoft Excel.
About 100 seven-criterion comparison matrices were generated within Microsoft Excel for the purpose of this study. After performing Monte Carlo analysis it was observed that the probability of IEC61850 being the most preferred technology in the industry was 0.46 for a worst case scenario whereby the flexible base rates in SAW analysis were maximized in favour of the DNP3 technology. For any other worst case scenarios studied in this research, IEC61850 proved to be more beneficial than DNP3 technology with a probability between 0.52 and 0.59. The selection criteria which allowed flexible base rates were; ease of system configuration, space saving and system scalability. The base rates for the performance speed, technology system effectiveness, reliability of the system, and purchase costs were fixed.