Contributions of the Thesis and Methodology

According to these motivations, an analysis and investigation were carried out based on a comprehensive research work to present the impact of the IEC 61850 standards on SASs’ operations considering the reliability of the SASs’ functions and the robustness of the SASs’ communications system network in various cir-cumstances. The highlights of the research tasks were classified based on the the-oretical and practical tests variously throughout Chapters 2-4 as mentioned earli-er, and are listed below.

1 To investigate the impact of the IEC 61850 standards on SASs’ reliability, the availability of the breaker failure protection (BFP) function has been analyzed. Reliability and availability are two of the primary considera-tions in current and future SAS design. The importance for this investiga-tion has been to provide the reliability and availability of the BFP funcinvestiga-tion in which, with n = 1, the other protection-related SAS functions are a sub-set of the BFP function. The analysis was carried out over the small transmission substation 220/132 kV platform classified as T1-1 with a single bus which is assigned by the IEC 61850 standard using an RBD method. Comparisons between the reliability and availability results for various substation communications network topologies have been carried out. Redundancy has been identified as key to increasing SASs’ reliability (Mekkanen etc. 2012).

2 A generic, novel reliability and probability of failure estimation algorithm (RaFSA) had been invented. The RaFSA estimation method is suitable for estimating the reliability and probability of failure for any individual de-vice, function, subsystem or system. The RaFSA estimations are imple-mented over a practical, small transmission substation, T1-1. Various SAS communications bus topologies are considered. A stochastic simulation approach is the way in which RaFSA estimations are implemented. The RaFSA estimation method attempts to examine and predict the actual be-haviour pattern for each device in the automation system. Various ad-vantages were noted through the implementation of the novel method RaFSA, as illustrated in Chapter 2.2. (Mekkanen etc. 2013a).

3 To evaluate the system’s reliability and probability of failure functions, it was developed based on the simulation of a novel approach to various SAS communications bus topologies and experimental tests were carried out. A sequential Monte Carlo simulation method was used based on the reliability and probability of failure evaluations of the RaFSA estimation

method. These evaluations were implemented over the small transmis-sion substation T1-1 for the BFP function. According to the developed so-lution, various advantages were achieved (e.g., it is a flexible solution that has the ability to change, expand input data and include various parame-ters in the calculation without the need to change the underlying process) (Mekkanen et al. 2013b). In addition, comparisons between the mathe-matical and RaFSA reliability and probability of failure results’ output values were carried out, showing that significant variations in the RaFSA results values about the true value occur when the number of trials is small. In contrast, the number of variations is significantly reduced as the number of trials increases, converging on the true values.

4 Within the practical analysis and in the first step, a proper approach for estimating the high-speed priority messages’ latencies has been developed which is suitable for the dynamic characteristics of the SAS communica-tions network (a round-trip approach). Further, this approach reflects the real behaviour of the devices in the system. In the next step, the utiliza-tion of the developing approach is carried out based on the design of the actual physical SAS. The output results values from these practical exper-iments show that the devices under testing (DUTs) are compliant with the IEC 61850 criteria. Furthermore, it proves the interoperability concept such that the DUTs subscribe to the GOOSE messages from a third-party IED within the designed SAS (Mekkanen etc. 2013d). (Mekkanen etc.

2014a).

5 The second issue related to the practical study was, firstly, to enhance and relax the system configuration task using a novel approach for which a new vendor/natural SAS configuration tool has been invented which is in-dependent of any commercial IED brand. The vendor/natural system con-figuration tool has the ability to import various types of IEC 61850 specific configuration files from different manufacturers, IEDs, systems and da-tabases, and increases the relay configuration to the system level based on the full IEC 61850 standard, including the protection and fea-ture setting levels. Further, this tool is expected to reduce costs and effort involved as well as the time taken for AS configuration and commission-ing tasks. Secondly, the vendor/natural system configuration tool has been proposed for large utilities that comprise various manufacturer units and IEDs to re-lax the system configuration task and support the expan-sion of the IEC 61850 standard so as to go beyond SASs, emerging to-wards the SG concept (Mekkanen etc. 2014b) (Mekkanen etc. 2014c).

6 The last issue related to the practical study was, firstly, to facilitate the de-sign of the SAS by assessing the capacity of the process bus communica-tions network. For testing purposes, the modelling of various IEDs, such as MUs, ESW, the communication link and the receiving IED (which have not been developed yet and do not exist in the OPNET simulation tool li-brary) has been carried out. Within these modelled IEDs, various com-munications network parameters need to be considered in order to simu-late a typical IEC 61850-9-2LE process bus. The SV traffic stream simu- laten-cies were successfully measured in two scenarios that confirmed that the first Ethernet switch experienced more latency than the subsequent switches, such that the limits and capacity of the process bus network’s critical components (such as the communication links and the Ethernet switch) have been assessed successfully. Secondly, a novel approach for estimating the SV packets’ stream latencies based on a time analysis for a series of successive receiving packets has been developed. The developed SV packets stream latency approach has been implemented and tested over the typical designed IEC 61850-9-2LE process bus communications network. Lastly, comparisons between the IEC 61850-9-2LE process bus laboratory’s practical experiments and the IEC 61850-9-2LE process bus OPNET simulation models’ output results have been carried out (Mek-kanen etc. 2014d) (Mek(Mek-kanen etc. 2014e) (Mek(Mek-kanen etc. 2014f).

7 To reduce and enhance the energy system’s operational costs, an alterna-tive novel framework for the communications system in an SG has been proposed. The novelty of the proposed communications model is that it at-tempts to bring about a reasonable change in SG’s communication in-fra-structure. The study considers wireless communication as a medium and introduces the CR technology. Further, the feasibility of CR in identi-fying the available spectrum (even with a very low SNR based on sub-scribing and sensing) has been demonstrated. This task was carried out by using the feature detection method “cyclostationary” within the MATLAB soft-ware environment. The alternative novel framework has many advantages that can be summarized as a reduction in the network’s communications system infrastructure costs based on avoiding wired ap-plications and reusing the licensed frequency bands, thereby providing more affordable services (Mekkanen etc. 2013c).