Steven Macpherson Blair

An Open Platform for Rapid-Prototyping Protection and Control Schemes With IEC 61850

Abstract form only given. Communications is becoming increasingly important to the operation of protection and control schemes. Although offering many benefits, using standards-based communications, particularly IEC 61850, in the course of the research and development of novel schemes can be complex. This paper describes an open source platform which enables the rapid-prototyping of communications-enhanced schemes. The platform automatically generates the data model and communications code required for an Intelligent Electronic Device (IED) to implement publisher-subscriber Generic Object-Oriented Substation Event (GOOSE) and Sampled Value (SV) messaging. The generated code is tailored to a particular System Configuration Description (SCD) file, and is therefore extremely efficient at run-time. It is shown how a model-centric tool, such as the open source Eclipse Modeling Framework, can be used to manage the complexity of the IEC 61850 standard, by providing a framework for validating SCD files and by automating parts of the code generation process.

Current–Time Characteristics of Resistive Superconducting Fault Current Limiters

Superconducting fault current limiters (SFCLs) may play an important role in power-dense electrical systems. Therefore, it is important to understand the dynamic characteristics of SFCLs. This will allow the behavior of multiple SFCLs in a system to be fully understood during faults and other transient conditions, which will consequently permit the coordination of the SFCL devices to ensure that only the device(s) closest to the fault location will operate. It will also allow SFCL behavior and impact to be taken into account when coordinating network protection systems. This paper demonstrates that resistive SFCLs have an inverse current-time characteristic: They will quench (become resistive) in a time that inversely depends upon the initial fault current magnitude. The timescales are shown to be much shorter than those typical of inverse overcurrent protection. A generic equation has been derived, which allows the quench time to be estimated for a given prospective fault current magnitude and initial superconductor temperature and for various superconducting device and material properties. This information will be of value to system designers in understanding the impact of SFCLs on network protection systems during faults and in planning the relative positions of multiple SFCLs.

Analysis of Energy Dissipation in Resistive Superconducting Fault-Current Limiters for Optimal Power System Performance

Fault levels in electrical distribution systems are rising due to the increasing presence of distributed generation, and this rising trend is expected to continue in the future. Superconducting fault-current limiters (SFCLs) are a promising solution to this problem. This paper describes the factors that govern the selection of optimal SFCL resistance. The total energy dissipated in an SFCL during a fault is particularly important for estimating the recovery time of the SFCL; the recovery time affects the design, planning, and operation of electrical systems using SFCLs to manage fault levels. Generic equations for energy dissipation are established in terms of fault duration, SFCL resistance, source impedance, source voltage, and fault inception angles. Furthermore, using an analysis that is independent of superconductor material, it is shown that the minimum required volume of superconductors linearly varies with SFCL resistance but, for a given level of fault-current limitation and power rating, is independent of system voltage and superconductor resistivity. Hence, there is a compromise between a shorter recovery time, which is desirable, and the cost of the volume of superconducting material needed for the resistance required to achieve the shorter recovery time.

Application of Multiple Resistive Superconducting Fault-Current Limiters for Fast Fault Detection in Highly Interconnected Distribution Systems

Superconducting fault-current limiters (SFCLs) offer several benefits for electrical distribution systems, especially with increasing distributed generation and the requirements for better network reliability and efficiency. This paper examines the use of multiple SFCLs in a protection scheme to locate faulted circuits, using an approach which is radically different from typical proposed applications of fault current limitation, and also which does not require communications. The technique, referred to as “current division discrimination” (CDD), is based upon the intrinsic inverse current-time characteristics of resistive SFCLs, which ensures that only the SFCLs closest to a fault operate. CDD is especially suited to meshed networks and particularly when the network topology may change over time. Meshed networks are expensive and complex to protect using conventional methods. Simulation results with multiple SFCLs, using a thermal-electric superconductor model, confirm that CDD operates as expected. Nevertheless, CDD has limitations, which are examined in this paper. The SFCLs must be appropriately rated for the maximum system fault level, although some variation in actual fault level can be tolerated. For correct coordination between SFCLs, each bus must have at least three circuits that can supply fault current, and the SFCLs should have identical current-time characteristics.

Standardization of power system protection settings using IEC 61850 for improved interoperability

One of the potential benefits of smart grid development is that data becomes more open and available for use by multiple applications. Many existing protection relays use proprietary formats for storing protection settings. This paper proposes to apply the IEC 61850 data model and System Configuration description Language (SCL), which are formally defined, to represent protection settings. Protection setting files in proprietary formats are parsed using rule-based reasoning, mapped to the IEC 61850 data model, and exported as SCL files. An important application of using SCL-based protection setting files is to achieve protection setting interoperability, which could bring multiple compelling benefits, such as significantly streamlining the IED configuration process and releasing utilities from being “locked in” to one particular vendor. For this purpose, this paper proposes a uniform configuration process for future IEDs. The challenges involved in the implementation of the proposed approach are discussed and possible solutions are presented.

The use of real time digital simulation and hardware in the loop to de-risk novel control algorithms

Low power demonstrators are commonly used to validate novel control algorithms. However, the response of the demonstrator to network transients and faults is often unexplored. The importance of this work has, in the past, justified facilities such as the T45 Shore Integration Test Facility (SITF) at the Electric Ship Technology Demonstrator (ESTD). This paper presents the use of real time digital simulation and hardware in the loop to de-risk a innovative control algorithm with respect to network transients and faults. A novel feature of the study is the modelling of events at the power electronics level (time steps of circa 2 μs) and the system level (time steps of circa 50 μs).

Automatically Detecting and Correcting Errors in Power Quality Monitoring Data

Dependable power quality (PQ) monitoring is crucial for evaluating the impact of smart grid developments. Monitoring schemes may need to cover a relatively large network area, yet must be conducted in a cost-effective manner. Real-time communications may not be available to observe the status of a monitoring scheme or to provide time synchronization and, therefore, undetected errors may be present in the data collected. This paper describes a process for automatically detecting and correcting errors in PQ monitoring data, which has been applied in an actual smart grid project. It is demonstrated how to: unambiguously recover from various device installation errors; enforce time synchronization between multiple monitoring devices and other events by correlation of measured frequency trends; and efficiently visualize PQ data without causing visual distortion, even when some data values are missing. This process is designed to be applied retrospectively to maximize the useful data obtained from a network PQ monitoring scheme, before quantitative analysis is performed. This work therefore ensures that insights gained from the analysis of the data—and subsequent network operation or planning decisions—are also valid. A case study of a U.K. smart grid project, involving wide-scale distribution system PQ monitoring, demonstrates the effectiveness of these contributions. All source code used for this paper is available for reuse.

A Practical and Open Source Implementation of IEC 61850-7-2 for IED Monitoring Applications

A new open source mapping of IEC 61850-7-2 to web services has been defined and implemented. This letter describes work which is useful for rapidly implementing user interfaces-particularly web-based interfaces-for monitoring and controlling intelligent electronic devices from multiple vendors. The web service mapping has been implemented using the Hypertext Transfer Protocol, with a message format in JavaScript Object Notation. This approach requires a simple and ubiquitous software stack for its implementation, which is a significant advantage over existing client-server communications mappings. The use of an open source paradigm allows for the rapid iteration and refinement of the design, implementation, and testing of the internal details of the proposed protocol stack in a collaborative manner. These developments are of immediate interest to users of IEC 61850, and are particularly relevant to the IEC 61850 standardization process.

Real-time compression of IEC 61869-9 sampled value data

Fast-acting, yet cost-effective, communications is critical for smarter grid monitoring, protection, and control. This paper demonstrates a new approach for the real-time compression of Sampled Value (SV) data based on the IEC 61869-9 recommendations. This approach applies simple compression rules, yet yields excellent compression performance - typically compressing data to less than half of the original size. This leads to a significant and beneficial reduction in encoding time (in the merging unit producing the SV data) and decoding time (at the end application), as well as the main benefit of reduced Ethernet transmission times resulting from the reduced frame size. As well as reducing the absolute bandwidth requirements in typical applications, this has system-wide benefits due to reducing Ethernet queuing delays and the consequent network jitter. The approach has been validated on a real-time platform to accurately measure all contributions to the end-to-end delay. This work will help enable low-latency and bandwidth-sensitive applications involving the SV protocol, such as phasor measurement units and wide-area protection.

Application of MPLS-TP for transporting power system protection data

Power utilities are increasingly dependent on the use of communications networks. These networks are evolving to be packet-based, rather than using conventional Time-Division Multiplexing (TDM) technologies. Transporting current differential protection traffic over a packet network is especially challenging, due to the safety-critical nature of protection, the strict requirements for low delay and low asymmetrical delay, and the extensive use of legacy TDM-based protocols. This paper highlights the key technical characteristics of Multi-Protocol Label Switching-Transport Profile (MPLS-TP), and demonstrates its application for transporting current differential protection traffic. A real-time hardware-in-the-loop testing approach has been used to thoroughly validate the technologies in various configurations. It is demonstrated that MPLS-TP technologies can meet the requirements of current differential protection and other, less critical applications. In particular, it is shown that delay and asymmetrical delay can be controlled through the inherent use of bi-directional paths-even when “hitless” link redundancy is configured. The importance of appropriate traffic engineering, clocking schemes, circuit emulation methods is also demonstrated.