Evaluation of Time-Critical Communications for IEC 61850-Substation Network Architecture

Present-day developments, in electrical power transmission and distribution, require considerations of the status quo. In other meaning, international regulations enforce increasing of reliability and reducing of environment impact, correspondingly they motivate developing of dependable systems. Power grids especially intelligent (smart grids) ones become industrial solutions that follow standardized development. The International standardization, in the field of power transmission and distribution, improve technology influences. The rise of dedicated standards for SAS (Substation Automation Systems) communications, such as the leading International Electro-technical Commission standard IEC 61850, enforces modern technological trends in this field. Within this standard, a constraint of low ETE (End-to-End) latency should be respected, and time-critical status transmission must be achieved. This experimental study emphasis on IEC 61850 SAS communication standard, e.g. IEC 61850 GOOSE (Generic Object Oriented Substation Events), to implement an investigational method to determine the protection communication delay. This method observes GOOSE behaviour by adopting monitoring and analysis capabilities. It is observed by using network test equipment, i.e. SPAN (Switch Port Analyser) and TAP (Test Access Point) devices, with on-the-shelf available hardware and software solutions

Investigating Performance and Reliability of Process Bus Networks for Digital Protective Relaying

To reduce the cost of complex and long copper wiring, as well as to achieve flexibility in signal communications, IEC 61850 part 9-2 proposes a process bus communication network between process level switchyard equipments, and bay level protection and control (P&C) Intelligent Electronic Devices (IEDs). After successful implementation of Ethernet networks for IEC 61850 standard part 8-1 (station bus) at several substations worldwide, major manufacturers are currently working on the development of interoperable products for the IEC 61850-9-2 based process bus. The major technical challenges for applying Ethernet networks at process level include: 1) the performance of time critical messages for protection applications; 2) impacts of process bus Ethernet networks on the reliability of substation protection systems. This work starts with the performance analysis in terms of time critical Sampled Value (SV) messages loss and/or delay over the IEC 61850-9-2 process bus networks of a typical substation. Unlike GOOSE, the SV message is not repeated several times, and therefore, there is no assurance that each SV message will be received from the process bus network at protection IEDs. Therefore, the detailed modeling of IEC 61850 based substation protection devices, communication protocols, and packet format is carried out using an industry-trusted simulation tool OPNET, to study and quantify number of SV loss and delay over the process bus. The impact of SV loss/delay on digital substation protection systems is evident, and recognized by several manufacturers. Therefore, a sample value estimation algorithm is developed in order to enhance the performance of digital substation protection functions by estimating the lost and delayed sampled values. The error of estimation is evaluated in detail considering several scenarios of power system relaying. The work is further carried out to investigate the possible impact of SV loss/delay on protection functions, and test the proposed SV estimation algorithm using the hardware setup. Therefore, a state-of-the-art process bus laboratory with the protection IEDs and merging unit playback simulator using industrial computers on the QNX hard-real-time platform, is developed for a typical IEC 61850-9-2 based process bus network. Moreover, the proposed SV estimation algorithm is implemented as a part of bus differential and transmission line distance protection IEDs, and it is tested using the developed experimental setup for various SV loss/delay scenarios and power system fault conditions. In addition to the performance analysis, this work also focuses on the reliability aspects of protection systems with process bus communication network. To study the impact of process bus communication on reliability indices of a substation protection function, the detailed reliability modeling and analysis is carried out for a typical substation layout. First of all, reliability analysis is done using Reliability Block Diagrams (RBD) considering various practical process bus architectures, as well as, time synchronization techniques. After obtaining important failure rates from the RBD, an extended Markov model is proposed to analyze the reliability indices of protection systems, such as, protection unavailability, abnormal unavailability, and loss of security. It is shown with the proposed Markov model that the implementation of sampled value estimation improves the reliability indices of a protection system

On reliability and performance analyses of IEC 61850 for digital SAS

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An open platform for rapid-prototyping protection and control schemes with IEC 61850

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 to implement a publisher-subscriber generic object-oriented substation event and sampled-value messaging. The generated code is tailored to a particular system configuration description (SCD) file, and is therefore extremely efficient at runtime. It is shown here 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. The flexibility and convenience of the platform are demonstrated through a prototype of a real-time, fast-acting load-shedding scheme for a low-voltage microgrid network. The platform is the first open-source implementation of IEC 61850 which is suitable for real-time applications, such as protection, and is therefore readily available for research and education

Secure Control and Operation of Energy Cyber-Physical Systems Through Intelligent Agents

The operation of the smart grid is expected to be heavily reliant on microprocessor-based control. Thus, there is a strong need for interoperability standards to address the heterogeneous nature of the data in the smart grid. In this research, we analyzed in detail the security threats of the Generic Object Oriented Substation Events (GOOSE) and Sampled Measured Values (SMV) protocol mappings of the IEC 61850 data modeling standard, which is the most widely industry-accepted standard for power system automation and control. We found that there is a strong need for security solutions that are capable of defending the grid against cyber-attacks, minimizing the damage in case a cyber-incident occurs, and restoring services within minimal time. To address these risks, we focused on correlating cyber security algorithms with physical characteristics of the power system by developing intelligent agents that use this knowledge as an important second line of defense in detecting malicious activity. This will complement the cyber security methods, including encryption and authentication. Firstly, we developed a physical-model-checking algorithm, which uses artificial neural networks to identify switching-related attacks on power systems based on load flow characteristics. Secondly, the feasibility of using neural network forecasters to detect spoofed sampled values was investigated. We showed that although such forecasters have high spoofed-data-detection accuracy, they are prone to the accumulation of forecasting error. In this research, we proposed an algorithm to detect the accumulation of the forecasting error based on lightweight statistical indicators. The effectiveness of the proposed algorithms was experimentally verified on the Smart Grid testbed at FIU. The test results showed that the proposed techniques have a minimal detection latency, in the range of microseconds. Also, in this research we developed a network-in-the-loop co-simulation platform that seamlessly integrates the components of the smart grid together, especially since they are governed by different regulations and owned by different entities. Power system simulation software, microcontrollers, and a real communication infrastructure were combined together to provide a cohesive smart grid platform. A data-centric communication scheme was selected to provide an interoperability layer between multi-vendor devices, software packages, and to bridge different protocols together

A methodology for performance and compatibility evaluation of an all-digital substation protection system

A power system protection system consists, at least, of an instrument trans- former, a protective device (relay), and a circuit breaker. Conventional instrument transformers bring currents and voltages from power network levels to much lower scaled-down replicas that serve as input signals to protective relays. The relay's function is to measure input signals (or a relationship among them in some cases) and compare them to defined operating characteristic thresholds (relay settings) to quickly decide whether to operate associated circuit breaker(s). Existing protection systems within a substation are based on a hardwired interface between instrument transformers and protective relays. Recent development of electronic instrument transformers and the spread of digital relays allow the development of an all-digital protection system, in which the traditional analog interface has been replaced with a digital signal connected to digital relays through a digital communication link (process bus). Due to their design, conventional instrument transformers introduce distortions to the current and voltage signal replicas. These distortions may cause protective relays to misoperate. On the other hand, non-conventional instrument transformers promise distortion-free replicas, which, in turn, should translate into better relay performance. Replacing hardwired signals with a communication bus also reduces the significant cost associated with copper wiring. An all-digital system should provide compatibility and interoperability so that different electronic instrument transformers can be connected to different digital relays (under a multi-vendor connection) Since the novel all-digital system has never been implemented and/or tested in practice so far, its superior performance needs to be evaluated. This thesis proposes a methodology for performance and compatibility evaluation of an all-digital protection system through application testing. The approach defines the performance indices and compatibility indices as well as the evaluation methodology

Power Systems Monitoring and Control using Telecom Network Management Standards

Historically, different solutions have been developed for power systems control and telecommunications network management environments. The former was characterized by proprietary solutions, while the latter has been involved for years in a strong standardization process guided by criteria of openness. Today, power systems control standardization is in progress, but it is at an early stage compared to the telecommunications management area, especially in terms of information modeling. Today, control equipment tends to exhibit more computational power, and communication lines have increased their performance. These trends hint at some conceptual convergence between power systems and telecommunications networks from a management perspective. This convergence leads us to suggest the application of well-established telecommunications management standards for power systems control. This paper shows that this is a real medium-to-long term possibility

Transformer load tap changer control using IEC 61850 GOOSE messaging

The research of this thesis implements Load Tap Changer (LTC) control using the International Electrotechnical Commission (IEC) 61850 standard in a laboratory environment. In particular, Generic Object Oriented Substation Event (GOOSE) messages are used to facilitate all required communication. A set of two Schweitzer Engineering Laboratories, Inc. (SEL) devices is used for the demonstration. IEC 61850 has many benefits including great flexibility and improved interoperability and promises to be more widely implemented in the United States with time as is already the case in many other parts of the world. This research shows that LTC operation using IEC 61850 is reliable and brings with it all the benefits that the implementation of IEC 61850 has to offer. Above all, due to elimination of the majority of copper wiring, the proposed method is very flexible and can be implemented using a variety of different devices

Interfacing IEC 61850-9-2 Process Bus Data to a Simulation Environment

IEC 61850 – Communication and networks in substations is the standard for building communication infrastructure between the different Intelligent Electronic devices (IEDs) in the substation automation system. It consists of several parts which include Specific Communication and Service Mapping for the transmission of sampled values (defined in part 9–2 of the standard). The Sampled value communication is a high speed, time critical Ethernet based communication for the transfer of data over the network. It defines the sampling rate and time synchronization requirement of the system. The main purpose of this thesis is to extract sampled value data (four voltages, four currents) from a PCAP data file captured over the network in the ‘Sundom Smart Grid’ environment and convert the data into the format needed for analysis on PSCAD simulation tool. This thesis serves as an interface between the real Smart Grid environment and the test environment in the University of Vaasa. This thesis explains fundamental concepts that relate to IEC 61850, and the Sampled Value in particular. It describes the frame structure of sampled value and a software application has been developed based on WinPcap Application Program Interface (API) to extract the data points needed and fulfill the data format requirement of the PSCAD which is adaptable for use in MATLAB.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format