Protection, Automation and Control Architectures with Functionality Independent of Hardware

Objectives of this Technical Brochure

The objective of this Technical Brochure was to investigate and propose new architectures which would allow the independence of software from hardware and to describe possible reference architectures for the PACS. The application of new concepts like FIH need to be supported by technologies, processes, tools, and standards. Therefore, the Working Group explored relevant technologies, applicable standards, life cycle aspects, and migration strategies. Beside the expected benefits, technical and business challenges had to be reviewed and potential gaps in standards had to be evaluated. The evolution of microprocessor based IEDs and their architectures had been analysed to understand the changes imposed by the new concepts.

Consequently, some key technologies and core approaches could be identified to enable FIH concepts. As an example, FIH concepts would require the use of standards to separate the process interface as much as possible from the application functions allowing their use on different hardware platforms. Present multifunctional IEDs are grouping the functions according to the application, e.g., distance protection functions or overcurrent protections functions. This is a first step to virtualize devices which could be expanded to a virtual IED, a main element of the FIH concept.

The possibility of this kind of virtualization is already provided by IEC 61850 and part of the data model and related engineering processes. Nevertheless, FIH concepts would require additional methodologies for design, engineering, testing, and maintenance along the life cycle. Some elements are already addressed in standardisation, but still some gaps need to be closed for an efficient implementation and operational use of FIH. Related recommendations have been gathered and shared with some standard bodies to influence their roadmaps.

During the last few years, the topic of virtualization - as a core element of the FIH concept - gained a lot of momentum in the industry. Several standardization bodies, study groups, and associations started to work on Centralized Protection and Control (CPC) Systems. In parallel, some projects have been launched to validate related concepts in cooperation between manufacturers and utilities. First results have been considered in this Technical Brochure.

As new technologies might challenge existing business aspects like relationships, responsibilities, (migration) strategies, as well as skills and knowledge management. On the other side, several benefits are expected like improved operational efficiency, lower life cycle cost, more flexibility, and higher sustainability.

Structure and Content of the Technical Brochure

This Technical Brochure proposes new PAC architectures with I/O (Input/Output), processing hardware and functionality separated for optimum life cycles and elaborates criteria and conditions to be able to use hardware independent software application for PAC functions.

Over the last years new solutions have been developed and related pilot projects have been launched. Two promising technical concepts and architectures have been elaborated in this TB. Beside a concept of an IED based solution using a standardized middleware, and a Centralized Protection and Control system applying server-based architectures are proposed to provide hardware independence.

Both architectures are leveraging from the hardware abstraction capabilities of IEC 61850. The application of IEC 61850 in the context of FIH is almost similar to current applications in digital substations.

Overall, the chapters of this Technical Brochure are:

Chapter 1 introduces FIH and the main drivers to apply new architectures for PACS and expected features and benefits like:

• Application based functions independent of hardware, and new PACS hardware platforms, which allows a function operational over the life cycle of primary equipment or beyond
• Flexible function re-allocation, including dynamic assignment of functions based on operational requirement
• Cost-efficient hardware redundancy independent of functional redundancy
• New approaches to redundancy (re-assignment of functions rather than hardware duplication on per function basis)
• PAC functions may become applications running on generic platforms
• PAC functions may reach higher maturity levels by being in operation for decades without being modified or changed because of hardware upgrade
• New options for allocating PAC applications (from multiple devices to a “station in a box”)
• New opportunities for remote engineering and management with reduced local workforce requirements, opening new business models for providing protection, automation, and control.

Chapter 2 explains existing architectures of PACS and, also describes the optimized architectures and new functionalities of PACS enabled by the improvements in the performance of microprocessor technologies over the last three decades. The benefits of each new generation of PACS starting from conventional control panels to digital substations using process bus communications are explained. This evolution goes along with the introduction of IEC 61850 as communication protocol and core data model for PACS replacing various traditional protocols worldwide allowing new communication architectures, services, and applications. Starting from a short overview about IEC 61850 main concepts, the reader will gain a comprehensive understanding of the reasoning for the IEC 61850 to be a key element to support the transition from packaged hardware and software towards an application functionality implementation independent of hardware. Furthermore, the application of process bus allows more flexibility regarding the allocation of functions requesting at the same time new solutions like redundant communication to keep the high level of reliability for PACS. The chapter closes with an overview about the communication between substations and control centers.

Chapter 3 describes microprocessor based IEDs and their main characteristics of hardware and software and how each of the generations are different from each other. The retrospective of the IED technologies allows the reader to understand the dependencies between hardware and software and the evolution of the algorithms. A specific focus is given to the properties of the analogue data acquisition chain and the related processing of the digitized information. Furthermore, the improvements in microprocessor performances helped to implement new communication technologies supporting new protocols as a key enabler of distributed functions.

Chapter 4 introduces the requirements and limitations related to the concept of FIH based on used cases like free allocation of functions, exchange of hardware, aspects of granularity of hardware and software among others. To enable free allocation of functions, a distributed software architecture is required. IEC 61850 would help to aggregate functions in virtual devices based on standardized data models and communication protocols. Additionally, a higher level of interoperability towards interchangeability seems to be achievable under certain conditions. The free allocation of functions and the capability to host them on different hardware platforms is leading to new requirements to express the granularity and performance of such solutions. These requirements can be split into aspects related to hardware abstraction, process interface, time synchronization, interoperability, and performance benchmarking and testing along the life cycle. Existing product safety and electromagnetic compatibility guidelines need to be considered for newer FIH platforms. Derived from specific use cases like outdoor installations, substation level protection, automation, and control schemes, and WAMPAC applications requirements are also included in the chapter.

Chapter 5 details two different concepts for FIH - applying common approaches for FIH like decoupling and separation principles as well as data modelling and abstraction technologies. Derived from them IED architectures based on middleware (Figure 1) and server-based architectures (Figure 2) are introduced. Different applications and related internal architectures of IEDs following FIH concepts are presented. Server-based architectures are very much dedicated to support Centralized Protection and Control Systems and the focus is given to real-time virtualization technologies and related open-source projects.

Chapter 6 allows the reader to understand necessary enhancements of tools supporting design, engineering, testing, and maintenance in the context of FIH. Different phases of the life cycle and how standardized processes defined by IEC 61850 and related tools are supporting them are discussed. A specific focus is given to the (system) management during the operational phase based on practical situations like upgrading or adding functions. Furthermore, potential benefits compared to existing maintenance strategies are described. The implementation of FIH will cause some enhancements to existing test strategies allowing at the same time optimizations.

Chapter 7 explains FIH related system reference architectures from digital substation with process bus to a Centralized Protection and Control System (Figure 2) and provides a detailed comparison of them. Ten different criteria from number of devices up to cost aspects have been defined and the system reference architectures are ranked accordingly. The reader would be able to use these criteria to select the most appropriate solution for a given application.

Chapter 8 focusses on technical and business challenges linked to the introduction of FIH concepts. Technical Challenges related to test and maintenance processes, cyber and physical security performances or migration strategies are addressed. Business aspects like responsibilities of stakeholders, knowledge and skill management, business relationships, life cycle aspects, or the management of field-issues are discussed.

Chapter 9 provides a landscape about ongoing and existing standardization work as well as related study groups. The analysis of these activities provides recommendations for future work which are partially considered in new work approaches by different organizations.

Conclusion

This Technical Brochure summarizes various aspects of the concept of PACS independent from hardware and proposed two directions for embedded and server-based implementations. Moving from a hardware driven approach to software solutions will require several changes beside the technical strategies. Specification, purchasing, engineering and design processes, logistics, testing, operations, and maintenance – the entire life cycle will be influenced by moving to a software-centric PACS. The main findings and recommendations are:

• Any kind of PACS with functions independent of hardware will require a well-defined separation of physical interfaces to the process from the higher-level application functions based on standards providing interoperability, flexibility and long life cycle support
• Applicable standards should not cover just the communication aspect, but as well the data model and the engineering processes. To reduce risks during the development and project execution phases, the implementation of conformance testing is highly beneficial. Therefore, PACS with FIH should be based on IEC 61850 as this standard series and ecosystem will cover most of the requirements for designs providing independence of hardware
• Along with flexibility, the number of possible architectures and solutions may increase. To manage efficiency of the engineering process and ensuring the performance of the entire systems, the current concepts of specification, engineering and testing need to be enhanced. Steps have already been taken in the standardization and research to cover these aspects like isolation of functions during test or virtual IED implementation. It is recommended that study groups start to address performance benchmarking principles to prepare recommended engineering practices or even propose a standard for this critical purpose
• A replacement of current and well experienced PACS will only be possible if economic, reliability and operational aspects of a new solution brings substantial benefits. Based on the proposed architectures the evaluation of the benefits needs to analyse all life cycle phases
• The application of IT concepts to virtualize protection functions as virtual IEDs on servers is considered as promising future direction enabling several benefits like easier integration and life cycle management of software packages, seamless cyber security, functional digital twin, capability to use cloud-based testing among others
• Existing open source based real-time operating systems have been tested in pilot projects and are providing a high level of stability, performance and reliability and may be used to define vendor independent virtualization frameworks
• While most of the technical challenges have been considered already, some specific areas need to be targeted by further standardization work. This technical brochure will be used by standards bodies like IEC and IEEE to evaluate potential gaps and will define roadmaps to cover them
• Some technical approaches may be considered for new study groups like influence of architectures on primary equipment design, improved energy efficiency in substations or digital twin use cases.
• Further study groups should address business related topics like cost effectiveness, knowledge management and optimized life cycle management.