Experience Gained and Recommendations for Implementation of Process Bus in Protection, Automation and Control Systems

Introduction

The process bus provides a digital link between primary substation equipment, on one side, and protection, automation, and control devices, on the other side. It enables the reduction of copper wiring, improves safety, flexibility, and efficiency of operation and maintenance, resulting in significant interest in the development and implementation of digital substations using IEC 61850 process bus.

In recent years, an increasing number of publications reported the design or commissioning of demonstrators, pilot projects, pre-series or series of fully digital substation Protection, Automation and Control Systems (PACS) using IEC 61850 process bus. This constitutes a major development, as up to now PACS were mainly using only IEC 61850 station bus. The availability on the market of both Binary Input / output Intelligent Electronic Device (IED) (BIED), Stand Alone Merging Units (SAMU) and Low-Power Instrument Transformers (LPIT) sustains this trend.

The scope, goals and design of these projects vary widely. This includes the number of feeders, the number of different manufacturers involved and the use of LPIT and/or SAMU, with or without trip signal to the circuit breakers (real trip / monitoring only). Also, the estimated or reported economic benefits show a considerable variation depending on the considered use case and context.

In order to gain confidence and to enable a realistic technical and economic evaluation of these technologies, CIGRE Study Committee B5 (Power System Protection and Local Control) instigated in 2018 the formation of the Working Group B5.69 “Experience Gained and Recommendations for Implementation of Process Bus in Protection, Automation and Control Systems” to perform a review of PACS employing IEC 61850 based process bus. This review was to be based on available publications from demonstrators and pilot projects of PACS involving process bus.

This Technical Brochure reviews Protection, Automation, and Control Systems (PACS) employing IEC 61850-based process bus, using available publications from demonstrators and pilot projects, and a survey conducted within the industry between September 2020 and January 2021. The review focuses on projects using Sampled Values over the process bus and classifies them according to various criteria such as project type, process bus architecture, testing and maintenance, monitoring of high-voltage equipment, and economic evaluation.

Structure of the Technical Brochure

The Technical Brochure is organized in 12 chapters and 3 appendixes:

Chapter 1 provides an introduction to the development of the IEC 61850 standard and the process bus concept, highlighting their importance in the context of the ongoing transition towards a smarter grid.

Chapter 2 defines key terms and concepts related to digital substations and the process bus, providing a foundation for the subsequent chapters.

Chapter 3 provides a list of reference documents.

Chapter 4 reviews process bus based PACS projects, classifying them according to various criteria and providing detailed descriptions of selected projects. It also compares the advantages and drawbacks of different process bus architectures and discusses the classification of projects covered in the reviewed publications. Close to 200 publications (full list in Appendix B) and close to 60 projects (full list in Appendix C) were reviewed.

The figures 1 and 2 illustrate the analysis of the referenced publication and projects. Figure 1 shows the distribution of the analysed references according to the type of project. The overall coverage is quite homogenous for the different project...