Electromagnetic Compatibility Issues in Modern and Future Power Systems

Introduction

This Technical Brochure addresses the Electromagnetic Compatibility (EMC) issues that are arising in modern power systems and are expected to persist in future power systems.

Technological changes are being introduced into modern power systems to facilitate the transition to a clean energy future and to enable more flexible power networks. However, these technological changes have introduced new electromagnetic compatibility problems in these systems and have also exacerbated some existing problems. In fact, they have created and/or amplified some interference problems both intra-system and inter-system, between power systems and other man-made systems, as well as between power systems and the natural electromagnetic environment.

The main features of modern electric power systems that give rise to these EMC issues, in contrast to traditional systems, include:

• Transmission lines with higher voltages and currents, and lower resistance.
• Greater spatial extent and the use of large size high-voltage equipment, often containing numerous power electronics components.
• Switching surges with very short front times, generated by the operation of Gas-Insulated Switchgear.
• Increased importance of non-linearity from power electronics interfaces between parts of the system operating at different frequencies.
• Bidirectional active power flows, due to distributed generation and loads with power electronics interfaces.
• Faster, but more electromagnetically susceptible, control and monitoring processes.

The emergence of these new EMC issues have created the need for a more detailed understanding of the increasingly complex interactions between the different components of power systems and highlighted the limitations of current models used to describe the system behaviour, which are based on circuit theory.

To gain this deeper understanding of the interactions between the different components and explain the nature of EMC issues, as power systems are electromagnetic systems, it is necessary to adopt an electromagnetic field perspective. However, a full electromagnetic view is often too complex for practical engineering. Consequently, what is needed is an engineering simplification of the full electromagnetic view that goes beyond the traditionally used circuit theory.

Scope/Methodology

As emerging EMC problems reveal the limitations of simplified models, this Technical Brochure presents CIGRE power systems engineers with EMC concepts. While still an engineering simplification of the full electromagnetic view, these concepts are more comprehensive than the circuit theory. 

Circuit theory relies on integral field quantities like voltage and current, which can be treated as signals. EMC concepts build on that by also including field quantities as signals, which are the values of some electromagnetic fields at specific locations in space (the ports of susceptible devices). Furthermore, to enable comparison of the intensity of electromagnetic disturbances with the immunity of devices to them, a key simplifying concept is introduced: the "level of electromagnetic disturbance," which defines the level of a specific disturbance at a given location, resulting from all contributing sources.

Therefore, as a result of the technological changes introduced into modern power systems, the following fundamental EMC issues in power systems are emerging or being exacerbated:

1. The emergence of new types of electromagnetic disturbance waveforms and some existing ones are being exacerbated, representing the evolving electromagnetic environment of power systems.
2. The need to determine the correct method for aggregating disturbances from all contributing sources for determining the probability density of the disturbance level at the location of interest, or at least, to accurately estimate the maximum disturbance level.
3. The need to determine the immunity limits of devices in the presence of these new or exacerbated types of disturbances.

Description of the TB

This Technical Brochure presents the problems of intra-system interference in modern power systems and the problems of inter-system interference between power systems and both the natural electromagnetic environment and other man-made systems. Rather than providing an exhaustive bibliographical review, it attempts to present the stage of development of the understanding of each of these problems, as well as the relevant suppression techniques and standards. 

This Technical Brochure is structured as follows:

• Chapters 1-3 outline the scope of the document and define key terms by referencing them to the International Electrotechnical Vocabulary. They cover the introduction, definitions, and the fundamental EMC problem.
• Chapter 4 presents the problems of intra-system interference in a modern power system.
• Chapter 5 presents the problems of inter-system interference between power systems and the natural electromagnetic environment.
• Chapter 6 presents the problems of inter-system interference between the power systems and other man-made systems, using communication systems as an example; and
• Chapter 7 provides a brief overview of the nature of EMC problems and lists the main EMC problems arising in modern and future energy systems, as well as key conclusions about the current stage of their resolution.

Conclusions

The main conclusions reached during the preparation of this Technical Brochure on the fundamental EMC issues in power systems that are emerging or being exacerbated, and which are currently only partially resolved and require further development, are:

• Field measurements reveal that switching operations in gas-insulated substations and the normal operation of power electronics equipment produce disturbance waveforms that differ significantly from the standard waveforms used for immunity testing.
• The challenge of correctly aggregating the electromagnetic disturbances from all contributing sources to adequately estimate the potential maximum disturbance level, considering the effects of nonlinearity, is not yet satisfactorily resolved, even for harmonic studies.
• There is limited data on immunity limits of devices, equipment, and their insulating materials, in the presence of these new types of electromagnetic disturbance waveforms.

This document is intended for all power systems engineers seeking a more detailed understanding of the increasingly complex interactions between the various components of modern power systems and aims to raise awareness of EMC issues that are exacerbated by the new characteristics of these systems. These is achieved by explaining an engineering simplification of the full electromagnetic view, known as EMC, which is more comprehensive than circuit theory because it also includes signals originating directly from electromagnetic field quantities.