Innocent Kamwa, Barry Mather
In the last issue, the focus was on the grid health monitoring. Instead of assessing the grid health in retrospect, when it is often too late to fix the observed issues, we must strategically address the prerequisite conditions for a grid in the good health condition. Enabling a noble grid (versus a degraded network) primarily requires transmission and distribution (T&D) equipment with fully functional components that can operate robustly under all specified operating conditions while allowing the network to meet grid code requirements. In contrast to many industries, the lifetime of properly dimensioned T&D equipment is expected to last several decades—sometimes as long as 40 to 60 years. While we should be proud of this achievement, it is also a barrier to innovation. Once equipment is installed, there is no incentive to change it. Otherwise, the operator will have, in the substation backyard, stranded assets that can still meet the minimum service requirements. Most maintenance checks only confirm the excellent condition of the component and further deter the operator from replacing the old stuff with new technologies. For this reason, innovation in T&D assets has been incremental. We can see, in the countryside, electric poles installed 60 years before that have barely evolved and are still operational.
It seems that this familiar status quo is bound to change, finally. In the list of trending topics published by the IEEE Power & Energy Society (PES), we can, more often than before, see T&D asset modernization topics popping up. Indeed, the pervasive integration of renewable energy sources and inverter-based technologies, while having a positive impact on the environment, resulted in serious consequences for T&D equipment and networks in terms of design, planning, operation, and maintenance. While there has been extensive research in a few key areas, particularly the challenge of diminished inertia, the impact of inverter-based technologies on the legacy electrical equipment is less understood, and further research is needed, opening new opportunities for power engineers to modernize the assets without the risks of stranded assets.
For example, the influence of inverter-based grid resources on T&D switchgear has been recognized, and measures have been taken to set new standards, such as the IEEE 1547 Standard for Interconnection and Interoperability of Distributed Energy Resources With Associated Electric Power Systems Interfaces, that indirectly impact switchgear requirements under continuously changing stresses. Along the same lines, the Electric Machinery Committee of PES recently investigated the consequences of diverse grid code requirements on synchronous machine design and standards. Their report highlighted the often-conflicting goals between systems aspects for reliable electrical energy supply versus practical design considerations of synchronous generators from the manufacturing, lifecycle maintenance, and cost viewpoints.
To tell the truth, organizations responsible for ensuring a stable system with a high share of inverter-based resources are struggling to get online-only stabilizing T&D equipment. Their concerns were highlighted in a December 2022 North American Electric Reliability Corporation report on the disturbance in Odessa, TX, USA, and in the June 2022 position paper by the European association for the cooperation of transmission system operators for electricity on the stability management of the highly penetrated renewable grid. By contrast, the market is rushing frantically to install large amounts of inverter-based distributed energy resources (DERs) that are known to add higher harmonic currents to the grid, which may be problematic for interruption, even for lower short circuit duties, while expediting thermal and dielectric failure of switchgear and other equipment. For transformers, the question is whether the time-varying excitation due to reverse power flow injected by DERs from the secondary can accelerate their aging compared to high-side constant excitation in normal conditions. Some utilities are rightly concerned that solar photovoltaic reverse power-flow effects on transformer aging may not be sufficiently factored in the cost–benefit assessment of DERs as flexibility resources.
In This Issue
As “smart” as grids around the world have become in the preceding decades, transmission and distribution (T&D) systems are still realized in the physical domain and require large amounts of physical assets far beyond easily visible T&D lines. The efficient operation of these assets, including protecting them from harm, is of critical importance for the reliability of the grid. Additionally, new technologies continue to be developed, offering and increasing the number of options for solving new and future grid challenges. The theme of this issue is “T&D Equipment Technologies.” Multiple perspectives, from the development of new technologies, to maintenance strategies, to the protection of assets from natural hazards, are addressed in the five articles of this issue:
• T&D equipment requires maintenance and even replacement at times, and the maintenance practices often used by industry are explained. Equipment conditioning monitoring, to better predict the need for maintenance and presage equipment failure, is introduced via the presentation of recent research using new condition monitoring methods as well as machine learning.
• Static compensators (STATCOMs) have been in regular use to manage reactive power needs, particularly at the transmission level, for a long time. The concept of an “E-STATCOM,” incorporating short-term, fast-discharge energy storage on the dc bus of a STATCOM, is introduced. The capability of E-STATCOMs to address many grid stability challenges in multiple large operating areas is presented.
• The maintenance and planned replacement of large substation transformers, before or after failure, have long been a focus of power engineers due to the cost, potential disruption, and long transformer procure timeline. The increased difficulty of predicting transformer aging with the advent of distributed energy resources is introduced, and multiple strategies for managing power transformers as an asset are presented, including future recommendations.
• Since the advent of electric grids, the need for protecting these systems from lightning has been apparent. With a focus on distribution systems, which increasingly connect larger amounts of critical generation and load assets, methods to protect these systems from lightning damage are described. The critical parameters for selecting arresters are detailed, and multiple distribution-centric lightning protection considerations are covered.
• High-voltage direct current (HVdc) power systems are being implemented more often, and the voltage of these systems continues to push upward. Bushings for these systems, designed using an electric field adaptive grading method that takes advantage of the nonlinear composite material properties, are introduced. The concept of adaptive electric field grading is discussed, and results for prototype composite material-based HVdc bushings are shown.
The “In My View” column tops off the issue with an expert and practical view of T&D technologies. A summary is offered on the status of research and the direction for future efforts for multiple T&D technologies across the gamut, from HVdc systems to power quality.
—Barry Mather
These contrasting—if not conflicting—views demonstrate the necessity for a holistic approach for modernization of T&D assets, from the fundamental design principles to planning, operation, and maintenance in the framework of inverter-dominated power grids. The team of guest editors tasked for the present issue on T&D equipment has done a good job in this regard. They attracted contributors from reliability regulation institutions and equipment companies with, often, academicians in between as debate moderators.
The topics addressed include, on the design side, new nonlinear materials to reduce the failure rate of bushings, which account for some 37.8% of transformer failures with fire or explosion, according to a report by the Conference Internationale de Grands Reseaux Electriques. With the growing market of high-voltage direct current systems worldwide to integrate intermittent renewable resources from remote areas or integrate offshore wind, the time is indeed right to revisit the materials used in the bushings. It is shown that, compared with the temperature-dominated electric parameters of ordinary materials, ZnO microvaristor-based composites, responding to electric field intensity, can enable an electric field adaptive grading structure in bushings. Similarly, the development of wide-bandgap semiconductor materials has enabled power electronic modules for higher voltage, higher current, and lower losses. Though promising, these concepts are still far from mass production.
Taking the viewpoint of the reliability regulation entities into account, a team of multidisciplinary stakeholders proposes upgrading the static compensator that currently targets transient and voltage stability issues only to provide inertia and fast-frequency response reserves. The modified device, termed static compensators with energy storage (E-STATCOM), integrates supercapacitors in a way that makes it possible to confidently address the future systems stability needs, as stated, for instance, in the Canadian Provincial Grid Code Study, by retrofitting, in a cost-effective way, a well-known and mature flexible alternating current transmission systems (FACTS) device.
At the equipment level, our invited authors analyze, in depth, the impact of fast-changing DER power-flow patterns on substation transformer stresses. Based on transformer health-monitoring concepts, available instrumentation, loading calculations, and reverse power flow in transformer cores, recommendations are formulated to enhance transformer fleet management strategies. This special issue could not avoid a conversation on intelligent maintenance of T&D equipment, which is becoming ubiquitous, thanks to cheaper nonintrusive sensors and Internet-of-Things availability in digital substations. Readers will become familiarized in the article, with the notions of a heath index, a risk index, and remaining useful lifetime prediction, which constitutes a necessary step toward intelligent maintenance. The concepts are applied to vacuum circuit breakers, one of the most reliable types of T&D equipment out there, although the presentation remains general enough to apply to any conventional equipment. The last invited article, but not the least, is an overview of the challenges and opportunities in the lightning protection of electric power distribution systems. Specific topics discussed are the lightning protection of underground circuits, overhead circuits, system equipment, and lines of all configurations. The author also included an original historical perspective that will certainly captivate the imagination of readers of the “History” column of the magazine, which, to our great regret, is missing again in this issue.
In this issue’s “Book Review” column, Dr. Shayan Behzadirafi discusses Power Flow Control Solutions for a Modern Grid Using SMART Power Flow Controllers, first edition, from the IEEE Press series on power and energy systems, by Kalyan K. Sen and Mary Ling Sen. The book provides students and practicing engineers with a good understanding of power difficulties within congested power system networks and provides solutions to mitigate power-flow problems. The book gives a clear and straight-forward introduction to power-flow control in complex transmission systems, starting with basic electrical engineering concepts and theory. It explains why effective power-flow controllers should be viewed as simple impedance regulators. The book introduces the concept of a smart power-flow controller that is based on functional requirements and cost-effective solutions.
This year, there were about 1,000 nominations for elevation to Fellow throughout IEEE. Based on the famous rule stating that “the total number of IEEE Senior Members elevated to Fellow in any one year may not exceed one tenth of 1% of the total IEEE voting membership on record as of 31 December of the preceding year.” Only 319 nominations were deemed successful. We list the 33 IEEE Members of the 2023 class of IEEE Fellows who bear a professional relationship with PES. Eighteen are PES members evaluated by the PES Fellow Elevation Committee, and 15 are PES members evaluated by sister Fellow Elevation Committees. The new PES Fellows deserve our heartiest congratulations for their outstanding contributions to the advancement of science and technology.
As usual, we owe a world of thanks to the editors and authors of this issue for having triumphed over several hurdles to make this issue a success. Several revisions were necessary, and we would like to thank the contributors for their patience and constant collaboration. In the end, we believe that the present issue addresses, in a balanced way, the different facets of the equipment design, maintenance, protection, and operation in the context of current grid modernization efforts to deal with digital and energy transitions. The breadth and depth of the articles are remarkable, running from materials to lighting protection and smart asset management. This can only be beneficial to our readers’ understanding of this complex topic to help them make informed asset management decisions, with significant societal and economic consequences.
If you, our precious readers, want your voice to be listened to about the topics discussed in this issue or about any other topic in the scope of this magazine, please let me know at innocent.kamwa@gel.ulaval.ca. Your communication with me is always treated confidentially. We are committed to promoting a diversity of opinions on any subject from every part of the world, as long as the contribution is fact-based and peer-reviewed.
E. Agneholm et al., “Report on coordination of grid codes and generator standards: Consequences of diverse grid code requirements on synchronous machine design and standards,” IEEE Power Energy Soc., Piscataway, NJ, USA, Tech. Rep. PES-TR69, Nov. 2018. [Online] . Available: https://resourcecenter.ieee-pes.org/publications/technical-reports/PES_TR_11-18_0069.html
“2022 Odessa disturbance,” North Amer. Elect. Rel. Corp., Atlanta, GA, USA, Dec. 2022. [Online] . Available: https://www.nerc.com/comm/RSTC_Reliability_Guidelines/NERC_2022_Odessa_Disturbance_Report%20(1).pdf
“ENTSO-E position paper stability management in power electronics dominated systems: A prerequisite to the success of the energy transition,” ENTSO-E, Brussels, Belgium, Jun. 2022. [Online] . Available: https://eepublicdownloads.azureedge.net/clean-documents/Publications/Position%20papers%20and%20reports/220616_entso-e_pp_stability_management.pdf
“Canadian provincial grid code study,” GE Energy Consulting, Schenectady, NY, USA, 2021. [Online] . Available: https://weican.ca/docs/Canadian%20Provincial%20Grid%20Code%20Study%20-%20Final%20Public%20R2.pdf
Digital Object Identifier 10.1109/MPE.2022.3230997