Xuan Wu, Brian Johnson
Transmission and distribution (T&D) systems are evolving to meet the demands posed by an increasing number of utility-scale and distributed inverter-based renewable generation and energy storage installations. At the same time, T&D asset owners are faced with aging physical T&D infrastructure that is vulnerable to failures. While the combination of aging assets and increasing installation of inverter-based renewables presents challenges, it also presents opportunities to take advantage of new technologies and concepts to upgrade existing equipment, put in new equipment, and improve the operation and maintenance of T&D equipment.
With the backdrop of increasing inverter-based renewable installation and the industry’s focus on improving system reliability, this issue intends to bring the audience ideas about the lessons learned, best practices, and advances for various types of important T&D equipment, including substation transformers, circuit breakers, surge arresters, static synchronous compensators (STATCOMs), and high-voltage direct current (HVdc) bushings. Although this issue only covers a small portion of the entire set of T&D equipment categories, we hope to trigger the industry’s interest in this traditional area, allowing it to take advantage of new techniques to upgrade or more effectively maintain T&D equipment to better serve the electric system of the future.
One of the present key challenges to electric utilities in most countries with developed power networks is aging T&D equipment. Aging equipment is more vulnerable to failure and could create significant system disruptions. In addition, the integration of new renewable energy sources on all voltage levels leads to bidirectional power flows and increased variability in loading, which imposes additional risks to aging T&D equipment. Franck et al. explore whether the lifetime of T&D equipment could be prolonged in [A1]. The authors introduce the concepts of intelligent maintenance strategies and then discuss challenges and trends in T&D equipment condition monitoring, including automatic estimation of equipment health.
The second article [A2] introduces an upgraded STATCOM technology tailored to provide inertia and fast frequency response. This upgraded technology enables rapid injection or absorption of active power through the dynamic control of the stored energy in supercapacitors in addition to the functions provided by conventional STATCOMs. The introduction of energy storage allows this new flexible ac transmission system device to not only provide reactive power compensation but also compensate for temporary active power imbalances. We hope to see this new technology help the industry accelerate the transition to a clean energy future with an increasing number of inverter-based resources.
Unlike flexible ac transmission system devices (which are relatively new to the industry), substation transformers have been used in the power industry for more than a century. Transformers remain one of the most critical and expensive T&D assets that utilities around the world plan and operate. The third article [A3] discusses this important topic. The authors share insights on transformer operational issues, such as methods for calculating evolving transformer loading capabilities and assessing reverse power flow impacts due to the increasing penetration of distributed energy resources. The authors also share some interesting observations from a utility’s perspective on asset management strategies, including transformer health monitoring and spare transformer strategies.
Lightning protection for distribution equipment needs attention due to increasing expectations for higher quality voltage and power by distribution customers, especially those who own power electronic devices, such as distributed energy resource converters and electric vehicle chargers. As a result, the development of more lightning-resistant distribution systems is required. The fourth article [A4] provides an overview of the challenges and opportunities for solutions we now face in the lightning protection of electric distribution systems. The author discusses lightning protection for underground circuits, overhead circuits, and system equipment as well as for renewable energy plants.
HVdc systems are becoming increasingly popular as the need for transmitting large amounts of renewable energy from remote solar or wind installations to load centers pops up more often across the world. One of the key pieces of HVdc equipment is the HVdc bushing, which provides insulation between the energized jumper and the grounded equipment case. HVdc bushings always experience high electric fields in an environment with high load currents. The fifth article [A5] illustrates the theory of adaptive electric field grading in high-voltage equipment and presents an application of using nonlinear composites for solving electric field concentration problems.
Digital Object Identifier 10.1109/MPE.2022.3230996