The landscape of electricity distribution in the United States is rapidly evolving, driven by population growth, increasing electrification, and the pressing need for grid modernization. Utilities are in a constant quest for innovative ways to design, engineer, and construct substations and transformer equipment. Among the solutions emerging from this drive for innovation is the concept of Voltage Regulating Distribution Transformers (VRDTs), a transformative application for voltage-regulated distribution transformers, writes Tu Anh Tran with her co-authors Jose Mitra, Patrick Wright, and  James Chaggaris for our August edition of the Power Systems Technology / Transformers Technology Magazine.

Traditionally, voltage regulation in distribution transformers was achieved through off-circuit tap changers, allowing for adjustments in distinct steps when the transformer was de-energized. VRDTs, on the other hand, represent a new breed of distribution transformers equipped with on-load tap changers. These on-load tap changers enable stable voltage output even under varying loads, ensuring that the voltage remains within ±5% of the nominal voltage as required by ANSI C84 standards.

One of the remarkable advantages of VRDTs is their ability to decouple the medium voltage (MV) from the low voltage (LV) grid, a game-changing feature for grid stability. In conventional distribution transformers, voltage on the primary side directly affects the voltage on the secondary side, which can lead to voltage fluctuations as demand varies along the distribution line. VRDTs break this link, ensuring that changes in primary voltage do not impact the stable secondary voltage, providing consistent power to end-users.

ComEd, the largest electric utility in Illinois, is a prime example of how VRDTs are making a significant impact on grid infrastructure. ComEd's Substation-in-a-Box project, initiated in 2005, marked the inception of this innovative approach. By integrating VRDTs, specifically the ECOTAP® VPD® by Maschinenfabrik Reinhausen, ComEd transformed traditional distribution center substations into compact, cost-effective solutions.

The latest generation of this Substation-in-a-Box project showcases the advancements in VRDT technology. Featuring the ECOTAP® VPD®, this next-gen DCIAB has replaced individual voltage regulators, significantly reducing the substation's footprint. Notably, it operates with a regulating range of ±10% and ensures that voltage remains within prescribed limits, benefiting end-users in rural areas like Tonica, Illinois.

VRDTs, with their compact design and decoupling capabilities, are proving to be a cost-effective solution for utilities looking to modernize their distribution grids. As electrification and regulatory pressures continue to reshape the energy landscape, VRDTs are becoming a vital tool in ensuring grid stability and reliability while meeting the growing energy demands of the future.

In conclusion, the emergence of Voltage Regulating Distribution Transformers represents a significant step forward in the quest to modernize US grid infrastructure. With the ability to stabilize voltage, decouple grids, and reduce costs, VRDTs are poised to play a pivotal role in the evolving energy landscape.

Read the full article in the latest edition of the Power Systems Technology / Transformers Technology magazine.