T-Type Modular DC Circuit Breaker (T-Breaker) for Future DC Networks

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Columbus, Ohio
Project Term:
09/25/2019 - 03/24/2023

Critical Need:

Today’s power grid relies primarily on alternating-current (AC) electricity as opposed to direct-current (DC). DC has advantages over AC such as lower distribution losses, higher power carrying capacity, and reduced conductor materials, which make it well suited to industrial applications, transportation, and energy production. However, the risk associated with electrical faults, such as short circuits, and system overloads, continues to hinder the growth of DC markets. Inherently, AC electricity periodically alternates direction, providing a brief “zero crossing,” where no current flows. This characteristic allows electrical faults to be interrupted by conventional electro-mechanical breakers. DC networks deliver power without zero crossings, which make conventional circuit breakers ineffectual in fault scenarios. To fully benefit from medium voltage (MV) DC usage, fast, highly reliable, scalable breakers must be developed for commercial deployment.

Project Innovation + Advantages:

The Ohio State University (OSU) team will develop a MVDC circuit breaker prototype based on its novel “T-breaker” topology. OSU will leverage its unique high voltage and real-time simulation facilities, circuit prototyping experience with MV silicon carbide devices, and capability in developing protection strategies for faults in DC networks. The result will be a circuit breaker with reduced cost and weight, simplified manufacturing, and increased reliability, functionality, efficiency, and power density. The self-sustaining modular structure will allow for inherent scalability while integrating ancillary circuit functions, enabling superior electrical grid stability. This attribute will open markets for the T-Breaker in higher voltage grid applications and address the shortcomings of using a circuit breaker in the growing MVDC application space.

Potential Impact:

The proposed breaker is installed close to loads to rapidly detect and react to the short-circuit fault. Thus, it could enable an increased number of electronic loads that operate using DC, such as ultra-fast electric vehicle charging stations and utility scale energy storage battery units, to connect to the MV distribution grid. This would improve overall power delivery efficiency.


DC circuit breakers respond significantly faster than their AC counterparts, enabling prompt isolation and protection of assets from electrical faults. MVDC circuit breakers and grids enable greater resiliency to cyber and other attacks through targeted isolation of affected nodes.


MVDC breaker-enabled microgrids could facilitate greater deployment and adoption of distributed renewable resources, greatly reducing power sector emissions. Electrification of transportation (e.g., ships, aviation) with DC systems would also reduce emissions.


Proliferation of MVDC systems protected by more effective DC circuit breakers could drive higher energy efficiency, lower equipment costs, and bolster grid resiliency.


ARPA-E Program Director:
Dr. Isik Kizilyalli
Project Contact:
Jin Wang
Press and General Inquiries Email:
Project Contact Email:


United Technologies Research Center

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