Hitachi Energy and high-voltage interregional infrastructure developer Grid United have launched the next phase of a collaboration to strengthen transmission capacity between three energy markets straddling the Eastern and Western grids in the U.S., formalizing an agreement for the North Plains Connector (NPC), a ±525 kV, 3-GW high-voltage direct-current (HVDC) line spanning roughly 420 miles between Montana and North Dakota.
The Engineering Services Agreement (ESA), announced Oct. 2, 2025, tasks Hitachi Energy with delivering early-stage engineering services—including technical specifications for two HVDC converter stations, covering electrical ratings, valve hall layouts, control-system architecture, and harmonic mitigation studies. It also includes dynamic and steady-state system modeling and AC–DC interface definitions for integration with Midcontinent Independent System Operator (MISO), Southwest Power Pool (SPP), and Western Electricity Coordinating Council (WECC).
Grid United will advance corridor refinement, land-rights acquisition, stakeholder engagement, environmental permitting support, and supply-chain sequencing for long-lead items such as transformers, smoothing reactors, and converter valves. Procurement timelines will be aligned with the project’s permitting and construction schedule.
The project marks a significant advance for Hitachi Energy’s ambitions to bridge the Eastern and Western electrical interconnections, which federal studies have long identified as one of the nation’s most consequential grid vulnerabilities. The U.S. Department of Energy’s (DOE’s) October 2024 National Transmission Planning (NTP) Study found that “significantly more transmission needs to be built in the U.S.—roughly two to three times the current transmission system—to meet future demand growth, reliability requirements, and achieve existing and potential future public policy goals.” That expansion, the study said, would “enhance grid reliability as it allows more resources to be shared across regions and energy to be moved from where it is available to where it is needed,” particularly during “large-scale extreme weather events.”
A crucial structural gap, according to a January 2025 study from the Pacific Northwest National Laboratory (PNNL), stems from the grid’s topology: the U.S. lacks coordinated interregional transmission planning and physical transfer capacity between its major electrical interconnections. The report found “a lack of comprehensive, multi-value interregional transmission planning processes… and no planning organization or authority responsible for interregional transmission planning.” It also concludes that “improving interregional transmission can enhance grid reliability as it allows more resources to be shared across regions and energy to be moved from where it is available to where it is needed.” That isolation, the authors caution, heightens system congestion, curtails low-cost renewable power in the Plains and Interior West, and undermines resilience “during large-scale extreme weather events,” when the ability to shift power between regions could avert outages and lower costs.
According to Hitachi Energy and Grid United, the NPC is designed to address that deficiency. The ±525-kV HVDC system will link eastern Montana and western North Dakota to create a controllable, bidirectional bridge between the WECC, MISO, and SPP to transport up to 3 GW in either direction between the eastern and western U.S. “NPC will help address fast-growing electricity demand driven by AI data centers and industrial electrification. It will play a key role in enabling the sharing of power between grids serving different parts of the country,” the companies said on Thursday.
The ESA builds on the companies’ first landmark announcement about the concept in March 2024. That announcement outlined a plan for Hitachi Energy to provide HVDC technology across multiple Grid United transmission projects. The companies framed the effort as a way to “dramatically boost transmission capacity across the U.S. to support the urgent need for smooth sharing of power between energy markets at a time of drastically increasing demand for electricity,” while “help[ing] overcome one of the most persistent bottlenecks in the energy transition in the U.S. by bridging the east–west divide.”
That 2024 collaboration, notably, also introduced a novel capacity reservation framework that allows Hitachi Energy to pre-allocate manufacturing capacity and streamline delivery across successive HVDC projects. Hitachi has said the mechanism echoes a business model the company had previously applied with European utilities to accelerate transmission build-out. Hitachi Energy executives characterized the approach as a supply chain innovation designed to “enable speed and scale in the supply chain” and “make important contributions to streamlining the development process to help accelerate the energy transition.”
On Thursday, company officials hailed the historic nature of the project. “North Plains Connector will be the first transmission system connecting three major U.S. energy markets, supporting a key goal of the U.S. Department of Energy for interregional transmission connections to enhance grid reliability and resilience,” said Allie Wahrenberger, vice president of Engineering for Grid United. “We are excited to be moving forward with world-class engineering from Hitachi Energy, a company committed to our shared goal of improving grid reliability and resilience for millions of Americans.”
“This new agreement with Grid United is a perfect example of how a long-term collaboration built on trust and a shared vision can accelerate the project and mitigate risk,” said Nathanael Occenad, Vice President, Regional HVDC Sales Manager for the Americas of Hitachi Energy. “We are proud to support Grid United to advance this project, which is so critical to the expansion of the U.S. grid in the face of skyrocketing electricity demand.”
—Sonal Patel is a POWER senior editor (@sonalcpatel, @POWERmagazine).
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