Energy Transition in Rural America (Spring 2022) - Dickinson Converter Station, Great River Energy
By Joshua Anderson and Eric Barry
As the long winter turned to spring, our class visited Buffalo, Minnesota, home of Great River Energy’s (GRE’s) Dickinson Converter Station. In the wake of the pandemic we were fortunate to be the first group to tour the facility in over two years. Our serendipitous visit coincided with another rare event: planned maintenance. In an industry where reliability of service is paramount, planned maintenance must be carefully scheduled and efficiently completed. While under maintenance, some of the equipment was de-energized, allowing us a closer look. Lucky us!
One of only a few in the U.S., the converter station marks one end of a high-voltage direct current (HVDC) transmission line called “CU” (named after its original owners and GRE’s predecessor organizations, Cooperative Power Authority and United Power Authority). A nearly identical facility is located on the other end of the line at Coal Creek Station, a coal power plant in McLean County. The CU transmission project was built in the 1970’s, is 438 miles long, and transmits approximately 1,100MW of power. While the line is a very valuable asset today, its construction was filled with conflict, policy hurdles, and local revolts. Nonetheless, it is infrastructure like the CU line and the Dickinson Converter Station that provide resilience to our electrical grid, and more is required to expand as the energy industry transitions to more renewable, variable, and distributed sources of power generation.
HVDC lines transport power efficiently over long distances. However, while the high voltage decreases energy loss during transmission, direct current is incompatible with the distribution grid that connects homes and businesses to the electrical grid. Hence the need for facilities like the Dickinson Converter Station. At this facility, the large amounts of direct current power are transformed into alternating current and sent out along various lower-voltage transmission lines.
Owned by GRE, the HVDC line and converter stations are being sold to Rainbow Energy as soon as May 2022. While some things will change as a result, GRE will continue to operate and maintain the facility. And the converter managers Greg Schutte and Tony Geldert were clear that the priority for their teams and the station will remain the same: provide safe and reliable electricity to the residents of Minnesota.
Great River Energy (GRE) is Minnesota’s largest generation and transmission cooperative, consisting of 28 member cooperatives. The converter station lies within the service territory of one of their member co-ops, Wright-Hennepin Cooperative Electric Association.
The Control Room – Red is good, and green is bad
Upon arrival, our student cohort of Humphrey graduate students and professor Gabriel Chan signed into the main entrance of the facility—a process that was carefully done and required proof of government identification. The Dickinson station is a high-priority energy asset, not just for North Dakota and Minnesota, but for the United States. We were then ushered in by GRE managers to the control room. We walked past a wide display of monitors (the function of which is to keep tabs on equipment in the facility) and gathered in a central area of the control room. We were surrounded on all sides by server farm-like arrangements of computers adorned by bright red signs with the message, “WARNING: Equipment is Operational.” Facility operators were keen to point out that on this equipment, a red light indicates that it is working properly, and a green light indicates a problem. As if we needed the equipment to be harder to understand, at the converter station “Red is good, green is bad.”
Tony Geldert, the supervisor of the converter station, was only half-joking when he told our group that leaning on the computers and/or accidentally messing with any of the computer switches could cause major electricity delivery disruptions for the Twin Cities. We even split into smaller groups for the tour of the facility to ensure that we wouldn’t bump into any valuable equipment. Such reminders reflect the high stakes that surround the reliability and resilience of our electric grid.
The Valve Hall – Where the magic happens
Greg Schutte, manager of field services at GRE, provided an opening presentation about the history and policy implications of this unique piece of transmission infrastructure. We were then lucky enough to take a tour of the part of the facility temporarily shut down for maintenance. The facility is essentially bisected into two identical sections—the equipment we observed was the same equipment operational on the opposite side of the building. Part of the tour included the fire safety and climate control equipment (e.g., HVAC, humidifiers) located in the basement of the station. In fact, the facility’s basement is unique in its layout compared to most other transmission facilities that are generally built at ground level. This presents somewhat of a challenge to the GRE team tasked with climate control and keeping the facility within spec, since it is situated near swampy terrain.
Entering the valve hall, in its sci-fi like grandeur, was like stepping into a NASA testing facility. Oversized electrical equipment towered over our tour group leaving us quietly amazed. Large columns of conversion equipment were filled with thousands of thyristors, the small silicone semiconductor pucks responsible for the conversion of the DC input into AC output. Keeping this equipment running safely and efficiently is an involved task that included numerous systems: a waterless fire control system that evacuates air and suffocates fire, filters and machines to keep dust and humidity out of the air, leak detection wires on the floor, fiber lines leading to each thyristor, faraday cages over windows, a battery backup system, and even a 5th harmonic filter to reduce noise pollution.
2019 Upgrade – From 8-tracks to iPhones
Much of the tour focused on a system-wide upgrade in 2019—an expensive, but necessary decision made by the 28 co-op members of GRE. Over the course of 74 days, the upgrades were completed to reduce instances of equipment failure and outages. These changes increased reliability by implementing a number of technical advancements into the station’s infrastructure. Notably, the upgrades were completed without a single outage in service, a testament to the careful planning and herculean effort undertaken by GRE. During the upgrade, the valve hall’s air-cooled system was swapped with one cooled by water. As Tony put it, the older air-cooled system can be equated to listening to music on an 8-track tape, while the new water-cooled design is more akin to listening to music on your iPhone. This facility was state-of-the-art, and GRE was the proud operator.
