A hydroelectric station that began operating in 1903 remains a remarkable example of early twentieth century engineering. Despite its age, most of the original equipment continues to function, and a recent breaker modernization shows how carefully planned upgrades can preserve long standing infrastructure.
Construction of the Bulls Bridge Hydroelectric Plant in New Milford, Connecticut, started in 1902. When it entered service the next year, it became the first commercially successful hydroelectric facility on the Housatonic River. Nearly 125 years later, it still operates as a run of river installation using its original turbines, penstocks, and canal.
Operating at full output, the plant generates roughly 8.2 to 8.4 MW with a discharge capacity of about 1,200 cubic feet per second. Its annual production reaches around 30.8 GWh, placing it among the top hydroelectric generators in Connecticut.
Historic Machinery Still in Service
Bulls Bridge remains distinctive for its continued use of original components. The powerhouse relies on six horizontal double runner Model F 1 Francis turbine units installed in 1903, each connected to General Electric generators. Water from a two mile canal flows through 420 foot penstocks and drops approximately 105 feet to drive the turbine generator systems.
Breaker Systems in Need of Updating
While the turbines and generators continued to perform reliably, the downstream circuit breakers required attention. These breakers protect generators, allow isolation for maintenance, and ensure proper connection to the grid. Early designs such as oil and air magnetic breakers can degrade over time due to contact wear and insulation aging. They also fall short of modern safety expectations.
As a result, the original breakers were replaced with modern vacuum circuit breakers. Vacuum interrupters extinguish arcs within sealed chambers, offering improved reliability and minimal maintenance compared to older technologies. Updating the breakers also brought the plant into compliance with current electrical standards and interconnection requirements.
Retrofitting with Modern Vacuum Breakers
National Breaker Services (NBS) was engaged to replace all six breakers with draw out style vacuum units. The company, based in Middlebury, Connecticut, specializes in designing and retrofitting medium voltage switchgear suited for older infrastructure. Its Citadel platform allows utilities to modernize legacy systems while maintaining or improving original performance ratings.
The Citadel system began as a retrofit platform for fixed mounted vacuum breaker elements and has evolved into a draw out design offering remote racking and roll in replacement. The units support voltage ratings up to 38 kV and current capacities up to 5,000 A.
For Bulls Bridge, NBS engineered custom enclosures to accommodate the tight footprint of the original installation, which had been built without modern metal clad housing. The team removed the old breakers and installed the new assemblies over a two week period. The new enclosures also include draw out potential transformer modules, a capability not present in the original 1903 equipment.
National Push to Upgrade Aging Hydropower Facilities
Across the United States, more than 90,000 dams exist, yet only a small fraction are used to generate electricity. Many hydro facilities are more than 50 years old and require upgrades to remain productive. As electricity demand increases, maintaining and improving existing hydropower assets is seen as an important clean energy strategy.
A coalition known as the Uncommon Dialogue project, supported by Stanford University, brings together groups focused on both hydropower development and river restoration. The initiative aims to find balanced approaches that support clean energy goals while addressing environmental concerns. Its work contributed to the inclusion of significant hydropower funding in federal infrastructure legislation.
Preserving the Value of Legacy Infrastructure
The modernization effort at Bulls Bridge demonstrates how targeted upgrades can extend the life of historic power facilities. With the installation of Citadel breakers, the plant improves safety and reliability while preserving the core machinery that has operated for more than a century. This approach provides a model for other aging hydro and fossil fuel plants seeking to maintain service without full system replacements.