Montana Dakota Utilities Co., Lewis & Clark Station Unit #1
Montana-Dakota Utilities Co.
35023 Highway 23 E
Sidney MT, 59270
The L&S Electric Advanced Excitation System (AES) redundant static excitation system was selected to replace the existing G.E. Amplidyne excitation system for the Montana-Dakota Utilities Co.’s Lewis and Clark plant’s Unit #1 synchronous generator. MDU choose the AES for its advanced control and monitoring features, their comfort in L&S Electric’s excitation engineering expertise, the L&S Electric provided 24/7 product support, the two (2) year warranty, the AES’s competitive price, L&S Electric’s ability to provide and manage turnkey projects, and the commercially available spare parts.
The Lewis and Clark plant’s synchronous generator has a rated output of 72 MVA at 13.8kV and has field requirements of 595 amperes, 250 volts at rated load and 0.98 power factor. The input power to the AES was provided from an excitation power transformer (EPT). The EPT’s ratings are 352kVA, 2400/320 volts AC, 3-phase, 60 hertz, delta-wye with ±2x2½% primary taps and one (1) RTD in the center winding for over-temperature protection.
The Lewis & Clark excitation system consisted of an LS-AES-FS-EXCR-DT-800R and included a redundant (hot stand by) control system, an 800 amp 1+1 redundant, full wave rectifier bridge assembly with redundant fan cooling, an AC input breaker, a crowbar with a linear field discharge resistor for over excitation protection, an AC filter, a DC filter, a holding resistor, AC field flashing, reversible field leads, Ethernet IP communications, and a 15-inch color touchscreen (OIT), all in a 3-door, climate controlled, NEMA 12 enclosure with forced ventilation.
Additionally, the L&S Electric turnkey project services included the design and supply of the AES excitation elementary diagrams, the wiring diagrams, the assembly diagrams, operation & maintenance manual, installation engineering, installation thru subcontracted labor, installation supervision services, and the AES commissioning and onsite AES training.
A model validation study was also performed as part of the project services. The in-house engineering services and onsite engineering services validated the exciter model based on the time constants, gains, dynamic response, and saturation values recorded during system commissioning. A model validation report was provided upon commissioning completion.
The unit was installed April 2018.