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Modernizing Protective Relays: How One Utility Made the Switch

Drake_Power_Plant.jpgA May 2014 fire knocked out the Martin Drake Power Plant of Colorado Springs Utilities (CSU). The fire damaged all three coal-fired units, quickly disabling the entire 254 MW facility. The plant provided a third of the utility’s production, and to avoid power shortages and higher rates associated with buying power on the open market or by building a greenfield plant, CSU decided to repair the three units as quickly as possible.

The nerve center of the plant’s electrical system, the relay room, was severely damaged. This room contained the relays responsible for protecting critical plant equipment, including the main generators. The existing relays used older electromechanical technology, so the restoration presented an opportunity to modernize the system with microprocessor-based numerical devices, bringing benefits of the digital age into the power plant.

It’s a question many owners with older relays ponder on a continuous basis. The replacements would require engineering and redocumenting the plant’s systems. The staff would have to be trained on the new technology.

Although the relays and associated switch gear represented only about 10% of the project cost, there was a business analysis involved. Old relays are not being manufactured today, so used or older equipment would need to be found. Also, insurance coverage would pay for a restoration to the original condition, but not for new equipment.

CSU had planned to install new relays and had enough of the new ones to restart Unit 6, but they were eight years old and had to be sent back to the manufacturer for retesting. After considering the alternatives, the utility chose safety, improved plant control and efficiency and lower maintenance over a small additional cost and went with the new relays.

For CSU, speed was of the essence, as added time would result in higher costs. Relays aren’t bolted on, however. It would take careful engineering and documentation to realize their benefits.

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