Technical evaluation of the proposed design modifications and technical specification changes on grid voltage degradation (Part A) for the Rancho Seco Nuclear Generating Plant

Technical Report · Wed Oct 01 00:00:00 EDT 1980

DOI:https://doi.org/10.2172/6830844· OSTI ID:6830844

White, R L

The Rancho Seco Nuclear Generating Plant has two 4160-volt and two 480-volt Class 1E buses. The existing undervoltage protection design uses a single undervoltage relay on each 4160-volt Class 1E bus. If the voltage drops below 3534 volts (85% of 4160 volts), the undervoltage relay will energize a set of load-shedding relays. The load-shedding relays initiate the disconnection of the emergency 4160-volt buses from the off-site source, load shed the emergency 4160-volt buses, start the emergency diesel generators, and provide an enabling signal for the load-sequencing timing circuit. When the emergency diesel generator reaches the required voltage it is connected to the emergency buses and load-sequencing will begin automatically, if a safety injection (SI) signal exists. The licensee has proposed a design change to establish an automatic degraded voltage protection circuitry. The modification consists of incorporating the existing undervoltage protection scheme will consist of 3 undervoltage relays monitoring each 4160-volt emergency bus. The 3 undervoltage relays will be arranged in a 2-out-of-3 coincident logic with a setpoint of 3771 volts +- 38 volts (90.6% of 4160 volts) with a time delay of 12 seconds +- 1.2 seconds.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6830844
• Report Number(s): UCID-18690; TRN: 81-000103
• Country of Publication: United States
• Language: English

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