Nuclear Power Plant Emergency AC Electrical Systems



Electrical Systems

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Function

There are two (2) main function of electrical systems in a power plant:

• distribute the electrical power from the power supply to the components

• provide electrical protection for the power source and also for the components supplied.

Major Components

In nuclear plants there are several levels of electrical power distribution (other than from the generator to the generator transformer):

• High Voltage (e.g. 4160, 6900, or 13,800 Volts AC, may also be abbreviated VAC)

• Medium Voltage (e.g. 480 VAC)

• Low Voltage (e.g. 120, 240 VAC, 260 VAC)

High voltage systems are used to supply equipment that have motors with high horsepower ratings. Examples of these are:

• Feedwater pumps

• Recirculating or Reactor Coolant Pumps

• Circulating Water Pumps

• Condensate Pumps

• Cooling Tower Pumps and Fans

• High Pressure Emergency Makeup Pumps

• Containment Spray Pumps

Medium voltage systems are used to supply equipment that have motors with moderate horsepower ratings. Examples of these are:

• Auxiliary or Emergency Feedwater pumps

• Heating Ventilating Air Conditioning (HVAC) Fans and Chiller Units

• Control Rod Drive Motor-Generator Sets

• Motor operated valves

Low voltage systems are used to supply equipment that have motors with low horsepower ratings. Examples of these are:

• Lights

• Small pumps

The following photo illustrates electrical switchgear (distribution panels) as may be found in a nuclear plant.

|[pic] |Electrical Switchgear |

| |This photo shows electrical switchgear |

| |(distribution panels) as may be found in a |

| |nuclear plant. |

| |Detailed description.  |

|[pic] |Diesel Generator |

| |  |

| |Photo shows a diesel generator used for emergency power |

| |generator as may be found in a nuclear plant. |

| |Detailed description. |

|[pic] |Cable Trays |

| |A cable tray that holds electrical cables as may be found |

| |in a plant located in an area with high sensitivity to |

| |earthquakes. Note the structural supports. |

Example System Diagram

Below is an example of an overall electrical distribution system for a nuclear plant:

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Graphic courtesy USNRC

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Copyright © 1996-2008.  The Virtual Nuclear Tourist. All rights reserved. Revised: November 3, 2008.

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