by Brooke Barone on November 30, 2012

A Cheat Sheet for Electrical Substations

A Cheat Sheet for Electrical Substations

Posted by Brooke Barone on Nov 30, 2012 8:33:00 AM

Electricity- a hot commodity in modern life.

A Transmission and Distribution (T&D) System, has a notorious job of delivering electricity to consumers 24/7, 365 days a year.

But before the electricity can travel into your home, it must pass through a substation first. A substation is an assemblage of equipment where electrical energy is passed in order to be stepped up or stepped down.

Transformers inside a substation change the voltage levels between high transmission voltages and lower distribution voltages. The high transmission voltages are used to carry electricity longer distances, like across the country, whereas lower distribution voltages travel to industrial, commercial or residential consumers.

In a T&D system, the major components typically consist of transmission lines, distribution lines, substations and switchyards.

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Inside a substation is like its own unique “power world” where every pole, bolt, stand, surge arrestor or structure plays its own individual role.

The three main types of structures found inside a substation include:

1.)    Dead-End Structures

2.)    Static Poles

3.)    Bus Supports/ Equipment Stands

Dead-end Structures are where the line ends or angles off. They are typically constructed with heavier steel in case they are needed to carry heavier tension. The two most common dead-end structures are H-Frame and A-Frame structures.

 H frame graph

A frame graph resized 600

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The second structure, a Static Pole, is a single, free-standing pole that creates a shield to protect all of the equipment inside a substation from lightning. Static poles may or may not have overhead shield wires attached to enhance protection. It depends on the size of the substation as to how many static poles are needed.             

NOTE: Tapered tubular design is typically efficient and economical in dead-end and static pole situations when compared to AISC standard shape structures.

Bus Supports are the most basic structure found inside a substation. Its main purpose is to provide support for rigid bus as it travels though the substation. Rigid bus is stiff and will not move around during weather events. Unlike rigid, flexible bus is typically used in high seismic describe the imageareas in order to be able to move and dampen the seismic forces that occur. 

Electrical equipment can be of significant weight and must meet specific guidelines for structural loads, deflection limits or clearance requirements. Equipment Stands are the structures that the actual equipment sit on.

Examples of some equipment stands include:

  • Potential Transformers (PT) Stands
  • Current Transformers (CT) Stands
  • Coupling Capacitor Voltage Transformer (CCVT ) Stands
  • Lightning Arresters (LA)
  • Switch Stands

 So, although the concept seems quick and simple like flipping a light switch, much more is going on behind the scenes.  


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Tags: electrical substations, Voltage, transmission lines, substation, power, distribution lines, switchyards, equipment, static

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