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The somewhat mysterious inner workings of the electrical system are an important part of what keeps the technological tools of modern-day business ticking. Often taken for granted, electrical energy provides power for everything from the most sophisticated data center to the office coffee pot. A basic understanding of how this system works can help to develop a better appreciation for the conveniences it makes possible. Additionally, some electrical issues that come up can be easily solved by simply knowing how the system is put together and where to look.
Generation Systems
Most electricity is generated at central station power plants owned and operated by electric utility companies. These large industrial facilities house massive steam-driven turbines or gas turbines coupled to electrical generators that produce three-phase alternating current at high voltages. Other generating technologies include nuclear power, hydroelectric dams, wind energy and solar arrays that pump power into the grid. Next, these high-voltage currents are transmitted over long distances. Finally, the electricity arrives at the home or office load center, which distributes it to switches and outlets.
Transmission Systems
Even the best conducting materials like copper wire present some resistance to the flow of electric current. This electrical resistance is a parasitic element of the system that reduces the efficiency of transporting electrical energy over distances. One measure taken to reduce line losses is transforming the voltage into much higher potential levels. That process allows the transmission of energy at lower current levels reducing losses to resistance.
The transmission system consists of huge transformers and tall towers strung with specially designed cables to accomplish this task. Energy is routed over long distances at electrical potentials exceeding 200,000 volts. The electrical system in the continental U.S. is divided into three regional grid systems with limited interconnections. These semi-autonomous electrical grids serve the eastern U.S., western U.S. and the state of Texas. Once the energy arrives at an urban location where it will be delivered, transmission-level voltages must be stepped down to distribution voltage levels.
Distribution Systems
Large electricity consumers, like urban centers and factories, are served by connections to lower voltage distribution systems. The process of stepping down the voltage potential is accomplished at utility substations. Large pad-mount transformers populate these facilities, which are normally fenced-in. Care is taken to minimize any potentially combustible materials in the vicinity of these electrical switchyards to enhance safety.
High wind conditions and other weather events occasionally blow tree limbs onto distribution lines requiring line crews to perform repairs. Substations are also equipped with high voltage switchgear that can isolate and de-energize circuits for distribution system maintenance when required.
The distribution system is made up of utility poles and smaller sized conductors and transformers. Electrical energy leaving the substation is routed along the utility easements and right of ways beside roads and across properties to the delivery points. Depending upon the type of service required at customer locations, different types of switchgear and pole-mounted transformers are installed. These perform the final voltage step-down necessary to provide end-use voltage levels and single or three-phase power.
Customer Electrical Systems
Utility mains power is delivered to customer premises through some arrangement of weather shielding conduits and fittings. The final piece of equipment at which custody of the electrical energy changes hands is an electrical meter. Metering technology has advanced significantly in the past quarter-century. Older mechanical style meters have been replaced with computer-controlled devices to measure the quantity of electrical energy being consumed more accurately. Once the energy has passed through the meter, it is frequently connected to a distribution panel that houses circuit breakers.
Electrical circuit breakers are switches and overcurrent devices that protect people and equipment in the event of short circuits and other electrical faults. They also serve to subdivide the energy into discrete circuits that are connected to devices such as outlets, switches and light fixtures. A thermal device inside each breaker senses a high current flow condition when a short or ground fault occurs and immediately switches the breaker off to automatically remove power from the affected circuit.
This silent, invisible electrical energy drives the engines of commerce. Understanding the elements of the electrical grid and how they function is a fascinating and informative journey.
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