The Grid: What it is and How it works

By August 10, 2018Industry news
Silhouettes high voltage electric pylon in sunset background.

Electricity can’t be stored – at least, not economically in the large quantities produced by power generating plants. So, whenever you turn on a switch and draw electricity, you are receiving power generated at that very same moment.

The electrical grid is the sophisticated network of interconnected power lines that immediately transmits electricity from the thousands of places where it is generated to you and all other end users upon demand. The changing balance of electricity supply and demand on the grid is carefully managed in real time by regional entities called “balancing authorities.” By linking together the sources of electricity and routing them to large areas, the grid and its redundant power generators furnish electricity to everyone with a high reliability that is otherwise impossible.

High Voltage Transmission

Whether it’s electricity from Atlantic Energy’s renewable sources such as hydropower, wind and solar, or electricity generated any other way, in order to reach you after it’s produced, it must be sent onto the electrical grid.

Not just any voltage will do. The transmission wires themselves create resistance to the flow of electricity, and that resistance means some energy is lost during transmission. The longer the transmission wires, the greater the resistance and the worse the electricity loss – and the grid involves distances of hundreds or thousands of miles.

But fortunately, less electricity is lost when its voltage is higher. So, newly-generated electricity first passes through a substation with an electrical transformer that steps up the voltage as necessary for transmission through the grid. For example, electricity generated by solar technology or other power plants may initially have a relatively low voltage between 2 and 30 kilovolts. At the substation, the voltage is typically stepped up to 500 kilovolts for long-distance transmission.

Tall Towers, Long Distances

A key component of the grid – the familiar overhead wires stretched along large steel towers – supports high voltage electricity of 230, 500 or 765 kilovolts over its transmission lines. The United States has nearly 160,000 miles of those high voltage power lines, handling electricity generated by more than 7,300 power plants and delivering it over long distances with minimal energy loss.

To ensure public safety around high voltage transmission lines, regulations specify how high off the ground the wires must be – typically a range of 60 to 150 feet in height from the ground.

Stepping Down for Distribution

Just as the electricity voltage is boosted before it enters the grid, when it leaves the grid it must be stepped down to safe, consumer levels, before being distributed to end users. High voltage electricity exiting the grid passes through a substation with a step-down transformer to reduce the voltage. As the local utility distributes the electricity via its network of power lines, additional transformers located within neighborhoods where the electricity will actually be used further reduce its voltage to the levels needed for commercial and residential use.

Three Grids, Not One

The United States does not have one single, nationwide electricity grid. Rather, for the lower 48 states, there are three distinct interconnections of electrical transmission lines, which operate mostly independently from each other and with only limited transfers of energy between them.

•   The “Eastern Interconnection” serves the states east of the Rocky Mountains and a portion of northern Texas.

•   The “Western Interconnection” serves the states extending west from the Rocky Mountains.

•   The “Electric Reliability Council of Texas” (ERCOT) covers most, but not all, of Texas.

Each of those interconnections links up the electricity generators within them, and ensures that each electric utility in the mainland United States is connected to at least one other utility. That network structure provides reliability to the power system, by offering multiple routes for electricity to flow and by allowing generators to supply electricity to consumers in various different locations. Because of that redundancy, if any particular transmission line or power plant should fail, end users will most likely still receive electricity with no interruption in service.

Balancing Act

Considering that electric power must be generated at the time it is needed for use, and that the demand for electricity varies at different times and under different conditions, someone has to ensure that the supply of electricity is continually balanced with the demand. That is the responsibility of the balancing authorities.

For the Eastern Interconnection, Western Interconnection and Texas grid, there are a total of 74 balancing authorities, each covering a particular territory. The majority of balancing authorities are electric utilities that have accepted the balancing responsibilities for the area they serve.

In real time, around the clock 24/7, each balancing authority works with its neighbors throughout the grid to ensure that sufficient electricity is produced and available to meet the changing demand. A balancing authority has several means of doing so, including forecasting the expected demand, directing specific generators within its region to turn on or off as needed, and importing additional electricity from neighboring balancing authorities to compensate for any local shortfall (or conversely, exporting surplus electricity to other balancing authorities that need it).

The balancing authorities are also responsible for reconciling the intermittent nature of some renewable energy sources, such as solar and wind, with the ongoing demand for electricity. If the sun is not shining or there is little to no wind, then the output of solar and wind power plants will drop. A balancing authority makes up the difference by temporarily drawing from other types of generators that can be quickly ramped on and off as needed.

Balancing authorities identify potential problems before they become critical, and react immediately to prevent circumstances that could threaten reliable electricity service.

Electrifying Achievement

From the miles of transmission lines with voltage transformers at each end, to the minute-by-minute monitoring of each grid by the balancing authorities, a great deal of technology, infrastructure and human oversight enables the reliable delivery of electricity to you, whenever you need it.

Atlantic Energy is pleased that a most robust system delivers our electricity supply to our customers.

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