Electric System 101

If you’re like most people, how the power grid works is not something you think about every day. Many people have a vague understanding that electricity comes into their home from wires on a pole outside or, in some cases, underground. It goes into a metal box in the basement and from there to outlets throughout the house. In fact, most people don’t think about electricity at all, until the power goes out.

However, how electricity gets generated, transmitted hundreds or even thousands of miles, and then distributed to homes and businesses is not only important, it’s central to how we receive the power to run our lights, refrigerators, washing machines, TVs and computers. It makes life easier, safer, and more enjoyable.

power-transmissionTo help you understand the process, system, and expense it takes to provide power to every home, office, factory, and facility – not just on Aquidneck Island, but throughout the country – we’re presenting a brief “Electric System 101” to explain the journey electricity takes.

All the electrical power that we use starts at a power plant where a generator produces electricity. In most cases, generators are fueled by coal, oil, natural gas, or nuclear. In New England, natural gas is the dominant fuel type that powers generation. There are approximately 7,000 power plants of all sizes in the United States generating power that’s distributed throughout the country over the power distribution grid. Although National Grid is not in the business of generating power, we do purchase that power on behalf of our customers, the cost of which is passed on to our customers without markup. (Image courtesy of How Stuff Works)


A large generator typically produces thousands of volts of electricity at any given time.
To transmit that electricity efficiently through wires over long distances, however, requires conversion to a higher voltage but lower current. To do that, the electricity is sent from the generator to a transmission substation at the power plant. There it is converted to extremely high voltage for the transmission grid — that network of large metal or wooden towers and poles with massive wires stretching for miles, capable of carrying enormous amounts of power.


That high voltage electricity is far too powerful for use in an average home or business – it needs to come off the transmission grid and be converted back, or stepped down, for distribution. This process occurs in a power substation located near to the ultimate destination of the electricity, such as a residential neighborhood or shopping district.

These substations — such as our Jepson and Newport substations and others across Aquidneck Island — have several functions:

  • Transforming high voltage transmission electricity from tens or hundreds of thousands of volts down to usable amounts of less than 10,000 volts
  • Splitting that lower-voltage power using a device called a “bus” connected to a smaller generator which steps the electricity down to approximately 7,200 volts and sends it in multiple directions over distribution lines
  • Being able to disconnect from the transmission or distribution grid to accommodate various power loads and protect the system from damage

After entering the distribution grid from the substation, the electricity is sent to yet another set of transformers located near homes and businesses where it is stepped down even further, from 7,200 volts to the standard 240-volt household current used to power countless appliances, tools, and devices we use every day.