Again in late March and early April, a series of powerful storms swept through Ohio — this time bringing gale-force winds that brought down trees, snapped utility poles, and pulled wide stretches of power line to the ground, causing electricity to stop flowing to homes and businesses around the state.
Line crews from Ohio electric cooperatives, as they do, worked diligently, for long hours and several days, to reconnect those co-op-served portions of the power grid that had gone offline.
Scenes like that, when they happen, are highly visible events; that visibility may even make them seem common, especially during storm season. In reality, however, power is available to electric meters served by Ohio electric cooperatives more than 99.9% of the time, according to Ben Wilson, director of power delivery engineering at Buckeye Power, which generates and supplies the electricity co-ops distribute to their members.
For the vast majority of time, no one really thinks about electricity or where it comes from, or how it gets to that lightbulb. It’s only during that fraction of a percent of the hours in a year when power is not available that the grid comes to public attention.
But what is ‘the grid’?
In the United States, the electricity industry has a generating capacity of 1.1 million megawatts, serving up electricity to nearly every home and business — including over a million Ohioans and 42 million people across the country who are served by electric cooperatives.
“In short, the electricity grid is the system and equipment required to get electric power from where it’s generated to where it’s used,” says Tom Schmidt, principal planning engineer at Buckeye Power. “It’s a vast, sprawling, yet interconnected network that has provided this essential public good for over 100 years.”
It’s that interconnectedness that makes it a grid.
“You can think of the power grid like our system of roadways,” Schmidt says. “Each individual part of each system is designed and built to handle a certain volume — cars and trucks on the highway system, electricity on the grid.”
In that analogy, the interstate highway system compares to the high-voltage transmission system that carries bulk electricity at a very high voltage from its generation source to individual distribution systems.
Transformers step down voltage along the way, like cars taking exit ramps from the highway onto city streets, then slowing further onto smaller roads until it’s just one single car turning onto a driveway: electricity entering a home at a much lower, safer voltage than what’s carried on the transmission lines.
A system of redundancy
In the same way that there may be several different routes your family could take to drive to, say, Columbus, in case an accident or traffic jam closes one roadway, engineers build redundancy into the system of power lines and substations that provides numerous pathways for electricity to move and eventually arrive at members’ homes and businesses.
Generally, those redundancies are what allow for the grid’s overall high reliability. When an accident happens on the grid’s interstate — the extra-high-voltage transmission system — power is automatically rerouted to prevent interruptions to hundreds of thousands of consumers.
Lower-voltage transmission lines provide power to fewer people and can often lack the redundancy of the extra-high-voltage transmission system. This is also true for local distribution lines operated by electric cooperatives. In cases with limited redundancy, electric cooperatives constantly strive to maintain and improve local distribution lines while also supporting investments in transmission line upgrades — all, of course, while responding to every outage as it happens.
Like highway construction projects, transmission power line improvements can be slow, unsightly, and costly. But once completed, these investments strengthen the transmission grid by adding redundancy — increasing reliability and resilience for many decades.
Balance of power
Thomas Edison created the first power grid in 1882 and other than a change from direct current to alternating current, the technology is basically the same because the physics is the same: Power producers must ensure that the amount of electricity generated at power plants and put into the grid precisely matches the amount of electricity used by consumers at any given moment. An imbalance can cause anything from widespread blackouts to damaged equipment.
The recent retirement of numerous power plants over the last couple of years, coupled with extreme weather events, has resulted in blackouts from supply shortages in Texas, California, Tennessee, North Carolina, and Kentucky. With the removal of significant amounts of baseload generation, such as that provided by coal-fired power plants, from the grid, less-dependable sources of electricity were unable to keep up with consumers’ demand.
Rolling blackouts are currently necessary to avert a larger-scale grid catastrophe; notably, in Texas in February 2021, at least 246 people died during Winter Storm Uri and the resulting supply shortage.
New and emerging technologies continue to optimize grid performance, effectiveness, and reliability. Most of Ohio’s electric cooperatives, for example, continually modernize their distribution systems using “smart grid” technology: controls, computers, automation, telecommunication, and smart meters that work together to dynamically respond to quickly changing conditions.
“The grid is greater than 99.9% reliable, and we are always working to put more nines after that decimal,” Wilson says. “All outages hurt, even when they are rare.”
The electric roadway
The electricity grid can be compared with our system of roads.
Extra-high-voltage transmission lines, 300 kV (300,000 volts) to 1,000 kV: compares to an interstate highway (high volume, high capacity); carries enough power for 100,000 to 500,000 homes.
Transmission lines, 100 kV to 300 kV: compares to a U.S. highway (not quite the capacity of an interstate); 10,000 to 100,000 homes.
Sub-transmission lines, 20kV to 100 kV: closer to a state highway (still lots of volume); 1,000 to 10,000 homes.
3-phase distribution, 4 kV to 40 kV: more like a city street in terms of volume; 100 to 1,000 homes.
Single-phase distribution, 2 kV to 15 kV: more like a smaller residential street; 10 to 100 homes.
Distribution service, 120 to 240 volts: the lines that come from the street to your house, compares to your driveway; 1 to 10 homes.