One of the pleasures of working with the energy industry is the opportunity to hang around people who are passionate about energy. One of those people is EnergyCAP Project Manager David Ulmer.
David used to work for PJM Interconnection, a grid operator. After attending his recent Energy Leader webinar on Power Grid Fundamentals, I’ve gained new respect for the unsung heroes of the grid—the grid operators who manage the supply of electricity from minute to minute to ensure that the electricity is there when it's needed.
Let's take a look at some of David's insights into these daily behind-the-scenes heroics.
There are several grid operators across North America. They're responsible for:
- ensuring that the transmission system is operating in a reliable fashion
- providing all generators with equal access to the grid
- balancing the output of generators with the ever-changing demand for electricity
- operating the grid’s resources as cost-effectively as possible
Grid operators play a unique role in the provision of electricity. They function as Independent System Operators (ISOs)—they might or might not own any grid assets, but their role is to manage the grid in a way that allows all participants fair and equal access. Their function is similar to air traffic controllers, who are tasked with managing the skies in a fair and efficient manner. And although grid operators are not landing planes at Chicago's O'Hare International Airport, they are helping ensure that electricity is available every time we flick a light switch.
So how does electric power get from the electricity generator to the end user—your home or business?
Electricity generators, regardless of their fuel type or operation, do not supply their power directly to residential customers, even if they’re nearby. Instead, the output of those generators passes through a transformer at a substation, where the electrical output is converted to a higher voltage to travel across the high voltage transmission system—a network of steel towers crisscrossing the countryside.
Why is this conversion necessary? It’s all about efficiency. When electricity is converted to a higher voltage, there are fewer line losses during transmission; that is, losses of electricity, usually in the form of heat. It is also easier to transport electricity over very long distances at the higher voltages (up to 768 kilovolts in the United States). So the transformer provides up-conversion from the voltage coming from the generator to the higher voltage handled by the high voltage transmission lines. This process in carefully monitored by a grid operator.
After the electricity has been transported for long distances via the high voltage transmission towers, it is converted down to lower voltages at substations. Then it can be transported on those wooden poles, down your street, and eventually to your home or business. By the time the electricity “arrives” at your outlet, voltage has been reduced to roughly 110 volts.
Depending on the rules in your state, you may work with a single electricity utility to both provide and distribute your electricity or you may have the choice to select your electricity provider (company responsible for procuring your electricity) separate from your local distribution company (LDC), which manages and maintains the local low-voltage distribution system.
Grid management is an incredibly dynamic process. A helpful analogy would be to think of the “pool” of available electrical energy on the grid as a bathtub full of water with a spigot and a drain. The spigot is supply, and the drain is demand. But the drain aperture is constantly changing in size. The grid operators’ responsibility is to maintain the water level despite this uncertainty. When the drain gets bigger, the operators open the spigot a little more. When it shrinks, they close the spigot to reduce the supply.
On the grid, there is a constant tension or push and pull between the resources (generators) that are adding power to the grid and the consumers that are drawing electrical power from the grid to do work. Since there are few options for electricity storage, this balance can only be maintained by balancing available generation resources to match the current demand. This is a tricky job, and mistakes can be costly. Make the wrong call, and you might have to idle a nuclear reactor that could take days to start up again.
Whenever electricity is used, the drag on the system tends to slow the frequency, which must be kept constant (at 60 Hertz in the U.S.) to avoid damage to devices using the electrical current. Whenever the trend line is above 60 Hertz, the grid is over-producing in comparison to grid demand. Whenever the trend line is below 60, there is more power being drawn from the system than is currently being supplied. Grid operators try to keep that trend line as close to the center as possible.
Typical boundaries (measured in Hertz) would be from 59.95 to 60.05. If these tolerances are exceeded, the grid equipment has automated procedures for self-regulation that may include automatically shutting down equipment or turning off electricity for some users. Grid operators are constantly managing the system to ensure that these more extreme actions are not required.
If you want to find out more about the operations of the grid, we have repackaged David’s webinar as the latest installment in our eBook series. Power Grid Fundamentals and Electricity Pricing is now available online. Feel free to download the eBook and share it with your friends and colleagues.