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Understanding Load Shed

Living in the Midwest, you may not be familiar with the term "load shed". But if you have friends or family from Texas or California you may have heard about it. Load shed, commonly known as rotating outages, is a way to temporally reduce demand or "load" on the power grid.

Transmission lines

Balancing Power Supply and Demand

Load shed is required when the demand for electricity approaches available supply levels, creating the potential for a dangerous imbalance. It’s a way to help reduce demand by turning power off to some customers to help prevent longer, larger outages. The immediate reduction of power demand is critical to prevent a catastrophic, extended failure of the larger power grid.

Load shed is required when the demand for electricity approaches available supply levels, creating the potential for a dangerous imbalance. It’s a way to help reduce power demand by turning power off to some customers to help prevent longer, larger outages. The immediate reduction of power demand is critical to prevent a catastrophic, extended failure of the larger power grid.

Several factors can lead to load shedding, including extreme weather, sharply increased power demand, unplanned generation plant outages, transmission constraints, unexpected damage to equipment, unavailability of purchased power or a combination of these situations.

Power generation and load must always match up, or remain balanced, otherwise the grid’s integrity will be compromised. There are strict standards that utilities must follow to maintain this balance. I&M is part of a larger regional power grid that is overseen and monitored by an organization called PJM Interconnection.

Shedding load is always a last resort, but, when necessary, this action helps prevent more extensive and prolonged power outages that could severely affect the reliability of the power grid for weeks or even months.

For example, in 2003, the biggest blackout in North American history plunged 50 million people into darkness for 31 hours. In that blackout, a high-voltage power line in northern Ohio brushed against some overgrown trees and tripped off-line. Over the next hour and a half, three other high voltage lines sagged into trees and tripped off-line, forcing other power lines to shoulder an extra burden. The overtaxed lines cut out or tripped, causing a cascade of transmission lines to cut out throughout southeastern Canada and eight northeastern states.

Monitoring the Grid

I&M is part of a larger regional power grid that is overseen and monitored by an organization called PJM Interconnection. PJM not only monitors the flow of electricity for customers in Indiana and Michigan, but it also controls power flows to 65 million customers across 13 states as well as the District of Columbia.

PJM serves as the “traffic cop” for the grid, coordinating how electricity moves across its service territory. It is responsible for ensuring the safety, reliability, and security of the power grid throughout its territory.

The power grid is the infrastructure. It is made up of the generators that make power, along with all the poles, wires and transformers that allow power to move across large areas until it reaches its destination – your home or business.

PJM monitors how much power is being generated – from sources including nuclear energy, solar, wind and water – by I&M and other power plants throughout its 13-state region. It also monitors how much energy is being used and the status of that power flowing through high-voltage transmission lines.

Being a part of PJM allows Indiana Michigan Power to better coordinate and optimize generation and transmission for the benefit of our customers.

Power Grid Emergency

In a power grid emergency, I&M and other utilities may be ordered to reduce the demand on their systems so the amount of available power generation can meet the demand.

If time permits, the first step is a public request for emergency energy conservation – asking you to reduce your energy use.

If further emergency action is required, PJM will direct I&M and other power companies to shed load through rotating outages. This is an emergency action of last resort, taken only to prevent a catastrophic, extended failure of the larger power grid.

I&M’s emergency plan interrupts power to parts of its service territory in a series of controlled outages. Rotating outages every 15 to 30 minutes helps limit the impact to customers.

I&M is committed to ensuring the safe and reliable delivery of power to our customers. While I&M may not control the issues or conditions that required PJM’s order to shed load, we will do everything in our power to reduce energy demand and avoid rotating outages.

If rotating outages are necessary, we will restore power as quickly as we are able to safely do so. In addition, we will keep you informed through email, text alerts, social media, phone and digital messages and local media.

What you should know
  • Load shed is also known as rolling blackouts, rotating outages or involuntary load shed
  • It is most likely to occur during peak demand hours (typically 6 a.m. – 9 a.m. and 2 p.m. – 7 p.m.) or extreme weather.
  • Rotating outages are a last resort when all other means for balancing supply and demand have been exhausted.
  • Outages are temporary and will only last until PJM determines that controlled outages are no longer required.
  • The load shed process is not controlled by Indiana Michigan Power or any other retail power provider. It is ordered by PJM and carried out by I&M.
  • The entire area overseen by PJM has the potential to be affected.

FAQ

Load shed could be localized or it could impact the entire area that PJM territory oversees which includes 65 million customers across 13 states as well as the District of Columbia.

  • Localized load shed could occur if there’s unexpected damage to infrastructure in a specific area. For example, damage to a major transmission line, such as a tree falling and taking it down, or if there’s an unexpected outage at a generating plant, producing a shortfall of energy to the area. These scenarios usually impact a smaller, more localized group of customers, but could also span a larger geographic footprint (within I&M’s territory) depending on the conditions. Typically, I&M will determine if localized load shed is needed.
  • PJM Systemwide load shed is initiated only by PJM as a result of an imbalance of supply and demand of electricity. It is required to protect the power grid. Since the entire power grid is connected, an issue in another state can even affect customers in I&M’s territory. Such a scenario could occur due to extreme weather, such as a tornado storm, winter storm, or extreme high or low temperatures.

Power grid emergencies are not common. However, PJM and member power companies maintain plans and regular drills to prepare for such emergencies.

The most recent request occurred during the extreme cold weather on Christmas Eve 2022. I&M customers and customers of other utilities in the region rose to the request to reduce energy use, and rotating outages were not needed.

Although I&M may be generating adequate power to serve its customers, we are part of the larger grid where energy is transmitted across great distances to multiple states. In order to protect the power grid, PJM may order I&M and other power company members to begin shedding load under emergency conditions. This is required to avoid catastrophic grid failures which could result in prolonged power outages. In fact, if we don’t shed enough load in time, PJM can shed the required amount of load on our behalf

Since rotating outages are always a last resort, PJM has other measures it will try to avoid a power shortfall, such as importing more power from other resources or tapping into emergency reserves. PJM can also order its power company members, like I&M, to make a public appeal to have customers voluntarily reduce their energy use to help prevent rotating outages.

Whenever possible, a request to conserve energy comes before other emergency action like rolling outages. When PJM orders a public appeal for emergency energy conservation, we will ask all I&M customers to voluntarily reduce energy use as much as possible until the system strain has passed. You should use the electricity needed for personal safety and to protect against property damage.

We will keep you informed through multiple communications channels including email, text alerts, social media, phone and digital messages and local media. We may also ask for your help in conserving energy prior to a PJM ordered public appeal, given the conditions.

When we work together, small adjustments can make a significant difference in reducing energy use and easing the emergency.

  • Set your thermostat a few degrees lower in the winter / higher in the summer than normal.
  • Wait to use your stove, dishwasher, washer, dryer and other appliances.
  • Turn off unnecessary lights, inside and outside.
  • Unplug computers, gaming consoles and other electronics.
  • Turn off office and manufacturing equipment, wherever possible.
  • Large consumers of power should consider reducing or shutting down non-essential production processes.
  • Avoid use of electric space heaters.
  • More tips on how to reduce your energy use at home or work or on ElectricIdeas.com

When I&M is directed to reduce the load on its power system in an emergency, we use rotating outages. PJM tells I&M and other power utilities how much electric load we must reduce. In our emergency plan,

  • I&M matches the number of circuits that add up to the amount of power, or megawatts we are required to shed. For example, a circuit might have 500 to 1,500 customers, and I&M might need to disconnect 25 circuits. Those circuits would be in different locations around I&M’s two-state service territory. I&M would temporarily disconnect power to these circuits.
  • As one group of customers completes its outage cycle, the next group is removed from service and the first is returned to service. Groups with larger concentration of customers i.e., inner city and suburbs can typically shed large loads faster than more remote, less populated areas.
  • The rotating outages will last 15 to 30 minutes to help limit the impact to customers.
  • We do our best to avoid critical customers, including essential public health and safety services and facilities, such as hospitals, fire and police departments and water systems.
  • When I&M gets word from PJM that the rotating outages have reduced power enough, the rotating outages can end. During a longer emergency period, PJM could order rotating outages to continue until the system returns to lower levels of emergency and then to normal operations.
  • During rotating outages, power is controlled by centralized switching. Even though you may not see our crews out restoring power, be assured we are working to protect the power grid that serves you and we will restore your power as soon as possible.

PJM’s decision to implement rotating outages is made as a last resort and requires immediate action on very short notice. I&M will likely be unable to warn affected customers before a rotating outage. However, if rotating outages must occur, we will make every attempt to communicate the status to you as soon as possible through text alerts, social media, phone and digital messages and local media.

I&M has agreements in place with some commercial and industrial customers allowing us to reduce their energy use to agreed upon levels during periods of high energy demand such as a load shed event.

Many residential and business customers are enrolled in Power Rewards. These are voluntary demand response programs that helps reduce load. Customers can earn bill credits during a non-emergency Peak Energy Event.

Load reduction by these customers and a public request to reduce energy use could help avoid the need for rotating outages to a broader group of customers. However, should conditions continue to escalate, it still helps reduce the overall quantity of megawatts required to be shed. This means fewer customers are potentially impacted with rolling outages.

Regarding streetlights, they make up a very small percentage of our power demand, and we do not have the ability to remotely turn them off.

Technologies exist that allow energy to be stored for future supply, but to date have not been cost-effective compared to alternatives. As these technologies continue to emerge, and in the future become more cost-effective alternatives to other types of investments to enhance resilience, they may play a role in preventing load shed.

Power companies are connected to each other so they can work together for reliable electric service. They help each other out when there are power plant or other electric system problems. They work to get their customers the best price on power from different power plants. They work together to plan and build the right transmission lines to deliver power where it needs to go.

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