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MISO (mEYE-so)

Use "MISO" in all references to our corporate name

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Grid Conditions Primer

National weather forecasts show normal/slightly above normal temperatures for the MISO region. Forecasters expect a near to slightly below normal hurricane season in the Atlantic Basin.  
NOAA 2023

The electrical grid is an interconnected network for delivering electricity from producers to consumers. It consists of generating stations that produce electrical power, high voltage transmission lines that deliver electricity to sub-stations,  and distribution lines that deliver power to homes, schools and business.

As a grid operator, MISO's role is to ensure the right amount of  high-voltage electricity is generated and transmitted safely and reliably to our member utilities. MISO does not own any equipment on the bulk electric system. Our members do. It is the local utilities who are responsible for delivering electricity safely and reliably to their customers.

MISO is a Regional Transmission Organization (RTO) responsible for doing three things:

  1. Managing the generation and transmission of electricity across high-voltage lines located within its region
  2. Managing the buying and selling of electricity within its region
  3. Planning the MISO region grid of tomorrow

MISO's role and responsibilities can be compared to those of an air traffic controller. Air traffic controllers are responsible for ensuring planes get from point A to point B safely and reliably 24/7/365. They don't own the planes, they don't own the runways, they don't own the terminals. They simply manage the movement of planes.

MISO manages the movement of electrons across the bulk electric system in its region 24/7/365. From generation to transmission. MISO does not own the generators, the transmission towers, or the transmission lines. Our members do.

MISO makes sure the right amount of electricity is generated and transmitted to our member utilities who are responsible for delivering the power to their customers.

During abnormal conditions, such as severe weather, MISO grid operators may need to rely on a set of procedures or "tools" to keep power flowing and protect the bulk electric system. For example, severe weather can impact fuel supplies or knock generators and/or transmission lines offline. Scenarios like these may require the implementation of emergency procedures to maintain reliability. MISO's emergency procedures provide operators with additional resources not available under normal grid conditions. These include, but are not limited to, accessing reserve and/or emergency generation, working with members to reduce power usage, and importing emergency power. As a last resort, operators may need to temporarily interrupt power to consumers in order to avoid wide-spread outages and protect the system from long-term damage. This step, known in the electric industry as load shed, is rarely used.

MISO communicates and partners with its members every day to ensure power is flowing and the lights stay on. When it appears electricity supply will be "tight," MISO notifies member operators of what we are seeing, what we expect to see, and what actions operators need to take. MISO posts these notifications on its website at the bottom of the home page. They can also be viewed on the MISO app.

Common notifications and what they mean: 

Hot/Cold/Severe Weather Alerts: Used for situational awareness, this notification alerts members that unusual weather conditions may impact generation and/or transmission capacity.  

Conservative Operations: Used for situational awareness, this notification provides an early indication that system conditions may require emergency procedures or conservative operations. This notification asks members to review outage plans and determine which planned maintenance or testing can be postponed. The purpose is to defer, delay or recall any non-essential maintenance.

Capacity Advisory: Used for situational awareness, this message informs MISO members that, based on projected system conditions and capacity levels, there may be a need in the coming days to bring additional units on-line. Members are instructed to prepare for this possibility.

Maximum Generation Alert: Used for situational awareness, this notification serves as an early alert that system conditions may require emergency actions. 

Maximum Generation Warning: This notification asks member operators to prepare for a possible maximum generation event. It indicates operating reserve requirements may not be met in the near future without taking actions. 

Maximum Generation Event: This notification includes multiple steps that include directing members to turn on all available emergency generation, directing members to ask their customers to reduce energy usage, purchasing any available emergency energy from our neighbors, and, as a last resort, temporarily interrupting power to consumers (i.e. rolling outages).

NOTE: Power interruptions are always a last resort measure necessary to protect the reliability of  the power grid. They occur when electricity supply can no longer meet demand. During these rare situations, MISO's responsibility as a grid operator is to identify the area where the power interruptions need to occur along with the amount of electricity that needs to be reduced in order to balance electricity supply and demand. MISO's member utilities determine which customers will temporarily lose power.

In some extreme situations such as severe weather events or unplanned outages, there may be a point where electricity consumption looks like it will be greater than the available supply i.e. demand outweighs supply. When facing this low probability scenario, operators have to find ways to quickly decrease consumption in order to keep power flowing and protect the grid from the possibility of cascading outages. One way they do that is by directing member utilities to issue public conservation appeals. The purpose of the appeal is to get consumers to immediately decrease their electricity usage. When done at scale, these actions can significantly reduce energy demand on the grid and reduce or even eliminate the need for temporary power interruptions. 

Conservation measures can be as simple as adjusting a thermostat, turning off lights, and/or delaying the use of appliances like a washer or dryer. During these uncommon situations, MISO encourages utility customers to follow their electric company’s tips on conserving electricity.

MISO, as a Regional Transmission Organization, has a specific role to play, and specific "tools" it may rely upon, when it comes to power restoration. 

Power Restoration Role and Responsibilities

MISO’s primary role during a power grid restoration in its region is to serve as a facilitator during the restoration process: coordinating, exchanging information, and maintaining stability.

MISO is responsible for the collection and exchange of information, as well as communication and coordination with the impacted entities.  Additionally, MISO is responsible for working with our impacted members to coordinate getting the power flowing again across the grid while maintaining stability so as to prevent a re-collapse of the system.

MISO also coordinates with its neighbors to ensure stability throughout the restoration process.

Restoration "Tools" or Procedures

MISO operators can rely on a number of emergency procedures to ensure grid stability and reliability during restoration. These "tools" can include sending emergency notifications and declarations to member operators in the MISO region. Some of the notification and declarations that could be issued include:

  • Transmission Advisory
    • This communication tool is used for situational awareness. The message informs members that, based on projected system conditions, there may a transmission issue that will require specific actions to be taken in order to ensure reliability.
  • Local Transmission Emergency
    • This declaration identifies a specific entity or entities and provides instructions for mitigating a transmission emergency for a specific area of the grid
  • Transmission System Emergency
    • This declaration provides instructions for mitigating operating emergencies on the Transmission System that have the potential to exceed a pre-defined system operating limit that could lead to instability or outages.