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 electricity is generated minute by minute and transmitted safely and reliably across the high-voltage transmission lines. Local utilities are responsible to safely and reliably deliver the electricity to their customers.

MISO does not own any equipment on the bulk electric system. Our members do. MISO manages the generation of electricity and the transmission of electricity across high-voltage power lines. 

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

1. Manage the generation and transmission of electricity across high-voltage lines located within its region
2. Manage the buying and selling of electricity within its region
3. Plan for 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 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.

MISO grid operators have a set of procedures or "tools" they rely on to address potential and actual conditions like extreme weather that can negatively affect the grid. For example, severe weather can impact generators and/or transmission lines and knock them offline. Scenarios like these may require emergency procedures to keep power flowing. The emergency procedures provide operators with additional resources not available under normal grid conditions. They 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 limit damage to the grid and avoid wide-spread outages. This step, called load shed, is rarely used.

MISO communicates with our members every day to coordinate plans for any obstacle – such as extreme weather – and reliably forecast how much energy homes and businesses will need across the region. 

Conservative Operations: Provides an early indication that system conditions may require emergency procedures or conservative operations. In the declaration, MISO asks members to review outage plans and determine which planned maintenance or testing can be postponed. The goal of the declaration is to defer, delay or recall any non-essential maintenance.

Current emergency operating plans include issuing any of the following notifications:

Capacity Advisory: Used for situational awareness. The 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: Tells members that electricity supply is tight and system conditions may require emergency actions.

Maximum Generation Warning: Indicates operating reserve requirements may not be met in the near future without taking actions. MISO is directing members to prepare for a possible maximum generation event. When issued, MISO may direct utilities to issue public appeals to conserve electricity.

Maximum Generation Event: This notification includes several steps that include directing members to turn on all available emergency generation, directing members to implement procedures designed to reduce energy demand,  purchasing emergency energy from our neighbors (if available), and, as a last resort, interrupting power to consumers (known as shedding load).

NOTE: Load shed is always a last resort decision designed to protect the bulk electric system from collapsing and creating wide-spread blackouts. MISO's responsibility is to identify the area where the electricity needs to be interrupted and the amount of electricity that needs to be cut. The utilities in charge of the area(s) (Local Balancing Authorities) are responsible for individual load shed programs which take into account critical load identification.  

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.