Electric “Load Shed”
It’s all about Supply and Demand – and MISO
MISO (Midcontinent Independent System Operator) manages the transmission grid for the mid-central U.S. states, stretching from North Dakota to Minnesota, down to Louisiana and back up to Michigan (see map below). MISO, along with other regional transmission operators, is responsible for organizing wholesale power markets, planning new transmission lines and ensuring the delivery of reliable and stable electricity across the region.
When demand for electricity nears supply capacity the integrity – or stability – of the grid can be compromised. To prevent major, sometimes catastrophic, grid failures the delivery of electricity to customers is intermittently and temporarily interrupted. This is called load shed.
The need for load shedding can be caused by extreme weather conditions (cold or hot), drastically increased demand, damage to system equipment, unforeseen generation plant outages, transmission constraints and/or a combination of these situations.
When the need arises and MISO determines load shedding is required to protect the grid and prevent longer, more widespread outages, SPU will be required to shed power load very quickly (i.e., systematically cut power to customers.)
SPU and the leadership team have developed an action plan that can be quickly implemented and communicated when/should MISO require us to drop load. This plan will ensure the prompt and orderly disconnection of power to various customers for intermittent periods of time – often referred to as “rolling blackouts” or “brownouts”. It is this proactive action that will prevent much larger and longer power outages.
To summarize –
• The decision to shed load is made at a higher, regional transmission level by MISO. It is not about SPU’s infrastructure or local capacity.
• SPU is required to shed load when instructed to and it must happen in a short period of time (i.e., 15-20 mins).
• Outages will be temporary and systematic.
• Outages will be “rolled” to reduce the outage time to any one customer/service area.
• Load shedding is a last resort.
• Most importantly – load shedding prevents more extensive and prolonged power outages that could severely affect the power grid for weeks or months. (Think Texas snowstorm in 2021).
Note: This is intended to be an educational and informative communication piece. It is not an indicator or warning that load shedding is imminent.
