The Electric Reliability Council of Texas asked utilities on the electric grid to initiate controlled interruptions — typically lasting 15 to 45 minutes per neighborhood — because supplies of reserve power are exhausted. ERCOT says without this safety valve, generators would overload and begin shutting down to avoid damage, causing a domino effect statewide, as Centerpoint's Alicia Dixon explains.
"They have mandated utilities like Centerpoint Energy, utilities throughout the state of Texas, to shed load in order to protect the entire system within the state. ERCOT is saying that there were some problems with some power plants overnight due to the extreme weather. We've pre-identified circuits that we can bring down in order to shed load until the system recovers, but this is a protective measure designed to prevent longer, more wide-spread outages and damage to the system."
Hot summers can cause rolling blackouts because of the heavy load from air conditioning, but cold weather can also be a problem.
"There are many that heat their homes with electric heat, and so it can not only be a problem in the summer when air conditioning load is extremely high, but when you have power plants that are down and it simply isn't enough to meet the demand due to the extreme cold weather because of the heating needs."
But Dixon says rotating outages do not typically affect critical-need customers.
"These outages are impacting customers served off our distribution lines — the power lines that run behind your home and behind businesses. We're not impacting customers served off the higher voltage lines that come off the power plants. Transmission lines serve like our downtown Houston area, so we're not impacting critical facilities like downtown Houston, the Texas Medical Center."
Dixon says utility companies are trying not to duplicate the same customers affected by the power cuts throughout the day.