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Wide Area Blackouts: A Growing Risk

Tony Sleva's picture
President Prescient Transmission Systems

Tony Sleva is president and co-founder of Prescient Transmission Systems, where he provides risk assessments and innovative solutions for updating the electric power grid. Tony has more than 50...

  • Member since 2021
  • 32 items added with 8,014 views
  • Jul 16, 2021

Whether caused by an attack on power grid infrastructure, a design deficiency, or human error, wide area blackouts are a threat to electric power grid reliability. These large-scale blackouts lead to disruption of everything that requires electric power to function, from industrial manufacturing to residential air conditioning and wireless internet.

As we approach a future with hotter summers, more extreme storms, and widespread reliance on renewable energy sources, the risk of wide area blackouts is increased. If a wide area blackout were to occur during a heat wave or cold snap, the effects would be detrimental to the public and deadly to high risk individuals. The cost of recovery could be in the billions of dollars. But what exactly is a wide area blackout and why are they cause for concern?

The risk of wide area blackouts is a critical issue that can be addressed with risk assessments and enhancements to the existing electric power grid. Read on to learn more about wide area blackout risk. To gain a better understanding of how a risk assessment can help reduce the risk wide area blackouts, register for Prescient’s free webinar on Thursday, July 22 at 11:00 AM PDT.

What is a Wide Area Blackout?

A wide area blackout occurs when part of the electric power transmission system collapses, interrupting the flow of electric power to 250,000 customers or more. This is equivalent to shutting off electric power at many large neighborhood substations, leaving all the surrounding neighborhoods without power for several hours to days.

Several well-known wide area blackouts have occurred, including the Northeast blackout of 1965, Northeast blackout of 2003, and the Pacific southwest blackout of 2011. During these historic blackouts, power grid collapse resulted in simultaneous loss of electric power across several states, Canadian provinces, and parts of Mexico.

The blackouts in 1965, 2003, and 2011 were caused by human error (lack of attention to detail). The northeast blackout of 1965 occurred when protective relays tripped circuit breakers connected to five 230 KV transmission lines. The Northeast blackout of 2003 occurred when an overloaded 345 KV transmission line sagged into trees while the power grid was experiencing low voltage. The Pacific southwest blackout of 2011 occurred when a 500 KV air break switch was opened before its associated circuit breaker.

More recently, the United Kingdom blackout of 2019 occurred when two large generators tripped offline nearly simultaneously. This blackout was caused by a design deficiency.

Luckily, each of these blackouts required minimal repairs and power was restored in less than 24 hours. However, this may not be the case for future wide area blackouts.

What Causes Wide Area Blackouts

Wide area blackouts are caused by mismatches between energy production and energy consumption that exceed the normal tolerance band. During normal system operation, energy produced is equal to energy consumed; this is illustrated in Figure 1, where the beam is perfectly balanced on the balance point.

When customer load increases, the amount of power produced is ramped up to match energy with load. When customer load decreases, the amount of power produced is ramped down to match energy with load.

Figure 2 shows power grid operations during fault conditions. When faults occur, the transfer path between energy production facilities and consumers becomes distorted, resulting in a sudden large mismatch between production and consumption. Additionally, the amount of energy transmitted from production facilities is reduced. The amount of distortion is a function of initial conditions. The distortions and changes occur almost instantaneously.

When faults are cleared, a new transfer path is formed. Energy production and energy consumption are temporarily increased until a new balance point is established. At this point, there can be one of two potential outcomes: the grid returns to normal, balanced operating conditions; or the grid balance gets further distorted because energy consumption exceeds energy production, as shown in Figure 3.

If a new balance point is not established in a few seconds, a wide area blackout can occur in cascading fashion. The amount of distortion is a function of initial conditions and newly established, post-fault conditions.

Important Power System Parameters

A wide area blackout is the result of a combination of three important power system parameters: triggering events, risk factors, and voltage recovery. Let’s take a closer look at each of these three.

Triggering events are tipping points that may lead to a wide area blackout. During normal system operations, energy produced by power plants, windfarms, solar farms, etc., matches energy consumed by homeowners, businesses, and industry. Occasionally, a fault will trigger a mismatch in energy production and consumption. The fault type and duration determine if the fault will trigger a wide area blackout.

A three phase fault on a high voltage facility (345 KV, 500 KV, 765 KV) is the most likely triggering event. Fault duration, the power system response to the fault, is calculated in milliseconds. On the power grid, a 100 millisecond fault is long event, and a 200 millisecond fault is a very long event. The longer the fault duration, the more likely a wide area blackout will result.

Risk factors are variables that influence recovery. Some risk factors include:

  • System load: wide area blackouts are more likely to occur during peak load conditions when many power generators are operating near their maximum ratings (above 80% of their nameplate rating).
  • System voltage: wide area blackouts are more likely to occur if system voltage is less than nominal voltage before a fault occurs.
  • Type of electric power generating facility: traditional generators have voltage controls and speed controls that can quickly increase generator voltage and power output.
  • Predominant load type: loads, such as fan motors, pump motors, air conditioner motors, and space heaters, respond differently when voltage dips occur.
  • Spinning reserve, watts: Electric utilities schedule reserve power equal to the nameplate rating of the largest generator that is operating.
  • Spinning reserve, excitation: Electric utilities need to provide excitation energy to each transformer, transmission line, distribution line, and motor.

Fault induced delayed voltage recovery (FIDVR) is the final consideration. When voltage recovery extends beyond 10 seconds, a wide area blackout is likely.

Table 1 lists important considerations for each parameter:

To gain a more in depth understanding of wide area blackouts, check out Prescient’s blackout blog series or register for our upcoming webinar Wide Area Blackout Risk Assessment.

Infrequent But Concerning

Wide area blackouts are infrequent, happening on average about once every ten years. If they are so infrequent, why are they a concern?

Disruption to essential services, business operations, and industrial production have impacts that persist for days after power is restored. Rivers and streams can be polluted when digesters at sewage treatment plants overflow. Food that thawed in restaurant freezers must be discarded and replaced. Nuclear power plants must be inspected, and limiting conditions of operation must be resolved before power production can resume.

Additionally, the cost of recovery from wide area blackouts will only increase. The Northeast blackout of 2003 is estimated to have cost $6 billion. Costs include losses in sales and manufacturing, as well as food and medication that spoiled without refrigeration. The cost to individuals is often not accounted for. When negligence is discovered, individual electric utilities are assessed multi-million dollar civil penalties.

Future Projections

Although it is difficult to predict when and where a wide area blackout will occur, the conditions that lead to wide area blackouts are well understood. As the climate continues to change, wide area blackouts may become more frequent occurrences. Hotter, longer lasting summers will lead to more air conditioning usage and increased demand for electric power. Additionally, more intense winter storms have already stressed the power grid, leading to blackouts in Texas and Oregon during the winter of 2021. 

As renewable energy becomes a key source of electric power, the risk of wide area blackouts is even greater. It is vital that steps be taken now to reduce the risk of wide area blackouts in the future and maintain the hallmarks of the electric power grid: its resiliency in the face of change and reliability as demand increases.

What are your thoughts on wide area blackout risk? Add a comment below or register for Prescient’s upcoming webinar to join the conversation. 

Matt Chester's picture
Matt Chester on Jul 16, 2021

Thanks for sharing, Tony. Do you think with the recent headlines blackouts have unfortunately been making that leaders and grid operators are more amenable to new technologies, solutions, and ideas? Is there newfound momentum towards really solving this reliability issue in new ways?

Jim Stack's picture
Jim Stack on Jul 17, 2021

That is not really a lot of wide spread blackout. One every few years is not really too many. There are a lot more small outages. I wonder how all the outages and numbers show up?  I'm sure weather is the biggest cause with fires being next. 

Please let us know all the statistics also how long is the worst outages? 

Tony Sleva's picture
Tony Sleva on Jul 22, 2021

Utilities uses SAIDI (System Average Interruption Duration Index), SAIFI (System Average Interruption Frequency Index), and similar metrics to determine how they compare to peers.  Wide area blackouts are not included in these metrics.

The concern is that we need to do more to assure that the frequency of wide area blackouts does not increase as energy sources and customer loads change.

Michael Keller's picture
Michael Keller on Jul 19, 2021

Not so sure there are more extreme storms. However, there are more populated regions and that increases the probability of grid and distribution system disruptions. Couple that with grid instabilities associated with renewable energy and the likelihood of problems grows further. Add in more people living in fire and flood prone areas, more problems. Ditto for reducing the reliability of the grid by getting rid of coal plants. Getting rid of nuclear plants further exacerbates the problem.

Strikes me that many politicians and the green energy religion are pushing positions that seriously impact both the cost and reliability of the energy supply, but these same folks consider themselves as blameless while bearing no responsibility for the economic damage they create.

Patrick McGarry's picture
Patrick McGarry on Jul 20, 2021

Why is NERC so publicly silent on the topic of reliability?

FERC seems to make headlines daily on policy.

We know that power is becoming less reliable during the past three years. How is reliability and resiliency not the number one topic in the country right now. I know that NERC has historically been quieter than FERC, but I think they need to find their voice pretty quickly.

Three years ago, Randy Hardy was predicting a 5 to 10 gig capacity shortage for the PNW and it got very little attention.

Matt Chester's picture
Matt Chester on Jul 21, 2021

Thanks for sharing Patrick-- the PNW situation hopefully  has the silver lining of making more stakeholders find their voice and the issue come into more focus.

For those curious, I believe this report highlights the Hardy prediciton Patrick is mentioning. 


And for what it's worth, in looking up that report I found that Hardy has actually been beating this drum since the turn of the century...

Time to Fix Northwest's Inadequate Power Supply

Dr. Amal Khashab's picture
Dr. Amal Khashab on Jul 21, 2021

I would like to commend the author for his deep analysis for wide area blackouts. I might add that they were made in purpose to save the integrity of the whole power systems. They made by shedding predefined loads when the integrated system frequency drops below a specified value.

I described that in a post 4 months ago ,


Tony Sleva's picture
Tony Sleva on Jul 23, 2021

Thank you for reminding me of your post.  You and I are in complete agreement with respect to the issues.  My concern is that in the United States, electric companies have minimal undervoltage load shedding and extensive underfrequency load shedding.  With major energy sources at remote locations and major loads in metropolitan areas, underfrequency relaying does not respond to Fault Induced Delayed Voltage Recovery (FIDVR) events.  

In my experience, underfrequency relaying is effective when the concern is that there is not enough energy (P) to supply customer load.  When there is not enough excitation energy (Q), voltage decays, air conditioner motors stall, auxiliary systems in traditional power plants trip, and system collapse occurs.  Power factor biased undervoltage relaying schemes are needed to shed load during FIDVR events.

Adding new components, such as Solenoid Series Reactors (Patented by Prescient Transmission Systems) in series with high voltage circuit breakers, can stabilize voltage within 8 milliseconds of a fault and eliminate FIDVR concerns.

Dr. Amal Khashab's picture
Dr. Amal Khashab on Jul 23, 2021

Hi Tony

Thanks for reply. Control of V&Q is quite mature issue since the synchronous condenser , and all other FACETS applications. The problem may be raised again due to high penetration of solar PV which provide active power P only with zero Q. 


John Simonelli's picture
John Simonelli on Jul 29, 2021

Go read the 1967 Federal Power Commission Report (precursor to today’s FERC) on the great Northeast Blackout of 1964.  Many of the recommendations are still applicable today.

Matt Chester's picture
Matt Chester on Jul 29, 2021

Don't know that I could trace down a link to the report (any guidance on that, John?) but I did find the associated testimony on it from that time: Link

John Simonelli's picture
John Simonelli on Aug 3, 2021

I was able to get to a host of relevant information through IEEE but unfortunately I can't forward it. There has to be a public version out there somewhere.

Tony Sleva's picture
Thank Tony for the Post!
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