December 19, 2023

Resilience & Reliability Are Not the Same Thing

Ian Flatley and Christian Nolden

This is a call to regulators, governments and industry leaders - we need to change how we operate and fast!

Many in the electricity industry confuse resilience and reliability as the same thing, when they are in fact, quite different.  

By focusing on reliability as a proxy for safety and resilience, we are leaving our networks increasingly vulnerable.   We believe it is possible to have a safe, reliable and resilient network without it costing the earth, but until regulators and industry leaders understand the differences, we will continue to have a system that largely ignores resilience and causes untold damage to people, livelihoods and the environment.

Firstly, it helps to define the two:

  • Reliability focuses on the prevention of the event happening in the first place. The focus is on maintaining smooth operation and minimizing the chances of failure
  • Resilience focuses on minimizing the consequences of any event and most importantly, enabling the system to bounce back if an event does happen. It's about planning for the worst and ensuring that the network can recover quickly

Bow tie risk analysis looks at both the probability of something happening and the consequences; it is helpful in striking a good balance between resilience and reliability.

Decisions on building and maintaining our power network need to consider both the probability of an event AND the possible impacts.   By only considering the reliability side of the bow tie, we leave ourselves vulnerable.  The reality is, *stuff* happens and so we need to have also catered for resilience.  

The North American Electric Reliability Corporation (NERC)’s 2023 ERO Reliability Risk Priorities Report explained how they have changed their focus from extreme natural events to extreme events and now to resilience to extreme events.

They identified that these events impact power resilience in several ways including:

  1. Increased intensity or frequency of events historically typical to a given area
  2. Instances of historically atypical events in an area
  3. Longer term trends (e.g., higher average temperatures impacting ratings)
  4. Impacts on supply chain due to geographically larger events


Of course, our industry will only act if there’s a change in how we are measured and rewarded – that's human nature.  In most countries, power delivery is typically measured in ways which focus only on reliability and outage minutes.

None of these show how safe or resilient a system is.  Reliability speaks broadly to when things run smoothly and generally without risk. Many resilience challenges arise when systems are exposed to extremes, such as extreme heat, or wind, which we are seeing more of.  

These reliability measures also tend to focus on ‘averages’ and even exclude the outliers, such as ‘major event days’ (MEDs).  That’s great for the power networks in hitting their targets but doesn’t give us an accurate reflection of what is really happening. This makes it harder to plan for and mitigate; we would get a truer picture if we retain those days in our measures.  

Metrics around resilience focus on those bad days and the ability of the network to resist negative outcomes. Some countries, such as those in Scandanavia already include the MEDs and have additional measures in place for resilience.

Removing these ‘major event days’ is a bit like living in fantasy land!  With climatic changes impacting countries around the world, it becomes harder to argue that these are one-off occurrences. As an industry, if we only focus on providing a reliable, uninterrupted power supply, we are putting our head in the sand. Extreme events are being seen globally, with increased regularity and we need to start planning for them.


For example, powerline-initiated wildfires in a changing climate which is showing longer droughts, higher winds and more frequent extreme weather events; fire risk should also be included, due to its high consequence.

Perversely, the output from wildfires are not included in national greenhouse gas emission or CO calculations, despite significantly contributing to climate decline. For example, the "carbon output" of fires (all started in a single day) on Black Saturday 2009, with the larger fires initiated by power lines, added an additional 40% to the entire Commonwealth of Australia's annual carbon output for that year.

Figure 1: Satellite Photo of 2009 Black Saturday Wildfires

Powerline-initiated wildfires are the deadliest and most widespread. Whilst powerline wildfire starts account for roughly 2 – 5% of all wildfires, powerline-initiated wildfires have accounted for over 80% of deaths associated with wildfires in Australia over the last 50 years.

Why: Because at approximately the same time and at the time of day when conditions are such that the rate of spread of a fire is likely to be at its peak”, the application of highest load on aging infrastructure leading to failure of these assets, or adjacent vegetation.

This statistic is repeated across multiple fire prone areas of the world. For example, of the top twenty most destructive Californian Wildfires, six are identified as powerline initiated.

Figure 2: Top 20 Most Destructive California Wildfires

In Florida, the failure to check the condition of poles led to the loss of 40-50 poles in a hurricane.

Regrettably, here we are in 2023, with powerlines still contributing to loss of life and infrastructure across both temperate and tropical areas.

These examples highlight the importance of considering both resilience and reliability in design, maintenance, and operation.

Focusing primarily on outage minutes also ignores the consequences of power outages on specific communities.  If there is an outage and we prioritize getting power back on for an urban conglomeration (bigger population) but ignore the rural area with a smaller population, we possibly miss the point that the farm has equipment, which creates food for the community and drives our economy.


Working on resilience might appear costly but if the industry was able to take a longer-term view we could make a long-term impact and enjoy considerable savings.  

For example, a wildfire can cost hundreds of millions of dollars.  An investment of an additional 10% of the initial capital cost can make the system ten-times more resilient and 98% more effective against wildfires.

Not all solutions come with a big price tag.  These are a couple of examples from us at Groundline, but there are plenty of others too, it is a matter of focus.

Review your maintenance regime, using technology like THOR Poletest, which can identify the most vulnerable poles.  It’s a quick and cost-effective way to provide insights, enabling you to make informed decisions about where to focus your repair and maintenance budget.  

Identify if you have power lines in vulnerable locations, where they could spark a vegetation fire.  Focus on these areas and use a solution like Covered Conductor in a targeted way.

Undergrounding is often seen as a good solution but can be hard to repair and more prone to damage due to its lack of visibility (getting dug up) and earthquakes.  Understand if you can make your existing grid more reliable and resilient - overhead lines are visible and easier to manage and may be the best solution in some areas.


This is a call to regulators, governments and industry leaders - we need to change how we operate and fast!

If we accept that climate change is real and we are experiencing more impactful wetter, drier, windier weather events then we need to be asking these questions:

  • How resilient are we to impact events?  
  • What can we do to achieve a resilient network today?  

NERC’s Report provides a useful framework for power providers, including the importance of developing detailed mitigation plans and a roadmap for their implementation which includes procedures for system restoration and system resiliency.  They also recommend that organizations accelerate the planning and construction of strategic, resilient transmission which enables power routing from remotely located renewable sources to areas of high demand (even if cross-region).

By focusing on both resilience and reliability, we can not only meet everyone's objectives but create a stronger, safer network that can withstand the challenges of the future.


Groundline is a global consultancy specializing in transmission and distribution lines engineering services for network operators and service providers.  

We bring creative thinking to projects, ensuring solutions are cost-effective, resilient, safe and good for the planet.  

With offices in the USA, the UK, Australia and New Zealand, we have experience in all aspects of the power lines industry - from 11kV to 500kV+, new builds to refurbishments, condition assessments to asset management, site support and design verifications, to project management.  Our team have worked around the world, from remote, dry deserts, to wild, wet rainforests, urban cities, to cyclone-prone prairies.

Whatever challenges you face, we understand your requirements.  

Get in touch to discuss how we can ensure your power network is fit for the future.

Contact us here

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