1.0 Introduction - engineering innovations for a sustainable future:
Sustainable future for the Power and Energy sector is possible only through deployment of innovative ways for risk mitigation and resilient design of the systems. Some examples of engineering innovations are as follows:
Smart Grids: Efficient Energy Distribution – aims towards energy optimization, low wastages and thereby reducing the impact of global warming.
Hyperloop: high-speed transportation system for both passengers and freight; thereby Revolutionizing Transportation with minimal carbon foot print.
Solar Impulse Plane: designed to remain airborne day and night without using a drop of conventional fuel. A Journey toward Sustainable Aviation!
Ocean Thermal Energy Conversion (OTEC): use of temperature difference (of at least 20° Celsius) to power a turbine to produce electricity. Warm surface water is pumped through an evaporator containing a working fluid. The vaporized fluid drives a turbo-generator. Tapping into the Kinetic Energy within the Ocean – another innovation towards non-conventional energy.
Flexi-Wings: Adopting Nature’s Design for Wind Turbines! Classical wind turbines are designed to operate within a narrow zone centered around their optimal working point. This limitation prevents the use of wind mills at variable wind. A new type of bio-inspired wind turbine using elastic blades has been developed.
2.0 Resilience in a regulated Industry like Power & Energy:
Resilience is a subset of Reliability. Power and Energy industry needs to be built and operated with the focus on resilience. This calls for sustained efforts and close co-ordination between the industry operators, the Regulators, the Policy making Government bodies, Central and State Governments and the local bodies, responsible for governing the Regulation. This may need change in every aspect of designing, operating and regulating the sector. Many entities in the electricity industry confuse Resilience as a synonym for Reliability which is totally incorrect. By focusing on reliability as a proxy for safety and resilience, the susceptibility and vulnerability of the network and systems to fall prey to disasters does not change. Therefore, unless an approach focused on Resilience is undertaken by all the stake holders, the energy sector will continue to be more and more open to the risks and disasters of the approaching era, causing untold damage to the infrastructure, consumers and their livelihoods and the environment.
As regards to the Electrical Power sector, decisions on building and maintaining our power network need to be based on the consideration, of 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, reliability considerations may improve the protection to some extent but focus on Resilience reduces the residual damages arising out of disasters.
3.0 Reliability in Electrical Power Distribution
Various indices are used to monitor and measure the Reliability. Power Reliability by the Distribution companies can be understood through the following indices:
1) SAIFI (System Average Interruption Frequency Index) is the average number of interruptions that a customer would experience and is calculated as, where is the failure rate and is the number of customers for location. In other words, SAIFI is measured in units of interruptions per customer.
SAIFI = (Total number of sustained interruptions in a year) / (Total number of consumers)
2) SAIDI (System Average Interruption Duration Index) is the average outage duration for each customer served, and is calculated as: where is the number of customers and is the annual outage time for location, and is the total number of customers served. In other words, SAIDI is measured in units of time, often minutes or hours.
SAIDI = Total duration of sustained interruptions in a year / total number of consumers
SAIFI & SAIDI are the most used pair of reliability indices
3) CAIDI (The Customer Average Interruption Duration Index) is a reliability index commonly used by electric power utilities. It is related to SAIDI and SAIFI, and is calculated as, where is the failure rate, is the number of customers, and is the annual outage time for location.
CAIDI = Total duration of sustained interruptions in a year/total number of interruptions
It can also be seen that CAIDI = SAIDI/SAIFI
4) CAIFI (Consumer Average Interruption Frequency Index) is the average number of interruptions for consumers who experience interruptions during the year. It is the ratio of the annual number of interruptions to the number of consumers affected by interruptions during the year. Consumer is counted only once regardless of the number of interruptions.
CAIFI = Total number of sustained interruptions in a year/Total number of consumers affected
5) MAIFI (Momentary Average Interruption Frequency Index) is the average number of momentary (less than 5 minutes) interruptions per consumer during the year. It is the ratio of the annual number of momentary interruptions to the number of consumers.
MAIFI = (Total number of momentary interruptions in a year) / (Total number of consumers)
None of these indices 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.
4.0 Natural Events vis-a-vis Power Reliability:
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:
o Increased intensity or frequency of events historically typical to a given area
o Instances of historically atypical events in an area
o Longer term trends (e.g., higher average temperatures impacting ratings)
o Impacts on supply chain due to geographically larger events
Power 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.
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 have already included the MEDs and have additional measures in place for resilience. In India where the Regulatory reforms are already well in place, such progressive step needs to be taken by the Forum or Regulators for introduction in the Regulations of State Electricity Regulators.
With climatic changes impacting countries around the world, it becomes harder to argue that these are one-off occurrences. Wild fires in California, Tonardos in Tennessee, coastal storms in Texas, earthquakes in Himalayan areas, Tsunami in Indonesia and Japan have taught lessons to the affected utilities and their governing bodies. However, these disasters cannot be termed as one-off or” typical to one area” kind of disasters and the universal awareness for risk mitigation and resilience needs to be built in the systems world over. 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.
Devastating Impacts like wildfires occur in a changing climate which is showing longer droughts, higher winds and more frequent extreme weather events. Hence, fire risk should also be included, due to its high consequence.
Strangely, the output from wildfires was 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.
5.0 Power-line-initiated wildfires
Weather-driven events are by far the more common producers of damage to power equipment that leads to power flashes. Extreme weather often results in downed power lines and toppled utility poles triggering short circuits that sometimes cascade into massive and widespread power outages.
There are many other ways that utility lines, particularly high-voltage lines, can spark fires. If tree branches are within arcing distance of the lines, electricity can arc between the line and the tree. Old equipment can set off sparks. If the weather gets really hot, power lines can sag and touch dry grass or trees. Under these conditions, even a small spark can initiate a wildfire which can subsequently lead to a widespread catastrophic wildfire. Whilst power-line wildfire starts account for roughly 2 – 5% of all wildfires, power-line-initiated wildfires have accounted for over 80% of deaths associated with wildfires in Australia over the last 50 years.
6.0 Role of Renewable resources:
Distributed power generation from New and Renewable Energy Resources, supplemented by statutory grid back up will effectively provide high level of Resilience to the power distribution systems. Resilience level of the local system as well as that of the interconnected grid will get positively impacted by such measures. However, interstate as well as intrastate transmission network should be suitably augmented and State level as well as Regional level Load dispatching system should also be suitably geared up.
7.0 Conclusion:
Various indices are now available to the utility companies. Use of only one set of indices may not represent an appropriate scenario. Hence, multiple sets of indices, often may be in combination, shall be used through the Regulatory Reforms channel to portray the correct picture of system Resilience and Reliability.
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