How Australia Came Close to Wide-Scale Blackout – And Insights Into Energy Storage for Grid Resiliency
October 01, 2018 | Aung Thant, Power Systems Engineering Architect
A few weeks ago in Australia, a dramatic lightning strike nearly caused a wide-scale blackout.
In this post, I take a look at how Australia’s grid was able to recover from the strikes and explore energy storage systems as a critical tool in the grid engineer’s toolbox for helping keep the grid stable in the face of unpredictable events.
When lightning strikes
They say lightning never strikes the same place twice. In the rare event that took place in Australia recently, lightning did strike twice in the same place: it simultaneously struck the same phase on two transmission tower circuits. As a result, the high voltage interstate transmission line between Queensland and New South Wales (NSW) tripped to clear the fault, and within 50 seconds the Heywood line from South Australia to Victoria tripped.
South Australia and Queensland became isolated, NSW lost around 800 megawatts of power that it receives from the north, and Victoria lost about 280 MW that it receives from South Australia. Two aluminum smelters lost hundreds of megawatts of power, which affected their production for about an hour. Around 45,000 customers across Sydney lost power, and trains were delayed.
Despite this freakish act of nature and the resulting power losses, Australia’s grid held up extremely well thanks to intelligent system design and its built-in self-preservation mechanisms.
A self-healing grid
After the two major lines tripped, about 60 MW of fast-start hydro capacity went online within a few seconds, followed by another 150 MW a few minutes later to compensate for the decrease in generation. This quick-start hydro plant is one form of the grid’s self-protection strategy.
Another self-protection strategy is the grid’s ability to shed loads in order to protect more critical loads from being disrupted, like hospitals and schools. In Australia’s case, loads shed included an oil refinery, which took six days to get fully back online, and 50 MW of load in Tasmania.
Australia’s grid frequency must be maintained at 50 hertz. The lightning strikes caused the frequency to fall to 49.0 hertz. One hertz doesn’t seem like much, but when it comes to grid frequency, it is a major event that can cause severe cascading outages.
The shedding of loads, the quick-start hydro plant and the intelligent response of major power stations to reduce or increase their output until other generation sources came online all helped to keep the grid relatively stable. If it weren’t for these "self-healing" mechanisms, Australia’s grid could have experienced a wide-scale blackout similar to what New York experienced in 2003. It’s called a cascading effect, when one line trips and causes the remaining system to become overloaded, and then trips begin to occur in a domino effect, taking out power in a catastrophic failure.
Thankfully, this did not occur in Australia’s recent event. From an engineering perspective, the situation turned out well due to a carefully designed system.
But there is always room for improvement, and Australia’s power utilities are analyzing the system’s performance to learn how they can better secure the grid, since some aspects performed as expected and some didn’t. It’s a complex system, and with the mind-boggling number of events that could cause grid disruptions, it’s important for utilities to implement various strategies for grid resiliency.
Grid energy storage: A tool in the grid engineer’s toolbox
Faults and the intermittency of renewable energy causes imbalance between generation and load, resulting in system frequency excursions. A grid energy storage system based on ultracapacitor (supercapacitor) or battery storage can instantly come online and reduce or eliminate the imbalance, thus restoring frequency and preventing further frequency-related events. Depending on the size of the energy storage system, it can bridge the power gap for a few seconds to a few minutes. Energy storage buys extremely valuable time for the slower generation assets to respond, such as hydro (which benefits from a minute of lead-time) and diesel backup generators (which can come online in about 15 to 30 seconds, depending on the age of the machinery).
When grid engineers are considering adding an energy storage system to their toolbox of solutions, it’s important to consider the advantages of both ultracapacitors and batteries.
The Financial Review article covering the Australia blackout story mentioned that when the power outage occurred, South Australia’s Hornsdale Power Reserve, which is the site of a Tesla battery energy storage system, discharged 40 MW into the grid, helping to reduce or prevent load loss in South Australia. This is an excellent example of how grid energy storage systems are among the critical tools an engineer has available to ensure the highest stability possible.
Ultracapacitor energy storage systems specialize in rapid release of high power. In terms of cost-effectiveness and system efficiency, an ultracapacitor system is optimal for grid energy storage supporting a seconds to 1-minute timeframe. Ultracapacitors do not store large amounts of energy as batteries do, so their area of specialty is in high power, rapid response for short windows of time; and they perform this function with ease compared to batteries. Seconds of high power goes a long way in stabilizing the grid after a fault. Further, ultracapacitors are inherently a low maintenance technology not requiring replacement cycles.
Current battery systems have the ability to respond as fast as ultracapacitor systems, however, battery systems have to be oversized by approximately three to five times to provide the same amount of power as ultracapacitors for short duration applications. A 60 MW battery is a costly system if developed for the sole purpose of primary frequency response because the battery has to discharge its reusable energy fully within a few seconds. That’s an extraordinarily high C-rate and places great strain on the battery system.
A note on renewables and inertia
Conventional synchronous generators have rotating mass spinning synchronously with grid frequency. Seconds worth of energy is stored in those rotating masses and is naturally extracted when the grid frequency declines. Renewables, such as wind and solar, do not have such inertia or reserved energy. As the grid faces the introduction of more clean, renewable energy, the deficit of inertia must be addressed. Energy storage systems based on ultracapacitor and battery technologies can provide what’s called synthetic inertia by rapidly injecting power into the grid to limit the magnitude and the rate of change of grid frequency.
The lightning strikes on Australia’s grid showed us that a symphony of grid strategies, including backup hydro, generator ramp-up, demand response and load shedding, prevents a bad situation from becoming catastrophic.
It also showed us that it’s possible for some aspects of the grid system to not respond in the way we would expect. Operators and utilities come out of these events asking questions such as, how can we better prepare for the worst-case scenarios? What can we do to patch up the areas of our system that need more reliability?
One answer is that energy storage, in the form of ultracapacitor or battery systems, is a robust solution for stabilizing the grid with more control. Smart system design would deploy ultracapacitors for short-term, high power requirements and batteries for long-term energy storage.
When lightning strikes again, what will your strategy be?
Power Systems Engineering Architect
About this author
Aung Thant is a seasoned power systems engineer currently performing advanced architecture and designs, modeling and simulations of energy storage utilizing Maxwell’s ultracapacitor grid modules and commercially available advanced batteries. He works with utility, developers and C&I customers to identify the best strategic approach for their energy storage requirements, which may include a stand-alone ultracapacitor ESS or a hybrid ultracapacitor-battery ESS system. Thant received his education from New York University – Polytechnic/Tandon School of Engineering with BSEE and MSEE degrees in electrical engineering.
Maxwell’s Grid Energy Storage System
Energy storage systems help balance grid events like the one caused by lightning strikes in Australia.
When a line trips due to a fault on the grid, there is an imbalance in the load and generation, causing the frequency to deviate. Maxwell’s Grid Energy Storage System, based on its proprietary ultracapacitor technology, detects the frequency change and injects or absorbs power to slow down the change of frequency. The system is a short duration, high power source that fills the power gap, allowing slower grid assets the time they require to come online.
Maxwell’s Grid Energy Storage System is featured in the Siemens SVS PLUS FS, a transmission system designed to stabilize voltage and frequency.
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