Blackouts: Is Sri Lanka suffering alone?

By Dr. Tilak Siyambalapitiya

On Monday 17th August 2020, at 12.35 pm, Sri Lanka experienced the fifth countrywide blackout in recent memory. Probably, it was around 10.30 pm that night when all customers were reconnected to the grid. In my article ,”The Anatomy of a Blackout” in The Island on Wednesday, 19th August 2020, I explained how a grid operates in dynamic equilibrium and what protection mechanisms are there to save the grid from a total collapse. Why those systems failed to arrest a grid failure, on the 17th, would hopefully be explained by the investigating team of the Ministry of Power.

Today we ask the question: are we alone in the world, when it comes to frequent national blackouts? Do we have more or fewer blackouts compared with our neighbours? How about blackouts in advanced economies? This account is inno way justifies the five blackouts in Sri Lanka in recent memory, but presents a small subset of hundreds of diverse blackout events that happened in other countries.

United States

The Northeast blackout of 2003 is considered to be the worst blackout in the history of North America. The previous major blackout was reported in 1977, affecting New York City. . It was the summer peak in the northern hemisphere. On 14th August 2003 at 3.05 pm, a 345 kilovolt transmission line carrying a heavy current sagged as it is designed to do so, but the sagging line got too close to a tree. The heavy current failed to sound the alarm and the sagging line finally touched the tree. The first ring of protection recognized the line has touched a tree, and switched the line off, automatically. Controllers failed to recognize the root cause and another transmission line, now carrying the current of the first line that switched off, tripped 30 minutes later. A third line tripped in a further 15 minutes. Loss of three important lines caused the “dynamic equilibrium” to be lost. In some areas there were more customers than electricity produced; in others, there was more electricity production than what customers wanted. Lines that pass extra power in one region to another were already dead. A cascading failure of more lines and generators resulted. The disturbance spread to neighbouring Canada, too. Over 60,000 megawatt of customer electricity supply was interrupted when over 500 power plants stopped working. About 50 million people in the USA and Canada were affected for two days, as controllers struggled to restore power. Electric trains, industries, businesses, and homes were badly affected. The economic impact was estimated to be $10 billion.

Southwest blackout of 2011, in the USA, is considered to be the largest blackout in California. Power was interrupted for around 12 hours on September 8, 2011, affecting 2.7 million customers. The main reason was identified to be the dependence on power imports from Arizona at the time. Imports to California were approximately 2,750 megawatt, just below the limit of 2,850 megawatt. On that day, generation and transmission lines had been taken out for maintenance, with approval, but the shortage meant the California grid was running on a thin margin.

Brazil

Itaipu, until recently was the world’s largest hydroelectric power plant, shared by Brazil and Paraguay. Itaipu power plant stopped at 10.20 pm local time, on 10th November 2009, causing more than 190 million people to lose electricity. The power outage was not resolved for more than two hours. It is reported that heavy rains and strong winds caused three transformers to short-circuit, resulting in cutting the line and automatically losing power transmission. Brazil’s grid operator later confirmed that the failure of a 345-kilovolt line was provoked by the pollution of insulators due to deposits of soot.

More recently, a failure in the transmission network led to a large area blackout in Brazil on March 21, 2018. It started at 3.40 pm and some parts of the affected area regained power 20 minutes later while others took a much longer time. The problem was because of chain reactions caused by the protection of a circuit breaker which was inaugurated three months before the incident. It affected around 10 million customers and 18,000 megawatt was lost. The main causes were identified later as lack of necessary stability analysis before the event, defects in security control, maloperation of protection, and unreasonable configuration of the third line of defense.

India

Two severe backouts occurred in succession on 30th and 31st July, 2012. India operates six regional grids, most of them interconnected by strong transmission lines. At 2.35 am on 30th July, a circuit breaker on a 400 kilowatt transmission line, tripped, disconnecting the northern regional grid from the rest. About 32 hours later, a similar disturbance emerged. There was an unprecedented increase in agricultural demand in the northern region and a power surplus in the western region. Two transmission lines were already disconnected for maintenance and this situation exerted extra pressure on the available two lines, one of which was already carrying power at its capacity limit of around 1,000 megawatt. This line collapsed causing the first power outage on 30th July. Even after this, no proper steps were taken to balance the demand in the northern region or to curtail the generation in the western region. Instead, power from the surplus western region detoured via the central and eastern states to reach the deficit northern region. Even though the third level of protection with under frequency relays functioned properly, reports indicate the utility was under tremendous political pressure to continue drawing power from the grid.

The 30th July blackout affected over 300 million and a day later, the 31st July blackout affected 620 million people. An estimated 32,000 megawatt of power was lost. The 31st July 2012 blackout is considered to be the largest power outage in the history of India. Electricity service was restored between 31st July and 1st August 2012, a full 10 days after the blackout.

United Kingdom

The largest blackout, since the great storm of 1987, was reported on 28th August, 2003. A large portion of the UK grid went off at 6.30 pm and was restored in most of the places half an hour later. The initial cause was identified as a failure in a transformer at Hurst substation, near Bexley, due to an oil leak. A second fault occurred seven seconds later forcing the underground cable between New cross and Wimbledon stations to trip as automatic protection equipment identified and thought there was a fault. Later it was revealed the protection device on the transformer had the wrong rating.

Another, blackout across the UK, happened more recently, on 9th August 2019. Two large power generators (Little Barford gas-fired power plant and Hornsea offshore wind farm) disconnected from the system, causing the frequency to drop below safe limits. Little Barford power plant tripped shortly before 5.00 pm due to a technical issue. The outage was followed minutes later by the unexpected shutdown of the Hornsea wind farm. The demand at that time was 28,995 megawatt. The combined loss of power from two power plants added to 1,136 megawatt representing 4% of demand at that time. One million customers were affected. Over 500 train services were canceled or stranded. Power was restored from 45 minutes onward.

Argentina

This power outage happened on Sunday, 16th June 2019, at 7.06 am. It affected around 50 million people in Argentina and parts of Uruguay and Paraguay. Much of Argentina had heavy rainfall over the weekend and Uruguay’s utility reported some parts of their system were damaged by rain. A 500 kilovolt line in Argentina, from Colonia Elia to Campana was under maintenance. The company bypassed the line on maintenance using a nearby overhead line but missed to alert the automatic generation shutdown system which is designed to alert generators of network changes that would require to lower generation. Further, it was identified lack of coordination led to the propagation of failure. By 10.30 pm, almost 15 hours after the outage, power was restored throughout Argentina and most of Uruguay.

Bangladesh

The national grid of Bangladesh tripped two times on 1st November 2014. It tripped first at 11.30 am. Reports show the reason was excessive electricity imports from India. The power supply was partially restored from 2.50 pm., but it again collapsed at 4.30 pm on the same day. India normally delivers 250 megawatt to 350 megawatt to Bangladesh, but on that day, India had supplied 444 megawatt power to the substation. The outage affected about 100 million people in Bangladesh. Power was restored for half of the coverage area by 9.30 pm, 10 hours after power was lost.

Turkey

A power outage, affecting 70 million people, occurred in Turkey, on March 31, 2015. Four 400 kilovolt lines were not in operation at that moment. Parallel lines in service were carrying around 4,700 megawatt. One transmission line which was carrying 1,127 megawatt tripped on overload causing loss of synchronism between the Eastern and Western subsystems. Within 1.9 seconds, all parallel lines were disconnected. It took 6.5 hours to restore supply to 80% of customers.

Venezuela

This blackout is considered as one of the longest blackouts in history. It happened on 7th March 2019, affecting 30 million people. Analysts and engineers identified the event as a result of years of underinvestment in a network that had been mismanaged and neglected. It started at 4.45 pm on March 7, 2019, which lasted through March 14, a full week.

It should be noted that the above are not the only blackouts in the world. There were numerous blackouts in other countries that were not adequately reported.

Sri Lanka:

At 1.30 am on 9th October 2009, a transmission line carrying currents well within its limits was severed inside the Kelanitissa substation, with the two stubs of the broken line falling within the substation premises. A fire ensued, which finally caused all the generators to trip out within 3.5 seconds. The entire country was without power. A complete restoration was reported by mid-day, almost 9 hours after the line fell on the ground.

Sunday, 27th September 2015 was a Poya Day. Most parts of the country were experiencing rainy weather and the temperature in the night was lower than on a normal September day. At 11.53 pm, one generator at Lakvijaya power plant tripped, causing a cascading failure of generators. While restoration was going on, at 1.10 am on 28th September 2015, the grid collapsed again, causing restoration to be delayed. The power supply was fully restored by 4.02 am on 28th September, 4 hours after the grid collapsed.

At 1.52 pm, on 25th February 2016, a blackout occurred in the Sri Lanka grid. A lightning strike on the 132kV Seethawaka – Kolonnawa transmission line was the initiating event. Restoration of Colombo was completed in 1 hour and 40 minutes, but the total time taken to restore the entire grid is reported to be 3 hours and 20 minutes.

On 13th March 2016, the grid failed and is widely considered as the longest blackout of all recent events.

And on 17th August the grid failed again, for the fifth time in recent memory.