It was 2:30 in the morning when the first call came in to the National Control Center. Everyone stopped what they were doing as the dispatch manager relayed the message.
“Operator has arrived at Ksani substation. Begin final preparations.”
Everyone quickly got back to work.
It was June 16, 2011, in the country of Georgia. A small group of engineers had gathered in the National Control Center—the room that oversees the entire country’s electric power system. And they had a plan. In 30 minutes, they were going to intentionally create blackout conditions by simulating a fault, opening a breaker, and tripping one of the most important 500 kV transmission lines in the Georgian power system.
Most people, regardless of their industry, understand what a blackout is and understand the seriousness a situation like that demands. Georgian State Electrosystem (GSE), the country’s power utility, understood this better than most. Their country had experienced two decades worth of continual blackouts. However, they had just installed a new emergency control system, and they wanted to see it perform in a real emergency.
This new system came from Schweitzer Engineering Laboratories (SEL).
Diego Rodas, an SEL engineer, paced the control room. He and his team had spent the last few months rapidly designing the emergency control system, writing relay logic, and simulating field tests, all to fit the special requirements from GSE. He knew the system and the logic were sound. But a live test on a powerful transmission line always creates a certain amount of apprehension.
The transmission line in question is called Kartli II. It’s a 500 kV line that feeds power directly into the country’s capital, Tbilisi, where over 1.5 million people live and work. It’s also part of something called “The Backbone” in the Georgian power system. If any transmission line on The Backbone goes down, the whole system goes down.
“We like to select the most critical line and the most critical situation in the network for a live test,” said Aleko Didbaridze, a GSE engineer.
If everything went well, the emergency control system from SEL would detect the intentional fault, decide where and how much load to shed, isolate the correct breaker, send a trip signal to that breaker, and prevent a country-wide blackout. All in less than 100 ms.
But if things didn’t go as planned, if the logic was wrong…
“The repercussions would’ve been pretty grand,” said Dave Dolezilek, international technical director at SEL. “The tension was definitely there.”
Inside the National Control Center, massive screens dominated the room, illuminating a display of the entire country’s power system—every transmission line, every substation, every generator, every power flow and voltage level. No matter what happened, everyone would see it.
For GSE, there was a lot of meaning attached to the outcome of this test. It was about more than whether or not the new system did its job. It was also carrying the weight of years and years of unreliable, unstable electric power in Georgia. Years of continual blackouts. Years of financial burden.
It was now closing in on 3:00 a.m. Rodas checked the relay logic one last time and nodded his approval. Operators lowered the power thresholds. All eyes focused on the control screens, and everything was momentarily quiet.
The dispatch manager spoke into the phone.
“Cut the power.”
The glowing line indicating the 500 kV transmission line Kartli II vanished.
Instantly, the control screens lit up with activity. The emergency control system was shedding load in substations all over Georgia—and the lights were still on. They had power. All of Georgia had power.
“With the SEL system, we have seen our last blackout,” said Ucha Uchaneishvili, the dispatch manager. Everyone in the control center celebrated a successful night and the turning point of reliable electric power in Georgia.
But one question looms: How did GSE come to find themselves in their National Control Center in the middle of the night with some engineers from SEL about to “pull the plug” on their most critical transmission line?
That story begins with the independence of Georgia.
In a small section of southeastern Europe, at the crossroads into Asia, sits the nation of Georgia. Rolling green hills, wind-worn villages, and a growing population are encompassed by the rugged and imposing Caucasus Mountains. In Greek mythology, these mountains are said to be one of the pillars holding up the world.
Over one million people live within the mazelike, cobblestoned streets of Tbilisi, the country’s capital, where the statue of the powerful Mother Georgia watches over them day and night. In one hand she holds wine, for those who come as friends; in the other, a sword, for those who come as enemies.
Tbilisi is a stark contrast between traditional and modern. Interspersed between space-age architecture are buildings that look like they might collapse.
This mix of old and new was no different when it came to Georgia’s power system—specifically, its substations. Next to the few newer digital relays were sixty- to seventy-year-old electromechanical relays, covered in plastic cases that had once been clear and white but now were scuffed and yellowing with age.
Georgia claimed its independence as a country in the early 1990s. Before that, it was part of a large, interconnected electric power system in the Soviet Union. When the Soviet Union collapsed, so did the interconnected system; it split.
This fractured system, combined with the aging equipment, took its toll on Georgia. The loss of interconnection led to unintentional weak spots and unforeseen consequences because there were no longer alternate sources to compensate for the outage of certain lines. The old relays had zero visibility into the rest of the power system and no way to shed load.
For over 20 years, Georgia suffered from continual blackouts, sometimes as many as 14 a year. It was a great financial and economic burden for a newly independent country.
The Backbone, a 500 kV transmission line circuit, was the main source of instability.
Running west to east, The Backbone carries electric power from the Enguri hydropower plant through the rugged Caucasus Mountains and across the country to serve the most populated area: Tbilisi.
The load demand from Tbilisi put so much strain on The Backbone that it would cause faults and trip. The system would then reroute power through a parallel 220 kV circuit, which isn't capable of carrying that much power, so it overloads. The old electromechanical relays in the surrounding substations see the overloading and send out trip signals to protect the 220 kV line from damage. However, because the system has no way to balance the load, this action cascades into a blackout.
After one of the worst country-wide blackouts in August 2010, the Ministry of Energy got involved, expressing concern over the severity of the recent events. The blackouts had compromised national security and the stability of the economy.
Immediately, GSE hired a leading consultancy firm to investigate Georgia’s power system operations, behaviors, and responses to various events and contingencies. After re-creating the conditions of the August 2010 blackout in a system study, GSE knew their main requirements. They needed their power system to detect a fault, generate a load-shedding decision, and send that decision to a mitigation device operating the circuit breaker in 100 ms or less.
“We needed someone who could provide us with these fast signal delivery times between substations across the country,” said Didbaridze. “After looking into the company, we found that SEL could provide the technologies we needed for the delivery of that trip signal in a very short, fast period.”
With less than four months to meet GSE’s deadline, SEL specified, designed, built, tested, and installed a solution called an emergency control system. It’s a concept based on decentralized, or distributed, control. It quickly stabilized the GSE power system enough to prevent the country-wide blackouts and contain any power outages to smaller areas. When the emergency control system was put to the live test, it operated in 12 ms—far below the initial 100 ms time requirement.
Once that emergency control system was in place, the challenge became how to further minimize a power outage during a fault, how to add more control, and how to add more visibility, more intelligence, and more functionality. For GSE, this meant adding a remedial action scheme (RAS).
A RAS system is based on centralized management. The controller sits in the National Control Center and evaluates the entire GSE power system every 2 ms by communicating with other devices, monitoring voltage levels and power flows, and checking for faults. In other words, the RAS system is ready to take action 500 times a second to save the country from a blackout.
With a protection system that fast, the communications network needs to be able to keep up. So GSE also got an upgraded communications network, based on the SEL ICON, that covers almost all the substations throughout Georgia. It’s fast—the message transit time between the central RAS controller and any other relay in the country is less than a millisecond.
In addition, each RAS device in the field constantly runs self-tests to communicate the health, behavior, and performance of the power system. Any time there’s a fault or other event, the SEL devices automatically generate detailed, synchronized reports for operators to review.
Once the RAS system was in place, GSE could focus on making further upgrades.
In 2014, GSE and SEL began updating ten of the most critical substations in the Georgian power system. Feeder by feeder, they replaced old electromechanical relays with new digital microprocessor relays that significantly reduce the likelihood of malfunctions and false trips.
They also began using traveling-wave fault locating (which locates power system faults within one tower span), started monitoring all of their transmission lines with synchrophasor solutions, added power oscillation detection to increase system stability, and more.
For GSE, the value of new technology goes beyond simply reducing the number of blackouts. As of 2014, GSE became an authorized transmission system operator, giving them the power to operate and plan for the development of the entire transmission grid in Georgia. They are now able to transfer energy to and from Turkey because of their new 700 MW, high-voltage dc converter station.
In recognition of their improvements, GSE was awarded Best IT Solution for Business in 2014 for the successful implementation of their SCADA and telecommunications systems. They are also now an ISO 9001:2008-certified company, which means they meet international quality standards for continuous improvement and superior performance in all aspects of business.
It all started with one transmission line test. Although seemingly small, it showed the monumental opportunities that arise through creativity and collaboration. From widespread blackouts to emergency control to total system management, GSE is taking Georgia into the future and leaving the past behind.