Innovation, Persistence, and a New Beginning

“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.

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.

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.