The drone entered Estonian airspace from the Russian side of the border and is thought to have been a Ukrainian drone taking part in the mass strikes on the port of Ust-Luga. Had it hit a nearby substation, instead of the chimney at the Auvere plant, 3 kilometers from the Russian border, the damage would likely have been much greater.

While a power station may remain partly or even completely intact after a drone strike, if a smaller substation gets knocked out, this will cut off electricity transmission to consumers.

The 330-kilovolt Viru substation is located just a few hundred meters from the Auvere power plant, just a couple of kilometers from the Narva River, which marks the eastern border.

Former Estonian Defense Forces (EDF) commander Martin Herem said that Russia's strikes on Ukraine's own energy system last year focused principally on 330- and 150-kilovolt substations, rather than larger generating power stations.

"They didn't target power plants much. I'm not an energy expert, but you can fairly quickly set up a diesel power plant somewhere and start supplying electricity from there. We do have wind turbines and solar panels near Tootsi, for example, but the residents of Tootsi wouldn't obtain a single bit of electricity from them if the substation is destroyed. Rather than dismantling production, the distribution network is more vulnerable," Herem said.

Herem's successor as EDF chief, Lt Gen. Andrus Merilo, told Wednesday's edition of "Esimene stuudio" that if war were to reach Estonia, the Auvere plant would be essentially indefensible regardless of how many resources were devoted to defending it.

Herem agreed. "I have said at the government level that we should not build things within 40–50 kilometers of the eastern border if we are afraid of losing them. Within that zone, they are relatively easy to destroy. Beyond that, it becomes harder," he said.

Estonia has a total of 15 substations like the Viru facility operating at 330 kilovolts, nationwide. While the Viru substation is right next to the Narva River, the Püssi substation (pictured), still in Ida-Viru County, lies exactly 50 kilometers from the river.

Herem said that when preparing for war, these types of substations should be moved underground, drawing on Ukraine's experience. "The Ukrainians have also said this: Everything within 50 kilometers of the state border should be moved underground. I understand it's very expensive, but these are highly vulnerable," Herem said.

The EDF commander said he was unaware if Ukraine has actually moved any substations underground, but he has observed how they have been partly reinforced with concrete: The core of the substation — the transformer — is surrounded by a half-meter-thick concrete wall, topped with metal beams and concrete panels.

"This protects against multiple strikes by Shahed-type drones carrying warheads of up to 100 kilograms. It wouldn't help much against a cruise missile, but it would certainly mitigate the damage. The accuracy of an Iskander is considered to be about ten meters — if it misses by 10 or even 20 meters, the wall is definitely useful, as the blast wave and shrapnel won't reach the target," the former commander said.

Elering: Underground substation would cost €100 million

Meanwhile Hannes Kont, head of crisis preparedness at Elering, said that moving a larger substation underground could cost about €100 million. By contrast, reinforcing key above-ground elements, such as encasing a transformer in concrete, works out at a fraction of that cost, at approximately €5 million.

Elering says it plans to partially reinforce an unspecified number of substations over the next four years, for example by surrounding transformers in some substations with such concrete "sarcophagi."

A transformer is the most important component of a substation, adjusting voltage to the optimal level needed to transmit electricity over long distances. With more powerful substations, a transformer can be roughly the size of a house, while in a 110-kilovolt substation it is more like the size of a train loco. As well as being the heart of the substation, the transformer due to its makeup is also its most vulnerable part, filled as it is with highly flammable cooling oil.

While there are no plans to move substations underground, Kont confirmed the goal is to strengthen them so they are better protected against sabotage and lighter drone attacks.

The government has however set no objectives for companies like Elering, nor for electricity and heat producers or water utilities, to prepare for full-scale war or conflict.

However, the electricity grid is more vulnerable, Kont said. "Because the electricity infrastructure is so large and open — spanning air, land, and sea — we can never fully protect it. Consumers would not be willing to pay for a system entirely encased in reinforced concrete or placed underground. Consequently, we will have to assume that some part of the system may fail, but it is designed so that even if one or two key elements fail for any reason, the system will continue to operate in peacetime," Kont said.

Kont explained that the goal is to design the electricity system with sufficient reserves and buffers.

Jaanus Uiga, Deputy Secretary General of the Ministry of Climate, said the grid is prepared for a single substation being knocked out.

"Our main grid is built on the principle of ring supply — if one substation fails, which can also happen due to a normal fault, the system is prepared for it. A single element does not affect the operation or capability of the system to deliver electricity from controllable power plants," Uiga said.

Elering to spend €220 million on grid protection

Elering says it plans to spend €220 million over the next four years to better protect the grid, nearly a quarter of which, €50 million, is EU funding which has to be utilized by 2029.

Kont noted the investment will primarily go toward countering hybrid threats. Grid resilience will be strengthened against threats originating from land and air, while Elering will ensure it has sufficient reserves of critical components to quickly restore operations if an object is hit.

One of these critical components, as seen in the Ukrainian experience, is the transformers themselves. Kont said he could not disclose the size of Elering's transformer reserves, for security reasons, but did say: "We are moving toward having a certain level of reserve and buffer, but we do not describe where it is located or how it is created."

Eesti Energia tight-lipped on how new gas plant will be defended

Energy Minister Andres Sutt (Reform) told "Aktuaalne kaamera" Thursday that the state does not intend to obstruct generator Eesti Energia in its plan to build a new 100-megawatt gas power plant adjacent to the Auvere plant. This is planned for the next two years.

Last November, Eesti Energia subsidiary Enefit Industry—owned by Eesti Energia signed a €100 million turnkey contract with Israeli companies Baran International Ltd and Baran Group Ltd to build a hydrogen-capable thermal power plant.

ERR asked Eesti Energia what, if anything, it had learned from this week's drone incident, in the context of planning the new gas plant in Auvere. The company declined to discuss publicly matters related to the security of its power plants.

Eesti Energia CEO Andrus Durejko issued a written response stating: "We will not be elaborating on specific measures. Broadly speaking, these involve who we recruit, staff training, our cybersecurity solutions, physical security, continuity measures, cooperation with state authorities etc."

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