Inside Ukraine's wrecked power plants amid unprecedented Russian attacks: Reporter's notebook

Ukraine's largest private energy provider said it fears that "ruthless" missile and drone assaults by the Russian military will continue on the country's power plants.

The country is now racing to repair some of the widespread damage to several facilities after Moscow carried out a series of unprecedented attacks on Ukrainian energy infrastructure in recent weeks.

Russia destroyed 80% of Ukraine's thermal power plants in those attacks, according to Ukrainian Prime Minister Denys Shmyhal, in an interview with Estonian broadcaster ERR.

ABC News was granted access to some of the power plants that have suffered extensive damage.

A pungent burnt smell hits you as you enter each facility.

One of the plants visited was completely destroyed, with damage visible across the huge Soviet-era site. Even the engine and control rooms, the heart of the plant, were wrecked in the attacks.

Darkness reigns throughout each site; the irony now is that these megalithic structures that should power millions of homes cannot even provide light for themselves.

In the wake of successful Ukrainian drone attacks on oil refineries in Russia earlier this year, the Kremlin launched its most vicious campaign yet on Ukraine's critical infrastructure.

Throughout the past year, the Russian military had largely given up its attacks on Ukrainian power plants, in favor of trying to target Ukraine's growing domestic arms production and other more valuable military sites.

Now, Moscow has reverted to its tactic of trying to cripple Ukraine's energy grid, which is vital for the country's economy.

In the past two weeks alone, Russia has launched about 300 explosive attack drones and approximately 190 different missiles at Ukrainian energy sites, according to ABC News' analysis of daily Ukrainian Air Force reports.

"The enemy's relentless assaults [now] occur nearly every day," said Volodymyr Kudrytskyi, from Ukraine's state energy company Ukrenergo.

Kudrytskyi described the frequency of Russian drone attacks on energy facilities nearer to the front lines as "alarming," adding that the extensive damage to multiple Ukrainian thermal and hydroelectric plants had "disrupted" the country's energy grid's equilibrium.

According to officials in Ukraine's energy sector, Ukraine has moved some of its air defense assets to strategically protect other sites, such as weapons manufacturing facilities -- meaning the country's ability to defend many of its power stations is limited.

There is also clear evidence that Ukraine has, at times, deployed some air defense assets closer to the front lines to target Russian aircraft.

At a NATO meeting in Brussels on Wednesday, Ukrainian Foreign Minister Dmytro Kuleba said his country is lacking air defense systems, particularly sophisticated U.S.-made Patriots.

In the spate of recent attacks, Russia has damaged about a dozen Ukrainian thermal power plants and at least four hydropower plants, according to officials.

On March 22, in the largest Russian attack on Ukrainian energy infrastructure of the entire war, Ukraine's largest private provider, DTEK, lost nearly three-quarters of its overall generating capacity, the company said.

DTEK CEO Maksym Timchenko told ABC News it has never been this bad, with the company now operating at around 20-30% of its normal output.

As the weather has gotten warmer in Ukraine and the heating season is over, the country is still not generating enough power to meet the overall demand from consumers, meaning there are rolling power cuts for millions of people in several regions.

Engineers and maintenance crews at DTEK's plants are now tasked with clearing vast amounts of debris from the missile strikes. The usual routine is on hold, but some employees must remain on-site, taking cover in the facility's bomb shelters, in the case of an attack.

Complex electrical infrastructure that's uncrewed can be even more dangerous if it is hit by a missile, explained Volodymyr, a DTEK worker. All DTEK workers who spoke with ABC News did not want to provide surnames for security reasons.

During one attack, he told ABC News that he and his colleagues were unable to reach the bomb shelter in time and were lucky to survive.

Oleksandr, another DTEK worker, said the Russian attacks have become increasingly accurate.

In previous attacks, the Russians hit equipment on the periphery of a plant, he said.

Now, they were successfully striking core facilities, such as the engine room, which is vital for the plant's overall operation, he added.

Officials at the plant said it would take months or even years to repair the damage. Their ability to carry out repairs is also hampered by a shortage in the supply of specialist parts.

Ukraine faces an inevitable dichotomy: As soon as a power plant is repaired, there is the risk Russia will target it again.

Oleksandr said it took him and his colleagues a year to repair one unit in the plant. It worked for a month and half, he said, before a missile hit it again.

"We are afraid of new attacks," said Vasyl, another worker at a DTEK power plant who described the Kremlin's new campaign as "terrifying."

"Without energy, production will just stop, everyday life will stop, we [in Ukraine] will return to a primitive and communal life," he told ABC News.

The glimmer of hope for Ukraine is that three out of its four nuclear power plants are still operating. In total, those power plants produce around half of the country's energy, according to officials.

However, thermal power plants are needed to power those nuclear plants, and other energy infrastructure is needed to transfer energy throughout the grid.

Ukraine's ability to import energy from European allies is also limited because, before the war, Ukraine exported energy to the rest of Europe. The compatibility of certain infrastructure is also a problem when it comes to transferring energy to Ukraine.

According to energy provider DTEK, Ukraine's only option is more air defense to destroy Russian missiles, otherwise, the country risks losing its ability to produce power.

Timchenko said the recent spate of Russian attacks should be "a wake-up call" to Western allies.

His warning is stark: Just two or three more attacks from Russia on Ukrainian power stations and "there will be nothing [to] restore."

The result, he said, would be blackouts and an even more crippling impact on Ukraine's already war-ravaged economy.