“Historic moment”: 210 MW from Chaira PVPP are back in the grid

Nearly three years after it went out of service, the Chaira Hydroelectric Power Plant is gradually starting to supply the Bulgarian grid network. Its only repaired hydro unit – Number 2 (XA2) – is already operating at 130 MW in generator mode. The plant completed its tests a few days ago, and on Monday the working unit was demonstrated to Prime Minister Dimitar Glavchev, Minister of Energy Vladimir Malinov and journalists.

Malinov described the moment as "historic", as the plant had been out of commission for nearly three years. The hydropower unit has a maximum capacity of 210 MW, though it can currently reach only 205 due to the water level in the Belmeken reservoir. In pumping mode, XA2 operates at a maximum of 197 MW.

We expect the price pressure to decrease, that is, to increase supply during peak hours, when there is the greatest need for electricity," explained Martin Georgiev, CEO of the National Electricity Company.

The repair of hydro unit 2 took about a year – three months of testing and research, then a “unique” technical solution was developed, and the repair itself continued for ten months. The last month was spent testing the facilities to ensure that the repair was successful.

During the repair, a modification was made to the turbine stator columns – the component that failed the tests in hydro unit 4. Their shape was changed so that the pressure inside would be distributed more smoothly, and not concentrated in the critical areas.

The repair cost is unclear, as it was a continuation of the confidential contract signed with ABB-Voith. However, Georgiev said the budget for the restoration was “competitive.”

After the repair, hydro unit 2 will be able to operate sustainably for at least 5 years and "will certainly be able to overlap with the period of complete replacement of two of the hydro units, which is the most long-term sustainable solution."

We must remember that this facility has been operating for many years, and quite actively at that; it has done a lot of good for the energy supply system and will continue to do so," said Georgiev.

A similar solution will be applied to hydropower unit 3, which is expected to be operational by the end of 2025. The dismantling of its turbine part will begin in mid-January.

Everything is done with extreme caution and attention, and the main goal is to avoid any risks to the facilities and, above all, to people," said Georgiev.

The negotiations that NEK is conducting with the original equipment manufacturer - Toshiba regarding a medium-term solution for the repair of hydro unit 1 are in an advanced phase, Malinov explained. They are being conducted per the Memorandum of Cooperation in the field of energy signed in September between Minister Malinov and the Japanese Minister of Economy, Trade and Industry, Ken Saito. Following the final approval of the draft agreement by Toshiba, the expectation is that it will be signed by the end of the year.

Chaira Hydroelectric Power Plant is the largest underground power plant on the Balkan Peninsula, located under the Belmeken Reservoir. The power plant has 4 hydropower units (HP) with a total capacity of 864 megawatts in generator mode and 788 megawatts in pump mode. The total installed capacity of the Chaira Hydroelectric Power Plant is comparable to one unit of the Kozloduy NPP. The power plant operates as a battery using a renewable source (water) and plays a key role in the security and balancing of the Bulgarian grid network.

Translated by Tzvetozar Vincent Iolov