Czech grid operator ČEPS conducts extraordinary inspection of 370 km of lines, finds damage to V412

Transmission system operator ČEPS found damage to the V412 line during extraordinary inspections of key power lines. The line connects the Ústí nad Labem and Central Bohemian regions and Prague. The cracked insulator string did not affect grid operations. Technicians will repair the fault next week. In total, the state-owned grid operator inspected more than 370 kilometres of lines. ČEPS spokeswoman Hana Klímová told the Czech News Agency (ČTK) today. The damaged line was not connected to the recent widespread power outage in the Czech Republic, the company said.

ČEPS carried out the extraordinary aerial inspections using thermal imaging in response to the extensive power outage on Friday, 4 July. According to Industry and Trade Minister Lukáš Vlček (STAN), around one million customers were left without electricity. There are 6.3 million electricity supply points in the Czech Republic.

During the extraordinary inspections, the grid operator focused specifically on line V411, whose outage caused by a fallen phase conductor was one of the main causes of the problems at the time; line V412 between the Hradec and Řeporyje substations; line V420 between Kadaň and Havlíčkův Brod; and line V208, which runs through the Central Bohemian Region and Prague.

"The flight operator visually identified a cracked insulator string in a three-string tension assembly on line V412. This type of fault occurs only rarely on transmission system lines and is usually identified during foot patrols, climbing inspections or aerial inspections. The repair is scheduled for next week," Klímová said.

ČEPS also identified other findings on lines V420 and V411. These were not urgent, however, and will be repaired during planned outages for routine line maintenance.

ČEPS is also continuing to analyse the causes of the extensive power outage in early July. The fallen conductor is currently being assessed by police experts, although this is standard practice in similar cases, according to Klímová.

She said the investigation is also being conducted internationally, through the European Network of Transmission System Operators (ENTSO-E). "A preliminary report is expected within six months, and a final report with any corrective measures within 12 months," Klímová added.

According to information previously released by ČEPS, the main mechanical cause of the outage on 4 July was the rupture of a phase conductor, which carries electricity between power plants and substations. This took the backbone V411 line out of service. The line is used to evacuate high volumes of power from power plants and transmit electricity over long distances. The Ledvice power plant unit in the Teplice area and the large Krasíkov substation in the Ústí nad Orlicí area then went offline. The dispatcher also switched off line V208, which connects substations, due to the heavy load.

ČEPS ruled out grid overload caused by power flows or damage caused by a third party, saying the system had been operating reliably before the outage.