‘Unexpected’ frequency variation in the network in Ceará may have been the ‘root cause’ of the blackout, says ONS director

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Luiz Carlos Ciocchi explained that, in 48 hours, the report will point out the main evidence. Certainties about what led to this Tuesday’s blackout, however, should take days to reach. The general director of the National Electric System Operator (ONS), Luiz Carlos Ciocchi, said this Tuesday (15) that, so far, evidence gathered by the agency indicates that a frequency variation in the Ceará power grid may have led to to the blackout in 25 states and the Federal District. “In the Ceará region, the evidence, our assessments, data and telemetry show that, in that region, around 8:30 am, there was an uncontrolled and unexpected frequency variation. This leads us to believe that the main cause or root cause of all the phenomena that occurred could be contained there in that electrical region,” he told TV Globo. According to Ciocchi, the frequency variation refers to a kind of disturbance that occurs between the power generation and the load. Normally, the value should be close to 60 Hz. But the index was not verified this Tuesday. The disturbance that occurred in the state, according to the director, may have gradually affected a series of components of the National Interconnected System (SIN). “When you have a disturbance like this in frequency, you usually have a series of components that may be acting in the sense of causing this sudden and unexpected variation in frequency”, stated Ciocchi. “And, in this transmission system, where there are several lines of transmission and substations, which are interconnecting consumers and generators, so that this disturbance is propagated, and gradually affects other components, expanding this electrical region”, he added. Blackout hits 25 states and the DF; some cities are up to 6 hours without electricity The director general of ONS said that, for now, this is the evidence found by the agency to explain the interruption of electricity supply in the country. He did not indicate what would have been the reason for the frequency variation in the area. Earlier, Minister Alexandre Silveira (Minas e Energia) signaled that another event, in addition to the one identified in Ceará, may have caused the blackout. “One of the events already pointed out by the ONS happened in the north of the Northeast, more precisely in the region of Ceará. The other possible event has not yet been detected by the ONS”, he said. According to Carlos Ciocchi, it is still not possible to say which other disorder influenced the drop in distribution across the country. “For now, the evidence is this. Other causes will be evaluated in due course. We are working to identify potential areas or disturbances. We do not have this indication that this second cause is circumscribed to the same electrical region. Could it be. Or not, it could be in another region that was promoting these disturbances,” he explained. Load shedding system The “unexpected” disturbance in the Ceará electrical region led to a cascade effect in the interconnected system, which also affected the South, Southeast and Midwest regions. The agents responsible for transmission in these regions automatically activated the Regional Load Relief Scheme (ERAC). The measure is already planned by the system operators and serves to prevent disturbances from spreading. According to the representative of the body responsible for the coordination and control of the Brazilian electrical system, the ERAC started operating only in that region of the country. Thanks to the performance of the system, it was possible to resume, more quickly, the energy supply in these areas. “South, Southeast and Midwest was the performance of a Regional Cargo Relief Scheme. He perceives a very big disturbance arriving, he realizes that it can propagate. So, you do a preventive load cut, so that the situation does not spread to the whole region”, he explained. “You try, in a technical way, to control this disturbance that was coming from outside. It is controlled, specific and planned. So much so that, as a result of ERAC’s activities, the recomposition of cargo from the South, Southeast and Midwest was carried out very quickly. Because this is absolutely standard and normal procedure.” Ciocchi explained that, when activating the ERAC, the electrical charge is gradually minimized, in order to relieve the system, for its preservation. “The system detects it, triggers the ERAC, which has several stages. In these stages, you are taking the load off, relieving the system, so that it can be preserved. And that’s exactly what happened. The load cut in the South and Southeast was controlled and quickly recovered.” According to the ONS director, it is necessary, however, to explain why the ERAC was not activated in the North and Northeast regions, most affected by the blackout. ‘Root cause’ In a press conference, Alexandre Silveira stated that the ONS will present a report, within 48 hours, to point out the reasons that led to the interruption in the country’s energy supply. Ciocchi stated that, although the document is important, it will not be able to pinpoint the causes of the disturbance in the national electricity system. According to him, the opinion should address only the “strongest evidence”. “In 48 hours, it is our commitment to bring to society the strongest evidence, in order to identify, more closely, the origin of this problem. Normally, these major failures, like the one that happened today, are caused by a sequence of technical events, of malfunctions of several components, so that you have this situation that is significantly strong and heavy, as we had today”, he said. To find out exactly what happened this Tuesday, the ONS director said that it will be necessary to produce the so-called Disturbance Analysis Report (RAP). He did not signal how long it will take to release the document. Coordinated by the National Electrical System Operator, the RAP is developed in partnership with all the agents involved in the electrical region where the disturbance was identified, such as generation and distribution companies and component manufacturers, for example. “It’s complex. It is not done solely and exclusively by the ONS. You involve all the companies and agents that are in that area. What happened could be a failure in a device, in a transformer… Well, in several components of an electrical system like ours”, explained Carlos Ciocchi.

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