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The blackout that affected Amapá on the night of November 3 – and which still limits the electricity supply in the state – is related to a “multiple contingency” that completely affected the operation of the Macapá substation, where one of the equipment exploded in a storm. The Disturbance Analysis Report (RAP), prepared by the Operator of the National Electric System (ONS), records a set of failures by the plants and the distribution network that supply the State.
The RAP, to which the Value had access, it will still be subject to the latest reviews, but it reinforces the preliminary findings that the Macapá substation could collapse at any moment.
The multiple contingency mentioned in the conclusion of the report refers to the comparison of the blackout in Amapá with the accident of a commercial airplane, a tragedy that is not determined by a single factor, but by the combination of several. The example was initially used by the command of the National Electric Energy Agency (Aneel) to explain what happened.
In the conclusions, the operator indicates that it has already started studies, together with the Energy Research Company (EPE), to propose a definitive solution for the State service. “ONS and EPE are evaluating possible alternatives to increase the reliability of the service to the Macapá load that is currently supplied by SE Macapá and UHE Coaracy Nunes, considering the network topology and the availability of local generation”, records.
The substation installed in the capital is the main energy input of the state. The concessionaire Linhas de Macapá Transmissora de Energia (LMTE) belongs to Gemini Energy, which, in turn, is controlled by holding funds Starboard and Perfin. The group took over the project at the end of last year, following the restructuring of the Spanish group Isolux Corsán.
Wanted by Value, Gemini Energy declined to comment. The company, despite being responsible for the operation and maintenance of the network, relies on the communications sent to ONS about the conditions in which it received the line and the maintenance and equipment replacement plan that it assumed from Isolux. The substation operated according to the safety criterion called N-1, which does not have a cut-off in case of equipment failure.
With this position, the concessionaire ends up directing part of the pressure it has received to ONS, responsible for the operation and analysis of risks involved, and to Aneel, in its role as inspector of transmission facilities, as well as generation and distribution.
In the report, ONS acknowledges that the Macapá substation was operating with only two of the three transformers at the time of the blackout. Thus, the network worked without backup equipment due to a problem with the transformer TR2.
Now, the analysis of the operator of the Brazilian electrical system shows that, after the blackout, a problem of “damaged bushing” was detected in one of the two transformers in operation, the TR3. The report indicates that it was precisely the explosion of a hub like this that caused TR2 to become unavailable at the end of 2019.
The TR1 transformer was the equipment that triggered the blackout in Amapá. The fault started with a short at 8:48 pm, recorded by ONS with millisecond precision. Then there was an explosion from this transformer, followed by fire.
The document reconstructs the sequence of “disturbances” in the operation of the system that lasted for almost 24 hours. The substation problem caused “voltage and frequency degradation in this system.” This caused the shutdown of one of the turbines at the Coaracy Nunes hydroelectric plant. Another generation unit of the plant suffered an overload and also a shutdown, which “culminated in the total collapse of the loads in the Amapá system” related to the Macapá substation.
With the local distributor CEA, the operator reported a failure at the Equatorial and Santana substations. There was also a need to move equipment to the SE Port to verify the operation of the circuit breakers. The report reports, however, that there were “several unsuccessful attempts to make a telephone call” from the ONS regional representation to the distributor, through the so-called “hot line” system.
When asked about the content of the report, ONS simply replied that it worked with agility to draft the document in the shortest possible time. With this, the operator reported that it was possible to reduce the period from 15 to five business days from the first meeting with the sector authorities to address the causes of the blackout. Aneel declined to comment.
At dawn yesterday, new cuts were registered in the Amapá electricity supply system. Residents of the capital neighborhoods registered a sequence of short circuits in CEA publications, which confirmed the authenticity of the images published on social networks. The failures occurred two days after the visit of President Jair Bolsonaro, who made the official delivery of generators and signed a provisional measure to guarantee the benefit of exemption on Amapaense’s electricity bill.
