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Itaipu exceeds 100 million MWh in 2016: behind the scenes of production
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20/12/2016
 
Generating energy in a hydroelectric plant is theoretically simple, since hydroelectricity is based on some fundamental laws of physics. First it is necessary to have water, the potential energy stored in the reservoir. There is a height difference between the uptake of water at the top of the dam and its discharge downstream. In this path, the water passes through the generating units, and the kinetic energy (of the movement) is transformed into electric energy.
Itaipu Reservoir: for the company, water is energy stored and needs to be harnessed to the full.
 
In addition to the availability of water, three other factors are determinant for a hydroelectric plant to produce energy: generating units and transmission lines under operating conditions and consumption.  “Water and consumption are variables over which we have no control. So our role is to act so that generating units and transmission systems are not limiting factors for production. If we are successful, for the consumer it is as if these factors were infinite,” explains Itaipu’s Superintendent of Operations, Celso Torino.
 
In order to maximize the availability of its generating units, form 2011 Itaipu has improved its operational management model, which incorporates principles of Production Engineering and which presupposes a greater integration between the plant’s Engineering (EN.DT), Works (SO.DT), Maintenance (SM.DT) and Operation (OP.DT). The idea is to make the most of all the water that reaches the reservoir.
 
The results of this management model are clear if we observe the evolution of production and productivity indexes of the plant (see table). In 2008, for example, when Itaipu set a world record of 94.6 million MWh, Itaipu recorded the use of 97.6% of its water resources. This means that of all the water of the Paraná River that arrived at the plant and could be transformed into energy, 97.6% was actually used, an exceptional performance until then.
  
As of 2012, this index has always been higher than 96%, reaching 99.3% in 2014. For this year, when the plant is registering a new world record with more than 100 million MWh, the index should again exceed 96%. Some external factors contributed to this number not being even better, such as the economic downturn, which impacts on the demand for energy.
 
How It Works
 
The operational management model was baptized internally as “dance with the waters”, which already gives an idea of its concept. Everything begins in the Hydrology area, which maintains an uninterrupted monitoring of the behavior of the reservoir, its tributaries and rainfall in the Paraná Basin. The data provided by this area is decisive for the decision-making of other areas related to energy production, which, within certain principles and limits, have the mission of providing the best use of water resources.
 
In-Field Hydrological Data Collection.
 
By incorporating principles of Production Engineering, water is treated as a resource within a supply chain. “Within the determining factors for production, the consumer is more predictable. If the temperature rises, there’s more consumption. On Sundays and at dawn, demand falls. So if we look for efficiency in production, our actions must be based on water behavior,” Torino adds.
 
Hydrology issues daily bulletins, with data ranging from the next few hours to forecasts for 10 days. “The setting for the following days is updated and improved on a daily basis. And the operation can estimate if you can count on the incoming water or if you have to use the reservoir stock,” says Rafael de Souza Favoreto, manager of the Programming and Statistics Division (OPSP.DT). The scenario is also estimated with the knowledge of the predicted and future conditions of the electrical systems of Brazil and Paraguay that can impact Itaipu.
 
The data is automatically captured by about 40 stations called the Hydrometeorological Telemetry System (STH) and sent to a central station. The plant also uses data from meteorological systems, such as satellite imagery, radar images and the location of electric discharges, through agreements with the Paraná Meteorological System (Simepar) and the National Civil Aeronautics Directorate (Dinac) of Paraguay.
 
Behavior of water in the “guts” of Itaipu is also closely monitored by the teams responsible for dam safety.
 
Along with Itaipu’s almost 33-year experience in generation there is continuous improvement of the models that project the behavior and propagation of water in the watershed.   “The more precise the hydrometeorological bulletin, the better the planning of production for the next days,” summarizes Alberto de Araújo Bastos, manager of the Operating System Department (OPS.DT).
 
The forecast goes to the planning area of the operation, which in turn receives from Ande (in Paraguay), and Eletrobras and the National System Operator (in Brazil) the forecast of energy demand in both countries. The Operation seeks, therefore, to adapt the maximum use of water to the times of greater consumption. 
Maintenance actions, within certain limits, adapt to dates and times in order to maximize production.
 
At the same time, maintenance actions and works that may involve machinery shutdown are also appropriate. These tend to occur in more adequate dates and within certain limits, and can be advanced or postponed due to the best use of water. 
 
Typically, Itaipu operates with the availability of 19 generating units and one in maintenance. Among the 20 units, ten are in the 50 Hertz sector and ten are in the 60 Hertz sector. The flexibility adopted by the plant also implies using more water in one or another sector, depending on the scenario. “If Ande’s consumption forecast is not confirmed, for example, this means that more energy is available for Brazil and vice versa, and the adjustments are made in real time in the Cargo Dispatch Room,” exemplifies Rodrigo Gonçalves Pimenta, from the System Operation Division (OPSO.DT).
 
Other variables influencing the production management come from the teams that supervise the operation of the machines and the entire plant in the Supervision and Central Control room. The generating units have a series of sensors that can trigger alarms, signaling some type of malfunction, such as an abnormal temperature rise. Teams then have to assess whether this is an anomaly that needs to be resolved on the spot, with the machine shut down, or if it can be repaired without interruption of generation. Or, still, it can momentarily operate with the anomaly, thus scheduling the intervention for a moment of low consumption. However, before keeping the machines in operation, there are three basic pillars that guide decision making: whether it involves any risk to the workers or the environment; Or if there is a risk to the plant’s equipment or assets; Or even if the energy production itself can be put at risk. 
 
It is a risk analysis that can involve committed and skilled people from at least three Technical areas: System Operation, Plant Operation and Maintenance. “Some maintenance actions, works or assembles are made while the machines are operating. It’s like fixing a plane in mid-flight,” says Douglas Teixeira Barreto of the Operation Division of the Plant and Substations (OPUO.DT). “A wrong decision can lead, at the very least to a loss of efficiency in production,” adds Paulo Zanelli Júnior, from the same area. 
 
Load Dispatch Room: interaction with the electrical systems of Brazil and Paraguay influences decisions in real time.
 
The comparison with aeronautics is another parallel to breakdown solution. Just as pilots are trained for a series of procedures that are adopted in critical situations, the management of hydroelectric production also adopts specific emergency command sequences. 
 
According to Rui Jovita Godinho Correa da Silva, manager of the Division of Electrical Studies and Standards (OPSE.DT), Itaipu has promoted over the years a series of studies that allow the operation to know what should be done when unforeseen events arise, such as drop of transmission lines. “Today, the vast majority of occurrences are planned and operators know the measures that need to be taken,” he says.
 
The evolution of the crisis management also allowed to reduce eventual transmission bottlenecks. In extreme events, such as the World Cup, the Olympics or a papal visit, where the electric sector needs to operate within a more restrictive range for extreme security, Itaipu’s load availability to Brazil used to be reduced from the usual 7 thousand Megawatts to 3 thousand Megawatts. 
 
With the evolution of the plant’s operating procedures, this load is now restricted to 4.9 thousand Megawatts, which, in addition to the power gain, also represents a greater reliability for the system. Likewise, medium and long-term studies and actions are adopted by all areas of Itaipu’s Technical Board, so that production restrictions are systematically avoided or eliminated. 
 
Water use at Itaipu
2008*    97.6%
2012*   98.8%
2013*    98.5%
2014      99.3%
2015      96.5%
2016*    96%**
*Years in which Itapu set a world record of production.  
**Estimate.