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After 19 months, the generating unit #6 (U6) returns to operations
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21/03/2012

The return to operations of the generating unit #6 (U6), of Itaipu Binacional, Tuesday (20), after a halt of nearly 19 months, it will regularize the preventive maintenance schedule of the plant and, consequently, raise the level of production and security predictability of Brazilian power system. The evaluation is the Deputy superintendents, engineer Marco Cesar Castella, Plant Maintenance, and engineer Celso Torino, Operations.

U6 was reconnected to the power system at 8:24, this Tuesday and, since then, progressively it increased power load. At the same time, the recent tests were carried out on the machine, so that it would operate with security – such as hydraulic stability tests, vibration, noise and differential pressure as a function of power load.

Around 3:0 pm, U6 peaked at 100% capacity, around 700 MW – sufficient power to supply Curitiba Metropolitan Region of 2.5 million inhabitants. The Brazilian General Director of Itaipu, Jorge Samek, followed the final part of the work.

Mr. Samek stated that the return of U6 represents a historic date for Itaipu and the plant is ready today to meet any demand request on the part of the National System Operator (ONS). He added that the knowledge acquired by the staff of the plant, during the recovery process, will be catalogued and will comprise Itaipu Corporate University database, which will be available to future generations;.

“It was a task that allowed sharing the more experienced workers’ knowledge with the youngest ", he said. The Director-General recalled that the initial prediction was U6 returning to the system only on 23 April – but the work was anticipated in 33 days. “This was only possible thanks to the efficiency of Itaipu technical staff ", Mr. Samek praised.

The resumption of generation in unit #6 will reflect positively both in power plant’s ,maintenance and operations. “We will be able to better distribute the workload of our professionals, without overburdening the teams or sacrificing the schedule ", Mr. Castella commented. “I would say that maintenance provides sustainability to production in the long term. Thus, the return of U6 makes this relationship, maintenance-operations, even more harmonic ", Mr. Torino added.

Technical reserve

With 20 generating units installed, Itaipu has permission to operate 18 of them simultaneously. The other two are always halted for: maintenance or as technical reserve. The return of the U6 will also enable to connect quickly the unit to the system, if another machine has an unscheduled outage. “In other words, it means that once the planned production, we can fulfill it ", Mr. Torino highlighted.

According to the engineer, should the need arise, it is possible to connect one unit to the power system in only three or four minutes. “This highly valued by our customers, who are consumers both from Brazil and Paraguay. Particularly, if the need for this connection appears at consumption peak time ", Mr. Torino said.

At the other end of the process, maintenance follows a strict schedule. Each machine goes through semi-annual inspections (half workday), interspersed with annual inspections (9 workdays), biannual (11workdays) and every four years (13 workdays). The importance of the work can be measured by the discovery of small cracks in the U6 turbine wheel precisely during a routine inspection in September 2010, by Itaipu professionals.

According Mr. Castella, in the period that U6 was stopped, one of the major concerns of the sector was to avoid that three machines were out of service at the same time, restricting power generation. “Therefore, we had to undertake maintenance on Saturday and Sunday last year, adjusting schedules. Everything not to damage the power system " he disclosed..
 
Record

The return of the U6 reinforces Itaipu management expectations of closing 2012 with power generation equivalent to 2008, when the plant reached the record of world production with 94,684,781 MWh. Mr. Torino recalls that there are four factors impacting generation: hydrological conditions, power demand, transmission and the unit’s own production capacity. “The return of U6 reduces the chance of the generating unit be a restrictive factor of generation ", he commented

The operations Deputy Superintendent of the right bank, Mr. Anastacio Sebastian Arce Encina, points out another advantage of U6 return. According to the engineer, the unit reinforces the generation 50 Hz sector of the plant, whose transmission limit is high – unlike the 60 Hz sector, which has a capacity of transmission lower than generation.

“Brazil has enhanced the 60 Hz transmission system with the construction of the Foz-Cascavel line. However,  until this line is operational with all its circuit breakers, situation scheduled for mid of next month, the presence of U6 gives us further confidence that we are not going to waste water by lack of generating unit”,  Mr. Torino mentioned.

Full mapping

Juan Alberto Molina Mauro, Paraguayan maintenance superintendent, added that the recovery work on Unit 6, undertaken by Itaipu professionals, raised the technical qualification of personnel, allowed the exchange of professional experience between the younger and the more experienced, as well as producing a database that will be vital to future revisions. There are 36 thousand pictures and 1,320minutes of filming. “ Is a full mapping of all that we need to pay more attention in the next revisions ", Mr. Castella added.