On October 13th, 2016, I was invited to join a crew of engineers in a visit to the main gate of electricity to the Brazilian capital. Called Furnas Samambaia Substation, this is a transmission substation that receives electricity from the North, generated at Hydroelectric Serra Da Mesa Plant, 350 km away from Brasília. This is a 1.252 GW plant, in operation since 1998. It has the biggest water tank in Brazil, with capacity of 56.6 billion cubic meters of water. And also, this is a very singular plant as it is  underground plant, with a full digital operation.

During the visit, 5 engineers and I walked through all facilities at the substation. Starting from where the electricity arrives at 500kV, big towers handle the transmission conductors (See image bellow). At the top of that structure, there were two cables, the guard cables. Its function is to protect the conductors from being hit by lightning strikes, that may cause overvoltages and short-circuits on some occasions. Right after the arrival of the transmission lines, each phase conductor passes through a piece of equipment that counts the surges. One of the phases has counted 12 surges, since its installation a couple of years ago.


Then, inside the substations, the phases flow through several subsections of the substation that perform a specific operation. There was a Capacitor Bank, that has the function of balancing the reactive power in the grid and keeping the power factor as close to 1 as possible. There were Current Transformers and Potential Transformers, that have the function of changing the potential and current values to the level at which the other equipment operates. There were breakers and switchers, to make the necessary changes in power flow on the grid. There were some huge transformers, to lower the voltage from 500kV to 245kV. And many other pieces of equipment that were responsible for the safe and efficient operation of the facility and the electrical grid.

During the walk around all that equipment, I heard very loud noises. They were due to the corona effect – that is the occurrence of electrical discharges due to the ionization of the air around the conductors in the substation. The substation engineers relayed that during the night it is possible to see purple and green lights around the conductors. I’m sure it is a beautiful scene, but during the day those loud noises were just super scary.


In the end, the engineers showed us the control room, with a very old, unattractive and unintuitive  system that runs the whole substation operation. He also told us about the lack of automation in situations like maintenance. Once a year a team of technicians and engineers have to drive along approximately 2,300 km of transmission lines looking for problems to be fixed during the year. They also made some comments about some extreme situations they had experienced during their time at the substation.

It was an amazing day, besides the sunburns due to a 3-hour walk in a super sunny day. A lot of valuable information and learning from those who have been doing for several years what I am about to start doing – being an engineer. Thanks for it Alcides, Rogerio, Felipe, Rogerio, and Caio. It was awesome!