Case study: Cemig


Brazilian utilities giant Cemig works with Inmarsat and OnixSat to improve the performance of its electric grid in Minas Gerais.

Cemig is the largest integrated electric power company in Brazil, with 83 power stations and participation in nearly 200 companies and consortia in 22 Brazilian states and the Federal District.

In the state of Minas Gerais, Cemig Distribution is responsible for a concession of approximately 96% of the area, with 8.5 million consumers in 774 municipalities, an area of more than 500,000 km2.

The challenge

One of the main problems that Cemig faces as an electric distribution company is in improving cellular connectivity performance in remote areas of Minas Gerais. While the state plays host to major cities such as Belo Horizonte, it is also made up of very remote areas with lower population densities.

In the event that there is an incident with the electrical system, switches known as reclosers are used to test the medium voltage distribution network automatically, interrupting the power in the event of a problem and restoring the supply if they detect the problem is no longer present.

However, the lack of connectivity in remote areas hampered communication with Cemig’s Centre of Operations, meaning it wasn’t possible to send remote commands to the automated reclosers in the field.

The solution

OnixSat and Inmarsat developed a solution based on satellite connectivity to enable Cemig to increase availability and improve its remote controlling of reclosers.

Sandro Bernardes Oliveira, a telecommunications engineer at Cemig, commented: “The solution was specified by the Management of Telecommunications Solutions and Maintenance, in partnership with the Management of Distribution Assets Automation, and uses a serial/ ethernet converter and Inmarsat’s BGAN 9502 terminal to connect the reclosers to Inmarsat’s ultra-reliable L-band satellite network, in order to ensure the effectiveness of the commands issued to the reclosers by Cemig’s Centre of Operations.”

The Inmarsat satellite communications network has been crucial for assuring connectivity, reaching reclosers in very remote locations in the Cemig distribution network. Its coverage enables Cemig’s field equipment to send and receive data regardless of its location, and its 99.9% uptime ensures that they will always remain connected, even in adverse weather conditions.

With the BGAN terminal to install, and without a complex terrestrial infrastructure to deploy, the solution is easy to configure. Cemig’s technicians do not need to have an advanced knowledge of communication via satellite to implement the solution, because it is very easy to establish a connection with the Inmarsat satellite network.

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The results

The collaboration between OnixSat and Inmarsat has produced impressive results for Cemig. Before deploying the solution, Cemig had an effective availability of remotely controlling the reclosers in the remote recloser project of less than 90%.

After deployment of the Inmarsat and OnixSat solution, this indicator now shows an average of 98% at the points where satellite communication was installed.

Such was the success of the solution based on connectivity via satellite that, after starting by deploying the solution in 150 reclosers, Cemig now plans to install 760 further satellite terminals across its distribution networks and substations.

Daniel Senna Guimarães, Manager of Telecommunications Solutions and Maintenance Management at Cemig, added: “Inmarsat’s satellite connectivity has played an important role within the mix of telecommunications solutions currently used by Cemig, Specifically it provides a communication means with the availability required for mission-critical services, contributing to the improvements in supply quality indicators for the company.”