Power Transmission

Cemig runs one of the largest extra-high-voltage transmission complexes in Brazil, which is vitally important within the Southern-Southeastern interconnected system due to its strategic position. The extra-high-voltage transmission system is concentrated in the Triāngulo Mineiro Region, where six of Cemig's major hydroelectric power plants are located, accounting for more than 80% of its energy generating capacity. The power is transmitted to consumers located in and around the central part of the State, supplying the second largest consumer market in the Country.

Cemig has been busy expanding and modernizing its transmission system, through the construction of new lines and large substations, in order to increase its reliability and provide for the expansion of the market. Currently, its transmission system has 21,120 km of transmission and sub-transmission lines, in addition to 424 step-down substations, with a transformation capacity of 28,757 MVA.

The System Operation Center (COS) is the heart and nerve center of Cemig's electrical system. Its basic function is to provide real-time coordination of the integrated operation activities of the main energy generation and transmission systems, ensuring operational reliability, rationality, speed and safety for the generation complex and to the main transmission grid of Cemig.

In support of the system's operations, Cemig employs a SHF/UHF microwave telecommunications network. This consists of 2,520 km of SHF routes interconnecting 74 stations and another 600 km of UHF routes, with 68 stations. The system also has 832 communication terminals using high-voltage line carrier waves, 507 km of optical fibers, a private telephone system, fixed-mobile radios with 700 fixed and repeater stations, 2,015 mobile and 1,398 portable stations.  

Pioneering Projects and State-of-the-Art Technology

Cemig has always been a pioneer in the Brazilian Electrical Industry. Another major goal is now being achieved with the development of its new Distributed Supervisory and Control System (SSCD), which provides its System Operation Center (COS) with a state-of-the-art computer system, facilitating the accomplishment of its functions in the real-time operation of Cemig's system.

With the purpose of replacing its former Supervising and Control System, Cemig used its own technical staff to design, execute and deploy the SSCD, creating a modern system, capable of supporting the most advanced applications for the control and management of electrical power systems. For the selection of hardware and basic software design, Cemig employed the consultancy services of Digital Equipment do Brasil.

The development of the system was achieved through the utilization of a structured methodology of project management and prototyping techniques for the development of the applications that assured the bug-free and well-documented implementation of the system, within the required timeframes.  

Successful Exports

The ease with which the SSCD can adapt itself to the functional requirements of other centers has enabled Cemig to extend the initial design, with the incorporation of this technology into the development of the supervisory and control systems of its Regional Operation Centers (COR).

The success of the SSCD has underscored Cemig's role as a supplier of supervisory and control systems, opening up another business opportunity for the Company, through the sale of this product to similar companies, both in Brazil and abroad.