Underground distribution hybrid system

The system "network" of underground distribution applied in some areas of the Eletropaulo is constituted by secondary nets in mesh, supplied for feeders radial and protected breakers of LV. With directional relay, connected to each transforming one, whose basic function is to interrupt the feeding of defects of the primary net for inverse flow of power of the secondary net. Although it offers high degree of trustworthiness, this configuration of net presents one high cost for counting on great capacity of reserve in transforming and net MV/LV, beyond the cited devices of protection - "network protector" - whose cost is also raised. Searching solutions to improve the efficiency and the cost of its installations, are discussed in this article, where they are alternative analyzed proposals and of configurations that derive from the configuration "network", they do without network protector and they can be applied gradually, using itself the radialization of the secondary net, conventional protections and use of underground primary keys that they transfer, automatically, the feeding of the transforming one when of lack in the primary net. The results from the net pilot located in the old center of the city of S. Paulo are presented.