Analysis of coordination and selectivity between protection devices of low voltage system (440vac)

This study aims to analyze the coordination and selectivity of the protection in a low voltage industrial electrical installation, so that the protection devices isolate and eliminate the fault quickly and selectively. To achieve this objective, a survey of the installed loads was carried out, a conference of fuse values and adjustment of the thermal relays, verification of the gauge of the cables connecting the respective loads and calculations of the short-circuit current through a software. Therefore, we want to demonstrate the importance of the correct selection of protection equipment and the impact that it can cause in productivity when incorrectly designed, impacting the continuity of the electric power supply to the manufacturing process. The analyzes presented here are based on the IEEE 242 standard, coordination and selectivity reports, and authors such as Caminha, Mamede Filho, Hewitson and Mardegan. The study was carried out within a pulp and paper industry, which, because it was an old plant, some protective equipment had to be replaced by modern ones. For example, the fuse switches and the bimetallic relays were replaced by electronic thermal relays and motor circuit breaker, since the old equipment did not allow us to make the correct coordination and selectivity, while others were only adjusted to work accordingly with the nominal data of the motors information plates. in this way, the objective of adapting the coordinated and selective protection system for overload, short-circuit and blocked rotor disarms was reached.