Tecnologia de comunicação em sistemas SCADA: enfoque em comunicação wireless com espalhamento espectral

Abstract

The necessity of the production information to be divulged in some places simultaneously, showing resulted on-line of the production chain, made with that the data communication nets are each time more present in enterprise daily and compels the constant search for new techniques and ways to establish this communication. To specify supervisory control and acquisition data system (SCADA), over all, involving remote supervision and control of machines and equipment in real time, is not an easy task. In the investment strategy, the appropriate choice of the net and way to establish this communication in the integration of the equipment distributed in different places are an important factor for the success of the production chain integration. The present work compares the technologies of communication in SCADA systems, through a qualitative research and case study in a company with SCADA system implanted and net of data with diverse ways, as conducting handles of electricity, optics fiber and waves of radio (wireless). The result is useful for any involved designer in phases of planning and project of SCADA systems. The study it showed that, in places of difficult access or where the substitution of the physical lines if justifies for the financial return the medium and long run, the communication wireless with technique of spread spectral, using radio MODEM in frequencies operating in the set free bands for the ANATEL, is currently the technology without wire that presents the best cost/benefit relation in the communication in SCADA systems, since this technology eliminates the data-communication monthly costs, when compared with the dedicated lines of data or cellular telephones with tariff for package data. This system presents a solution safe, trustworthy and adjusted for the communication of data between PLC and computer, besides granting to the users independence of the public and private communication systems.