Profibus System Integration PDF 4.03MB - Schneider Electric

Design PhaseIntroductionObjectiveThe first section of this chapter covers the physical configuration of the PROFIBUSPA network, which includes the number of bus masters, couplers and junction boxes.The second section explains the software design related to the equipmentimplementation, including all system components (PLC, HMI, SCADA) and theinterfaces between these elements.Hardware DesignThe hardware design of a Profibus PA configuration must take into account thefollowing considerations:• The number of Profibus PA segments required to connect the automationequipment. This requires the configuration of each Profibus PA bus inaccordance with the characteristics of each instrument and with the capacities ofthe master bus. If the system is designed for use in an explosive atmosphere, theconnections are limited by overall current restrictions, as stated in Standard IEC60079-27 established by the FISCO (Fieldbus Intrinsically Safe Concept).• The number of master buses and their capabilities.Dimensioning of Profibus PAFieldbus SegmentationAs presented in the Selection Phase chapter, environment has a major affect on aPROFIBUS PA segment’s population density. In addition, the use of field barriers inexplosive areas may increase spurs and segment lengths, and limit the maximumnumber of devices per segment, compared to conventional applications.The limits applicable to Zone 1 are as follows:• Total length (trunk + spurs) is a maximum of 1900 m for an MBP PROFIBUS PAsegment. This length decreases to 1000 m if FISCO applies.• A Segment Coupler designated for standard devices will usually deliver up to 500mA. Following FISCO, this figure drops to 250 mA if this segment coupler isintended to drive Intrinsic Safety devices in Gas Group IIC areas, and to 110 mAif intended to drive Intrinsic Safety devices in Gas Group IIA/IIB areas.• Total length (trunk + spurs) is 1900 m max for an MBP PROFIBUS PA segment.This length decreases to 1000 m if FISCO applies.38