Cables for data transmission in industrial automation - LEONI

www.leoni-industrial-projects.com Fieldbus technology 7FISCO-ModelEspecially in the use of bus systems in explosion-hazard areas,the so-called FISCO (Fieldbus Intrinsically Safe COncept) facilitatesthe planning, installation and extension of networks.The FISCO model was developed in Germany by the PhysikalischTechnische Bundesanstalt (PTB) and has now been standardisedaccording to the international standard IEC 60079-27.The requirements for use of the FISCO model are as follows:■ All participants in the bus (devices) must be FISCO-approved■ Every field device takes up a constant basic current ofat least 10 mA■ Only one supply source per Fieldbus segment■ With ignition protection typeia (Zone 0), the cable must not be longer than 1000 mand with ignition protection ib (Zone 1 and Zone 2) 1900 m■ Maximum length of each spur cable:60 m for device group IIC and IIB■ Maximum length of each trunk cable, including all spur cables:1000 m for device group IICand 5000 m for device group IIBAccording to IEC 60079-27, the parameters for the bus cables areas follows:Loop resistance R = 15…150 Ω/kmLoop inductance L = 0.4…1 mH/kmMutual capacitance C = 45…200 nF/kmWhen lines and cables matching the above requirements areused, it is no longer necessary to take other cable parametersinto account.FISCOFieldbusIntrinsincallySafeConcept