Foundation Fieldbus Topologies for Intrinsically Safe (IS) Installations

Transcription

1 Foundation Fieldbus Topologies for Intrinsically Safe (IS) Installations Dr.-Ing. Gunther Kegel CEO Pepperl+Fuchs GmbH, Mannheim Member of the Fieldbus Foundation Board of Directors Chairman of the FF European Executive Advisory Council

2 Content 1. Necessity of topology elements 2. Preferred general fieldbus topology 3. IS fieldbus topologies 4. Vision 5. DART technology 2

3 Information Pyramid ERP MES DCS FIELD 3

4 Automation Pyramid Information Quality HMI DCS PLC Interfaces Sensors und Actuators Information Quantity 4

5 Power Supply and Wiring Block Topology HOST Single point of failure (o.c.) (s.c.) HOST T 5

6 Typical IS fieldbus topology in Fieldbus ex-i power supply 6

7 Typical IS fieldbus topology in 2004 Fieldbus power supply Termination ex-i spurs Fieldbusbarrier Fieldbusbarrier Fieldbusbarrier 7

8 Topology Requirements 1. Avoid single point of failure architectures. 2. Integrate Shielding and Grounding. 3. Guarantee protection against short circuit and open circuit of fielddevice connections. 4. Provide current limitation to fielddevices. 5. Gain maximum cable length and acceptable voltage drop to add actuarial reserves. 8

9 Fieldbus topology for IS installations In general the same arguments apply for IS installations in regards of grounding; shielding; protection etc. In addition the topology has to provide the IS isolation between safe areas (e.g. control room) and hazardous areas (e.g. field). As fieldbus devices are low power devices anyhow, IS is a very appropriate method for fieldbus installations in hazardous areas. Today two different IS installation concepts for fieldbus are existing: True intrinsic safety -Concept High Power Trunk -Concept 9

10 True Intrinsic Safety -Concept 24V Trunk: Ex-i FISCO Gas Group IIC 15 V / 100 ma Ex-i FISCO Gas Group IIB.15 V / 200 ma H1 T FISCO Fieldbus Powersupply Active Junction Box Spur: Ex-i FISCO Gas Group IIC.. >10 V / 30 ma 10

11 High Power Trunk -Concept 24V Trunk: Ex-e. < 31 V / 500 ma H1 T Powersupply Fieldbus Barrier Spur: Ex-i FISCO Gas Group IIC.. >10 V / 30 ma 11

12 Characteristics Trunk Protection Spur Protection Isolation Trunk Spec. Power Supply Redundancy True Intrinsic Safety Ex-i FISCO Power Supply 17 V 200 ma 1) NO High Power Trunk Ex-e FISCO Power Supply+ Fieldbus Barrier 31 V 500 ma 2) YES 1) Values are for gas group IIB only. 2) Other devices with (e.g. 25 V / 360 ma) are also available 12

13 VISION True Intrinsic Safety -Concept and High Power Trunk -Concept are both widely accepted and have to be seen as prooven technology. What about a True Intrinsically Safe High Power Trunk -Concept? In other words: Can we achieve high power on an intrinsically safe trunk? 13

14 VISION 24V Trunk: Ex-i. > 24 V / 350 ma T H1 Spur: Ex-i FISCO Gas Group IIC.. >10 V / 30 ma 14

15 Advantages Single Ex-i harzadous area protection concept, no Ex-e wiring. High Power Trunk offers more cable length through accepting bigger voltage drops along the trunk cable. Simplified Active Junction Box (compared to Fieldbusbarrier). Spurs remain FISCO protected. 15

16 24 V / 350 ma Intrinsically Safe!? 16

17 Principle of Intrinsic Safety R L i U C The energy in an intrinsically safe system is limited to a value that is not capable of causing ignition in normal operation and fault condition in the surrounding hazardous atmospheres by sparks (opening, closing, short circuit, short circuit to earth) 17

18 Principle of Intrinsic Safety The classic protection method is to limit voltage, current, power, inductance and capacity in an intrinsically safe system to a constant value. -> The results are documented in Ignition curves 18

19 Physics of an arc Funken - spannung U F Spark voltage U [V] critical phase Funken - strom SparkI F current I [A] 5 initial phase t [ µs] 0 Rectangular source, U= 25V, I= 500mA, 1000m cable, cable break at 500m 19

20 DART DART is a new intrinsically safe concept developed and approved by Physikalische Technische Bundesanstalt (PTB) in Braunschweig and Pepperl+Fuchs Mannheim. Dynamic Arc Recognition &Termination The principle of DART is the detection of the development of an arc and the fast shut down of power source and/or sink. 20

21 DART basic structure Power Supply Trunk Cable Active Junction Box I di dt R l t p 24V U T 10V U U 12V 500mA 21

22 VISION 24V Trunk: Ex-i. > 24 V / 350 ma H1 DART T DART Power Supply Spur: Ex-i FISCO Gas Group IIC.. >10 V / 30 ma 22

23 Conclusion Trunk Protection Spur Protection Isolation Trunk Spec. Power Supply Redundancy True Intrinsic Safety Ex-i FISCO Power Supply 17 V 200 ma 1) NO High Power Trunk Ex-e FISCO Power Supply+ Fieldbus Barrier 31 V 500 ma 2) YES DART Ex-i FISCO Power Supply 24 V 350 ma YES 23

24 24 Want to know more about DART and fieldbus? Visit the Interkama 2008 in Hannover!