Intrinsic DART

© 2007 Fieldbus Foundation

Dr.-Ing. Gunther KegelCEO Pepperl+Fuchs GmbH, Mannheim

Member of the Fieldbus Foundation Board of DirectorsChairman of the FF European Executive Advisory Council

Foundation Fieldbus Topologies for Intrinsically Safe (IS) Installations

2© 2007 Fieldbus Foundation

Content

1. Necessity of topology elements

2. Preferred general fieldbus topology

3. IS fieldbus topologies

4. Vision

5. DART technology


Information Pyramid

ERP

MES

DCS

FIELD


Automation Pyramid

Sensors und Actuators

Interfaces

PLC

DCS

HMI

Information Q

uantity

Information Q

uality


Power Supply and Wiring Block Topology

HOST Single pointof failure (o.c.)

Single pointof failure (s.c.)

HOST

T


...Fieldbusex-ipower supply

Typical IS fieldbus topology in 2000


Fieldbusbarrier FieldbusbarrierFieldbusbarrier

Termination

Typical IS fieldbus topology in 2004

Fieldbuspowersupply

ex-ispurs


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.


Fieldbus topology for IS installationsIn general the same arguments apply for ISinstallations in regards of grounding; shielding; protection etc.In addition the topology has to provide the ISisolation 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 fieldbusinstallations in hazardous areas.Today two different IS installation concepts for fieldbus are existing:

“True intrinsic safety“-Concept“High Power Trunk“-Concept


“True Intrinsic Safety“-Concept

H1 T

24VTrunk:Ex-i FISCO Gas Group IIC…15 V / 100 mAEx-i FISCO Gas Group IIB….15 V / 200 mA

FISCO Fieldbus Powersupply

Spur:Ex-i FISCO Gas Group IIC .. >10 V / 30 mA

ActiveJunction Box


“High Power Trunk“-Concept

H1 T

24V Trunk:Ex-e ……………. < 31 V / 500 mA

Powersupply


FieldbusBarrier


Characteristics

TrunkProtection

SpurProtection

IsolationTrunkSpec.

Power SupplyRedundancy

True Intrinsic Safety Ex-i FISCO Power

Supply17 V

200 mA1) NO

High Power Trunk Ex-e FISCO

Power Supply+FieldbusBarrier

31 V500 mA2) YES

1) Values are for gas group IIB only.2) Other devices with (e.g. 25 V / 360 mA) are also available


VISION

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


VISION

H1

T

24V


Trunk:Ex-i ……………. > 24 V / 350 mA


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.


24 V / 350 mAIntrinsically Safe !?


Principle of Intrinsic Safety

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)

“ i ”

U

R L

C


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”


Physics of an arc

Rectangular source, U= 25V, I= 500mA, 1000m cable, cable break at 500m

0

5

10

15

20

25

30

0 10 20 30 40 50t [ µs]

U [V

]

0

0.1

0.2

0.3

0.4

0.5

0.6

I [A

]

criticalphase

initialphase

Funken -strom IF

Funken -spannung UFSpark voltage

Spark current


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.


DART basic structure

24V

Ididt

UT

10V

tp

UU

12V

500mA

Power Supply Trunk Cable ActiveJunction Box

R’ l


VISION

H1

T

24V


Trunk:Ex-i ……………. > 24 V / 350 mA

DARTPower Supply

DART


Conclusion

TrunkProtection

SpurProtection

IsolationTrunkSpec.

Power Supply

Redundancy

True Intrinsic Safety

Ex-i FISCO Power Supply

17 V 200 mA1) NO

High Power Trunk

Ex-e FISCO

Power Supply+FieldbusBarrier

31 V500 mA2) YES

DART Ex-i FISCOPowerSupply

24 V350 mA YES


Want to know more about DART and fieldbus?

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Intrinsic DART

Documents

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