steps to a successful profibus project

7/26/2019 Steps to a successful profibus project

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Practical Steps to a Successful

PROFIBUS Project

Slides by Dr. Xiu Ji - MMU

Presentation today by Richard Needham Hi-Port Controls


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Practical steps to a successful project, The PROFIBUS Group Seminars, Dr Xiu Ji Slide 2

Outline of this presentation

Presentation objective

Introduction to PROFIBUS and associated benefits

Connection options and rules

Other cabling issues : grounding and interference

Design Considerations

Implementation issues

Essential training


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Introduction to PROFIBUS

Fieldbus is widely used in many automation systems.

PROFIBUS solutions for Factory Automation (FA) andProcess Automation (PA)

Applications also involving drives, instruments, servos,robotics, functional safety, redundancy, and explosiveenvironments etc.

Extensive diagnostic functions available to operators andmaintenance engineers

Diagnostic tools available for engineering, commissioning,maintenance, and fault finding

Excellent support from PROFIBUS International, regionalevents and competence and training centres.


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More Information

More adjustable settings and parameters (e.g. scaling,

linearization and calibration).Diagnostic data to inform if measurement is valid.


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Extensive Diagnostics

Controller

Engineering

Station

PA Software

SCADA/HMI

1

2

2

3

Analyser


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6PROFIBUS Applications

Vehicle

manufacture

Bottling plants

Warehousingsystems

Switchgear

Hollow glass

production

Vehicle

assembly

Machine tool

building

Chemical

industry

Petrochemical

industry

Paper and

textile industry

Foodstuffs

Power stations

Sewage plants

Machine tools

Packaging

machines

Pressing plants Paper production

Factory

automationProcess

automation

Drive

technology

Safety

applications


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The PROFIBUS Family

PROFIBUS DP (Decentralised Periphery)Low cost, simple, fast for general automation applicationsWithin short distances, in large quantities, mainly in-door, in dryareas, in cabinetsParameters, options and capabilities can be defined using asimple, text GSD file.

Physical layer uses RS485 or fiber optic


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The PROFIBUS Family

PROFIBUS PA (Process Automation)Developed specifically for the process industry to replace 4-20mAtransmissionTwo-wire connection carrying both power and dataSpread over long distances, in low quantities, mainly out-doors,in wet and exposed sites

Parameters, options and capabilities are defined in additional to aGSD file, in EDD or FDT/DTMLarge number of parameters, options and diagnostic eventsCyclic and acyclic communicationsPA equipment is often used in explosive environments


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Transmission Technologies

Communicat ionTechnology

Transmiss ion

Technologies

PRO FIBUS DP (DP-V0, -V1, -V2)

WiredRS485 / RS485-IS

MBP / MBP-IS

E

ngi

neering

Techn

ologies

GSD

,EDD

,FDT/DTM,

TCI

OpticalGlass, PC F, Plastic

Wireless

P

ROFIdrive

P

ADev

ices

E

nco

der

Ident

Systems

W

eighing

&

D

osage

H

ARTon

P

ROFIBUS

L

abAutomation

SpecificAp plica ti onProfi les

CommonAp plica ti onProfi les

X

Y. . . .

PRO FIsafe, I&M, iPar-Server,Time Stamp, Redundancy,

Communicat ionTechnology

Transmiss ion

Technologies

PRO FIBUS DP (DP-V0, -V1, -V2)

WiredRS485 / RS485-IS

MBP / MBP-IS

E

ngi

neering

Techn

ologies

GSD

,EDD

,FDT/DTM,

TCI

OpticalGlass, PC F, Plastic

Wireless

P

ROFIdrive

P

ADev

ices

E

nco

der

Ident

Systems

W

eighing

&

D

osage

H

ARTon

P

ROFIBUS

L

abAutomation

SpecificAp plica ti onProfi les

CommonAp plica ti onProfi les

X

Y. . . .

PRO FIsafe, I&M, iPar-Server,Time Stamp, Redundancy,

PROFIBUS supports different transmission technologiesWired, Optical, and Wireless


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Connection technologies

PROFIBUS DP uses 2-core shielded and twisted RS485 wiring.

9-pin sub-D or M12 connectors extensively used.

DP can also use plastic or glass fibre optic cabling.ST/BFOC connectors widely used

PROFIBUS PA uses Manchester Bus Powered (MBP) cabling

over 2 cores.Glanded screw or M12 connection normally used

1

0


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Optical transmission

The implementation of a fibre optic cable network involves theuse of electro optical converters (OBT and OLM):

for long distance, between buildings, andto solve grounding problem (grounds with un-even earthpotential).

Fibre

to

Copper

OLM(OpticalLinkModule)

OBT(Optical

BusTerminal)

FO

CouplerFO

Coupler


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Control System Architecture


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From DP (RS485) to PA (MBP)

0

-9mA

time

Current/mA

+9mA

1 1 0 0

PROFIBUS PA, MBP

10 mA

4

To

7

volts

PROFIBUS DP, RS485

0 0

1 1 1


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DP & PA Segments

One PROFIBUS network can host up to 126 stations (masters and slaves)

capacity of a PROFIBUS DP master

Limitation of RS485 and MBP 32 loads and total cable length per segment

M

S

S S

S

S S

S

S

M

S

S

S

S

R O O

Segment

1 RS485

Segment 2

RS485

Segment 3

Fibre Optic

Segment 4

RS485

Segment 5

MBP

Repeater

Fibre optic

links

C

DP/PA

Coupler

SMBP segments can be laid out in a

more flexible manner using Tee

junctions to create spur lines.

Each RS485 segment are best laid

out as a linear bus daisy-chaining

from device to device.


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DP Segment Cable Length

When using best quality PROFIBUS RS485 (Type-A) cables, the

segment cable length is limited according to the network speed.

Baud rate Maximum segment length

9.6 kbit/s 1 200m

19.2 kbit/s 1 200m45.45 kbit/s 1 200m

93.75 kbit/s 1 200m

187.5 kbit/s 1 000m

500.0 kbit/s 400m1.5 Mbit/s 200m

3.0 Mbit/s 100m

6.0 Mbit/s 100m

12.0 Mbit/s 100m

Low

speeds

High

speeds

Middlespeeds


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PA Segment Cable Length

PA baud rate is fixed at 31.25 kbit/s.

The maximum segment cable length is 1900 meters for non-intrinsically safe applications, and.

1000 meters for intrinsically safe applications


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Segmentation, PA

The maximum number of devices on a PA segment is the sameas the maximum on a DP segment, which is 32.

However, how many slaves can be connected to a PA segmentdepends primarily on the power supplied to the segment.

Segment CouplerV = 13.4 VDC, I = 100 mA

#13#14

#15

#16

#17T

14 mA 14 mA 14 mA 14 mA14 mA

Maximum number of

PA slaves = 100 / 14 = 7

I actual = 5 x 14 = 70 mA


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Reflections

When electrical signals travel down a cable, any electricaldiscontinuity can cause reflections to occur

The end of the cable in particular is a major discontinuity, whichcan cause severe reflections, particularly with fast changes

Just like an echo, the reflected signal can cause multiple signalsor corrupted telegrams to appear on the line


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Reflection caused bymissing terminator

Reflection caused by

missing terminator

Reflection caused bymissing terminator

Reflections

Analysis of PROFIBUS system behaviour is covered in PROFIBUS in

Practice system engineering, troubleshooting and maintenance.


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Termination - Rules

To avoid reflections from ends of the cable it is essential

that each segment is terminated at both ends andnowhere else

Both terminators in each segment must be powered at alltimes

Terminator switches and resisters are normally include in9-pin PROFIBUS connectors for this purpose, with plug-interminators used for M12 schemes

+5 volt power is needed for these terminators to workproperly. This is normally supplied from the connected

device

T i ti


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Termination

Standalone termination boxes are also available

for DPand for PA

Termination on Repeaters

Termination


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Termination

1 network with 2

segments.

DP/PA

coupler

#1#0 #10 #11

#13#14

#15

#16#17

Power supply for PA segment

TT

T

T

C f R fl ti


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Causes of Reflections

Missing terminatorUn-powered terminator

Terminator switch - faultyExtra terminatorReflection can also be caused by:

Un-certified devicesCable length between two devices is too shortSpurs are used in high speed networks

Wrong types of cables are usedCores are sharply bent

Allowance of RS485 Spurs


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Allowance of RS485 Spurs

Bit rateTotal allowable spurcapacitance Total Spur cablelength/segment*

>1.5 Mbit/s None None

1.5 Mbit/s 0.2 nF 6.7 m

500 kbit/s 0.6 nF 20 m

187.5 kbit/s 1.0 nF 33 m

93.75 kbit/s 3.0 nF 100 m

19.2 kbit/s 15 nF 500 m

* Calculated for PROFIBUS cable type A at 30pF/m

One spur @ 6.7m or

6 spurs @ 1.1m each

It is much more flexible @ low speed.

Allowance of MBP Spurs


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Allowance of MBP Spurs

The length of the individual spur-lines on a PA segment depends

upon the total number of spurs used:

Number of

spur-lines

Maximum spur length

non-intrinsically safe

Maximum spur length

intrinsically safe

25 to 32 1 m 1 m19 to 24 30 m 30 m

15 to 18 60 m 60 m

13 to 14 90 m 60 m

1 to 12 120 m 60 m

Note that the maximum cable length of 1900m includescable used for spurs. E.g. 18 x 60 = 1080m spurs + 810m trunk line.

Interference


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Interference

Interference is picked up from adjacent equipment or

connected equipment with poor Electromagnetic Compatibility(EMC) rating.

Interference can be caused by:Inadequate earthing of equipment,Poor or incorrect earthing of cable shield,

Insufficient segregation of power and bus cables,Routing cables through electrically noisy areas, andHeavy earth currents on the cable screen.

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6

Equipotential Bonding


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Equipotential Bonding

Installation: Shielding and Grounding


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Shielding and Grounding

The recommended grounding practices:

Connect all PROFIBUS interfaces and cable shields to ground.

Use a grounding cable to go from cabinet to cabinet

in the same segment equipotential bonding.

Types of grounding:

Direct grounding (at any connecting point)

Capacitive grounding

Installation: Shielding and Grounding2

8intern

Equipotential Bonding at a Device


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Equipotential Bonding at a Device

Connect the PROFIBUS cable shield to the equipotential

bonding at every PROFIBUS station assuming local potentialsare equal!

Shielded, twisted-pair cable

Cable shield route

to groundRx

Tx Tx

Rx

Connector

Device Device

Red = +

Green = -

Connector wiring problems


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Connector wiring problems

Which connectors are incorrectly wired?

A CBD

Cable Segregation


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Cable Segregation

All channels and partitions must be properly earthed.

Use flexible bonding links are protected against corrosion. Braided straps are better than solid metal.

Cable Segregation Distance


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g g

In general, the greater the spacing between the cables and the

shorter the paths run parallel, the lower the risks ofinterference.Recommended cable segregation distances:

Cable

Category II

20 cm

10 cm 10 cm

50 cm 50 cm 50 cm

Cable

Category I

Cable

Category III

Cable

Category IV

Cable Segregation ?


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g g

An example: variable frequency drivesCan you spot the error here?

Power cable route

Spot the errors


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p

Spot the errors


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Spot the errors


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Standard connections PROFIBUS DP3


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3

7

Standard connections PROFIBUS PA3


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3

8

Tink

oupler

TPROFIBUS DP PROFIBUS PA

Trunk

Spur lines

Devices

Link

oupler

TPROFIBUS DP PROFIBUS PA TJunction

Box

Junction

Box

Spur lines

Trunk

Devices

Spot the errors


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Design considerations - details


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Limitations of segment loads and total cable length

Standalone terminations for DP, redundant power supply toterminators

Network drawings node addresses, mark of terminationposition, cable routes, cable length between connectors andjunction boxes, trunk cable and drop cable length

Piggyback connectors spare connection into EVERY segmentfor voltage measurements and troubleshooting

Design considerations - architecture4


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Which network to use PROFIBUS, PROFINET, DP, PA, AS-i?

Designation of safe and hazardous areas

Production and functional safety systems

Cable routes fibres, copper cables, earthing systems,equipotential bonding cable in place?

Cabinet or field assembly

Connection of devices via remote IO or integrated fieldbus?

Use of redundancy at difference levels

Network and device access for engineering, monitoring andmaintenance

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1

Installation Checklists4


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Checklist to determine network topology and obtain thenetwork drawing

Checklist for PROFIBUS DP (RS485) Grounding

Checklist for PROFIBUS PA (MBP) Grounding

Checklist for PROFIBUS DP (RS485) Cabling

All above are included in PROFIBUS in Practice installingPROFIBUS devices and cables as templates for a Factory

Acceptance Test document.

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2

Practical steps to a successful PROFIBUS project4


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The very first step to a successful project should be

Training

PROFIBUS training courses are available for:Installers,System Designers,

Commissioning Engineers, andMaintenance staff.

Many industry sectors specify that their staff, contractors andsub contractors must be appropriately trained.

Competence Centre - Manchester Metropolitan University

Training Centre Verwer Training and Consultancy

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Certified PROFIBUS Installer Training4


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This training is widely accepted as the minimum standard oftraining for anyone who is working in PROFIBUS systems at atechnical level.

Available as a one-day training course in house or on-site.

It teaches the basic principles of PROFIBUS and covers the basic

layout, installation and testing of DP and PA networks.

It is also essential basic training for system designers,maintenance and all engineering staff.

Background details are covered in the series of PROFIBUS in

Practice, the orange and blue textbook.

Extra days can be added to extend the training for maintenance,design and engineering staff.

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4

PROFIBUS System Design Training4


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Good overall design, with good documentation and clearspecifications of required wiring, installation, testing,commissioning and final setting-to-work practices arerecommended. Production of final as installed drawings arealso recommended (to assist with subsequent maintenance)

Designer training will allow companies to ensure that their

designers are aware of the common design pitfalls and able toproduce systems that are cost effective, efficient andmaintainable.

Designer course at MMU is 3 days covering installation,maintenance, and design.

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Summary: Steps to a successfully project4


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1. Design staff should be trained before the design starts.

2. Everyone involved in the project at a technical level is trained toan adequate level, at the least to the designer or installer level

3. Make sure that designers are fully aware of the methods fordiagnosing and locating faults, before start of design

4. Ensure that health checking and performance monitoringfacilities are incorporated into the network

5. Follow the extensive guidance that is available from PI and fromcompetency and training centres, for example, incorporating

the checklists in to your installation acceptance tests

6

steps to a successful profibus project

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