practical steps to a successful profibus project - xiu ji of the uk's picc

Practical Steps to a Successful PROFIBUS Project

Dr. Xiu Ji

Practical steps for a successful project, Xiu Ji. PROFIBUS Seminar at MTC, Coventry, 2013. Slide 2

Outline of this presentation

Basics of PROFIBUS Considerations at the design stage Installation - visual checks Summary – Steps to a successful PROFIBUS project


Introduction to PROFIBUS

Fieldbus is widely used in many automation systems.

PROFIBUS solutions for Factory Automation (FA) and Process Automation (PA)

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

Extensive diagnostic functions available to operators and maintenance engineers

Probably the single reason to use bus or networked devices and systems

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

Excellent support from PROFIBUS International, regional events and competence and training centres.


More Information

More adjustable settings and parameters (e.g. scaling, linearization and calibration). Diagnostic data to inform if measurement is valid.


Extensive Diagnostics

Controller

Engineering

Station

PA Software

SCADA/HMI

1

2

2

3

Analyser


The PROFIBUS Family

PROFIBUS DP (Decentralised Periphery) Low cost, simple, fast for general automation applications Within short distances, in large quantities, mainly in-door, in dry areas, in cabinets Parameters, options and capabilities can be defined using a simple, text file, GSD file. Machines or a production line can be stopped in case of communication problems Physical layer uses RS485 or fiber optic


The PROFIBUS Family

PROFIBUS PA (Process Automation) Developed specifically for the process industry to replace 4-20mA transmission Two-wire connection carrying both power and data Spread over long distances, in low quantities, mainly out-doors, in wet and exposed sites Parameters, options and capabilities are defined additional to a GSD file, also in EDD or FDT/DTM. Machines and processes cannot be stopped if there are only communication problems Large number of parameters, options and diagnostic events Cyclic and acyclic communications PA equipment is often used in explosive environments


Transmission Technologies

Communication Technology

Transmission

Technologies

PROFIBUS DP (DP-V0, -V1, -V2)

Wired RS485 / RS485-IS

MBP / MBP-IS

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OpticalGlass, PCF, Plastic

Wireless

PR

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Idrive

PA

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SpecificApplication Profiles

CommonApplication Profiles

XY

. . . .

PROFIsafe, I&M, iPar-Server, Time Stamp, Redundancy, …

Communication Technology

Transmission

Technologies

PROFIBUS DP (DP-V0, -V1, -V2)

Wired RS485 / RS485-IS

MBP / MBP-IS

En

gin

ee

rin

g T

ech

no

log

ies

GS

D,

ED

D,

FD

T /

DT

M,

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OpticalGlass, PCF, Plastic

Wireless

PR

OF

Idrive

PA

De

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on

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SpecificApplication Profiles

CommonApplication Profiles

XY

. . . .

PROFIsafe, I&M, iPar-Server, Time Stamp, Redundancy, …

PROFIBUS supports different transmission technologies Wired, Optical, and Wireless


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

9


Fibre Optic

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

for long distance, between buildings, and to solve grounding problem (grounds with un-even earth potential).

Fibre to Copper

OLM (Optical Link Module)

OBT (Optical Bus Terminal)


Control System Architecture


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


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

S

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01_book_Aug_2013_Final_1.pdf


Segmentation, PA

The maximum number of devices on a PA segment is the same as the maximum on a DP segment, which is 32. However, how many slaves can be connected to a PA segment depends primarily on the power supplied to the segment.

Segment Coupler V = 13.4 VDC, I = 100 mA

#13 #14

#15

#16

#17

T

14 mA 14 mA 14 mA 14 mA 14 mA

Maximum number of PA slaves = 100 / 14 = 7

I actual = 5 x 14 = 70 mA


Reflections

When electrical signals travel down a cable, any electrical discontinuity can cause reflections to occur. The end of the cable in particular is a major discontinuity, which can cause severe reflections. Just like an echo, the reflected signal can cause multiple signals or corrupted telegrams to appear on the line.


Reflections


Termination - Rules

To avoid reflections from the ends of the cable it is essential that each segment is terminated at the two ends and nowhere else. Two terminators in each segment must be powered at all times.


Termination

Standalone termination boxes are available. for DP, and for PA.

Termination on Repeaters


Termination

1 network with 2

segments.

DP/PA

coupler

#1 #0

#10 #11

#13 #14

#15

#16

#17

Power supply for PA segment

T T

T

T


Causes of Reflections

Missing terminator Un-powered terminator Terminator switch - faulty Extra terminator Reflection can also be caused by:

Un-certified devices. Cable length between two devices is too short. Spurs are used in high speed networks. Wrong types of cables are used. Cores are sharply bended.

Page 31



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, and Heavy earth currents on the cable screen.

2

1


Equipotential Bonding


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 Grounding 2

3 intern


Grounding of devices and shields

Connect the PROFIBUS cable shield to the equipotential bonding at every PROFIBUS station assuming local potentials are equal!

Shielded, twisted-pair cable

Cable shield route

to ground Rx

Tx Tx

Rx

Connector

Screw

terminals

Device Device

Red = +

Green = -


Wrong connectors

Which connectors are faulty?

A C B C


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

In general, the greater the spacing between the cables and the shorter the paths run parallel, the lower the risks of interference. 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 ?

An example: frequent converters. Can you spot the error here?

Power able route


Spot the errors


Use PROFIBUS connections - DP

3

2


Use PROFIBUS connections - PA

3

3

T Link/

Coupler T PROFIBUS DP PROFIBUS PA

Trunk

Spur lines

Devices

Link/

Coupler T PROFIBUS DP PROFIBUS PA T

Junction

Box

Junction

Box

Spur lines

Trunk

Devices


Spot the errors


Design considerations - details

Limitations of segment loads and total cable length Standalone terminations for DP, redundant power supply to terminators Network drawings – node addresses, position of termination, cable length between connectors and junction boxes, trunk cable and drop cable length Piggyback connectors – spare connection into EVERY segment for voltage measurements and troubleshooting


Design considerations - architecture

Which network to use – PROFIBUS, PROFINET, DP, PA, AS-i? Designation of safe and explosive 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 and maintenance Design documents and drawings

3

6


Installation Checklists

Checklist to determine network topology and obtain the network drawing Checklist for PROFIBUS DP (RS485) Grounding Checklist for PROFIBUS PA (MBP) Grounding Checklist for PROFIBUS DP (RS485) Cabling

3

7

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Practical steps to a successful PROFIBUS project

The very first step to a successful project should be

Training

PROFIBUS training courses are available for: Designers, Installers, Commissioning Engineers, and Maintenance staff.

Many industry sectors specify that their staff, contractors and sub contractors must be appropriately trained. PI Competence Centre - Manchester Metropolitan University, in-house or on-site training PI Training Centre – Verwer Training and Consultancy, on-site training for min. 6 people

3

8


Summary: Steps to a successfully project

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

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

3. Make sure that designers are fully aware of the methods for diagnosing and locating faults.

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

5. Follow the extensive guidance that is available from PI and from competency and training centres, for example, incorporating the checklists into your installation acceptance tests.

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Reference (Page 79)