wimes_3_02ai1

WATER INDUSTRY MECHANICAL AND ELECTRICAL

SPECIFICATION 3.02(A)

PROFIBUS AND OPTICAL FIBRE NETWORK DESIGN

WIMES 3.02(A) ISSUE 1

JULY 2008

Copyright 2008, ESR Technology. All rights reserved. No part of this document may be reproduced in any form electronic or mechanical, including photocopying, recording or any other information storage and

retrieval system without permission in writing from the Pump Centre.

The Pump Centre is a Centre of Excellence within ESR Technology, one of the UKs leading engineering, safety and risk consultancies. ESR Technology provides independent technical expertise to help its customers ensure asset integrity, improve machine reliability, manage safety and risk and transfer best practice.

WATER INDUSTRY MECHANICAL AND ELECTRICAL

SPECIFICATION 3.02(A)

PROFIBUS AND OPTICAL FIBRE NETWORK DESIGN

Prepared by:

Roger Marlow Pump Centre

With technical support and co-operation from the WIMES Electrical Working Group consisting of:

J Hughes Anglian Water P Davison Northern Ireland Water J Summers Dwr Cymru T Strong Northumbrian Water T Nicol Scottish Water S Ellis Severn Trent Water R Lennox South West Water M Jones Southern Water A Bailey/D Watkins Thames Water K Waud Three Valleys Water C Lomax United Utilities C Mildren Wessex Water R Rennie Yorkshire Water

Please Note

This Specification will be reviewed periodically to take account of feedback from Water Companies/Suppliers. If changes to the document are necessary, it will be re-issued.

Acknowledgments

The Authors of this Specification are grateful to Profibus International for their guidance and assistance in the preparation of this document.

WIMES 3.02 (A) PROFIBUS & OPTICAL FIBRE NETWORK DESIGN Page 1

ISSUE 1 JULY 2008

CONTENTS 1.0 SCOPE 2 2.0 PROFIBUS DP NETWORKS 2

2.1 General 2 2.2 Network Design 2

2.2.1 General 2 2.2.2 Topology 2 2.2.3 Termination 4 2.2.4 Spur Lines 5 2.2.5 Cable Length Considerations (Based on a Design Baud Rate of 1.5 Mbit/s) 5

2.3 Component Selection 5 2.4 Network Installation 5 2.5 Earthing and Equipotential Bonding 5

3.0 PROFIBUS PA NETWORKS 5 3.1 General 6 3.2 Network Design 6

3.2.1 General 6 3.2.2 Topology 6 3.2.3 Termination 7 3.2.4 Spur Lines 7 3.2.5 Cable Length Considerations 8 3.2.6 Intrinsically Safe Considerations - Profibus PA in Hazardous Areas 8

3.3 Component Selection 8 3.4 Network Installation 8 3.5 Earthing and Equipotential Bonding 8

4.0 OPTICAL FIBRE NETWORKS 8 4.1 General 8 4.2 Network Design 9 4.3 Component Selection 9 4.4 Network Installation 9

5.0 DESIGN VERIFICATION AND NETWORK TESTING 9 APPENDIX A - SPECIFICATIONS AND STANDARDS REFERENCED 10 APPENDIX B GUIDANCE NOTES 11

WIMES 3.02(A) PROFIBUS AND OPTICAL FIBRE NETWORK DESIGN Page 2

ISSUE 1 JULY 2008

1.0 SCOPE

This Specification defines the requirements for the design of Profibus DP, Profibus PA and optical fibre networks in the Water Industry.

The installation of Profibus DP, Profibus PA and optical fibre networks is covered by Section 9.4 of WIMES 3.02.

2.0 PROFIBUS DP NETWORKS

Profibus DP (decentralised periphery) is one of the well proven, widely accepted Profibus family of fieldbus communications protocols. It utilises EIA RS 485 as its transmission technology; which is a two wire data transmission technology using screened twisted pair cable.

2.1 General

1. The design of the network shall comply with the latest editions (current at the time of Tender) of all relevant International, Harmonised European and British Standards, including:

a) IEC 61158-2 - Industrial communication networks - Fieldbus specifications Part 2: Physical layer specification and service definition; and

b) BS EN 50174-1: 2001 - Information technology. Cabling installation. Specification and quality assurance.

Refer to Appendix A for a list of the Regulations, Standards and Specifications referenced in this Specification.

2.2 Network Design

2.2.1 General

1. The network shall be designed for a baud rate of 1.5 Mbits/s.

2.2.2 Topology

2.2.2.1 General

1. The network shall comprise a number of segments.

2. Each segment shall comprise a number of devices (or nodes) and shall be configured as a linear bus with the network cable daisy chaining from device to device.


ISSUE 1 JULY 2008

3. The specification of the EIA RS 485 data transmission system dictates that a maximum number 32 devices (masters and slaves) may be incorporated within a given segment. In practice, however, the number of devices incorporated within a given segment shall be limited to 25 to allow for:

a) Spare segment capacity i.e. the incorporation of additional devices; b) Network expansion (necessitating the use of repeaters (refer to Section 2.2.2.2,

below)); and c) The connection of diagnostic/programming equipment to the segment.

4. To facilitate network analysis and troubleshooting, each segment shall incorporate at least one connector with a piggyback socket, to enable monitoring and programming equipment to be connected to the network without causing network disruption. The piggyback socket shall only be attached to a device which can supply the required operating current to the monitoring and programming equipment. Piggyback sockets shall not be used for adding further devices to the network, as this would introduce a spur line.

2.2.2.2 Use of Repeaters/OLMs

1. If there is a requirement to incorporate more than 25 devices within the network, the network may be extended (thus increasing the number of segments) by the use of repeaters or optical link modules (OLMs) as shown in Figure 1, below:

Figure 1 Use of Repeaters and Optical Link Modules to Produce a Complex Network Structure


ISSUE 1 JULY 2008

2. Repeaters/OLMs may also be incorporated into the network when:

a) There is a need to electrically isolate sections of the network; and/or b) A segment exceeds the maximum permissible cable length for a baud rate of

1.5 Mbit/s.

3. Repeaters/OLMs shall be powered at all times.

4. It should be noted that repeaters/OLMs do count towards the 25 device limit for a given segment.

5. A maximum of 4 repeaters/OLMs shall be used between any master and slave device, unless the repeater/OLM manufacturers specifications state otherwise.

6. Repeaters shall be connected to the network so that the piggyback socket can be used to examine the signals on the outgoing segment. This normally means that the DP 1 repeater connection will be used for the outgoing segment and the DP2 connection will be used for the incoming segment.

2.2.3 Termination

1. To avoid reflections from the ends of the cables, the network shall be effectively terminated.

2. Network termination shall be provided by separate active terminators. The advantage of using separate active terminators, as opposed to termination resistors within connectors, is that any device can be removed/replaced without disturbing the network.

3. Active terminators shall be installed at the beginning and the end of each segment, as shown in Figure 2 below:

AT Slave Slave Master Slave Slave

R

SlaveSlaveSlaveSlaveSlaveAT

No additional terminations AT Active Terminator

R - Repeater

Figure 2 Use of Separate Active Terminators

Note If the master is located at the beginning of a segment, it shall usually incorporate the active terminator.


ISSUE 1 JULY 2008

4. Active terminators shall be powered at all times (refer to Guidance Notes).

5. Active terminators do not count towards the 25 device limit for a given segment.

6. To avoid additional reflections, termination resistors within connectors or devices shall always be disabled. This shall normally be done after all network testing and commissioning activities have been completed.

2.2.4 Spur Lines

1. As far as reasonably possible, spur lines shall be avoided within the network because they can cause reflections. If spur lines cannot be avoided, the total length of all spur lines within an individual network segment shall not exceed 6.7 m (based on a design baud rate of 1.5 Mbit/s). Within this figure of 6.7 m, suitable allowance shall be made for the lengths of any internal spurs which may exist within devices (e.g. actuators etc.) and also for any test equipment which may be connected to the network.

2.2.5 Cable Length Considerations (Based on a Design Baud Rate of 1.5 Mbit/s)

1. The maximum length of an individual network segment shall be 200 m.

2. To avoid reflections, there shall be a minimum cable length of 1 m between any two devices.

2.3 Component Selection

Refer to Section 9.4.2.2 of WIMES 3.02.

2.4 Network Installation


2.5 Earthing and Equipotential Bonding


3.0 PROFIBUS PA NETWORKS

Profibus PA (Process Automation) is one of the well proven, widely accepted Profibus family of fieldbus communications protocols.

Profibus PA networks utilise MBP (Manchester-encoded, Bus Powered) transmission technology, which is a 2-wire technology combining the functions of data transmission and power supply in a single network cable.


ISSUE 1 JULY 2008

3.1 General


a) IEC 61158-2 - Industrial communication networks - Fieldbus specifications Part 2: Physical layer specification and service definition; and

b) BS EN 50174-1: 2001 - Information technology. Cabling installation. Specification and quality assurance.


3.2 Network Design

3.2.1 General

1. The network is designed to operate at a baud rate of 31.25 Kbits/s.

3.2.2 Topology

1. A typical Profibus PA segment is shown in Figure 3 below:

Figure 3 Profibus PA Topology

2. As shown in Figure 3, each segment shall be configured in a trunk and spur topology, with each device (or slave) being connected to the trunk cable via a spur cable and T-connector/junction box.


ISSUE 1 JULY 2008

3. The specification of the MBP transmission technology dictates that a maximum number of 32 devices may be incorporated within a given segment. In practice, however, the number of devices shall generally be limited to 20 to allow a maximum spur length of 30 m between the trunk cable and a given device (refer also to Section 3.2.4).

4. As shown in Figure 3, each segment shall be connected to the Profibus DP network via a link/interface module and one or more DP/PA couplers, which will allow the DP network to run at high speed, independently of the PA network baud rate. A single DP/PA coupler shall be used for simple networks, whereas a link/interface module and multiple DP/PA couplers shall be used for more complex networks. A number of DP/PA couplers may be connected to each link/interface module (refer to Guidance Notes).

5. The link/interface module provides power for the PA network and shall therefore be powered at all times.

3.2.3 Termination

1. To avoid reflections from the ends of the cable, each segment shall be terminated at both ends of the segment and nowhere else with a suitable terminator which shall comprise a capacitor and resistor in series connected between the cable cores.

2. As shown in Figure 3, terminators shall be installed at the ends of the trunk cable only (i.e. not at the ends of any spur cables). Most DP/PA couplers incorporate a built in terminator which, by default, will ensure that a terminator is present at one end of the trunk cable. The other terminator shall then be installed in the last or furthest device, or preferably in the last junction box.

3. Terminators shall not be powered.

3.2.4 Spur Lines

1. The recommended length of each individual spur cable shall comply with the following table:

Number of Spur Lines Maximum Spur Length (non-intrinsically safe

installation) Maximum Spur Length

(intrinsically safe installation)

25 to 32 1 m - 19 to 24 30 m - 15 to 18 60 m - 13 to 14 90 m - 1 to 12 120 m 30 m

Note - It is not normally practical to incorporate more than 12 devices in an IS network, due to the limitations imposed on the power supply.


ISSUE 1 JULY 2008

3.2.5 Cable Length Considerations

1. The maximum length of an individual network segment (including all branches and spur cables) shall not exceed 1900 m, however, the particular characteristics of the segment power supply and/or requirements for intrinsic safety may reduce this significantly.

3.2.6 Intrinsically Safe Considerations - Profibus PA in Hazardous Areas

1. PA segments shall be designed to be intrinsically safe by ensuring that all devices are certified for intrinsic safety and that the cable and terminations also meet the requirements of intrinsic safety.

2. The Fieldbus Intrinsically Safe Concept (FISCO) (as detailed in BS EN 60079-27) shall be used in system design (refer to Guidance Notes).





3.5 Earthing and Equipotential Bonding


4.0 OPTICAL FIBRE NETWORKS

4.1 General


a) BS EN 50174-1:2001 - Information technology. Cabling installation. Specification and quality assurance.



ISSUE 1 JULY 2008

4.2 Network Design

1. The usual approach in designing an optical fibre network shall be as follows:

a) Determination of the transmission path length; b) Selection of the most appropriate type of optical fibre cable according to the

required transmission path length; c) Selection of suitable devices for the chosen optical fibre cable; and d) Selection of suitable connectors for the chosen devices.

2. Plastic Optical Fibres or PCF/HCS (Plastic Clad silica Fibre)/Hard Clad silica Fibre) optical fibres may be used at the same optical interface. Multimode and single mode optical fibres require their own interface design.





5.0 DESIGN VERIFICATION AND NETWORK TESTING

Refer to Section 9.4.5 of WIMES 3.02.


ISSUE 1 JULY 2008

APPENDIX A - SPECIFICATIONS AND STANDARDS REFERENCED

Standards

IEC Series

IEC 61158-2 - Industrial communication networks - Fieldbus specifications Part 2: Physical layer specification and service definition;

BS EN Series

BS EN 50174-1: 2001 - Information technology. Cabling installation. Specification and quality assurance; BS EN 60079-27 - Electrical apparatus for explosive gas atmospheres. Fieldbus intrinsically safe concept (FISCO) and fieldbus non-incendive concept (FNICO).

Specifications

WIMES

WIMES 3.02 Low Voltage Electrical Installations.

WIMES 3.02(A) PROFIBUS & OPTICAL FIBRE NETWORK DESIGN Page 11

ISSUE 1 JULY 2008

APPENDIX B GUIDANCE NOTES

Clause 2.2.3.4

Active terminators should be used to provide segment termination instead of the termination resistors provided in the connectors/devices. Active terminators are standalone Profibus DP components and require a 24 V DC power supply.

Clause 3.2.2.4

The DP/PA link acts as a slave on the DP network and a master on the PA network, decoupling all data communication on the network. This means that DP and PA networks can be combined without influencing the processing performance of the DP network.

The DP/PA link enables the addressing capacity of the network to be considerably increased due to the fact that a large number of field devices can be connected to a DP/PA link, but the link only reserves one DP address.

Ex and non-Ex rated PA segments can be connected to the DP network by connecting Ex and non-Ex versions of the DP/PA coupler into the link/interface module. Ex couplers incorporate protection barriers to limit the current and voltage supplied to an IS segment.

Connection of the link/interface module to the DP network is via a single 9-pin Sub-D connector (the DP interfaces of the DP/PA couplers are redundant).

Clause 3.2.6.2

Significant care should be taken when designing segments if PROFIBUS PA is to be used in hazardous areas. The FISCO (Fieldbus Intrinsically Safe Concept) model can make planning, installing and expanding PROFIBUS networks in hazardous areas significantly easier. The model is based on the concept that a network segment can be considered intrinsically safe (with no separate intrinsic safety calculation required) if the voltage, current, power, inductance and capacitance values of the relevant components (cable, segment couplers, bus terminators) are within the boundaries of prescribed FISCO limits and all field devices are FISCO certified.

FISCO power supplies limit the available output power to a given segment, however, in addition, the voltage is limited which allows greater current to be delivered to the segment, hence more devices can be used.

The FISCO model enforces the following restrictions:

Each segment has only one source of power; Each field device consumes a constant basic current of at least 10 mA; The field devices act as passive current sinks; even when a station is transmitting, no

power is fed into the bus; Device internal capacitance and inductance is limited to < 5 nF and 10 H; The total cable length limited to 1000 m (including spurs); and Individual spur lines are limited to a maximum length of 30 m.

WIMES 3.02(A) PROFIBUS & OPTICAL FIBRE NETWORK DESIGN Page 12

ISSUE 1 JULY 2008

Components and instrumentation by various manufacturers can be operated on the same segment provided that all of them meet the requirements described. Intrinsic safety is considered proven if all stations on an electrical circuit have been certified in accordance with FISCO as defined in IEC/BS EN 60079-27.

Intrinsically safe DP/PA couplers incorporate barriers that provide current and voltage limiting (a typical coupler for EEx ia gas group IIC might provide 110 mA at 13 V which would limit the number of devices to 7 or 8 per segment (compared to 32 devices for a non-hazardous application).

For further information on the Water Industry Mechanical and Electrical Specifications please contact: The Pump Centre ESR Technology plc Whittle House Birchwood Park Warrington Cheshire WA3 6FW Telephone: +44 (0) 1925 843457 Facsimile: +44 (0) 1925 843500 Email: [email protected] WWW: www.pumpcentre.com/wimes.htm

Title PageCreditsContact DetailsCONTENTS1.0 SCOPE2.0 PROFIBUS DP NETWORKS2.1 General2.2 Network Design2.2.1 General2.2.2 Topology2.2.3 Termination2.2.4 Spur Lines2.2.5 Cable Length Considerations (Based on a Design Baud Rate of 1.5 Mbit/s)

2.3 Component Selection2.4 Network Installation2.5 Earthing and Equipotential Bonding

3.0 PROFIBUS PA NETWORKS3.1 General3.2 Network Design3.2.1 General3.2.2 Topology3.2.3 Termination3.2.4 Spur Lines3.2.5 Cable Length Considerations3.2.6 Intrinsically Safe Considerations - Profibus PA in Hazardous Areas

3.3 Component Selection3.4 Network Installation3.5 Earthing and Equipotential Bonding

4.0 OPTICAL FIBRE NETWORKS4.1 General4.2 Network Design4.3 Component Selection4.4 Network Installation

5.0 DESIGN VERIFICATION AND NETWORK TESTINGAPPENDIX A - SPECIFICATIONS AND STANDARDS REFERENCEDAPPENDIX B GUIDANCE NOTES

wimes_3_02ai1

Documents