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Introduction and brief history of SCADA This manual is designed to provide a thorough understanding of the fundamental concepts and the practical issues of SCADA systems. Particular emphasis has been placed on the practical aspects of SCADA systems with a view to the future. Formulae and details that can be found in specialized manufacturer manuals have been purposely omitted in favor of concepts and definitions. This chapter provides an introduction to the fundamental principles and terminology used in the field of SCADA. It is a summary of the main subjects to be covered throughout the manual. SCADA (supervisory control and data acquisition) has been around as long as there have been control systems. The first ‘SCADA’ systems utilized data acquisition by means of panels of meters, lights and strip chart recorders. The operator manually operating various control knobs exercised supervisory control. These devices were and still are used to do supervisory control and data acquisition on plants, factories and power generating facilities. The following figure shows a sensor to panel system.
Practical SCADA for Industry Titles in the series Practical Cleanrooms: Technologies and Facilities (David Conway) Practical Data Acquisition for Instrumentation and Control Systems (John Park, Steve Mackay) Practical Data Communications for Instrumentation and Control (John Park, Steve Mackay, Edwin Wright) Practical Digital Signal Processing for Engineers and Technicians (Edmund Lai) Practical Electrical Network Automation and Communication Systems (Cobus Strauss) Practical Embedded Controllers (John Park) Practical Fiber Optics (David Bailey, Edwin Wright) Practical Industrial Data Networks: Design, Installation and Troubleshooting (Steve Mackay, Edwin Wright, John Park, Deon Reynders) Practical Industrial Safety, Risk Assessment and Shutdown Systems (Dave Macdonald) Practical Modern SCADA Protocols: DNP3, 60870.5 and Related Systems (Gordon Clarke, Deon Reynders) Practical Radio Engineering and Telemetry for Industry (David Bailey) Practical SCADA for Industry (David Bailey, Edwin Wright) Practical TCP/IP and Ethernet Networking (Deon Reynders, Edwin Wright) Practical Variable Speed Drives and Power Electronics (Malcolm Barnes) Practical SCADA for Industry David Bailey BEng, Bailey and Associates, Perth, Australia +J]OT=XOMNZ MIPENZ, BSc(Hons), BSc(Elec Eng), IDC Technologies, Perth, Australia Newnes An imprint of Elsevier Linacre House, Jordan Hill, Oxford OX2 8DP 200 Wheeler Road, Burlington, MA 01803 First published 2003 Copyright 2003, IDC Technologies All rights reserved No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1T 4LP Applications for the copyright holder's written permission to reproduce any part of this publication should be addressed to the publisher British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 07506 58053 For information on all Newnes publications, visit our website at www.newnespress.com Typeset and Edited by Vivek Mehra, Mumbai, India (vivekmehra@tatanova.com) Printed and bound in Great Britain Contents Preface 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.1 2.2 2.3 2.4 2.5 2.6 xiii Background to SCADA Introduction and brief history of SCADA Fundamental principles of modern SCADA systems SCADA hardware SCADA software Landlines for SCADA SCADA and local area networks Modem use in SCADA systems Computer sites and troubleshooting System implementation 7 SCADA systems, hardware and firmware 11 Introduction Comparison of the terms SCADA, DCS, PLC and smart instrument 11 12 2.2.1 2.2.2 2.2.3 2.2.4 2.2.5 12 15 15 16 17 SCADA system Distributed control system (DCS) Programmable logic controller (PLC) Smart instrument Considerations and benefits of SCADA system Remote terminal units 17 2.3.1 2.3.2 2.3.3 2.3.4 2.3.5 2.3.6 2.3.7 2.3.8 2.3.9 2.3.10 2.3.11 2.3.12 2.3.13 19 19 26 27 28 29 31 33 33 33 33 34 35 Control processor (or CPU) Analog input modules Typical analog input modules Analog outputs Digital inputs Counter or accumulator digital inputs Digital output module Mixed analog and digital modules Communication interfaces Power supply module for RTU RTU environmental enclosures Testing and maintenance Typical requirements for an RTU system Application programs PLCs used as RTUs 36 36 2.5.1 2.5.2 2.5.3 37 38 40 PLC software Basic rules of ladder-logic The different ladder-logic instructions The master station 46 2.6.1 48 Master station software vi Contents 2.6.2 2.6.3 2.6.4 2.6.5 2.6.6 2.7 2.8 2.9 System SCADA software Local area networks Ethernet Token ring LANs Token bus network 48 48 49 51 52 System reliability and availability 52 2.7.1 52 Redundant master station configuration Communication architectures and philosophies 54 2.8.1 2.8.2 2.8.3 2.8.4 54 56 56 59 Communication architectures Communication philosophies Polled (or master slave) CSMA/CD system (peer-to-peer) Typical considerations in configuration of a master station SCADA systems software and protocols 61 64 3.1 3.2 Introduction The components of a SCADA system 3.3 The SCADA software package 67 3.3.1 3.3.2 3.3.3 70 72 72 3.2.1 3.4 3.5 3.6 SCADA key features Redundancy System response time Expandability of the system 64 64 65 Specialized SCADA protocols 72 3.4.1 3.4.2 3.4.3 3.4.4 3.4.5 73 74 78 80 81 Introduction to protocols Information transfer High level data link control (HDLC) protocol The CSMA/CD protocol format Standards activities Error detection 82 3.5.1 3.5.2 83 84 Causes of errors Feedback error control Distributed network protocol 87 3.6.1 3.6.2 3.6.3 3.6.4 3.6.5 3.6.6 3.6.7 3.6.8 3.6.9 3.6.10 3.6.11 3.6.12 87 87 87 88 88 88 88 88 89 92 96 97 Introduction Interoperability Open standard IEC and IEEE SCADA Development Physical layer Physical topologies Modes Datalink layer Transport layer (pseudo-transport) Application layer Contents vii 3.6.13 3.7 3.8 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 Conclusion 97 New technologies in SCADA systems 97 3.7.1 3.7.2 3.7.3 3.7.4 97 97 98 98 Rapid improvement in LAN technology for master stations Man machine interface Remote terminal units Communications The twelve golden rules Landlines 98 100 Introduction Background to cables Definition of interference and noise on cables Sources of interference and noise on cables 100 100 101 102 4.4.1 4.4.2 4.4.3 103 104 105 Electrostatic coupling Magnetic coupling Impedance coupling Practical methods of reducing noise and interference on cables 107 4.5.1 4.5.2 4.5.3 4.5.4 4.5.5 107 108 110 111 111 Shielding and twisting wires Cable spacing Tray spacing Earthing and grounding requirements Specific areas to focus on Types of cables 112 4.6.1 4.6.2 4.6.3 4.6.4 4.6.5 4.6.6 4.6.7 4.6.8 4.6.9 4.6.10 112 114 114 116 116 116 118 120 120 121 General cable characteristics Two wire open lines Twisted pair cables Coaxial cables Fiber optics Theory of operation Modes of propagation Specification of cables Joining cables Limitations of cables Privately owned cables 121 4.7.1 4.7.2 4.7.3 4.7.4 4.7.5 121 122 122 122 125 Telephone quality cables Data quality twisted pair cables Local area networks (LANs) Multiplexers (bandwidth managers) Assessment of existing copper cables Public network provided services Switched telephone lines 125 126 4.9.1 4.9.2 4.9.3 126 126 128 General Technical details DC pulses viii Contents 4.9.4 4.10 4.11 4.12 4.13 4.14 4.15 5.1 5.2 5.3 5.4 Dual tone multifrequency — DTMF 128 Analog tie lines 128 4.10.1 4.10.2 4.10.3 4.10.4 4.10.5 128 129 130 131 131 Introduction Four wire E&M tie lines Two wire signaling tie line Four wire direct tie lines Two wire direct tie lines Analog data services 131 4.11.1 4.11.2 4.11.3 4.11.4 4.11.5 4.11.6 4.11.7 132 132 132 133 134 134 135 Introduction Point-to-point configuration Point-to-multipoint Digital multipoint Switched network DATEL service Dedicated line DATEL service Additional information Digital data services 135 4.12.1 4.12.2 135 135 General Service details Packet switched services 136 4.13.1 4.13.2 4.13.3 4.13.4 4.13.5 136 138 138 139 139 Introduction X.25 service X.28 services X.32 services Frame relay ISDN ATM 139 141 Local area network systems 142 Introduction Network topologies 142 143 5.2.1 5.2.2 5.2.3 5.2.4 5.2.5 143 144 144 144 145 Bus topology Bus topology advantages Bus topology disadvantages Star topology Ring topology Media access methods 146 5.3.1 5.3.2 146 147 Contention systems Token passing IEEE 802.3 Ethernet 147 5.4.1 5.4.2 5.4.3 5.4.4 5.4.5 148 148 150 151 153 Ethernet types 10Base5 systems 10Base2 systems 10BaseT 10BaseF Contents ix 5.4.6 5.4.7 5.4.8 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12 10Broad36 1Base5 Collisions 153 153 153 MAC frame format High-speed Ethernet systems 154 155 5.6.1 155 Cabling limitations 100Base-T (100Base-TX, T4, FX, T2) 156 5.7.1 5.7.2 5.7.3 5.7.4 5.7.5 5.7.6 156 157 157 158 158 159 Fast Ethernet overview 100Base-TX and FX 100BASE-T4 100Base-T2 100Base-T hubs 100Base-T adapters Fast Ethernet design considerations 159 5.8.1 5.8.2 5.8.3 159 159 160 UTP Cabling distances 100Base-TX/T4 Fiber optic cable distances 100Base-FX 100Base-T repeater rules Gigabit Ethernet 1000Base-T 160 5.9.1 5.9.2 5.9.3 5.9.4 5.9.5 5.9.6 5.9.7 160 161 162 163 163 163 163 Gigabit Ethernet summary Gigabit Ethernet MAC layer 1000Base-SX for horizontal fiber 1000Base-LX for vertical backbone cabling 1000Base-CX for copper cabling 1000Base-T for category UTP Gigabit Ethernet full-duplex repeaters Network interconnection components 164 5.10.1 5.10.2 5.10.3 5.10.4 5.10.5 5.10.6 164 165 165 166 166 167 Repeaters Bridges Router Gateways Hubs Switches TCP/IP protocols 169 5.11.1 5.11.2 5.11.3 170 170 171 The TCP/IP protocol structure Routing in an Internet Transmission control protocol (TCP) SCADA and the Internet 172 5.12.1 5.12.2 5.12.3 5.12.4 5.12.5 173 173 174 175 175 Use of the Internet for SCADA systems Thin client solutions Security concerns Other issues Conclusion x Contents 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.11 7.1 7.2 Modems 176 Introduction Review of the modem 176 176 6.2.1 6.2.2 6.2.3 6.2.4 6.2.5 178 179 180 180 181 Synchronous or asynchronous Modes of operation Components of a modem Modem receiver Modem transmitter The RS-232/RS-422/RS-485 interface standards 182 6.3.1 6.3.2 6.3.3 6.3.4 6.3.5 6.3.6 6.3.7 6.3.8 6.3.9 182 183 185 185 186 187 188 188 190 The RS-232-C interface standard for serial data communication Electrical signal characteristics Interface mechanical characteristics Functional description of the interchange circuits The sequence of asynchronous operation of the RS-232 interface Synchronous communications Disadvantages of the RS-232 standard The RS-422 interface standard for serial data communications The RS-485 interface standard for serial data communications Flow control Modulation techniques 191 191 6.5.1 6.5.2 6.5.3 6.5.4 6.5.5 6.5.6 192 192 192 193 194 195 Amplitude modulation (or amplitude shift keying) Frequency modulation (or frequency shift keying — FSK) Phase modulation (or phase shift keying (PSK)) Quadrature amplitude modulation (or QAM) Trellis coding DFM (direct frequency modulation) Error detection/correction and data compression 196 6.6.1 6.6.2 6.6.3 196 197 198 MNP protocol classes Link access protocol modem (LAP-M) Data compression techniques Data rate versus baud rate Modem standards Radio modems Troubleshooting the system 201 202 203 207 6.10.1 6.10.2 6.10.3 6.10.4 207 208 208 209 Troubleshooting the serial link The breakout box Protocol analyzer Troubleshooting the modem Selection considerations Central site computer facilities 210 212 Introduction Recommended installation practice 212 212 7.2.1 212 Environmental considerations