1、jyr - jyi_ | -w m. -_- Tiftr JnyDu Book T-3 Automation and Telecommunications 1 DISPLAY COPY DONOTREMpVE GEOP Gas Engineering and Operating Practice Series ; GEOP i Gas Engineering and Operating Practice A Series by the Operating Section f The American Gas Association Volume II TRANSMISSION Book T-3
2、 Automation and Telecommunications The American Gas Association Arlington, Virginia I Legal Notice The Gas Engineering and Operating Practices Senea was prepared by the Amencan Gas Associatton (AJGA ), Its member companies and other individuals and KTOups with an interest in the natural gas industry
3、 Neither AGJV, Its member companies, employees, nor any person acting on their behalf a Makes any warranty or reapresentation. express or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this eenes, or that the use of any apparatus, method, or proces
4、s disclosed in this senes may not infnnge privately owned nghts, or b. Assumes any liability with respect to the use of or for damages or personal injuries resulting from the use of any mformation, apparatus, method, or process disclosed m this senes, or for violation of any federal, state or mimiQp
5、a) regulation with which it may conflict c Reference to trade namesor specific commercial products, methods, commodities or services in this senes does not represent or constitute an endorsement, recommendation or favonng hy AGA or any other pereon of the specific commercial product, commodity or se
6、rvice d Nothmg contained in this senes is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use in connection with any method apparatus, or product covered by letters patent, nor as insunng anyone against liability for mfnngement of letters patent Copy
7、right 1991 by the American Gas Association, A.G.A. All rights reserved. Library of Congress Catalog Card Number: 85-70460 ISBN 0-87257-007-X A.G.A. Catalog Number XY9106 1M06.91-138-69 Printed in the United States of America CONTENTS LIST OF FIGURES xi PREFACE xiiACKNOWLEDGEMENTS xv INTRODUCTION 1 C
8、HAPTER 1. PRINCIPLES OF PROCESS CONTROL 3 Definitions 3 Open-Loop Control System 4 Closed-Loop Control System 5 Proportional, Integral, Derivative Algorithm 9 The Process and Its Controllability 10 CHAPTER 2. MEASUREMENT OF PROCESS VARIABLES 13 General Sensor Characteristics 1Sensor Measurement Erro
9、r 3 Sensor Mechanical Characteristics 14 Pressure Measurement 15 General 1Mechanical Sensorsui IV AUTOMATION AND TELECOMMUNICATIONS Bourdon Tubes 16 BellowsDiaphragms and Capsules 18 Electromechanical Sensors 20 Temperature MeasurementGeneral 2Bimetellic Thermometers 21 Filled Thermal SystemsThermoc
10、ouples 26 Thermocouple Materials 27 Extension Wire 8 ApplicationResistance Temperature Detectors 28 Thermowells 29 Level Measurement 31 Sight GaugeFloat SwitchDisplacer 4 Radioactive Sensor 3Differential Pressure 7 Dry Leg 8 Wet Leg 9 Pneumatic Pressure Repeater 3Remote Pressure SealsCHAPTER 3. TRAN
11、SMITTERS (or TRANSDUCERS) 43 Definition 4Transmitter Outputs 44 Analog OutputElectricalPneumaticDigital Output 44 Transmitter SelectionFunctional Specifications 45 Temperature 4Environment 6 Classified Locations 4DampingOutput 4Performance Specifications (Accuracy) 46 Sensor Materials 48 CONTENTS V
12、Desired Features 48 Pressure Transmitters 9 Types of Pressure Measured 4Absolute and Gauge Pressure 9 Differential PressureBasic Description 4Electronic Implementation 50 Typical TransmitterSensors 51 Calibration 3 InstallationPneumatic Implementation 5Installation 53 Temperature Transmitters 5 Smar
13、t TransmittersCHAPTER 4. GAS CHROMATOGRAPHS 57 Operating Principles 5Signal Derivation and Analog Output 58 Interfacing with SCADA SystemsCHAPTER 5. POSITION ACTUATORS 61 Theory 6Types of Position Actuators 64 Pneumatic Spring and Diaphragm 6Pneumatic Piston 6HydraulicElectric-Hydraulic 5 Electric 6
14、Gas/Hydraulic Rotary Piston 6Design Considerations 65 CHAPTER 6. SUPERVISORY CONTROL AND DATA ACQUISITION (SCADA) 67 HistoryIllustrative Examples 68 Project Considerations 71 o VI AUTOMATION AND TELECOMMUNICATIONS Development Steps 71 Requirements Study 2 Integration 3 Design Considerations 7Master
15、StationGeneral 7Displays and Reports 74 Alarms 5 Database 6 Data Quality 77 External Interfaces 7Power Supply 8 EnvironmentManagement .- 79 CommunicationsData/Signal ConversionAnalog 80 Pulse Duration 8Variable Frequency 1 Analog ModulationDigital Modulation 8Multiplexing 83 Cycle Timing 4 Voice Fre
16、quency 8Frequency Division 5 Time DivisionProtocols 8Polling Schemes 88 Remote Locations 9 Remote Terminal Units (RTUs) 8Transmitters (Transducers) 91 Flow Calculation 9Transient Protection 2 Open Loop/Closed Loop Control 93 Local ControlRemote Control 94 Drawings 95 Power SourcesEnvironment 6 Maint
17、enanceCHAPTER 7. COMPUTER SYSTEMS 97 Digital Computer Systems 9CONTENTS vii Introduction 97 BackgroundTypes of Computers 98 ConfigurationsCorporate Computing 9 Gas Control/Central Control 100 Front-end Processors 102 Regional Control Systems 10Communications Concentrators/Subprocessors 102 Station-C
18、ontrol Systems 103 Remote Terminal Units 4 Central Applications Processors 105 Introduction 10Pipeline Modeling 10Load Forecasting 6 Data-Exchange Systems 107 Analog Computing DevicesPneumatic Analog Devices 108 Electronic Analog DevicesCHAPTER 8. COMMUNICATIONS SYSTEMS 109 General Principles 10Defi
19、nitionsCommunications Media 110 General 11Telephone Voice-Grade Circuits Ill Vhf/Uhf Radio IlMicrowave RadioSatellite Radio 112 Digital TransmissionAnalog vs Digital 11Telecommunications Example 112 Transmission Speeds 11Multiplexors 113 Telephone Systems 4 Voice-Grade Circuits 11Local Services 115
20、Long Distance Carriers 11Data ServicesVhf and Uhf Radio Systems 115 Types of System Technologies 116 vm AUTOMATION AND TELECOMMUNICATIONS One-way Paging Systems 116 Conventional SystemsSimplex and Simplex Repeater : 116 Duplex 117 Multichannel Trunked Systems 11Cellular Systems 11Multiple Address Sy
21、stems 117 Modulation Methods 118 Continuous-wave Modulation 119 Amplitude Modulation (AM) 11Double-Sideband Modulation (DSB) 119 Single-Sideband Modulation (SSB) 11Frequency and Phase Modulation FM and PM) 119 Pulse Modulation 120 Pulse Amplitude Modulation 12Pulse Duration Modulation 0 Pulse Positi
22、on Modulation 12Pulse Code ModulationSystem Planning and Design 120 Licensing 12System Reliability 121 Basic ConsiderationsOperating Frequency 122 Antenna Systems . 12Directive Gain 123 Feeder NetworksDesign Example 124 Microwave Radio Systems 5 General 12Role of Microwave Systems 126 HistoryAdvanta
23、ges 12Disadvantages 6 Elements of the Systems 127 Design Considerations 8 Propagation Reliability 12Space Diversity 129 Mure ProtectionRedundant Equipment 12Redundant Routing . 129 Maintenance 12Digital Techniques with Microwave Radio 130 Advantages 13CONTENTS ix Disadvantages 130 Pulse-Coded Modula
24、tion 13Baseband Signal Generation 131 Modulation Techniques 13Digital Hierarchy 13Satellite Radio Systems 2 CHAPTER 9: AUTOMATED METERrREADING SYSTEMS 135 Traditional Meter Reading 13The Meter Reader 135 Estimated and Special Readings 13Automated Meter Reading 136 Early Attempts 13Current Capabiliti
25、esTypes of AMR Systems 137 Radio-Transmission Systems 13Telephone-Transmission Systems 137 Call-in and Call-out DesignationsSystem Components 138 Typical AMR Systems 9 Radio-based System-Call-out Type 13Telephone-based Systems 13Call-out Type 139 Standard Call-in Type 140 Additional PTN Call-in Type
26、 14AMR Systems for Large Customers 140 REFERENCES 143 INDEX 145 LIST OF FIGURES 1. Open-loop control system 4 2. Closed-loop pressure control 6 3. Closed-loop flow control 7 4. Closed-loop pressure/flow control with high select 7 5. Three types of Bourdon sensing elements 17 6. Bellows sensing eleme
27、nt-differential-pressure type 18 7. Diaphragm and capsular sensing elements 19 8. Bimetallic thermometer 22 9. Filled-system thermometer 3 10. Filled-system thermometer with built-in compensation . 25 11. Filled-system thermometer with dual compensation 25 12. Typical thermocouple system 26 13. Plat
28、inum resistance temperature detector (RTD) 29 14. Thermowell 30 15. Sight gauge 2 16. Float switch-point level 33 17. Float switch-multiple level18. Displacer-type level detector 5 19. Radioactive-sensor level measurement (continuous-measurement type) 36 20. Level measurement in open vessels 8 21. D
29、ry-leg level measurement 40 22. Wet-leg level measurement23. Pressure repeater 41 xu AUTOMATION AND TELECOMMUNICATIONS 24. Remote-seal transmitter 41 25. Typical wiring configuration for electrical transmitters . 45 26. Bonded-strain-gauge sensor 527. Capacitive sensor 52 28. Typical arrangement of
30、calibration valves used with pneumatically implemented transmitters 54 29. Basic process-control loop 62 30. Relationship between actuator position and fluid flow 63 31. Simple SCADA system for monitoring pressure at a remote location 69 32. SCADA system for data communications over long distances b
31、y use of PDM converters 69 33. SCADA system with RTUs for communicating data for several parameters from each remote location 70 34. Example of SCADA scheme for a pressure-control requirement 71 35. Three types of anolog modulation: amplitude, frequency, and phase 82 36. Three types of digital modul
32、ation: pulse amplitude, pulse width, and pulse position 83 37. Typical multiplexing scheme using cycle-timing technique . 84 38. Example of frequency-division multiplexing 85 39. Format of Synchronous Data Link Control (SDLC) 87 40. Typical transmission of pressure measurement from field to home off
33、ice 113 41. Example of multiplexing five lines 114 PREFACE Arlington, Virginia, May 1991 Over the past two decades, we have witnessed vast changes in our abihty to accumulate, store, and transmit information. In this book, some of the most experienced practitioners of data collection and dis seminat
34、ion in the U.S. and Canada-all members of American Gas Asso ciations Automation and Telecommunications Committee-share with the reader the kowledge they have gained over their professional careers. They cover the hisorical aspects of the subject and the application of new technologies to the needs o
35、f the natural-gas industry. Automation and Telecommunications is the eighth book in a series of Gas Engineering and Operating Practices (GEOP) books covering supply, transmission, distribution, measurement, utilization, and tech nical services in the natural-gas industry. All are written in language
36、 directed to the informed non-specialist and are aimed at bridging the knowledge gaps between different occupational areas. While the books in the GEOP series were designed to offer broad, general treatment of their subjects, they contain Lists of Codes and Standards, References, and Bibliographies
37、that cite related literature to expand the books usefulness. Alsc the Indexes, compiled by members of A,G.A.s Library Services Committee under the direction of Anne C. Roess, librarian at Peoples Gas Light and Coke Company of Chicago, serve as a excellent reference aids. Gerald G. Wilson Robert L. P
38、arker Chairman, GEOP Task Group Editor xiii Robert L Parker IN MEMORIAM This book is dedicated to the memory of our good friend and associate Robert L. Parker, Editor of the GEOP series, who died on June 5, 1991. Bob joined A.G.A. in May 1980 as Manager, Engineering Series Publications. Known throug
39、hout the industry for his writing and editorial expertise, Bob was instrumen tal in producing eight of the eleven books in the GEOP series. He will be missed. ACIOSrOWLEDGEMENTS This book is a tribute to the many people in the industry who have advanced automation and telecommunications from an art
40、to a science and from a science to the goal of any technical effort: practical use. Those who have unselfishly devoted their time and talent to the preparation of this book include authors who penned the many individual contributions, section coordinators who combined the contributions into the majo
41、r sections of the book, reviewers who ensured technical ac curacy, editors who translated the original drafts into readily under standable text, and typists who composed the many revisions that the document underwent. Many people contributed in multiple capacities, so, without trying to identify the
42、ir roles, the following is a simple alphabetical list of the participants: Phil Alexander, Manager, Transmission Services, Southern National Gas Company Mike Bakes, Measurement Engineer, Mississippi River Transmission Corporation Ralph Barbakoff, Supervisory Engineer, Peoples Gas Light the output ma
43、y be an electrical, pneumatic, or other type of representation. Set point-A value at which a parameter of a controlled system is directed to operate. It may be adjusted manually by an oper ator, automatically by other control-system elements, or remotely via a communications system. 3 4 AUTOMATION A
44、ND TELECOMMUNICATIONS Controlled device-The system device that is modified by the controller to maintain the process at its desired value. It is manipulated in accordance with the information delivered to it by the control system. Controller-The device that accepts set-point and process-variable inf
45、ormation as input and computes a desired output for the controlled device. Open-loop control system-A control system wherein informa tion measured from the process is not used to provide automatic corrective action for errors in the position of the controlled device. Closed-loop control system-A con
46、trol system wherein infor mation measured from the process is used to provide automatic corrective action for errors in the position of the controlled device. OPEN-LOOP CONTROL SYSTEM Figure 1 is an example of an open-loop control system used to in ject odorant into a gas stream. The control system,
47、 based on a digital flow computer with extended control capabilities, has the following functions: The flow computer calculates the instantaneous flow rate of the gas flow in engineering units of millions of cubic feet per hour (Mcfh). The flow computer converts the flow rate as a percentage of the
48、maximum gas flow rate expected through the system. r L Functions provided m digital flow computer n Flow Engineering Computalion - Units Engineettng II Units Sel Point Controller Pump J Flow i Ondcc Figure 1. Open-loop control system. PRINCIPLES OF PROCESS CONTROL 5 The flow computer performs an eng
49、ineering-unit conversion of the set point, expressed in pounds of odorant per hour per million cubic feet of gas per hour, to a percentage. The percentage is based on the maximum available flow rate and maximum available odorant pump rate. The flow computer includes a controller function that multiplies the set point in percent times the flow rate in percent to provide a required injection rate percent of maximum pumping rate. The flow computer drives an odorant pump with an output pump ing rate that can be set from zero to maximum by the output func
