1、 AMERICAN NATIONAL STANDARD ANSI/ISA-77.43.01-2014 Fossil Fuel Power Plant Unit/ Plant Demand Development Approved 22 December 2014 Copyright 2014 ISA. All rights reserved. ANSI/ISA-77.43.01-2014 Fossil Fuel Power Plant Unit/Plant Demand Development ISBN: 978-1-941546-35-2 Copyright 2014 by ISA. All
2、 rights reserved. Not for resale. Printed in the United States of America. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means (electronic mechanical, photocopying, recording, or otherwise), without the prior written permission of t
3、he Publisher. ISA 67 Alexander Drive P.O. Box 12277 Research Triangle Park, North Carolina 27709 3 ANSI/ISA-77.43.01-2014 Copyright 2014 ISA. All rights reserved. Preface This preface, as well as all footnotes and annexes, is included for information purposes and is not part of ANSI/ISA-77.43.01-201
4、4. In the 2014 edition, the title and purpose has been modified to make this standard applicable for once-through boilers. Thus, all references to “drum type” boiler have been removed. In the 2014 edition, the scope has been modified to include generation demand and turbine demand development and to
5、 change firing rate demand to boiler demand. The scope modification correctly identifies the content covered within the document and uses terms common to the industry. This document has been prepared as part of the service of ISA towards a goal of uniformity in the field of instrumentation. To be of
6、 real value, this document should not be static but should be subject to periodic review. Toward this end, the Society welcomes all comments and criticisms and asks that they be addressed to the Secretary, Standards and Practices Board; ISA; 67 Alexander Drive; P. O. Box 12277; Research Triangle Par
7、k, NC 27709; Telephone (919) 549-8411; Fax (919) 549-8288; E-mail: standardsisa.org. The ISA Standards and Practices Department is aware of the growing need for attention to the metric system of units in general, and the International System of Units (SI) in particular, in the preparation of instrum
8、entation standards. The Department is further aware of the benefits to USA users of ISA standards of incorporating suitable references to the SI (and the metric system) in their business and professional dealings with other countries. Toward this end, this Department will endeavor to introduce SI-ac
9、ceptable metric units in all new and revised standards, recommended practices, and technical reports to the greatest extent possible. IEEE/ASTM SI 10, American National Standard for Metric Practice, and future revisions, will be the reference guide for definitions, symbols, abbreviations, and conver
10、sion factors. It is the policy of ISA to encourage and welcome the participation of all concerned individuals and interests in the development of ISA standards, recommended practices, and technical reports. Participation in the ISA standards-making process by an individual in no way constitutes endo
11、rsement by the employer of that individual, of ISA, or of any of the standards, recommended practices, and technical reports that ISA develops. CAUTION ISA DOES NOT TAKE ANY POSITION WITH RESPECT TO THE EXISTENCE OR VALIDITY OF ANY PATENT RIGHTS ASSERTED IN CONNECTION WITH THIS DOCUMENT, AND ISA DIS
12、CLAIMS LIABILITY FOR THE INFRINGEMENT OF ANY PATENT RESULTING FROM THE USE OF THIS DOCUMENT. USERS ARE ADVISED THAT DETERMINATION OF THE VALIDITY OF ANY PATENT RIGHTS, AND THE RISK OF INFRINGEMENT OF SUCH RIGHTS, IS ENTIRELY THEIR OWN RESPONSIBILITY. PURSUANT TO ISAS PATENT POLICY, ONE OR MORE PATEN
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14、DITIONS. FOR MORE INFORMATION ON SUCH DISCLOSURES AND LETTERS OF ASSURANCE, CONTACT ISA OR VISIT WWW.ISA.ORG/STANDARDSPATENTS. OTHER PATENTS OR PATENT CLAIMS MAY EXIST FOR WHICH A DISCLOSURE OR LETTER OF ASSURANCE HAS NOT BEEN RECEIVED. ISA IS NOT RESPONSIBLE FOR IDENTIFYING PATENTS OR PATENT APPLIC
15、ATIONS FOR WHICH A LICENSE MAY BE REQUIRED, FOR CONDUCTING INQUIRIES INTO THE LEGAL VALIDITY OR SCOPE OF PATENTS, OR DETERMINING WHETHER ANY LICENSING TERMS OR CONDITIONS PROVIDED IN ANSI/ISA-77.43.01-2014 4 Copyright 2014 ISA. All rights reserved. CONNECTION WITH SUBMISSION OF A LETTER OF ASSURANCE
16、, IF ANY, OR IN ANY LICENSING AGREEMENTS ARE REASONABLE OR NON-DISCRIMINATORY. ISA REQUESTS THAT ANYONE REVIEWING THIS DOCUMENT WHO IS AWARE OF ANY PATENTS THAT MAY IMPACT IMPLEMENTATION OF THE DOCUMENT NOTIFY THE ISA STANDARDS AND PRACTICES DEPARTMENT OF THE PATENT AND ITS OWNER. ADDITIONALLY, THE
17、USE OF THIS DOCUMENT MAY INVOLVE HAZARDOUS MATERIALS, OPERATIONS OR EQUIPMENT. THE DOCUMENT CANNOT ANTICIPATE ALL POSSIBLE APPLICATIONS OR ADDRESS ALL POSSIBLE SAFETY ISSUES ASSOCIATED WITH USE IN HAZARDOUS CONDITIONS. THE USER OF THIS DOCUMENT MUST EXERCISE SOUND PROFESSIONAL JUDGMENT CONCERNING IT
18、S USE AND APPLICABILITY UNDER THE USERS PARTICULAR CIRCUMSTANCES. THE USER MUST ALSO CONSIDER THE APPLICABILITY OF ANY GOVERNMENTAL REGULATORY LIMITATIONS AND ESTABLISHED SAFETY AND HEALTH PRACTICES BEFORE IMPLEMENTING THIS DOCUMENT. The following people served as members of ISA77.43: NAME COMPANY M
19、. Cushing, Chair Siemens Industry Inc. J. Weiss, Managing Director Applied Control Solutions LLC D. Crow Invensys Foxboro R. Hubby Robert N. Hubby Consulting D. Lee ABB Inc. C. Taft Taft Engineering Inc. The following people served as voting members of ISA77: NAME COMPANY R. Hubby, Chair Robert N. H
20、ubby Consulting D. Lee, Chair ABB Inc. J. Weiss, Managing Director Applied Control Solutions Inc. J. Batug PPL Generation LLC G. Cohee Applied Control Systems D. Crow* Invensys Operations Management M. Cushing Siemens Industry Inc. R. Eng Mitsubishi Hitachi Power Systems A. Erickson Bibb and b) a si
21、ngle boiler or multiple boilers supplying a common distribution header, typical of an industrial power plant. Specifically excluded from consideration are: a) dispatch control; b) turbine/generator control (other than turbine demand); c) feedwater controls d) steam temperature controls (covered sepa
22、rately by ANSI/ISA-77.44.01, Fossil Fuel Power Plant Steam Temperature Controls); e) combustion controls (covered separately by ANSI/ISA-77.41.01, Fossil Fuel Power Plant Boiler Combustion Controls); f) steam distribution control systems; g) economic loading of boilers; and h) fluidized bed boilers.
23、 3 Definitions The following definitions are included to clarify their use in this standard and may not correspond to the use of the word in other texts. For other definitions, reference ISA-51.1, Process Instrumentation Terminology. 3.1 alarm: an audible and/or visible means of indication to the pl
24、ant operator of an equipment or process malfunction or abnormal condition requiring a response. 3.2 boiler: the entire vessel in which steam or other vapor is generated for use external to the vessel. This includes the furnace, consisting of waterwall tubes; the firebox area, including burners and d
25、ampers; the convection area, consisting of any superheater, reheater, and/or economizer sections or any combined thereof, as well as drums and headers. ANSI/ISA-77.43.01-2014 10 Copyright 2014 ISA. All rights reserved. 3.3 boiler follow mode: a mode of boiler/turbine control where the boiler respond
26、s to an energy demand requirement and controls boiler pressure by regulating boiler inputs. 3.4 coordinated control mode: a mode of boiler/turbine control that provides for the parallel operation of the boiler and the turbine as a unit to match generation to demand while maintaining boiler/turbine b
27、alance. 3.5 controller: any manual or automatic device or system of devices used to regulate a process within defined parameters. If automatic, the device or system responds to variations in a process variable. 3.6 differential pressure flow element: a measuring element that is inserted in a process
28、 flow path and used to create a pressure drop that is proportional to the square of the rate of flow. 3.7 firing rate: the rate of fuel combustion in a boiler. 3.8 first-stage pressure: the pressure within a steam turbine at the point where the steam exits the first row of turbine blades. The pressu
29、re at this point is closely proportional to the flow rate of steam through the turbine. First-stage pressure is also referred to as impulse pressure by some turbine manufacturers. 3.9 frequency: an electrical measurement of the number of cycles in a given period of time that an electrical current os
30、cillates. In the United States, the electrical system operates at a frequency of sixty Hertz (cycles/sec). 3.10 load: the rate of energy output, usually expressed as lb/hr (kg/s) of steam or megawatts of electrical generation. 3.11 load dispatch: a remotely developed signal transmitted to an electri
31、c generating units control system for the development of that units net generation requirement. 3.12 load index: signal representative of desired output energy flow rate. 3.13 mass steam flow: the mass flow rate of steam from the boiler derived either from direct process measurements and/or calculat
32、ions from other parameters. If volumetric steam flow rate measuring techniques are employed, the measured (indicated) flow shall be compensated for flowing steam density to determine the true mass steam flow rate. 3.14 megawatt: a unit of power measurement equal to one million watts. Turbine/generat
33、or capability is usually expressed in megawatts. 3.15 mode (submode): a particular operating state of a control system such as manual, automatic, remote, coordinated, etc. A mode is usually designed to achieve a desired control strategy. 11 ANSI/ISA-77.43.01-2014 Copyright 2014 ISA. All rights reser
34、ved. 3.16 redundant (redundancy): duplication or repetition of elements in electronic or mechanical equipment to provide alternative functional channels in case of failure of one of the device. 3.17 regenerative: a quality of signal that feeds back on itself (positive feedback), causing control syst
35、em instability. 3.18 runback: an action initiated by the loss of selected auxiliary equipment, in which the load is reduced automatically to a level which can be sustained with the remaining auxiliary equipment. 3.19 rundown: an action initiated by an undesirable operating condition, in which the lo
36、ad is reduced until the undesirable condition has cleared. 3.20 runup: an action initiated by an undesirable operating condition, in which the load is increased until the undesirable condition has cleared. 3.21 shall, should, and may: the word “shall“ is to be understood as a requirement, the word “
37、should“ as a recommendation, and the word “may“ as permissive, neither mandatory nor recommended. 3.22 steam header: pipe in which steam output from multiple boilers is collected and then distributed to various steam loads. 3.23 tracking: forcing an inactive control function to follow the active con
38、trol function so that upon a mode transfer, no process upset occurs. 3.24 turbine: a machine that converts energy from a moving fluid into rotating mechanical energy to drive a load. In a power plant, a turbine converts energy in the steam into mechanical energy to drive an electric generator (the l
39、oad) or an auxiliary, such as a boiler feedpump. 3.25 turbine follow mode: a mode of boiler/turbine control in which the turbine demand is adjusted to control the steam pressure out of the boiler. 3.26 turbine governor valves: the primary control valves used to regulate the flow of steam through the
40、 turbine during normal operation. 4 Minimum design requirements for unit/plant demand development control systems The unit/plant demand development portion of the total plant control system shall meet the operational requirements of the plant and shall correctly interface with the process to provide
41、 accurate, safe, and efficient plant control. To accomplish these objectives, the following requirements are defined as the minimum acceptable design. ANSI/ISA-77.43.01-2014 12 Copyright 2014 ISA. All rights reserved. 4.1 Process measurement requirements 4.1.1 Instrument installation for unit/plant
42、demand development Process-sensing devices should be installed as close as practical to the source of the measurement with appropriate design to prevent excessive vibration and temperature and to provide access for periodic maintenance. Recommendation for the location of instrument and control equip
43、ment connections can be found in “Recommended Instrument Connections“ published by SAMA/ABMA/IGCI (no longer in print, and no longer supported by SAMA, but available from MCAA). If instruments require impulse lines, then separate isolation valves and impulse lines shall be provided for each instrume
44、nt. 4.1.2 Measurement and conditioning 4.1.2.1 Measurement filtering Filtering techniques used to condition process measurements shall not compromise the speed of response of control. 4.1.3 Process measurements 4.1.3.1 Steam pressure measurement An appropriate steam pressure measurement shall be pro
45、vided for control. This may be steam header pressure, throttle pressure, or drum pressure, as required by the application. 4.1.3.2 Boiler output energy flow measurement Boiler output energy flow may be used in the demand development calculation. Energy flow may be calculated or measured in several d
46、ifferent manners including but not limited to: measurement of boiler output steam flow, measurement of turbine first-stage (impulse) pressure, or calculation of turbine governor valve(s) position. If a differential pressure flow element is used for the steam flow measurement, it shall be pressure an
47、d temperature compensated to determine the mass steam flow. 4.1.3.3 Megawatt and frequency measurement For coordinated mode (4.2.3), megawatts and frequency measurements shall be provided, if not a part of the turbine control system. 4.1.4 Measurement redundancy The following process measurements sh
48、all be redundant: a) steam pressure; and b) boiler output energy flow. When two measurements are employed, excessive deviation between the measurements shall be alarmed and the affected portion of the control system automatically transferred to manual. When three measurements are employed, the media
49、n measurement shall be used for control and excessive deviation between each measurement and the median shall be alarmed. 13 ANSI/ISA-77.43.01-2014 Copyright 2014 ISA. All rights reserved. 4.2 Control and logic requirements 4.2.1 Boiler follow 4.2.1.1 Single boiler units Single-element control (header or throttle pressure control only) is the minimum boiler follow mode required to match steam production to steam needs for the following applications: a) process of relatively slow load changes (e.g., building heating system); and b) process where constant steam
