1、 STANDARD ANSI/ISA77.14.01-2010 Fossil Fuel Power Plant Steam Turbine Controls Approved 10 November 2010ANSI/ISA77.14.01-2010 Fossil Fuel Power Plant Steam Turbine Controls ISBN: 978-1-936007-67-7 Copyright 2010 by ISA. All rights reserved. Not for resale. Printed in the United States of America. No
2、 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 the Publisher.Copyright 2010 ISA. All rights reserved. 3 ANSI/ISA77.14.01-20
3、10 Preface This preface, as well as all footnotes and annexes, is included for information purposes and is not part of ANSI/ISA77.14.01-2010. The standards referenced within this document may contain provisions, which, through reference in this text, constitute requirements of this document. At the
4、time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this document are encouraged to investigate the possibility of applying the most recent editions of the standards indicated within this document. Members of IEC and ISO m
5、aintain registers of currently valid International Standards. ANSI maintains registers of currently valid U.S. National Standards. This document has been prepared as part of the service of ISA, The International Society of Automation, toward a goal of uniformity in the field of instrumentation. To b
6、e of 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
7、 Park, 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 in
8、strumentation 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
9、SI-acceptable metric units in all new and revised standards, recommended practices, and technical reports to the greatest extent possible. Standard for Use of the International System of Units (SI): The Modern Metric System, published by the American Society for Testing one or more valve(s) opening
10、following another. See partial arc. 3.27. Shall and should: The word “SHALL” is to be understood as a REQUIREMENT; the word “SHOULD” as a STRONG RECOMMENDATION. 3.28. Single-valve mode: Control valves opening simultaneously. See full arc. 3.29. Speed control: Closed-loop control of turbine speed (RP
11、M) before synchronization. 3.30. Speed droop: The ratio of the percentage speed change to the resulting percentage valve-position change. Speed droop is inversely proportional to the steady-state gain of the speed controller. 3.31. Stop valve: A valve or set of valves used to shut off steam flow to
12、the turbine during turbine shutdown. The stop valves are tripped closed by the turbine protection system. In some applications, these valves are used to regulate steam flow during startup. 3.32. Synchronization: The process of matching frequency, phase, and voltage between the turbine generator and
13、the utility grid to allow proper breaker closure. 3.33. Turbine control system (TCS): Decision-making equipment with its associated power supplies, control processor(s), I/O hardware, and sensing devices that monitor and control the turbine. 3.34. Throttle pressure: See inlet pressure. 3.35. Throttl
14、e valve: See stop valve. 3.36. Trip: An action where all of the steam turbine valves are closed as quickly as possible. This can occur as a result of an emergency condition or as part of a normal shutdown. 3.37. Valve position limiter: See load limiter. Copyright 2010 ISA. All rights reserved. ANSI/
15、ISA77.14.01-2010 12 3.38. Valve position control: A control mode in which the load demand is directly translated into valve position demand without closed loop load feedback within the turbine controller. However, some turbine valve actuators may require a closed loop positioning system. 4. Design r
16、equirements 4.1. Instrumentation Process-sensing devices (see Figure 4.Error! No text of specified style in document.1 - Turbine instrumentation) should be installed as close as practical to the source of the measurement with appropriate design to prevent excessive vibration and temperature and to p
17、rovide access for periodic maintenance. Separate isolation valves and impulse lines should be run to each pressure-sensing device used for control. Figure 4.Error! No text of specified style in document.1 - Turbine instrumentation (typical) ST101HPGeneratorIPJT101ST102ST103Re-heaterLPHStopValveZT101
18、HControlValveZT102PT102PT101CondenserReheatStop ValveZT103InterceptValveZT1044.1.1. Speed sensing A minimum of three speed-sensing devices (probes) shall be used for speed control (ST-101, 102, 103). At least one of these speed probes shall be capable of reading turning-gear speed. An additional ins
19、talled spare-speed probe should be supplied. When the backup overspeed trip system is an electronic design (refer to section 4.2), the speed probes used by the turbine control system shall be independent of those used by a backup electronic overspeed trip system. 4.1.2. Valve position Feedback shall
20、 be instrumented for all valves controlled by the turbine control system: stop (ZT101), control (ZT102), reheat stop (ZT103), and intercept valves (ZT104). LVDTs or similar measurement devices shall be used for modulating valves. Limit switches are acceptable for valves whose position is not modulat
21、ed. Copyright 2010 ISA. All rights reserved. 13 ANSI/ISA77.14.01-2010 4.1.3. Steam pressures Inlet-pressure transmitter (PT-101). First-stage pressure transmitter (PT-102). 4.1.4. Generator Megawatt transducer (JT-101). Generator breaker status 4.1.5. Turbine trip status Typically a pressure signal
22、on the trip oil header. 4.2. Overspeed trip system Two independent turbine overspeed trip systems shall be provided: The primary system shall be within the turbine control system; the backup system shall be either a mechanical overspeed trip device or an electronic overspeed trip system as defined b
23、y the American Petroleum Institute standard, API 670. The backup overspeed trip system shall be capable of tripping the turbine without the involvement of the turbine control system. Speed sensing devices (probes) used by the turbine control system shall be independent of those used by a backup elec
24、tronic overspeed trip system. The turbine control system and the electronic overspeed trip system, when utilized as the backup system for the overspeed trip function, shall perform the trip function through independent solenoids. A multi-toothed surface for speed sensing shall be provided integral w
25、ith or securely attached to the turbine shaft. Sharing this surface between the turbine control system, a backup electronic overspeed trip system, and a tachometer shall be permitted. Details of the speed sensing measurement shall follow API 670. 4.3. Turbine control system design 4.3.1. Architectur
26、e The turbine control system design should be fault tolerant. The failure behavior of components shall be considered and incorporated in the design. The turbine control system shall be designed to be failsafe. The turbine control system functions shall reside in a dedicated controller that is segreg
27、ated from other plant functions. 4.3.1.1. Diagnostics The control system design shall include diagnostics to monitor and alarm any component failures, including: processor, data transfer, input or output hardware, and power supplies. Diagnostics shall be included to monitor and alarm any analog inpu
28、t (4-20mA, T/Cs, RTDs, etc.) signal failure. Copyright 2010 ISA. All rights reserved. ANSI/ISA77.14.01-2010 14 4.3.2. Data archival Archival of turbine control system data is used for performance analysis and not intended for sequence of event analysis. The data update period for data archival shall
29、 not exceed 1 sec. The minimum data to be archived include: a) turbine speed; b) generator load; c) first-stage steam pressure; d) inlet steam pressure; e) valve positions; f) controller outputs; g) active control mode; and h) trip-system status. 4.3.3. Security Changes to the turbine control system
30、s logic shall be protected from unauthorized access. Tunable values and parameters shall have restricted access. 4.4. Turbine control system functions 4.4.1. Turbine reset Once all of the trip conditions have been cleared, the operator shall be able to initiate a reset of the turbine. Reset of the t
31、urbine is a prerequisite to complete the reset sequence before attempting speed control. Upon confirmation the turbine is reset (turbine trip status input cleared), all steam admission valves that are not used to control speed for the selected steam admission mode shall ramp open. Refer to Section 4
32、.4.16 for a definition of possible steam admission modes based on OEM design. The turbine control system shall include interlocks to ensure valves open in a sequence in accordance with the OEM design. 4.4.2. Normal range speed control The turbine speed control described in this section shall provide
33、 closed-loop speed control from zero speed through rated speed when the main generator breaker is open. The speed control system shall use a median-signal select of the three speed sensors. Speed-sensor voting shall switch from median-signal to high-signal select if a speed-sensor fault condition ex
34、ists. The turbine control system shall automatically transfer to speed control mode when the turbine is initially reset and when the other speed control permissives are satisfied. When this occurs, the speed control setpoint shall be automatically set to no greater than the current turbine speed. Co
35、pyright 2010 ISA. All rights reserved. 15 ANSI/ISA77.14.01-2010 After the turbine is reset, the turbine control system shall control turbine speed to maintain an operator adjustable setpoint in RPM. The speed controller shall provide at a minimum the equivalent of proportional plus integral control
36、action. This type of control ensures zero speed error under steady-state conditions. The operator shall have the capability of ramping the speed control setpoint at a minimum of three selectable rates expressed in RPM/min. Implementing the ramp as an operator function within predefined limits shall
37、be permitted. The turbine control system shall accommodate an external speed setpoint function (e.g. from an automated turbine startup system). The input from the external system shall be limited by the TCS to reasonable ranges and rates and shall be either a hardwired input or a digital data interf
38、ace with a data update period not to exceed 500 msec. A method shall be implemented to prevent turbine speed from operating continuously in a critical vibration window. The turbine control system shall assume speed control of the turbine when the generator breaker opens, and the speed setpoint at th
39、at time shall be the rated speed of the turbine. The speed controller shall provide stable control at all times and regulate within plus or minus one RPM of setpoint during steady speed conditions. On turbines where a steam admission valve transfer occurs before rated speed is reached, the speed con
40、trol system shall be designed to accomplish this transfer with an upset to the actual turbine speed of less than one percent of rated speed. 4.4.3. Overspeed functions The overspeed functions included in the turbine control system shall use the same speed sensors as the normal range speed control. A
41、n overspeed trip condition shall be sensed by two out of three voting of the three speed sensor circuits from the normal range speed control signal. A failed speed sensor circuit shall be voted as an overspeed condition for that sensor. The overspeed trip setpoint shall be a restricted access parame
42、ter. A means of testing and verification of all overspeed trip systems shall be provided. The turbine control system shall have provisions, if necessary, to test the backup overspeed trip system. Activation of online testing functions shall have safeguards to prevent inadvertent operation. Based on
43、the unit size and turbine OEM, there may be several additional overspeed protection functions (e.g. pre-emergency governor, load-drop anticipator, power-load unbalance) that require additional measurements (e.g. reheat pressure and generator current). This functionality shall be incorporated into th
44、e control system design. 4.4.4. Synchronization The turbine control system shall be capable of receiving demand signals for speed setpoint changes during synchronization. This demand input shall be separate from the operator speed control inputs in order to allow different gains, limits, and permiss
45、ives. 4.4.5. Initial megawatt pick-up Upon generator breaker closure, the turbine control shall initiate a step change in flow demand to establish load on the generator. This action shall be a step function and is not subject to the loading rate. After load is established, this function shall have n
46、o further action. Initial megawatt pick-up settings shall be restricted access parameters. These parameters shall be implemented as a function of inlet steam pressure. Copyright 2010 ISA. All rights reserved. ANSI/ISA77.14.01-2010 16 4.4.6. Isochronous control mode Isochronous control is an optional
47、 function but subject to the following when provided: Isochronous control shall be used when the generator breaker is closed, and the unit is independent of the grid. Isochronous control shall be a proportional-plus-integral type of control that maintains turbine speed at the setpoint. In this situa
48、tion, the operator shall not be able to select any load-control mode. When the unit is tied to the grid, isochronous control is not allowed, and speed droop shall be utilized as described in Section 4.4.9. 4.4.7. Open-loop load control The transition from speed control to open-loop load control shal
49、l be automatic at the time the generator breaker closes. This is the prevailing control mode while the generator breaker is closed unless a closed-loop control mode is in service. Load reference shall be implemented with no closed-loop control feedback signals and shall include an operator adjustable setpoint expressed in percent or megawatts. The operator adjustable setpoint shall equate to turbine flow demand. The turbine control system shall provide the capability of ramping the open-loop load control setpoint at a minimum of three operator selectable
