Setting Alarm for Power Plant

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A N SI / I EEE Std 676-1986

IEEE Guide for Alarm Monitoring andReporting Systems for Fossil-FueledPower Generating Stations

Published by The Institute of Electrical and Electronics Engineers, Inc. 345 East 47th Street, New York, NY 10017, USAJuly l8, 986 SH10603

Authorized licensed use limited to: Thammasat University. Downloaded on February 23, 2009 at 05:31 from IEEE Xplore. Restrictions apply.


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ANSI/ IEEEStd 676-1986

A n American National StandardIEEE Guide for Alarm Monitoring andReporting Systems for Fossil-FueledPower Generating Stations

SponsorIEEE Power Generation Committee of theIEEE Power Engineering Society

Approved September 19, 1985IEEE Standards Board

Approved February 28, 1986American National Standards Institute

@ Copyright 1986 by

The Institute of Electrical and Electronics Engineers, Inc345 East 47th Street, New York, NY 10017, USAN o p a r t of this publication may be reproduced in any form,in a n e lectronic re tr ieval system or otherwise,wi tho ut the p r io r wr i t t en p ermiss io n of the publisher.



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IEEE Standards documents are developed within the Technical Com-mittees of the IEEE Societies and the Standards Coordinating Committeesof the IEEE Standards Board. Members of the committees serve volun-tarily and without compensation. They are not necessarily members of theInstitute. The standards developed within IEEE represent a consensus ofthe broad expertise on the subject within the Institute as well as thoseactivities outside of IEEE which have expressed an interest in participatingin the development of the standard.Use of an IEEE Standard is wholly voluntary. The existence of an IEEEStandard does not imply that there are no other ways to produce, test,measure, purchase, market, or provide other goods and services relatedto the scope of the IEEE Standard. Furthermore, the viewpoint expresseda t the time a standard is approved and issued is subject to change broughtabout through developments in the state of the art and comments receivedfrom users of the standard. Every IEEE Standard is subjected to reviewat least once every five years for revision or reaffirmation. When a doc-ument is more than five years old, and has not been reaffirmed, it isreasonable to conclude tha t its contents, although still of some value, donot wholly reflect the present sta te of the art. Users are cautioned tocheck to determine that they have the latest edition of any IEEE Standard.

Comments for revision of IEEE Standards a re welcome from any in-terested party, regardless of membership affiliation with IEEE. Sugges-tions for changes in documents should be in the form of a proposed changeof text, together with appropriate supporting comments.

Interpretations: Occasionally questions may arise regarding the mean-ing of portions of standards as they relate to specific applications. Whenthe need for interpretations is brought to the attention of IEEE, theInstitute will initiate action to prepare appropriate responses. Since IEEEStandards represent a consensus of all concerned interests, i t is importantto ensure that any interpretation has also received the concurrence of abalance of interests. For this reason IEEE and the members of its technicalcommittees are not able to provide an instan t response to interpretationrequests except in those cases where the matter has previously receivedformal consideration.

Comments on standards and requests for interpretations should be ad-dressed to: Secretary, IEEE Standards Board345 East 47th Street

New York, NY 10017USA



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Foreword(This Foreword is not a part of ANSIIIEEE Std 676-1986,IEEE Guide for Alarm Monitoring and Reporting Systems forAt the Winter General Power Meeting of IEEE in 1976, the Power Plan t Control, Protection and

Automation Subcommittee proposed tha t a working group be established to review and analyze theala rm monitoring and reporting systems tha t should be used in modern fossil-fueled power generatingstations . It was recognized th at due to the complexity of modern plants, conventional methods (thatis, hardwired window annunciators) were no longer sufficient alone to convey needed information tothe operator. An excessive number of window annunciators would be required to properly monitorplant conditions. The application of alarm monitoring and reporting systems necessitates earlyconsideration of th e design of the a larm and monitoring system to consider information categorizationand the implementation of supplementary reporting techniques. All of these efforts are directedtoward presenting information to the operator in an orderly, manageable form.

This document provides guidelines for categorizing information on plant conditions and means forpresenting this information to the operator.This guide was prepared by the Alarm Monitoring and Reporting Systems Working Group of thePower Plan t Control, Protection and Automation Subcommittee, Power Generation Committee. Themembership of th e working group during the preparation of this guide was:

Fossil-Fueled Power Generating Stations.)

L. BaggaleyD. L. BradleyC. H. ClarridgeD. J. Damsker

H. M. Jimenez, ChairmanK. D. FloydC. E. KneeburgG. L. LuriN . PetroroN. R. PillaiR. J. ReimanD. E. SpacklerW. J. Spengel

Suggestions for improvements of this guide will be welcome. They should be sent toSecretaryIEEE Standards BoardInstitute of Electrical and Electronics Engineers, Inc345 East 47th StreetNew York, New York 10017The following persons were on the balloting committee th at approved th is document for submission

to the IEEE Standards Board:W. W. AvrilM. S. BaldwinJ. H. BellackI. B. BerezowskyG. BermanF. L. BrennanP. G. BrownR. W. CantrellH. E. Church, J rR. S. ColemanR. E. CottaM. L. CrenshawP. M. DavidsonA. C. Dolbec

G. R. EngmannW. M. FennerA. H. FerberD. I. GordenR. D. HandelF. W. KeayP. R. LandrieuG. L. LuriJ. T. Madill0. S. MazzoniM. W. MigliaroJ. L. MillsW. S. Morgan

J. T. NikolasM. I. OlkenR. E. PennJ . D. PlaxcoR. J. ReimanD. E. RobertsM. N. SprouseA. J. SpurginG. I. StillmanJ. E. Stoner, JrJ. B. SullivanS. TjepkemaC. . WylieT. D. Younkins



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ContentsSECTION PAGE1

2.3.4.

5.

6.

7.

8

9

10

1112

Scope and Purpose ....................................................................................1.1 Scope ............................................................................................1.2 Purpose .........................................................................................Definitions..............................................................................................References ..............................................................................................Purpose and Function of Alarm Monitoring and Reporting Systems ...........................4.1 Purpose ..........................................................................................4.2 Function ........................................................................................Categorization and Prior itization of Alarms .......................................................5.1 Purpose .........................................................................................5.2 Benefits .........................................................................................5.3 Procedure .......................................................................................Display Devices ........................................................................................6.1 Window Annunciator Displays ...............................................................6.2 CRT Displays ...................................................................................6.3 Mimic Displays .................................................................................6.4 Printed Displays ...............................................................................6.5 Audible Devices ................................................................................Methods of Prioritization.............................................................................7.1 Window Annunciator Displays ...............................................................7.2 CRT Displays ...................................................................................Sequence of Events Information.....................................................................8.1 Purpose .........................................................................................8.2 Characteristics .................................................................................8.3 Application .....................................................................................8.4 Devices ..........................................................................................Plant Computers ......................................................................................9.1 General..........................................................................................9.2 Application Characteristics...................................................................Window Annunciator, Dedicated SER and Recording System (Pl ant Computer)Integration .............................................................................................Human Factors Engineering.........................................................................Bibliography ...........................................................................................

77777778888899

101111111212121212121313131313141414

TABLESTable 1 Alarm and Information Categorization and Prioritization ................................. 9

Technique ........................................................................................ 11Classification of Display Devices by Atten tion-Getting Value .............................

Table 2Table 3

Correlation Between Alarm a nd Information Category an d Suggested Display12



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APPENDIXES PAGEAppendix A Examples of Alarms for Categories A.1. A.2. and A.3 .................................. 15Appendix B Example of a Multiple-Input Window Configuration ................................... 17Appendix C Sharing of Field Contacts .................................................................. 18Appendix D An Example of Ground Fault Sectionalization Procedure Applicable to Integrated

Systems ...................................................................................... 19APPENDIX FIGUREFig D1 Conventional Sectionalizing ................................................................... 19



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A n American N ational StandardIEEE Guide for Alarm Monitoring andReporting Systems for Fossil-FueledPower Generating Stations

1. Scope and Purpose1.1 Scope. This guide provides guidelines forthe organization' of fossil-fueled power generat-ing plant alarm and monitoring informationinto types and categories, taking into consider-ation information usefulness and limitations.This guide further serves to establish guide-lines for correlating type and category of al armand monitoring information with the appropri-at e information-display devices.

Adherence to the categorization and the cor-responding information-display techniques pre-sents prioritized ala rm and monitoringinformation to the operator which is appropri-ately proportioned between the window annun-ciator, CRT, mimic display, and printer. Thisalso permits a reduction in the number of win-dow annunciators over historic practices.1.2 Purpose. It is the purpose of thi s guide todefine the logical classifications for categoriesof plant information and to identify display tech-niques available for monitoring and reportingthis information to plant personnel. Use of thisguide will:

(1)Aid engineers in achieving a balanced andintegrated design in al arm monitoring systems(2) Assist control-room operator, supervisory,and training personnel

(3) Improve proficiency of control room op-erators

(4) Enhance plant generating station safety,efficiency, and availability

2. DefinitionsDefinitions of terms used are as described in

ANSI / IEEE Std 100-1984 [l].' Where no appro-priate term exists, it is defined here.

Numbers in brackets correspond to those of the refer-ences in Section 3 of this standard.

integrated alarm system. An alarm displaysystem consisting of window annunciators com-bined with CRT, printer, or mimic display.predictive alarming. A method of aler ting theoperator to a potential problem in time for himto respond and initiate corrective action to mit-igate the problem.warble-tonegenerator.An audio-frequency os-cillator, the frequency of which is varied cycli-cally at a subaudio rate over a fixed range.window annunciator. A visual signal deviceconsisting of a number of backlighted windows,each one indicating a condition that exists orhas existed in a monitored circuit, and beingidentified accordingly.

3. References[l] ANSI / IEEE Std 100-1984. IEEE S tandardDictionary of Electrical and Electronic Terms.2[2] Illuminating Engineering Society of NorthAmerica, IES Lighting Handbook, 1981 Appli-cation Volume IES Lighting Handbook, Refer-ence Volume, 198L3

4. Purpose and Function of AlarmMonitoring and Reporting Systems

4.1 Purpose. The purpose of ala rm monitoringand reporting systems is to:

4.1.1 Alert, identify, and locate for personnel,events, actual or imminent, of varying impor-tance and necessitating different response times,from immediate to delayed, to permit continuedsafe plant operation.

'ANSI documents are available from the Sales Depart-ment, American National Standards Institute, 1430 Broad-way, New York, NY 10018.' ES publications are available from the Illuminating En-gineering Society, 345 East 47th Street, New York, NY10017.

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ANSI / IEEES M 676-1986 IEEE GUIDE FOR ALARM MONITORING AND REPORTING SYSTEMS4.1.2 Reduce or minimize er rors by personnel,

thereby, improving plant safety, efficiency, andavailability.4.1.3 Provide comprehensive data for reviewand analysis as an a id in defining problems andimplementing corrective action.4.1.4 Provide a permanent document for his-torical records.4.1.5 Provide a timely indication of conditionsrequiring maintenance.4.2 Function. In order to serve a variety of di-verse needs, the system should function to mon-itor and report:4.2.1 Conditions tha t may result in danger toplant personnel.4.2.2 Pretrip conditions that if uncorrectedmay lead to a unit tr ip or to damage to the unit.4.2.3 Conditions that may cause a unit trip,significant reduction in load, or an alternatemode of plant operation.

4.2.4 Information necessary for protection ofequipment that represents significant invest-ment, lengthy replacement time, or specializedmaintenance requirements.4.2.5 Conditions requiring equipment repairbefore resta rt is possible.4.2.6 Sufficient pretrip and post-trip infor-mation to provide aid in problem definition.4.2.7 Sufficient information to achieve de-sired level of unit operation.4.2.8 Information that has been time syn-chronized with all related plant monitoring andreporting systems.4.2.9 Data on all of the above for historicalrecords.

5. Categorization and Prioritization ofAlarms5.1 Purpose. In the application of alarm mon-itoring and reporting systems in power gener-ating stations, early effort should be directed tocategorizing alarms and related monitoring in-formation. The fundamental purpose of thecategorization is to assist the control-room o perator in the performance of his duties. Alarm,information categorization, and prioritizationalso serve as aids in selecting appropriate typesof display devices for the various categories. Theselection of the appropriate display device is ad-dressed in a subsequent section of this applica-tion guide.

5.2 Benefits.Categorization of ala rms and mon-itoring information resul ts in two principal ben-efits, that is:

(1)Establishes the relative importance ofalarms and monitoring information within thecontrol room

(2) Predete rmines t he priority of operatorsresponse to various alarm and information in-puts

5.3 Procedure. The fundamental step in cate-gorizing alarms is to group alarms and moni-toring information according to the operator-response criteria. This categorization processprovides alarm and information prioritizationand is shown in Table 1.

The categorization of total alarms should re-sult in between 5% and 15% of the alarms inthe A-1 category, 20% an d 30% in A-2, and t heremaining in the A-3 category.

Description of alarms in each category:(1) Alarms that indicate tha t a boiler, turbine ,

or generator tri p has occurred, or will occur fol-lowing a very short time delay unless the op-erator responds immediately.(2) Alarms indicating a fire protection systemactuation.

(3) Alarms indicating imminent or actualdamage to major plant equipment.(4) Alarms th at indicate failu re of majorequipment to transfer to the planned mode, fol-lowing a plant upset.

A-1

A-2(1)Alarms indicating a major piece of equip-ment has been taken out of service automati-

cally.(2) Alarms indicating a loss of minor equip

ment.(3) Alarms th at indicate failure to meet reg-

ulatory requirements.(4) Alarms that indicate failure of equipmentneeded to support power operation.A-3

(1)Alarms indicating impending damage tominor plant equipment if operator action is nottaken.

(2) Alarms indicating loss of redundant powerto important plant equipment.(3) Alarms tha t indicate impending failure tomeet regulatory requirements.(4) Alarms that indicate impending loss ofequipment needed to support power operation.

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FOR FOSSILFUELED POWER GENERATING STATIONSANSI / IEEES M 676-1986

Table 1Alarm and Information Categorization and PrioritizationALARM

Priority Significanceategory 5 p eA-1 Critical Highest Immediate operator action required to prevent or mitigatesignificant damage to equipment or property or to avertconditions leading to imminent loss of load.A-2 Urgent Second highest Unusual or serious operational or maintenance situationrequiring prompt operators action.A-3 Operational Third highest Operational or maintenance situation requiring operatorsattention.

Information Categorystatus

Sequence of events informationInformation not normally requiring corrective action.Information requiring time correlation with other infor-mation for fault and problem analysis. It may supple-ment any of the categories listed above.

(5 ) Alarms that indicate a loss of plant com-munications.

Refer to Appendix A for specific examples ofalarms for each category.It should be noted that the category of thealarm depends upon the plant mode and thesta te of the process being monitored, and tha t achange in situation may alter the significanceor priority of the alarm. An alarm, which maybe highly significant during failure of a subsys-tem or process within a subsystem, is meaning-less when that alarm results from a systemfailure. For example, a low-fluid pressure al armis meaningless to the operato r if the pump whichproduces the pressure is out of service. Underthese conditions, this l atte r al arm can be inter-preted as status indication. A parallel situationexists when considering the plant operatingmode. Under a given operating mode, that is,start-up, an alarm may be highly significant,whereas under a different operating mode, thatis, tripout, the a larm is relegated to a status orinformation category. These situation-depen-dent and mode-dependent conditions exist andmust be handled and recognized by plant oper-ating personnel. Alarm suppression or recate-gorization should be designed into the system toautomatically suppress or recategorize thesealarms where possible.

6. Display DevicesThe basic purpose of a display is to provide an

effective means of presenting alarm and moni-toring information to the operator. The specific

display techniques utilized should be consistentwith th e response required. Certain informationshould be presented in a timely and unique man-ner to enable the operator to recognize the kindof problem and to respond appropriately. O therinformation may be presented in a form thatrequires further interpretation or analysis.Some monitoring information needs to be doc-umented for permanent records or later analy-sis. By varying the type of display utilized, thedesigner can effectively establish a correlationbetween the categorization of alarm and moni-toring information and the method of presen-tation. The specific display devices addressed inthis document include:

(1)Window annunciator displays(2) CRT displays(3) Mimic displays(4) Printed displays

6.1 Window Annunciator Displays. This typeof display provides high visibility in a consistentmanner, is always available without th e need tocall up the display, and is always in the sameplace for each unique alarm. Because of theseattributes, it is suggested that window annun-ciator displays always be utilized for critical andurgent alarms. It is further suggested that thenumber of window annunciators be limited tothose necessary to continue restricted unit o peration when the equipment supporting addi-tional alarm reporting is unavailable. Windowannuncia tor displays should incorporate the fol-lowing characteristics:6.1.1 Display Arrangement. Window an-nunciators should be located above their asso-

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ANSI / IEEEStd 676-1986

COOLING WATERHEADER PRESSURELOW

IEEE GUIDE FOR ALARM MONITORING AND REPORTING SYSTEMS

Process componentProcess variableProcess condition

ciated displays and controls and grouped byspecific systems. By arranging the annunciatordisplay so tha t i t correlates with its associateddisplays and controls, the operator can morequickly and accurately compare the displays,and then respond to the alarm condition.

6.1.2 Display Illumination.Good practice inwindow annunciator lighting requires adequatevisual distinction between normal and alarmdisplays under all ambient lighting conditions.Sufficient visual distinction is needed to com-mand the operators attention. Windows shouldonly appear to be in ala rm when energized, andnot from the effects of direct or reflected light.Flashing capability or other means of attractingattention may be used, such as changing color.Maximum luminance ratios should be as rec-ommended by [2].6.1.3 Display Legends. Nameplate legendsshould reflect consistency in type, style, and sizefor easy reading by control-room operators. Win-dow characters should be printed in capitals.Abbreviations should be consistent throughoutthe control room and whenever possible,throughout all alarm reporting devices. A sug-gested format for presenting window legends isshown below.

S/ U TRANSFORMERWINDING TEMPHIGH

EquipmentVariableCondition

To ensure legibility at the intended viewingdistance, consideration should be given to thefollowing window legend display parameters .

(1)Character height(2) Letter and number width(3) Stroke width(4) Character, word, and line spacing6.1.4 Return to Normal. When an alarm

clears, it should be indicated in a distinctivemanner in the window. This should be followedby a resetting of the window alarm to normal.

6.1.5 Nameplate Replacement. Meansshould be provided to assure nameplate replace-ment in the correct location after window re-lamping.

6.1.6 Multiple-Input Windows. Multiple-in-put windows are not for critical alarms. Urgent

or operational alarms may be incorporated inmultiple-input windows; however, care shouldbe exercised when doing so to ensure that theoperator will have sufficient information avail-able in other forms to determine the specificnature of the alarm. An example of this and howmultiple-input ala rms may be utilized to reducethe number of window displays required is con-tained in Appendix B.

6.1.7 Multiple-Input Window Realarming.Multiple-input windows should realarm for sub-sequent alarm inputs and should not return toa normal condition until all al arm inputs to thewindow have returned to normal.

6.1.8 Nonambiguous Nomenclature. Win-dow alarms should not present multiple choiceindications, such as HIGHILOW or LEVEL/PRESSURE, for critical and urgent alarms.

6.1.9 Annunciator-Control Functions. An-nunciator-control functions should be providedfor audible silence, window acknowledge, win-dow reset, and system test. Good practice in-cludes multiple-pushbutton locations forparallel operation of the audible-silence functionwith dedicated locations for acknowledge, reset,and test functions.

6.1.10 Special Considerations. I t is sug-gested tha t unique size, shape, and color be uti-lized to differentiate control pushbuttons. It isfurther suggested that the tes t pushbutton be ofa design that provides restricted access to pre-vent inadvertent operation during a crisis orstress situation.6.2 CRT Displays. CRTs inherently have theability to display a large quanti ty of informationin a relatively small area. CRT displays are eas-ily changed or expanded to include new infor-mation since they are normally computer ormicroprocessor controlled. The CRTs driven bya computer system can provide alarm monitor-ing and reporting by themselves, or can also beused as an effective complement to other in-stalled ala rm monitoring and reporting systems.

6.2.1 When a CRT is being utilized as analarm device, the size of the screen, characterheight, and number of lines of informationshould be a function of the viewing distance.When the capacity of the display has been ex-ceeded, additional pages of alarms should bestored in memory. The number of pages of mem-ory specified should be determined by the num-ber of anticipated alarms during a worst-casecondition.

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FOR FOSSILFUELED POWER GENERATING STATIONS6.2.2 A common display format is one where

new alarms appear at the top of the screen andexisting alarms are moved down. When thescreen is filled, the bottom line moves in memoryand so on. (Other display formats may be uti-lized.) Convenient operator controls should beprovided to allow an operator to recall any pageto the screen for review. When a new alarmappears, most systems return to page one dis-playing the new alarm. If it is desirable to reta inthe page when a new alarm appears, a freezeoption should be considered where the displayis locked in until released by the operator.6.2.3 To enhance the attention getting capa-bilities of CRT displays, flash rates, and colorscan be effectively utilized. Flashing all or a por-tion of a message can call attention to a newalarm. Color coding should be consistent withother types of ala rm displays.6.2.4 Return to normal alarm messages mayappear as a new message at the top of the screenor be presented as a color change or deletion ofth e existing message. All messages should moveup and fill vacant lines when any messages aredeleted.6.2.5 Alarm messages typically include thepoint or input address, date, and time infor-mation, type of alarm, and a programmable leg-end field for point description or operatorinstruction.

6.3 Mimic Displays.A mimic display consistsof process flow diagrams containing alarm in-dications, equipment s tatus indications, and con-trols. A primary att ribute of mimics is that theyassist in rapid interpreta tion of the informationin the context of the total system.

ANSI / IEEEStd 67619866.4 Printed Displays. Printers with a wide va-riety of styles and speeds ar e available. Printersused for logging information can vary from atype which displays only numeric and logs onlyan alarm identification and time of occurrence,to alphanumeric which prints words describingthe details in addition to the numeric identifi-cation. Degree of sophistication and speed of theprintout depends upon the application for bothmessage format desired and printout speedneeded. The main function of printers is to re-cord all categories of ala rms for future analysisand permanent records. Printers do not conveyinformation to all personnel in the control roomas readily as other available display devices.6.5 Audible Devices. Audible devices are usedin conjunction with display systems to attractthe operators attention and to communicate thedegree of urgency. Audible devices have a high-recognition factor and provide a multilocationalaler t. Good practice in audible device applicationrequires the following:6.5.1 Audible devices should be audible in a ll

parts of the control room without being irritat-ing or excessively loud (90 dB maximum), andat least 10 dB above background noise.6.5.2 Audible alarms should be positioned togive directional at tention to the specific display,such as boiler vs generator.6.5.3 In some applications it may be desirableto differentiate audible devices by alarm cate-gory. (See Appendix A.)6.5.4 It is advisable to employ a unique au-dible for ala rm clearing conditions.

(See Table 2for suggested display techniquesand Table 3 for attention-getting value of var-ious devices.)

Table 2Correlation Between Alarm and Information Categoryand Suggested Display TechniqueDisplay Technique

Alarm Annunciator MimicCategory Window CRTs Display Pr in terA-1 Critical Primary Secondary Secondary SecondaryA-2 Urgent Primary Secondary Secondary SecondaryA-3 Operational Secondary Primary Secondary SecondaryInformation CategorySequence of events - Secondary - PrimaryStatus indication - Primary - Secondary* Sequence of events information avail able from dedicated SER or computer. Refer to Section 8.Secondary-use to be evaluated on a case-by-case basis.

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ANSI / IEEEStd 676-1986 IEEE GUIDE FOR ALARM MONITORING AND REPORTING SYSTEMSTable 3Classification of Display Devices by Attention-Getting Value

Mode Attention-GettingRelativeresentation

Device Visual Auditory ValueWindow annunciator X X HighCRT displays X X Low to moderateMimic displays X ModeratePrinted displays X X Low to moderateNOTE Auditory presentation is based upon the use of a bell, buzzer, chime, gong,horn or warble-tone in conjunction with the visual presentation. The use of auditorywith visual can enhance the overall attention-getting value to very high to moderate.

7. Methods of Prioritization7.1 Window Annunicator Displays. The areaof first consideration in prioritization is windowannunica tor displays. Without a disciplined anda balanced approach to the use of annunciatordisplays, this highest priority tool loses its se-lectivity, becomes a nuisance to the operatorduring transient plant upsets, and contributesto stress in a major crisis. Prioritization methodsinclude unique window positioning, hierarchicalwindow positioning, and unique window iden-tification.7.1.1 Unique Window Positioning. An ex-ample of this type of prioritization would be todedicate the top row of each window cabinet ascritical alarms. Another example might be adedicated window cabinet which would containcritical ala rms only. The principal disadvantageof this method of alarm prioritization is that itmay conflict with th e human factors concern ofgrouping displays with controls or violate alar minput functional grouping.7.1.2 Hierarchical Window Positioning.This method is consistent with accepted humanfactors engineering criteria. The principal dis-advantage is tha t a larms can not be previouslycorrelated with their controls, or tha t the alarmsmay compete for space with other display de-vices and equipment.7.1.3 Unique Window Identification. Colorcoded windows would appear to provide the op-timum type of alarm prioritization without con-flicting with human factors considerations. Acolor prioritzation method could consist of crit-ical alarm displays coded red, urgent a larm dis-plays coded amber, and operational alarmdisplay coded white. Whatever color prioritiza-tion method is selected, it should be uniformthroughout the control room display devices.

7.2 CRT Displays. The area of second consid-eration in prioritization is CRT displays. Sug-gested methods are:7.2.1 Dedicating CRTs for only ala rm presen-tation.7.2.2 Locating CRTs in a unique place withinthe control room. The location should considerproximity to associated controls.7.2.3 Using foreground or background colorsin the CRT display. Care should be taken inselecting colors to be compatible with other con-trol room displays.7.2.4 Dedicating unique areas of the displayscreen to different priority levels.

8. Sequence of Events Information8.1 Purpose. Because of the increasing com-plexity in plant design, a means to provide highspeed monitoring has become a necessity inpower plants to track, display, and record cas-cading events preceding and following a plantor equipment upset.8.2 Characteristics8.2.1 Sequence of events should be recordedin real time with approximately 1ms resolutionbetween events.8.2.2 The time of each input status changeshould be provided, along with identification ofstatus change, that is, abnormal or normal.8.2.3 Identification of input number and al-phanumeric description of event in easily under-stood language.8.2.4 The ability to correlate messages withother alarm display devices.8.2.5 Sequence of events information shouldbe reported on a prin ter, CRT display or both.8.2.6 Consideration should be given to the

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FOR FOSSILFUELED POWER GENERATING STATIONS ANSI / IEEESt d 676-1986need for synchronizing sequence of events in-formation to a master time source for correlationwith other plant functions.8.2.7 No information should be lost during themost severe plant upset condition.8.3 Application.Information that provides thesequence of those events, detected in their orderof occurrence in real time, is used for operation,engineering, and plant management purposes.Sequence of events information is used by thesegroups in the following manner:8.3.1 Operations. For immediate detection,interpretation, and understanding of changingplant conditions to permit timely remedial ac-tion.Assists in operational tests and startup ofplant equipment.The data also permits analysis of operatingprocedures.

8.3.2 Engineering. For fault analysis and tocollect data for future engineering and designreferences.8.3.3 Plant Management. For use in plan-ning outages and maintenance of equipment.For validating proper operation of systems asoriginally designed.

8.4 Devices8.4.1 Dedicated Sequential Events Re-corder.Modern sequential events recorders aremicroprocessor-based machines accepting digi-tal inputs or inputs that may be digitized, pro-viding continuous surveillance of these inputsand recording status changes in accordance withguidelines outlined above. SERs are designedonly for monitoring and recording events. SERsmay be interfaced with computers, CRT dis-plays, and other data links. SERs are usuallyequipped with nonvolatile memories to preventloss of information on power failure. SERs maybe equipped to provide printouts of input re-views, alarm summaries, and similar data. Avariety of hardware and software features areavailable to enhance the versatility of SERs.8.4.2 Plant Computer. The plant computermay be used as a source of sequential eventsinformation. This may be accomplished by ded-icating a portion of the computer system to afast-scan operation or interrupt-response oper-ation, with nonsequence of events on a slowerscan operation for status determination. Se-quence of events information from the plant

computer adheres to the guidelines outlinedabove.8.4.3 Application Characteristics.Both thededicated SER and the plant computer whenutilized as an SER are characterized by the fol-lowing:8.4.3.1 Provide redundancy by operating inparallel with inputs to the window annunciatorand displaying information on an associatedCRT.8.4.3.2 Indicate specific inputs involved onmultiple inputs to a common window from awindow annunciator, that is, typically, opera-tional alarms can be indicated on the CRT or bya hard copy on a printer, or both.8.4.3.3 Return to normal conditions may bedisplayed on the CRT, or recorded by hard copyon a printer, or both.8.4.3.4 Hard-copy data records of alarms asthey occur can be provided as well as storedsummary or historical records, or as logs forlater evaluation.8.4.3.5 Alarm suppression can be activated,based on plant conditions and related inputs.8.4.3.6 Data and logs can be provided onsequence of events, plant trips, or other event-triggered occurrences.8.4.3.7 Provide for long term storage ofalarm and event data on disc or magnetic tapefor later retrieval and analysis.

9. Plant Computers9.1 General. The inherent ability of computersto manipulate data offers a more flexible andversatile means of presenting information to theplant operator than is possible in a typical win-dow annunciator display.9.2 Application Characteristics. In additionto the application characteristics listed under8.4.3, lant computers offer the following ca-pabilities for alarm system functions:9.2.1 Continual rewarning of increased criti-cality can be displayed on a CRT or by hard copyon a printer, or both, when an input conditioncontinues to move further from the initial alarmsetting.9.2.2 Predictive alarms may be displayed onthe CRT, or by hard copy on a printer or both.One method of predictive alarming is by ananalysis developed by measuring the rate ofchange of process parameters and calculating

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ANSI / IEEEStd 676-1986 IEEE GUIDE FOR ALARM MONITORING AND REPORTING SYSTEMSthe trend to determine the future time when themeasured value will exceed the al arm set point.9.2.3 Specific measurement data can be pro-vided at the time of alarm and on a continuingbasis, while in alarm.9.2.4 Alarm suppression can be activated,based on plant conditions, related inputs andcalculations.9.2.5 Pretrip and post-trip trends of analogvalues and contact inpu ts for major plant equip-ment and systems can be logged for futur e anal-ysis.9.2.6 Long term storage of alarm, event, andother plant data can be provided on disc or mag-netic tape for later re trieval and analysis.9.2.7 Process and instrument diagrams, bardiagrams, and plant subsystem pictorials can bepresented on CRT or by hard copy on printer,or both.9.2.8 Computer enhancement of operator per-formance can be used to help the operator followand understand the significance of plant alarmconditions as they occur. Some techniques are:

(1) Group trending displays(2) Operator guide messages(3) Graphic one line and pictorial displays of

plant subsystems

10. Window Annunciator, DedicatedSER and Recording System (PlantComputer) Integration

In modern power plants, the computer systemand the window annunciator system a re used tosupplement each other. In those applicationswhere a dedicated SER is used, it should sup-plement the window annuncia tors and the plantcomputer. A method of implementing the inte-gration of window annunciators with e ither theplant computer or the SER is described in A ppendix C.

11. Human Factors EngineeringEarly and appropriate consideration to hu-

man factors engineering is mandatory by de-signers of alarm monitoring and reporting

systems. Previous mention has been made in th isdocument of the desi rability for correla ting dis-play devices with re lated displays and controls.Consideration should be given to the operator'stask and his ability to absorb and comprehendthe alarm information displayed, and of limi-tations on the quantities of such displays. A hu-man factors goal is achieved in a system wherethe a larm s communicate the kind of trouble andthe degree of urgency, without overloading thehuman capacity or causing unusual stress. Asan alarm is displayed in the control room, theoperator may be sitting or standing, or facingin any direction; thus, th e location of al arm dis-play devices are conditioned by this fact. Am-bient illumination and sound level may be at anacceptable, marginal or degraded level. Thus,the display devices and audible devices are de-signed to provide acceptable performance undervarying conditions. Alarm signal level againstbackground is to be sufficient to command theoperator's attention without irritation. Ade-quate visual contrast should be provided to per-mit immediate operator recognition of thedisplay indication. The seated operator, facingforward, has a narrow cone of sharpest vision of15 to 20 ".The operator's peripheral vision en-compasses close to 180 '. Visual alarms, controlsand displays should be optimally located follow-ing task analysis.

12. Bibliography

HARRIS, C. M. Handbook of Noise Control. NewYork: McGraw Hill, 2nd ed, 1979.I.S.A. S.18.1-1979, Annunciator Sequences andSpecifications.McCORMICK, E. J. Human Factors in Engi-neering and Design. New York: McGraw Hill,1976.VAN COTT and KINKADE. Human Engineer-ing Guide to Equipment Design. Washington,D.C., US Govt Printing Office, 1972.

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FOR FOSSILFUELED POWER GENERATING STATIONSANSI/ IEEESM 6761986

Appendixes(These Appendixes are not a part of ANSI / IEEE Std 6761986,EEE Guide for Alarm Monitoring and Reporting Systemsfor Fossil-Fueled Power Generating Stations.)

Appendix AExamples of Alarms for Categories A-1, A-2, and A-3

NOTE Categories can change depending on plant specifics; see Table 1.

Al. A-1 CategoryAl.l The following examples are pretrip or tripalarms.

(1)Master fuel trip(2) Generator differential trip(3) Turbine lube oil pressure low(4) Generator volts / hertz high(5 ) Boiler drum level low

A1.2 The following examples pertain to firealarms.

(1)Pulverizer fire(2) Turbine oil fire(3) Fire pump autostart(4) Deluge valve autotrip

A1.3 The following examples are warnings of acritical problem.

(1)Boiler superheat temperature high(2) Turbine EH governor fluid pressure low(3) Generator winding temperature high(4) Turbine eccentricity high

A1.4 The following examples cover failure ofmajor equipment needed to transfer to theplanned mode, following a plant upset.

(1)4 kV aux bus, failure to transfer to reserve(2) Diesel engine generator, failure to auto-(3) Emergency seal oil pump motor, failure to(4 ) Turbine turning gear motor, failure to au-

startautostarttostart

A2. A-2 CategoryA2.1 The following examples indicate loss ofmajor equipment.

(1)Trip of an ID, FD, or PA fan motor(2) Trip of a pulverizer motor(3) Trip of a boiler feed pump motor

A2.2 The following examples cover loss of minorequipment.(1)Turbine auxiliary oil pump motor trip (if

plant has dc turbine oil pump motor)(2) Vacuum pump motor trip(3) Station ai r compressor motor t ripA2.3 The following examples perta in to failureto meet regulatory requirements.

(1) Stack opacity high(2) Stack sulfur dioxide emissions high(3 ) Precipitator efficiency lowA2.4 The following examples indicate failure ofequipment needed to suppor t power operations.

(1)Station control battery voltage low(2) Station power battery charger failure(3) UPS power supply (to boiler or turb ine con-trols) transfer to station supply

A3. A-3 Category

A3.1 The following examples indicate impend-ing danger to minor plant equipment.

(1)Service water pump motor bearing tem-perature high(2) Control ai r compressor vibration high(3) Boiler sump overflow

(4) Sootblower air pressure lowA3.2 The following examples cover loss of re-dundant power to important plant equipment.

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ANSI / IEEEStd 676-1986 IEEE GUIDE FOR ALARM MONITORING AND REPORTING SYSTEMS(1)Supply to station UPS ailure(2) Turbine ac oil pump or dc oil pump failure(3) Station control battery failure

impending loss of equipment needed to supportpower operation.(1 ) Isolated phase bus forced cooling unit outof service(2) Cooling tower basin level low

(3) Differential pressure at circulating water3.3 The following ar e examples of alarms forimpending failure to meet regulatory require-ments.to river)

low(l)High pH in basin (Overflow goes A3.5 The following alarms are examples of

those that indicate a loss of plant communica-tions.2) Sulfur dioxide emissions near limit(3 ) Opacity near limit(4) Fly ash pond excessive dusting (1)Telephone battery voltage low(2) Station loud speaker system out of service

(3) Microwave (communications) systemA3.4 The following examples cover alarms for failed

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FOR FOSSILFUELED POWER GENERATING STATIONSANSI / IEEEStd 6781986

Appendix BExample of a Multiple-Input Window Configuration

B1. General CommentsAn example of how various display techniques

may be combined to provide an effective a larmreporting mechanism for the plant operator isindicated below. Note tha t by using a dedicatedmultiple-input window for the major piece ofequipment the operator is informed of a systemdisturbance or pending plant tr ip via a dedicatedwindow display and can ascertain the specificreason for the failure of the major piece of eq ui pment via a CRT or printer. This can be an ef-fective mechanism for reducing the number offixed window displays required without jeopar-dizing alarm categorization, prioritization, andreporting to the plant operator.

B2. ExampleTypical annunciation provided for large FD(1)FD fan motor differential trip(2) FD fan motor instantaneous trip

fans is as follows:

(3) FD fan motor overload trip(4) FD fan motor overheated(5 ) FD fan motor vibration high(6 ) FD fan lube oil pressure low(7) FD fan standby lube oil pump failure

Instead of providing individual window dis-plays for each alarm, all of the above alarmscan be grouped into one or two multiple-inputwindows. If one multiple-input window were uti -lized, it could read FD an failure or trip. If twowindows were used, one could be for FD an tripsand the other forFD an failures. In eithe r case,the specific input th at caused the multiple-inputwindow to go into alarm would be displayed ona CRT or printer. The number of dedicated win-dow displays required is greatly reduced withoutloss of information to the operator. If the CRTor prin ter were out of service, the multiple-inputwindows would still a ler t the operator to a n ab-normal condition and conventional panel in-strumentation could provide information toascertain the problem.

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FOR FOSSILFUELED POWER GENERATING STATIONS ANSI / IEEEStd 676-1986

Appendix DAn Example of Ground Fault Sectionalization ProcedureApplicable to Integrated Systems

When applying visual annunciators, com-puters, SERS, nd other types of alarm moni-toring systems, consideration should be given tothe problem of ground faults on trouble contactinput wiring. Because of the widespread locationof alarm system initiating devices in varyingenvironments, and the resultant convergence ofthe input wiring to the alarm monitoring sys-tem, the probability and hence th e frequency ofground faul ts is greater t han on other plant sys-tems. These grounds represent a problem toplant operating personnel. A single ground ofitself does not cause any alarm system opera-tional anomalies, but it does represent a poten-tial problem should a second ground occur. Inspite of high quality, long life wire, and cableinsulation used in power plants, grounds occurin both new and old plants. Probable causes ofgrounds in new plants include:

(1) Insulation damage during construction(2) Human errors in design or wiring(3) Component failureIn older plants grounds result from:(1)Build-up of contaminants in combination

with moisture(2) Hostile ambient conditions such as heat,vibration, or motion(3) Age deterioration(4) Human errors

Once they occur, grounds may be eliminatedby a combination of detection and a disciplinedmethod of sectionalization permitt ing isolationand identification. In those applications wherethe visual annunciator, computer, or sequentialevents recorder are not electrically intercon-nected, conventional sectionalizing may be used.This usually consists of switches by which, afterground fault detection, trouble contact inputwiring is disconnected in convenient groups, typ-ically 16 or 20 inputs per disconnect switch tolocate the group of inputs in which the ground

exists. After locating the group, individual in-puts may be disconnected until the precise lo-cation of the grounded input is determined.Multiple grounds on alarm monitoring sys-tems involve a somewhat more complicated dis-connecting procedure requiring input groups tobe disconnected and remain disconnected whileindividual groups are reconnected one group ata time, unti l all grounds have been located. Thesectionalizing procedure is further complicatedwhen there is a mixture of grounds on both sidesof the trouble contacts.

In those applications in which the computer,visual annunciator, and possibly the SER areintegrated, a special consideration must be givento the problem of ground fault sectionalization.In the integrated system, a single trouble con-tact may be utilized and both systems wired inparallel from a common trouble contact voltagesource as shown in Fig D1.

Fig D1Conventional Sectionalizing

INITIATINGCONTACTSENSING LEAD COMMON LEAD(SIGNAL) 18,RETURN)

L- DISCONNECTSWITCH

GROUNDDETECTORCONTACTVOLTAGEI SOURCE 1

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ANSI / IEEES M 6761986In order to isolate the inputs to sectionalize,

one of the parallel paths must be eliminated.Most modern generating plant visual-annuncia-tor systems are required to accept random inpu twindow assignments, that is, any input or groupof inputs may be assigned randomly to any win-dow within the system. Thus, it is not possibleto disconnect the visual annunciator on a dis-ciplined basis; that is, 16 inputs per group dueto the random wiring. However, the computerinputs are usually sequential and most alarminputs a re wired to the computer, whereas onlya selected few ar e displayed by annunciator win-dows. Because of these characteristics, the pri-mary means of sectionalizing is through thecomputer. Since the annuncia tor window inputsar e randomly wired, it is necessary to disconnectthese inputs before proceeding with disconnect-ing the computer inputs.

The sectionalizing procedure is to disconnect

one of the parallel paths (window annuncia tors)and then to proceed to sectionalize, in a sequen-tial manner. Disconnection of the window an-nunciators obviously disables their monitoringcapability during the sectionalizing process.While this is not the optimum situation, it rep-resents the least undesirable option. If the win-dow annunciator inputs were not disconnectedbecause of th e parallel wiring paths an d the ran-dom wiring, under certain conditions of a groundor grounds on the input wiring could never beisolated and located.

Special hardware or software might be con-sidered which would prevent tota l loss of sur-veillance and superfluous printout during thesectionalizing procedure when it is necessary toleave sections of the inputs in a disconnectedposition for a protracted period of time, aswouldbe the case when multiple grounds occur on bothsides of the initiating contacts.

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Setting Alarm for Power Plant

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