IEEE 3006-2012 pdf download Historical Reliability Data for IEEE 3006 Standards: Power Systems Reliability
Equations (6)(9) were used to develop Fig. 1. These curvesavoid the need of looking up x’p,n. Here Az and Ay areplotted in terms of percent deviation from 入 as a function ofthe observed number of failures.
The best estimnate for the average outage duration or repairtime for a particular type of equipment is simply the averageof the observed outage durations. Confidence limit expressionsfor average outage durations are also available if the distribu-tional nature of outage durations is known [17]. However,such expressions are not given here primarily because theaverage outage durations given in this paper are intended as arough guide only. Equipment outage durations are believed tobe more a function of the nature of a power systemn’s operatorthan an inherent function of the equipment itself. Henceaverage outage durations for equipment used in reliabilitystudics should be values believed most reasonable for theparticular system being studied.The data from the survey contained information on thefailure and repair characteristics of 217 categories of equipment. However, the number of observed failures for manyequipment categories was too smal] to allow adequately accu.rate estimiates of failure rates to be made. The Reliability Subcommittee felt that a minimur of eight to ten observed failureswas required for“good” accuracy when estimating equipmentfailure rates (sec Fig. 1). Therefore, whenever possible andreasonable fromn an engineering point of view, equipment cate-gories having less than ten observed failures were combinedwith other categories so as to bring the number of observedfailures in the combined category up to a minirnum of ten. Insome cases an equipment category with a large number of observed failures was further subdivided.In most cases thecquipment size attribute was climinated by corbining categories that were identical except for equipment size. Thessteps reduced the original 217 equipment categories to the 74categories published in this paper. A total of 66 equipmentcategories have eight or more observed failures each; the otheieight categories have between four and seven observed failureseach.
SurvEY ResuLTS OF EQUIPMENT FAILURESTable 2 gves a summary of the “All Industry” equipmnentfailure rate and equipment outage duration data for the 66equiprnent categories that contain eight or more failures. The“actual hours downtimne per failure” is based upon the actualoutage data of the failed equipment: the “industry averageuses all equiprnent failures, and the “median plant averageuses all plants that reported actual outage tirme data on equipment failures.
The 1962 survey !11] contained equipment outage durationdata on failures that have been challenged for two reasons.1) Repairing a failed comnponent may take much longer thanreplacing with a spare (for example, a large power transformner)2) The urgency for repair is a significant factor in the outagttime (low priority repairs may take days or weeks).
In order to help correct these deficiencies, two additionalcolumns on ““repair”” and “replace with spare” were includedin the survey and contain average estimated clock hours to fixfailure duringa 24hour work day,These estimates are averagedover all the plants participating in the survey, even where therewere no actual failures. These results are reported in Table 2and are not included in the more detailed Tables 3-19.Tables 3-19 give more detailed data on equipmnent failurcrate and actua! hours of equiprent downtimne per failure for74 equiprnent categories; this includes the 66 equipment categorjes in Table 2 plus the eight equipment categories containingfrom four to seven failures, The additional detail includes
1) sample size in unit years;
2) number of failures;
3) number of plants reporting data;
4) additional data on actual hours of downtime per failure;5) data for various industry groups where there were ten ormore failures in that industry.
The data on average estimated clock hours to fix failurcduring 24-hour work day have been omitted from Tables 3-19The reliability data in Tables 14,16,and 18 on cables, jointsand termninations represent a different look at the sarme datathat are contained in Tables 13, 15, and 17. One set of tableslooks at the type of insulation and the other set of tables looksat the application of the cable.