{"id":111986,"date":"2024-10-18T16:19:33","date_gmt":"2024-10-18T16:19:33","guid":{"rendered":"https:\/\/pdfstandards.shop\/product\/uncategorized\/ieee-c57-91-2012\/"},"modified":"2024-10-24T22:03:18","modified_gmt":"2024-10-24T22:03:18","slug":"ieee-c57-91-2012","status":"publish","type":"product","link":"https:\/\/pdfstandards.shop\/product\/publishers\/ieee\/ieee-c57-91-2012\/","title":{"rendered":"IEEE C57.91 2012"},"content":{"rendered":"

Revision Standard – Active. This guide provides recommendations for loading mineral-oil-immersed transformers and step-voltage regulators with insulation systems rated for a 65 C average winding temperature rise at rated load. This guide applies to transformers manufactured in accordance with IEEE Std C57.12.001 and tested in accordance with IEEE Std C57.12.90, and step-voltage regulators manufactured and tested in accordance with IEEE Std C57.15. Because a substantial population of transformers and step-voltage regulators with insulation systems rated for 55 C average winding temperature rise at rated load are still in service, recommendations that are specific to this equipment are also included.<\/p>\n

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PDF Pages<\/th>\nPDF Title<\/th>\n<\/tr>\n
1<\/td>\nIEEE Std C57.91-2011 Front Cover <\/td>\n<\/tr>\n
3<\/td>\nTitle page <\/td>\n<\/tr>\n
6<\/td>\nNotice to users
Laws and regulations
Copyrights
Updating of IEEE documents
Errata
Interpretations <\/td>\n<\/tr>\n
7<\/td>\nPatents <\/td>\n<\/tr>\n
8<\/td>\nParticipants <\/td>\n<\/tr>\n
10<\/td>\nIntroduction <\/td>\n<\/tr>\n
12<\/td>\nCONTENTS <\/td>\n<\/tr>\n
15<\/td>\nImportant Notice
1. Overview
1.1 Scope
1.2 Purpose <\/td>\n<\/tr>\n
16<\/td>\n2. Normative references
3. Definitions <\/td>\n<\/tr>\n
17<\/td>\n4. Effect of loading beyond nameplate rating
4.1 General
4.2 Voltage and frequency considerations <\/td>\n<\/tr>\n
18<\/td>\n4.3 Supplemental cooling of existing self-cooled transformers
4.4 Information for user calculations <\/td>\n<\/tr>\n
19<\/td>\n5. Transformer insulation life
5.1 General <\/td>\n<\/tr>\n
20<\/td>\n5.2 Aging equations <\/td>\n<\/tr>\n
24<\/td>\n5.3 Percent loss of life <\/td>\n<\/tr>\n
25<\/td>\n6. Ambient temperature and its influence on loading
6.1 General
6.2 Approximating ambient temperature for air-cooled transformers
6.3 Approximating ambient temperature for water-cooled transformers
6.4 Influence of ambient on loading for normal life expectancy <\/td>\n<\/tr>\n
26<\/td>\n7. Calculation of temperatures
7.1 Load cycles
7.1.1 Load cycles, general <\/td>\n<\/tr>\n
27<\/td>\n7.1.2 Method of converting actual to equivalent load cycle
7.1.3 Equivalent peak load
7.1.4 Equivalent continuous prior load <\/td>\n<\/tr>\n
28<\/td>\n7.2 Calculation of temperatures
7.2.1 General
7.2.2 Components of temperature <\/td>\n<\/tr>\n
29<\/td>\n7.2.3 Top-oil rise over ambient <\/td>\n<\/tr>\n
30<\/td>\n7.2.4 Oil time constant <\/td>\n<\/tr>\n
32<\/td>\n7.2.5 Winding hot-spot rise <\/td>\n<\/tr>\n
34<\/td>\n7.2.6 Exponents for temperature rise equations
7.2.7 Adjustment of test data for different tap position <\/td>\n<\/tr>\n
35<\/td>\n7.3 Computer calculation of loading capability <\/td>\n<\/tr>\n
36<\/td>\n7.4 Bibliography for Clause 7 <\/td>\n<\/tr>\n
38<\/td>\n8. Loading of distribution transformers and step-voltage regulators
8.1 Life expectancy
8.1.1 General
8.1.2 Normal life expectancy
8.2 Limitations
8.2.1 General <\/td>\n<\/tr>\n
39<\/td>\n8.2.2 Limitations for loading distribution transformers above nameplate rating
8.3 Types of loading
8.3.1 Loading for normal life expectancy under specific conditions
8.3.2 Loading by top-oil temperature <\/td>\n<\/tr>\n
42<\/td>\n8.3.3 Continuous loading based on average winding test temperature rise
8.3.4 Short-time loading with moderate sacrifice of life expectancy (operation above 110 \u00b0C hottest- spot temperature)
8.4 Loading specific to voltage regulators
8.4.1 General <\/td>\n<\/tr>\n
43<\/td>\n8.4.2 Restricted regulation
8.4.3 Loading with reduced voltages
8.4.4 Limitations for loading voltage regulators above nameplate rating
9. Loading of power transformers
9.1 Types of loading and their interrelationship <\/td>\n<\/tr>\n
44<\/td>\n9.2 Limitations
9.2.1 Temperature or load limitations <\/td>\n<\/tr>\n
45<\/td>\n9.2.2 Ancillary components
9.2.3 Risk considerations
9.3 Normal life expectancy loading
9.3.1 General <\/td>\n<\/tr>\n
46<\/td>\n9.3.2 Influence of ambient temperature on normal life expectancy loading
9.3.3 Normal life expectancy loading by top-oil temperature
9.3.4 Normal life expectancy loading by average winding test temperature rise <\/td>\n<\/tr>\n
48<\/td>\n9.4 Planned loading beyond nameplate rating
9.5 Long-time emergency loading
9.6 Short-time emergency loading <\/td>\n<\/tr>\n
49<\/td>\n9.7 Loading information for specifications
9.8 Operation with part or all of the cooling out of service <\/td>\n<\/tr>\n
50<\/td>\nAnnex A (normative) Thermal evolution of gas from transformer insulation
A.1 General <\/td>\n<\/tr>\n
51<\/td>\nA.2 Experimental verification <\/td>\n<\/tr>\n
52<\/td>\nA.3 Determination of equation parameters
A.4 Example <\/td>\n<\/tr>\n
53<\/td>\nA.5 Bibliography for Annex A <\/td>\n<\/tr>\n
55<\/td>\nAnnex B (normative) Effect of loading transformers above nameplate rating on bushings, tap changers, and auxiliary components
B.1 Bushings
B.1.1 General <\/td>\n<\/tr>\n
56<\/td>\nB.1.2 Draw leads in bushings
B.2 Tap-changers
B.2.1 Tap-changers for de-energized operation (TCDO) <\/td>\n<\/tr>\n
57<\/td>\nB.2.2 Load tap-changers <\/td>\n<\/tr>\n
59<\/td>\nB.3 Bushing-type current transformers
B.3.1 General
B.4 Insulated lead conductors
B.5 Bibliography for Annex B <\/td>\n<\/tr>\n
60<\/td>\nAnnex C (informative) Calculation methods for determining ratings and selecting transformer size
C.1 General
C.2 Calculation determining loading beyond nameplate rating of an existing transformer <\/td>\n<\/tr>\n
65<\/td>\nC.3 Planned loading beyond nameplate (PLBN) <\/td>\n<\/tr>\n
66<\/td>\nC.4 Long-time emergency loading (LTE) <\/td>\n<\/tr>\n
67<\/td>\nC.5 Short-time emergency (STE) loading <\/td>\n<\/tr>\n
69<\/td>\nAnnex D (normative) Philosophy of guide applicable to transformers with 55 \u00b0C average winding rise (65 \u00b0C hottest-spot rise) insulation systems
D.1 General <\/td>\n<\/tr>\n
70<\/td>\nD.2 Aging equations <\/td>\n<\/tr>\n
71<\/td>\nAnnex E (normative) Unusual temperature and altitude conditions
E.1 Unusual temperatures and altitude
E.2 Effect of altitude on temperature rise
E.3 Operation at rated kVA
E.4 Operation at less than rated kVA <\/td>\n<\/tr>\n
72<\/td>\nE.5 Bibliography for Annex E <\/td>\n<\/tr>\n
73<\/td>\nAnnex F (normative) Cold-load pickup (CLPU)
F.1 General
F.2 Duration of loads
F.3 CLPU ratio <\/td>\n<\/tr>\n
74<\/td>\nF.4 Other considerations <\/td>\n<\/tr>\n
75<\/td>\nF.5 Bibliography for Annex F <\/td>\n<\/tr>\n
76<\/td>\nAnnex G (informative) Alternate temperature calculation method
G.1 General
G.2 List of symbols <\/td>\n<\/tr>\n
80<\/td>\nG.3 Equations
G.3.1 Introduction <\/td>\n<\/tr>\n
81<\/td>\nG.3.2 Average winding temperature <\/td>\n<\/tr>\n
83<\/td>\nG.3.3 Winding duct oil temperature rise over bottom oil <\/td>\n<\/tr>\n
84<\/td>\nG.3.4 Winding hottest-spot temperature <\/td>\n<\/tr>\n
86<\/td>\nG.3.5 Average oil temperature <\/td>\n<\/tr>\n
88<\/td>\nG.3.6 Top and bottom oil temperatures <\/td>\n<\/tr>\n
89<\/td>\nG.3.7 Stability requirements <\/td>\n<\/tr>\n
90<\/td>\nG.3.8 Fluid viscosity and specific heats of materials <\/td>\n<\/tr>\n
91<\/td>\nG.3.9 Summary of exponents
G.3.10 Adjustment of rated test data for a different tap position
G.3.10.1 Top- and bottom-oil rise over ambient <\/td>\n<\/tr>\n
92<\/td>\nG.3.10.2 Average winding rise over ambient <\/td>\n<\/tr>\n
93<\/td>\nG.3.10.3 Hottest-spot rise over ambient <\/td>\n<\/tr>\n
94<\/td>\nG.3.11 Load cycles and ambient temperatures
G.4 Discussion <\/td>\n<\/tr>\n
95<\/td>\nG.5 Disclaimer statement
G.6 Computer program Input data for computer program <\/td>\n<\/tr>\n
105<\/td>\nG.7 Bibliography for Annex G <\/td>\n<\/tr>\n
106<\/td>\nAnnex H (normative) Operation with part or all of the cooling out of service
H.1 General
H.2 ONAN\/ONAF transformers
H.3 ONAN\/ONAF\/ONAF, ONAN\/ONAF\/OFAF, and ONAN\/OFAF\/OFAF transformers
H.4 OFAF and OFWF transformers
H.4.1 General <\/td>\n<\/tr>\n
107<\/td>\nH.4.2 Calculations
H.4.2.1 Equations <\/td>\n<\/tr>\n
109<\/td>\nH.4.3 Caution <\/td>\n<\/tr>\n
110<\/td>\nH.5 Forced-oil-cooled transformers with part of coolers in operation <\/td>\n<\/tr>\n
111<\/td>\nAnnex I (informative) Transformer insulation life
I.1 Historical perspectives <\/td>\n<\/tr>\n
112<\/td>\nI.2 Thermal aging principles <\/td>\n<\/tr>\n
116<\/td>\nI.3 Example calculations <\/td>\n<\/tr>\n
120<\/td>\nI.4 Bibliography for Annex I <\/td>\n<\/tr>\n<\/table>\n","protected":false},"excerpt":{"rendered":"

IEEE Guide for Loading Mineral-Oil-Immersed Transformers and Step-Voltage Regulators<\/b><\/p>\n\n\n\n\n
Published By<\/td>\nPublication Date<\/td>\nNumber of Pages<\/td>\n<\/tr>\n
IEEE<\/b><\/a><\/td>\n2012<\/td>\n120<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n","protected":false},"featured_media":111987,"template":"","meta":{"rank_math_lock_modified_date":false,"ep_exclude_from_search":false},"product_cat":[2644],"product_tag":[],"class_list":{"0":"post-111986","1":"product","2":"type-product","3":"status-publish","4":"has-post-thumbnail","6":"product_cat-ieee","8":"first","9":"instock","10":"sold-individually","11":"shipping-taxable","12":"purchasable","13":"product-type-simple"},"_links":{"self":[{"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/product\/111986","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/product"}],"about":[{"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/types\/product"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/media\/111987"}],"wp:attachment":[{"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/media?parent=111986"}],"wp:term":[{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/product_cat?post=111986"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/pdfstandards.shop\/wp-json\/wp\/v2\/product_tag?post=111986"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}