IEEE 55-1953 - IEEE Guide for Temperature Correlation in the Connection of Insulated Wire and Cables to Electronic Equipment.pdf

1、IEEE Guide for Temperature Correlation in the Connection of Insulated Wire and Cables to Electronic Equipment - THIS PAGE WAS BLANK IN THE ORIGINAL IEEE Std 55-1953 IEEE Guide for Temperature Correlation in the Connection of Insulated Wire and Cables to Electronic Equipment (Effective January 15, 19

2、53) THIS PAGE WAS BLANK IN THE ORIGINAL TABLE OF CONTENTS 1 NT I20 I GCT 10 N . . . . . . . . . . . . . . . . . . . . 3 SCOLE _. ._ . . . ._. 5 GENERAL _ . _._._._._. ._. 5 WIRE AND CABLE APPLICATION PRACTICES . Dry Locations Wet Locations Hot Locations Conductor Selection and Arrangenlent OPERATING

3、 LIMITATIONS . . . . . . . . . . . . . . . , . , . . . . . . . . . . . . . . 6 Desirable Operating Limits Thermal Loading Degree of Loading NECESSITY FOR TEMPERATURE CORRELATION . . . . . . . 6 SOURCES OF HEAT IN EQUIPMENT ENCLOSURES . . . . . . 6 TEMPERATURE RISES WITHIN ENCLOSURES . . . . . . . .

4、. . . 7 MAXIMUM OPERATING TEMPERATURES ._. 7 AIEE General Standards Insulated Wire and Cable Copper Temperature Limits AMBIENT TEMPERATURES WR RATING PURPOSES . . . . 7 AIEE General Standards Insulated Wires and Cables VARIATION 0 F CAB LE CURRENT-CARRY I NG CAPABILITY WITH AMBIENT TEMPERATURES. . .

5、 . . MEANS OF EFFECTING 8 TEMPERATURE CORRELATION . 8 ,.- . I .NNING” OF CABLES . 3 Fanning Effect Curves HEAT CONDUCTION FROM TERMINALS ._. 8 HIGH TEMPERATURE CABLE SECTION SPLICED IN. . . 9 RADIATORS AT THE POINT OF CONNECTIOS . . . _. . . 9 TERMINAL CONNECTIONS MADE IN .4 COOL LOCATION . 9 SUPPLE

6、MENTAL COMPARTMENTATION ._. 9 SPECIAL VENTING _._. . _ _ _. _ _ . . _ . . . _._. . . 9 ROOM COOLING _._._._._._ ._ ._ _._. 9 POTHEAD CORRELATION _. ._ ._ . . . . 9 INSTRUblENT TRANSFORMER CORRELATION. . . 9 10 CONCLUSIONS . . . . . . . _. . . . . . . . . 3 ACKNOWLEDGMENT The Institute vishes to ackn

7、owledge its indebtedness to those who have so freely given their time and knowledge, and have conducted experimental work on which many of the AIEE publications are based. The work of preparing this guide was carried out by a Project Com- mittee appointed by the AIEE Standards Committee. The personn

8、el of this Project Committee was as follows: J. E. Ckm, Choirman - R: L. Webb, Sccretary J. S. Brown J. H. Chiles K. G. Darrow C. T. Hatcher C. A. Jordan L. F. Kennedy C. P. West R. J. Wiseman J. C. Woods Alternates: R. W. Burrell C. C. Schackford 4 GUIDE FOK TEMlERATUIt 1: CORIEIA1ION IN TIIE CONNE

9、CTION OF INSJlA.4rlIl WIRES AND CABLES TO ELECTRIC lt cxctcrl 5,000 volt.iiig IiiIicr tciieraiircs fnr yliort Iicriocls of tinlc, is accclt;il)lc. exctlit Ic)r t1io.c iiisuhtitmh vliicli ex- hibit sc.ritus tliernioil:istic teiitlcncy at tllc elcv:ltctl ciiitrgciicy tciiilicratiircs. EsccctlinG the n

10、insiiiiuiii iircwribcd coutluctor tcnii)crnturc, cithcr continuously or f r cqueii t 1 J. v ill a c c ck rat e cl c t c riora t ion of t I I e ins ti la t ion. Thermal Loading Electric equipinetit and connections in sonic types of apparatus are being operattd niore frequently in accordance with thci

11、r tliernial capability tliaii by nnnie- plate rating. This practice usss tlic iiiaxiniuni prc- scribed continuous tciiiiwrature as a base for estalr- lihiiig normal loading limits. Tlicrnial limitations in cables, instrument traiisiornicrs. and other equipinetit are bcing studied to pcrniit tlicriea

12、l loading. In some cases existing installations may be rcvainiml to pertnit operating tlic equipment at, or evcn above, the naiiie- plate rating. Degree of Loading Some types of equipment. or parts of equipment. such as potheads, or switchgear frames, are made with current-carrying conductors in a l

13、imited number of sizes. ;hen such equipniciit is used at its actual cur- rent-carrying rating in enclosures where the ambient temperature within the enclosures niay be in excess of 4OC. there is a possil is not accurately knc)wn. M:iiiit:kiiiinT tlic II:IYIIIIII coii- tluctor tcnipcraturc at values

14、nn xrc:ctcr tli:tii t1lo.c prescribed 114. the AIEllisli the current-carrying capability, without excccding pre- scribed copper temperature limits, vhen the maxi- niuni expected base ambient is different from the base reference value assumed for the tables. Before these corrections can be applied, t

15、he ani- bient temperatures niust be established. Because of local variations, surveys are desirable. Representative values quoted by IPCEA for air ambients are as follows: (a) In well ventilated buildings with- out other sources of heat. . . . . . .2SC to 30C (b) In buildings with other sources of h

16、eat, such as power stations and industrial plants . . . . . . . . . . . .35C to 40C (c) In poorly ventilated enclosures such as sun-exposed runways. . . . .40C to 45C (d) Furnace and boiler roonis . . . . . . .4OC to 60C (e) In the shade outdoors . . . . . . . . . . .35C to 40C (f) Directly exposed

17、to hot sun. . . . 5OC Information on earth temperature variation can be found in the literature. A comprehensive survey was made by the Edison Electridnstitute (See “Earth Temperatures and Their Use in Cable Ratings,” NELA (EEI) Publication No. 021, December 1929). In recent years a nuniber of infor

18、mative articles have appeared in the literature in connection with heat pump studies. In northern localities, in this country, at usual depths of laying (3 to 6 feet) maximum (summer) earth temperature varies from 2OC to ZC, and in southern localities from 25C to 30C. Winter earth temperature will b

19、e appreciably lower. There niay be appreciable time lag between the air temperature and the earth temperature. VARIATION OF CABLE CURRENT- CARRYING CAPABILITY WITH AMBIENT On the basis of current-squared conductor tenipera- ture rises curves of the type of Fig. 2 indicate the effect of current-carry

20、ing capability of cable installa- tions in air operating in ambieiit tcmperatures other than the base value of 1OC. Fig. Z corresponds to tlic correction factors discurscd under the heading Ah- BIENT TEMPERATURES. Im/o!cd Wirc aid Cnhlc. In addition to tlic tliermal limitations of the limit- ing con

21、ductor teinpcraturcs and the basic rcierence ambient teniperatures. special coritlitio.; arc at tinics encountered wliich niu.-t be give11 c;ircful consitlcra- tion in tlic al)plicntioii of insulated conductors. Some exaniplcs arc: 1. 3 L. MEANS OF EFFECTING TEMPERATURE CORRELATION FANNING “Fanning”

22、 oP Cable The term “fanning” is used to designate the spread- ing out. to facilitate connections to equipment ternii- nals, of cables after they leave the conduit. In the case of most enclosed electric equipment, the conduit makes connection to the enclosure and the cable rum separated from there to

23、 the terminal points. This “fanning” term applies a!so when a single cable is carried in one conduit and then runs in air inside of the equipment. “Fanning” Effect Curves In either of these rases, there is a favorable teni- perature margin available as soon as the cable is fanned out leaving the con

24、duit, the-conductor tem- perature rise being higher in the conduit run, primarily because of the close proximity of the cables. Curves, Fig. 3 and 4 indicate the temperature ad- vantages of fanning of cable. The ampere ratings and the temperature rise data given are in accordance with data listed in

25、 IPCEA Publication P-29-26 (First Edition, Dec. 1943). Reference to these curves shows that, if the circuit consists of three cables in one con- duit until it arrives at the enclosed equipment and it is there “fanned-out” in air within tlie equipment, a .substantial temperature margin is normally av

26、ailable to assist in tenipcrature correlation of cable insula- tion in an area where !5C additional am1)ient temper- ature is pcrniitted by the standards. A similar condition exists vlicn one cable in one conduit changes to one cable in air. T!icse tvo curves arc sufticiently accui-ate for all pract

27、ical purposes. As an cxaniplc. refer to Fig. .3:-if tlirce 250 hfCM single-conductor c;il)lcs iii one conduit are fanned out to tlirce single conductors in single conduits, the teni- Iicrature rise i.; rc(lucctl almut 13C. aiici if tile cables arc faiinctl into ail- ail xtlt1ition;il retluct ion of about 8C occurs. 8