1、ST/r : Standard CH DO.- /or FUSES ABOVE 600 VOLTS (Effective February 14, 1958) (Supersedes AIEE No. 251952) Published by AMERICAN INSTITUTE OF ELECTRICAL ENGINEERS 33 West Thirty-ninth Street, New York 18, N. Y. Table of Contents Scope 5 Service ConditionsDefinitions 6 Tests 9 Nameplate Markings 14
2、 Appendix A Recommended methods for determining the rms value of sinusoidal cur rent wave 5 Appendix B Simplified calculation of fault current ,. 19 Appendix C Recommended method of determining the equivalent steady-state rms current ,. 22 Appendix D Guide for the Operation and Maintenance of Fuses
3、of Rating Above 600 Volts 23 3 ACKNOWLEDGMENT The Institute wishes to acknowledge its indebtedness to those who have so freely given their time and knowledge, and have conducted experimental work on which many of the AIEE Standards are based. The work of preparing this standard was carried out by me
4、mbers of the Subcommittee on Switches, Fuses and Insulators of the AIEE Switchgear Committee. The members of the subcommittee are: J. B. Owens, Chairman R. H. Amundson F. W. Rich C. H. Baker A. C. Schwager T. E. Curtis F. R. Solis G. K. Ditlow C. W. Upton J. C. Lebens . P. Zimmerman A. H. Powell i S
5、tandardoJ theAmerican Institute of Electrical EngineersFUSES ABOVE 600 VOLTSSCOPEThis Standard applies to the following types ofdevices designed for operation above 600 voltswhether for indoor or outdoor service.(a) Fuses (see paragraph 25-50).(b) Fuse cutouts (see paragraph 25-64).(c) Fuse parts of
6、 combined equipment.SERVICE CONDITIONS25-1 Usual Temperature and Altitude ServiceConditions-Equipment conforming to these Stand ards shall be suitable for operation at its standardrating, provided that:(a) The temperature of the cooling air (am bient temperature) does not exceed 40C and cop per-to-c
7、opper contacts, or equivalent are used forfuse terminals and all conducting joints exceptthose of the conducting element.(b) The temperature of the cooling air (am bient temperature) does not exceed 55C if the fusehas all contacts silver surfaced or equivalent, andin addition has all conducting join
8、ts, except thoseof the conducting element, including terminal con nections, either:(1) Separately held mechanically and either sold ered or silver surfaced, or(2) Brazed, welded or silver soldered and pro vided that such operation does not result intemperatures in excess of 90C for Class 0,l05C for
9、Class A, or 130C for Gass B in sulations.(c) The altitude does not exceed 3300 feet( 1000 meters).Nate: Distribution cutouts are generally not suitable foroperating in an ambient temperature above 40C and suchapplications should be considered as unusual ambient temperature conditions. See paragraph
10、25-2.25-2 Unusual Temperature and Altitude ServiceConditions-The application of equipment athigher ambient temperatures or at higher alti-5tudes than specified in 25-1 shall be considered asspecial.Standard equipnlent may be applied at higherambient temperatures or at higher altitudes thanspecified,
11、 but its performance may be affected andspecial consideration should be given to these ap plications. (See paragraph 25-4).25-3 Other Conditions Which May Affect Designand Application-Where other unusual conditionsexist they should be brought to the attention ofthose responsible for the design and a
12、pplication ofthe equipment. Examples of such conditions are:(a) Damaging fumes or vapors, excessive orabrasive dust, explosive mixtures of dust or gases,steanl, salt spray, excessive moisture or drippingwater, etc.(b) Abnormal vibration, shocks, or tilting.(c) Excessively high or lov temperatures.(d
13、) Unusual transportation or storage condi tions.(e) Unusual space limitations.(/) Unusual operating duty, frequency of oper ation, difficulty of nlaintenance, poor wave fornl,unbalanced voltage, special insulation requirenlents,etc.25-4 Applications at Altitudes Greater than 3300Feet (1000 Meters)-E
14、quipment that depends onair for its insulating and cooling rnedium willhave a higher temperature rise and a lower di electric value when operated at altitudes higherthan 3300 feet.Withstand voltage and current ratings shouldbe multiplied by factors shown in Tables la and lb.Equipnlent designed for s
15、tandard temperaturerise may be used at its normal current ratingwithout exceeding ultimate standard temperaturelimits provided that the ambient telnperature doesnot exceed the ambient allowed in paragraph 25-1,multiplied by the factor shown in Table Ie.TABLE I Altitude Correction Altitude Correction
16、 Factor To Be Applied To a b c Altitude Withstand Feet 3300 4000 5000 6000 7000 8000 9000 10000 12000 14000 16000 18000 20000 The not to Meters 1000 1200 1500 1800 2100 2400 2700 3000 3600 4200 4800 5400 6000 correction be applied Voltage 1.00 .98 .95 .92 .89 .86 .83 .80 .75 .70 .65 .61 .56 Current
17、Rating 1.00 .995 .99 .985 .98 .97 .965 .96 .95 .935 .925 .91 .90 factors in columns at the same time. Ambient Temperature 1.00 .992 .980 .968 .956 .944 .932 .920 .896 .872 .848 .824 .800 b and c are If the derating as determined from the table is serious, equipment of a suitably higher rating should
18、 be chosen to meet requirements, after de rating factors have been applied. DEFINITIONS Definitions given below apply specifically to the apparatus treated in this Standard. Where possible, definitions given in American Standard Defini tions of Electrical Terms, C42, are used and such definitions ar
19、e followed by the C42 designating number. Where a slight change is made, the cor responding paragraph number is given with the notation Mod. Where there is no corresponding definition in C42, no reference is given. General 25-50 FuseA fuse is an overcurrent protective device with a circuit-opening f
20、usible member directly heated and severed by the passage of overcurrent through it. (20.20.005) 25-51 Vented FuseA vented fuse is a fuse which during circuit interruption may eject forcibly arc gases, solid particles, liquid or other material into the surrounding atmosphere. 25-52 Non-Vented FuseA n
21、on-vented fuse is a fuse which during circuit interruption does not eject forcibly arc gases, solid particles, liquid or other material into the surrounding atmosphere. Construction 25-53 Current-Responsive Element The current-responsive element of a fuse is the conducting sec tion with predetermine
22、d characteristics, the melting and/or severance of which initiates the interrup tion function of the fuse. (The current-responsive element may consist of the combination of a fusible element and, when used, a strain element.) 25-54 Conducting ElementThe conducting element of a fuse is the conducting
23、 means, including the current responsive element, for completing the electric circuit between the terminals of the fuse holder. 25-55 Arc Extinguishing MediumThe arc extin guishing medium of a fuse is the material included in the fuse to facilitate current interruption. 25-56 Refill UnitA refill uni
24、t of a fuse is an assembly comprising a conducting element, the complete arc extinguishing medium and parts normally required to be replaced after each circuit interruption to restore the fuse to its original operating condition. 25-57 Fuse LinkA fuse link is a replaceable part or assembly comprised
25、 entirely or principally of the conducting element required to be replaced after each circuit interruption to restore the fuse to operating condition. 25-58 Fusible Element A fusible element is the current-carrying part of a fuse unit designed to sever under stated conditions. 25-59 Fuse TubeA fuse
26、tube is a tube of insulating material which encloses the conducting element. (20.20.080 Mod.) 25-60 Fuse HolderA fuse holder is an assembly of a fuse tube or tubes, together with parts necessary to enclose, and provide means of making contact with, the conducting element and the fuse clips. The fuse
27、 holder does not include the conducting element. (20.20.090 Mod.) 25-61 Fuse UnitA fuse unit is an assembly com prising a conducting element mounted in a fuse holder with parts and materials in the fuse holder essential to the operation of the fuse. 25-62 Fuse Clips (Fuse Contacts)Fuse clips are cur
28、rent-carrying parts of a fuse support which engage the fuse holder. (20.20.100 Mod.) 25-63 Fuse Support (Fuse Mounting)A fuse sup port is an assembly of base, insulating means, and fuse clips for mounting a fuse holder and connect ing it into the circuit. (20.20.110 Mod.) 25-64 Fuse CutoutA fuse cut
29、out is an assembly of a fuse support and fuse holder which may or may not include a fuse link or conducting element. (20.20.115 Mod.) (a) Enclosed Fuse CutoutAn enclosed fuse cutout is a fuse cutout in which the fuse clips and fuse holder are mounted completely within an en closure. (20.20.120) 6 (b
30、) Open Fuse CutoutAn open fuse cutout is a fuse cutout in which the fuse support and fuse holder or fuse link are exposed. (20.20.125 Mod.) (c) Open Link Fuse CutoutAn open link fuse cutout is a fuse cutout which does not employ a a fuse holder and in which the fuse support di rectly receives an ope
31、n link fuse link. (d) Oil Fuse CutoutAn oil fuse cutout is an enclosed fuse cutout in which all or a part of the fuse support is mounted in oil with provision for partial or complete immersion of the conducting element. (20.20.130 Mod.) Modifying Terms 25-67 Liquid-Fuse UnitA liquid-fuse unit is a f
32、use unit in which the arc is drawn through a liquid. (20.20.140 Mod.) 25-68 Solid-Material-Fuse UnitA solid-material-fuse unit is a fuse unit in which the arc is drawn through a hole in solid material. 25-69 Filled-Fuse UnitA filled-fuse unit is a fuse unit in which the arc is drawn through powdered
33、, granular or fibrous material. 25-70 Expulsion-Fuse UnitAn expulsion-fuse unit is one characterized by expulsion of arc gases during interruption. (20.20.135 Mod.) 25-71 Renewable-Fuse UnitA renewable-fuse unit is a fuse unit which, after circuit interruption, may be restored for service. (a) Field
34、 Renewable-Fuse UnitA field re newable-fuse unit is a fuse unit which, after circuit interruption may be readily restored for service by the replacement of the fuse link or refill unit. (b) Factory Renezvable-Fuse UnitA factory renewable-fuse unit is a fuse unit which, after circuit interruption, mu
35、st be returned to the manu facturer to be restored for service. 25-73 Drop-Out FuseA drop-out fuse is a fuse in which the fuse holder automatically drops into an open circuit position after the fuse has interrupted the circuit. 25-75 Fuse Disconnecting Switch (or Disconnecting Fuse)A fuse disconnect
36、ing switch is a discon necting switch in which a fuse unit forms a part of the blade. (20.20.155) 25-76 Indicating FuseAn indicating fuse is a fuse which automatically indicates that the fuse has interrupted the circuit. 25-77 Reclosing FuseA reclosing fuse is a com bination of several fuse holders
37、or fuse units mounted on a fuse support or supports, mechani cally or electrically interlocked, so that one fuse can be connected into the circuit at a time and the functioning of that fuse automatically connects the next fuse into the circuit, with or without additional time delay, thereby permitti
38、ng one or more service restorations without replacement of fuse links, refill units or fuse units. 25-78 Current-Limiting Fuse A current-limiting fuse is a fuse which, when interrupting a specified circuit, will consistently limit the short-circuit cur rent of that circuit to a magnitude substantial
39、ly less than that obtainable in the same circuit with the fuse bypassed. Performance Terms 25-79 Melting Time of a FuseThe melting time of a fuse is the time required for the current to sever the current responsive element under specified con ditions. (20.20.050 Mod.) 25-80 Arcing Time of a FuseThe
40、arcing time of a fuse is the time elapsing from the severance of the current responsive element to the final interruption of the circuit under specified conditions. (20.20.055 Mod.) 25-81 Clearing Time (Total Interrupting Time) of a FuseThe clearing time of a fuse is the total time, measured from th
41、e beginning of a specified overcurrent condition to interruption of the cir cuit at maximum design voltage. The clearing time is equal to the sum of the melting time and the arcing time. (20.20.060 Mod.) 25-82 Current-Limiting Characteristic of a Fuse The current-limiting characteristic of a fuse is
42、 expressed by a curve showing the relation between the rms short-circuit current (including the d-c component) available in the circuit and the maxi mum instantaneous peak current permitted by the fuse during circuit interruption. 25-83 Recovery Voltage Recovery voltage is the voltage impressed upon
43、 a fuse after the current has been interrupted. (a) Normal-Frequency Recovery VoltageThe normal-frequency recovery voltage is the normal-frequency rms voltage impressed upon a fuse after the current has been interrupted and after high-frequency transients have subsided. (b) Transient Recovery Voltag
44、eThe transient recovery voltage is the transient voltage impressed upon a fuse immediately after the current has been interrupted or substantially limited. (c) Rate of Rise of Transient Recovery Volt ageThe rate of rise of transient recovery voltage is the rate at which the voltage rises across the
45、contacts of a fuse during the transient period, immediately after the current has been interrupted or substantially limited. 7 Installation 25-84 Mounting PositionThe mounting of a fuse is determined by and corresponds to the position of the base of the fuse support, and may be designated as: (a) Ve
46、rtical. (b) Horizontal-Upright. (When fuse holder is to be mounted above the supporting insulators.) (c) Horizontal-Underhung. (When fuse holder is to be mounted below the supporting insulators.) (d) Angle (from vertical). Rating 25-100 RatingA rating of a device is a designated limit of operating c
47、haracteristics based on definite conditions. Ratings of equipment covered by this Standard shall include the items indicated in the following table. Rated Voltage , , Maximum Design Rated Frequency Rated Continuous Rated Time-Current Rated Interrupting Rated Withstand Voltage Rated Temperature Rise
48、TABLE II Fuse Link Fuse and Unit Refill Unit . X . X . X . X . X . X . X X X X X X Fuse Cutout Fuse Support and Fuse Holder X X X X X X X 25-101 Rated VoltageThe rated voltage of a device is the nominal system voltage on which it is in tended to be applied. 25-102 Maximum Design Voltage The maximum
49、design voltage of a device is the highest rms voltage at which it is designed to operate. 25-103 Rated FrequencyThe rated frequency of a device is the frequency of the circuit for which it is designed. 25-104 Rated Continuous CurrentThe rated contin uous current of a device is the designated limit in rms alternating current or direct current which it can carry continuously without deteriorating or exceeding the limit of permissible temperature rise. Note: Transient currents having a magnitu
