1、ANSI/ICEA P-45-482-2017 Short Circuit Performance of Metallic Shields and Sheaths on Insulated Cable NOTICE AND DISCLAIMER The information in this publication was considered technically sound by the consensus of persons engaged in the development and approval of the document at the time it was devel
2、oped. Consensus does not necessarily mean that there is unanimous agreement among every person participating in the development of this document. The Insulated Cable Engineers Association. Inc. (ICEA) standards and guideline publications, of which the document contained herein is one, are developed
3、through a voluntary consensus standards development process. This process brings together persons who have an interest in the topic covered by this publication. While ICEA administers the process and establishes rules to promote fairness in the development of consensus, it does not independently tes
4、t, evaluate, or verify the accuracy or completeness of any information or the soundness of any judgements contained in its standards and guideline publications. ICEA disclaims liability for personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential
5、, or compensatory, directly or indirectly resulting from the publication, use of, application, or reliance on this document. ICEA disclaims and makes no guaranty or warranty, expressed or implied, as to the accuracy or completeness of any information published herein, and disclaims and makes no warr
6、anty that the information in this document will fulfill any of your particular purposes or needs. ICEA does not undertake to guarantee the performance of any individual manufacturer or sellers products or services by virtue of this standard or guide. In publishing and making this document available,
7、 ICEA is not undertaking to render professional or other services for or on behalf of any person or entity, nor is ICEA undertaking to perform any duty owed by any person or entity to someone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate, seek
8、 the advice of a competent professional in determining the exercise of reasonable care in any given circumstances. Information and other standards on the topic covered by this publication may be available from other sources, which the user may wish to consult for additional views or information not
9、covered by this publication. ICEA has no power, nor does it undertake to police or enforce compliance with the contents of this document. ICEA does not certify, test, or inspect products, designs, or installations for safety or health purposes. Any certification or other statement of compliance with
10、 any health or safety-related information in this document shall not be attributable to ICEA and is solely the responsibility of the certifier or maker of the statement. ICEA P-45-482-2017 Page i CONTENTS Page Foreword . ii Section 1 GENERAL 1 1.1 SCOPE . 1 1.2 REFERENCES . 1 Section 2 FORMULAE AND
11、CALCULATIONS . 3 Section 3 Tabulated Parameters . 5 Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 LIST OF TABLES Formulas for Determining Metallic Shield/Sheath Cross-sectional Area . . 4 Parameters for Use in Equations (1 ), (2) or (3) . 5 Values of T1, Approximate Shield or Sheath Operating Temp
12、erature, C at Various Conductor Temperatures 5 Values for Tz, Maximum Allowable Shield or Sheath Transient Temperature, C 6 M Values for Tz Temperature of 200 C . 6 M Values for Tz Temperature of 350 C . 7 Copyright 2017 by the Insulated Cable Engineers Association, Incorporated. ICEA P-45-482-2017
13、Page ii Foreword This publication discusses factors for consideration in approximating the operability of insulated and/or covered wire and cable under the influence of uninterrupted short circuit currents encountered as a result of cable or other equipment faults. The duration of such a fault is co
14、nsidered to be up to approximately 2 seconds. Calculation for single short circuits of longer durations will yield increasingly conservative results. The following items must be considered in order to estimate the short circuit performance of a specific circuit: 1. The magnitude and duration of the
15、fault current including any fault current division due to available conducting paths. 2. The capability of joints, terminations and other accessories in the affected circuit to withstand the thermal and mechanical stresses created by the fault. 3. The interaction between the faulting circuit and sur
16、rounding equipment, such as supports, ties and clamps. 4. The capability of the affected cable circuit, as installed, to withstand the electromagnetic forces created during the fault. 5. The maximum temperature that cable components can withstand without incurring damage due to heating caused by fau
17、lt current flow. 6. Damage to adjacent equipment due to arcing at the site of the fault. 7. For limitations imposed on the short-circuit current in the cable phase conductor see ICEA Publication P-32-382, Short Circuit Characteristics of Insulated Cable. An important simplifying assumption in the fo
18、rmula is the adiabatic nature of the heat generated, i.e., the duration of the fault is so short that all the heat developed by the fault current during this time is assumed to be completely contained within the sheath or shield. The amount of heat dissipated from the sheath or shield during continu
19、ous, single fault occurrences of relatively short duration is small. A significant amount of heat may be dissipated because of the relatively long cooling periods involved for faults interrupted and reestablished with automatic reclosing of circuit protective devices. A non-adiabatic calculation may
20、 be more suitable for these situations and for single. uninterrupted short circuits in excess of 2 seconds requiring close accuracy. Non-adiabatic calculation methods are described in several published works listed in Section 1.2 “References“. The formula (1) described in this publication is based o
21、n the thermal capacity of the metallic sheath/shield material and the transient temperature limit of the adjacent cable component materials. The quantity of heat contained in the metallic sheath/shield is that created by the fault current and is also a function of the temperature rise in the metalli
22、c sheath/shield. The magnitude of the temperature rise is the difference between the upper temperature of the cable material in contact with the sheath/shield and the operating temperature of the sheath/shield immediately prior to the initiation of the fault. The operating temperature of the sheath
23、or shield depends on the temperature of the conductor and the insulation thickness which is determined by the cable voltage rating. See Section 3, Table 3 for suggested estimated values. ICEA P-45-482-2017 Page iii The maximum transient temperature limits of the cable component materials are those w
24、hich cause no significant change in the materials. These limits were extrapolated from laboratory test data. Suggestions for improvements in this publication are welcome, and should be sent to the ICEA website http:/ Copyright 2017 by the Insulated Cable Engineers Association, Incorporated. ICEA P-4
25、5-482-2017 Pageiv 1.1 SCOPE Section 1 GENERAL ICEA P-45-482-2017 Page 1 Equations and parameters have been established for short circuit calculations for sheaths or shields made of aluminum, bronze, copper, lead, steel, zinc and cupronickel alloys. The types of sheaths or shields included are: Wires
26、, applied either helically, as braid or serving; or longitudinally with corrugations. Helically applied flat tape, not overlapped. Helically applied, overlapped, flat tape. Corrugated tape, longitudinally applied. Tubular sheath. The types of cable materials in contact with the sheath or shield are:
27、 crosslinked (thermoset, thermoplastic, impregnated paper, and varnished cloth. The materials which determine the maximum allowable short circuit temperatures are: paper, varnished cloth and several thermoplastic and thermosetting materials presently appearing in ICEA standards. Temperature limits,
28、considered safe, were established for the various coverings and insulation materials. The equations may be used to determine: The maximum short circuit current permitted for a specific sheath/shield and short circuit duration. The sheath/shield size necessary to carry a specific short circuit curren
29、t for a given duration. The maximum duration a specific sheath/shield can carry a specific short circuit current. 1 REFERENCES The following references were reviewed in preparing this document. The Transient Temperature Rise of Round Wire Shields of Extruded Dielectric Cables Under Short Circuit Con
30、ditions, M. A. Martin Jr., A.W. Reczek Jr., IEEE-ICC Open Forum at 57 Meeting Nov. 17-19, 1975. Optimization of Design of Metallic Shield-Concentric Conductors of Extruded Dielectric Cables Under Fault Conditions. EPRI EL-3014, Project 1286-2, final Report 4/83. Optimization of Metallic Shields for
31、Extruded Dielectric Cables Under Fault Conditions, IEEE Paper 86 T or longitudinally with corrugations. 2. Helically applied tape, not overlapped. 1.27 nwb 3. Helically applied flat tape, overlapped. See NOTE 3. 4bd 100 ) m 2100 - L) 4. Corrugated tape, longitudinally applied. 5. Tubular sheath. NOT
32、E 1: Meaning of Symbols: A B b dis dm ds w n L = Effective cross-sectional area of shield or sheath, emil. =Tape overlap, mils (usually 375). = Thickness of tape, mils. = Diameter over extruded insulation screen, mils. = Mean diameter of shield or sheath, mils. = Diameter of wires, mils. =Width of t
33、ape, mils. = Number of serving or braid wires, or tapes. = Overlap of tape, percent. NOTE 2: NOTE 3: The effective area of composite shields is the sum of the effective areas of the components. For example, the effective area of a composite shield consisting of a helically applied tape and a wire se
34、rving would be the sum of the area calculated from Formula 2 (or 3) and Formula 1. The effective area of thin, helically applied overlapped tapes depends, also, upon the degree of electrical contact resistance of the overlaps. Formula 3 may be used to calculate the effective cross-sectional area of
35、the shield for new cable. An increase in contact resistance may occur after cable installation, during service exposed to moisture and heat. Under these conditions the contact resistance may approach infinity, where Formula 2 could apply. Copyright 2017 by the Insulated Cable Engineers Association,
36、Incorporated. Section 3 TABULATED PARAMETERS Table 2 Parameters for Use in Equations (1), (2) or (3) Suggested Values for Properties of ICEA P-45-482-2017 Page 5 K Material Metals at To= 20 C Calculated from SG SH Aluminum* 2.70 0.22 Bronze* 8.80 0.094 Coppert 8.93 0.092 Leadtt 11 .3 0.031 Steel:t:
37、7.85 0.11 Zinc:t:j: 7.14 0.093 Cupronickel Alloys 8.94 0.09 90Cu-10Ni (C70600) 80Cu-20Ni (C71 000) 70Cu-30Ni (C71500) Three quarter hard, 1350 aluminum. * Commercial Bronze, 90% copper, 10% zinc. t Annealed 100% conductivity copper. tt Pure lead (99.99%). :j: Mild or low carbon steel. + Commercial r
38、olled zinc, 0.08% lead. Po “ Equation (2) 2.83 228 0.013 3.95 564 0.030 1.72 234 0.030 20.6 236 0.0011 12.0 180 0.0036 5.91 268 0.0080 1800 19.1 0.019 26.6 0.014 37.5 0.010 These values are believed accurate for the materials shown. Variations may occur due to small changes in composition. Nominal W
39、all Thickness (mils) (See NOTE 2) 220 221-344 345-449 450 Table 3 Values ofT 1, Approximate Shield or Sheath Operating Temperature, oc at Various Conductor Temperatures Shield or Sheath Temperature, C, at Conductor Temperatures (See NOTE 1) 105 oc 100 oc 95C 90 C 85C 80 C 75 C 70 C 65 oc 100 95 90 8
40、5 80 75 70 65 60 95 90 90 85 80 75 70 65 60 95 90 85 80 75 70 65 60 55 N/A N/A N/A 75 70 65 60 55 50 NOTE 1: The maximum conductor temperature should not exceed the normal temperature rating of the insulation used. For more accurate shield/sheath temperatures, contact the cable manufacturer. NOTE 2:
41、 For performance based design wall thicknesses please refer to ICEA S-113-684. Copyright 2017 by the Insulated Cable Engineers Association, Incorporated. ICEA P-45-482-2017 Page 6 Table 4 Values forT 2, Maximum Allowable Shield or Sheath Transient Temperature, C Cable Material in Contact with Shield
42、 or Sheath T 2 Crosslinked (thermoset) 350* High Heat Deformation* 350* Thermoplastic 200 Impregnated Paper 200 Varnished Cloth 200 NOTE: The temperature of the shield or sheath shall be limited by the material in contact with it. For example, a cable having a crosslinked semi-conducting shield unde
43、r the metallic shield and a crosslinked jacket over the metallic shield would have a maximum allowable shield temperature of 350 C. With a thermoplastic jacket it would be 200 C. *For lead sheaths this temperature is limited to 200 C. *See ICEA S-113-684 for definition of High Heat Deformation Table
44、 5 a ues or 2 empera ure o MVI f T T t f 200 C Values for M for the Limiting Conditions Where T 2 = 200 C Shield/Sheath Shield/Sheath Operating Temperature (T1), oc Material 100 95 90 85 80 75 70 65 60 55 50 Aluminum 0.039 0.040 0.041 0.042 0.043 0.044 0.045 0.046 0.047 0.048 0.049 Commercial Bronze
45、 0.043 0.044 0.045 0.046 0.047 0.048 0.049 0.050 0.051 0.052 0.053 Copper 0.058 0.060 0.062 0.063 0.065 0.066 0.068 0.070 0.071 0.073 0.074 Lead 0.011 0.011 0.012 0.012 0.012 0.012 0.013 0.013 0.014 0.014 0.014 Steel 0.022 0.022 0.023 0.024 0.024 0.025 0.026 0.026 0.027 0.027 0.028 Zinc 0.029 0.030
46、0.030 0.031 0.032 0.033 0.034 0.034 0.035 0.036 0.037 c k l upron1c e 90Cu-10Ni (C70600) 0.021 0.021 0.022 0.022 0.023 0.023 0.023 0.024 0.024 0.025 0.025 80Cu-20Ni (C71000) 0.017 0.018 0.018 0.019 0.019 0.020 0.020 0.020 0.021 0.021 0.021 70Cu-30Ni (C71500) 0.015 0.015 0.016 0.016 0.016 0.017 0.017
47、 0.017 0.018 0.018 0.018 Copyright 2017 by the Insulated Cable Engineers Association, Incorporated. Shield/Sheath Material 100 95 Aluminum 0.056 0.057 Commercial Bronze 0.065 0.066 Copper 0.085 0.086 Steel 0.031 0.032 Zinc 0.042 0.043 90Cu-10Ni (C70600) 0.032 0.032 80Cu-20Ni (C71000) 0.027 0.027 70C
48、u-30Ni (C71500) 0.023 0.023 Table 6 a ues or 2 empera ure o MVI f TT t f 350 C ICEA P-45-482-2017 Page 7 Values for M for the Limiting Conditions W here T 2 = 350 C Shield/Sheath Operating Temperature (T1), oc 90 85 80 75 70 65 60 55 50 0.058 0.059 0.060 0.060 0.061 0.062 0.063 0.063 0.064 0.066 0.0
49、67 0.068 0.068 0.069 0.070 0.070 0.071 0.072 0.088 0.089 0.090 0.091 0.092 0.093 0.094 0.096 0.097 0.032 0.033 0.033 0.034 0.034 0.035 0.035 0.036 0.036 0.044 0.044 0.045 0.045 0.046 0.046 0.047 0.047 0.048 c kl upron1c e 0.033 0.033 0.033 0.034 0.034 0.034 0.034 0.035 0.035 0.028 0.028 0.028 0.028 0.029 0.029 0.029 0.030 0.030 0.024 0.024 0.024 0.024 0.025 0.025 0.025 0.025 0.026 Copyright 2017 by the Insulated Cable Engineers Association, Incorporated.
