IEEE 738 2013

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IEEE Standard for Calculating the Current-Temperature Relationship of Bare Overhead Conductors

Published By	Publication Date	Number of Pages
IEEE	2013	72

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Description

Revision Standard – Active. A method of calculating the current-temperature relationship of bare overhead lines, given the weather conditions, is presented. Along with a mathematical method, sources of the values to be used in the calculation are indicated. This standard does not undertake to list actual temperature-ampacity relationships for a large number of conductors nor does it recommend appropriately conservative weather conditions for the rating of overhead power lines. It does, however, provide a standard method for doing such calculations for both constant and variable conductor current and weather conditions.

PDF Catalog

PDF Pages	PDF Title
1	IEEE Std 738™-2012 front cover
3	Title page
5	Important Notices and Disclaimers Concerning IEEE Standards Documents
8	Participants
12	Introduction
13	Contents
15	IMPORTANT NOTICE 1. Overview 1.1 Scope 1.2 Disclaimer
16	2. Definitions
17	3. Units and identification of letter symbols
19	4. Temperature calculation methods
21	4.1 Steady-state case 4.1.1 Steady-state thermal rating 4.1.2 Steady-state conductor temperature for a given current and ambient temperature
22	4.2 Transient calculations 4.2.1 Transient conductor temperature
23	4.2.2 Transient thermal rating 4.2.3 Fault current calculations 4.3 Time-varying weather and current calculations
24	4.4 Formulas 4.4.1 Steady-state heat balance 4.4.2 Non-steady-state heat balance 4.4.3 Convective heat loss
25	4.4.3.1 Forced convection
26	4.4.3.2 Natural convection 4.4.4 Radiated heat loss rate 4.4.5 Rate of solar heat gain
27	4.4.6 Conductor electrical resistance ([B7] and [B17]) 4.4.6.1 Limitations of linear interpolation of AC resistance
28	4.4.6.2 Skin effect component of AC resistance 4.4.6.3 Magnetic core effect on AC resistance 4.4.6.4 Radial thermal gradient component of AC/DC resistance
29	4.4.7 Radial temperature gradient within the conductor ([B16] and [B27])
30	4.4.8 Conductor heat capacity
31	4.5 Equations for air properties, solar angles, and solar heat flux 4.5.1 Dynamic viscosity of air (see also Table H.1) 4.5.2 Air density (see also Table H.1) 4.5.3 Thermal conductivity of air (see also Table H.1)
32	4.5.4 Altitude of the sun (see also Table H.2) 4.5.5 Azimuth of the sun (see also Table H.2)
33	4.5.6 Total heat flux density (heat intensity) at sea level versus Hc (see also Table H.3) 4.5.7 Elevation correction factor (see also Table H.4)
34	4.6 Sample calculations 4.6.1 Steady-state thermal rating 4.6.1.1 Problem statement
35	4.6.1.2 Air and conductor properties
36	4.6.1.3 Radiated heat loss (qr) 4.6.1.4 Solar heat gain (qs)
37	4.6.1.5 Resistance at 100 °C 4.6.1.6 Steady-state thermal rating
38	4.6.1.7 Check radial temperature steady-state thermal rating 4.6.2 Steady-state conductor temperature 4.6.3 Transient conductor temperature
40	4.6.4 Transient thermal ratings
41	4.6.5 Thermal time constant 4.6.6 Time-varying conductor current and weather conditions.
43	5. Input data 5.1 General
44	5.2 Selection of air temperature and wind conditions for line ratings 5.3 Air density, viscosity, and conductivity
45	5.4 Conductor emissivity and absorptivity 5.5 Solar heat gain
46	5.6 Conductor heat capacity 5.7 Maximum allowable conductor temperature
47	5.8 Time step
48	Annex A (informative) (“RATEIEEE” numerical method listing – SI units) flowchart of numerical method
58	Annex B (informative) Numerical example: steady-state conductor temperature calculation (SI units)
59	Annex C (informative) Numerical example: Steady-state thermal rating calculation (SI units)
60	Annex D (informative) Numerical calculation of transient conductor temperature
62	Annex E (informative) Numerical Calculation of Transient Thermal Rating
63	Annex F (informative) Conductor thermal time constant
65	Annex G (informative) Selection of weather conditions G.1 Base ratings
66	G.2 Study-based ratings G.3 Ambient-adjusted ratings G.4 Real-time ratings
67	Annex H (informative) Tables for solar heating and air properties
71	Annex I (informative) Bibliography

Additional information

Standard Title	IEEE Standard for Calculating the Current-Temperature Relationship of Bare Overhead Conductors
Published Code	IEEE
Publication Date	2013
Pages Count	72

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