Calculates the thermal rating of an overhead transmission line using the IEEE-738 method. You can display help for any parameter by clicking on the 'help' links.
Select the type of conductor from the drop-down list. The Rating Calculator will calculate the rating using the conductor diameter and resistance parameters for the conductor you select.
If your particular conductor type is not found in the list, please contact Shaw EDS for assistance.
Emissivity is a material surface property which indicates the efficiency of the surface at cooling through the emission of thermal radiation. The emissivity of a surface can be between 0.00 and 1.00 but typical values for a conductor would be between 0.30 and 0.95.
Absorptivity is a material surface property which indicates the efficiency of the surface at absorbing incoming solar radiation. The absorptivity of a surface can be between 0.00 and 1.00 but typical values for a conductor would be between 0.40 and 0.95.
Enter the Air/Ambient temperature in degrees C. The specified temperature must be between -50.0 and +70.0.
A conductor is cooled by wind so wind speed and direction must be specified when calculating a conductor rating. Increasing wind speed will increase rating and a more perpendicular wind direction will increase conductor rating.
Wind speed is specified in feet per second. The wind speed must be between 0.0 and 50.0 feet per second. Wind direction is specified in degrees (between 0.0 and 90.0) relative to the conductor as shown in the following:
Solar intensity varies over date and time so the date and time must be specified.
Specify whether the conductor is operating in an area where the atmosphere is clear or industrial. Industrial polution blocks incoming solar radiation and decreases the effect of sunlight on conductor heating.
Elevation affects conductor rating for two reasons: 1) The density of air decreases with elevation and convective cooling capacity of air decreases with air density. 2) The intensity of solar radiation increases with elevation. Both of these factors have the effect of decreasing conductor rating as elevation increases.
Conductor elevation is specified in feet above sea level. For the Rating Calculator, the elevation must be between -200 and +20,000 feet above sea level.
The amount of solar radiation received is a function of latitude. Specify latitude in degrees from the equator with positive latitudes representing the northern hemisphere and negative latitudes representing the southern hemisphere.
The directional orientation of the conductor influences the amount of solar radiation the conductor receives, especially when the sun is low in the sky. Enter the orientation in degrees (-90 to +90) where 0 represents the conductor running in a north-south direction as shown in the following:
Specify the maximum temperature at which the conductor should operate. The calculating rating will be the maximum current that can be transferred over this line without exceeding the specified maximum conductor temperature. For sag-limited lines, this maximum temperature corresponds to the maximum allowable sag. The maximum temperature is specified in degrees C and must be between 50 and 200.
This field simply allows you to enter a brief description or other comment which will be included in the rating calculation report generated by the Rating Calculator.