YellowDressGreenHair
Electrical
- Oct 4, 2023
- 1
In IEEE Std 242-1986, there is a table named "Table 11 - 60 Hz Low-voltage Cable in Conduit - Resistance and Reactance Data for Insulation Types THWN and THHN in Milliohms per Conductor per 100 ft at 25 deg Celsius Copper Conductor"
We know that as per NEC, the temperature rating of THWN is 75 deg Celsius while THHN is 90 deg Celsius. I guess we can call this rating the "Operating Temperature". Therefore, I am assuming that the 25 deg Celsius from Table 11 indicates "Ambient Temperature".
Now for my question, supposed that the 25 deg Celsius from the table is an Ambient Temperature, is it necessary to adjust the resistance values from this table to the "Operating Temperature" of THWN (75) or THHN (90)? Yes I'm using these data for calculating the Rpu of a THHN Feeder for Short Circuit calculation.
We know that as per NEC, the temperature rating of THWN is 75 deg Celsius while THHN is 90 deg Celsius. I guess we can call this rating the "Operating Temperature". Therefore, I am assuming that the 25 deg Celsius from Table 11 indicates "Ambient Temperature".
Now for my question, supposed that the 25 deg Celsius from the table is an Ambient Temperature, is it necessary to adjust the resistance values from this table to the "Operating Temperature" of THWN (75) or THHN (90)? Yes I'm using these data for calculating the Rpu of a THHN Feeder for Short Circuit calculation.