IEEE Std 242-1986 Table 11 Conductor Temperature

[YellowDressGreenHair]

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.

 

[7anoter4]

The standard 242/1986 is obsolete and the new editions it is 2001.In this edition cable protection is in chapter 9 and Table 9-4 presents typical emergency temperature for different cable insulation.
No such a table [Table 11 as you said] is in this edition.
The standard UL 44 states the thermoplastic insulation maximum temperature.
[UL Standard for Safety for Thermoplastic-Insulated Wires and Cables, UL 83]
Table 5.1 maximum temperature for THWN 75oC dry or wet
Table 5.2 maximum temperature for THHN 90oC.
For short-circuit current cable protection see chapter 9 of IEEE 242/2001 and for conductor resistance at 20 and 25oC see UL 1581 [Table 30.1 up to 30.11] or NEC chapter 9.

 

[dpc]

It's the temperature of the conductor (this is reference temperature for the resistance values given). The NEC covers derating based on ambient temperatures. It seems that there was a long discussion on this a few months back?

 

[7anoter4]

If you need the maximum short-circuit current in order to compare with
the maximum current which the installation could overcome,you need the minimum temperature-it could be the average ambient or less.
For protection purpose you need the minimum short-circuit current, also, and then you may take the maximum permissible[ even in emergency overload, may be] temperature of the conductor.