Error in NFPA 70E Table 130.2(C)

[jtinge]

Restricted Approach Distances in NFPA 70E-2009, Table 130.2(C), for 72.6kV to 121kV and 161kv to 169kV are both shown as 1.29m. This matches up with the NESC Tables 441-1 and 441-2 from which these distances are derived. The conversion of the 1.29m distance is 4 ft-3 in. In Table 130.2(C), the 1.29m meter distance is correct for both voltage ranges; however, for 72.6kV to 121kV, instead of showing an equivalent distance of 4 ft- 3 in, it shows an incorrect distance of 3 ft- 4in. Has any one else noticed this? Was the 3 and the 4 transposed during the printing of this table?

 

[TxEngr]

Nice catch. Looking at the tables, I would think that the error was in the 1.29 meters rather than the footage since the higher the voltage, the greater the distance. 3'-4" would be 1.02 meters which fits nicely between 1.0m and 1.15m. I'll be interested in hearing if anyone knows anything about this.

I did a quick check of the 2012 proposed changes and noted that somone had marked this to be changed to 1.029m which makes more sense.

 

[jtinge]

The 1.29m appears to be correct for 72.5kV. This is the way it shows in both the NESC and NFPA 70E. It does go down to 1.15m at 121kV, then back up to 1.29m at 161kV. The dip is explained by the fact that there is an ergonomic factor that is higher at distribution voltages and is reduced once you get to 121kV. Other than that, it appears that the error in the 70E table is a simple transposition of the 3 and the 4 in the ft-in conversion at 72.5kV.