wind farm collection system 1

[rlcguy]

What would be the advantage to installing a 34.5kv collection system where the cables are kept seperated by a minimum of seven inches horizontally vs. zip tied together every 4 feet, or does it matter? This is at a wind farm. I have seen them done both ways. Of course the engineers who designed them aren't available for questioning. It seems that there shouldn't be a need for cross cancellation due to the generator producing a balanced load. I have heard that you can follow the buried circuit over snowy areas where they are zip tied as they heat the ground, I haven't been back to see it though.

 

[davidbeach]

Makes sense to me. All together in one location makes for a greater heat concentration compared to having them separated. All together means less inductive reactance and more shunt capacitance while separated means more inductive reactance and less shunt capacitance. Pick your poison.

 

[cranky108]

One important consiteration for some farms is that the cables be transposed to keep equal voltages on the three phases. This can be accomplished by zip tieing the cables togather, or make an effort to transpose them when they are spaced.

Consitering the installers point of view, it's just easer to zip tie the cables and not worry about transpositions.

 

[jghrist]

Cables close together have lower shield currents (and lower losses and heating from the shield currents), but higher mutual heating from being closer to the other cables (heat sources).

 

[rlcguy]

Thank you all for your replies. jghrist, where can I get more info regarding youor comments? Thanks

 

[jghrist]

jghrist, where can I get more info regarding youor comments?

From calculation methods for ampacity.

Neher, J.H., and McGrath, M.H. (Oct. 1957), "The calculation of the temperature rise and load capability of cable systems," AIEE Trans., vol. 76, part 3, pp. 752-772

IEC Standard 287 (1982), "Calculation of the continuous current rating of cables (100% load factor)," 2nd ed., 3rd amendment, 1993.

Anders, G.J., Rating of Electric Power Cables, McGraw-Hill, IEEE Press, 1997.