reduction factor for power cable laid vertically in ladder

[xiake]

hello,
In wind power generator, power cables are laid vertically along ladder from ground to nacelle of above 100 meters height. The cables are installed in method F according to IEC 60364-5-52(single-core cables with three loaded conductors in trefoil),The clearance between trefoil groups are kept lager than two times the cable diameter, and the trefoil groups are erected on a cable ladder which are installed vertically.
I don't find reduction factors for cable using this installation method in this IEC standard.
Who can provide a reference for ampacity calculation of cable laid vertically in ladder?
Thanks!

 

[7anoter4]

If the ladder is in open air [not enclosed in conduit or cable trunking] and it is not exposed to the sun radiation no correction is needed.
BS 7671 and IEC 60364-5-52 pos.34 on cable ladder-consider reduction only if the ventilation is restricted.
In IEEE 835/1994 3.5.7 Vertical cables in air-cable riser-a method for cable carrying capacity[ampacity] calculation is presented but only for cable in unventilated riser.

 

[xiake]

Thanks for your reply. I have one more question.
In our application, vertical cables are erected in 2 parallel ladders, where ladders are installed vertically next to each other a minimum distance between the ladders of about 2 times the cable diameter.
Is there any reduction factor for this cable installation method?

 

[7anoter4]

 

[xiake]

Yes.
actually, cables are fixed by cleats as attached picture. the distance between two cable layers is 2 times the cable diameters.

 

[7anoter4]

It seems to me according to ABB Switchgear Manual 11 edition-attached here-in your case a 0.9 factor has to be employed.

 

[7anoter4]

I am sorry,wrong file

 

[7anoter4]

It seems to me IEC 60364-5-52 Table A.52-21 is the same as per ABB Switchgear Manual
However, if the cable diameter is less than 225/2=113 mm you have to consider this as a bunched group of cables. [Table A.52-17]
Calculating for trefoil 8 groups of 240 sq.mm copper 0.6/1kV no reducing factor.

 

[7anoter4]

Following TEMPERATURE RISE OF SUBMARINE CABLE ON RISER POLES by J.Motlis/IEEE Ontario Hydro [IEEE TRANSACTION ON POWER DELIVERY VOL.6 NO.1 /1991]
calculation way for 8*3*1*240 sq.mm copper 0.6/1 kV [IEC 60502-1] the result could be 418 A [68.86 % of 607 as per IEC 60364-5-52 Table A.52-12].

 

[xiake]

Thanks for your kindly reply, @ 7anoter4.

Yes, IEC 60364-5-52 table B 52-21 has the same content as ABB switchgear manual.
But the cable in the standard runs horizontally, not vertically. I guess cables fixed vertically will provide better heat dissipation.
However, the diameter of 240sq. mm copper cable is about 30 mm, and distance between cable group is about 62 mm, which is less than 225 mm.