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Dear all, is there any negative impact of operating one circuit of a double circuit overhead line at a lower voltage than its rating. For example having double circuit 225 kV line and operating one circuit at 225 kV and the other at 33 kV. From my perspective since it is a lower voltage there...

Hello again, is it possible to provide some links for examples that utilizes the approach we have here. you told me to go to google and search for IEC calcaution examples but i couldn't find much examples to support that this approach is the one practiced. Thank you

Hello, i agree with you that the cables inside the duct are in free air since IEC considers that when calculating T'4 by considering the temprature of the medium filling the duct. However, i would like first to get your opinion that the standard is not very clear especially when it comes to...

thank you, i had support from you to make that. now for my understanding: for singel-core conducter T1 is the heat from the insulation T3 is the the from the PVC jacket T'4 is the heat from the inside ambient of the Duct T"4 is the heat from the Duct thickness T'" 4 is the mutual heat from the...

its great that you have time to respond, i appreciate it but unfortunately i dont have the experience that you have and would like to know how to explain the usage of the equations in the standard. I attached a calculation example here. the challenge that i have is that i am getting a comment...

so calculating for the case i am describing is it a combination of touching and not touching? the 3 single-core cables are touching while the PVC ducts are not touching! i am convinced that using the section with touching is not correct! but i cant find a clear argument that i can use section...

how is the impact of the mutual heating inside the duct itself is accounted for in your opinion and in this case what is section 2.2.4.3.1 is used for!

but we are considering in this case three single-core cables inside one duct, the other duct are not touching for sure. section 2.2.4.3.1 is for three singe-core cables in trefoil. if we considered 2.2.3.2, which is a variance of the single isolated cable, how are we accounting for the mutual...

Dear all, concerning the current carrying capability of three-single core cables in trefoil in 9 way (3 x 3) duct bank and following the procedure in IEC 287 - 1 -1 and 287 - 2 - 1 when we are calculating T4 = T'4 + T"4 + T"' 4 T'4 is according to 287-2-1 2.2.7.1 T"4 is according to 287-2-1...

ok you are very correct and i am very wrong it is the temperature rise!! so it should be 50 in the nominator! now with 50 as deltatheta and taking n = 3 for all cases from one cable active till eight cables i get the following results: one cable 365A two cables 299A three cables 259A...

in 287-1 section 1.4.1.1 deltatheta "is the conductor temperature rise above the ambient temperature (K)" so in case considering the ambient as 40°C then deltatheta would be 90-40 + 273.15 = 323.15°K which leads to a higher current value! [neutral][neutral] is it possible to get a picture of...

first, i really appreciate your support. second these are the values i have for one cable case (8th cable in 3 x 3 ductbank) T1 = 0.2 K.m/W T2 = 0 (no armour) T3 = 0.109 K.m/W T'4 = 0.361 T''4 = 0.062 Te = 0.292 Tc = 0.577 T4 = 1.292 K.m/W lambda 1 = 0.1 (Assumed) lambda 2 = 0 (no armour)...

you are correct i was consdering the 50 mm as 5 mm! however still for only ONE cable in operation FK doesnt affect the calculation and i cant find my mistake! any thoughts from your side? or am I using the wrong section of the standard?

you are correct the FK was wrong: the values are: LI81, LI82, LI83 = 330 + 2 x (1000 + 80) = 2490 LI84, LI86 = 165 + 2 x (1000 + 160 + 50 + 80) = 2745 LI87, LI89 = 2 x (1000 + 160 + 50 + 160 + 50 + 80) = 3000 the 1000 mm is from ground to top of the first duct which is 75 mm from the duct bank...

Hello again, i uploaded the calculations sheets i made i hope it is possible for you to check them. I made the calculations for 300 mm.sq. with cables active in ductbank from duct 1 to duct 9 where duct 5 is always empty. i used in N for Teaerth of T'''4 as 3xno. of active cables and i used n in...

Thanks! one last question: above you indicate n = 3 and N = 9 is there any place where we will use 27? that is 9 ducts and in each duct a cable with 3 conductors.

Hello 7anoter4, thank you for youe previous assistance. the sheets you sent helped me a lot in understanding the calculations. I made the calculations and have some questions. I hope it is not a problem to ask you. 1. when i am considering non-armoured cables lambda 2 in 1.4.1.1 from 287-1-1 and...

Thanks again for your very precious reply. I will be doing some calculations and would like to consult you on them later.

Hello, is there a way according to IEC 287 to calculate the maximum capacity of a cable in a concrete duct bank while other cables are loaded equally. For example, if i have same to the above calculations 9 cables each with 150 A when all cables are operating, for 8 cable operating can i have 7...

so if i am not considering using a generator breaker, the parallel 2 x 2500 A breaker configuration is valid and shouldnt cause any operational issues with all switching operations? Energization, fault clearance, load rejection,... Thanks!