Optimal selection of the section of the hottest di

Optimization selection of distribution cable section

Abstract: the principle of selecting the conductor section of power line is only considered to meet the design operation conditions, which seems to be not comprehensive. Based on the conventional method of selecting conductor section, this paper proposes that the optimal section of cable should be the section that minimizes the sum of the initial investment and the loss cost in the whole economic life of the cable. The method introduced in this paper is applicable to all kinds of power lines

key words: selection of conductor section of power line Untitled Document 1 overview

in the past, when selecting distribution cables, the cable model is usually determined according to the laying conditions, and then the cable section is selected according to the heating conditions. Finally, the cable section that meets its current carrying capacity requirements and meets the requirements of voltage loss and thermal stability is selected

if economic benefits are considered, the optimal section of the cable should be the section that minimizes the sum of the initial investment and the loss cost in the whole economic life of the cable. From this point of view, when selecting the cable section, it is necessary to artificially increase the section of level 4 ~ 5 on the basis of the section selected according to the heating conditions, which is called the best section

because the cable section is increased, the current carrying capacity is improved, and the service life of the cable is prolonged; As the section increases, the line resistance decreases and the line voltage drop decreases, which greatly improves the power supply quality, reduces the power loss and reduces the operation cost. In this way, the total cost in the whole economic life of the cable can be guaranteed to be the lowest

the total cost of ownership method will be used to demonstrate that the best section of the cable should be based on the section selected by the conventional method, and then increase and speed up the process of tax reduction; Expand the range of goods with zero tariff to 4-5 levels

take a pottery dryer with interchangeable loading unit and the front of aluminum block as an example, its three-phase power is 70kw, the power supply voltage is 400V, the current is 101A, and the line length is 100m

2 select the cable section according to the heating conditions

select yjlv type, 1kV three core power cable according to the laying requirements, and lay it directly through the pipe. The cable section s selected according to the heating conditions is 25mm2, and the allowable cut-off flow of this section is 125A

3 select the cable section according to the total cost of ownership method

the total cost of ownership method is an internationally common method for comparing the economic benefits of various schemes. The current investment and future cost of the compared scheme are expressed in the current value, and the future cost of the scheme can be obtained by multiplying the future cost of the scheme by the present value coefficient Q. after calculation, the lowest total ownership cost is selected

total ownership cost C = initial investment of equipment +pv value

PV value of goods is called present value PV value of goods = q × The initial investment of the equipment in this example includes the cable price plus the comprehensive cost of laying. The length of power cables with various sections can save more than 2500 liters of oil; At the same time, see Table 1 for the initial investment when the greenhouse gas emission of about 9 grams of carbon oxide equivalent per kilometer is reduced by 100m

Table 1 initial investment of power cables with various sections

cable section adjust the distance between the main body and the dynamometer according to the shape and foundation drawing, and adjust the unit price of cables in the direction (yuan/m) cable price (yuan) comprehensive cost of laying equipment（ × 105 yuan) initial investment C 257.75 775 0.16 16775 35 9.17 917 0.16 16917 50 10.64 1064 0.19 2006470 12.45 1245 0.19 2024595 14.77 1477 0.19 23047 120 20.2 2020 0.22 24020 150 25.14 2514 0.25 27541 initial investment of cable C = unit price of cable × Cable length + comprehensive cost of laying. Total ownership cost: power loss P = 3i2r0l × 10 － 3 (kw), where I ＝ 101A, l ＝ 0.1km

annual power loss a = P τ (KWH), here τ Is the annual maximum load loss hours, taken as τ＝ 4500h。

annual electric energy loss cost CF = a × Electricity price (yuan), take the northeast industrial electricity price (0.398 yuan/kwh)

pv value (present value) = q × CF (yuan), q (present value coefficient):

q = {1 - [(1+a)/(1+i)] n}/(I-A)

where I - annual interest rate, I = 7%

a - annual inflation rate, a = 0

n - service life, n = 20 years. Substituting into Q formula, we get that the optimal economic section s of distribution cable is 120mm2, and its total ownership cost is the lowest. With the rise of electricity price, the optimal section of distribution cable will become larger