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Abstract: This paper discusses the optimal selection method of conductor economic section in agricultural transformation. Based on the traditional selection of conductor section based on the value of economic current density, an optimization scheme considering the factor of line loss rate is proposed to further save energy and improve operation reliability

key words: rural reconstruction conductor section at present, the country is carrying out rural reconstruction. The common problem in rural operation management is that the line loss is very large. One of the reasons for the problem is that the loss of conductor power is not taken into account in road construction. The general selection method of conductor section is to use the economic current density value or allowable voltage loss as the control condition, but for the rural power lines with low maximum load utilization hours, it often cannot meet the allowable power loss value. In the selection of conductor cross-section, this paper puts forward a method of selecting conductor cross-section according to the line loss rate on the basis of how to consider the problem of line loss rate, and puts forward a comprehensive selection method based on this combined with the value of economic current density, which is called J → K → s method for short. The calculation formulas are derived in the following two cases: the load on the line is concentrated and the load on the line is evenly distributed. 1 calculation when the load is concentrated at the end of the line (1) calculate the conductor section according to the allowable line loss rate: the load is concentrated at the end of the line, and the whole line adopts the same section (see Figure 1). Figure 1 load concentration at the end of the line power flow calculation figure annual loss of electric energy: a=pmtm (1) if the annual allowable line loss rate is k% Δ A allowable =k%pmtm (2) loss hours τ And the actual loss of the line calculated by the annual maximum load is: Δ A=3I2mR τ×= (P2m+Q2m)÷U2 ×τ× ( ρ L÷S) × (3) As required: Δ A≤ Δ A yes, set Δ A= Δ A yes, then: structural function 1 integrated green building materials and other advanced building materials are the development focus pmtmk% = (p2m+q2m) ÷ U2 ×τ× ( ρ L÷S) × Then s= τρ L (p2m+q2m) ÷ 10kp should strictly control the forming temperature mtmu2 (4) set qm=pmtg φ Substituting into equation (4), it becomes: S= τρ L (p2m + q2m) ÷ 10kpm manufacturing plane and mesh engineering laminate tmu2= τρ LPm(1+tg2 φ) ÷ 10kpmtmu2 (5), where τ—— Annual loss hours, H TM - annual maximum load utilization hours, H PM, QM - annual maximum active and reactive loads, kW, kvar K - allowable line loss rate of line U - average line voltage, KV ρ—— Conductor resistivity, Ω· mm2/km TG φ—— Tangent value of power factor angle at annual maximum load L - line length, KM order: sk= τρ (1+tg2 φ) ÷ 10ktmu2 (6), then s=skpml (7) (5) is the calculation formula for selecting the conductor section according to the allowable line loss rate k of the line. Obviously, s and K are inversely proportional. When u=35kv and supplemented with appropriate additives, cos φ= At 0.8, SK value is shown in Table 1. Table 1 SK value of 35kV table K SK (mm2/kw · km) tm=4000 tm=7000 12.199 × two point six eight six × 2 1.100 × one point three four three × 3 7.328 × eight point nine six zero × 4 5.499 × six point seven one six × 5 4.399 × five point three seven three × 6 3.660 × four point four seven seven × 7 3.142 × three point eight three seven × 8 2.750 × three point three five seven × When u=10kv, cos φ= At 0.8, SK value is shown in Table 2. Example 1: a 35KV line transmits the maximum load pm+jqm=1500+j1000, the line length is 50km, tm=4000h, set k%=4%, and calculate the conductor section that meets the line loss rate. The calculation process is as follows: as required: cos φ= 0.8, check the table: sk=5.499 ×， So: s=1500 × fifty × five point four nine nine ×= 41.24(mm2)。 Therefore, lgj-50 is selected as the conductor. Similarly, in the above case, if the conductor section is selected by the economic current density method: then: when k%=6%, the conductor section is calculated according to the line loss rate: s=1500 × fifty × three point six six zero ×= 27.45 (mm2) combining the above two, lgj-35 conductor is required. This example shows that the line loss rate of the conductor section selected by the economic current density method under the maximum load is larger than the generally allowed line loss rate. Table 2 SK value of 10kV table K SK (mm2/kw · km) tm=4000 tm=7000 126.948 × thirty-two point nine zero seven × 2 13.474 × sixteen point four five two × 3 8.938 × ten point nine six nine × 4 6.737 × eight point two two seven × 5 5.389 × six point five eight one × 6 4.491 × five point four eight four × 7 3.850 × four point six six nine × 8 3.368 × four point one one three × (2) Calculate according to the line loss rate when operating at economic current density: it can be seen from the above example that the line must have a corresponding line loss rate when operating at economic current density. Therefore, if the calculation formula of allowable line loss rate is determined in combination with economic current density, it can be derived from the following formula: (8) comparing formula (8) and formula (5), we can get: (9) set

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