1. Why does the power line generate "voltage drop"?
The voltage drop in the power line is due to the resistance of the conductor. Because of this, so no matter adopt what kind of conductor material (copper, aluminum) can cause line voltage loss, the loss of pressure drop () is not more than 5% of the voltage itself is generally not on the line of electric drive.

2. Where do I need to consider voltage drop?
Generally speaking, when the line length is not very long, because the voltage drop is very limited, the problem of "pressure drop" can be ignored, for example, the line is only tens of meters. However, if the cable pressure drop is ignored on some of the longer power lines, the starting equipment may be too low to start the equipment after the cable is laid. Or the device can be started, but in low voltage running state, the time is long damaged equipment.
Longer power lines need to consider pressure drop. The so-called "long line" generally refers to the cable line is more than 500 meters. Pressure drop should also be considered for situations requiring high voltage accuracy.

3. How to calculate the voltage drop of the power line?
1). Overhead line voltage drop.
According to the rules and regulations; The 10kv class line generally does not exceed the radius of 15km, including the length of the branch line.
At the same time the power supply quality, the voltage drop is plus or minus 7%.
Example; U = 10 kv L = 15000 m S = LGJ - 15000 was 0.0315 mm aluminium resistivity. M COS phi = 0.8, P = 1150 kw Q = 863 kvar 10 kv reactance X = 0.35 Ω. Km = 15 = 5.25 Ω o R = 0.35 * rho * L/S = 0.0315 * Ω 15000/240 = 1.97
According to the voltage loss formula;
Delta U R = P * * X + Q/U (kv) + 863 * 1150 * 1.97 = 5.25/10 = 2266 + 4731/10 = 4731/10 = 699.7 v = w/w % U * = 7% (699.7/10000) * 100 = 100
10kv line radius 15km choose 240mm2 aluminum wire overhead laying, theory COS (s) =0.8, terminal voltage drop control 7%, can carry load 1150kw.

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