On the Refinement of Calculations of Load Losses of Electricity in the Wires of Overhead Power Lines
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he Refinement of Calculations of Load Losses of Electricity in the Wires of Overhead Power Lines G. V. Shvedova, * and A. S. Shchepotina aNational
Research University Moscow Power Engineering Institute, Moscow, 111250 Russia *e-mail: [email protected] Received August 28, 2018; revised January 9, 2019; accepted January 23, 2019
Abstract—In this paper, we study the possibility of increasing the accuracy of calculating load losses of electricity in the wires of overhead power transmission lines with a voltage of 35–220 kV. In “traditional” calculations, some factors that determine the accuracy of loss determination are not taken into consideration. One of them is the effect of weather conditions. The need to take into account meteorological factors are noted in the normative documents. However, existing methods are complex, computationally voluminous, and require comprehensive weather information. Therefore, they cannot be used for engineering calculations. Here, we estimate the values of the correction coefficients allowing to take into account the weather conditions in the calculations and thereby reduce the error in determining the load loss of electricity in the wires of overhead power lines at a minimal amount of source data. Keywords: overhead power line, electricity losses, meteorological factors, error reduction DOI: 10.3103/S1068371220060103
A number of studies indicate the need to take into account meteorological factors when calculating load losses of electricity in the wires of overhead power lines. According to [1], losses for the calculating period can be determined by the method of operational calculations: n
ΔW =
I R i =1
2 i 20
[1 + αt (Tw i − 20)]Δti ,
(1)
where n is the number of time intervals; Ii is the effective value of the current in the power line for the i th interval, A; R20 is the specific active resistance of the wire at its temperature of 20°C, Ohm/km; αt is the temperature coefficient equal to 0.00403 for electrotechnical aluminum, 1/°С; Tw i is the wire temperature in the i th time interval, °С; and Δti is the time interval during which current load Ii and temperature tw i are taken constant. In practical calculations of load losses of electricity, the wire temperature is normally taken equal to 20°C or, in rare cases, the air temperature [1]. In this case, every 10°С difference from the real temperature increases the error in determining losses by 4%. As was shown in [2], the neglect of meteorological factors can lead to errors in the determination of wire overheating up to 50°C, which is equivalent to an error in determining active power losses of up to 20%. Therefore, weather conditions must be taken into account when calculating load losses of electricity in the wires of overhead power lines.
The temperature of the overhead power line wire depends on many factors [2]: —ambient temperature; —current density in the wire; —wind speed; —wind direction with respect to the wire; and —the intensity of solar radiation. The calculation methods taking into account these
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