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5ТЕХНИЧЕСКИЕ НАУКИ (TECHNICAL SCIENCES) УДК 620.197.5
Ismayilova G.
Associate professor of the Department Power Industry Azerbaijan State Oil and Industry University (Baku, Azerbaijan)
Mufidzade N.
Associate professor of the Department Power Industry Azerbaijan State Oil and Industry University (Baku, Azerbaijan)
ESTIMATES OF THE COEFFICIENTS OF LINEAR EQUATIONS OF CONNECTION
OF THE PARAMETERS OF STAY CURRENTS
Abstract: at research of influence of wandering currents of the electrified rail transport on underground petro- and gas pipelines, and also in calculation of accident protection devices, buildings the various characteristics connecting parameters of their modes and chains of currents. Thus, there is a problem of construction of models of communication ofparameters of system "a rail - the earth - underground construction" with parameters of a mode of the accident protection device and etc.
Keywords: distribution function, the metal constructions, wandering currents, random variable, distribution excess.
Introduction. Transportation of oil, gas, oil products through main and distribution pipelines has great technical and economic advantages compared to other modes of transport. The danger of destruction and failure of underground pipelines under the influence of stray currents is the most dangerous and destructive in its consequences. This is due to the significantly higher densities of stray currents flowing
from underground metal pipelines into the environment, as a result of which the normal and uninterrupted operation of their operation is disrupted in a very short time.
Currently, the criteria for determining the corrosion hazard are: experiments in laboratories and natural conditions, theoretical and model studies, field surveys on the routes of existing and projected pipelines.
Approach method. The accuracy of estimating the coefficients of linear coupling equations for the parameters of stray currents was studied by us using a simulation model. The dependence of the potentials of structures relatively close to the ground <pc and relative to the rails <pav on the potentials of the rails <pr and on the traction load It was built. These dependences were based on a linear structural relationship of the form [1]:
(y--q) = a(x-f), (1) where: x, y- are unobservable random variables [3]; tf ,<f - mean values of the respective observed variables.
The mean values of the parameters and their standard deviations are taken from the results of processing a large number of field measurements. The most common values of <pc, <pav, <pr It, as well as the values of their standard deviations are selected
[3].
For example, the average value of the potentials of structures relative to the rail was taken equal to tf = <pav = IV, with standard deviation^ = IV; the average value of the potentials of the rails relative to the distant earth are f = <pav = -2V, with standard deviation Sav = 0,6V.
The value of a is taken equal to two. Random x values were determined (obeying Johnson's Sv distribution law) as deviations from the mean value x:x = x + aru, where u quantile's of the Sv in Johnson distribution; accepted that or = Sav = 0,6V and aav = Sav = IV. For example,
Vr = <Pav + Gru
The y values were calculated using formula (1) preliminarily converted to the
form:
y = -q + ax — (2)
For the accepted average values of the potentials <pav, <pr and the coefficient a, expression (2) can be written in the following forms
(pav = 1 + 2(pr — 2(—2) or (pav = 2(pr + 5.
It is assumed that the distribution of errors e and 5 of the dependent and independent variables n and respectively, obeys the normal law, and their mathematical expectations are equal to zero, i.e.:
M(E) = M(8) = 0.
Variational series of values of observed random variables, i.e. deviations from a linear dependence were simulated by means of random numbers having a normalized normal distribution according to the formulas [1, 3]:
£ = a£u or S = asu, where: o£ and os - relevant error standards.
To analyze the influence of the observational error on the estimate of the slope of the linear dependence, the latter was determined for various standard errors. The error standards o£ h os are expressed in fractions of the standard aav of the measured value yav, i.e. values:
^ and ^.
&av Фар
These ratios were taken equal to 0.05; 0.1; 0.2; 0.3; 0.5, i.e. they were 5, 10, 20, 30, 50 percent of oav = 1. The obtained data were processed and estimates of the coefficient of linear dependence equations were found, which were compared with a precisely specified value equal to two [3,4].
The accuracy of the estimation of the coefficient a obviously depends on the accuracy of the estimates Sav and Sr, as well as the accuracy of the standards oav and or, increasing with the number of measurements. But, since we do not use the estimates Sav and Sr, but their exact values oav and or , an increase in the volume of production will not increase the accuracy of the estimate a. With an increase in the volume of production, only random fluctuations in the estimate take place. Comparison of variances by the Fisher criterion showed the insignificance of the difference in variances [3]:
F = 00515 = 2,91 < F(4; 0,95) = 6,39.
0,0177 v У
Conclusion. Thus, in corrosion studies of stray current fields, one has to resort to multiple measurements, observations, and subsequent statistical processing of their results.
The processing technique depends on the regularities that are characteristic of the observational results and characterize their scattering. Measurement is possible only when the dispersion of observational results reveals certain patterns. Therefore, it is necessary to make sure that the patterns take place, and the distribution of observations is statistically stable.
REFERENCES:
https://cyberleninka.ru/article/n/matematicheskiy-metod-rascheta-raspredeleniya-
tokov-korrozii-i-potentsialov-v-zazemlyayuschih-ustroystvah-tyagovyh-podstantsiy
http://physics.gov.az/PowerEng/2007/v1article/art15.pdf
А.М. Керимов. Исмайлова Г. Г.. Методы оценки параметров цепей блуждающих токов. «Проблемы энергетики»,.№3, Баку, 2011, стр. 56-63. Копьев И.Ю., Петрова Ю.Г., Гончаров A.B. Основные способы оценки эффективности электрохимической защиты обсадных колонн скважин от коррозии // Газовая промышленность. - 2012. - № 9. - С. 72-75.
