Power cable core section of economic optimization standard fraud can be Ⅲ, on the basis of comprehensive consideration of the cable loss during the initial investment and operation cost, the economic selection for cable method to ((IEC287-3-2/1995, lowest total cost for engineering construction economy target, thus has been widely applied [2-0. "[8] economic current density of low voltage cable in a more in-depth research, given the economic selection of related data in 2000, for convenience, the economic selection hereinafter referred to as the original data.
In recent years, the rising price of copper leads to the doubling of the cost of copper core cable, which makes the original economic selection data no longer applicable.
In order to ensure the accuracy of current economic selection of cable section, it is necessary to update the economic selection data by using the current cost of various types of cables.
However, it is quite difficult to collect relatively complete cable material cost and installation cost, and the cable reference price given by the relevant national administrative authorities lags behind the actual demand. For example, the research report of Literature [8] is based on the Budget Price of Raw Material L for Electric Power Construction Equipment in 1998.
Due to the use of traditional method a lot of work, the economic selection of cable data update very slow, is proposed in this paper using recent copper cable estimate the approximate method of new materials and on the basis of updated economic current density of the simplified method, can be obtained under the condition of the copper price volatility fast accurately the economic selection of data, to a great extent, simplify the complex process of the use of traditional method for data update.
Updated approximation of economic current density with new cable material charges
According to IEC287-3-2/1995 standard economic model selection principle of cable economic current density expression resistance, pseudo-economic current density, A/ RAM2, is the maximum load current: S.
Is the economic section, mm2;
A is the variable part of the cost, yuan /·m);
Coefficient of equivalent loss, Yuan/L [W;P∞ is the DC resistivity of the cable at ℃, Q·m;B is a function of the cable neighborhood effect coefficient y and skin effect coefficient y8, B=I+Y, +Y;^0 Strider temperature coefficient of the cable OR20 and the average operating temperature as a function, K=I+ OT20 (0M_20), the unit of m is ℃.
It can be seen that direction and/ten thousand are proportional. The change of initial cable investment will cause the change of variable part A of the cost, and then affect the value of economic current density.
According to IEC287-3-2/1995 standard economic selection principle, the initial investment of the cable section of the linear function usesesimals, S for the cable section, mm2;
C is the fixed part of the cable cost, yuan /m;
L is the cable length, m.
Can express initial investment CI is the form of sum of material cost OU and installation cost.
Because of the same type cable all levels of cross section of A value with the same value, therefore, according to the type (2), using the difference between the two adjacent nominal cross section of the initial investment of the cable can be obtained by A, considering the cable installation in the cable initial investment proportion of smaller assumes that the raw materials of the cable for cic, as A result of fluctuations in copper prices of new materials for c 'k, the cost of raw materials increase ratio k = c', jc.
, the new value A 'of the variable part A of the cable cost, and the new economic current density can be obtained. The error analysis of this simplified process is shown in Table 1.
The original values in the table are taken from literature, A precise update value of 2006 data, cable materials in the process of updating reference ((construction engineering price information, shenzhen city, guangdong province, 2006 installation reference (the general norm of municipal engineering in guangdong province in 2006, and the electric power construction engineering budget quota - electrical equipment installation project "2001 revision to estimate the unit price.
It has been verified that when the fluctuation of A value is no more than 20%, the error caused by... is no more than 10%, and the accuracy of economic selection is not affected.
From the analysis results in Table 1, it can be seen that the errors caused by this approximate method are all within the allowable range and meet the accuracy requirements of economical selection of cable section.
Approximate method for estimating material cost of copper core cable by copper price
Since it is very difficult to collect the complete material cost of all types of cables, considering that the cost of copper material accounts for a large proportion in the cost of cables, we try to approximate the price of cables by using the copper price.
Divide the cable material cost G into parts directly related to the copper price.
And the part civ unrelated to the copper price, denotes the specific gravity coefficient of the part related to the copper price.
It can be approximately assumed that G fluctuates linearly with the copper price, while CIV stays constant.
Institute of assumptions based on the starting year of cable materials for rockwell, copper related parts as per thousand, copper related proportion coefficient for ao, the first n years cost of raw materials for the Cia. I copper part related to C, n and the initial years, the ratio of copper to K if known starting materials C hoe, starting in copper prices w relevant part proportion coefficient and copper growth multiples of ink, can be the cost of raw materials, n years, so as long as can be determined tXo of various types of cable can be based on the study of copper to estimate the new cable materials.
Research work of this article to as starting in 2000, with years of relevant data as the original data, using the type to determine the coefficient of %, use the each type of the average value of five (5) % of the cable as the starting year of copper relevant part of the weight coefficient, 0 c0 values of different types of cable to simplify updating method for the rapid growth of copper, starting from year to year) based on the economic selection of related parameters and data, using the current copper price and the w value can be obtained quickly in table 2 applies to the current situation of economic current density data.
The specific steps are as follows:
Based on the material cost of the corresponding cable in the starting year (2000), the ratio of the current copper price to the starting year copper price and the parameters of the corresponding cable, the current material cost of the cable is estimated according to Equation (10).
Using the estimated cable material cost and the corresponding cable material cost of the starting year, the material cost growth factor K is calculated.
According to Equation (6), the new economic current density Jn is calculated by using the material cost growth multiple K and the economic current density data of the starting year.
4. Accuracy analysis of simplified update method
The simplified updating method of economic model selection data is verified by using the relevant data in 2006, that is, the results obtained by the simplified updating method are compared with those obtained by the precise updating method.
By adopting the method of accurate updated economic current density, cable materials reference ((construction engineering price information, shenzhen city, guangdong province, in 2006, the installation reference ((the general norm of municipal engineering in guangdong province in 2006 and the electric power construction engineering budget quota - electrical equipment installation project "2001 revision to estimate unit price, other related parameters are the same as the literature [8].
In the calculation process, the electricity price takes the annual electricity price of the high electricity price area in China.
According to the sensitivity analysis conclusion of economic current density in literature [8], the error of economic current density obtained by the simplified update method is less than 10%, which can meet the accuracy and economy of economic selection of conductor section.
5 conclusion
In view of the need of updating the economic selection data of copper core cable caused by the fluctuation of copper price in the world and the problems of the complicated updating process and the difficulty of data collection existing in the traditional methods, a simplified method of updating the economic selection data of copper core cable based on copper price was proposed, and its accuracy was verified.
The results show that the updating process of this method is simple, the updating data can meet the accuracy of economic selection of cable section, and the purpose of accelerating the updating process of economic selection data of cable section is realized.
In this paper, the relevant data in literature [8] are taken as the original data, so only six types of cables involved are analyzed for example, in order to prove the superiority and practicability of the proposed simplified method.
The update of economic selection data of other types of cables can be carried out by referring to the simplified method proposed in this paper. The analysis of calculation examples is not given in this paper.