CN115795889A - Power transmission line loss optimization calculation method based on multi-parameter correction - Google Patents
Power transmission line loss optimization calculation method based on multi-parameter correction Download PDFInfo
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Abstract
A transmission line route loss optimization calculation method based on multi-parameter correction comprises the following steps: s1, correcting resistance, reactance and susceptance in an overhead transmission line model according to the length of the transmission line; s2, correcting the resistance loss of the power transmission line under the influence of temperature; correcting corona loss under various weathers; s3, constructing a theoretical line loss correction model; and S4, fitting the theoretical line loss and the statistical line loss to construct a comprehensive line loss rate calculation model. According to the invention, on the premise of considering various factors, the resistance loss and the corona loss of the wire are corrected, the corrected loss is added to the original line loss, and a new theoretical line loss calculation model is fitted, so that the model considers more factors than the traditional method, the calculation result is more reliable, the accuracy of the line loss rate can be improved, the high-voltage electric quantity settlement of the transmission line is more fair, and the coordination and the high-efficiency operation of a power grid are ensured.
Description
Technical Field
The invention relates to the technical field of line loss analysis of an extra-high voltage distribution network, in particular to a multi-parameter correction-based line loss optimization calculation method for a transmission line, which is mainly suitable for improving the accuracy of a line loss rate.
Background
The line loss rate is an important economic and technical index for inspecting the power grid and the power industry, can practically reflect the management level of the power grid operation by the power departments in China, and the lean line loss calculation is beneficial to the planning and production feasibility management of the power grid by the related departments. Furthermore, the trading, pricing and settlement of electricity in the electricity market also depends on the calculation of line loss and line loss rate. Therefore, it is very urgent to find a lean comprehensive line loss calculation model which can reduce errors and correct theoretical line loss and statistical line loss simultaneously.
Currently, the methods used are the rms current method, the average current method and the maximum current method. The root mean square current method has the advantages of less parameter requirements, simpler and more convenient calculation and high coincidence degree of the obtained data and the actual data; but the method has the defects of small application range and good effect only on the conventional wiring mode, and the load curve and the load node power factor obtained by the method are greatly different from the actual load curve and load node power factor, so the load node current obtained by directly carrying out algebraic calculation by using the method cannot be directly used as the root mean square current. The average current method adopts electric quantity which is easy to obtain in actual production as a parameter, so that a more ideal calculation result can be obtained; the disadvantage is that the shape factor is difficult to calculate, and the result of the value has a certain influence on the calculation accuracy. The maximum current method is a loss factor method, which is applied on the premise of an equivalent relation between the maximum current and the root-mean-square current, and the loss calculation value finally obtained by the maximum current method is larger, so that the result is perfected by using a correction coefficient smaller than 1, and the authenticity is improved; the maximum current method has the defects that the accuracy of a final result cannot be guaranteed only by collecting the maximum current and the average current in a certain period during calculation, so that the calculation method is only suitable for being used in planning and designing links of a power distribution network, and other methods are required to be selected for loss reduction countermeasures and line loss calculation in the operation period of a power system.
Disclosure of Invention
The invention aims to overcome the defects and problems of low accuracy in the prior art, and provides a high-accuracy multi-parameter correction-based optimal calculation method for line loss of a transmission line.
In order to achieve the above purpose, the technical solution of the invention is as follows: a transmission line route loss optimization calculation method based on multi-parameter modification comprises the following steps:
s1, correcting resistance, reactance and susceptance in an overhead power transmission line model according to the length of the power transmission line;
s2, correcting the resistance loss of the power transmission line under the influence of temperature; correcting corona loss under various weathers;
s3, constructing a theoretical line loss correction model;
and S4, fitting the theoretical line loss and the statistical line loss to construct a comprehensive line loss rate calculation model.
In step S1, the calculation formula of the resistance R of each phase of wire of the equivalent circuit is:
in the formula, r 0 Is the unit resistance of the wire, rho is the resistivity of the wire, l is the length of the wire, S is the cross-sectional area of the wire, N is ci The number of splits of each phase of conductor;
the reactance X of the equivalent circuit is calculated by the formula:
in the formula, x 0 Reactance per unit length of transmission line, omega power frequency angular velocity, L 1 Is the inductance value of unit inductor, beta is the geometric mean distance of the conducting wire, r d Is the wire radius;
the calculation formula of the susceptance B of the equivalent line is as follows:
in the formula, b 0 Is the transmission line unit length susceptance, C is the capacitance value of the unit capacitor;
when the length l of the lead meets the condition that l is more than or equal to 500km and less than or equal to 1000km, correcting a mathematical calculation formula of a resistor R, a reactor X and a susceptance B, wherein the correction coefficient is as follows:
in the formula eta r For correcting the coefficient of resistance, eta x Is a reactance correction coefficient, eta b Is the susceptance correction factor.
In step S2, the calculation formula of the resistance loss of the equivalent transmission line is:
where Δ a is the resistive loss of the equivalent transmission line, T is the operating time, i (T) is the instantaneous value of the current through the wire, and R is the resistance of the wire;
the formula for correcting the resistance loss is as follows:
ΔE′ L ＝k w ×ΔE L
in the formula,. DELTA.E' L For temperature compensated line resistive losses, k w For temperature rise compensation factor, Δ E L For line power loss before temperature compensation, R i (20) Is the resistance value of the i-th section of the line per unit length at a temperature of 20℃, L i Is the ith wire length, I pi To rated current value, I if Is the root mean square current value, l i Length of i-th type wire, N ci Number of splits per phase conductor, T te Is ambient temperature.
In step S2, when the resistance loss is corrected, the resistance value of the resistor itself is corrected, and the correction formula is:
R 0 ＝k θ R 20
r 0 ＝k θ r 20
in the formula, R 0 Is the actual resistance of the wire, r 0 Is a unit resistance of a wire, k θ For resistance temperature correction coefficient, R 20 Is the resistance value of the wire at a temperature of 20 ℃, r 20 Is the unit resistance of the wire at a temperature of 20 ℃, I rms Root mean square current value, N ci The number of splits of each phase of the conductor, k is the temperature coefficient of the conductor, t is the average temperature of the selected representative day, and I is the temperature of the conductor at 20 DEG CContinuous current value to target temperature.
In step S2, the formula for calculating corona loss is:
in the formula, P 1 、P 2 、P 3 Corona loss per unit length, R, for good weather, rainy weather, and rime weather, respectively n To split the radius of the conductor, E u Maximum field strength at the surface of the wire, E 0 Critical electric field strength;
surface field strength E of mesophase M The calculation formula is as follows:
wherein v is a coefficient for calculating the maximum electric field intensity on the surface of the divided conductor, C av Is the average capacitance, N ci The number of splits of each phase conductor, r is the radius of the sub-conductor, V is the actual operating voltage, D 1 Is a constant;
surface field intensity E of side phase M (B) The calculation formula is as follows:
in the formula, D 2 Is a constant number, D 2 ＝D 1 ＝D；
Replacing the running voltage of the transmission line with the average voltage of the head end and the tail end of the transmission line, wherein the weighted average value of the one-year corona loss is as follows:
in the formula, V i And V j Respectively head end voltage and tail end voltage of the transmission line, T 1 Duration of good weather in one year, T 2 Duration of rainy weather in a year, T 3 The duration of rime weather in one year; a. The 1 、A 2 、A 3 Are all the parameters of the replacement, and,
the corona loss correction formula is:
P′ i ＝μP i
of formula (II) to (III)' i For corrected corona loss, P i Is a weighted average of the corona losses, mu is the corona correction factor, f is the voltage frequency, r 1 Is the wire radius; beta is the geometric mean distance of the lead,
R b is the radius of the cylinder where the wire is equivalent to the reference potential.
In step S3, the theoretical line loss calculation formula is:
ΔP＝P 1 -P 2
wherein Δ P is the theoretical line loss, P 1 For active power at the head end of the transmission line, P 2 Active power is the tail end of the transmission line;
the corrected theoretical line loss is:
ΔP′＝ΔP+μP i +k w ΔE L
wherein Δ P' is the corrected theoretical line loss, μ P i For corrected corona loss, k w ΔW L Is the corrected resistive loss.
In step S4, dividing the theoretical line loss into variable loss and fixed loss;
variable loss P R The calculation formula is as follows:
in the formula I w The current is the current flowing through the line resistor in a working state, R is the line resistor, and U is the voltage on the resistor;
fixed loss Δ P C The calculation formula is as follows:
ΔP C ＝N
in the formula, N is a constant;
the theoretical line loss rate k 1 Comprises the following steps:
statistical line loss rate k 2 The calculation formula is as follows:
wherein Δ S is the line loss power, S 1 For supplying power to the beginning of the gateway, S 2 Sending electric quantity to the tail end of the gateway;
the comprehensive line loss rate χ calculation model is as follows:
compared with the prior art, the invention has the beneficial effects that:
according to the multi-parameter correction-based optimal calculation method for the line loss of the power transmission line, on the premise that various factors are considered, the resistance loss and the corona loss of the wire are corrected, the corrected loss is added to the original line loss, and the original line loss is fitted into a new theoretical line loss calculation model. Therefore, the invention can improve the accuracy of the line loss rate, make the settlement of the high-voltage electric quantity of the transmission line fairer and ensure the coordination and the high-efficiency operation of the power grid.
Drawings
Fig. 1 is a flow chart of a transmission line loss optimization calculation method based on multi-parameter modification according to the present invention.
Fig. 2 is a schematic diagram of an overhead transmission line model according to the present invention.
Fig. 3 is a graph of line loss rate versus power in accordance with the present invention.
Detailed Description
The invention is described in further detail below with reference to the figures and the detailed description of the invention.
Referring to fig. 1, a power transmission line loss optimization calculation method based on multi-parameter modification includes the following steps:
s1, constructing an overhead transmission line model as shown in a figure 2; correcting resistance, reactance and susceptance in the overhead transmission line model according to the length of the transmission line;
the resistance R of each phase of wire of the equivalent circuit is calculated by the formula:
in the formula, r 0 Is the unit resistance of the wire, rho is the resistivity of the wire, l is the length of the wire, S is the cross-sectional area of the wire, N is ci The number of splits of each phase conductor;
the reactance X of the equivalent circuit is calculated by the formula:
in the formula, x 0 Reactance per unit length of transmission line, omega power frequency angular velocity, L 1 Is the inductance of the unit inductor, beta is the geometric mean distance of the conductive lines, r d Is the wire radius;
the calculation formula of the susceptance B of the equivalent line is as follows:
in the formula, b 0 Is the unit length susceptance of the transmission line, and C is the capacitance value of the unit capacitor;
when the length l of the lead meets the condition that l is more than or equal to 500km and less than or equal to 1000km, correcting a mathematical calculation formula of a resistor R, a reactor X and a susceptance B, wherein the correction coefficient is as follows:
in the formula eta r Is a resistance correction coefficient, η x Is a reactance correction coefficient, η b Is the susceptance correction factor;
the resistance R, the reactance X and the susceptance B are respectively multiplied by a correction coefficient eta r 、η x 、η b Obtaining corrected line parameters;
s2, correcting the resistance loss of the power transmission line under the influence of temperature; correcting corona loss under various weathers;
because the internal characteristics of the conductor can change along with the change of the temperature, the resistivity can also change along with the change of the internal characteristics, and meanwhile, the temperature of the working environment of the conductor can also influence the heat dissipation speed of the conductor, so the influence of the temperature on the conductor is not negligible;
the calculation formula of the resistance loss of the equivalent transmission line is as follows:
in the formula, Δ a is the resistance loss of the equivalent transmission line, T is the operation time, i (T) is the instantaneous value of the current passing through the wire, and R is the resistance of the wire;
temperature compensation is that the calculation result of the electric energy loss of the resistor is multiplied by a temperature rise compensation coefficient, so that the resistance loss is corrected, and the calculation formula is as follows:
ΔE′ L ＝k w ΔE L
in the formula,. DELTA.E' L For the line resistance loss after temperature compensation, k w For temperature rise compensation factor, Δ E L For line power loss before temperature compensation, R i (20) Is the resistance value of the i-th section of the line per unit length at a temperature of 20℃, L i Is the ith wire length, I pi To rated current value, I if Root mean square current value, I i Length of i-th type wire, N ci Number of splits, T, of conductor per phase te Is ambient temperature;
in the calculation process, the temperature of the wire can be increased by the current flowing around the wire, the air temperature can also affect the wire, and further the accuracy of resistance loss calculation is affected, so on the basis of correcting the whole resistance loss, the resistance value of the resistor is required to be corrected, and the result is more reliable; the correction formula is as follows:
R 0 ＝k θ R 20
r 0 ＝k θ r 20
in the formula, R 0 Is the actual resistance of the wire, r 0 Is a unit resistance of a wire, k θ For resistance temperature correction coefficient, R 20 Is the resistance value of the wire at a temperature of 20 ℃, r 20 Is the unit resistance of the wire at a temperature of 20 ℃, I rms Root mean square current value, N ci The splitting number of each phase of the lead, k is the temperature coefficient of the lead, t is the average temperature of a selected representative day, and I is the continuous current value when the lead reaches the target temperature at the temperature of 20 ℃;
generally, when a power transmission line with a voltage level of 110kV or more is calculated, the corona loss is small, so that the corona loss can be reduced to be within the theoretical line loss; the corona loss of the power transmission line with the voltage class of 110 kV-330 kV is relatively fuzzy, so that the estimation can be carried out according to 0.5% -2.0% of the active loss of the wire, a small value is taken in good weather, and a large value is taken in ice and snow weather and rime weather; the corona loss calculation formula on the unit length of the transmission line with the voltage class of 500 kV-1000 kV is as follows:
in the formula, P 1 、P 2 、P 3 Corona loss per unit length, R, for good weather, rainy weather and rime weather, respectively n Is a radius of a divided conductor, E u Maximum field strength at the surface of the wire, E 0 Critical electric field strength;
surface field intensity E of the mesophase M The calculation formula is as follows:
wherein v is a coefficient for calculating the maximum electric field intensity on the surface of the divided conductor, C av Is the average capacitance, N ci The number of splits per phase conductor, r is the radius of the sub-conductor, V is the actual operating voltage, D 1 Is a constant;
surface field intensity E of side-to-side phase M (B) The calculation formula is as follows:
in the formula, D 2 Is constant due to D 1 Ratio of only D 2 About 6% greater, so D is considered to be approximate 2 ＝D 1 ＝D；
Replacing the operating voltage of the transmission line with the average voltage of the head end and the tail end of the transmission line, wherein the weighted average value of the one-year corona loss is as follows:
in the formula，V i And V j Respectively, the head end voltage and the tail end voltage of the transmission line, T 1 Duration of good weather in one year, T 2 Duration of rainy weather in a year, T 3 The duration of rime weather in one year; a. The 1 、A 2 、A 3 Are all the parameters of the replacement, and,
the corona loss correction formula is:
P′ i ＝μP i
of formula (II) to (III)' i For corrected corona loss, P i Is a weighted average of corona losses, mu is the corona correction factor, f is the voltage frequency, r 1 Is the wire radius; beta is the geometric even distance of the lead,
R b a radius of a cylinder equivalent to a reference potential for the wire;
s3, constructing a theoretical line loss correction model;
by combining the parameter correction results of fig. 2 and step S1, the reactor loss, the transmission line loss, and the reactive power consumption are calculated, and the following results can be obtained:
wherein,
is total power transmission quantity of the power transmission line, S' 2 Delta Q is reactive power consumption, delta S is the power line type equivalent output power ZL Is the loss of the transmission line, Δ S A Loss for the reactor; and the active power P of the head end of the transmission line can be calculated according to the complex power 1 (ii) a According to the end of the transmission lineElectric power supply quantity S 2 And the active power P at the tail end of the transmission line can also be obtained 2 ；
The theoretical line loss calculation formula is as follows:
ΔP＝P 1 -P 2
wherein Δ P is the theoretical line loss, P 1 For active power at the head end of the transmission line, P 2 Active power is the tail end of the transmission line;
the line loss calculation after parameter correction still does not consider the influence of resistance loss and corona loss. The above contents analyze the influence of temperature on resistance and corona loss, and calculate the correction coefficients of resistance loss and corona loss. Because the line loss is roughly calculated by subtracting the head end power and the tail end power at present, the influence of temperature on the resistance loss of a wire and the influence of field intensity and different weather on corona loss are ignored, the calculation result is inaccurate, and the difference between the calculation result and the actual value is large. Therefore, the invention provides a new theoretical line loss calculation model which corrects the resistance loss and the corona loss of the wire under the premise of considering various factors, adds the corrected loss into the original line loss, and has the following calculation formula, wherein the model considers more factors than the traditional method and has more reliable calculation results;
the corrected theoretical line loss is:
ΔP′＝ΔP+μP i +k w ΔE L
wherein Δ P' is the corrected theoretical line loss, μ P i For corrected corona loss, k w ΔE L The resistance of the corrected resistance loss is R 0 ＝k θ R 20 ；
S4, fitting the theoretical line loss and the statistical line loss to construct a comprehensive line loss rate calculation model;
considering that the influence of temperature, humidity and some small load changes on the line loss can be ignored when the theoretical line loss is calculated, calculating the line loss rate from the theoretical line loss calculation model alone can cause the calculation result to be inaccurate. Only considering the statistical line loss, and not considering the theoretical line loss, the line loss rate and the true value are deviated due to the gateway metering error, so the invention fits the theoretical line loss and the statistical line loss together and provides a novel comprehensive line loss calculation model, thereby correcting the existing single line loss rate calculation scheme and reducing the error;
dividing theoretical line loss into variable loss and fixed loss;
variable loss P R The calculation formula is as follows:
in the formula I w The current flowing through the line resistor in the working state, R is the line resistor, and U is the voltage on the resistor;
fixed loss Δ P C The calculation formula is as follows:
ΔP C ＝N
in the formula, N is a constant;
the theoretical line loss rate k 1 Comprises the following steps:
statistical line loss rate k 2 The calculation formula is as follows:
wherein Δ S is the line loss, S 1 For supplying power to the beginning of the gateway, S 2 Supplying power to the tail end of the gateway;
the comprehensive line loss rate χ calculation model is as follows:
because certain errors exist in the theoretical line loss rate and the statistical line loss rate, and the error generation reasons are different, the theoretical line loss rate and the statistical line loss rate can be combined to construct a comprehensive line loss rate, the comprehensive line loss error can be corrected mutually, and the influence of the change of factors such as temperature, corona loss and power on the line loss rate can be expressed more accurately.
After the proportion of different weather in one year is selected, resistance loss and corona loss are solved according to the splitting number of the conductor, the maximum field intensity coefficient of the surface, the radius of the sub-conductor and the actual operating voltage, and a relation between the theoretical line loss rate and the power can be obtained by adding the fixed loss of the transformer and the overhead line. Selecting statistical line loss data measured at the power transmission line gate within one year, solving a relational expression of statistical line loss rate and power, fitting the statistical line loss data and the relational expression into a comprehensive line loss rate when different powers are selected, and obtaining points according to the comprehensive line loss rate
The line loss rate is plotted against the power.
The trans-regional power transmission of a province is frequent, the comprehensive line loss rate is used for converting the electric quantity of a gateway of a power grid of a transmitting end region to a power grid of a receiving end region, so that the province is selected to research the comprehensive line loss rate, the conventional single line loss rate is recorded as a fixed value of 1.3%, and the comprehensive line loss rate is corrected by using the comprehensive line loss rate calculation method provided by the invention.
The equivalent resistance of the line is R =5.67 omega, wherein the corona loss is influenced by temperature and weather conditions, so the proportion of weather of rain, fog and ice is R =5.67 omega
The coefficient of the maximum electric field intensity on the surface of the split conductor is 0.6, the average capacitance is 5F, the split number is 4, the radius of the sub-conductor is 0.6mm, the actual operating voltage is 550KV, and the theoretical line loss rate is obtained by substituting into a theoretical line loss rate calculation formula according to the fact that the corrected corona loss is 8.72MW, and the sum of the fixed losses of the overhead line and the transformer is 13.67 MW;
selecting statistical line loss data measured by the transmission line gate within one year, and obtaining a statistical line loss rate according to a proposed statistical line loss rate calculation formula;
for the theoretical line loss rate and the statistical line loss rate, points under different powers are respectively taken(P i ，k 1i ) And (S) i ，k 2i ) Taking points of the corrected comprehensive line loss rate of the two line loss rates
The power taken is as shown in Table 1;
TABLE 1 relationship between theoretical line loss rate, statistical line loss rate, comprehensive line loss rate and power
| Power (MW) | Theoretical line loss rate% | The statistical line loss rate% | Comprehensive line |
| 450 | 2.32 | 2.73 | 2.64 |
| 750 | 2.03 | 2.26 | 2.13 |
| 1050 | 1.43 | 1.87 | 1.67 |
| 1350 | 1.09 | 1.56 | 1.32 |
| 1750 | 1.13 | 1.76 | 1.43 |
| 2250 | 1.23 | 1.99 | 1.56 |
| 2750 | 1.65 | 2.45 | 1.97 |
| 3250 | 1.86 | 2.98 | 2.21 |
| 3750 | 2.02 | 3.31 | 2.32 |
The function image of the theoretical line loss rate, the statistical line loss rate variation curve with power and the correction curve is shown in fig. 3. Therefore, the image of the correction curve is positioned between the function images expressed by the first two, so that theoretical factors and actual factors are considered comprehensively, and errors are reduced by mutual correction.
The invention provides a corrected theoretical line loss calculation model aiming at correcting the influences of the existing theoretical line loss influence factors such as temperature, weather and humidity on resistance loss and corona loss. According to the influence factors of the power on the theoretical line loss and the statistical line loss, a comprehensive line loss rate calculation model is established, so that the theoretical line loss and the statistical line loss can be fully integrated and corrected mutually, and errors caused by adopting a single line loss calculation method are avoided. When the line loss model provided by the invention is applied to an actual transmission line, the following can be seen: the comprehensive line loss rate calculation results of the model under different powers are closer to the actual values, the comprehensive line loss rate is 1.32% when the flowing power on the traditional 1000kV extra-high voltage line is 1350MW, and the precision is improved by 17.7% compared with the theoretical line loss rate; compared with the statistical line loss precision, the line loss precision is improved by 18.5 percent and is closer to the actual line loss rate of the project at the moment by 1.3 percent, so that the high-voltage electric quantity settlement of the transmission line is fairer. Therefore, the comprehensive line loss rate calculation model provided by the invention has strong persuasion, high accuracy and stronger practical significance.
Claims (7)
1. A transmission line route loss optimization calculation method based on multi-parameter correction is characterized by comprising the following steps:
s1, correcting resistance, reactance and susceptance in an overhead power transmission line model according to the length of the power transmission line;
s2, correcting the resistance loss of the power transmission line under the influence of temperature; correcting corona loss under various weathers;
s3, constructing a theoretical line loss correction model;
and S4, fitting the theoretical line loss and the statistical line loss to construct a comprehensive line loss rate calculation model.
2. The transmission line loss optimization calculation method based on multi-parameter modification according to claim 1, characterized in that:
in step S1, the calculation formula of the resistance R of each phase of the wire of the equivalent circuit is:
in the formula, r 0 Is the unit resistance of the wire, rho is the resistivity of the wire, l is the length of the wire, S is the cross-sectional area of the wire, N ci The number of splits of each phase of conductor;
the reactance X of the equivalent circuit is calculated by the formula:
in the formula, x 0 Reactance per unit length of transmission line, ω angular velocity at power frequency, L 1 Is the inductance of the unit inductor, beta is the geometric mean distance of the conductive lines, r d Is the wire radius;
the calculation formula of the susceptance B of the equivalent line is as follows:
in the formula, b 0 Is the transmission line unit length susceptance, C is the capacitance value of the unit capacitor;
when the length l of the lead meets the condition that l is more than or equal to 500km and less than or equal to 1000km, correcting a mathematical calculation formula of a resistor R, a reactor X and a susceptance B, wherein the correction coefficient is as follows:
in the formula eta r Is a resistance correction coefficient, η x Is a reactance correction coefficient, eta b Is the susceptance correction factor.
3. The transmission line loss optimization calculation method based on multi-parameter modification according to claim 2, characterized in that:
in step S2, the calculation formula of the resistance loss of the equivalent transmission line is:
where Δ a is the resistive loss of the equivalent transmission line, T is the operating time, i (T) is the instantaneous value of the current through the wire, and R is the resistance of the wire;
the formula for correcting the resistance loss is as follows:
ΔE′ L ＝k w ×ΔE L
in the formula,. DELTA.E' L For temperature compensated line resistive losses, k w For temperature rise compensation factor, Δ E L For line power loss before temperature compensation, R i (20) Is the resistance value of the i-th section of the line per unit length at a temperature of 20 ℃, L i Is the ith wire length, I pi To rated current value, I if Is the root mean square current value, l i Length of i-th type wire, N ci Number of splits per phase conductor, T te Is ambient temperature.
4. The transmission line loss optimization calculation method based on multi-parameter modification according to claim 3, characterized in that:
in step S2, when the resistance loss is corrected, the resistance value of the resistor itself is corrected, and the correction formula is:
R 0 ＝k θ R 20
r 0 ＝k θ r 20
in the formula, R 0 Is the actual resistance of the wire, r 0 Is a unit resistance of a wire, k θ For resistance temperature correction coefficient, R 20 Is the resistance value of the wire at a temperature of 20 ℃, r 20 Is the unit resistance of the wire at a temperature of 20 ℃,I rms is root mean square current value, N ci And k is the splitting number of each phase of the conductor, k is the temperature coefficient of the conductor, t is the average temperature of a selected representative day, and I is the continuous current value when the conductor reaches the target temperature at the temperature of 20 ℃.
5. The transmission line loss optimization calculation method based on multi-parameter modification according to claim 1, characterized in that:
in step S2, the formula for calculating corona loss is:
in the formula, P 1 、P 2 、P 3 Corona loss per unit length, R, for good weather, rainy weather and rime weather, respectively n To split the radius of the conductor, E u Maximum field strength at the surface of the wire, E 0 Critical electric field strength;
surface field intensity E of the mesophase M The calculation formula is as follows:
wherein v is a coefficient for calculating the maximum electric field intensity on the surface of the divided conductor, C av Is the average capacitance, N ci The number of splits per phase conductor, r is the radius of the sub-conductor, V is the actual operating voltage, D 1 Is a constant;
surface field intensity E of side phase M (B) The calculation formula is as follows:
in the formula, D 2 Is a constant number, D 2 ＝D 1 ＝D；
Replacing the operating voltage of the transmission line with the average voltage of the head end and the tail end of the transmission line, wherein the weighted average value of the one-year corona loss is as follows:
in the formula, V i And V j Respectively, the head end voltage and the tail end voltage of the transmission line, T 1 Duration of good weather in one year, T 2 Duration of rainy weather in a year, T 3 The duration of rime weather in one year; a. The 1 、A 2 、A 3 Are all the parameters of the replacement, and,
the formula for correcting corona loss is as follows:
P i ′＝μP i
in the formula, P i ' Corona loss after correction, P i Is a weighted average of corona losses, mu is the corona correction factor, f is the voltage frequency, r 1 Is the wire radius; beta is the geometric mean distance of the lead,
R b is the radius of the cylinder where the wire is equivalent to the reference potential.
6. The transmission line loss optimization calculation method based on multi-parameter modification according to claim 5, wherein the calculation method comprises the following steps:
in step S3, the theoretical line loss calculation formula is:
ΔP＝P 1 -P 2
wherein Δ P is the theoretical line loss, P 1 For active power at the head end of the transmission line, P 2 Active power is provided for the tail end of the transmission line;
the corrected theoretical line loss is:
ΔP′＝ΔP+μP i +k w ΔE L
wherein Δ P' is the corrected theoretical line loss, μ P i For corrected corona loss, k w ΔE L Is the corrected resistive loss.
7. The transmission line loss optimization calculation method based on multi-parameter modification according to claim 6, wherein the calculation method comprises the following steps:
in step S4, dividing the theoretical line loss into variable loss and fixed loss;
variable loss P R The calculation formula is as follows:
in the formula I w The current flowing through the line resistor in the working state, R is the line resistor, and U is the voltage on the resistor;
fixed loss Δ P C The calculation formula is as follows:
ΔP C ＝N
in the formula, N is a constant;
the theoretical line loss rate k 1 Comprises the following steps:
statistical line loss rate k 2 The calculation formula is as follows:
wherein Δ S is the line loss power, S 1 For supplying power to the beginning of the gateway, S 2 Sending electric quantity to the tail end of the gateway;
the comprehensive line loss rate χ calculation model is as follows:
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