CN115795889B - Multi-parameter correction-based power transmission line loss optimization calculation method - Google Patents
Multi-parameter correction-based power transmission line loss optimization calculation method Download PDFInfo
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Abstract
A transmission line 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 in various weather; 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 lead are corrected, the corrected loss is added into the original line loss, and the corrected loss is fitted into a new theoretical line loss calculation model, so that the model has more considered factors than the traditional method, the calculation result is more reliable, the accuracy of the line loss rate can be improved, the settlement of the high-voltage electric quantity of the transmission line is more fair, and the coordination and the efficient operation of the power grid are ensured.
Description
Technical Field
The invention relates to the technical field of extra-high voltage distribution network line loss analysis, in particular to a transmission line loss optimization calculation method based on multi-parameter correction, which is mainly suitable for improving the accuracy of 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 departments in China on the operation of the power grid, and the lean line loss calculation is beneficial to the relevant departments to manage the planning and production feasibility of the power grid. Moreover, the trading, pricing and settlement of electricity for the electricity market also rely on the calculation of line losses and line loss rates. Therefore, finding a lean comprehensive line loss calculation model capable of reducing errors and correcting theoretical line loss and statistical line loss simultaneously is urgent.
At present, the root mean square current method, the average current method and the maximum current method are mostly adopted. The root mean square current method has the advantages that the parameter requirement is less, the calculation is simpler and more convenient, and the obtained data has high matching degree with the actual data; however, the method has the disadvantages that the application range is small, the method has a good effect only on the conventional wiring mode, and the load curve and the load node power factor obtained by the method are very different from the actual load node power factor, so the load node current directly obtained by algebraic calculation by the method cannot be directly used as root mean square current. The average current method adopts the electric quantity which is easier to obtain in actual production as a parameter, so that an 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, is applied on the premise of the equivalent relation between the maximum current and the root mean square current, and finally obtains a larger loss calculated value by the maximum current method, so that the result is perfected by using a correction coefficient smaller than 1, and the authenticity is improved; the maximum current method is also insufficient, and the accuracy of the final result can not be ensured 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 planning and designing links of the power distribution network, and other methods are also required to be selected for loss reduction countermeasures and line loss calculation during the operation of the power system.
Disclosure of Invention
The invention aims to overcome the defect and problem of low accuracy in the prior art and provides a high-accuracy transmission line loss optimization calculation method based on multi-parameter correction.
In order to achieve the above object, the technical solution of the present invention is: a transmission line 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 in various weather;
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:
wherein r is 0 Is the unit resistance of the wire, ρ is the wire resistivity, l is the wire length, S is the wire cross-sectional area, N ci The number of splits per phase of wire;
the reactance X of the equivalent circuit is calculated as follows:
wherein x is 0 Reactance in unit length of transmission line, omega is angular velocity under power frequency, L 1 The inductance value of unit inductance is beta is the geometric mean distance of the wires, r d Is the radius of the wire;
the susceptance B calculation formula of the equivalent circuit is as follows:
wherein b is 0 The susceptance is the unit length of the transmission line, and C is the capacitance value of the unit capacitance;
when the length l of the lead meets 500km or less and 1000km or less, correcting a mathematical calculation formula of the resistor R, the reactance X and the susceptance B, wherein the correction coefficient is as follows:
wherein eta is r Correction coefficient of resistance, eta x For reactance correction factor, eta b Is a susceptance correction coefficient.
In step S2, the calculation formula of the resistance loss of the equivalent transmission line is:
wherein delta A is the resistance loss of the equivalent transmission line, T is the running time, i (T) is the instantaneous value of the current passing through the wire, and R is the resistance of the wire;
the calculation formula for correcting the resistance loss is as follows:
ΔE′ L ＝k w ×ΔE L
wherein DeltaE' L K is the line resistance loss after temperature compensation w For the temperature rise compensation coefficient DeltaE L For the line power loss before temperature compensation, R i (20) The resistance value of the ith section of the line per unit length at 20 ℃ is L i For the ith wire length, I pi For rated current value, I if Is the root mean square current value, l i For the length of the i-th type of wire, N ci T is the number of splits per phase of wire te Is ambient temperature.
In step S2, when the resistance loss is corrected, the resistance value of the resistor is corrected, and the correction formula is as follows:
R 0 ＝k θ R 20
r 0 ＝k θ r 20
wherein R is 0 R is the actual resistance of the wire 0 Resistance of wire unit, k θ R is the temperature correction coefficient of resistance 20 R is the resistance value of the wire at 20 DEG C 20 Is the unit resistance of the wire at 20℃, I rms Is the root mean square current value, N ci For the number of splits of each phase of wire, k is the wire temperature coefficient, t is the average air temperature of the selected representative day, and I is the continuous current value when the wire reaches the target temperature at 20 ℃.
In step S2, the corona loss calculation formula is:
wherein P is 1 、P 2 、P 3 Corona loss per unit length in good, rainy and rime weather, respectively, R n To split the wire radius, E u For maximum field strength of the wire surface, E 0 Is the 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 of the surface of the split conductor, C av For average capacitance, N ci For the split number of each phase of wire, r is the radius of the subconductors, V is the actual operating voltage, D 1 Is a constant;
surface field strength E of side phase M (B) The calculation formula is as follows:
wherein D is 2 Is constant, D 2 ＝D 1 ＝D；
The running voltage of the power transmission line is replaced by the average voltage of the head end and the tail end of the power transmission line, and the weighted average value of the annual corona loss is:
wherein V is i And V j Respectively the head end voltage and the tail end voltage of the power transmission line, T 1 For good weather duration in one year, T 2 For duration of rainy weather in one year, T 3 The duration of rime weather in one year; a is that 1 、A 2 、A 3 Are all the parameters of the replacement, and,
the corona loss correction formula is:
P′ i ＝μP i
wherein P' i P for corrected corona loss i Is the weighted average of corona loss, mu is the corona correction factor, f is the voltage frequency, r 1 Is the radius of the wire; beta is the geometric average distance of the wires,R b the radius of the cylinder equivalent to the reference potential of the lead.
In step S3, the theoretical line loss calculation formula is:
ΔP＝P 1 -P 2
wherein DeltaP is theoretical line loss, P 1 Is the active power of the head end of the transmission line, P 2 Active power at the tail end of the transmission line;
the theoretical line loss after correction is:
ΔP′＝ΔP+μP i +k w ΔE L
wherein ΔP' is the theoretical line loss after correction, μP i K for corrected corona loss w ΔW L To correct for the resistance 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:
wherein I is w The current flows through the line resistor in the working state, R is the line resistor, and U is the upper voltage of the resistor;
fixed loss ΔP C The calculation formula is as follows:
ΔP C ＝N
wherein N is a constant;
theoretical line loss rate k 1 The method comprises the following steps:
statistics of line loss rate k 2 The calculation formula is as follows:
wherein DeltaS is the line loss electric quantity, S 1 For supplying electricity to the beginning of the gateway, S 2 Delivering electricity 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:
in the transmission line loss optimization calculation method based on multi-parameter correction, on the premise of considering various factors, the resistance loss and the corona loss of the lead are corrected, the corrected loss is added into the original line loss, the corrected loss is fitted into a new theoretical line loss calculation model, the model has more considered factors than the traditional method, and the calculation result is more reliable. Therefore, the invention can improve the accuracy of the line loss rate, so that the settlement of the high-voltage electric quantity of the transmission line is fairer, and the coordination and the high-efficiency operation of the power grid are ensured.
Drawings
Fig. 1 is a flowchart of a transmission line loss optimization calculation method based on multi-parameter correction.
Fig. 2 is a schematic diagram of an overhead transmission line model in accordance with the present invention.
Fig. 3 is a graph of line loss rate versus power for the present invention.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings and detailed description.
Referring to fig. 1, a transmission line loss optimization calculation method based on multi-parameter correction includes the following steps:
s1, constructing an overhead transmission line model, as shown in FIG. 2; correcting resistance, reactance and susceptance in the overhead transmission line model according to the length of the transmission line;
the calculation formula of the resistance R of each phase of conducting wire of the equivalent circuit is as follows:
wherein r is 0 Is the unit resistance of the wire, ρ is the wire resistivity, l is the wire length, S is the wire cross-sectional area, N ci The number of splits per phase of wire;
the reactance X of the equivalent circuit is calculated as follows:
wherein x is 0 Reactance in unit length of transmission line, omega is angular velocity under power frequency, L 1 The inductance value of unit inductance is beta is the geometric mean distance of the wires, r d Is the radius of the wire;
the susceptance B calculation formula of the equivalent circuit is as follows:
wherein b is 0 The susceptance is the unit length of the transmission line, and C is the capacitance value of the unit capacitance;
when the length l of the lead meets 500km or less and 1000km or less, correcting a mathematical calculation formula of the resistor R, the reactance X and the susceptance B, wherein the correction coefficient is as follows:
wherein eta is r Correction coefficient of resistance, eta x For reactance correction factor, eta b Is electric powerReceiving a correction coefficient;
the resistance R, reactance X, susceptance B are multiplied by 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 in various weather;
the internal characteristics of the conductor can change along with the change of temperature, so that the resistivity can also change along with the change of temperature, and meanwhile, the temperature of the working environment of the conductor can influence the heat dissipation speed of the conductor, so that 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:
wherein delta A is the resistance loss of the equivalent transmission line, T is the running time, i (T) is the instantaneous value of the current passing through the wire, and R is the resistance of the wire;
the temperature compensation is to multiply the temperature rise compensation coefficient on the electric energy loss calculation result of the resistor, so as to correct the resistance loss, and the calculation formula is as follows:
ΔE′ L ＝k w ΔE L
wherein DeltaE' L K is the line resistance loss after temperature compensation w For the temperature rise compensation coefficient DeltaE L For the line power loss before temperature compensation, R i (20) The resistance value of the ith section of the line per unit length at 20 ℃ is L i For the ith wire length, I pi For rated current value, I if Is the root mean square current value, I i For the length of the i-th type of wire, N ci T is the number of splits per phase of wire te Is ambient temperature;
in the calculation process, the temperature of the wire can be increased by the current flowing around the wire, and the air temperature can also influence the wire so as to influence the accuracy of resistance loss calculation, so that the resistance value of the resistor is required to be corrected on the basis of correcting the whole resistance loss, and the result is ensured to be more reliable; the correction formula is:
R 0 ＝k θ R 20
r 0 ＝k θ r 20
wherein R is 0 R is the actual resistance of the wire 0 Resistance of wire unit, k θ R is the temperature correction coefficient of resistance 20 R is the resistance value of the wire at 20 DEG C 20 Is the unit resistance of the wire at 20℃, I rms Is the root mean square current value, N ci For the split number of each phase of wire, k is the temperature coefficient of the wire, t is the average temperature of the selected representative day, and I is the continuous current value when the wire reaches the target temperature when the temperature is 20 ℃;
in general, when a power transmission line with a voltage class of 110kV and above is calculated, the corona loss is smaller, 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 level of 110kV to 330kV is relatively fuzzy, so that the corona loss can be estimated according to 0.5 to 2.0 percent of the active loss of the wire, the corona loss is smaller in good weather, and the corona loss is larger in ice and snow weather and rime weather; the corona loss calculation formula of the unit length of the power transmission line with the voltage class of 500 kV-1000 kV is as follows:
wherein P is 1 、P 2 、P 3 Corona loss per unit length in good, rainy and rime weather, respectively, R n To split the wire radius, E u For wire gaugeMaximum field strength of face E 0 Is the 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 of the surface of the split conductor, C av For average capacitance, N ci For the split number of each phase of wire, r is the radius of the subconductors, V is the actual operating voltage, D 1 Is a constant;
surface field strength E of side phase M (B) The calculation formula is as follows:
wherein D is 2 Is constant due to D 1 Only ratio D 2 About 6% greater, so that D is considered to be approximately 2 ＝D 1 ＝D；
The running voltage of the power transmission line is replaced by the average voltage of the head end and the tail end of the power transmission line, and the weighted average value of the annual corona loss is:
wherein V is i And V j Respectively the head end voltage and the tail end voltage of the power transmission line, T 1 For good weather duration in one year, T 2 For duration of rainy weather in one year, T 3 The duration of rime weather in one year; a is that 1 、A 2 、A 3 Are all the parameters of the replacement, and,
the corona loss correction formula is:
P′ i ＝μP i
wherein P' i P for corrected corona loss i Is the weighted average of corona loss, mu is the corona correction factor, f is the voltage frequency, r 1 Is the radius of the wire; beta is the geometric average distance of the wires,R b the radius of the cylinder is equivalent to the reference potential of the lead;
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 can be obtained:wherein (1)>S 'is the total power supply quantity of the power transmission line' 2 Is the equivalent output electric quantity of the transmission line, delta Q is reactive power consumption, delta S ZL Delta S is the loss of the transmission line A Is the reactor loss; and the active power P of the head end of the power transmission line can be calculated according to the complex power 1 The method comprises the steps of carrying out a first treatment on the surface of the According to the power transmission quantity S at the tail end of the power transmission line 2 The active power P at the tail end of the transmission line can also be obtained 2 ；
The theoretical line loss calculation formula is:
ΔP＝P 1 -P 2
wherein DeltaP is theoretical line loss, P 1 Is the active power of the head end of the transmission line, P 2 Active power at the tail end of the transmission line;
the effects of resistance loss and corona loss are not considered in the calculation of the line loss after parameter correction. The above analysis shows the effect of temperature on resistance and corona loss, and the correction coefficients of resistance loss and corona loss are calculated. 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 the lead wire and the influence of field intensity and different weather on the corona loss are ignored, the calculation result is inaccurate, and the difference between the calculation result and the actual value is larger. Therefore, the invention proposes to correct the resistance loss and the corona loss of the lead on the premise of considering various factors, adds the corrected loss into the original line loss, and provides a new theoretical line loss calculation model, the calculation formula is shown as follows, the model has more considered factors than the traditional method, and the calculation result is more reliable;
the theoretical line loss after correction is:
ΔP′＝ΔP+μP i +k w ΔE L
wherein ΔP' is the theoretical line loss after correction, μP i K for corrected corona loss w ΔE L Is the resistance loss after correction, and the resistance of the 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 tiny load variation on the line loss is ignored when calculating the theoretical line loss, calculating the line loss rate from the theoretical line loss calculation model alone can make the calculation result inaccurate. 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 the theoretical line loss into variable loss and fixed loss;
variable loss P R The calculation formula is as follows:
wherein I is w The current flows through the line resistor in the working state, R is the line resistor, and U is the upper voltage of the resistor;
fixed loss ΔP C The calculation formula is as follows:
ΔP C ＝N
wherein N is a constant;
theoretical line loss rate k 1 The method comprises the following steps:
statistics of line loss rate k 2 The calculation formula is as follows:
wherein DeltaS is the line loss electric quantity, S 1 For supplying electricity to the beginning of the gateway, S 2 Delivering electricity 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 two can be combined to construct the comprehensive line loss rate, the comprehensive line loss errors are mutually corrected, and the influence of the variation of factors such as temperature, corona loss, power and the like on the line loss rate can be more accurately expressed.
After the duty ratio of different weather in one year is selected, the resistance loss and the corona loss are obtained according to the split number of the wire, the maximum field intensity coefficient of the surface, the radius of the subconductors and the actual running voltage, and the 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 by a gateway of a transmission line within one year, solving a relation between a statistical line loss rate and power, and fitting the statistical line loss data and the relation to comprehensive when different powers are selectedThe line loss rate can be calculated according to the pointTo draw the line loss rate with the power change.
The power is frequently transmitted in a cross region of a certain province, and the comprehensive line loss rate is used for converting the power of a power grid gateway of a power transmission region into the power grid of a power receiving region, so that the comprehensive line loss rate of the province is selected, the single line loss rate in the past is recorded as a fixed value as 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 circuit is R=5.67 omega, wherein the corona loss is influenced by temperature and weather conditions, so that the ratio of rain, fog and ice and snow weather is thatThe 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 subconductors is 0.6mm, the actual running voltage is 550KV, the calculated and corrected corona loss is 8.72MW, the sum of the fixed losses of the overhead line and the transformer is 13.67MW, and the fixed loss is substituted into a theoretical line loss rate calculation formula to obtain a theoretical line loss rate;
selecting statistical line loss data measured by a gateway of the power transmission line within one year, and obtaining 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, the points (P) under different powers are respectively taken i ，k 1i ) (S) i ，k 2i ) Taking points of the comprehensive line loss rate after the two line loss rates are correctedThe power taken is as in table 1;
TABLE 1 theoretical line loss Rate, statistical line loss Rate, comprehensive line loss Rate and Power relationship
| Power (MW) | Theoretical line loss rate% | Statistics of line loss Rate% | Comprehensive line loss rate% |
| 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 theoretical line loss rate, the curve of the statistical line loss rate with the power change and the function image of the correction curve are shown in fig. 3. Therefore, the image of the correction curve is positioned in the middle of the function images expressed by the two images, theoretical factors and actual factors are comprehensively considered, and errors are reduced through mutual correction.
The invention corrects the influence of the temperature, weather and humidity on the resistance loss and the corona loss aiming at the existing theoretical line loss influence factors, and provides a corrected theoretical line loss calculation model based on the corrected theoretical line loss. According to the influence factors of power on theory and statistical line loss, a comprehensive line loss rate calculation model is established, so that the theory line loss and the statistical line loss can be fully integrated and mutually corrected, and errors caused by adopting a single line loss calculation method are avoided. The line loss model proposed by the invention can be seen when applied to an actual transmission line: the calculation result of the comprehensive line loss rate of the model is closer to the actual value under different powers, the comprehensive line loss rate is 1.32% when the current power of 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 method improves the statistical line loss precision by 18.5 percent, is closer to the actual line loss rate of the engineering by 1.3 percent at the moment, and ensures that the settlement of the high-voltage electric quantity of the transmission line is fairer. Therefore, the comprehensive line loss rate calculation model provided by the invention has strong persuasion, high accuracy and strong practical significance.
Claims (1)
1. The transmission line loss optimization calculation method based on multi-parameter correction is characterized by comprising the following steps of:
s1, correcting resistance, reactance and susceptance in an overhead transmission line model according to the length of the transmission line;
the calculation formula of the resistance R of each phase of conducting wire of the equivalent circuit is as follows:
wherein r is 0 Is the unit resistance of the wire, ρ is the wire resistivity, l is the wire length, S is the wire cross-sectional area, N ci The number of splits per phase of wire;
the reactance X of the equivalent circuit is calculated as follows:
wherein x is 0 Reactance in unit length of transmission line, omega is angular velocity under power frequency, L 1 The inductance value of unit inductance is beta is the geometric mean distance of the wires, r d Is the radius of the wire;
the susceptance B calculation formula of the equivalent circuit is as follows:
wherein b is 0 The susceptance is the unit length of the transmission line, and C is the capacitance value of the unit capacitance;
when the length l of the lead meets 500km or less and 1000km or less, correcting a mathematical calculation formula of the resistor R, the reactance X and the susceptance B, wherein the correction coefficient is as follows:
wherein eta is r Correction coefficient of resistance, eta x For reactance correction factor, eta b Is a susceptance correction coefficient;
s2, correcting the resistance loss of the power transmission line under the influence of temperature; correcting corona loss in various weather;
the calculation formula of the resistance loss of the equivalent transmission line is as follows:
wherein delta A is the resistance loss of the equivalent transmission line, T is the running time, i (T) is the instantaneous value of the current passing through the wire, and R is the resistance of the wire;
the calculation formula for correcting the resistance loss is as follows:
ΔE′ L ＝k w ×ΔE L
wherein DeltaE' L K is the line resistance loss after temperature compensation w For the temperature rise compensation coefficient DeltaE L For the line power loss before temperature compensation, R i(20) The resistance value of the ith section of the line per unit length at 20 ℃ is L i For the ith wire length, I pi For rated current value, I if Is the root mean square current value, l i For the length of the i-th type of wire, N ci T is the number of splits per phase of wire te Is ambient temperature;
when the resistance loss is corrected, the resistance value of the resistor is corrected, and the correction formula is as follows:
R 0 ＝k θ R 20
r 0 ＝k θ r 20
wherein R is 0 R is the actual resistance of the wire 0 Resistance of wire unit, k θ R is the temperature correction coefficient of resistance 20 R is the resistance value of the wire at 20 DEG C 20 Is the unit resistance of the wire at 20℃, I rms Is the root mean square current value, N ci For the split number of each phase of wire, k is the temperature coefficient of the wire, t is the average temperature of the selected representative day, and I is the continuous current value when the wire reaches the target temperature when the temperature is 20 ℃;
the corona loss calculation formula is:
wherein P is 1 、P 2 、P 3 Corona loss per unit length in good, rainy and rime weather, respectively, R n To split the wire radius, E u For maximum field strength of the wire surface, E 0 Is the 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 of the surface of the split conductor, C av For average capacitance, N ci For the split number of each phase of wire, r is the radius of the subconductors, V is the actual operating voltage, D 1 Is a constant;
surface field strength E of side phase M (B) The calculation formula is as follows:
wherein D is 2 Is constant, D 2 ＝D 1 ＝D；
The running voltage of the power transmission line is replaced by the average voltage of the head end and the tail end of the power transmission line, and the weighted average value of the annual corona loss is:
wherein V is i And V j Respectively the head end voltage and the tail end voltage of the power transmission line, T 1 For good weather duration in one year, T 2 For duration of rainy weather in one year, T 3 The duration of rime weather in one year; a is that 1 、A 2 、A 3 Are all the parameters of the replacement, and,
the corona loss correction formula is:
P i ′＝μP i
wherein P is i ' is corrected corona loss, P i Is the weighted average of corona loss, mu is the corona correction factor, f is the voltage frequency, r 1 Is the radius of the wire; beta is the geometric average distance of the wires,R b the radius of the cylinder is equivalent to the reference potential of the lead;
s3, constructing a theoretical line loss correction model;
the theoretical line loss calculation formula is:
ΔP＝P 1 -P 2
wherein DeltaP is theoretical line loss, P 1 Is the active power of the head end of the transmission line, P 2 Active power at the tail end of the transmission line;
the theoretical line loss after correction is:
ΔP′＝ΔP+μP i +k w ΔE L
wherein ΔP' is the theoretical line loss after correction, μP i K for corrected corona loss w ΔE L The resistance loss after correction;
s4, fitting the theoretical line loss and the statistical line loss to construct a comprehensive line loss rate calculation model;
dividing the theoretical line loss into variable loss and fixed loss;
variable loss P R The calculation formula is as follows:
wherein I is w The current flows through the line resistor in the working state, R is the line resistor, and U is the upper voltage of the resistor;
fixed loss ΔP C The calculation formula is as follows:
ΔP C ＝N
wherein N is a constant;
theoretical line loss rate k 1 The method comprises the following steps:
statistics of line loss rate k 2 The calculation formula is as follows:
wherein DeltaS is the line loss electric quantity, S 1 Is a gatewayInitial end power supply quantity S 2 Delivering electricity to the tail end of the gateway;
the comprehensive line loss rate χ calculation model is as follows:
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