CN111861136B - Method for calculating station area line loss rate evaluation benchmarking value - Google Patents
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Abstract
The invention relates to a method for calculating a station area line loss rate evaluation benchmarking value, which is characterized in that a sample data cleaning rule is formulated to improve calculation accuracy based on user power consumption information acquisition system data and marketing system basic archive data. Meanwhile, the equivalent resistance method, the least square fitting technology and the big data analysis technology are combined to obtain the station area line loss rate evaluation benchmark value. In order to improve the calculation accuracy, the invention carries out fitting calculation on the training set of the transformer area to obtain the equivalent resistance of the line based on the nonlinear relation between the power supply quantity, the power selling quantity and the root mean square current.
Description
Technical Field
The invention relates to the field of electric power and big data, in particular to a method for calculating a station area line loss rate evaluation benchmarking value.
Background
The line loss rate evaluation benchmarking value is based on the existing equipment parameters, operation and maintenance conditions, user loads and other conditions of the power grid, and the upper limit value of the line loss rate allowed by each power grid company is an important basis for the line loss rate evaluation of power supply enterprises. At present, line loss rate benchmarking values of each network province company mostly do not consider differences caused by factors such as line distribution, user load, urban and rural characteristics and the like, and the benchmarking values are evaluated by adopting the fixed line loss rate of the whole company, so that the phenomenon is not beneficial to the power grid company to develop line loss management and make loss reduction measures. Meanwhile, the traditional line loss rate benchmarking method is limited by the incompleteness and inaccuracy of basic data, and the difficulty in calculating the line loss of the transformer area is high. Therefore, a method for calculating a line loss rate benchmarking value is needed.
The current line loss rate evaluation benchmarking value calculation method mainly comprises various heuristic algorithm calculation methods and traditional calculation methods. A heuristic algorithm calculates line loss such as an artificial neural network method, a particle swarm algorithm and the like, but the heuristic algorithm has the problems of long search time, low convergence speed and trapping in local optimal solution. And traditional power distribution network line loss calculation methods such as a root mean square current method, an average current method, a maximum load loss time method, an equivalent resistance method and the like have high stability and are more suitable for actual operation management of a power grid. The root mean square current method is characterized in that the root mean square current is obtained by calculating parameters such as active power, reactive power and voltage of each element in the known representative daily load, and the electric energy loss of the whole power distribution network can be obtained by combining the known line parameters; the average current method comprises the steps of firstly calculating the average current of each load, starting iterative addition from the tail end of a power distribution network, and finally calculating to obtain the electric energy loss of a corresponding branch; the maximum load loss time method is to calculate the annual electric energy loss of the series branch of the power grid by using the power loss and the maximum load utilization hours when the series branch is under the maximum load; the equivalent resistance method is to equate the resistance in all lines to a total resistance, and then the line loss obtained by the equivalent total resistance and the head end total root mean square current is the line loss value of the whole power distribution network.
The traditional method for calculating the pole value of the line loss rate has strong dependence on basic data of a distribution network such as power, current, line impedance and the like, and the pole value of the line loss rate is difficult to calculate when partial parameters are lost or the data accuracy is low. The problem that the difficulty in obtaining actual line parameters and accurate node data in the operation of a power grid is high is that: each parameter file of the power distribution network has certain deviation with actual data, and the problems of high calculation difficulty and low accuracy exist when the parameters of the power distribution network are directly calculated; the data of each node is affected by adverse factors such as clock consistency, communication signals and the like, and the integrity and accuracy of the data are difficult to guarantee. Therefore, the traditional line loss rate benchmarking value calculation method has certain difficulty in practical engineering application.
Disclosure of Invention
In view of the above, the present invention provides a method for calculating a platform area line loss rate evaluation benchmarking value, which greatly reduces the strong dependence on basic data in a model, can make a platform area line loss rate benchmarking value suitable for a local area by considering factors such as line distribution, user load, urban and rural characteristics, and the like, is helpful for a power grid company to perform line loss management and make specific loss reduction measures, and has strong engineering practicability.
The invention is realized by adopting the following scheme: a method for calculating a station area line loss rate evaluation benchmarking value comprises the following steps:
step S1: formulating a sample data cleaning rule based on the collected user electricity utilization information data and the provided marketing basic archive data to obtain cleaned electricity quantity data;
step S2: establishing a theoretical line loss calculation model of the transformer area during three-phase balance, wherein the equivalent resistance of the line in the model is calculated in the step S3;
step S3: based on the cleaning data of the step S1, a nonlinear quadratic fitting method is applied to solve the line equivalent resistance ReqRAnd the theoretical line loss calculation model of the transformer area in the step S2 is substituted to obtain the theoretical line loss of the transformer area when the three phases are balanced;
step S4: and combining the calculation results of the steps S2 and S3 with the three-phase unbalance correction coefficient, and further calculating a station area line loss rate benchmark value considering the three-phase unbalance factor.
Further, the specific content of step S1 is:
for the current data: 96 data points per day, 1 data point per hour, 24 in total; in 24 data points every day, the null value exceeds 5 samples, the samples in the day are regarded as invalid samples, the invalid samples are removed, and the rest samples are reserved as training data; in 24 data points each day, the zero value exceeds 5 samples, the samples in the day are regarded as invalid samples, the invalid samples are removed, and the rest samples are reserved as training data;
aiming at the electric quantity data: rejecting samples with zero or empty power supply and sale;
for historical line loss data: eliminating samples with historical line loss rate not between (0 and 10), eliminating samples with small electric quantity, namely monthly supply and sale electric quantity smaller than distribution transformer capacity of the distribution area and small loss, namely daily supply and sale electric quantity difference within the range of [ -3,5 ];
aiming at the acquisition success rate: eliminating samples with the collection success rate not equal to 100%;
selecting a data source platform area: the newly added distribution area does not participate in the calculation of the line loss rate benchmark value; and the removed station area does not participate in the calculation of the line loss rate benchmark value.
Further, the specific content of step S2 is:
comprehensively considering the loss of the electric energy meter and the loss of the reactive power compensation device, and combining a traditional equivalent resistance method to obtain a theoretical line loss calculation model of the transformer area in three-phase balance as shown in the formula (1);
in the formula:
ΔAbthe low-voltage network line loss capacity (kWh) in three-phase load balance is represented; n represents the structural coefficient of the power grid, the single-phase power supply is 2, the three-phase three-wire system is 3, and the three-phase four-wire system is 3.5; k denotes the form factor, i.e. the root mean square current IrmsAnd the average current IavThe equivalent relationship of (a) to (b),Iavrepresents the average current (A) at the head end of the line; reqRThe equivalent resistance (omega) of a low-voltage line is represented; t represents the running time (h); d represents the full month calendar number of days (D); delta AdbiRepresenting monthly losses (kWh) of various types of electric energy meters; m isiThe number of each type of electric energy meter is represented; delta ACRepresents the loss of the reactive compensation equipment (kWh);
the root mean square current is calculated as follows:
in the formula: i isiRepresenting the current (A) of the ith point in 24 whole points of the metering point; piThe active power (kW) of the ith point in 24 whole points of the metering point is represented; qiRepresenting the reactive power (kvar) of the ith point in 24 integer points of the metering point;
Uirepresents a group of formulae and Pi、QiCorresponding line voltage (kV); i is1,I2,…,I24The integral current represents the integral current value of any phase in a three-phase current balance state, and if the integral current values of the three phases of the line A, B, C are not equal, the integral current value represents the average value of the sum of the corresponding A, B, C three-phase currents;
the average current is calculated as follows:
in the formula: i is1,I2,…,I24A current value (A) representing 24 hour points on a day; a. thepRepresenting the active electric quantity (kWh) of the head end of the day element; u represents the terminal voltage (kV) of the daily element; lambda represents the average power factor of the head end of the daily element;
p represents daily element head end average power (kW);
the calculation method of the shape coefficient is as follows:
in line loss calculation, k generally needs to be calculated2,k2The determination of (2) should be determined according to the average load rate f and the minimum load rate beta of the load curve; wherein the average load factor f is the average load/current IavAnd large load/current ImaxThe ratio of (a) to (b), namely:
f=Iav/Imax (5)
minimum load factor beta is the minimum load/current IminTo maximum load/current ImaxThe ratio of (a) to (b), namely:
β=Imin/Imax (6)
when the average load rate f is more than or equal to 0.5, k is calculated according to the continuous load curve which changes linearly2The values, namely:
when the average load rate f is less than 0.5, k is calculated according to the second gradient continuous load curve2The values, namely:
further, the specific content of step S3 is:
the square of the supply/sale electricity and the root mean square current is a quadratic equation of unity:
in the formula, a, b and c are divided into quadratic term coefficients, first order coefficient and constant terms of a quadratic equation of root mean square current and supply/sale electric quantity;
It is known that the above formula can be satisfied only when R and I satisfy the following relationship;
in the formula, R is equivalent resistance on the supply (sale) side, and a ', b ' and c ' are divided into negative quadratic coefficient, negative first order coefficient and constant term of a relation equation between the resistance and the current.
On the other hand, in the case of a liquid,
RPPQ=ReqR+RSPQ (11)
in the formula, RPPQIs the sum of all resistances on the supply side, ReqRIs a line resistance, RSPQIs a user side resistance; therefore, the number of the first and second electrodes is increased,
in the formula, a1、b1、c1Negative quadratic term coefficient, negative first order term coefficient and constant term of the relation equation between the power supply side resistance and the current; a is2、b2、c2To useNegative quadratic coefficient, negative first order coefficient and constant term of the relation equation between the household resistance and the current.
Respectively carrying out development analysis and solution on the electricity selling quantity and the power supply quantity in the training set sample and the root mean square current through a nonlinear least square fitting method to obtain RPPQAnd RSPQThen, the equivalent resistance R of the line is obtainedeqR(ii) a After obtaining the equivalent line resistance, substituting the equivalent line resistance into the formula (1) of the step S2 to obtain the theoretical line loss Delta A of the transformer area in three-phase balanceb。
Further, the specific content of step S4 is:
the three-phase load unbalance correction coefficient Kb,KbRelated to the unbalance degree of the three-phase load, the calculation formula is divided into the following three conditions:
three-phase loading one phase heavy, one phase light, one phase average or two phase average, one phase light:
three-phase load one phase heavy, two phase light or one phase average, two phase light:
three-phase load two-phase heavy, one-phase light or two-phase heavy, one-phase average:
wherein a phase current and IavpThe ratio of (A) to (B) is more than 1.2, the average load is 0.8-1.2, and the light load is less than 0.8; epsiloniThree-phase load current imbalance, (%);
in the formula:
Imaxrepresents a maximum one-phase load current (A);
IavCthe average value of the three-phase load current, namely the average value of the load current of the A phase, the B phase and the C phase, (A);
calculating the theoretical electricity quantity loss delta A of the transformer area when the three phases are unbalanced by combining the theoretical line loss when the three phases are balanced in the step S2, the equivalent resistance in the step S3 and the correction coefficient of the three-phase imbalanceb1:
ΔAb1=ΔAb·Kb (18)
In the formula,. DELTA.AbTheoretical line loss at the time of three-phase balance calculated in step S3;
therefore, the bench area line loss rate benchmarking value LLR is calculated as:
compared with the prior art, the invention has the following beneficial effects:
the method and the device give full play to the full data acquisition advantage of the power utilization information acquisition system of the user, and set up the cleaning rule of the sample data of the transformer area according to the current, the electric quantity, the historical line loss rate, the acquisition success rate and other data, thereby improving the data availability and the calculation accuracy. The method greatly reduces the strong dependence on basic data in the model, does not need to depend on distribution network archives and distribution network specific parameters, and each network province company can consider factors such as line distribution, user load, urban and rural characteristics and the like so as to formulate the station area line loss rate benchmark value suitable for the local area, thereby being beneficial to the power grid company to carry out line loss management and formulate specific loss reduction measures and having strong engineering practicability.
Drawings
FIG. 1 is a graph of the power supply amount and the RMS current according to an embodiment of the invention.
Fig. 2 is a diagram illustrating a relationship between power sales and root mean square current according to an embodiment of the present invention.
FIG. 3 is a flow chart of an embodiment of the present invention.
Detailed Description
The invention is further explained below with reference to the drawings and the embodiments.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
As shown in fig. 3, the present embodiment provides a method for calculating a station area line loss rate evaluation benchmarking value, which includes the following steps:
step S1: making a sample data cleaning rule based on the collected user electricity utilization information data and the provided marketing basic archive data to obtain cleaned electricity quantity data, and laying a data foundation for the calculation accuracy of the steps S2-S4;
step S2: establishing a theoretical line loss calculation model of the transformer area during three-phase balance, wherein the equivalent resistance of the line in the model is calculated in the step S3;
step S3: based on the cleaning data of the step S1, a nonlinear quadratic fitting method is applied to solve the line equivalent resistance ReqRAnd the theoretical line loss calculation model of the transformer area in the step S2 is substituted to obtain the theoretical line loss of the transformer area when the three phases are balanced;
step S4: and combining the calculation results of the steps S2 and S3 with the three-phase unbalance correction coefficient, and further calculating a station area line loss rate benchmark value considering the three-phase unbalance factor.
In this embodiment, the power consumption information acquisition system for the user has the problem that external factors such as unsuccessful acquisition and work orders affect the actual line loss rate of the distribution room, so that the quality of sample data is reduced. Meanwhile, the actual data has abnormal data such as zero values, null values and the like, and the line loss calculation of the transformer area is influenced. In order to improve the calculation accuracy of the line loss rate benchmarking value, the present embodiment formulates a sample cleaning rule, and puts forward the following requirements on the data quality of the sample:
for the current data: 96 data points per day, 1 data point per hour, 24 in total; in 24 data points every day, the null value exceeds 5 samples, the samples in the day are regarded as invalid samples, the invalid samples are removed, and the rest samples are reserved as training data; in 24 data points each day, the zero value exceeds 5 samples, the samples in the day are regarded as invalid samples, the invalid samples are removed, and the rest samples are reserved as training data;
aiming at the electric quantity data: rejecting samples with zero or empty power supply and sale;
for historical line loss data: eliminating samples with historical line loss rate not between (0 and 10), eliminating samples with small electric quantity (the monthly supply and the sales electric quantity are both smaller than the distribution transformer capacity of the transformer area) and small loss (the difference of the daily supply and the sales electric quantity is in an interval of [ -3,5 ]);
aiming at the acquisition success rate: eliminating samples with the collection success rate not equal to 100%;
selecting a data source platform area: the newly added distribution area does not participate in the calculation of the line loss rate benchmark value; and the removed station area does not participate in the calculation of the line loss rate benchmark value.
In this embodiment, the specific content of step S2 is:
comprehensively considering the loss of the electric energy meter and the loss of the reactive power compensation device, and combining a traditional equivalent resistance method to obtain a three-phase unbalanced transformer area and a theoretical line loss calculation model as shown in a formula (1);
in the formula:
ΔAbthe low-voltage network line loss capacity (kWh) in three-phase load balance is represented; n represents the structural coefficient of the power network, single-phase power supply is 2, and three-phase three-wire system time is3, 3.5 is taken during the three-phase four-wire system; k represents the form factor, i.e. the root mean square current IrmsAnd the average current IavThe equivalent relationship of (a) to (b),Iavrepresents the average current (A) at the head end of the line; reqRThe equivalent resistance (omega) of a low-voltage line is represented; t represents the running time (h); d represents the full month calendar days (D); delta AdbiRepresenting monthly loss (kWh) of each type of electric energy meter; m isiThe number of each type of electric energy meter is represented; delta ACRepresents the loss of the reactive compensation equipment (kWh);
the method for calculating the root mean square current is as follows:
in the formula: i isiRepresenting the current (A) of the ith point in 24 whole points of the metering point; piThe active power (kW) of the ith point in 24 whole points of the metering point is represented; qiRepresenting the reactive power (kvar) of the ith point in 24 integer points of the metering point;
Uirepresents a group of formulae and Pi、QiCorresponding line voltage (kV); i is1,I2,…,I24The integral current represents the integral current value of any phase in a three-phase current balance state, and if the integral current values of the three phases of the line A, B, C are not equal, the value represents the average value of the sum of the corresponding A, B, C three-phase currents;
the average current is calculated as follows:
in the formula: i is1,I2,…,I24A current value (A) representing 24 whole points on a day; a. thepRepresenting the active electric quantity (kWh) of the head end of the day element; u represents the terminal voltage (kV) of the daily element; λ represents the average power factor at the head end of the daily element;
p represents daily element head end average power (kW);
the calculation method of the shape coefficient is as follows:
in line loss calculation, k generally needs to be calculated2,k2The determination of (2) should be determined according to the average load rate f and the minimum load rate beta of the load curve; wherein the average load factor f is the average load/current IavAnd large load/current ImaxThe ratio of (a) to (b), namely:
f=Iav/Imax (5)
minimum load factor beta is the minimum load/current IminTo maximum load/current ImaxI.e.:
β=Imin/Imax (6)
when the average load rate f is more than or equal to 0.5, k is calculated according to the continuous load curve which changes linearly2The values, namely:
when the average load rate f is less than 0.5, k is calculated according to the second gradient continuous load curve2The values, namely:
in this embodiment, when the line loss rate benchmarking value is calculated by a traditional equivalent resistance method, the most calculation difficulty is to analyze and solve the line equivalent resistance, and the line equivalent resistance depends on the power grid basic data greatly no matter whether the line parameters are obtained from files or the data of each node is analyzed and calculated. According to the embodiment, the equivalent resistance is calculated by adopting a nonlinear least square fitting technology through the strong correlation of the power supply quantity, the power selling quantity and the root mean square current, so that the basic data dependency in the benchmark value calculation process is reduced to the greatest extent. After the collected samples are cleaned according to the cleaning rule, a distribution area with 31 days of samples is selected, and scatter diagrams 1 and 2 of power supply quantity, power sale quantity and root mean square current are shown.
Specifically, the specific content of step S3 is:
the square of the supply/sale electricity and the root mean square current is a quadratic equation of unity:
in the formula, a, b and c are divided into quadratic term coefficients, first order coefficient and constant terms of a quadratic equation of root mean square current and electric quantity for sale;
It is known that the above formula can be satisfied only when R and I satisfy the following relationship;
in the formula, R is equivalent resistance on the supply (sale) side, and a ', b ' and c ' are divided into negative quadratic coefficient, negative first order coefficient and constant term of a relation equation between the resistance and the current.
On the other hand, in the case of a system,
RPPQ=ReqR+RSPQ (11)
in the formula, RPPQIs the sum of all resistances on the supply side, ReqRIs a line resistance, RSPQIs the user side resistance; therefore, the temperature of the molten metal is controlled,
in the formula, a1、b1、c1Negative quadratic coefficient, negative first order coefficient and constant term of the relation equation between the power supply side resistance and the current; a is a2、b2、c2The negative quadratic term coefficient, the negative first order term coefficient and the constant term of the relation equation between the user side resistance and the current.
Respectively carrying out development analysis and solution on the electricity selling quantity and the power supply quantity in the training set sample and the root mean square current through a nonlinear least square fitting method to obtain RPPQAnd RSPQThen, the equivalent resistance R of the line is obtainedeqR。
In this embodiment, the specific content of step S4 is:
considering the influence of three-phase imbalance on the line loss of the transformer area, the embodiment provides the three-phase load imbalance correction coefficient K by combining with a 0.4kV low-voltage network split-phase equivalent resistance method in the power network electric energy loss calculation guide rule DL/T686-2017b,KbRelated to the unbalance degree of the three-phase load, the calculation formula is divided into the following three conditions:
three-phase loading one phase heavy, one phase light, one phase average or two phase average, one phase light:
three-phase load one phase heavy, two phase light or one phase average, two phase light:
three-phase load two-phase heavy, one-phase light or two-phase heavy, one-phase average:
wherein a phase current and IavpThe ratio of (E) is greater than 1.2, which is a heavy load, 0.8E1.2 is the average load, less than 0.8 is the light load; epsiloniThree-phase load current imbalance, (%);
in the formula:
Imaxrepresents a maximum one-phase load current (A);
Iavpthe average value of three-phase load current, namely the average value of the load current of the A phase, the B phase and the C phase (A);
calculating the theoretical electricity quantity loss delta A of the transformer area when the three phases are unbalanced by combining the theoretical line loss when the three phases are balanced in the step S2, the equivalent resistance in the step S3 and the correction coefficient of the three-phase imbalanceb1:
ΔAb1=ΔAb·Kb (18)
In the formula,. DELTA.AbTheoretical line loss at the time of three-phase balance calculated in step S3;
therefore, the calculation model for calculating the benchmarking value LLR of the station area line loss rate is as follows:
preferably, the embodiment gives full play to the full data acquisition advantage of the user power consumption information acquisition system, and determines that the sample data cleaning rule is formulated according to data such as current, electric quantity, historical line loss rate, acquisition success rate and the like in the calculation of the distribution line loss rate evaluation benchmarking value of the user power consumption information acquisition system. And 3, model training is carried out on the screened data sample, so that the algorithm calculation efficiency is greatly improved.
Preferably, in the embodiment, a quadratic nonlinear relationship between the power supply amount and the root mean square current is obtained through analysis and calculation of the sample data of the power supply side, and the equivalent resistance of the power supply side is calculated through a least square fitting technology.
Preferably, in the embodiment, the power selling amount and the root mean square current are obtained to present a quadratic nonlinear relationship through analysis and calculation of the sample data of the power selling side, and the equivalent resistance of the user side is calculated through a least square fitting technology.
Preferably, in this embodiment, based on the fact that the power supply amount, the power selling amount and the root mean square current show a quadratic nonlinear relationship, the training set of the distribution room is subjected to fitting calculation to obtain equivalent resistances of the power supply side and the user side, and the equivalent resistance of the line is obtained from the difference value of the equivalent resistances of the power supply side and the user side.
Preferably, in the embodiment, a traditional equivalent resistance calculation method is adopted in the transformer area theoretical line loss calculation model, and influence factors of the transformer area shape coefficient, loss of each electric energy meter in the transformer area, loss of a reactive power compensation device, three-phase imbalance of the transformer area and the like are comprehensively considered.
Preferably, the platform area line loss rate benchmarking value model in the embodiment considers factors such as loss of the electric energy meter, reactive compensation and platform area three-phase imbalance factors on the basis of an equivalent resistance method. In order to reduce the strong dependence on basic data in the model, the embodiment performs fitting calculation on the platform area training set to obtain the line equivalent resistance through a least square fitting technology based on the nonlinear relation between the power supply quantity, the power selling quantity and the root mean square current, so as to obtain the line loss rate evaluation benchmarking value. The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.
Claims (2)
1. A method for calculating a benchmarking value for evaluating a line loss rate of a transformer area is characterized by comprising the following steps: the method comprises the following steps:
step S1: formulating a sample data cleaning rule based on the collected user electricity utilization information data and the provided marketing basic archive data to obtain cleaned electricity quantity data;
step S2: establishing a theoretical line loss calculation model of the transformer area during three-phase balance, wherein the equivalent resistance of the low-voltage line in the model is calculated in the step S3;
step S3: based on the cleaning data of the step S1, the non-linear quadratic fitting method is applied to solve the equivalent resistance R of the low-voltage lineeqRAnd substituting the theoretical line loss calculation model of the distribution room in the step S2 to obtainThe theoretical line loss of the transformer area during three-phase balance;
step S4: combining the calculation results of the steps S2 and S3 with the three-phase unbalance correction coefficient, and further calculating a station area line loss rate benchmark value considering the three-phase unbalance factor;
the specific content of step S2 is:
comprehensively considering the loss of the electric energy meter and the loss of the reactive power compensation device, and combining a traditional equivalent resistance method to obtain a theoretical line loss calculation model of the transformer area in three-phase balance as shown in the formula (1);
in the formula: delta AbThe low-voltage network line loss capacity (kWh) in three-phase load balance is represented; n represents the structural coefficient of the power grid, the single-phase power supply is 2, the three-phase three-wire system is 3, and the three-phase four-wire system is 3.5; k represents the form factor, i.e. the root mean square current IrmsAnd the average load current IavThe equivalent relationship of (a) to (b),Iavrepresenting the average load current (A) at the head end of the line; reqRThe equivalent resistance (omega) of a low-voltage line is represented; t represents the running time (h); d represents the full month calendar number of days (D); delta AdbiRepresenting monthly losses (kWh) of various types of electric energy meters; m isiThe number of each type of electric energy meter is represented; delta ACRepresents the loss of the reactive compensation equipment (kWh);
the method for calculating the root mean square current is as follows:
in the formula: i isiRepresenting the current (A) of the ith point in 24 whole points of the metering point; piThe active power (kW) of the ith point in 24 whole points of the metering point is represented; qiRepresenting the reactive power (kvar) of the ith point in 24 integer points of the metering point;
Uirepresents a group of formulae and Pi、QiCorresponding line voltage (kV); i is1,I2,…,I24The integral current represents the integral current value of any phase in a three-phase current balance state, and if the integral current values of the three phases of the line A, B, C are not equal, the value represents the average value of the sum of the corresponding A, B, C three-phase currents;
the average load current is calculated as follows:
in the formula: i is1,I2,…,I24A current value (A) representing 24 whole points on a day; a. thepRepresenting the active electric quantity (kWh) of the head end of the daily element; u represents the terminal voltage (kV) of the daily element; λ represents the average power factor at the head end of the daily element;
p represents daily element head end average power (kW);
the calculation method of the shape coefficient is as follows:
in line loss calculation, k generally needs to be calculated2,k2The determination of (2) should be determined according to the average load rate f and the minimum load rate beta of the load curve; wherein the average load factor f is the average load current IavWith the maximum load current ImaxThe ratio of (a) to (b), namely:
f=Iav/Imax (5)
the minimum load factor beta is the minimum load current IminWith the maximum load current ImaxThe ratio of (a) to (b), namely:
β=Imin/Imax (6)
when the average load rate f is more than or equal to 0.5, k is calculated according to the continuous load curve which changes linearly2The values, namely:
when the average load rate f is less than 0.5, k is calculated according to the second gradient continuous load curve2The values, namely:
the specific content of step S3 is:
the square of the supply/sale electricity and the root mean square current is a quadratic equation of unity:
in the formula, a, b and c are divided into quadratic term coefficients, first-order term coefficients and constant terms of a quadratic equation of root-mean-square current and supply/sale electricity;
It is known that the above formula can be satisfied only when R and I satisfy the following relationship;
in the formula, R is equivalent resistance of a supply/sale side, and a ', b ' and c ' are divided into negative quadratic coefficient, negative first order coefficient and constant term of a relation equation between the resistance and the current;
on the other hand, in the case of a liquid,
RPPQ=ReqR+RSPQ (11)
in the formula, RPPQIs the sum of all resistances of the supply side, ReqRIs the equivalent resistance, R, of the low-voltage lineSPQIs the user side resistance;
in the formula, a1、b1、c1Negative quadratic term coefficient, negative first order term coefficient and constant term of the relation equation between the power supply side resistance and the current; a is2、b2、c2Negative quadratic term coefficient, negative first order term coefficient and constant term of the relation equation between the user side resistance and the current;
respectively carrying out development analysis and solution on the electricity selling quantity and the power supply quantity in the training set sample and the root mean square current through a nonlinear least square fitting method to obtain RPPQAnd RSPQThen, the equivalent resistance R of the low-voltage line is obtainedeqR(ii) a After obtaining the equivalent resistance of the low-voltage line, substituting the equivalent resistance into the formula (1) of the step S2 to obtain the theoretical line loss Delta A of the transformer area during three-phase balanceb;
The specific content of step S4 is:
the three-phase unbalance correction coefficient Kb,KbRelated to the unbalance degree of the three-phase load, the calculation formula is divided into the following three conditions:
three-phase loading one phase heavy, one phase light, one phase average or two phase average, one phase light:
three-phase load one phase heavy, two phase light or one phase average, two phase light:
three-phase load two-phase heavy, one-phase light or two-phase heavy, one-phase average:
wherein a phase current and IavpThe ratio of (A) to (B) is more than 1.2, the average load is 0.8-1.2, and the light load is less than 0.8; epsiloniThe current unbalance degrees (%) of the three-phase load are shown;
in the formula:
Imaxrepresents the maximum load current;
Iavpthe average value of three-phase load current is represented, namely the average value of A-phase, B-phase and C-phase load current;
combining the theoretical line loss during three-phase balance of the step S2, the equivalent resistance of the step S3 and the three-phase imbalance correction coefficient, calculating the theoretical line loss delta A during the three-phase imbalance of the transformer areab1:
ΔAb1=ΔAb·Kb (18)
In the formula,. DELTA.AbTheoretical line loss at the time of three-phase balance calculated in step S3;
therefore, the bench area line loss rate benchmarking value LLR is calculated as:
2. the method for calculating the bench mark post value for the line loss rate evaluation of the transformer area according to claim 1, wherein the method comprises the following steps:
the specific content of step S1 is:
for the current data: 96 data points per day, 1 data point per hour, 24 in total; in 24 data points every day, the null value exceeds 5 samples, the samples in the day are regarded as invalid samples, the invalid samples are removed, and the rest samples are reserved as training data; in 24 data points each day, the zero value exceeds 5 samples, the samples in the day are regarded as invalid samples, the invalid samples are removed, and the rest samples are reserved as training data;
for the electric quantity data: rejecting samples with zero or empty power supply and sale;
for historical line loss data: eliminating samples with historical line loss rate not between (0 and 10), eliminating samples with small electric quantity, namely monthly supply and sale electric quantity which are smaller than distribution transformer capacity, eliminating samples with small loss, namely daily supply and sale electric quantity difference within a range of (-3, 5), eliminating samples with line loss which can not be counted, and eliminating samples with line loss rate which is null;
aiming at the acquisition success rate: eliminating samples with the collection success rate not equal to 100%;
selecting a data source platform area: the newly added distribution area does not participate in the calculation of the line loss rate benchmark value; and the removed station area does not participate in the calculation of the line loss rate benchmark value.
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