A method for calculating technical line loss based on load curve

Abstract

The present invention discloses a method for calculating technical line loss based on load curve, which relates to the field of power operation and maintenance. The actual situation of the line is intricate, the line length cannot be accurately measured, and it is labor-intensive; the algorithm is complex and the real-time performance is poor. The present invention fits the public transformer current data, integrates the square of the load curve of the public transformer current, and calculates I<supgt;2< / supgt;t based on the integration result; based on the formula I<supgt;2< / supgt;Rt and the calculated "I<supgt;2< / supgt;t" and "R"; calculates the technical line loss through the formula. This technical solution makes full use of the currently available power grid data, reorganizes it, and calculates according to the continuous load curve to obtain more accurate and reliable results. By calculating the technical line loss based on the load curve and the voltage at both ends, the problem of measuring the line length is avoided, and it is transformed into a problem of energy conversion, improving the real-time performance and reducing the complexity of the algorithm.

Description

Technical Field

[0001] The present invention relates to the field of power operation and maintenance, and in particular to a method for calculating technical line losses based on load curves. Background Art

[0002] Accurately calculating the theoretical loss of the power grid plays a very important role in scientifically evaluating economic benefits and rationally arranging the operation mode of the power system. The level of line loss is closely related to each link of power generation and supply, so the characteristics and laws of each link that affect line loss should be carefully studied. Due to the random nature of the power flow, the network loss problem has not been solved satisfactorily.

[0003] Some data analyses are based on line loss research, but if technical line loss (inevitable loss on the line) and non-technical line loss (loss caused by improper management or user electricity theft) are not separated, the research results will be affected.

[0004] For example, when the system searches for electricity theft users, it will lock the line loss of the substation with high line loss rate, but it is not sure whether the high line loss rate is caused by technical line loss or non-technical line loss, which will affect the result judgment. The technical line loss calculation method based on the load curve is to better mine the power consumption information, and provide a certain basis for real-time prevention of electricity theft and assisting on-site staff in the investigation of suspected electricity theft users. According to the in-depth mining and analysis of a large amount of electricity consumption data, it is found that there may be a certain law between the line loss rate of the substation and the power consumption. The calculation methods of power grid line loss can be mainly divided into two categories: one is various equivalent model algorithms established based on the physical characteristics of the main loss components of the network; the other is various statistical models and neural network models established based on feeder data. Among them, the equivalent model algorithm is widely used. Although these methods meet the needs of rough calculation of technical line loss to a certain extent. However, with the development of power grid construction, most power supply companies have been able to obtain more and more accurate data than before, so it is necessary to make full use of these data to improve the rationality and accuracy of line loss calculation.

[0005] The traditional technical line loss calculation methods mainly include: voltage loss method, equivalent resistance method, and substation loss rate method. All of the above methods are engineering approximation methods. The voltage loss method and substation loss rate method are statistical approximate calculations. The equivalent resistance method is an approximate calculation under specific load and fluctuation conditions, and does not consider the impact of load three-phase imbalance and user load characteristics on the calculation. Existing intelligent algorithms for calculating technical line loss, such as clustering algorithms, artificial neural networks, genetic algorithms, and other intelligent algorithms, all require the total length of the line. However, the actual situation of the line is complicated, the line length cannot be accurately measured, and the manual labor consumption is also large. The algorithm is complex and the real-time performance is poor. Summary of the invention

[0006] The technical problem to be solved and the technical task proposed by the present invention are to improve and perfect the existing technical solutions and provide a method for calculating technical line loss based on load curves to achieve the purpose of improving real-time performance and reducing algorithm complexity. To this end, the present invention adopts the following technical solutions.

[0007] A method for calculating technical line loss based on load curve comprises the following steps:

[0008] 1) Get data;

[0009] The electricity consumption data of electricity users in the electricity consumption information collection system is collected and stored in the central database through the data transmission channel and the data receiving system; the collected electricity consumption data includes: real-time data of public transformer load and user load, one data point every 15 minutes, a total of 96 data points per day;

[0010] 2) Data preprocessing to remove outliers;

[0011] 3) Fitting the public transformer current data;

[0012] Obtain 96 public transformer current points in one day, fit them by polynomial approach, select the 9th order fitting, and obtain the load curve of public transformer current;

[0013] 4) Integrate the square of the load curve of the public transformer current;

[0014] 5) Based on the integral result, calculate I 2 t; where I is the common transformer current and t is the time;

[0015] 6) Calculate the three-phase voltage difference ΔU of the public transformer load and the user load respectively;

[0016] 7) Calculate the resistance R by dividing ΔU by the common variable current I;

[0017] 8) Calculate the technical line loss based on formula I 2 Rt and the calculated "I 2 t" and "R"; by the formula Calculate technical line loss.

[0018] As a preferred technical means: in step 3), for the linear fitting of the load curve of the daily transformer current, the Curve Fitting Tool toolbox in MATLAB is used, and the Polynomial approximation method is used for fitting, and then the 7th, 8th and 9th order fitting results are compared to compare whether the error sum of squares (SSE) is close to 0, whether the multiple determination coefficient (R-square) is close to 1, whether the adjusted R-square of the degrees of freedom is close to 1 and whether the root mean square error (RMSE) is close to 0, and finally the 9th order fitting with good effects on all parameters is selected.

[0019] As a preferred technical means: in step 5), I 2 The calculation formula of t is:

[0020]

[0021] The unit of the transformer current I is ampere (A), the unit of time t is second (s), and T is 86400 seconds (s) in one day; for a three-phase circuit, the A, B, and C phases should be calculated separately;

[0022] As a preferred technical means: in step 6), the calculation formula of ΔU is ΔU=U-U0, U is one phase of the three-phase public transformer voltage of the public transformer load, U0 is one phase of the three-phase voltage of the user load, and the terminal voltages of the remaining two phases of the three-phase are calculated similarly.

[0023] As a preferred technical means: in step 7), the calculation formula of R is: Among them, U and I are one phase of the three-phase public transformer voltage and one phase of the three-phase public transformer current of the public transformer load, and the units are volts V and amperes A. U0 is one phase of the three-phase voltage of the user load; according to the 96 voltage points of each phase in the three phases every day, they are then divided by the public transformer current of each phase in the three phases of the corresponding public transformer load at each time point; finally, 96 resistance points are obtained in one day, and the average value is calculated to obtain the resistance of one day.

[0024] Beneficial effects: This technical solution makes full use of the currently available power grid data, reorganizes it, and calculates it according to the continuous load curve to obtain more accurate and reliable results. By calculating the technical line loss based on the load curve and the voltage at both ends, the problem of measuring the line length is avoided and converted into an energy conversion problem, which improves real-time performance and reduces the complexity of the algorithm. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a principle block diagram of the present invention.

[0026] Figure 2 It is a flow chart of load curve calculation of public transformer current of the present invention.

[0027] Figure 3 It is a technical line loss calculation flow chart of the present invention.

[0028] Figure 4 It is a daily power supply curve diagram of a certain area 7 of the present invention.

[0029] Figure 5 It is a line loss rate curve diagram of a certain area of ​​the present invention and a line loss rate curve diagram after removing technical line loss. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0031] like Figure 1 , 2 As shown in , 3, the present invention comprises the following steps:

[0032] 1) Get data;

[0033] The electricity consumption data of electricity users in the electricity consumption information collection system is collected and stored in the central database through the data transmission channel and the data receiving system; the collected electricity consumption data includes: real-time data of public transformer load and user load, one data point every 15 minutes, a total of 96 data points per day;

[0034] 2) Data preprocessing to remove outliers;

[0035] 3) Fitting the public transformer current data;

[0036] Obtain 96 public transformer current points in one day, fit them by polynomial approach, select the 9th order fitting, and obtain the load curve of public transformer current;

[0037] 4) Integrate the square of the load curve of the public transformer current;

[0038] 5) Based on the integral result, calculate I 2 t; where I is the common transformer current and t is the time;

[0039] 6) Calculate the three-phase voltage difference ΔU between the public transformer load and the user load;

[0040] 7) Calculate the resistance R by dividing ΔU by the common variable current I;

[0041] 8) Calculate the technical line loss based on formula I 2 Rt and the calculated "I 2 t" and "R"; by the formula Calculate technical line loss.

[0042] Explanation of public variable load and user load

[0043] User loads include: load current, load transformer voltage

[0044] The loads of the public transformer are: public transformer current, public transformer voltage

[0045] This technical solution uses three types of data: public transformer current, public transformer voltage and user load public transformer voltage. And all of them are three-phase data.

[0046] Some of the steps are further described below.

[0047] 1. Data Source

[0048] The electricity consumption data of several electricity users in the electricity consumption information collection system are collected, and the data are stored in a central database through a data transmission channel and a data receiving system, which serves as the data source for the technical line loss calculation of the inventive method.

[0049] The objects of analysis of this method are the bus loss, public transformer load and user load of the substation area. The public transformer load and user load of each day are the real-time data of the day in the power information collection system, with one data point every 15 minutes, and a total of 96 data points per day.

[0050] 2. Data preprocessing

[0051] The calculation of the total line loss in the substation area is mainly based on the difference between the power supply in the power consumption information collection system and the actual power sales. The specific formula is: Line loss power = power supply - power sales, power supply = factory power supply + input power + purchased power. The power sales include two parts, one is the power supply for non-power production supplied by the power enterprise to the enterprise, and the other is the power sold to users.

[0052] 3. Line loss analysis

[0053] Line loss can be divided into technical line loss and non-technical line loss (also called management loss) according to its nature. Line loss can be divided into variable loss, constant loss and unknown loss according to its loss characteristics. Technical loss is a part of loss that cannot be avoided. Non-technical loss is caused by inadequate management work and is avoidable.

[0054] During the transmission and distribution of the power grid, a part of the power loss is related to the equipment parameters and load of the power grid. This loss belongs to the normal loss of equipment operation and is an inevitable part of the loss. This part of the loss can be obtained through the theoretical calculation of the typical daily line loss, which is called technical loss, also called theoretical loss. The theoretical line loss includes several aspects: (1) the power loss generated by the power grid not less than 35kV; (2) the power loss generated by the 6-20kV distribution network; (3) the power loss generated by the low-voltage network not higher than 0.4kV; (4) the power loss of parallel capacitors, parallel reactors, phase regulators, voltage transformers and the power used by station transformers; (5) the power loss of high-voltage direct current transmission systems (direct current lines, grounding electrode systems, converter stations). The technical line loss calculation method invented in this paper mainly calculates the part of the power energy converted into heat energy during the transportation process.

[0055] 4. Theoretical basis for calculating technical line loss

[0056] There are four main formulas for calculating electric energy: W = Pt, W = UIt, W = I 2 Rt and The unit is joule. W is electrical energy, P is power, U is voltage, I is current, R is resistance, and t is time. The first two are applicable to all circuits, and the last two are only applicable to pure resistance circuits. Because the last two methods mainly calculate the energy of pure resistance in the circuit when electrical energy is converted into heat energy. If the circuit where electrical energy is converted into other energy, such as mechanical energy, light energy, etc., these forms of energy will not be included in the calculation. In short, in a circuit where electrical energy is converted into composite energy, using the fourth method to calculate electrical energy will only calculate the energy converted into heat energy. Because the fourth method is also Joule's law: Q=I 2 Rt, Joule's law is a law that quantitatively explains the conversion of electrical energy into heat energy by conducting current. The content is: the heat generated by current passing through a conductor is proportional to the square of the current, proportional to the resistance of the conductor, and proportional to the time of power on. Therefore, the heat energy loss in the technical line loss calculated using Joule's law is approximately equal to the technical line loss.

[0057] 5. “I 2 t" calculation

[0058] The public transformer current load is not a fixed value. There is a public transformer current load point every 15 minutes in the electricity consumption information collection system. For the 96 public transformer current points in a day, a curve is first fitted, and then the square of the fitted curve is integrated. For the linear fitting of the public transformer current load curve of a day, the Curve Fitting Tool toolbox in MATLAB is used, and the Polynomial polynomial approximation method is used for fitting, and then the 7th, 8th and 9th order fitting results are compared. The main comparison is whether the error sum of squares (SSE) is close to 0, whether the multiple determination coefficient (R-square) is close to 1, whether the degree of freedom adjusted R-square (Adjusted R-square) is close to 1 and whether the root mean square error (RMSE) is close to 0. Finally, the 9th order fitting with good effects on each parameter is selected. The public transformer current load curve of a day is obtained, and it is integrated to obtain "I 2 t". The specific formula is: The unit of the transformer current I is ampere (A), the unit of time t is second (s), and T is 86400 seconds (s) in one day. For a three-phase circuit, the A, B, and C phases should be calculated separately.

[0059] 6. Calculation of resistance "R"

[0060] The resistance calculation mainly calculates the resistance of the conductor. The resistance calculation formula of the conductor is: The length L of the wire cannot be measured in practice. Since the power consumption information collection system mainly contains three-phase voltage, three-phase current and other data, The I in the formula is the three-phase public transformer current in the public transformer load of the substation, and the terminal voltage ΔU in the formula is calculated using the three-phase public transformer voltage in the public transformer load on the substation side and the three-phase voltage in the user load on the user side. There are 96 voltage data points every day, and the difference in the three-phase voltage of the public transformer load and the user load is calculated at the corresponding time points. The formula is ΔU=U-U0, U is one phase of the three-phase public transformer voltage of the public transformer load, and U0 is one phase of the three-phase voltage of the user load. Similarly, the terminal voltages of the remaining two phases of the three phases are calculated. The final result is that each phase of the three phases has 96 voltage points every day, and then divided by the public transformer current of each item in the three phases of the corresponding public transformer load at each time point. Finally, 96 resistance points are obtained in one day, and the average value is calculated to get the resistance of one day. The specific calculation formula is Among them, U and I are the three-phase public transformer voltage and three-phase public transformer current of the public transformer load, in volts (V) and amperes (A), and U0 is the three-phase voltage of the user load.

[0061] 7. Determine the method for calculating technical line loss

[0062] Based on “I 2 Rt" method and the calculated "I 2t" and "R", calculate the technical line loss for one day and divide it by 3600000 to convert it to kilowatt-hour (kw.h). The formula is Among them, U and I are the public transformer voltage and public transformer current of the public transformer load, and U0 is the voltage of the user load.

[0063] 8. Implementation Examples

[0064] The implementation of the method of the present invention is as follows: Figure 4-5 shown. Figure 4 The following is the daily power supply data of a certain area A in Zhejiang Province from January 1 to February 24, 2017. Figure 5 This is the analysis result of the method of the present invention.

[0065] Figure 5 The line loss rate after removing the technical line loss is obtained by calculating the technical line loss using the method of the invention, and is obtained by Figure 4 Power supply and Figure 5 By comparing the two line loss rates, it can be seen that the higher the power supply, the higher the proportion of technical line loss, which is consistent with the actual situation. This method is reasonable to a certain extent.

[0066] above Figure 1-3 The method for calculating technical line loss based on load curve shown is a specific embodiment of the present invention, which has embodied the substantial characteristics and progress of the present invention. According to actual use needs and under the guidance of the present invention, equivalent modifications in shape, structure, etc. can be made to the method, which are all within the protection scope of this scheme.

Claims

1. A method for calculating technical line loss based on load curve, characterized in that The following steps are involved: 1) Get data; Collect electricity consumption data of electricity users in the electricity consumption information collection system, and store the data in the central database through the data transmission channel and the data receiving system; The collected electricity consumption data include: real-time data of public transformer load and user load, one data point every 15 minutes, a total of 96 data points per day; 2) Data preprocessing to remove outliers; 3) Fitting the public transformer current data; Obtain 96 public transformer current points in one day, fit them by polynomial approach, select the 9th order fitting, and obtain the load curve of public transformer current; 4) Integrate the square of the load curve of the public transformer current; 5) Based on the integral result, we can calculate ; In the formula, I is the public variable current, t For time; 6) Calculate the three-phase voltage difference ΔU between the public transformer load and the user load; 7) Calculate the resistance R by dividing ΔU by the common variable current I; 8) Calculate the technical line loss based on the formula and the calculated" "and" R "; through the formula , calculate the technical line loss; In step 7), the calculation formula of R is ,in, U and I The three-phase transformer voltage and three-phase transformer current of the transformer load are expressed in volts V and amperes A. U 0 is the three-phase voltage of the user load; for the 96 voltage points of one phase of the three-phase voltage at the public transformer end and the user end every day, divide it by the public transformer current at each time point of the phase in the three-phase of the corresponding public transformer load; finally, 96 resistance points are obtained in one day, and the average value is calculated to obtain the resistance of one day.

2. A method for calculating technical line loss based on load curve according to claim 1, characterized in that: In step 3), for the linear fitting of the load curve of the daily transformer current, the Curve Fitting Tool toolbox in MATLAB is used to fit the load curve using the Polynomial approximation method, and then the 7th, 8th and 9th order fitting results are compared to see whether the error sum of squares (SSE) is close to 0, the multiple determination coefficient (R-square) is close to 1, the adjusted R-square of the degrees of freedom is close to 1, and the root mean square error (RMSE) is close to 0. Finally, the 9th order fitting with good effects on all parameters is selected.

3. The method for calculating technical line loss based on load curve according to claim 2, characterized in that: In step 5), The calculation formula is: The public variable current I The unit is ampere (A), time t The unit is seconds (s), T One day is 86400 seconds (s); for a three-phase circuit, phases A, B, and C should be calculated separately.

4. The method for calculating technical line loss based on load curve according to claim 3 is characterized in that: In step 6), the terminal voltage ΔU is calculated as , U It is one phase of the three-phase public transformer voltage of the public transformer load. U 0 is one phase of the three-phase voltage of the user load, and the terminal voltages of the remaining two phases of the three-phase are calculated in the same way.

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