A method for calculating the output data of a primary current transformer

Abstract

This invention belongs to the field of power system power grid operation technology, and relates to a method for calculating the output data of a primary transformer. The method involves setting and loading constant parameter data, establishing a calculation model for the input phase angle and frequency changes of the primary transformer, establishing a calculation model for the output data of the primary transformer, starting a timer in the program module, and cyclically checking whether the frequency change period of f has reached the set time. If so, the calculation model is assigned to calculate the input phase angle and frequency changes of the primary transformer, as well as the output data of the primary transformer. Finally, in chronological order, multiple sets of five output data for the primary transformer are generated and displayed on the computer screen. The five output data are: output voltage and output phase angle of the primary voltage transformer, output current and output phase angle of the primary current transformer, and frequency. This invention saves on-site sampling costs, improves work efficiency, and allows for early detection of faults or damage to primary transformers.

Description

Technical Field

[0001] This invention belongs to the field of power system power grid operation technology, and specifically relates to a method for calculating the output data of a primary transformer. Background Technology

[0002] The primary transformer in a power system, also called an instrument transformer, is a general term for primary voltage transformers and primary current transformers. Its main function is to convert high voltage or high current in the power system into standard low voltage (100V) or standard low current (1A or 5A) signals according to the transformation ratio of the primary transformer, so as to facilitate the acquisition and measurement of measuring instruments, protection equipment and automatic control equipment.

[0003] A large number of primary instrument transformers exist within the power grid, allowing for the sampling and monitoring of data such as voltage, current, and frequency. The output data of primary instrument transformers mainly includes voltage, current, phase angle, and frequency. Voltage, current, and frequency are primarily obtained through actual sampling by the equipment, while the phase angle is mainly calculated. Currently, the commonly used method for phase angle calculation is the vector method, which uses the voltage vector in the AC circuit. Divide by current vector Obtain the impedance Z:

[0004]

[0005] In the formula, the real part is R = (ac + bd), the imaginary part is X = (bc - ad), and j is the complex unit; therefore, the formula can be transformed into:

[0006]

[0007] in

[0008] This is the famous Euler formula, where e is the natural constant and j is the complex unit; the phase angle δ = arctan X / R, that is, the phase angle δ is obtained by using the arctangent function.

[0009] Current vector-based methods for calculating phase angles have the following four main shortcomings:

[0010] 1. Narrow applicability, mainly for sinusoidal AC circuits. For nonlinear components, the accuracy of data will be affected when the AC power supply changes significantly.

[0011] 2. The data processing volume is large, requiring continuous sampling and calculation within one cycle, resulting in a large amount of data processing.

[0012] 3. It is not conducive to data precision calculation, and the complex number calculation process will cause precision loss;

[0013] 4. It cannot describe the change process of the phase angle from 0 to the normal value because it is calculated through vector voltage and current, and can only reflect the data value when the sampling is correct. Summary of the Invention

[0014] To address the aforementioned technical problems, this invention provides a method for calculating the output data of a primary current transformer, proposing a calculation formula and method for the output data of the primary current transformer, as well as a method for calculating the input phase angle and frequency changes of the primary current transformer. The technical solution adopted by this invention is as follows:

[0015] A method for calculating the output data of a primary current transformer involves setting up a program module in a computer to calculate the output data of the primary current transformer. The program module includes a timer, and the execution steps of the program module are as follows:

[0016] S1: Set and load constant parameter data, which includes, but is not limited to: phase angle difference, ratio difference, and transformation ratio. Phase angle difference, ratio difference, and transformation ratio are the most commonly used constant parameters. The values ​​of these constant parameters are provided by the primary transformer and are usually marked on the nameplate of the primary voltage transformer / primary current transformer.

[0017] S2: Establish two calculation models: a calculation model for the input phase angle and frequency changes of the primary transformer, and a calculation model for the output data of the primary transformer.

[0018] The computational model is established through computational formulas, which involve digitizing, storing, and serializing the computational formulas. Various variables and parameters related to the computational formulas are directly input into the computational model to obtain the computational results. The computational formulas are stored in a database, and the computational model reads the database to parse the computational formulas.

[0019] The calculation model for the input phase angle and frequency variation of the primary transformer includes: the input phase angle δ of the primary voltage transformer in radians. tu(弧度) Calculation model, primary voltage transformer input phase angle δ in degrees tu(角度) The calculation model and the input phase angle δ of the primary current transformer in radians. ti(弧度) The calculation model and the input phase angle δ of the primary current transformer in degrees. ti(角度) Computational model.

[0020] The input phase angle δ of a primary voltage transformer, measured in radians. tu(弧度) Computational model:

[0021] δ tu(弧度) =δ (t-1)u(弧度) +(f t -50)*2π;

[0022] The formula is derived from the sine wave phase angle calculation formula δ=2πf+α, where f is the frequency and α is the initial phase angle; since the frequency is now changing, therefore (f t -50)*2π represents the frequency of change f. t The phase difference at each moment, plus the input phase angle δ in radians from the previous moment. (t-1)u(弧度) That is, to obtain the input phase angle δ in radians at the current moment. tu(弧度) ;δ tu(弧度) The initial value (that is, the value at time t0) is 0;

[0023] The input phase angle δ of the primary voltage transformer is measured in degrees. tu(角度) Computational model:

[0024] δ tu(角度) =(δ tu(弧度) *180) / π.

[0025] The input phase angle δ of a primary current transformer, measured in radians. ti(弧度) Computational model:

[0026] δ ti(弧度) =δ (t-1)i(弧度) +(f t -50)*2π-Φ0*π / 180;

[0027] The basic principle of the formula is the same as that of the primary voltage transformer formula. The difference is that in the primary current transformer, (f t -50)*2π-Φ0*π / 180 represents the frequency of change f. t The phase difference at any given moment; Φ0 represents the angle between the bus voltage and current, which is the initial setting value. δ ti(弧度) The initial value (that is, the value at time t0) is 0;

[0028] The input phase angle δ of a primary current transformer is measured in degrees. ti(角度) Computational model:

[0029] δ ti(角度) =(δ ti(弧度) *180) / π.

[0030] The calculation model for the primary transformer output data includes a calculation model for the primary voltage transformer output data and a calculation model for the primary current transformer output data.

[0031] Calculation model for primary voltage transformer output data:

[0032] Output voltage

[0033] Where: U0 represents the effective value of the input voltage; e represents the ratio difference of the primary voltage transformer; x represents the transformation ratio of the primary voltage transformer; cos represents the power factor;

[0034] Φ 2U This represents the output phase angle of a primary voltage transformer, expressed in degrees.

[0035] Φ 2U =(δ tu(弧度) +gπ / 10800)*180 / π;

[0036] δ tu(弧度) The input phase angle of the primary voltage transformer, expressed in radians, is the input phase angle value of the primary voltage transformer, which changes with the frequency f. g represents the phase angle difference of the primary voltage transformer.

[0037] Calculation model for primary current transformer output data:

[0038] Output current

[0039] Where: I0 represents the effective value of the input current; q represents the ratio difference of the primary current transformer; y represents the transformation ratio of the primary current transformer;

[0040] Φ 2I This represents the output phase angle of a primary current transformer, expressed in degrees.

[0041] Φ 2I =(δ ti(弧度) +hπ / 10800)*180 / π;

[0042] δ ti(弧度) The input phase angle of the primary current transformer, expressed in radians, is the value of the input phase angle of the primary current transformer, expressed in radians, which changes with the frequency f. h represents the phase angle difference of the primary current transformer.

[0043] S3: Start the timer in the program module to cyclically check if the frequency f has reached the set time. The set time can be manually set, with a default of 1 second. The timer is a millisecond timer. Initially, the start time for recording frequency f is t1, and in each cycle, the current time when frequency f changes is t2. When the time difference (t2-t1) ≥ the set time, the calculation model performs the following calculations for the primary transformer input phase angle and frequency change, as well as the primary transformer output data.

[0044] S3.1 Calculation of the input phase angle and frequency change of the primary current transformer. The specific calculation steps are as follows:

[0045] The first step is to obtain the frequency f variation data, which ranges from 49.95 to 50.05. There are three modes of frequency f variation:

[0046] - The step value and step direction vary randomly;

[0047] - The step direction first changes towards the maximum value of 50.05, and after reaching the maximum value of 50.05, it changes towards the minimum value of 49.95, and so on; the step value is 0.01;

[0048] - The step direction first changes towards the minimum value of 49.95, and after reaching the minimum value of 49.95, it changes towards the maximum value of 50.05, and so on; the step value is 0.01;

[0049] The second step is to use the calculation model of the input phase angle and frequency change of the primary transformer in S2 to calculate the input phase angle values ​​of the primary voltage transformer and the primary current transformer respectively.

[0050] S3.2 Calculation of primary transformer output data.

[0051] Using the calculation model of the primary transformer output data in S2, calculate the output voltage U and output phase angle Φ of the primary voltage transformer respectively. 2U The output current I and output phase angle Φ of the primary current transformer 2I At the same time, there is also the calculation of related intermediate data.

[0052] S4: Finally, in chronological order, five sets of output data from the primary current transformers are generated and displayed on the computer screen. The five output data are as follows:

[0053] The primary voltage transformer output voltage U;

[0054] The primary current transformer outputs current I;

[0055] Primary voltage transformer output phase angle Φ 2U ;

[0056] The output phase angle Φ of the primary current transformer 2I ;

[0057] Frequency f.

[0058] This invention sets the ratio difference and phase angle of the primary transformer as fixed parameters, and combines them with other input variables to calculate the changes in the output voltage, current, output phase angle, and frequency of the primary transformer according to a specific algorithm. These changes are generated regularly, in large quantities, and in groups. By analyzing these changes, the actual operating conditions of the primary transformer can be effectively predicted, and faults or damage to the primary transformer can be detected early, providing strong data support for the safe and stable operation of the power grid.

[0059] The beneficial effects of this invention are:

[0060] This invention uses specific formulas and algorithms to simulate and generate five typical data points for primary voltage / current transformers in a power system, and records and saves these data according to timestamps. 1) No on-site data collection is required; the formula algorithm generates a large number of regular, grouped typical data samples of five primary transformers, saving on-site sampling costs and improving work efficiency. 2) By analyzing these generated typical data points of primary transformers, different primary transformer models are formed, which can detect whether primary transformers have faults or damage at an early stage, providing strong data support for the safe and stable operation of the power grid. Attached Figure Description

[0061] Figure 1 This is a flowchart of a method for calculating the output data of a primary transformer according to an embodiment of the present invention. Detailed Implementation

[0062] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0063] like Figure 1 The diagram shown is a flowchart of a method for calculating the output data of a primary current transformer according to an embodiment of the present invention. A method for calculating the output data of a primary current transformer includes the following steps:

[0064] Step 1: Load constant parameter data such as phase angle difference, ratio difference, and turns ratio;

[0065] Step 2: Establish a calculation model for the input phase angle and frequency changes of the primary transformer, and establish a calculation model for the output data of the primary transformer;

[0066] Step 3: Determine whether the frequency change period has reached the timing time. In this embodiment, the timing time is 2 seconds by default. If yes, proceed to the next step; otherwise, repeat step 3.

[0067] Step 4: Calculation of the input phase angle and frequency changes of the primary transformer.

[0068] Take the frequency of change value and the input phase angle value from the previous moment.

[0069] Assign values ​​to the computational model and perform the calculation.

[0070] Output the calculated phase angle value in radians.

[0071] Output the calculated phase angle value in degrees.

[0072] and,

[0073] Calculation of primary transformer output data

[0074] Calculations are performed using the effective value of voltage and parameter data, and calculations are performed using the effective value of current and parameter data.

[0075] The power factor value is calculated by introducing the input phase angle value.

[0076] Assign a value to the primary voltage transformer output data calculation model to calculate the primary voltage transformer output voltage and output phase angle; assign a value to the primary current transformer output data calculation model to calculate the primary current transformer output current and output phase angle.

[0077] Step 5: Finally, in chronological order, generate five sets of output data for the primary transformers: output voltage and phase angle of the primary voltage transformer, output current and phase angle of the primary current transformer, and frequency f.

[0078] This invention proposes an algorithm for calculating the output voltage, current, and phase angle of a primary transformer in a power system using ratio differences and phase angle differences. This addresses the problems of insufficient accuracy and limited data quality resulting from relying solely on actual sampling of primary transformer data. The algorithm primarily employs specific formulas and algorithms to solve these issues. Examples of specific implementation methods are provided below:

[0079] I. Example of primary voltage transformer parameters.

[0080] The parameters of the primary voltage transformer are shown in the table below:

[0081]

[0082]

[0083] II. Example of primary current transformer parameters.

[0084] The parameters of the primary current transformer are shown in the table below:

[0085]

[0086]

[0087]

[0088] III. Calculation example of input phase angle and frequency change of primary voltage transformer.

[0089] The change in frequency f and the input phase angle δ tu(弧度) The data generation formula is:

[0090] δ tu(弧度) =δ (t-1)u(弧度) +(f t-50)*2π;

[0091] The frequency data for the time series is generated as f, which changes once per second according to three modes, generating a total of t time-series data points. The initial phase angle δ0 is a preset value of 0. Then:

[0092] δ1=δ0+(f1-50)*2π,

[0093] δ2=δ1+(f2-50)*2π,

[0094] ...

[0095] δ t =δ t-1 +(f t -50)*2π.

[0096] The frequency f changes once per second between 49.95Hz and 50.05Hz, and the following example data would be provided:

[0097] t=0, δ0=0, f1=50, δ1=0,

[0098] When t=1, δ1=0, f2=50, δ2=0,

[0099] When t=2, δ2=0π, f3=50.01, δ3=0.02π,

[0100] When t=3, δ3=0.02π, f4=50.01, δ4=0.04π,

[0101] When t=4, δ4=0.04π, f5=50.02, δ5=0.08π,

[0102] When t=5, δ5=0.08π, f6=50.02, δ6=0.12π.

[0103] The present invention has the following key points and features:

[0104] 1) Derivation and calculation process of the formula for the output data of the primary voltage transformer;

[0105] 2) Derivation and calculation process of the formula for the output data of the primary current transformer;

[0106] 3) The derivation and calculation process of the relationship between the input phase angle and frequency change of the primary transformer.

[0107] In the embodiments of the present invention, all technical features not described in detail are existing technologies or conventional technical means, and will not be repeated here.

[0108] Finally, it should be noted that the above embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit them. The scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention.

Claims

1. A method for calculating the output data of a primary current transformer, comprising installing and running a program module for calculating the output data of a primary current transformer in a computer, wherein the program module includes a timer, characterized in that, The execution steps of the program module are as follows: S1: Set and load constant parameter data, which includes, but is not limited to: phase angle difference, ratio difference, and transformation ratio; S2: Establish two calculation models: a calculation model for the input phase angle and frequency changes of the primary transformer, and a calculation model for the output data of the primary transformer. The calculation model for the input phase angle and frequency variation of the primary transformer includes: the input phase angle δ of the primary voltage transformer in radians. tu（弧度） Calculation model, primary voltage transformer input phase angle δ in degrees tu（角度） The calculation model and the input phase angle δ of the primary current transformer in radians. ti（弧度） The calculation model and the input phase angle δ of the primary current transformer in degrees. ti（角度） Computational model; The input phase angle δ of a primary voltage transformer, measured in radians. tu（弧度） Computational model: δ tu（弧度） =δ (t-1)u（弧度） +(ft-50)×2π; (ft-50)×2π represents the frequency of change f. t Phase difference at time δ tu（弧度） The initial value is 0; The input phase angle δ of the primary voltage transformer is measured in degrees. tu（角度） Computational model: d tu（角度） =(δ tu（弧度） ×180) / π; The input phase angle δ of a primary current transformer, measured in radians. ti（弧度） Computational model: d ti（弧度） =d （t-1）i（弧度） +(f t -50)×2π-Φ0×π / 180; (f t -50)×2π-Φ0×π / 180 represents the frequency of change f. t The phase difference at any given moment; Φ0 represents the angle between the bus voltage and current, which is the initial setting value, δ ti（弧度） The initial value is 0; The input phase angle δ of a primary current transformer is measured in degrees. ti（角度） Computational model: d ti（角度） =(δ ti（弧度） ×180) / π; The calculation model for the primary transformer output data includes a calculation model for the primary voltage transformer output data and a calculation model for the primary current transformer output data; Calculation model for primary voltage transformer output data: Output voltage U= , Where: U0 represents the effective value of the input voltage; e represents the ratio difference of the primary voltage transformer; x represents the transformation ratio of the primary voltage transformer; cos represents the power factor; Φ 2U This represents the output phase angle of a primary voltage transformer, expressed in degrees. F 2U =(δ tu（弧度） +gπ / 10800)×180 / π; g represents the phase angle difference of the primary voltage transformer; Calculation model for primary current transformer output data: Output current I= ; Where: I0 represents the effective value of the input current; q represents the ratio difference of the primary current transformer; y represents the transformation ratio of the primary current transformer; Φ 2I This represents the output phase angle of a primary current transformer, expressed in degrees. F 2I =(δ ti（弧度） +hπ / 10800)×180 / π; h represents the phase angle difference of the primary current transformer; S3: Start the timer in the program module, and continuously check whether the frequency f change period has reached the timing time. If so, assign the calculation model to perform one calculation of the transformer input phase angle and frequency change, and one calculation of the transformer output data. S4: Finally, in chronological order, generate multiple sets of five output data points from the primary transformers and display them on the computer screen. The five output data points are: primary voltage transformer output voltage U, primary current transformer output current I, and primary voltage transformer output phase angle Φ. 2U The output phase angle Φ of the primary current transformer 2I and frequency f; The specific calculation steps in step 3 are as follows: S3.1 Calculation of input phase angle and frequency changes of primary current transformer: The first step is to obtain the frequency f variation data, which ranges from 49.95 to 50.

05. There are three modes of frequency f variation: - The step value and step direction vary randomly; - The step direction first changes towards the maximum value of 50.05, and after reaching the maximum value of 50.05, it changes towards the minimum value of 49.95, and so on; the step value is 0.01; - The step direction first changes towards the minimum value of 49.95, and after reaching the minimum value of 49.95, it changes towards the maximum value of 50.05, and so on; the step value is 0.01; The second step is to use the calculation model of the input phase angle and frequency change of the primary transformer in S2 to calculate the input phase angle values ​​of the primary voltage transformer and the primary current transformer respectively. S3.2 Calculation of primary transformer output data; Using the calculation model of the primary transformer output data in S2, calculate the output voltage U and output phase angle Φ of the primary voltage transformer respectively. 2U The output current I and output phase angle Φ of the primary current transformer 2I At the same time, there is also the calculation of related intermediate data.

2. The method for calculating the output data of a primary current transformer according to claim 1, characterized in that, The establishment of a computational model is achieved through computational formulas. This involves digitizing, storing, and serializing the computational formulas, and directly inputting the variables and parameters related to the computational formulas into the computational model to obtain the computational results. The calculation formulas are stored in the database, and the calculation model reads the database to parse the calculation formulas.

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