A line loss on-line monitoring method of high-voltage transmission line and CVT on-line monitoring device

Abstract

This invention discloses an online monitoring method for line losses in high-voltage transmission lines and an online monitoring device for CVTs, relating to the field of power monitoring system technology. By synchronously acquiring CVT secondary voltage signals and CT secondary current signals at both the beginning and end of the transmission line based on a unified time reference, the method performs real-time error correction processing on the synchronously acquired secondary voltage and current signals, and obtains the real-time ratio error of the CVTs at both ends of the transmission line. This leads to the construction of a statistical line loss acquisition model that uses the active power at the beginning and the real-time ratio error of the CVTs as input. This achieves accurate online sensing and compensation for time-varying CVT errors, effectively solving the problems of traditional methods that cannot adapt to dynamic environmental changes due to the use of fixed error compensation coefficients, and the low accuracy and reliability of line loss calculation results caused by the disconnect between the line loss analysis model and CVT error correction.

Description

Technical Field

[0001] This invention relates to the field of power monitoring system technology, and in particular to a method for online monitoring of line losses in high-voltage transmission lines and an online monitoring device for CVT. Background Technology

[0002] Electricity metering is the cornerstone of economic operation and fair trading in power systems, and its accuracy directly affects the reliability of power grid line loss statistics, energy settlement, and operational efficiency assessment. CVTs (capacitive voltage transformers), as key conversion devices connecting high-voltage transmission networks to metering and protection equipment, bear the important task of accurately converting hundreds of kilovolts of high voltage into standard low voltage. However, the measurement accuracy of CVTs is not constant. Factors such as the nonlinearity of their core magnetization characteristics, the temperature rise effect during operation, the complex characteristics of the insulating medium, and the mechanical stress caused by long-term pressure all contribute to the slow or rapid drift of their ratio and phase errors with operating time and environmental conditions. In high-voltage transmission scenarios, the active power loss of the line itself typically accounts for only 1% to 3% of the transmitted power, falling within the scope of small-signal metering. This means that even small changes in CVT errors can have a significant amplifying effect on line loss calculation results.

[0003] Traditional line loss management methods typically assume constant accuracy of metering transformers or treat error correction and line loss analysis as two independent systems, lacking the ability to online perceive and compensate for the time-varying characteristics of CVT errors. In addition, existing technologies often use fixed compensation coefficients for CVT error compensation, which cannot adapt to dynamic environmental changes. While some solutions improve the efficiency of line loss analysis through AI algorithms, they lack the ability to correct CVT errors in real time. This is especially true in new energy power plants such as wind and solar power, where frequent power fluctuations exacerbate the coupling effect between CVT errors and environmental factors, further increasing the error in line loss analysis. Summary of the Invention

[0004] To overcome the above-mentioned shortcomings of the prior art, the present invention provides a method for online monitoring of line loss in high-voltage transmission lines and an online monitoring device for CVT, aiming to solve the problems of low accuracy and reliability of line loss calculation results caused by the inability of traditional methods to adapt to dynamic environmental changes due to the use of fixed error compensation coefficients, and the disconnect between line loss analysis models and CVT error correction.

[0005] The technical solution adopted by this invention to solve its technical problem is: an online monitoring method for line loss of high-voltage transmission lines, comprising:

[0006] At the beginning and end of the transmission line, based on a unified time reference, the secondary voltage signal of the CVT and the secondary current signal of the CT (current transformer) are synchronously acquired.

[0007] Real-time error correction processing is performed on the synchronously acquired secondary voltage and secondary current signals, and the real-time ratio error of the CVTs at both ends of the transmission line is obtained.

[0008] Based on the corrected starting voltage and current signals, the active power at the starting end of the line is obtained;

[0009] A statistical line loss acquisition model is constructed. The active power at the starting end and the real-time ratio error of the CVT are input into the statistical line loss acquisition model to obtain the statistical line loss value of the transmission line.

[0010] Monitoring data is obtained by attaching time stamps to statistical line loss values ​​and intermediate data. The intermediate data includes at least one of the following: active power at the beginning, real-time ratio error, and voltage and current signals at the beginning and end of the transmission line.

[0011] As a further improvement of the present invention: the unified time reference includes:

[0012] Receive the synchronous clock signal and decode it to generate a synchronous second pulse;

[0013] The timing of data sampling at the beginning and end of the transmission line is controlled by the synchronous second pulse.

[0014] As a further improvement of the present invention, the real-time error correction process includes spectral parameter correction and phase difference correction.

[0015] As a further improvement of the present invention: the spectral parameter correction includes:

[0016] Fast Fourier transform analysis was performed on the acquired secondary voltage and secondary current signals to identify the peak spectral lines of the fundamental component.

[0017] Calculate the frequency correction based on the amplitude of the peak spectral line and its two adjacent spectral lines.

[0018] The frequency, amplitude, and phase of the fundamental component are corrected based on the frequency correction amount.

[0019] As a further improvement of the present invention: the method of obtaining the real-time ratio error of CVT at both ends of the transmission line includes: taking the amplitude of the corrected fundamental component as the accurate amplitude, taking the amplitude of the fundamental component before correction as the reference amplitude, comparing the accurate amplitude with the reference amplitude, and taking their relative deviation as the real-time ratio error of the CVT.

[0020] As a further improvement of the present invention: the phase difference correction includes:

[0021] The initial phase spectrum is obtained by performing a first fast Fourier transform analysis on the same CVT secondary voltage signal.

[0022] After shifting the secondary voltage signal by a known time delay, the fast Fourier transform window length is selected based on the signal frequency change, and a second fast Fourier transform analysis is performed.

[0023] Based on the results of two fast Fourier transform analyses, the corrected phase difference at the fundamental frequency is calculated;

[0024] The fundamental phase measurement value in the initial phase spectrum is calibrated by correcting the phase difference.

[0025] As a further improvement of the present invention: obtaining the active power at the beginning of the line based on the corrected beginning voltage and current signals includes:

[0026] Extract the fundamental components of the secondary voltage of the initial CVT and the fundamental components of the secondary current of the initial CT after real-time error correction.

[0027] The active power at the beginning is calculated based on the phase difference between the corrected fundamental voltage component and the fundamental current component.

[0028] As a further improvement of the present invention: the expression of the statistical line loss acquisition model is:

[0029] ;

[0030] Where y' is the statistical line loss, ε M ε represents the CVT ratio error at the beginning of the line. N denoted as CVT ratio error at the end of the line, x as the transmission power at the beginning of the line, and y as the line loss.

[0031] As a further improvement of the present invention: the expression for the line loss y is:

[0032] ;

[0033] Where x is the transmission power at the beginning of the line, and a, b, and c are the model parameters based on the impedance of the series branches of the line, the admittance to ground, and the voltage amplitude at both ends of the line, respectively.

[0034] This invention also provides a CVT online monitoring device for implementing the aforementioned online monitoring method for line losses in high-voltage transmission lines, comprising a data acquisition module, a monitoring host, a data processing module, and a terminal server, wherein...

[0035] The data acquisition module is set at the metering point of the first and second stations to synchronously acquire the secondary voltage signal of the CVT and the secondary current signal of the CT.

[0036] The monitoring host is used to receive data collected by the data acquisition module.

[0037] The data processing module is used to process and analyze the data received by the monitoring host.

[0038] The time synchronization module, located at the first and second stations, is used to synchronize the time of the data collected by the data acquisition module.

[0039] The terminal server communicates with the monitoring host and is used to receive and store monitoring data transmitted by the monitoring host.

[0040] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the aforementioned method for online monitoring of line losses in high-voltage transmission lines.

[0041] Compared with the prior art, the beneficial effects of the present invention are:

[0042] 1. This invention synchronously acquires voltage and current signals at the beginning and end of a transmission line based on a unified time reference, and performs real-time error correction processing to dynamically obtain the real-time ratio error of the CVTs at both ends. It then constructs a statistical line loss acquisition model that takes the active power at the beginning end and the real-time ratio error of the CVT as input, thereby realizing online accurate perception and compensation of the time-varying error of the CVT. This effectively solves the problems of traditional methods, which cannot adapt to dynamic environmental changes due to the use of fixed error compensation coefficients, and the low accuracy and reliability of line loss calculation results caused by the separation between the line loss analysis model and the CVT error correction.

[0043] 2. This invention controls the sampling timing at different locations by generating synchronous second pulses through decoding IRIG-B codes, ensuring strict spatiotemporal consistency of the data. Furthermore, through adaptive algorithms such as bi-peak interpolation spectrum correction and time-domain phase shift correction, it accurately extracts the fundamental wave parameters of the signal and identifies CVT errors online under complex conditions such as strong electromagnetic interference. The combined effect of these measures provides source data that is time-aligned, accurate in amplitude, and reliable in phase for subsequent calculations, fundamentally overcoming the inherent defects of weak line loss analysis due to data asynchrony and low measurement accuracy, thus ensuring the stability and reliability of the entire monitoring system's output results. Attached Figure Description

[0044] Figure 1 This is a flowchart of an online monitoring method for line loss of a high-voltage transmission line according to the present invention.

[0045] Figure 2 This is a structural block diagram of a CVT online monitoring device according to the present invention.

[0046] Figure 3 This invention relates to a PI-type equivalent current diagram of a high-voltage transmission line online monitoring method for line losses. Detailed Implementation

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be briefly introduced below in conjunction with the accompanying drawings and descriptions of the embodiments or the prior art. Obviously, the following description of the structure of the accompanying drawings is only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0048] It should be understood that the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0049] It should be understood that although the terms first, second, etc., may be used herein to describe various units, these units should not be limited by these terms. These terms are only used to distinguish one unit from another. For example, a first unit may be referred to as a second unit, and similarly, a second unit may be referred to as a first unit, without departing from the scope of the exemplary embodiments of the invention.

[0050] It should be understood that the term "and / or" that may appear in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" that may appear in this document describes another relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " that may appear in this document generally indicates that the related objects before and after it are in an "or" relationship.

[0051] It should be understood that specific details are provided in the following description to facilitate a complete understanding of the exemplary embodiments. However, those skilled in the art will understand that the exemplary embodiments can be implemented without these specific details. For example, the system may be shown in block diagrams to avoid obscuring the example with unnecessary details. In other instances, well-known processes, structures, and techniques may be shown without unnecessary details to avoid obscuring the exemplary embodiments.

[0052] like Figure 1-3 As shown, one embodiment of the present invention provides a method for online monitoring of line losses in high-voltage transmission lines based on a CVT online monitoring device.

[0053] The CVT online monitoring device of the present invention includes a data acquisition module, a monitoring host, a data processing module, a time synchronization module, and a terminal server.

[0054] The data acquisition module is set at the metering points of the first and second stations to synchronously acquire the secondary voltage signal of the CVT and the secondary current signal of the CT. Specifically, the data acquisition module includes a first acquisition unit installed in the outdoor control cabinet for acquiring the secondary voltage signal of the CVT and the secondary current signal of the CT, and a second acquisition unit installed in the metering room for acquiring the secondary voltage signal of the CVT and the secondary current signal of the CT. All acquired information is transmitted via optical fiber.

[0055] The data acquisition module achieves an accuracy of 0.02% in measuring the CVT secondary voltage signal and 0.02% in measuring the CT secondary current signal, with an overall precision preferably of 0.05%. In addition, the data acquisition module needs to be designed to resist electromagnetic interference, which can be achieved by using adaptive filtering technology to eliminate the influence of the strong electromagnetic environment in the substation.

[0056] The monitoring host is used to receive the data collected by the data acquisition module. Specifically, the monitoring host can receive the data collected by the first acquisition unit and the second acquisition unit and perform preliminary processing. It has data caching and anomaly detection functions. The monitoring host has a built-in IRIG-B code (Inter-Range Instrumentation Group-B, an internationally recognized time coding standard) synchronization module, which works with the station's clock synchronization system to ensure that the time synchronization accuracy of the data at each acquisition point is better than 1μs.

[0057] The data processing module is used to process and analyze the data received by the monitoring host. The data processing module adopts spectrum parameter correction technology and phase difference correction technology to improve the accuracy and completeness of data when conventional equipment collects data, thus ensuring the integrity and accuracy of data collection.

[0058] The time synchronization module, installed at each station, is used for data time synchronization. Installed in the computer room, the time synchronization module uses the station-side IRIG-B synchronization clock for decoding, synchronously acquiring the CVT secondary voltage, CT secondary current signals, and metering chamber voltage signals. The data acquisition module uses a 1PPS synchronization pulse to synchronize the sampling pulses of each node. The signals acquired by the synchronized sampling pulses have a unified time reference. Based on this reference, the amplitude and phase angle measured at each node can be directly identified as the actual amplitude and phase angle of that node. Subsequently, these measured values ​​are appended with the corresponding time stamp and transmitted to the data processing module.

[0059] The terminal server is connected to the monitoring host. The monitoring host can transmit monitoring data to the terminal server for storage. Specifically, the monitoring host transmits the data to the station, processes it using the station's time synchronization module and data processing module, and finally transmits the data to the terminal server for storage.

[0060] The time synchronization module includes a receiving unit and a clock unit.

[0061] The receiving unit includes an IRIG-B(DC) second pulse extraction and decoding module. The receiving unit receives the B-code synchronization signal, demodulates and processes it, and outputs a second pulse and NMEA-0183 (Marine Electronic Equipment Format) statement to obtain time, location, and status information. The receiving unit receives two external IRIG-B(DC) fiber optic signals through two fiber optic receivers. The fiber optic receivers convert the optical signals into electrical signals, which are then input to the IRIG-B(DC) second pulse extraction and decoding module. After processing, time and status information are obtained. IRIG-B(DC) and IRIG-B(AC) are two modulation methods unique to the IRIG-B format.

[0062] The clock unit mainly consists of an internal clock frequency source, a signal selection module, a high-precision second pulse generation module, a real-time time counter module, an IRIG-B (DC) encoding module, an IRIG-B (AC) encoding module, and a serial port message encoding module. The high-precision second pulse generation module is the specific implementation of the high-precision second pulse generation scheme.

[0063] The clock unit works as follows: After receiving the external time reference signal, the clock unit selects the external time reference source as the time synchronization source according to the status information decoded by the receiving unit, in order of priority. The selected external time reference signal and the frequency-vibrating second pulse complement each other in terms of error and compensate for the transmission delay, outputting a high-precision second pulse. At the same time, under the synchronization of the second pulse, various time synchronization signals and time information are encoded and output, including pulse signals, IRIG-B (DC) (AC) and serial port time messages.

[0064] If the receiving unit loses the external time reference signal, the clock enters a time-holding state. In this state, the clock maintains a certain level of time accuracy and outputs a time synchronization signal and time information. Once the external time reference signal is restored, the clock unit automatically ends the time-holding state and is pulled into a tracking-locked state by the external time reference signal. During this pulling process, the clock unit continues to output correct time synchronization signals and time information. These time synchronization signals should be error-free, the time information should be error-free, and the pulse codes should be transmitted with minimal or no errors.

[0065] In addition, the server's database system can be initialized and configured to establish a suitable data storage structure and indexes in order to efficiently store and retrieve data.

[0066] Another embodiment of the present invention provides a method for online monitoring of line loss in high-voltage transmission lines, which can be specifically divided into steps S1-S5.

[0067] Step S1: At the beginning and end of the transmission line, based on a unified time reference, the secondary voltage signal of the CVT and the secondary current signal of the CT are synchronously acquired.

[0068] This step aims to address the fundamental problem of inconsistent line loss calculation benchmarks caused by asynchronous data acquisition in existing technologies. Specifically, at two key metering points at the beginning and end of the transmission line, the secondary voltage signals of the capacitive voltage transformer and the secondary current signals of the current transformer must be synchronously triggered and acquired, strictly based on a unified, high-precision time benchmark. This ensures that the data sequences obtained from multiple spatially separated measurement points are perfectly aligned on the time axis, laying a crucial foundation for accurate power calculation and line loss analysis, and fundamentally eliminating calculation errors introduced by timestamp deviations.

[0069] In one specific embodiment, a standard synchronization clock signal, such as the IRIG-B code, is first received from the station's clock synchronization system. This signal is demodulated and processed by a dedicated decoding module to extract a data packet containing absolute time information and ultimately generate a highly stable synchronization second pulse. The rising edge of this second pulse marks the beginning of each UTC (Coordinated Universal Time) second, with extremely high time accuracy, typically with an error better than 1 microsecond. Subsequently, the generated synchronization second pulse is distributed to various data acquisition units deployed at the beginning and end of the line. The internal sampling clocks of these acquisition units are all phase-locked and synchronized based on this second pulse. In actual sampling, the starting point of each sampling interval is strictly triggered and controlled by this synchronization clock.

[0070] In this way, regardless of the location of the acquisition unit, each sampling action of the voltage and current signals occurs on the same absolute time scale, thereby ensuring the strict synchronization of data from all acquisition points. This mechanism effectively overcomes the problem of data time misalignment caused by the drift of crystal oscillators or network delay uncertainties within each acquisition device, ensuring that the power value calculated subsequently can truly reflect the operating status of the power grid at the same instant.

[0071] Step S2: Perform real-time error correction processing on the synchronously acquired secondary voltage and secondary current signals, and obtain the real-time ratio error of the CVTs at both ends of the transmission line.

[0072] In this step, the raw voltage and current signals synchronously acquired in step S1 undergo real-time error correction processing. During this process, the real-time differential error of the CVTs at both ends of the transmission line is dynamically identified and acquired. This step, through digital signal processing algorithms, not only significantly improves the accuracy of basic electrical quantity measurements but, more importantly, enables online monitoring of the metering equipment's operating status. It upgrades error compensation from a static, offline mode to a dynamic, online mode, providing crucial and accurate input parameters for constructing a high-precision line loss model.

[0073] Specifically, real-time error correction processing includes spectral parameter correction and phase difference correction.

[0074] Accurate extraction of the fundamental component based on spectral parameter correction can be achieved by performing a Fast Fourier Transform (FFT) on the acquired discrete signal sequence to initially locate the spectral line corresponding to the fundamental frequency of the power grid. However, due to the difficulty in achieving strict whole-cycle truncation in actual sampling, the picket fence effect can occur, leading to deviations in the measurement of frequency, amplitude, and phase. To address this issue, a bimodal interpolation correction method is employed. This method utilizes the amplitude relationship between the peak spectral line of the fundamental component and its adjacent spectral lines on both sides to accurately calculate the true frequency and the offset of the peak point relative to the discrete spectral line, i.e., the frequency correction. This offset is then used to perform high-precision compensation on the fundamental frequency, amplitude, and phase obtained from the initial FFT analysis. The advantage of this step is that it effectively eliminates the systematic errors caused by asynchronous sampling, obtaining fundamental component amplitude and phase values ​​that approximate theoretical values, providing a high-precision data source for all subsequent calculations.

[0075] To further improve the reliability of phase measurement, especially in dynamic scenarios with rapidly changing signal frequencies, this solution introduces phase difference correction technology. First, an initial phase value is obtained by performing a first Fast Fourier Transform (FFT) analysis on the same voltage signal. Then, the original signal is subjected to a known, precise, and minute time delay, followed by a second FFT analysis. By calculating the phase difference between these two FFT results at the fundamental frequency, a more accurate initial fundamental phase can be deduced. During this process, the window length of the FFT analysis can be adaptively adjusted according to the signal frequency change rate to balance dynamic response speed and measurement accuracy. This self-verification mechanism significantly enhances the anti-interference capability and accuracy of the phase measurement results under dynamic conditions, ensuring the accuracy of the power factor angle in subsequent power calculations.

[0076] After obtaining the accurate amplitude of the fundamental voltage after the above correction, it is regarded as the true value or standard value of the current CVT secondary output. This accurate amplitude is compared with the direct measurement result of the CVT secondary, and the relative deviation between the two is calculated. The calculated relative deviation directly reflects the ratio error of the CVT under the current operating conditions relative to its ideal characteristics, that is, the ratio difference. Through this step, online and real-time measurement of CVT error can be realized, so that line loss analysis can take into account the performance changes of the metering equipment itself. This solves the key defect that the fixed compensation coefficient cannot adapt to the dynamic changes of the environment. In particular, it can effectively deal with the coupling effect of CVT error and operating conditions under the fluctuation of new energy.

[0077] The method for obtaining the real-time ratio error of CVTs at both ends of the transmission line includes: taking the amplitude of the corrected fundamental component as the accurate amplitude, taking the amplitude of the fundamental component before correction as the reference amplitude, comparing the accurate amplitude with the reference amplitude, and taking their relative deviation as the real-time ratio error of the CVT.

[0078] In one specific embodiment, the spectral parameter correction includes the bimodal interpolation method, which compensates for the picket fence effect by interpolating adjacent spectral lines to reduce frequency and phase measurement errors. The principle is to perform interpolation compensation by using the highest spectral line in the main lobe and its adjacent second highest spectral line to correct the frequency / phase deviation caused by non-integer period sampling.

[0079] Frequency correction amount: ;

[0080] in, , These represent the peak spectral line and the amplitude of adjacent spectral lines, respectively, f s Where N is the sampling rate, N is the number of FFT points, k is the index number of the main peak spectral line in the discrete spectrum, X(k) is the complex value of the fast Fourier transform result at index k, and X(k+1) is the complex value of the fast Fourier transform result at index k+1.

[0081] Amplitude correction: ;

[0082] Phase correction: ;

[0083] Furthermore, a ratio correction method based on the characteristics of window functions is proposed, which uses the normalized window spectrum function ratio equation to accurately solve for frequency, amplitude, and phase shift.

[0084] Normalization of the window function creates a function W(f):

[0085] ;

[0086] Solving through iteration Then, work backward to deduce the actual frequency. .

[0087] The reliability of dynamic signal analysis is enhanced by employing time-domain shifting and variable-window-length Fast Fourier Transform, combined with phase difference correction of spectral parameters. The phase difference correction technique steps are as follows:

[0088] Phase difference Calculation formula:

[0089] ;

[0090] in, Let X1(k) and X2(k) be the phase difference, and X1(k) and X2(k) be the Fast Fourier Transform results of the same signal after a time delay τ. Indicates conjugate.

[0091] In variable window length Fast Fourier Transform phase compensation, the window length L is adaptively selected based on the signal frequency change rate df / dt.

[0092] ;

[0093] Where C is an empirical constant, typically taken as 0.1-0.3, f s Where N is the sampling rate, and N is the number of points in the Fast Fourier Transform.

[0094] The correction for phase consistency is expressed as:

[0095] ;

[0096] Where n is the harmonic order and t is the time offset. To correct the phase value, To measure the phase value.

[0097] Step S3: Obtain the active power at the beginning of the line based on the corrected starting voltage and current signals.

[0098] This step uses the high-precision starting voltage and current signals obtained after correction in step S2 to calculate the active power value transmitted at the beginning of the line. It does not use the original signal or the signal that has only been simply filtered, but is based on the fundamental component after precise correction of the spectrum and phase. This ensures that the starting power, which is the core input parameter of the line loss model, has extremely high accuracy and avoids the transmission and amplification of errors in the front-end stage.

[0099] In a specific embodiment, the system accurately extracts two key fundamental physical quantities from the signal data processed in step S2: one is the fundamental component of the secondary voltage from the CVT, whose amplitude and phase have been corrected by the aforementioned correction algorithm to remove measurement system errors; the other is the fundamental component of the secondary current from the CT, whose amplitude and phase have also been corrected with high precision. This ensures that the basic elements used for power calculation are pure and accurate power frequency fundamental quantities, effectively suppressing the influence of interference factors such as harmonics and noise on power calculation, and laying a solid foundation for obtaining the true fundamental active power.

[0100] After obtaining the aforementioned high-precision voltage and current fundamental components, calculations are performed based on fundamental electrical engineering principles. First, the precise phase difference between the voltage and current fundamental components is calculated. Then, using the active power calculation formula, the transmitted active power value at the line's origin is calculated, resulting in a highly reliable origin active power value. This power value, based on precise amplitude and phase measurements, provides a reliable core input for the subsequent line loss calculation model and directly affects the accuracy of the final line loss statistics.

[0101] Step S4: Construct a statistical line loss acquisition model. Use the active power at the starting end and the real-time ratio error of the CVT as the input to the statistical line loss acquisition model to obtain the statistical line loss value of the transmission line.

[0102] The impact of CVT errors at both ends of the line on statistical line loss requires analysis of the variation of statistical line loss with transmission power, taking CVT errors into account. To analyze the variation of statistical line loss with power, it is necessary to first analyze the variation of actual line loss with power.

[0103] PI-type equivalent circuit of transmission lines, such as Figure 3 As shown in the figure, Z=R+jX is the impedance of the series branch of the line, Y1=G1+jB1 and Y2=G2+jB2 are the admittances to ground at both ends of the line (including line capacitance, line conductance and parallel reactance), Z is a lumped parameter, R is the resistance of the transmission line conductor itself, X is the inductive reactance of the transmission line, G1 and G2 represent the active power loss of the insulation medium of the two lines, and B1 and B2 are the capacity effect of the two lines. For the voltage phasors at both ends of the line, For the complex power phasors of each branch, all satisfy the following condition: The subscript k can be replaced with 1 or 2. For the active component of the corresponding complex power, Let j be the reactive component of the corresponding complex power, and j be the imaginary unit.

[0104] As can be seen from the power system analysis, Figure 3 The active power losses in each part are as follows:

[0105] (1)

[0106] (2)

[0107] (3)

[0108] ΔP Z ΔP Y1 ΔP Y2 These are the active power losses of the series branches, the primary-side parallel branches, and the secondary-side parallel branches, respectively. The total line loss is the sum of equations (1), (2), and (3). ,for:

[0109] (4)

[0110] For the series branch containing Z, assuming the power flow direction is from 1 to 2, according to the power angle theorem for power transmission through a line, the active power and reactive power transmitted at the beginning of the line are respectively:

[0111] (5)

[0112] (6)

[0113] In the formula, δ is the power angle by which U1 leads U2, and ρ is the complementary angle of the line impedance angle.

[0114] When the line reactance is much greater than the line resistance, i.e., X >> R, ρ ≈ 0. Assuming that the voltage amplitude on both sides of the line remains unchanged, equations (5) and (6) become:

[0115] (7)

[0116] (8)

[0117] Combining equations (7) and (8), and eliminating the work angle difference δ, we get:

[0118] (9)

[0119] Solving ,have to:

[0120] (10)

[0121] Substituting equation (10) into equation (4), we get:

[0122] (11)

[0123] For ease of writing, let variable x represent the power transmitted at the beginning of the line. Replacing the line loss ΔP with the variable y, the curve of line loss versus transmission power can be simplified as follows, i.e., the expression for the line loss y is:

[0124] (12)

[0125] Where a, b, and c are the model parameters based on the preset impedance of the series branch of the line, the admittance to ground, and the voltage amplitude at both ends of the line, respectively, expressed as:

[0126] (13)

[0127] In the above formula, a is a coefficient related to the power factor, b is the line power transmission limit, and C is the line loss at the power transmission limit.

[0128] Equation (13) First equation is considered in the case of three-phase symmetry. The vector symbol in the equation is removed, the vector dot product is replaced by scalar multiplication, the statistical line loss ΔP' is replaced by the variable y', the transmission power PM at the beginning of the line is replaced by the variable x, and the line loss ΔP is replaced by y:

[0129] (14)

[0130] From equations (12) and (14), we can obtain:

[0131] (15)

[0132] The above formula represents the statistical line loss variation with the power transmitted from the starting end, taking into account the CVT error at both ends of the line when the line power is transmitted from the M side to the N side.

[0133] Where y' is the statistical line loss, ε M The error ε represents the CVT error at the beginning of the line. N y is the CVT error at the end of the line, x is the transmission power at the beginning of the line, y is the line loss, and a, b, and c have the same meaning as in equation (13).

[0134] Step S5: Add time stamps to the statistical line loss values ​​and intermediate data to obtain monitoring data.

[0135] This step binds and encapsulates the key result data obtained from the previous steps, mainly the statistical line loss value, with the relevant source data and time stamps to generate standardized monitoring data records, which are then output and stored. This process enables the extraction of value and integration of information from the raw signal to the final analysis result, ensuring the integrity and traceability of the data chain. It provides directly usable, semantically rich structured data for upper-level applications such as energy management systems, historical databases, and alarm platforms.

[0136] The intermediate data includes active power at the starting end, real-time ratio error, and voltage and current signals at the beginning and / or end of the transmission line. Alternatively, it can be a set of key parameters, source data, and status indicators necessary for using the line loss value. In addition to the above, analysis models can be set to analyze real-time monitoring data and achieve functions such as status early warning.

[0137] Another embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the aforementioned method for online monitoring of line losses in high-voltage transmission lines.

[0138] The functions described herein can be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions can be stored as one or more instructions or codes on or transmitted via a computer-readable medium. Other examples and embodiments are within the scope and spirit of this invention and the appended claims. For example, due to the nature of software, the functions described above can be implemented using software executed by a processor, hardware, firmware, hardwired, or any combination thereof. Furthermore, the functional units can be integrated into a single processing unit, or each unit can exist physically separately, or two or more units can be integrated into a single unit.

[0139] The units described as separate components may or may not be physically separate. Similarly, the components of the control device may or may not be physical units; they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0140] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory, random access memory, portable hard drives, magnetic disks, or optical disks.

[0141] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for online monitoring of line losses in high-voltage transmission lines, characterized in that: include: At the beginning and end of the transmission line, the secondary voltage signal of the CVT and the secondary current signal of the CT are synchronously acquired based on a unified time reference. Real-time error correction processing is performed on the synchronously acquired voltage and current signals, and the real-time ratio error of the CVTs at both ends of the transmission line is obtained. Based on the corrected voltage and current signals at the starting end, the active power at the starting end of the line is obtained. A statistical line loss acquisition model is constructed. The active power at the starting end and the real-time ratio error of the CVT are input into the statistical line loss acquisition model to obtain the statistical line loss value of the transmission line. The monitoring data is obtained by attaching time stamps to the statistical line loss values ​​and intermediate data. The intermediate data includes at least one of the following: active power at the beginning, real-time ratio error, and voltage and current signals at the beginning and end of the transmission line. The real-time error correction process includes spectral parameter correction and phase difference correction; The spectral parameter correction includes: Fast Fourier transform analysis was performed on the acquired secondary voltage and secondary current signals to identify the peak spectral lines of the fundamental component. Calculate the frequency correction based on the amplitude of the peak spectral line and its two adjacent spectral lines. Based on the frequency correction amount, the frequency, amplitude, and phase of the fundamental component are corrected; The method of obtaining the real-time ratio error of CVT at both ends of the transmission line includes: taking the amplitude of the corrected fundamental component as the accurate amplitude, taking the amplitude of the fundamental component before correction as the reference amplitude, comparing the accurate amplitude with the reference amplitude, and taking their relative deviation as the real-time ratio error of the CVT. The expression for the statistical line loss acquisition model is: ； Where y' is the statistical line loss, ε M ε represents the CVT ratio error at the beginning of the line. N y is the CVT ratio difference error at the end of the line, x is the transmission power at the beginning of the line, and y is the line loss. The expression for the line loss y is: ； Where x is the transmission power at the beginning of the line, and a, b, and c are the model parameters based on the impedance of the series branches of the line, the admittance to ground, and the voltage amplitude at both ends of the line, respectively.

2. The method for online monitoring of line losses in high-voltage transmission lines as described in claim 1, characterized in that: The unified time base includes: Receive the synchronous clock signal and decode it to generate a synchronous second pulse; The timing of data sampling at the beginning and end of the transmission line is controlled by the synchronous second pulse.

3. The method for online monitoring of line losses in high-voltage transmission lines as described in claim 1, characterized in that: The phase difference correction includes: The initial phase spectrum is obtained by performing a first fast Fourier transform analysis on the same CVT secondary voltage signal. After shifting the secondary voltage signal by a known time delay, the fast Fourier transform window length is selected based on the signal frequency change, and a second fast Fourier transform analysis is performed. Based on the results of two fast Fourier transform analyses, the corrected phase difference at the fundamental frequency is calculated; The fundamental phase measurement value in the initial phase spectrum is calibrated by correcting the phase difference.

4. The method for online monitoring of line losses in high-voltage transmission lines as described in claim 1, characterized in that: The step of obtaining the active power at the beginning of the line based on the corrected voltage and current signals at the beginning includes: Extract the fundamental components of the secondary voltage of the initial CVT and the fundamental components of the secondary current of the initial CT after real-time error correction. The active power at the beginning is calculated based on the phase difference between the corrected fundamental voltage component and the fundamental current component.

5. A CVT online monitoring device, characterized in that: A method for online monitoring of line losses in high-voltage transmission lines as described in any one of claims 1-4, comprising a data acquisition module, a monitoring host, a data processing module, and a terminal server, wherein, The data acquisition module is set at the metering point of the first and second stations to synchronously acquire the secondary voltage signal of the CVT and the secondary current signal of the CT. The monitoring host is used to receive data collected by the data acquisition module. The data processing module is used to process and analyze the data received by the monitoring host. The time synchronization module, located at the first and second stations, is used to synchronize the time of the data collected by the data acquisition module. The terminal server communicates with the monitoring host and is used to receive and store monitoring data transmitted by the monitoring host.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that: When executed by a processor, the computer program implements a method for online monitoring of line losses in high-voltage transmission lines as described in any one of claims 1-4.

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