A method and system for monitoring DC ice-melting operation of a power transmission line

Abstract

The application provides a power transmission line DC ice melting operation monitoring method and system, and relates to the technical field of power system automatic control, which comprises the following steps: collecting voltage signals and current signals output by a DC ice melting power supply; extracting characteristic components from the voltage signals and the current signals; calculating line impedance parameters based on the characteristic components; inverting the temperature and sag of the power transmission line according to the line impedance parameters; and adjusting the output current of the DC ice melting power supply according to the temperature and sag of the power transmission line. The application uses the output signals of the DC ice melting power supply as a measurement source, does not need to install sensors on the line, is not limited by severe weather conditions, realizes real-time online monitoring of the line temperature and sag, can automatically adjust the ice melting current, effectively prevents the line from being damaged due to overheating, and improves the automation level and safety of the ice melting operation.

Description

Technical Field

[0001] This invention relates to the field of power system automation control technology, specifically to a method and system for monitoring DC de-icing operations on transmission lines. Background Technology

[0002] Currently, in DC de-icing operations on power transmission lines, it is typically necessary to measure parameters such as line temperature and sag to monitor the condition of the iced line during the de-icing process, and then control and adjust the output current of the DC de-icing power supply accordingly. Existing measurement methods mainly include installing contact sensors (such as temperature sensors and tension sensors) on the line or using drones equipped with infrared thermal imagers and lidar for measurement. However, contact sensors require pre-installation, making it impossible to monitor lines without sensors, and the strong electromagnetic environment of high-voltage transmission lines can easily interfere with sensor operation, affecting measurement accuracy. Drone inspection is heavily limited by weather conditions, unable to take off or operate safely in severe weather such as strong winds and heavy fog, resulting in the inability to obtain data at the critical moment when monitoring is most needed. In addition, existing de-icing power supply control largely relies on manual adjustments based on measurement data, which has a time lag and may lead to line overheating and damage. Therefore, there is an urgent need for a technical solution that can monitor the line status in real time and automatically control the de-icing current without the need for external sensors in harsh environments. Summary of the Invention

[0003] To address the problems of existing technologies that rely on external sensors or drones for monitoring the status of DC de-icing operations on transmission lines, which suffer from issues such as inability to monitor without sensors, inaccurate measurements due to strong electromagnetic interference, inability to operate in severe weather, and the tendency for manual adjustment of the de-icing current to cause overheating and damage to the lines, this application proposes a method and system for monitoring DC de-icing operations on transmission lines. This method utilizes the output signal of the DC de-icing power supply itself for impedance calculation and status inversion, achieving real-time monitoring and automatic control without the need for external sensors.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for monitoring DC de-icing operations on transmission lines includes: acquiring voltage and current signals output by a DC de-icing power supply; extracting characteristic components from the voltage and current signals; calculating line impedance parameters based on the characteristic components; retrieving the temperature and sag of the transmission line based on the line impedance parameters; and adjusting the output current of the DC de-icing power supply based on the temperature and sag of the transmission line.

[0005] Preferably, the characteristic components include a DC component and a characteristic frequency component; wherein, the characteristic frequency component is the inherent harmonic component of the DC de-icing power supply; the DC component is used to calculate the line resistance, and the characteristic frequency component is used to calculate the line reactance.

[0006] Preferably, the step of extracting feature components from the voltage and current signals includes: performing a fast Fourier transform on the voltage and current signals to obtain spectrum data; extracting the amplitude of the DC component from the spectrum data to obtain DC voltage and DC current; and extracting the amplitude and phase of the harmonic components from the spectrum data to obtain harmonic voltage and harmonic current.

[0007] Preferably, the step of calculating the line impedance parameters based on the characteristic components and inverting the temperature and sag of the transmission line based on the line impedance parameters includes: calculating the line resistance based on the DC component and inverting the temperature of the transmission line based on the line resistance; calculating the line reactance based on the characteristic frequency component and inverting the sag of the transmission line based on the line reactance.

[0008] Preferably, the step of calculating the line resistance based on the DC component and inverting the transmission line temperature based on the line resistance includes: calculating the line DC resistance based on the DC component; and calculating the transmission line temperature based on the temperature coefficient of resistance of the conductor material and the ratio of the line DC resistance to a reference resistance at a reference temperature.

[0009] Preferably, the step of calculating the line reactance based on the characteristic frequency components and inverting the sag of the transmission line based on the line reactance includes: calculating the line reactance based on the characteristic frequency components; calculating the average height of the transmission line to the ground based on the line reactance and the relationship between the line inductance and the average height to ground; and calculating the sag of the transmission line based on the average height to ground and the height of the line suspension point.

[0010] Preferably, adjusting the output current of the DC de-icing power supply based on the temperature and sag of the transmission line obtained from the inversion includes: reducing the output current of the DC de-icing power supply when the temperature of the transmission line exceeds a preset temperature threshold; reducing the output current of the DC de-icing power supply when the temperature change rate of the transmission line exceeds a preset change rate threshold; maintaining the output current of the DC de-icing power supply unchanged when the sag change rate of the transmission line is less than or equal to zero; and reducing the output current of the DC de-icing power supply until it stops outputting when the sag change rate of the transmission line is greater than zero.

[0011] Furthermore, the present invention also provides a DC de-icing operation monitoring system for transmission lines, comprising: a DC de-icing power supply configured to output de-icing current to the transmission line; a measurement unit connected to the DC de-icing power supply configured to acquire voltage and current signals output by the DC de-icing power supply; a processing unit communicatively connected to the measurement unit configured to extract feature components from the voltage and current signals, calculate line impedance parameters based on the feature components, and invert the temperature and sag of the transmission line according to the line impedance parameters; and a controller connected to the processing unit and the DC de-icing power supply configured to adjust the output current of the DC de-icing power supply according to the inverted temperature and sag of the transmission line.

[0012] Preferably, the measuring unit includes a voltage sensor and a current sensor; the voltage sensor is configured to acquire the voltage signal output by the DC de-icing power supply; and the current sensor is configured to acquire the current signal output by the DC de-icing power supply.

[0013] Preferably, the processing unit includes a data acquisition card and a processor; the data acquisition card is configured to sample the voltage signal and the current signal; the processor is configured to perform the operations of extracting feature components from the voltage signal and the current signal, calculating line impedance parameters, and inverting the temperature and sag of the transmission line.

[0014] Beneficial effects: This invention utilizes the voltage and current signals output by a DC de-icing power supply as the measurement signal source, eliminating the need for additional sensors or measuring devices on the transmission line to acquire the line's impedance parameters in real time. Since the DC de-icing power supply operates invariably during de-icing operations, this method is unaffected by adverse weather conditions (such as strong winds or heavy fog), solving the problems of drones being unable to take off or sensors malfunctioning due to electromagnetic interference in existing technologies. By extracting the DC component and characteristic frequency components from the signal, the line resistance and reactance are calculated separately, and then the line temperature and sag are inverted, achieving real-time, online monitoring of the de-icing line's condition. Based on the real-time monitored temperature and sag parameters, the output current of the DC de-icing power supply is automatically adjusted, effectively preventing line overheating damage caused by current adjustment lag, thus improving the automation level and safety of de-icing operations. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the DC de-icing operation monitoring system for power transmission lines according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the DC ice-melting power supply impedance measurement circuit according to an embodiment of the present invention; Figure 3 This is a simplified schematic diagram of the impedance measurement principle of the DC de-icing circuit according to an embodiment of the present invention; Figure 4 This is a flowchart of the DC de-icing operation monitoring and control method for transmission lines according to an embodiment of the present invention; Figure 5 This is a waveform diagram of the DC ice-melting operation voltage and current signals according to an embodiment of the present invention; Figure 6 This is a voltage and current spectrum diagram of DC ice melting operation according to an embodiment of the present invention; The components include: 1. DC de-icing power supply; 2. Measurement unit; 3. Processing unit; 4. Controller; and 5. Icing circuit. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0018] Example 1: This example provides a method for monitoring DC de-icing operations on transmission lines. The core concept of this method lies in "multiplexing power supply signals," that is, using the output signal naturally generated by the DC de-icing power supply during operation as the measurement excitation source, thereby achieving the perception of the line status without adding additional hardware sensors. Figure 4 As shown, the method specifically includes the following steps: Step S100: Collect the voltage and current signals output by the DC de-icing power supply.

[0019] Specifically, this embodiment overcomes the limitations of traditional technologies that require additional temperature sensors to be installed on the line or rely on drone inspections. When the DC de-icing power supply is running, its output itself contains rich information reflecting the line characteristics. By setting a measurement point at the power supply output, raw voltage and current waveform data, including DC and harmonic components, can be directly acquired. This acquisition method is completely unaffected by external weather conditions (such as heavy fog, strong winds, rain, or snow) because the signal transmission path is located inside the electrical connection circuit, not in open atmospheric space. It should be understood that although this embodiment describes the acquisition of signals from the power supply output, in actual engineering applications, the acquisition point can be set at any location in the de-icing circuit, as long as the current flowing through the line and the voltage drop across the line can be obtained.

[0020] Step S200: Extract feature components from the voltage signal and the current signal.

[0021] Specifically, the output of a DC de-icing power supply (especially one employing a rectifier circuit) is not pure DC, but a composite signal containing a DC component and a series of specific frequency harmonic components. This step involves performing frequency or time domain analysis on the acquired raw signal to separate the "characteristic components" useful for subsequent calculations. For example, for a power supply using a 6-pulse rectifier circuit, its characteristic components typically include a DC component and higher-order harmonic components with frequencies 6 times, 12 times, etc., of the fundamental frequency. These characteristic components effectively act as "probes" to detect the line's condition, with the DC component primarily reflecting the line's resistance characteristics and the harmonic components primarily reflecting the line's reactance characteristics. By multiplexing these frequency components generated by the power supply itself, this invention eliminates the need for additional probe signals as required by existing impedance measurement techniques, thus avoiding electromagnetic compatibility issues and additional equipment costs that may arise from injected signals.

[0022] Step S300: Calculate the line impedance parameters based on the characteristic components.

[0023] Specifically, using the voltage amplitude, current amplitude, and phase difference of each frequency component extracted in step S200, and combining Ohm's law and the calculation principles of AC circuits, the impedance values ​​of the line at different frequencies can be calculated. For example, the impedance calculated using the DC component mainly represents the resistance component; the impedance calculated using the high-frequency harmonic components includes both resistance and reactance components. Since the geometric parameters of the line (such as length and wire diameter) are fixed, changes in the impedance parameters directly reflect changes in the physical state of the line (such as temperature and height above ground). This step establishes a mapping bridge between electrical parameters and physical parameters.

[0024] Step S400: Invert the temperature and sag of the transmission line based on the line impedance parameters.

[0025] Specifically, this is the theoretical core of the condition monitoring achieved in this embodiment. The resistance of a conductor increases linearly with increasing temperature. Therefore, based on the calculated DC resistance of the line and the temperature coefficient of resistance of the conductor material, the current average temperature of the line can be deduced. On the other hand, the reactance of the line (especially the inductance) is closely related to the average height of the conductor to ground, and changes in sag directly alter the average height of the conductor to ground. Therefore, by monitoring changes in the line reactance, changes in the line sag can be deduced. This inversion calculation method is entirely based on electrical measurement data, enabling indirect measurement of non-electrical physical quantities of the line, effectively solving the technical challenge of directly measuring temperature and sag in harsh environments.

[0026] Step S500: Adjust the output current of the DC de-icing power supply according to the temperature and sag of the transmission line.

[0027] Specifically, after obtaining real-time line temperature and sag data, the system will implement closed-loop feedback control of the de-icing power supply accordingly. For example, if the retrieved temperature exceeds the line's maximum allowable operating temperature, it indicates that the line is overheating, and the output current needs to be reduced to prevent damage. When the sag rate of change fluctuates abnormally, it may mean that the line has experienced ice-breaking jumps, in which case the current needs to be adjusted or even the system shut down to ensure safety. This automatic control based on real-time status feedback replaces the traditional manual adjustment method, significantly improving the automation level and safety of de-icing operations and avoiding the risk of line overheating caused by delayed manual judgment.

[0028] Example 2: This example, based on Example 1, provides a detailed description of the feature component extraction process. The feature components include a DC component and a characteristic frequency component; wherein, the characteristic frequency component is the inherent harmonic component of the DC de-icing power supply; the DC component is used to calculate the line resistance, and the characteristic frequency component is used to calculate the line reactance.

[0029] Specifically, DC de-icing power supplies typically use rectifier circuits to convert AC to DC. Their output signal is not ideal pure DC, but rather superimposed with harmonic signals of various frequencies. These harmonic signals are naturally generated by the internal rectifier components (such as thyristors) during the switching process and are inherent physical characteristics of the power supply. This embodiment cleverly utilizes these harmonic components, which are "originally considered interference," to transform them into an effective signal source for probing the line's reactance characteristics. The DC component mainly flows through the resistive path of the line, and its amplitude change directly reflects the change in the line's DC resistance. Meanwhile, characteristic frequency components (such as the 300Hz and 600Hz higher harmonics generated by a 6-pulse rectifier power supply) flow through the reactive path of the line, and their phase and amplitude relationship reflects the combined effect of the line's inductance and capacitance. By distinguishing between these two types of components, this invention achieves decoupled measurement of line resistance and reactance parameters, laying a data foundation for subsequent inversion of temperature and sag.

[0030] Further, the step of extracting feature components from the voltage signal and the current signal includes: performing a fast Fourier transform on the voltage signal and the current signal to obtain spectrum data; extracting the amplitude of the DC component from the spectrum data to obtain DC voltage and DC current; and extracting the amplitude and phase of the harmonic component from the spectrum data to obtain harmonic voltage and harmonic current.

[0031] Combination Figure 5 and Figure 6As shown, this embodiment uses the Fast Fourier Transform (FFT) algorithm to convert the voltage and current signals in the time domain into spectral data in the frequency domain, thereby achieving accurate separation of characteristic components. This process specifically includes the following sub-steps: Step S201, signal sampling. The processing unit controls the data acquisition card to synchronously acquire the voltage signal u(t) and the current signal i(t) at a preset high sampling rate (e.g., 200kHz). The sampling process needs to last for at least one complete power frequency cycle (e.g., 20ms) to obtain waveform data containing complete harmonic information. Figure 5 As shown, the collected voltage and current waveforms exhibit a DC shape with superimposed pulsating ripples, which contain the required harmonic components.

[0032] Step S202, Windowing Process. To suppress spectral leakage caused by data truncation and improve the accuracy of spectral analysis, this step applies a Hanning window or other suitable window function to the acquired time-domain data sequence. Windowing smooths abrupt changes at signal edges, concentrating spectral energy more at the true frequency points, thereby reducing the interference of spurious frequency components on the measurement results.

[0033] Step S203, FFT Transform. A Fast Fourier Transform is performed on the windowed data sequence to convert the time-domain waveform signal into a discrete spectral sequence X(f). For example... Figure 6 As shown, the transformed spectrum clearly displays the amplitude distribution of the signal at different frequency points. There is a significant peak at frequency f=0Hz, corresponding to the DC component of the signal; there are also obvious peaks at specific frequency points such as f=300Hz and 600Hz, corresponding to the inherent characteristic harmonic components of the power supply.

[0034] Step S204, Feature Extraction. Based on the spectral data, the parameters of the DC component and the characteristic frequency component are extracted respectively. For the DC component, the spectral amplitude at f=0Hz is directly read to obtain the DC voltage amplitude U. dc and DC current amplitude I dc For characteristic frequency components, the spectral amplitude and phase angle at a specific harmonic frequency point (e.g., 300Hz) are read to obtain the harmonic voltage amplitude U. hf Harmonic current amplitude I hf and their respective phase angles , By comparing the phase difference between voltage and current at the same frequency, the line impedance angle at that frequency can be calculated, and the reactance component can be separated.

[0035] It should be understood that although this embodiment uses the FFT algorithm as an example, other signal processing algorithms such as wavelet transform and Hilbert transform can also be used to extract feature components in other embodiments, as long as effective separation of DC components and harmonic components can be achieved. This embodiment uses the power supply's own harmonic signal for separation by FFT, eliminating the need for additional detection signals injected into the line. This avoids the high cost and potential electromagnetic compatibility risks of signal source equipment, and also avoids the drawback of external sensors failing to work in harsh weather conditions, significantly improving the robustness and economy of the monitoring system.

[0036] Example 3: This example, based on the feature components extracted in Example 2, provides a detailed explanation of the calculation of line impedance parameters and the inversion process of transmission line temperature and sag. Combined with... Figure 2 and Figure 3 The equivalent circuit model shown in this embodiment achieves accurate perception of the line status by establishing a mathematical mapping relationship between electrical parameters and physical parameters.

[0037] First, the step of calculating the line impedance parameters based on the characteristic components and inverting the temperature and sag of the transmission line based on the line impedance parameters includes: calculating the line resistance based on the DC component and inverting the temperature of the transmission line based on the line resistance; calculating the line reactance based on the characteristic frequency component and inverting the sag of the transmission line based on the line reactance.

[0038] Specifically, this embodiment utilizes the different impedance characteristics exhibited by transmission lines under excitation by signals of different frequencies. For example... Figure 2 and Figure 3 As shown, a transmission line can be equivalently represented as a distributed parameter circuit consisting of a resistor R, an inductor L, and a capacitor C. For the DC component (frequency 0Hz), the capacitor branch is in an open-circuit state, and the inductor branch is equivalent to a short circuit; at this time, the line impedance mainly exhibits resistive characteristics. However, for high-frequency harmonic components, the inductive reactance (ωL) of the inductor and the capacitive reactance (1 / ωC) of the capacitor cannot be ignored, and the line impedance exhibits a composite characteristic of resistance and reactance. Through this decoupled calculation method, this embodiment can separately obtain the resistance parameters reflecting the thermal state of the line and the reactance parameters reflecting the geometric shape of the line, thereby providing independent data support for subsequent temperature and sag inversion.

[0039] Further, the step of calculating the line resistance based on the DC component and inverting the transmission line temperature based on the line resistance includes: calculating the line DC resistance based on the DC component; and calculating the transmission line temperature based on the temperature coefficient of resistance of the conductor material and the ratio of the line DC resistance to a reference resistance at a reference temperature.

[0040] Specifically, the resistance of a conductor increases with increasing temperature; this physical property forms the theoretical basis for inversion temperature. The specific calculation logic for this step is as follows: Step S401: Calculate the DC resistance of the line. Utilize the DC voltage amplitude U extracted in Example 2. dc and DC current amplitude I dc Calculate the current DC resistance R of the line according to Ohm's law. dc : This resistance value reflects the actual conductivity of the circuit at the current temperature.

[0041] Step S402: Invert the temperature of the transmission line. Based on the temperature coefficient of resistance formula for conductor materials, establish a functional relationship between resistance and temperature. For common conductor materials such as aluminum stranded wire and steel-cored aluminum stranded wire, the relationship between resistance R and temperature T can be expressed as: Among them, R ref Reference temperature T ref The reference resistance is given by α, where α is the temperature coefficient of resistance of the conductor material. By transforming this formula, the DC resistance R can be obtained from the real-time measurement. dc Determine the current average temperature T of the line: Among them, R 20℃ The resistance is the line resistance at 20°C. Through the derivation of the above formula, this embodiment transforms the line temperature, which is difficult to measure directly, into a problem of calculating easily measurable electrical parameters, thus realizing non-contact temperature monitoring in harsh environments.

[0042] Further, the step of calculating the line reactance based on the characteristic frequency components and inverting the sag of the transmission line based on the line reactance includes: calculating the line reactance based on the characteristic frequency components; calculating the average height of the transmission line to ground based on the line reactance and the relationship between the line inductance and the average height to ground; and calculating the sag of the transmission line based on the average height to ground and the height of the line suspension point.

[0043] Specifically, changes in the sag of a conductor alter its average height above ground, thus changing the conductor's inductance. This step utilizes this physical relationship to infer changes in sag by monitoring changes in reactance. The specific calculation logic is as follows: Step S403: Calculate the line reactance. Utilize the harmonic voltage U at a specific frequency (e.g., 300Hz or 600Hz) extracted in Example 2. hf Harmonic current I hf Given the phase difference between the two, calculate the line impedance Z at that frequency.hf : This impedance includes a resistive component and a reactive component, as shown in the following formula: in, =2π f , is the angular frequency of the AC power supply. To account for the skin effect in AC resistance, L represents inductance and C represents capacitance; The relationship between the AC resistance and DC resistance of the circuit is as follows. Among them, the skin effect coefficient k f for Using R dc Solution of measurement results k f Thus, calculate Substitute it into line Z. hf The impedance expression can be used to calculate the line inductance L and capacitance C.

[0044] Step S404: Calculate the average height of the transmission line above ground. According to transmission line theory, the inductance L0 per unit length of a single overhead conductor and the average height h of the conductor above ground are related as follows: Where μ0 is the free magnetic permeability and r is the conductor radius. Since the total inductance of the line L = L0 * l (where l is the line length), the average height h of the conductor above ground can be calculated by measuring the inductance value L. This step establishes a quantitative relationship between the electrical parameter (inductance) and the geometric parameter (height).

[0045] Step S405: Calculate the sag of the transmission line. There is a geometric relationship between the average conductor height h above ground, the suspension point height H, and the sag g: The suspension point height H can be determined from the tower structure data and is usually a known quantity. By transforming this formula, the sag g of the line can be calculated: .

[0046] Through the above derivation process, this embodiment successfully converts the high-frequency reactance parameter into the line sag parameter. When the sag decreases due to ice melting on the line, the average height h to the ground will increase, which in turn leads to an increase in the inductance L, and this change will be sharply captured by the impedance change of the characteristic frequency component. This inversion method based on electrical principles completely gets rid of the dependence on optical observation equipment or tension sensors. Even in environments with extremely low visibility such as at night or in heavy fog, it can still accurately perceive the geometric shape change of the line, which greatly improves the environmental adaptability of the ice-melting operation monitoring system.

[0047] Embodiment 4: Based on the temperature and sag parameters obtained in Embodiment 3, this embodiment describes in detail the adjustment strategy for the output current of the DC ice-melting power supply. The adjusting the output current of the DC ice-melting power supply according to the inverted temperature and sag of the transmission line includes: when the temperature of the transmission line exceeds a preset temperature threshold, reducing the output current of the DC ice-melting power supply; when the temperature change rate of the transmission line exceeds a preset change rate threshold, reducing the output current of the DC ice-melting power supply; when the sag change rate of the transmission line is less than or equal to zero, keeping the output current of the DC ice-melting power supply unchanged; when the sag change rate of the transmission line is greater than zero, reducing the output current of the DC ice-melting power supply until the output stops.

[0048] Specifically, this embodiment establishes a set of multi-level control logic based on line physical state feedback, aiming at balancing ice-melting efficiency and line safety. The specific judgment process of this control logic is as follows: Step S501, temperature over-limit judgment. The processing unit compares the real-time line temperature T obtained by inversion calculation with the preset temperature threshold Tmax. The preset temperature threshold Tmax is usually set as the maximum allowable operating temperature of the line (for example, it can be set to 70°C or 80°C for aluminum conductor steel reinforced). If T≥Tmax, it indicates that the line is currently generating severe heat and there is a risk of overheating damage, and the controller immediately sends an instruction to reduce the output current of the DC ice-melting power supply, for example, by 50A per cycle, so as to reduce the line heating power. If T<Tmax, it is judged that the line operates normally.

[0049] Step S502, temperature change rate judgment. The processing unit calculates the temperature change amount between the current moment and the previous moment to obtain the temperature change rate dT / dt. The preset change rate threshold εT can be determined according to the planned ice-melting duration and the temperature rise range. If dT / dt≥εT, it indicates that the line temperature rises too fast, which may be caused by the deterioration of environmental heat dissipation conditions or the excessively high current set value. At this time, it is also necessary to reduce the output current to prevent thermal accumulation from getting out of control.

[0050] Step S503, sag change rate judgment. The processing unit calculates the sag change rate dg / dt according to the sag calculation values at consecutive moments. This judgment is a key link for identifying the ice-melting process, which is specifically divided into three situations: In the first scenario, when dg / dt ≤ 0, it indicates that the line sag is decreasing or remaining constant. During the de-icing process, as the ice melts and falls off, the weight borne by the conductor gradually decreases. Under tension, the conductor is pulled taut, resulting in a decrease in sag and an increase in height above the ground. This is a typical characteristic of normal de-icing operations. Therefore, the system determines that the current de-icing strategy is effective, maintains the output current constant, and continues the operation.

[0051] In the second scenario, when alternating positive and negative fluctuations are detected in the sag change rate—that is, the signs of the sag changes in two consecutive sampling periods are opposite (Δg(n) / Δg(n+1)<0)—it indicates that the line has experienced ice shedding and jumping. Large chunks of ice breaking off can cause the conductor to vibrate violently up and down momentarily, potentially causing fatigue damage to the line hardware. In this case, the system determines that the line is in an unstable state and needs to reduce the output current to lower the thermal stress on the line while simultaneously preventing further vibration.

[0052] In the third scenario, when dg / dt > 0, it indicates that the line sag is increasing. This usually means that the ice on the line has completely melted, and the conductor has expanded due to thermal increase in temperature, or the tension has been released, leading to an increase in sag. At this point, the line is no longer covered with ice, and continuing to carry current would not only waste energy but could also cause the conductor to over-elongate or even touch the ground. Therefore, the system determines that the de-icing operation is complete, rapidly reduces the output current until it stops, and ends the de-icing process.

[0053] It should be understood that the aforementioned preset temperature threshold, preset rate of change threshold, and current adjustment range can all be flexibly configured according to the specific line model, environmental conditions, and de-icing requirements. This embodiment, through the aforementioned multi-dimensional state judgment logic, achieves refined closed-loop control of the de-icing operation process, effectively solving the problems of response lag and subjective judgment inherent in traditional manual control methods, and significantly improving the safety and automation level of the de-icing operation.

[0054] Example 5: This example provides a DC de-icing operation monitoring system for power transmission lines. For example... Figure 1 As shown, this system is the hardware carrier of the monitoring methods described in Examples 1 to 4. Through the coordinated operation of its various functional modules, it achieves real-time monitoring and automatic control of the de-icing line status. Specifically, the system includes: a DC de-icing power supply, a measurement unit, a processing unit, and a controller.

[0055] The DC de-icing power supply 1 is configured to output de-icing current to the transmission line.

[0056] Specifically, the DC de-icing power supply is the core energy supply device of the entire de-icing operation system, and also the signal excitation source for the monitoring method described in this invention. During the de-icing operation, the current output by this power supply is not only used to heat the lines to melt the ice, but its inherent DC component and harmonic components are also multiplexed as carrier signals to detect the line impedance parameters. This power supply typically uses a three-phase bridge rectifier circuit (such as a 6-pulse or 12-pulse rectifier circuit), and the output current is controlled by adjusting the conduction angle of the rectifier elements (such as thyristors). It should be understood that although... Figure 1 The diagram shows a single power supply module, but in actual engineering applications, the power supply can also be a power system composed of multiple rectifier modules connected in parallel, as long as it can output an ice-melting current containing characteristic components.

[0057] The measuring unit 2 is connected to the DC de-icing power supply and is configured to collect the voltage and current signals output by the DC de-icing power supply.

[0058] Specifically, the measurement unit, acting as the system's "sensor," is responsible for extracting low-voltage, low-current signals from the high-voltage, high-current main circuit, making them available for analysis by the processing unit. Physically, the measurement unit's input is directly connected to the output terminal of the DC de-icing power supply, enabling real-time monitoring of the power supply's output voltage and current waveforms. This connection method ensures that the measured signals accurately reflect the electrical quantities flowing through the icing line 5, avoiding the installation difficulties and communication interference problems caused by distributing sensors along the line. The measurement unit typically includes voltage and current conversion stages, converting voltages up to several kilovolts and currents up to several hundred amperes into standard low-voltage signals (such as ±10V voltage signals or 4-20mA current signals), and achieving electrical isolation between the high-voltage and low-voltage sides, ensuring the safety of subsequent processing units.

[0059] The processing unit 3 is communicatively connected to the measurement unit and is configured to extract feature components from the voltage and current signals, calculate line impedance parameters based on the feature components, and invert the temperature and sag of the transmission line according to the line impedance parameters.

[0060] Specifically, the processing unit is the "brain" of the system, undertaking the core tasks of data analysis and state calculation. It establishes a communication connection with the measurement unit via signal cables or optical fibers, receiving analog or digital signals output by the measurement unit. Internally, the processing unit runs the signal processing algorithms and physical models described in Examples 2 and 3, specifically performing FFT transformation, feature component extraction, impedance calculation, and inversion calculations of temperature and sag. In terms of hardware architecture, the processing unit typically possesses high-speed data acquisition capabilities and powerful numerical calculation capabilities, enabling it to complete all calculation tasks within one power frequency cycle (e.g., 20ms), thus ensuring the real-time nature of the monitoring results. The processing unit transmits the calculated line temperature, sag, and rate of change, among other state data, to the controller in real time via the communication interface.

[0061] The controller 4 is connected to the processing unit and the DC de-icing power supply, and is configured to adjust the output current of the DC de-icing power supply according to the temperature and sag of the transmission line obtained by inversion.

[0062] Specifically, the controller is the system's "executor," responsible for closed-loop control of the de-icing power supply based on decision information provided by the processing unit. Its input is connected to the communication interface of the processing unit to acquire line status data; its output is connected to the control port of the DC de-icing power supply to send control commands. The controller internally has the control strategy logic described in Example 4, including modules for temperature threshold judgment, rate of change threshold judgment, and sag trend judgment. When the line status parameters trigger preset protection conditions (such as temperature exceeding limits or abnormally increased sag), the controller immediately generates corresponding current adjustment commands (such as reducing the conduction angle), driving the DC de-icing power supply to adjust the output current, thereby achieving automated closed-loop control of the de-icing operation. It should be understood that the controller can be a standalone physical device (such as a PLC or dedicated industrial control board) or integrated into the internal control system of the DC de-icing power supply, as long as it has the function of receiving external status feedback and adjusting the power output.

[0063] Through the organic coordination of the above four components, this embodiment constructs a complete "perception-decision-execution" closed-loop system. This system requires no additional sensors to be installed on the transmission line; it utilizes only the power supply's own output signal and fixed measuring devices to achieve real-time monitoring and automatic control of the line status even under severe weather conditions. This effectively solves the problems of existing monitoring methods being greatly constrained by the environment and having a low degree of automation.

[0064] Example 6: This example, based on Example 5, provides a detailed explanation of the hardware selection and collaborative working mechanism of the monitoring system. The specific hardware configuration is fundamental to achieving signal acquisition and processing functions. Appropriate selection ensures that the system accurately acquires characteristic components under high voltage and strong electromagnetic interference environments, thereby supporting subsequent impedance calculations and state inversion.

[0065] The measuring unit includes a voltage sensor and a current sensor; the voltage sensor is configured to acquire the voltage signal output by the DC de-icing power supply; the current sensor is configured to acquire the current signal output by the DC de-icing power supply.

[0066] Specifically, voltage and current sensors are front-end devices in the monitoring system that sense electrical quantities, and their performance directly determines the accuracy of the raw data. For voltage signal acquisition, this embodiment preferably uses a resistive-capacitive voltage divider. Utilizing the voltage division principle of capacitance and resistance, the resistive-capacitive voltage divider can proportionally reduce the high voltage (e.g., 10kV) output from the DC de-icing power supply to a low voltage signal (e.g., ±10V) for subsequent circuit processing. Compared to a simple resistive voltage divider, the resistive-capacitive voltage divider has better frequency response characteristics, accurately reproducing voltage waveforms containing high-order harmonic components, avoiding harmonic amplitude attenuation due to insufficient sensor bandwidth, thus ensuring the accuracy of characteristic frequency component extraction. For current signal acquisition, this embodiment preferably uses a Hall effect current sensor. Based on the Hall effect principle, the Hall effect sensor can achieve electrical isolation between the primary side (high-voltage, high-current side) and the secondary side (low-voltage control side), effectively blocking interference from the high-voltage circuit to the control circuit. Meanwhile, Hall effect sensors have a wide bandwidth (typically above 100kHz), capable of covering the main harmonic frequencies generated by DC de-icing power supplies (such as 300Hz, 600Hz, etc.), ensuring distortion-free transmission of high-frequency current components. It should be understood that in other embodiments, the measurement unit may also employ other types of sensors such as optical voltage transformers or Rogowski coils, as long as they meet the requirements of high-voltage isolation and wide-bandwidth measurement.

[0067] The processing unit includes a data acquisition card and a processor; the data acquisition card is configured to sample the voltage signal and the current signal; the processor is configured to perform the operations of extracting feature components from the voltage signal and the current signal, calculating line impedance parameters, and inverting the temperature and sag of the transmission line.

[0068] Specifically, the processing unit is the computational core of the monitoring system, responsible for converting the analog signals output by the sensors into digital signals and executing complex algorithm logic. The data acquisition card, acting as a bridge between the analog and digital domains, has key parameters including sampling rate and resolution. In this embodiment, the data acquisition card preferably uses the NIPCIe-6363 model, with a maximum sampling rate of 2MS / s (2 million samples per second), far exceeding the Nyquist sampling requirements for characteristic harmonic frequencies (such as 600Hz). This allows for the acquisition of a sufficient number of sample points within one power frequency cycle, ensuring the frequency resolution and computational accuracy of the FFT transform. Simultaneously, this acquisition card has 16-bit resolution, effectively distinguishing minute signal changes and improving the accuracy of impedance calculation. The processor is preferably an industrial control computer, which deploys the signal processing algorithms and physical models described in embodiments 2 and 3. The industrial control computer communicates with the data acquisition card at high speed via the PCIe bus, reads the sampled data in real time, and utilizes its powerful CPU computing capabilities to complete a series of numerical calculations such as FFT transform, feature component extraction, impedance calculation, and temperature sag inversion. In actual operation, the data acquisition card synchronously acquires voltage and current signals according to a set sampling period (e.g., 20ms) and caches the data in memory. The processor then reads the data and executes algorithms to calculate the current line temperature and sag parameters, and finally sends the results to the controller through the communication interface. This hardware architecture has a clear division of labor: the data acquisition card is responsible for high-precision signal digitization, and the processor is responsible for complex logic operations. The two work together to ensure the real-time performance and reliability of the monitoring system.

[0069] Example 7: To more intuitively verify the actual effect of the monitoring method and system described in this invention, a specific 20km overhead ground wire DC de-icing operation scenario is used as an example to demonstrate in detail the monitoring and control logic of the entire process from the start of de-icing to the removal of icing. It should be understood that the specific parameter values ​​given in this example are merely exemplary and are intended to illustrate the feasibility of the technical solution, and do not constitute a limitation on the scope of protection of this invention.

[0070] In this application scenario, the icing line is defined as the overhead ground wire of a ±800kV overhead DC transmission line with a length l = 20km. The two ground wires connected to the positive and negative terminals of the DC de-icing power supply are of the same type, JLB20A-150 aluminum-clad steel stranded wire. The DC resistance r per unit length of this type of conductor at 20℃ is known. dc The resistance is 0.000583 Ω / m. Based on this, the total resistance of the de-icing circuit at the reference temperature R20℃ = 0.000583 × 2 × 20 × 10³ = 23.32 Ω. The temperature coefficient of resistance α of the conductor is 0.00366 (1 / ℃), and the maximum allowable operating temperature T... maxThe temperature is set at 80℃. The conductor diameter d is 1.58cm, and the suspension point height H above the ground is 65m. At the start of the operation, the ambient temperature T0 = -5℃, the wind speed is 5m / s, and the ice thickness on the line is approximately 15mm. Based on the above conditions, the initial target value of the de-icing current I is... set It is 350A.

[0071] Step S101: Start ice melting and signal acquisition. After the DC ice melting power supply is started, the controller gradually adjusts the thyristor conduction angle to make the output current rise steadily to the set value of 350A, so as to avoid the impact of sudden current changes on the line. At this time, the measurement unit starts to work, and it acquires the voltage signal u(t) and current signal i(t) at the power supply output terminal in real time. Since the power supply uses a 6-pulse rectifier circuit, the acquired raw waveform shows a DC form with superimposed pulsating ripples. These ripples contain characteristic harmonic components with frequencies of 300Hz, 600Hz, etc.

[0072] Step S102, Feature Component Extraction. The processing unit performs FFT transformation on the acquired raw signal. Assume that within a certain sampling period, the processing unit extracts the following key parameters from the spectral data: DC voltage amplitude U... dc =8162.24V, DC current amplitude I dc =350.01A; 300Hz harmonic voltage amplitude U hf =1335.67V, harmonic current amplitude I hf =8.77A, with a phase difference of approximately 80.54°.

[0073] Step S103, Impedance Calculation and State Inversion. The processing unit performs calculations based on the extracted feature components. First, it calculates the current line DC resistance based on the DC component: R dc =U dc / I dc =8162.24 / 350.01≈23.32Ω. Since the line had just started de-icing and the temperature had not yet risen significantly, the calculated resistance value was basically consistent with the reference resistance value. Subsequently, the processing unit used the temperature coefficient of resistance formula to invert the line temperature. Substituting the values ​​into the calculation, the average line temperature at this time was T≈20℃. This indicates that in the early stages of de-icing, the conductor temperature was mainly affected by the ambient temperature and had not yet reached the effective de-icing temperature range.

[0074] Simultaneously, the processing unit calculates the line impedance using the 300Hz harmonic components and separates the reactance component, thereby estimating the line inductance L. Based on transmission line theory, the average height h of the conductor above ground is obtained by inversion using the relationship between inductance and height above ground. Combined with the suspension point height H = 65m, the current line sag g is calculated. Under icing conditions, the conductor load is greater, and the sag value is typically greater than the design sag under non-icing conditions. Assume the initial sag value obtained by inversion is g0.

[0075] Step S104, Dynamic Monitoring and Process Control. As the de-icing operation continues, the line temperature gradually rises. Assume that after a period of time, the processing unit monitors the DC resistance R in subsequent sampling cycles. dc The resistance was increased to 24.5Ω. At this point, the calculated line temperature T rose to approximately 40℃. The rate of temperature change, dT / dt, was within the normal range and did not exceed the preset threshold εT. Simultaneously, the rate of sag change, dg / dt, was ≤0, indicating that the sag was slowly decreasing, a normal physical phenomenon indicating the gradual melting of ice and the release of conductor tension. The system determined that the de-icing operation was progressing smoothly, and the controller maintained the output current at 350A to continue heating.

[0076] Step S105, Abnormal State Identification and Response. In the later stages of ice melting, assume the monitoring system detects abnormal fluctuations in the sag rate of change. Specifically, the calculation results of sag data from three consecutive sampling periods show that the sag changes in the two consecutive periods have opposite signs, i.e., Δg(n) / Δg(n+1)<0. This characteristic indicates that the line has experienced ice-shedding jumps, with large chunks of ice breaking off and causing severe vibration of the conductor. At this time, although the line temperature may not have reached the maximum threshold, to prevent further vibration and damage to the fittings, the controller immediately responds by reducing the output current, for example, lowering the current to 300A to reduce thermal stress on the line.

[0077] Step S106, Determination of De-icing Completion. As the ice completely melts, the conductor tension returns to a non-iced state. The processing unit monitors that the sag change rate dg / dt remains greater than zero, indicating that the sag is increasing (the conductor is shrinking due to the weight of the non-iced conductor, or the sag is increasing due to thermal expansion). This characteristic is a typical sign of a non-iced line. At this point, the system determines that the de-icing operation is complete, the controller rapidly reduces the output current until it drops to 0, automatically stops the DC de-icing power supply, and ends the operation.

[0078] Through the complete demonstration of the above application scenarios, it can be clearly seen how the system described in this invention utilizes the output signal of the DC de-icing power supply to sense changes in the resistance and reactance of the line in real time, thereby accurately retrieving the temperature and sag state, and automatically executing corresponding control strategies based on different physical state characteristics (such as normal de-icing, de-icing vibration, and no icing). This process requires no manual intervention or external sensor assistance, verifying the feasibility and effectiveness of this invention in achieving automated and intelligent de-icing operation monitoring in harsh environments.

[0079] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for monitoring DC de-icing operations on transmission lines, characterized in that, include: Collect the voltage and current signals output by the DC de-icing power supply; Extract feature components from the voltage and current signals; Calculate the line impedance parameters based on the characteristic components; The temperature and sag of the transmission line are inverted based on the aforementioned line impedance parameters; The output current of the DC de-icing power supply is adjusted according to the temperature and sag of the transmission line.

2. The method for monitoring DC de-icing operations of transmission lines according to claim 1, characterized in that, The characteristic components include a DC component and a characteristic frequency component; The characteristic frequency component is the inherent harmonic component of the DC de-icing power supply. The DC component is used to calculate the line resistance, and the characteristic frequency component is used to calculate the line reactance.

3. The method for monitoring DC de-icing operations of transmission lines according to claim 2, characterized in that, Extracting feature components from the voltage and current signals includes: Perform a Fast Fourier Transform on the voltage and current signals to obtain spectral data; The amplitude of the DC component is extracted from the spectral data to obtain the DC voltage and DC current; The amplitude and phase of the harmonic components are extracted from the spectral data to obtain the harmonic voltage and harmonic current.

4. The method for monitoring DC de-icing operations of transmission lines according to claim 2, characterized in that, The calculation of line impedance parameters based on the characteristic components, and the inversion of the temperature and sag of the transmission line based on the line impedance parameters, includes: The line resistance is calculated based on the DC component, and the temperature of the transmission line is inverted based on the line resistance. The line reactance is calculated based on the characteristic frequency components, and the sag of the transmission line is inverted based on the line reactance.

5. A method for monitoring DC de-icing operations of transmission lines according to claim 4, characterized in that, The step of calculating the line resistance based on the DC component and inverting the temperature of the transmission line based on the line resistance includes: Calculate the DC resistance of the line based on the DC component; Based on the temperature coefficient of resistance of the conductor material, the temperature of the transmission line is calculated according to the ratio of the DC resistance of the line to the reference resistance at the reference temperature.

6. The method for monitoring DC de-icing operations of transmission lines according to claim 4, characterized in that, The step of calculating the line reactance based on the characteristic frequency components and inverting the sag of the transmission line based on the line reactance includes: Calculate the line reactance based on the characteristic frequency components; Based on the relationship between line inductance and average height to ground, the average height to ground of the transmission line is calculated according to the line reactance. The sag of the transmission line is calculated based on the average height above the ground and the height of the line suspension point.

7. The method for monitoring DC de-icing operations of transmission lines according to claim 1, characterized in that, The step of adjusting the output current of the DC de-icing power supply based on the temperature and sag of the transmission line obtained through inversion includes: When the temperature of the transmission line exceeds a preset temperature threshold, reduce the output current of the DC de-icing power supply. When the temperature change rate of the transmission line exceeds a preset change rate threshold, the output current of the DC de-icing power supply is reduced. When the sag rate of the transmission line is less than or equal to zero, the output current of the DC de-icing power supply remains constant. When the sag rate of the transmission line is greater than zero, reduce the output current of the DC de-icing power supply until it stops outputting.

8. A DC de-icing operation monitoring system for transmission lines, applicable to the DC de-icing operation monitoring method for transmission lines as described in any one of claims 1-7, characterized in that it comprises: A DC de-icing power supply, configured to output de-icing current to transmission lines; The measuring unit is connected to the DC de-icing power supply and is configured to acquire the voltage and current signals output by the DC de-icing power supply. The processing unit is communicatively connected to the measurement unit and is configured to extract feature components from the voltage and current signals, calculate line impedance parameters based on the feature components, and invert the temperature and sag of the transmission line based on the line impedance parameters. A controller, connected to the processing unit and the DC de-icing power supply, is configured to adjust the output current of the DC de-icing power supply according to the temperature and sag of the transmission line obtained from the inversion.

9. A DC de-icing operation monitoring system for transmission lines according to claim 8, characterized in that, The measurement unit includes a voltage sensor and a current sensor; The voltage sensor is configured to acquire the voltage signal output by the DC de-icing power supply; The current sensor is configured to collect the current signal output by the DC de-icing power supply.

10. A DC de-icing operation monitoring system for transmission lines according to claim 8, characterized in that, The processing unit includes a data acquisition card and a processor; The data acquisition card is configured to sample the voltage and current signals; The processor is configured to perform the operations of extracting feature components from the voltage and current signals, calculating line impedance parameters, and inverting the temperature and sag of the transmission line.

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