Transformer winding deformation live detection system using iron core grounding wire to inject frequency response signal
By injecting frequency response signals into the transformer core grounding wire, combined with Rogowski coil sensors and network transfer function analysis, the problem of power outage in transformer winding deformation detection was solved, realizing miniaturized and convenient live detection, and improving the sensitivity and accuracy of detection.
Patent Information
- Application Number
- CN202520833710.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-28
- Publication Date
- 2026-02-24
- Estimated Expiration
- 2035-04-28
AI Technical Summary
Existing methods for detecting transformer winding deformation require offline testing during power outages, which cannot detect cumulative effects in a timely manner. Furthermore, the testing devices are bulky, inconvenient to install and disassemble, and the test results rely on human experience, resulting in insufficient sensitivity and accuracy.
A transformer winding deformation live detection system is adopted, which injects frequency response signals through the iron core grounding wire. It utilizes Rogowski coil sensors and weak high-frequency signal processing circuits to inject signals into the windings through magnetic field coupling. Combined with network transfer function analysis, the winding deformation is analyzed to achieve miniaturized and lightweight live detection.
It enables live detection of transformer windings. The device is miniaturized, easy to install and disassemble, and can continuously monitor the operating status to obtain more reliable data, reducing detection costs and time requirements.
Smart Images
Figure CN223941084U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of winding deformation detection technology, and in particular to a transformer winding deformation live detection system that injects frequency response signals by the iron core grounding wire. Background Technology
[0002] To improve the reliability of the power grid, my country's power industry is vigorously promoting the intelligent, digital, and information-based development of equipment. For transformers, winding deformation is one of the important causes of serious accidents such as inter-turn short circuits and insulation breakdown. Timely detection of local deformation is an effective means to avoid these accidents. However, people's understanding of the mapping relationship between the internal winding deformation of transformers and external measurable characteristics is not yet thorough enough. Current diagnostic methods generally have low sensitivity and accuracy, and live-line testing technology is generally not mature enough. In practice, offline testing is still the main method.
[0003] Currently, commonly used methods for detecting winding deformation include the short-circuit impedance method and the frequency response analysis method (FRA). Both require the transformer to be disconnected from the power grid, becoming an isolated device for testing. Compared to the short-circuit impedance method, the frequency response curve used in FRA contains much richer information and has higher sensitivity. Therefore, FRA has been widely used both domestically and internationally, and has both domestic industry standards and international standards.
[0004] The power industry standard DL / T911-2016, "Frequency Response Analysis Method for Power Transformer Winding Deformation," clarifies the offline detection method for transformer winding deformation using the frequency response method. The diagnostic technique of frequency response analysis is based on the horizontal or vertical comparison of frequency response amplitude curves. The horizontal comparison method compares the three-phase windings on each side of the same transformer. When the spectral characteristics of the three phases are inconsistent, the spectral characteristics of the windings of transformers of the same model produced in the same period from the same manufacturer are used for judgment. If the consistency among the three phases of transformers produced in the same period is good, it is preliminarily determined that the transformer winding has deformed. The vertical analysis method compares the amplitude-frequency characteristics of the transformer currently recorded with those recorded during normal operation. If the difference between the two exceeds a certain level, it can be preliminarily determined that the winding has deformed. However, the offline detection of transformer winding deformation currently faces the following problems in practice:
[0005] (1) Offline detection of transformer winding deformation requires de-energizing and disconnecting the transformer. In actual operation, the transformer cannot be easily stopped.
[0006] (2) Transformer winding deformation has a cumulative effect, and the offline detection interval is long, making it impossible to detect defects in a timely manner;
[0007] (3) Since there are no clear requirements for the output signal, offline testing depends on the technical level and work experience of the testing personnel.
[0008] Due to the long cycle and low economic efficiency of offline testing, live-line testing has become increasingly popular in recent years. However, transformer windings in live operation not only carry large currents and high potentials, but are also directly electrically connected to other equipment in the substation and overhead transmission lines. Existing offline testing and frequency response functions cannot be directly applied to operating transformers. The crucial problem of "how to inject an excitation signal into the high-potential winding and obtain a response signal from it" must be solved. Currently, some researchers have used magnetic field coupling to inject a sweep frequency excitation signal from the winding neutral point or bushing root using a coil, and then measure the current response signal from the bushing root. The feasibility of this method has been verified on a 110kV transformer in a transformer factory and a 35kV live-line transformer in the field. However, this testing method has many problems. Due to bushing insulation distance limitations, power outages are required to install the sensor, which is uneconomical and time-consuming; generally, the sensors used are large in size and weight, occupying a lot of space and are inconvenient to replace or disassemble.
[0009] Regarding the core grounding point, it was previously believed that injecting frequency response signals from this point would be unlikely to yield a measurable signal, and that the principle differed significantly from measurements taken from the winding neutral point or bushing root. However, different types of substation cores are all single-point grounded, making them practically universal; compared to the large size of bushings, the core grounding wire is small, enabling miniaturization and weight reduction of transformer live-line detection devices, facilitating installation and disassembly. Therefore, it is possible to attempt frequency response signal injection, construct a relevant network transfer function, and inject a frequency response excitation signal from the core grounding wire to perform live-line detection of transformer winding deformation.
[0010] To address the aforementioned issues, it is necessary to research a transformer winding deformation live-line detection system that can be installed and operated under energized conditions and that injects frequency response signals through the iron core grounding wire to meet practical needs. Utility Model Content
[0011] The purpose of this invention is to address the shortcomings of existing technologies by proposing a transformer winding deformation live-line detection system that injects a frequency response signal through the iron core grounding wire. The system includes a signal source, a sensor, a weak high-frequency signal processing circuit, and a data acquisition and analysis platform. The sensor includes an excitation sensor and a response sensor. The weak high-frequency signal processing circuit includes a filtering unit, an integration unit, and an amplification unit. The data acquisition and analysis platform includes a signal acquisition module and a diagnostic analysis module. The signal source, excitation sensor, response sensor, filtering unit, integration unit, amplification unit, signal acquisition module, and diagnostic analysis module are connected sequentially.
[0012] Both the excitation sensor and the response sensor are Rogowski coil sensors, with the excitation sensor having a magnetic core and the response sensor having a non-ferromagnetic material as its winding frame.
[0013] The excitation sensor is installed on the iron core grounding wire, and the response sensor is installed at the end of the terminal compartment of each phase cable on the high voltage side.
[0014] The excitation sensor is 50cm above the ground, and the response sensor is 220cm above the ground.
[0015] The center of the response sensor is fitted with a current-carrying metal sheath, grounding wire, and cable body.
[0016] The beneficial effects of this utility model are as follows:
[0017] 1. Unlike bushings and outgoing cables that have space limitations (protective devices, iron frames), iron core grounding wires can achieve miniaturization and weight reduction of transformer live-line detection devices, making them easy to install and disassemble;
[0018] 2. The iron cores of different types of substations are all single-point grounded. Frequency response excitation signals are injected through the iron core grounding wire, and the induced current signal at the iron core grounding point can be measured. More diverse transfer functions can be constructed to explore new technologies for detecting transformer winding deformation under live conditions.
[0019] 3. It can be installed under power without interrupting the power supply to monitor the operating status of transformer windings, making it economical and reliable;
[0020] 4. It can achieve continuous measurement of transformers in operation, and obtain more accurate and reliable data. Attached Figure Description
[0021] Figure 1 This is a structural diagram of the detection system of this utility model;
[0022] Figure 2 This is a schematic diagram of the excitation sensor and response sensor structure;
[0023] Figure 3 This is a schematic diagram of interference shielding in signal processing circuits;
[0024] Figure 4 This is a schematic diagram of the test principle for the deformation of a live transformer winding;
[0025] Figure 5 It is a curve image generated using the network function H. Detailed Implementation
[0026] This invention proposes a transformer winding deformation live detection system that injects frequency response signals through the iron core grounding wire. The invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0027] Figure 1This is a structural diagram of the detection system of this utility model, including a signal source, sensors, a weak high-frequency signal processing circuit, and an acquisition and analysis platform; the sensors include an excitation sensor and a response sensor; both the excitation sensor and the response sensor are Rogowski coil type sensors, and the winding frame of the excitation sensor is a magnetic core to enhance the signal coupling effect; the winding frame of the response sensor is made of non-ferromagnetic material to reduce interference from high power frequency noise signals. Figure 2 This is a schematic diagram of the excitation sensor and response sensor structure. The weak high-frequency signal processing circuit includes a filtering unit, an integration unit, and an amplification unit; the acquisition and analysis platform includes a signal acquisition module and a diagnostic analysis module; wherein, the signal source, excitation sensor, response sensor, filtering unit, integration unit, amplification unit, signal acquisition module, and diagnostic analysis module are connected sequentially. The specific operation steps are as follows:
[0028] 1. Install the excitation sensor on the 110kV high-voltage side iron core grounding wire, 50cm above the ground; install the three response sensors at the end of the terminal compartment of each phase cable on the high-voltage side, 220cm above the ground; wrap the current metal sheath grounding wire and the cable body together in the center of the response sensor.
[0029] 2. A 100V sweep frequency voltage signal is injected into the winding of the excitation sensor, with a sweep frequency range of 1kHz-1MHz. Utilizing the principle of magnetic field coupling, the excitation sensor couples the signal into the high-voltage winding, generating an induced current signal in the winding. The A, B, and C three-phase response sensors extract the induced current signal generated in the winding based on magnetic field coupling. For details on the principle of transformer winding deformation detection, please refer to [link to relevant documentation]. Figure 4 .
[0030] 3. The weak high-frequency signal processing circuit processes the frequency response voltage signal output by the response sensor. The frequency response signal first passes through a high-pass filter to remove power frequency noise, and then passes through a low-pass filter to remove high-frequency noise above 1MHz. After that, the composite integrator circuit processes the low-frequency and high-frequency bands to improve the sensitivity of signals from 1kHz to 10kHz and 900kHz to 1MHz, making the measurement frequency band flatter. Finally, the signal enters the amplifier, which amplifies the frequency response signal from tens to hundreds of microvolts to the millivolt level. Figure 3 This is a schematic diagram of interference shielding in signal processing circuits.
[0031] 4. The data acquisition and analysis module acquires signals processed by the weak high-frequency signal processing circuit. It simultaneously acquires signals from all sensors, classifies and processes the acquired data, and temporarily stores it. Then, it calculates the network function, constructing the network transfer function H using the port voltage-current relationship. The following are some possible types:
[0032]
[0033] Where j is the imaginary number, ω is the angular frequency, and H(ω) is the magnitude of the transfer function at frequency ω, which serves as the ordinate of the frequency response curve (amplitude-frequency curve). In the formula, U... S U1 is the voltage signal sent by the signal source to the excitation sensor, U2 is the voltage signal coupled out by the response sensor, I3 is the current signal coupled into the iron core grounding wire by the excitation sensor, and I4 is the induced current signal at the high voltage output terminal of the transformer winding.
[0034] Here is the construction of the transfer function H1, using it as an example:
[0035]
[0036] With the excitation sensor input voltage U S (Excitation signal) is used as a reference, and the output voltage signal U of the response sensor is used as a reference. X1 Combined, in the formula k T Represents the response sensor output voltage U X1 The voltage U generated by the sensing system X2 The scaling factor between them contains gain information from the weak signal processing circuit. X represents one of the three phases A, B, and C. See the generated frequency response function image for details. Figure 5 .
[0037] The generated frequency response curves are used for diagnostic analysis using correlation coefficients. The relevant calculations and processing are as follows:
[0038] Assuming X(k) and Y(k) are the frequency response amplitude sequences of the transformer under normal operating conditions and under winding deformation fault conditions, respectively, the characteristic function is calculated as follows:
[0039] First, calculate the standard deviation of the two sequences:
[0040]
[0041] Where k = 0, 1, 2, ..., N-1, is the number of sampling frequency points, and N is the total number of sampling frequency points;
[0042] The covariance of the two sequences is:
[0043]
[0044] The normalized covariance coefficients of the two sequences are:
[0045]
[0046] The relevant coefficients that meet the requirements of the project are:
[0047]
[0048] As shown in the above formula, the correlation coefficient between two identical curves is 10, and the greater the difference, the smaller the correlation coefficient.
[0049] A longitudinal comparison of the frequency response curves of three-phase windings at the same voltage level was performed. Changes in the frequency response characteristics of the winding's characteristic function were determined through characteristic indices, and a comprehensive analysis was conducted using multiple characteristic indices. The characteristic value used was R. LF (low-frequency correlation coefficient), R MF (Mid-frequency correlation coefficient), R HF (High-frequency band correlation coefficient), R (whole frequency band correlation coefficient).
[0050] The generated frequency response curves were compared with an online database, which refers to live-line testing data collected during the initial commissioning phase of the transformer, at which point the transformer was healthy and free from deformation. A comprehensive analysis of the three transfer functions was performed, and the results calculated using the correlation coefficient method are detailed in Table 1.
[0051] Table 1. Calculation results of eigenvalues of the frequency response curve of network function H.
[0052]
[0053]
[0054] Referring to the diagnostic criteria of the correlation coefficient method in the power industry standard DL / T911-2016 "Frequency Response Analysis Method for Winding Deformation of Power Transformers", it can be seen that all three phase windings of the transformer are in normal winding condition with no deformation. From the above analysis, it can be concluded that this detection system can achieve uninterrupted monitoring of transformer winding operation, which is economical and reliable; it can also perform continuous monitoring of transformers in operation, obtaining more accurate and reliable data.
Claims
1. A transformer winding deformation live-line detection system that injects frequency response signals via a core grounding wire, characterized in that, Includes signal source, sensor, weak high-frequency signal processing circuit, and acquisition and analysis platform; The sensor includes an excitation sensor and a response sensor; the weak high-frequency signal processing circuit includes a filtering unit, an integration unit, and an amplification unit; the acquisition and analysis platform includes a signal acquisition module and a diagnostic analysis module. The signal source, excitation sensor, response sensor, filtering unit, integration unit, amplification unit, signal acquisition module, and diagnostic analysis module are connected in sequence.
2. The transformer winding deformation live-line detection system based on the frequency response signal injected by the iron core grounding wire according to claim 1, characterized in that, Both the excitation sensor and the response sensor are Rogowski coil type sensors, with the excitation sensor having a magnetic core and the response sensor having a non-ferromagnetic material as its winding frame.
3. The transformer winding deformation live-line detection system based on the frequency response signal injected by the iron core grounding wire according to claim 2, characterized in that, The excitation sensor is installed on the iron core grounding wire, and the response sensor is installed at the end of the terminal compartment of each phase cable on the high voltage side.
4. The transformer winding deformation live-line detection system based on the frequency response signal injected by the iron core grounding wire according to claim 3, characterized in that, The excitation sensor is 50cm above the ground.
5. The transformer winding deformation live-line detection system based on the frequency response signal injected by the iron core grounding wire according to claim 3, characterized in that, The response sensor is 220cm above the ground.
6. The transformer winding deformation live-line detection system based on the frequency response signal injected by the iron core grounding wire according to claim 3, characterized in that, The center of the response sensor is fitted with a current-carrying metal sheath, a grounding wire, and a cable body.