Transformer winding deformation live monitoring device for GIS substation

Abstract

The invention discloses a transformer winding deformation live-line monitoring device for a GIS substation, and belongs to the technical field of winding deformation monitoring. Comprising a signal generation module, a feedback protection module, a sensor module, a weak high-frequency signal processing module, a signal acquisition module and a diagnostic analysis module, the feedback protection module comprises a change-over switch and a feedback unit; the sensor module comprises an excitation sensor and a response sensor; the weak high-frequency signal processing module comprises a filtering unit, an integrating unit and an amplifying unit; the signal generation module, the change-over switch, the feedback unit, the excitation sensor, the response sensor, the filtering unit, the integration unit, the amplification unit, the signal acquisition module and the diagnostic analysis module are connected in sequence. Frequency response signal injection and extraction and transformer winding deformation on-line monitoring are carried out at the tail end of each phase cable terminal bin on the high-voltage side of the transformer of the GIS substation, and key points of a sensor installation method of the monitoring device are provided.

Description

Technical Field

[0001] The present invention relates to the technical field of winding deformation monitoring, and particularly to a live monitoring device for transformer winding deformation in a GIS substation. Background Art

[0002] To improve the reliability of the power grid, the power industry in China vigorously promotes the development of equipment intelligence, digitization, and informatization. For transformers, winding deformation is one of the important reasons leading to serious accidents such as inter-turn short circuits and insulation breakdowns. 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 deep enough. Currently, the diagnostic methods generally have low sensitivity and accuracy, and the live detection technologies are generally not mature enough. In practice, off-line detection is still the main method.

[0003] Currently, the commonly used methods for detecting winding deformation include the low-voltage short-circuit impedance method and the frequency response analysis method (abbreviated as FRA). These two detection methods have been included in the winding deformation test process that must be carried out before the transformer leaves the factory and before it is put into production by the State Grid Corporation, and it is required to retain the original test data. Among them, the FRA has the advantages of good accuracy and convenient on-site use in detecting transformer winding deformation. Moreover, compared with the short-circuit impedance method, the frequency response curve used in FRA contains much richer information and higher sensitivity, so it has been widely promoted and used.

[0004] The power industry standard DL / T911-2016 "Frequency Response Analysis Method for Winding Deformation of Power Transformers" specifies the method for off-line detection of transformer winding deformation by the FRA. The diagnostic technology of the frequency response analysis method is based on the horizontal or vertical comparison of the frequency response amplitude curves. The horizontal comparison method uses the three-phase windings on each side of the same transformer for comparison. When the spectral characteristics between the three phases are inconsistent, the spectral characteristics of the windings of the same model transformers produced by the same factory in the same period are referred to for judgment. If the consistency between the three phases of the transformers produced in the same period is good, it is initially determined that the winding of the transformer has deformed. The vertical analysis method compares the amplitude-frequency characteristics of the current record of the transformer with the historical record during normal operation. If the difference between the two exceeds a certain degree, it can be initially determined that the winding has deformed. However, the off-line detection of transformer winding deformation currently faces the following problems in practice:

[0005] (1) Off-line detection of transformer winding deformation requires the transformer to be disconnected from the power grid and shut down. During the actual operation of the transformer, it cannot be easily stopped.

[0006] (2) Transformer winding deformation has a cumulative effect, and the off-line detection interval period is long, so defects cannot be detected in time.

[0007] (3) Since there is no clear regulation on the requirements for the output signal, off-line detection depends on the technical level and work experience of the detection personnel.

[0008] In the face of the deficiencies of offline detection, live monitoring has become more popular in recent years. The transformer winding in the live operation state not only carries large current and high potential, but also is directly electrically connected to other equipment in the substation and overhead transmission lines. Existing offline detection methods cannot be directly applied to operating transformers. At this time, it is necessary to solve the problem of how to inject an excitation signal into the winding at high potential and obtain a response signal from the winding. Some scholars use coils to inject a swept-frequency excitation signal from the neutral point of the winding or the root of the bushing, and measure the current response signal from the root of the bushing. However, this method has great limitations. If the transformer neutral point is not grounded, the sensor cannot be installed; when the sensor is installed at the root of the bushing, power outage is required for installation, which has low economic benefits and is time-consuming and laborious. New exploration and improvement are needed for the positions of frequency response signal injection and measurement for on-line monitoring of transformer winding deformation.

[0009] For the grounding outgoing cable of a GIS substation, it was previously considered that it was unlikely to measure a response signal by injecting a frequency response signal from here. However, compared with measuring at the root of the bushing, it has a larger operating space, the sensor installation is more convenient, and different from the limitation of the large insulation distance at the root of the bushing, it can be installed live at the outgoing cable, which is economical enough. Therefore, it is possible to try to inject and measure the frequency response signal from the outgoing cable of the GIS substation, construct the relevant network transfer function, and perform live detection of transformer winding deformation.

[0010] In view of the above problems, it is necessary to design a live monitoring device for transformer winding deformation in GIS substations with strong anti-interference ability, which can be installed and operated live to meet the actual needs. Summary of the Invention

[0011] The object of the present invention is to propose a live monitoring device for transformer winding deformation in GIS substations in view of the deficiencies of the prior art, including a signal generation module, a feedback protection module, a sensor module, a weak high-frequency signal processing module, a signal acquisition module, and a diagnostic analysis module;

[0012] The feedback protection module includes a changeover switch and a feedback unit; the sensor module includes an excitation sensor and a response sensor; the weak high-frequency signal processing module includes a filtering unit, an integrating unit, and an amplifying unit;

[0013] Among them, the signal generation module, the changeover switch, the feedback unit, the excitation sensor, the response sensor, the filtering unit, the integrating unit, the amplifying unit, the signal acquisition module, and the diagnostic analysis module are connected in sequence.

[0014] Both the excitation sensor and the response sensor are split-type Rogowski coil sensors, and the sensor core material is iron-based nanocrystalline.

[0015] The excitation sensor and the response sensor are installed at the ends of the cable terminal compartments of each phase on the high-voltage side.

[0016] Shielding layers are provided for each circuit element of the filtering unit, the integrating unit, and the amplifying unit.

[0017] The feedback unit is a unidirectional feedback parallel resonance device.

[0018] The switching switch is a periodic switching switch.

[0019] The installation method of the excitation sensor and the response sensor is as follows:

[0020] Place the two half excitation sensors of each phase at the ends of the cable terminal compartments of each phase on the high-voltage side, connect the aviation plug connecting wires, combine the excitation sensors, and tighten the interface screws;

[0021] Place the two half response sensors of each phase at the ends of the cable terminal compartments of each phase on the high-voltage side, and the response sensor sleevs the current metal sheath grounding wire and the cable body together in the center of the response sensor;

[0022] Parallel the anti-saturation coils of the three-phase response sensors through cable wires. After the parallel interfaces are firmly connected, connect the aviation plug connecting wires of each phase, combine the response sensors, and tighten the interface screws;

[0023] The input end of the excitation sensor is connected to the signal generation module through a cable wire, and the output end of the response sensor is connected to the weak high-frequency signal processing module through a cable wire.

[0024] The height difference between the response sensor and the excitation sensor is not less than 30 cm.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. The monitoring device can achieve live installation and detect the operating conditions of the transformer winding without power interruption, which is economical and reliable.

[0027] 2. The monitoring device can continuously measure the live operating transformer to obtain more real and reliable data.

[0028] 3. The monitoring device can diagnose early faults of the transformer winding, give early warnings before the faults worsen, and realize scientific planned maintenance work.

[0029] 4. The monitoring device can fully understand the historical usage of the equipment and make full use of its lifespan in the context of asset management. Description of the Drawings

[0030] Figure 1 It is a schematic structural diagram of the transformer winding deformation live monitoring device for GIS substations of the present invention;

[0031] Figure 2Schematic diagram of the sensor layout for monitoring the deformation of the transformer winding in a GIS substation;

[0032] Figure 3 Magnetic field distribution nephogram at different installation distances;

[0033] Figure 4 Schematic diagram of the interference shielding treatment for the signal processing circuit;

[0034] Figure 5 Principle diagram for detecting the deformation of the energized transformer winding;

[0035] Figure 6(a) is the frequency response curve with the excitation and response in phase;

[0036] Figure 6(b) is the frequency response curve with the excitation and response out of phase. Specific implementation manner

[0037] The present invention provides a device for on-line monitoring of the deformation of the transformer winding in a GIS substation. The following further describes the present invention with reference to the accompanying drawings and specific embodiments.

[0038] Figure 1 Schematic diagram of the structure of the device for on-line monitoring of the deformation of the transformer winding in a GIS substation according to the present invention; the device includes a signal generation module, a feedback protection module, a sensor module, a weak high-frequency signal processing module, a signal acquisition module, and a diagnostic analysis module; the feedback protection module includes a switching switch and a feedback unit; the sensor module includes an excitation sensor and a response sensor, both of which are Rogowski coil sensors based on the principle of magnetic field coupling. A measuring coil is wound around the magnetic core of the excitation sensor, one end of the coil is grounded, and the other end is the input end; a measuring coil and an anti-saturation coil are wound around the magnetic core of the response sensor, one end of the measuring coil is grounded, and the other end is used as the output end; the anti-saturation coils of each response sensor are connected in parallel through an external cable, and a small impedance Z is connected in series at the port of each anti-saturation coil. Both the excitation sensor and the response sensor are of the open type, and the sensor core material is iron-based nanocrystalline. The two ends of the sensor are open, the sensor housing and the break of the magnetic core are fastened by screws, and the break points of the coils are connected by an aviation plug connection line. The weak high-frequency signal processing module includes a filtering unit, an integrating unit, and an amplifying unit; among them, the signal generation module, the switching switch, the feedback unit, the excitation sensor, the response sensor, the filtering unit, the integrating unit, the amplifying unit, the signal acquisition module, and the diagnostic analysis module are connected in sequence. The specific monitoring steps are as follows:

[0039] 1. Install three excitation sensors at the end of each phase cable terminal compartment on the high-voltage side, at a height of 210 cm from the ground; install three response sensors at the end of each phase cable terminal compartment on the high-voltage side, at a height of 255 cm from the ground. For the specific layout scheme, please refer to Figure 2 , and the installation process is as follows:

[0040] (1) Place the two half excitation sensors of each phase at the end of the cable terminal compartment of each phase on the high-voltage side, connect the aviation plug connecting wires, combine the sensors, and tighten the interface screws.

[0041] (2) Place the two half response sensors of each phase at the end of the cable terminal compartment of each phase on the high-voltage side. The response sensor sleevs the current metal sheath grounding wire and the cable body together in the center of the sensor. Figure 3 For the magnetic field distribution nephogram at different installation distances, with the help of simulation analysis and on-site experimental experience, if the distance between the response sensor and the excitation sensor is too small, the magnetic fields of the two may be coupled, affecting the on-line measurement of the frequency response signal. The height difference between the response sensor and the excitation sensor should be no less than 30 cm.

[0042] (3) Connect the anti-saturation coils of the three-phase response sensors in parallel through the cable wires. After ensuring that the parallel interface is firmly connected, connect the aviation plug connecting wires of each phase, combine the sensors, and tighten the sensor interface screws.

[0043] (4) Connect the input end of the excitation sensor to the signal generation module through the cable wire, and connect the output end of the response sensor to the weak high-frequency signal processing module through the cable wire. After wiring is completed, perform the measurement.

[0044] 2. The signal generation module injects a 160V swept-frequency voltage signal into the winding of the A-phase excitation sensor through the polyphase switching switch. The swept-frequency range is 1 kHz - 1 MHz. Using the principle of magnetic field coupling, the A-phase excitation sensor couples and injects the signal into the winding, generating an induced current signal in the winding. The A, B, and C phase response sensors extract the induced current signal generated in the winding based on magnetic field coupling. The principle of live detection is detailed in the appendix Figure 5 .

[0045] 3. The weak high-frequency signal processing module processes the output voltage signal of the response sensor. The frequency response signal first passes through a high-pass filter to filter out the power frequency noise, and then passes through a low-pass filter to filter out the high-frequency noise above 1 MHz; then the composite integration circuit processes the low-frequency and high-frequency bands, improving the sensitivity of the 1 kHz - 10 kHz and 900 kHz - 1 MHz signals, making the measurement frequency band flat; finally, the signal enters the amplifier, first amplified 10 times by the first-stage amplifier, and then adjustable amplified 10 - 100 times by the second-stage amplifier, amplifying the frequency response signal of dozens to hundreds of microvolts to the millivolt level. Figure 4 It is a schematic diagram of the interference shielding treatment of the signal processing circuit.

[0046] 4. The signal acquisition module acquires the signals processed by the weak high-frequency signal processing module, acquires the signals of all sensors simultaneously, and after classifying and processing the acquired data, transmits them to the diagnostic analysis module for further analysis.

[0047] 5. The diagnostic analysis module calculates the signal network transfer function, and constructs the network transfer function H under the condition of ungrounded neutral point of the three-phase transformer according to the port voltage-current relationship.

[0048]

[0049] Among them, j is the imaginary symbol, ω is the angular frequency, and H(ω) is the modulus value of the transfer function corresponding to the frequency ω, which is used as the ordinate of the frequency response curve (amplitude-frequency curve).

[0050] Taking the input voltage U of the excitation sensor S (excitation signal) as a reference, it is combined with the output voltage signal U of the response sensor X1 In the formula, k T represents the proportional coefficient between the output voltage U of the response sensor X1 and the voltage U generated by the sensing system X2 , which contains the gain information of the weak signal processing circuit. X represents one of the three phases A, B, and C. For the generated frequency response function images, see Figures 6(a) and 6(b) in the attached drawings.

[0051] The signal generation module applies an excitation signal to the excitation sensor of phase A. At this time, all three-phase response sensors output signals. The frequency response curves generated by the network functions H formed by each phase are respectively denoted as A-a, A-b, and A-c.

[0052] 6. The multi-phase switch is switched to phase B, and the signal generation module injects a 160V swept-frequency voltage signal with a frequency range of 1kHz - 1MHz into the winding of the excitation sensor of phase B, and repeats steps 2 - 5 to generate frequency response curves B-a, B-b, and B-c.

[0053] 7. The multi-phase switch is switched to phase C, and the signal generation module injects a 160V swept-frequency voltage signal with a frequency range of 1kHz - 1MHz into the winding of the excitation sensor of phase C, and repeats steps 2 - 5 to generate frequency response curves C-a, C-b, and C-c.

[0054] For the generated frequency response curves, diagnostic analysis is carried out using the correlation coefficient, and the relevant calculation process is as follows:

[0055] Assume that X(k) and Y(k) are the frequency response amplitude sequences from 1kHz to 1MHz under the normal working condition of the transformer and the case of winding deformation failure respectively. The calculation process of the characteristic function is as follows:

[0056] First, calculate the standard variances of the two sequences:

[0057]

[0058] where k = 0, 1, 2,... N - 1 is the number of collected frequency points, and N is the total number of collected frequency points;

[0059] The covariance of the two sequences is:

[0060]

[0061] The normalized covariance coefficient of the two sequences is:

[0062]

[0063] The correlation coefficient that meets the engineering requirements is:

[0064]

[0065] It can be seen from the above formula that the correlation coefficient of two completely identical curves is 10, and the greater the difference, the smaller the correlation coefficient.

[0066] The frequency response curves of the three-phase windings with the same voltage level are compared longitudinally. By judging the change of the frequency response characteristics of the winding characteristic function through characteristic indexes, multiple characteristic indexes are used for comprehensive analysis. The characteristic values used are R LF (correlation coefficient in the low-frequency band), R MF (correlation coefficient in the middle-frequency band), R HF (correlation coefficient in the high-frequency band), R (correlation coefficient in the whole frequency band).

[0067] The generated frequency response curve is compared with the online database. The so-called online database refers to the live detection data obtained during the initial commissioning stage of the transformer. The results calculated by the correlation coefficient method are shown in Table 1.

[0068] Table 1 Calculation results of the characteristic values of the frequency response curve of the network function H

[0069]

[0070] Referring to the diagnostic criterion of the correlation coefficient method in the electric power industry standard DL / T911-2016 "Frequency Response Analysis Method for Winding Deformation of Power Transformers", it can be known that the three-phase windings of the transformer are in the normal winding state without deformation. From the above analysis, it can be seen that the monitoring device can realize the detection of the operation status of the transformer winding without power interruption, which is economical and reliable; it can continuously measure the live-running transformer to obtain more real and reliable data.

Claims

1. A transformer winding deformation live monitoring device for GIS substation, characterized in that: It includes signal generation module, feedback protection module, sensor module, weak high-frequency signal processing module, signal acquisition module, and diagnosis and analysis module; The feedback protection module includes a switch and a feedback unit; the sensor module includes an excitation sensor and a response sensor; the weak high-frequency signal processing module includes a filtering unit, an integration unit and an amplification unit; Among them, the signal generation module, the switching switch, the feedback unit, the excitation sensor, the response sensor, the filtering unit, the integration unit, the amplification unit, the signal acquisition module, and the diagnosis and analysis module are connected in sequence.

2. The transformer winding deformation live monitoring device for GIS substation according to claim 1 is characterized in that: Both the excitation sensor and the response sensor are open-and-closed Rogowski coil sensors, and the sensor core material is iron-based ultrafine crystal.

3. The transformer winding deformation live monitoring device for GIS substation according to claim 2 is characterized in that: The excitation sensor and response sensor are installed at the end of the cable terminal compartment of each phase on the high voltage side.

4. The transformer winding deformation live monitoring device for GIS substation according to claim 1 is characterized in that: Each level of circuit elements of the filtering unit, the integrating unit and the amplifying unit is provided with a shielding layer.

5. The transformer winding deformation live monitoring device for GIS substation according to claim 1 is characterized in that: The feedback unit is a unidirectional feedback parallel resonance device.

6. The transformer winding deformation live monitoring device for GIS substation according to claim 1 is characterized in that: The switching switch is a periodic switching switch.

7. The transformer winding deformation live monitoring device for GIS substation according to claim 3 is characterized in that: The installation method of the excitation sensor and the response sensor is as follows: Place the two halves of the excitation sensor of each phase at the end of the cable terminal compartment of each phase on the high-voltage side, connect the aviation plug connection line, combine the excitation sensors, and tighten the interface screws; Place two halves of the response sensor of each phase at the end of the cable terminal compartment of each phase on the high-voltage side. The response sensor puts the current metal sheath grounding wire and the cable body together in the center of the response sensor; Connect the anti-saturation coils of the three-phase response sensors in parallel through cables. After the parallel interface is connected and tightened, connect the aviation plug connection wires of each phase, combine the response sensors, and tighten the interface screws; The input end of the excitation sensor is connected to the signal generating module through a cable, and the output end of the response sensor is connected to the weak high-frequency signal processing module through a cable.

8. The transformer winding deformation live monitoring device for GIS substation according to claim 7 is characterized in that: The height difference between the response sensor and the excitation sensor is not less than 30cm.

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