Transformer bushing system with self-diagnosis function

Abstract

A transformer bushing system with a self-diagnosis function comprises A-phase, B-phase and C-phase capacitive bushings with the same voltage class, a secondary capacitive voltage divider and a voltage summary signal box, wherein the secondary capacitive voltage divider and the voltage summary signal box are matched with each other. The transformer bushing system is used as complete equipment in a combined manner during operation. Compared with three-phase bushings of the same voltage level, the three-phase bushings of the same voltage level are not instantaneous voltages, but are compared by firstly monitoring an effective voltage mean value of the three-phase voltages within a certain time and then comparing, and when a certain phase is obviously increased, an early warning signal is sent out. The dry-type bushing suitable for the capacitive insulation structure comprises an RIP sleeve, an RIS sleeve and the like, two measuring taps are arranged at the positions, close to the grounding position, of the bushing, the part led out from the outermost layer is always grounded during operation, the part led out from the secondary end screen is connected with a voltage acquisition input port of a capacitive voltage divider, and the risk that the end screen is out of the ground during operation of the bushing is avoided.

Description

Technical Field

[0001] The invention belongs to the field of transformer safety, and in particular relates to a transformer bushing system with a self-diagnosis function. Background Art

[0002] Capacitor dry bushings (RIP, RIS bushings, etc., hereinafter referred to as dry bushings) are generally considered "maintenance-free" and have now become an established solution for many engineering applications. Dry bushings and oil-impregnated paper capacitor bushings (OIP bushings) have the same basic design. The capacitor core is made of continuously wound paper or fiber cloth, etc. At the same time, aluminum foil or semiconductor tape is inserted at precise positions, and the electric field is uniformed by capacitor grading. After winding, the capacitor core is impregnated in epoxy resin or oil (OIP) under vacuum and heating conditions. Unlike oil OIP bushings, the capacitor core of resin-impregnated paper bushings is solid.

[0003] For OIP bushings, the increase in dielectric loss factor tanδ is a well-known aging parameter. In addition, DGA may also give useful information about operational reliability. Any increase in the main capacitance C1 indicates that a local breakdown has occurred. It is more difficult to diagnose these bushings with local breakdown between capacitor screens, because the failure mechanism may occur between two adjacent offline tests. Therefore, it is possible that no abnormality will be detected before a sudden and rapid complete breakdown occurs. After the first local breakdown, a complete insulation breakdown may follow, further leading to catastrophic failures. According to statistics, 80% of transformer burning accidents are caused by OIP bushing failures.

[0004] For dry bushings, any local breakdown is limited to a specific location and does not affect the rest of the capacitor core. This is due to the fact that the capacitor core of the bushing is solid. In OIP bushings, the generated gas and contaminated oil can diffuse throughout the capacitor core. Dry bushings do not contain oil, so there is no oil aging problem. In contrast, in the case of dry bushings, there is no correlation between local breakdown and the remaining capacitor core. The remaining life of dry bushings after the first local breakdown is usually much longer than that of OIP bushings. This means that detecting local breakdown during offline maintenance may be a sufficient parameter to evaluate operational reliability.

[0005] In order to judge the insulation status of the bushing during operation, improving the bushing status monitoring perception ability is an effective means to achieve fault early warning. In recent years, although various types of bushing monitoring (such as dielectric loss capacitance, capacitance current, etc.) have been applied, the overall development is slow. Operating units generally reflect many risks such as high false alarm rate of bushing monitoring and unreliable grounding of the device, which increases the maintenance workload of grassroots units and has little willingness to apply it. In addition, the voltage on the high-voltage side of the power transformer is greatly affected by the system voltage fluctuation, while the phase-to-phase voltage is basically the same. Even if the voltage monitoring method is adopted, single-phase monitoring still has false alarms. Through research and analysis, it is believed that the main reasons are the insufficient integrated design of the bushing body and the monitoring device, the low reliability of the device, and the high cost of the monitoring device. Summary of the invention

[0006] The present invention aims to provide a transformer bushing system with a self-diagnosis function to solve the technical problems of transformer voltage monitoring and early warning.

[0007] To achieve the above object, the specific technical solution of a transformer bushing system with self-diagnosis function of the present invention is as follows:

[0008] A transformer bushing system with a self-diagnosis function, characterized in that it comprises three-phase A, B, and C capacitor bushings of the same voltage level connected to the transformer, a secondary capacitor voltage divider corresponding to the bushing, and a voltage summary signal box;

[0009] The secondary capacitor voltage divider converts the primary voltage output by the bushing into a secondary voltage and transmits it to the voltage summary signal box. The voltage summary signal box monitors the input voltage value and issues a warning signal for abnormal voltage.

[0010] As a further improvement of the present invention, the voltage summary signal box includes a logic operation unit and an early warning module. The logic operation unit monitors the secondary voltage output by the secondary capacitor voltage divider. When an abnormal state occurs, the early warning module sends a warning signal.

[0011] As a further improvement of the present invention, the logic operation unit calculates the effective secondary voltage average of the bushing monitored within a certain period of time, compares the monitored secondary voltage with the effective voltage average, and issues a warning signal when an abnormal increase is found.

[0012] As a further improvement of the present invention, the bushing includes a terminal connected to the transformer, a capacitor core connected to the terminal, an insulating sleeve wrapped around the outside of the capacitor core, and an end-screen tap and a voltage tap connected to the capacitor core; the end-screen tap is grounded, and the voltage tap is connected to the secondary capacitor voltage divider.

[0013] As a further improvement of the present invention, the capacitor core includes a central conduit, a capacitor screen and an insulating material wound outside the central conduit; the capacitor screen includes an end screen at the very end and a secondary end screen closest to the end screen.

[0014] As a further improvement of the present invention, the bushing is a capacitor-type dry bushing, the capacitor core is wrapped with aluminum foil or semiconductor tape outside the central conduit as an electrode, and the insulating material is resin-impregnated paper or fiber cloth.

[0015] As a further improvement of the present invention, the last panel tap is led out from the last panel, and the voltage tap is led out from the second last panel.

[0016] As a further improvement of the present invention, the secondary capacitor voltage divider includes a secondary voltage divider capacitor composed of low-voltage capacitors connected in parallel, a varistor, a protection resistor and a discharge tube; the capacitance of the secondary voltage divider capacitor is adjusted according to the bushing and the output voltage requirements.

[0017] As a further improvement of the present invention, the secondary capacitor voltage divider converts the primary voltage U1 output by the bushing into a secondary voltage U2 and measures the secondary voltage U2. The calculation formula of the secondary voltage U2 is: U2 = U1*C1 / (C1+C f ), where U1 is the primary voltage output by the bushing, C1 is the main capacitance of the bushing, C f is the secondary voltage-dividing capacitor.

[0018] Beneficial effects:

[0019] By integrating the self-diagnosis function, the system can monitor the voltage status of the bushing in real time, detect anomalies in time, and thus prevent failures and accidents, significantly improving the reliability of the power system. By monitoring voltage anomalies and issuing early warning signals, the system reduces the risk of fire and explosion caused by bushing failures and enhances the safety of the power system. The self-diagnosis function reduces the reliance on regular manual inspections, reduces maintenance costs and workload, and improves the efficiency and accuracy of maintenance. By detecting and preventing potential failures early, the system helps to extend the service life of the bushing and reduce the frequency of replacement, thereby reducing long-term operating costs.

[0020] The design of the secondary capacitor voltage divider ensures accurate conversion from primary to secondary voltage, improving the accuracy of voltage monitoring. The design of the capacitor-type dry bushing makes it more adaptable to environmental changes and suitable for various environmental conditions, including temperature and humidity changes. The logic operation unit in the voltage summary signal box is able to perform a comprehensive analysis of multi-phase voltages, reducing the possibility of false alarms and improving the accuracy of the early warning system. The system is able to monitor multi-phase voltages in real time and quickly issue early warning signals when anomalies are detected, providing timely feedback to operators so that preventive measures can be taken. By comparing the effective voltage means of multi-phase voltages, the system can detect voltage imbalances in a timely manner, which helps maintain the stability of the power system.

[0021] The system design allows easy integration with existing power systems and can be expanded as needed to accommodate power facilities of different sizes. Since the system can provide early warning of potential failures, it reduces the risk of unexpected power outages and ensures the continuity of power supply. The system brings significant economic benefits to power operators by reducing maintenance costs, reducing failure rates and extending the life of casings.

[0022] In summary, the transformer bushing system with self-diagnosis function provides higher reliability, safety and economy for the power system through its advanced monitoring and early warning mechanism, and is an important technological advancement in the power industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of a transformer bushing system with a self-diagnosis function according to the present invention;

[0024] Figure 2 is a schematic diagram of the casing structure;

[0025] Figure 3 It is a schematic diagram of the capacitor core structure;

[0026] Explanation of the marks in the figure: 1000, bushing; 1100, terminal; 1200, capacitor core; 1210, center conduit; 1220, capacitor screen; 1221, end screen; 1222, second end screen; 1230, insulating material; 1300, insulating sleeve; 1400, end screen tap; 1500, voltage tap; 2000, secondary capacitor voltage divider; 3000, voltage summary signal box. DETAILED DESCRIPTION

[0027] In order to better understand the purpose, structure and function of the present invention, a transformer bushing system with a self-diagnosis function of the present invention is further described in detail below with reference to the accompanying drawings.

[0028] Implementation example:

[0029] like Figure 1 The transformer bushing system with self-diagnosis function shown in the figure includes three-phase A, B, C capacitor bushings 1000 of the same voltage level connected to the transformer, and correspondingly configured with three sets of secondary capacitor voltage dividers 2000 and voltage summary signal boxes 3000.

[0030] like Figure 2 In the capacitor-type dry bushing shown, the terminal 1100 is located at the top of the bushing 1000 and is used to connect the external high-voltage conductor; the capacitor core 1200 is the main capacitor element inside the bushing, which is used to evenly distribute the electric field and improve the insulation performance; the insulating sleeve 1300 is wrapped around the outside of the bushing 1000 to provide external insulation to prevent arc discharge and flashover. The design of the composite umbrella sleeve can increase the creepage distance and improve the insulation performance; the end screen tap 1400 is led out from the capacitor core 1200 and grounded, which helps to provide an effective electric field shielding, reduce the electric field strength near the end screen, and prevent local discharge and breakdown. Grounding can eliminate the charge that may accumulate on the end screen and avoid the potential difference and potential discharge caused by charge accumulation; the voltage tap 1500 is led out from the capacitor core 1200 and connected to the secondary capacitor divider 2000, and can also be directly grounded when not in use.

[0031] like Figure 3 The capacitor core 1200 shown is a series coaxial cylindrical capacitor composed of aluminum foil wrapped around the center conduit 1210 as an electrode and epoxy impregnated paper as an inter-electrode medium. The capacitor core 1200 is vacuum dried to remove the internal air and moisture, and is vacuum impregnated with epoxy resin with qualified treatment and excellent electrical performance, so that the sleeve has the specified electrical performance and sufficient performance margin. The center conduit 1210 is the central part of the capacitor core 1200, made of conductive material, and connected to the high-voltage line of the transformer; the capacitor screen 1220 is aluminum foil wrapped around the outside of the center conduit 1210; the insulating material 1230 is placed between the center conduit 1210 and the capacitor screen 1220 and between the capacitor screens 1220 to provide electrical insulation to ensure that no short circuit occurs between each capacitor screen 1220 and the center conduit 1210. The end of the capacitive screen 1220 is the final screen 1221 , and the closest to the final screen 1221 is the next final screen 1222 . The final screen tap 1400 is led out from the final screen 1221 , and the voltage tap 1500 is led out from the next final screen 1222 .

[0032] The secondary capacitor voltage divider 2000 is used to convert the primary voltage of the transformer bushing into a secondary voltage and perform effective measurement. The capacitance of the secondary voltage divider device is calculated based on the given primary end-screen bushing voltage signal, the ratio of the predetermined rated secondary output voltage and the capacitance inside the bushing, according to the formula U2 = U1*C1 / (C1+C f ) is calculated, where U1 is the primary voltage output by the bushing, U2 is the rated secondary output voltage, C1 is the main capacitance of the bushing, and Cf is the secondary voltage divider capacitor. To make the voltage divider device safer and more reliable, C f It is usually composed of multiple capacitors in parallel, and a discharge tube (usually a TVS diode is used to prevent the instantaneous voltage shock at the port from causing damage to the subsequent circuit), a varistor and related protection resistors are added to the unit box.

[0033] The voltage summary signal box 3000 is connected to the secondary capacitor voltage divider 2000 and includes a logic operation unit and an early warning module. The logic operation unit calculates the effective secondary voltage mean of the monitored bushing within a certain period of time, compares the monitored three-phase voltage with the effective voltage mean, and issues an early warning signal when an abnormal increase is found. In this embodiment, the light flashes and the buzzer emits an audible and visual alarm at the same time. The voltage summary signal box can use the working power supply of the nearby control cabinet, or a high-performance UPS battery power supply. At the same time, it is transmitted to the monitoring platform of the main control room through a wired or wireless network.

[0034] The transformer bushing system with self-diagnosis function of the present invention integrates advanced monitoring and protection devices, and sets two measurement taps near the grounding of the bushing. The taps drawn from the outermost layer are always grounded during operation, and the taps drawn from the second last screen are connected to the voltage acquisition input port of the capacitor voltage divider device, so as to avoid the risk of the last screen losing ground during bushing operation, and significantly improve the operational safety and reliability of the transformer. The system can not only monitor and warn potential faults in real time, but also has the advantages of maintenance-free, environmentally friendly, efficient data management and remote monitoring, providing a strong guarantee for the stable operation of the power system.

[0035] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A transformer bushing system with self-diagnosis function, characterized in that: It includes three-phase A, B, C capacitor bushings of the same voltage level connected to the transformer, a secondary capacitor voltage divider corresponding to the bushing, and a voltage summary signal box; The secondary capacitor voltage divider converts the primary voltage output by the bushing into a secondary voltage and transmits it to the voltage summary signal box. The voltage summary signal box monitors the input voltage value and issues a warning signal for abnormal voltage.

2. The transformer bushing system with self-diagnosis function according to claim 1, characterized in that: The voltage summary signal box includes a logic operation unit and an early warning module. The logic operation unit monitors the secondary voltage output by the secondary capacitor voltage divider. When an abnormal state occurs, the early warning module sends a warning signal.

3. The transformer bushing system with self-diagnosis function according to claim 2, characterized in that: The logic operation unit obtains the effective secondary voltage mean value of the bushing monitored within a certain period of time by calculation, compares the monitored secondary voltage with the effective voltage mean value, and issues a warning signal when an abnormal increase is found.

4. The transformer bushing system with self-diagnosis function according to claim 1, characterized in that: The bushing includes a terminal connected to the transformer, a capacitor core connected to the terminal, an insulating sleeve wrapped around the outside of the capacitor core, and an end-screen tap and a voltage tap connected to the capacitor core; the end-screen tap is grounded, and the voltage tap is connected to the secondary capacitor voltage divider.

5. The transformer bushing system with self-diagnosis function according to claim 4, characterized in that: The capacitor core comprises a central conduit, a capacitor screen and an insulating material wound outside the central conduit; the capacitor screen comprises an end screen at the very end and a second end screen closest to the end screen.

6. The transformer bushing system with self-diagnosis function according to claim 5, characterized in that: The bushing is a capacitor-type dry bushing, the capacitor core is wrapped with aluminum foil or semiconductor tape outside the central conduit as an electrode, and the insulating material is resin-impregnated paper or fiber cloth.

7. The transformer bushing system with self-diagnosis function according to claim 5, characterized in that: The last screen tap is led out from the last screen, and the voltage tap is led out from the second last screen.

8. The transformer bushing system with self-diagnosis function according to claim 1, characterized in that: The secondary capacitor voltage divider comprises a secondary voltage divider capacitor formed by connecting low-voltage capacitors in parallel, a varistor, a protection resistor and a discharge tube; the capacitance of the secondary voltage divider capacitor is adjusted according to the bushing and the output voltage requirements.

9. The transformer bushing system with self-diagnosis function according to claim 8, characterized in that: The secondary capacitor voltage divider converts the primary voltage U1 output by the bushing into a secondary voltage U2 and measures the secondary voltage U2. The calculation formula of the secondary voltage U2 is: U2 = U1*C1 / (C1+C f ), where U1 is the primary voltage output by the bushing, C1 is the main capacitance of the bushing, C f is the secondary voltage-dividing capacitor.

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