High-voltage capacitor partial discharge oscillation wave detection system

Abstract

The utility model discloses a high-voltage capacitor partial discharge oscillatory wave detection system, which belongs to the technical field of electrical equipment detection and comprises an oscillatory wave power supply system and an oscillatory wave partial discharge detection system which are connected in series. The oscillatory wave power supply system comprises a high-voltage direct-current power supply, a resonance reactor and a switch, the positive electrode of the high-voltage direct-current power supply is connected with one end of the switch and the input end of the resonance reactor, the other end of the switch is grounded, the output end of the resonance reactor is connected with the input end of a test capacitor, and the output end of the test capacitor is grounded. The cathode of the high-voltage direct-current power supply is grounded; the oscillatory wave partial discharge detection system comprises a special impedance and a partial discharge detection system, the input end of the special impedance is connected with the output end of the test capacitor, and the output end of the special impedance is connected with the partial discharge detection system and is grounded. The oscillatory wave partial discharge detection technology is used for detecting the insulation fault of the high-voltage high-capacity capacitor, and the problem that a high-power power supply needs to be configured for the high-capacity capacitor boost test is solved.

Description

Technical Field

[0001] The utility model belongs to the technical field of electrical equipment detection, and particularly relates to a high-voltage capacitor partial discharge oscillating wave detection system. Background Technique

[0002] The statements in this part only provide background technical information related to the present disclosure, and do not necessarily constitute prior art.

[0003] High-voltage large-capacity capacitors are essential important electrical equipment in the power grid system. The purpose of detecting partial discharge of high-voltage large-capacity capacitors is to detect internal defects of capacitors before they fail, timely understand the insulation state of equipment operation, better monitor the deterioration process of equipment, effectively understand the current true health state of equipment, give an effective early warning at the initial stage of equipment failure, and thus take measures in a timely manner.

[0004] At present, the methods for detecting partial discharge of capacitors include power frequency withstand voltage method, DC partial discharge detection method, ultrasonic detection method, etc. The power frequency withstand voltage partial discharge measurement is mostly carried out on small-capacity specimens. For large-capacity capacitors, this detection method has the disadvantages of a huge test power supply, high input cost, insufficient test sensitivity, and insufficient analysis means. In terms of its signal excitation and detection method, the DC partial discharge detection mode cannot truly reflect the fault characteristics of capacitors and cannot accurately detect insulation defects of capacitors. The ultrasonic method is the most commonly used method for detecting partial discharge of large-capacity capacitors at present. The advantage of the ultrasonic method is that it does not require a coupling capacitor to increase the power supply burden. However, the ultrasonic method also has some problems: 1) The ultrasonic sensor couples acoustic wave signals from the outer surface of the capacitor. The ultrasonic signals propagate through different media inside the capacitor, and the signal attenuation is large, resulting in low detection sensitivity and only being able to detect larger discharge signals; 2) The signals collected by the ultrasonic sensor are attenuated signals, making it difficult to confirm the actual discharge intensity and accurately measure the discharge amount; 3) The ultrasonic method cannot simplify the power supply configuration, and a set of conventional power supplies for large-capacity capacitors also requires a high cost.

[0005] At the same time, in the technology of detecting partial discharge of capacitors based on oscillating waves, most cable oscillating wave power supplies cannot meet the detection requirements of large-capacity capacitors. In the switching module (semiconductor switch) of the oscillating wave power supply system, actions will occur under the alternating voltage oscillation. When the semiconductor switch acts, it will inevitably introduce pulse interference with a relatively high frequency and strong amplitude. Content of the Utility Model

[0006] In order to solve the technical problems existing in the prior art, the utility model provides a high-voltage capacitor partial discharge oscillation wave detection system, which uses the oscillation wave partial discharge detection technology to detect the insulation faults of high-voltage large-capacity capacitors. Compared with the conventional power frequency test power supply, the oscillation wave power supply greatly reduces the volume, weight and input cost, and solves the problem of configuring a high-power power supply for the step-up test of large-capacity capacitors.

[0007] To achieve the above object, the utility model is realized through the following technical solutions:

[0008] A high-voltage capacitor partial discharge oscillation wave detection system includes an oscillation wave power supply system and an oscillation wave partial discharge detection system connected in series;

[0009] The oscillation wave power supply system includes a high-voltage DC power supply, a resonant reactor and a switch. The positive pole of the high-voltage DC power supply is respectively connected to one end of the switch and the input end of the resonant reactor. The other end of the switch is grounded. The output end of the resonant reactor is connected to the input end of the test capacitor. The negative pole of the high-voltage DC power supply is grounded. The oscillation wave partial discharge detection system includes a special impedance and a partial discharge detection system. The input end of the special impedance is connected to the output end of the test capacitor. The output end of the special impedance is connected to the partial discharge detection system and grounded.

[0010] A further technical solution is that the high-voltage DC power supply includes a step-up transformer, a voltage multiplier rectification circuit and a control module. The mains input end is connected to the input end of the control module. The output end of the control module is connected to the input end of the step-up transformer. The output end of the step-up transformer is connected to the input end of the voltage multiplier rectification circuit. The output end of the voltage multiplier rectification circuit is connected to the input end of the resonant reactor.

[0011] A further technical solution is that the control module includes a first control branch and a second control branch connected in parallel.

[0012] A further technical solution is that the first control branch is that the output end of the voltage multiplier rectification circuit is connected to the input end of the current sampling circuit. The output end of the current sampling circuit is connected to the input end of the PWM generator. The output end of the PWM generator is connected to the input end of the drive circuit. The output end of the drive circuit is connected to the input end of the full-bridge inverter.

[0013] A further technical solution is that the second control branch is that the output end of the voltage multiplier rectification circuit is connected to the input end of the voltage sampling circuit. The output end of the voltage sampling circuit is connected to the input end of the error amplifier. The output end of the error amplifier is connected to the input end of the PWM controller. The output end of the PWM controller is connected to the input end of the drive circuit. The output end of the drive circuit is connected to the input end of the Buck circuit. The output end of the Buck circuit is connected to the input end of the full-bridge inverter.

[0014] Further technical solution: The switch adopts a power electronic switch, including a thyristor and a diode connected in parallel. The anode of the thyristor is connected to the cathode of the diode, and the cathode of the thyristor is connected to the anode of the diode.

[0015] Further technical solution: The resonance reactor is a high-voltage partial-discharge-free resonance reactor.

[0016] Further technical solution: The special impedance includes a transformer. The input end of the primary winding of the transformer is connected to the output end of the test capacitor, and is respectively connected in parallel with a grading capacitor and a resistor. The output end of the secondary winding of the transformer is connected to the input end of the partial-discharge detection system.

[0017] Further technical solution: One end of the primary winding of the transformer is respectively connected to one end of the grading capacitor and the resistor, and the other end of the primary winding is respectively connected to the other end of the grading capacitor and the other end of the resistor. The other end of the grading capacitor is grounded.

[0018] Further technical solution: The oscillating wave power supply system further includes a protective resistor and a damping resistor connected in series. The input end of the protective resistor is connected to the output end of the high-voltage DC power supply. The output end of the protective resistor is respectively connected to the non-grounded end of the switch and the input end of the damping resistor. The output end of the damping resistor is connected to the input end of the resonance reactor.

[0019] Advantages of the present utility model:

[0020] The present utility model designs an oscillating wave power supply system, in which a step-up transformer is connected in series with a voltage multiplier circuit. By using the method of first passing through a first-stage step-up transformer and then through a voltage multiplier rectifier circuit for boosting, a very high voltage level can be achieved to meet the detection requirements of large-capacity capacitors with different capacities. At the same time, on the basis of an ordinary thyristor, the thyristor and the diode are combined to design a power electronic switch, which has small interference signals and little influence on the sensitivity of partial-discharge detection.

[0021] The present utility model also develops a special impedance, which can directly connect the impedance to the end of the test capacitor. Without the need to configure a large-capacity coupling capacitor, the partial-discharge signal generated by the insulation fault of the test capacitor can be detected with high sensitivity.

[0022] The present utility model uses the oscillating wave partial-discharge detection technology to detect the insulation faults of high-voltage large-capacity capacitors. Compared with the conventional power frequency test power supply, the oscillating wave power supply greatly reduces the volume, weight and investment cost, and solves the problem of the need to configure a high-power power supply for the step-up test of large-capacity capacitors. Description of the drawings

[0023] The accompanying drawings are used to provide a further understanding of the present utility model and constitute a part of the specification. They are used together with the embodiments of the present utility model to explain the present utility model and do not constitute a limitation to the present utility model.

[0024] Figure 1 It is the schematic diagram of the oscillating wave detection system for the embodiment of the present utility model;

[0025] Figure 2 It is the schematic diagram of the high-voltage DC power supply structure in the oscillating wave power supply system for the embodiment of the present utility model;

[0026] Figure 3 It is the equivalent circuit diagram of the switch in the oscillating wave power supply system for the embodiment of the present utility model;

[0027] Figure 4 It is the electrical schematic diagram of the special impedance in the oscillating wave partial discharge detection system for the embodiment of the present utility model.

[0028] Among them, HV DC is the high-voltage DC power supply, R1 is the protection resistor, R2 is the damping resistor, L is the resonance reactor, C X is the test sample capacitor, Z is the special impedance, and M is the partial discharge detection system. Specific embodiments

[0029] The following further describes the present utility model in conjunction with the accompanying drawings and specific embodiments.

[0030] See Figure 1 As shown, the embodiment of the present utility model provides a high-voltage capacitor partial discharge oscillating wave detection system, including an oscillating wave power supply system and an oscillating wave partial discharge detection system connected in series;

[0031] The oscillating wave power supply system includes a high-voltage DC power supply, a resonance reactor, and a switch. The positive pole of the high-voltage DC power supply is respectively connected to one end of the switch and the input end of the resonance reactor. The other end of the switch is grounded. The output end of the resonance reactor is connected to the input end of the test sample capacitor. The negative pole of the high-voltage DC power supply is grounded. The oscillating wave partial discharge detection system includes a special impedance and a partial discharge detection system. The input end of the special impedance is connected to the output end of the test sample capacitor. The output end of the special impedance is connected to the partial discharge detection system and grounded.

[0032] As Figure 1As shown, the oscillating wave power supply system further includes a protective resistor R1 and a damping resistor R2 connected in series. The input end of the protective resistor R1 is connected to the output end of the high-voltage DC power supply. The output end of the protective resistor R1 is respectively connected to the non-ground end of the switch and the input end of the damping resistor R2. The output end of the damping resistor R2 is connected to the input end of the resonant reactor. The protective resistor has an appropriate resistance value to ensure that the current in the circuit does not exceed the safe range, playing a role in protecting the circuit. The damping resistor is used to suppress high-frequency oscillations and improve the stability of the circuit.

[0033] Since the voltage level that the oscillating wave power supply system needs to rise to is very high, the methods of directly using a transformer to rise to the target voltage and then rectifying it into direct current and directly outputting the mains power through a voltage multiplier rectifier circuit are not suitable. In this embodiment, the method of first passing through a step-up transformer and then through a voltage multiplier rectifier circuit is used for boosting.

[0034] In this embodiment, as Figure 2 shown, the high-voltage DC power supply is used to convert the mains power into high-voltage direct current, including a step-up transformer, a voltage multiplier rectifier circuit, and a control module. The mains power input end is connected to the input end of the control module. The output end of the control module is connected to the input end of the step-up transformer. The output end of the step-up transformer is connected to the input end of the voltage multiplier rectifier circuit. The output end of the voltage multiplier rectifier circuit is connected to the input end of the resonant reactor, and high-voltage direct current is output.

[0035] The control module is used to control to obtain a predetermined and stable output voltage. The control module includes a first control branch and a second control branch connected in parallel; for the first control branch, the output end of the voltage multiplier rectifier circuit is connected to the input end of the current sampling circuit. The output end of the current sampling circuit is connected to the input end of the PWM generator. The output end of the PWM generator is connected to the input end of the drive circuit. The output end of the drive circuit is connected to the input end of the full-bridge inverter, and the output voltage of the full-bridge inverter is controlled by pulse width modulation; for the second control branch, the output end of the voltage multiplier rectifier circuit is also connected to the input end of the voltage sampling circuit. The output end of the voltage sampling circuit is connected to the input end of the error amplifier (error amplification circuit). The output end of the error amplifier is connected to the input end of the PWM controller. The output end of the PWM controller is connected to the input end of the drive circuit. The output end of the drive circuit is connected to the input end of the Buck circuit. The output end of the Buck circuit is connected to the input end of the full-bridge inverter. The output voltage of the voltage multiplier rectifier circuit is compared with the given reference voltage (i.e., the output voltage setting). If the comparison result is consistent, a stable voltage is delivered to the subsequent circuit of the oscillating wave detection system. If the comparison result does not meet the preset requirements, the duty cycle of the signal will be adjusted by the BUCK circuit, and the adjusted voltage is sent into the step-up transformer again, sampled after passing through the voltage multiplier rectifier circuit, and repeated until a predetermined and stable output voltage is obtained.

[0036] The mains input terminal is connected to the input terminal of the rectifier and filter circuit. The output terminal of the rectifier and filter circuit is connected to the BUCK circuit. When the mains power is just input, it is preliminarily rectified and filtered, converting the alternating current into direct current and filtering out the noise therein.

[0037] It should be noted that all the circuit structures, full-bridge inverters, step-up transformers, PWM controllers, and PWM generators used in the high-voltage DC power supply are existing circuit structures and electrical components. The PWM controller and PWM generator control the analog circuit through pulse width modulation technology, and use the existing PWM pulse width modulation method to control the output voltage, power, and frequency of the power supply quickly and effectively, without involving improvements in software programs. Those skilled in the art can know their implementation methods, so no more details will be elaborated here.

[0038] In some embodiments, the ER49 ferrite core is selected as the core of the step-up transformer, and the operating frequency is 60 kHz. When winding, the primary winding uses 0.55 mm enameled wire, and the secondary winding uses 0.3 mm enameled wire.

[0039] In this embodiment, as Figure 3 shown, the switch uses a power electronic switch, including a thyristor and a diode connected in parallel. The anode of the thyristor is connected to the cathode of the diode, and the cathode of the thyristor is connected to the anode of the diode. That is to say, the diode is reversely connected in parallel across the thyristor, short-circuiting the emitter junctions of the anode and cathode. After testing, the above optimization based on the ordinary thyristor has a switch-on and -off time of only a few microseconds, a working frequency of dozens of kilohertz, and significantly better on-off performance than the fast thyristor. Therefore, it is especially suitable as the power switch of the oscillating wave system and has the advantages of high temperature and high pressure resistance, fast turn-off, and low on-state voltage.

[0040] In this embodiment, the resonant reactor is a high-voltage partial discharge-free resonant reactor. In some embodiments, if the capacitance value of the detected capacitor is between 1 and 100 μF, the designed inductance of the reactor is 0.2 H. At this time, for capacitors with a capacitance in the range of 1 to 100 uF, the resonant frequency is between 35 and 424 Hz, and for most large-capacitance capacitors, their resonant frequencies can meet the requirements.

[0041] In some embodiments, if the dielectric distribution of the resonant reactor is uneven, local discharge phenomena are likely to occur. In this embodiment, in order to effectively ensure the insulation state, after comparing various insulating materials, epoxy resin has the characteristics of corrosion resistance, heat resistance, good electrical insulation performance, and small shrinkage rate. The method of casting with epoxy resin is used, and at the same time, the vacuum degree, humidity, temperature, dust, etc. of the casting environment are strictly controlled during the casting process, which greatly ensures the effectiveness of the insulation. At the same time, after the reactor is manufactured, the reactor is subjected to partial discharge detection to test its insulation performance.

[0042] When detecting the partial discharge of a large-capacity capacitor, a coupling capacitor with a larger capacitance than that of the capacitor needs to be connected in parallel, and then the detection impedance of the detection signal is connected to the tail end of the coupling capacitor. Since the capacitance of the large-capacity capacitor itself is very large, if a coupling capacitor with a larger capacitance is connected in parallel, the capacitance of the detection circuit will increase significantly. This not only requires a high power supply system but also a higher impedance current-carrying capacity. The equipment cost for building the entire test platform is extremely high and is not suitable for practical applications. In this embodiment, it is studied to remove the coupling capacitor and detect the partial discharge signal of the large-capacity capacitor by developing a special impedance and directly connecting the special impedance to the tail end of the test capacitor. Without the need to configure a large-capacity coupling capacitor, it can avoid the difficulty of building the coupling capacitor and also reduce the requirements for the power supply system.

[0043] In this embodiment, the special impedance adopts an RLC resonance circuit structure, including a transformer Lm. The input end of the primary winding of the transformer is connected to the output end of the test capacitor and is respectively connected in parallel with a grading capacitor Cm and a resistor Rm. The grading capacitor and the resistor are connected in parallel. The output end of the secondary winding of the transformer is connected to the input end of the partial discharge detection system. Specifically, one end of the primary winding of the transformer is respectively connected to one end of the grading capacitor and the resistor, and the other end of the primary winding is respectively connected to the other end of the grading capacitor and the resistor. The other end of the grading capacitor is grounded.

[0044] In some embodiments, the above special impedance uses thick hollow copper wire on the primary winding to increase the primary conduction current; the special impedance selects nickel-zinc ferrite material as the magnetic core to increase the impedance detection frequency; in order to achieve the function of improving the sensitivity of the detection signal, the number of turns of the winding can be increased; one end of the primary winding is connected in series with the grading capacitor and the other end is grounded. In this way, the ferrite core can transfer the partial discharge signal to the secondary winding, and the partial discharge signal received by the secondary winding can be connected to the partial discharge detection system for detection, meeting the test requirements of a capacitor with a maximum capacitance of 100 μF.

[0045] The special impedance is a new structure impedance specifically designed for detecting the partial discharge of large-capacity capacitors. It mainly starts from increasing the impedance detection frequency to achieve the acquisition of partial discharge signals of large-capacity capacitors.

[0046] In this embodiment, the partial discharge detection system uses an existing integrated module to detect the partial discharge of the large-capacity capacitor, which can be selected by those skilled in the art according to its functions and is not specifically limited in this embodiment.

[0047] Detailed description of the working principle:

[0048] The entire detection process can be divided into two stages: First is the DC charging stage. The high-voltage DC power supply charges the test capacitor until it reaches the preset voltage; second is the AC discharge stage, also known as the oscillation process. At this time, the switch is quickly closed, and the action time should be less than 1 μs, so that the test capacitor and the resonant reactor are in series resonance, generating a damped oscillation voltage in the test circuit, which will excite the partial discharge signal at the capacitor defect. Then, the partial discharge signal is directly collected from the end of the capacitor by a special impedance, and the signal is measured by the partial discharge detection system to achieve the detection purpose.

[0049] Although the specific implementation manners of the present invention have been described above in conjunction with the accompanying drawings, it is not a limitation to the protection scope of the present invention. Those skilled in the art should understand that, based on the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative labor are still within the protection scope of the present invention.

Claims

1. A high voltage capacitor partial discharge oscillation wave detection system, characterized in that: It includes an oscillating wave power supply system and an oscillating wave partial discharge detection system connected in series; The oscillation wave power supply system includes a high-voltage direct current power supply, a resonant inductor and a switch, wherein the positive electrode of the high-voltage direct current power supply is respectively connected to one end of the switch and the input end of the resonant inductor, the other end of the switch is grounded, the output end of the resonant inductor is connected to the input end of the test capacitor, and the negative electrode of the high-voltage direct current power supply is grounded; the oscillation wave partial discharge detection system includes a special impedance and a partial discharge detection system, the input end of the special impedance is connected to the output end of the test capacitor, and the output end of the special impedance is connected to the partial discharge detection system and grounded.

2. A high voltage capacitor partial discharge oscillation wave detection system as claimed in claim 1, characterized in that: The high-voltage DC power supply includes a boost transformer, a voltage doubler rectifier circuit and a control module. The mains input end is connected to the input end of the control module, the output end of the control module is connected to the input end of the boost transformer, the output end of the boost transformer is connected to the input end of the voltage doubler rectifier circuit, and the output end of the voltage doubler rectifier circuit is connected to the input end of the resonant inductor.

3. A high voltage capacitor partial discharge oscillation wave detection system as claimed in claim 2, characterized in that: The control module includes a first control branch and a second control branch connected in parallel.

4. A high voltage capacitor partial discharge oscillation wave detection system as claimed in claim 3, characterized in that: The first control branch is that the output end of the voltage doubler rectifier circuit is connected to the input end of the current sampling circuit, the output end of the current sampling circuit is connected to the input end of the PWM generator, the output end of the PWM generator is connected to the input end of the drive circuit, and the output end of the drive circuit is connected to the input end of the full-bridge inverter.

5. A high voltage capacitor partial discharge oscillation wave detection system as claimed in claim 3, characterized in that: The second control branch is that the output end of the voltage doubler rectifier circuit is connected to the input end of the voltage sampling circuit, the output end of the voltage sampling circuit is connected to the input end of the error amplifier, the output end of the error amplifier is connected to the input end of the PWM controller, the output end of the PWM controller is connected to the input end of the drive circuit, the output end of the drive circuit is connected to the input end of the Buck circuit, and the output end of the Buck circuit is connected to the input end of the full-bridge inverter.

6. A high voltage capacitor partial discharge oscillation wave detection system as claimed in claim 1, characterized in that: The switch adopts a power electronic switch, including a thyristor and a diode connected in parallel, wherein the anode of the thyristor is connected to the cathode of the diode, and the cathode of the thyristor is connected to the anode of the diode.

7. A high voltage capacitor partial discharge oscillation wave detection system as claimed in claim 1, characterized in that: The resonant reactor is a high-voltage non-partial discharge resonant reactor.

8. A high voltage capacitor partial discharge oscillation wave detection system as claimed in claim 1, characterized in that: The special impedance includes a transformer, the input end of the primary winding of the transformer is connected to the output end of the test capacitor, and is respectively connected in parallel with the graduation capacitor and the resistor, and the output end of the secondary winding of the transformer is connected to the input end of the partial discharge detection system.

9. A high voltage capacitor partial discharge oscillation wave detection system as claimed in claim 8, characterized in that: One end of the transformer primary winding is connected to one end of a dividing capacitor and a resistor respectively, the other end of the primary winding is connected to the other end of the dividing capacitor and the other end of the resistor respectively, and the other end of the dividing capacitor is grounded.

10. A high voltage capacitor partial discharge oscillation wave detection system as claimed in claim 1, characterized in that: The oscillating wave power supply system also includes a protective resistor and a damping resistor connected in series, the input end of the protective resistor is connected to the output end of the high-voltage DC power supply, the output end of the protective resistor is respectively connected to the non-grounded end of the switch and the input end of the damping resistor, and the output end of the damping resistor is connected to the input end of the resonant inductor.

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