A one-time neutral point access type flow-sensitive harmonic elimination device

Abstract

The application belongs to the technical field of flow-sensitive harmonic elimination devices, and particularly relates to a one-time neutral point access type flow-sensitive harmonic elimination device, which comprises a unit composed of PTC thermistors and PPTC thermistors in series, and then connected in parallel with a thin film capacitor and a pressure sensitive resistor, the unit is connected through N series to form a main circuit, the main circuit is connected with a PT one-time neutral point through a wire and the end is grounded; the device further comprises a wiring terminal, a base, a shell, a circuit board and filling glue, the wiring terminal is fixedly connected with the PT one-time neutral point through a screw, the base is fixed on a grounding row, the shell wraps the circuit board, the filling glue is filled in the shell, and the circuit board is integrated with the PTC thermistors, the PPTC thermistors, the thin film capacitor and the pressure sensitive resistor.

Description

Technical Field

[0001] This invention belongs to the technical field of flow-sensitive harmonic elimination devices, and particularly relates to a primary neutral point access flow-sensitive harmonic elimination device. Background Technology

[0002] In power systems, semi-insulated electromagnetic voltage transformers (PTs) are key devices for voltage measurement and protection, and are widely used in medium and high voltage scenarios such as 6kV-35kV. However, during PT operation, resonant overvoltages can easily be caused by ferromagnetic saturation, leading to neutral point potential shift and abnormal current increase. This not only affects metering accuracy but may also damage the PT itself and associated power equipment, and in severe cases, even cause power outages, threatening the safe and stable operation of the system.

[0003] Existing current-sensitive harmonic suppression devices mostly employ a single sensing element or a simple series-parallel structure, which has significant limitations: some devices have a simple response mechanism, making it difficult to adapt to complex resonance scenarios with rapid current changes and slow current increases, resulting in insufficient harmonic suppression timeliness; some devices are adapted to fixed voltage levels, lacking targeted designs for different voltage level PTs, resulting in poor versatility; at the same time, the heat dissipation performance, insulation strength, and overvoltage withstand protection design of traditional devices are not perfect, and they are prone to insufficient stability under high voltage and high current conditions, failing to fully meet the power system's requirements for efficient and reliable use of harmonic suppression devices. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned technical problems by providing a single-neutral-point-connected current-sensitive harmonic elimination device.

[0005] In view of this, the present invention provides a primary neutral point access current-sensitive harmonic elimination device, comprising a unit consisting of a PTC thermistor and a PPTC thermistor connected in series, and then connected in parallel with a thin film capacitor and a varistor. The unit is connected in series with N units to form a main circuit. The main circuit is connected to the primary neutral point of the PT via a wire and the end is grounded. The device also includes terminals, a base, a housing, a circuit board, and filler adhesive. The terminals are fixed to the primary neutral point of the PT by screws. The base is fixed to the grounding bar. The housing encloses the circuit board. The filler adhesive fills the inside of the housing. The circuit board integrates a PTC thermistor, a PPTC thermistor, a film capacitor, and a varistor.

[0006] Preferably, the PTC thermistor has a withstand voltage of VDC 800V-1000V, an R25℃ of 0.8-1.0KΩ, and a Curie temperature of 70-100℃.

[0007] Preferably, the PPTC thermistor has a withstand voltage of VDC 800V-1000V, an R value of 40-60Ω at 25℃, an operating current of 50-100mA, and an operating time of ≤1.5S.

[0008] Preferably, the film capacitor has a withstand voltage of VDC 1000V-2000V and a capacitance of 50-80nF.

[0009] Preferably, the filler is GN-7055 two-component addition-type liquid silicone rubber with a breakdown strength of 20kV / mm and a thermal conductivity of 5.0W / (mK).

[0010] Preferably, the base is made of aluminum alloy and is fixed to the grounding bar with bolts; the outer shell is made of epoxy resin with high thermal conductivity.

[0011] Preferably, the device is adapted to 6kV-20kV semi-insulated electromagnetic voltage transformers, in which case the clamping voltage of the varistor is Vac120V, and the number of units connected in series is N=25.

[0012] Preferably, the device is adapted to a 35kV semi-insulated electromagnetic voltage transformer, in which case the clamping voltage of the varistor is Vac125V, and the number of units connected in series is N=40.

[0013] Preferably, when the PT experiences a ferromagnetic saturation resonance overvoltage, the PTC thermistor and the PPTC thermistor work together to achieve a two-stage resistance transformation. When the varistor reaches the upper limit of the withstand voltage at the N terminal of the semi-insulated PT, it conducts to form a grounding discharge path.

[0014] The beneficial effects of this invention are as follows: By using a unit structure consisting of a PTC thermistor and a PPTC thermistor connected in series, and then in parallel with a thin-film capacitor and a varistor, combined with a design of N units connected in series, a rapid response mechanism for two-stage resistance value transformation is achieved. Whether it is a scenario where the neutral point current rapidly changes to the PPTC operating current during PT ferromagnetic saturation resonance, or a scenario where the current rises slowly but does not reach the operating current, the graded action of both can precisely limit the current increase and efficiently eliminate resonance. At the same time, the varistor conducts and discharges in a timely manner when the PTN terminal reaches the upper limit of its withstand voltage, fundamentally preventing equipment damage due to overvoltage and overcurrent, and ensuring the stable operation of the power system.

[0015] For semi-insulated power supplies (PTs) with different voltage levels from 6kV to 20kV and 35kV, the device achieves targeted adaptation by precisely matching component specifications and the number of units connected in series, significantly improving its versatility. The combined design of an aluminum alloy base, a high thermal conductivity epoxy resin shell, and a high thermal conductivity silicone filler not only enhances heat dissipation but also improves the insulation strength between components. Coupled with core components with excellent voltage and temperature resistance, the device can maintain stable and reliable operation under high voltage and complex conditions, effectively compensating for the shortcomings of traditional harmonic suppression devices, such as slow response, poor adaptability, and insufficient stability. Attached Figure Description

[0016] Figure 1 This is a circuit diagram of a current-sensitive harmonic elimination device applied to a semi-insulated PT primary neutral point connection type according to the present invention; Figure 2 This is an isometric view of a current-sensitive harmonic elimination device applied to a semi-insulated PT primary neutral point connection type according to the present invention; Figure 3 This is a cross-sectional view of a current-sensitive harmonic elimination device applied to the primary neutral point of a semi-insulated PT according to the present invention.

[0017] In the diagram: 1. PTC thermistor; 2. PPTC thermistor; 3. Film capacitor; 4. Terminal; 5. Varistor; 6. Wiring terminal; 7. Base; 8. Housing; 9. Circuit board; 10. Filler adhesive. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0019] This invention provides a current-sensitive harmonic elimination device for use in a semi-insulated PT primary neutral point connection, which is achieved through the following technical solution.

[0020] A current-sensitive harmonic elimination device for use with a semi-insulated PT primary neutral point connection, circuit diagram as follows: Figure 1 As shown, a PTC thermistor 1 and a PPTC thermistor 2 are connected in series, while a thin-film capacitor 3 and a varistor 5 are connected in parallel. These components form a unit, and N units are connected in series. A wire 4 is connected to the primary neutral point of the PT and grounded at its end. This enables the PTC and PPTC to cooperate in a graded operation, forming a two-stage resistance transformation, which works together to achieve a fast response to the resistance change.

[0021] A current-sensitive harmonic elimination device for use with a semi-insulated PT primary neutral point connection, comprising the following main functional components: Figure 2 ,3 It includes terminal blocks 6, base 7, housing 8, circuit board 9, and filler adhesive 10.

[0022] Terminal 6 is fixedly connected to the primary neutral point of the PT by screws; The base 7 is made of aluminum alloy and is fixed to the grounding bar with bolts. The outer casing 8 is made of epoxy resin material with high thermal conductivity; The circuit board 9 consists of a PCB board, a PTC thermistor 1, a PPTC thermistor 2, a thin film capacitor 3, and a varistor 5; Filler 10 is filled with high thermal conductivity silicone to improve heat dissipation and insulation strength between components on the PCB circuit board.

[0023] The aforementioned current-sensitive harmonic elimination device for use with a primary neutral point of a semi-insulated PT is available in two models: one is for use with a semi-insulated electromagnetic voltage transformer in the 6kV-20kV range, and the other is for use with a semi-insulated electromagnetic voltage transformer in the 35kV range.

[0024] Semi-insulated electromagnetic voltage transformers for 6kV-20kV applications: The PTC thermistor 1 is a thermistor with a withstand voltage of VDC 800V-1000V, an R value of 0.8-1.0KΩ at 25℃, and a Curie temperature of 70-100℃. The PPTC thermistor 2 is a thermistor with a withstand voltage of VDC 800V-1000V, R25℃ of 40-60Ω, operating current of 50-100mA, and operating time of less than or equal to 1.5S. The thin-film capacitor 3 is a thin-film capacitor with a withstand voltage of VDC1000V-2000V and a resistance of 50-80nF; The varistor 5 is a varistor with a clamping voltage of Vac120V; The aforementioned semi-insulated electromagnetic voltage transformer primary neutral point access current-sensitive harmonic elimination device for 6kV-20kV uses the above-mentioned components, with PTC thermistor 1 and PPTC thermistor 2 connected in series, and simultaneously connected in parallel with film capacitor 3 and varistor 5 to form a unit. The main circuit of the device is formed by connecting N units in series, where N equals 25. The filler is made of GN-7055 two-component addition-type liquid silicone rubber with a breakdown strength of 20kV / mm and a thermal conductivity of 5.0W / (mK).

[0025] Semi-insulated electromagnetic voltage transformers for 35kV applications: The PTC thermistor 1 is a thermistor with a withstand voltage of VDC 800V-1000V, an R value of 0.8-1.0KΩ at 25℃, and a Curie temperature of 70-100℃. The PPTC thermistor 2 is a thermistor with a withstand voltage of VDC 800V-1000V, R25℃ of 40-60Ω, operating current of 50-100mA, and operating time of less than or equal to 1.5S. The thin-film capacitor 3 is a thin-film capacitor with a withstand voltage of VDC1000V-2000V and a resistance of 50-80nF; The varistor 5 is a varistor with a clamping voltage of Vac125V; The aforementioned harmonic elimination device for a 35kV semi-insulated electromagnetic voltage transformer with primary neutral point access current-sensitive type uses the above-mentioned components, with PTC thermistor 1 and PPTC thermistor 2 connected in series, and simultaneously connected in parallel with film capacitor 3 and varistor 5 to form a unit. The main circuit of the device is formed by connecting N units in series, where N equals 40. The filler is made of GN-7055 two-component addition-type liquid silicone rubber with a breakdown strength of 20kV / mm and a thermal conductivity of 5.0W / (mK).

[0026] In field applications, terminal 6 is connected to the primary neutral point of the PT, and base 7 is fixed to the grounding busbar with bolts. When the PT experiences a ferroresonant saturation resonance overvoltage, the neutral point shifts. If the neutral point current rapidly increases to the operating current of the PPTC thermistor, the resistance of the PPTC thermistor first rises rapidly, and then rises rapidly again as the temperature increases, thus limiting the rapid increase of current and eliminating resonance. If the neutral point current rises slowly and does not reach the operating current of the PPTC thermistor, the resistance of the PPTC thermistor first rises, and then rises rapidly as the current increases to reach the operating current of the PPTC thermistor, thus limiting the rapid increase of current and eliminating resonance. In practical applications, these two processes can occur individually, alternately, or simultaneously, achieving two-stage resistance transformation and working together to achieve a rapid response in resistance transformation. If the N-terminal of the semi-insulated PT reaches the upper limit of its withstand voltage (3kV for 10kV type, 5kV for 35kV type) during the process of eliminating resonance in the harmonic elimination device, the varistor will conduct to form a grounding discharge path to prevent the N-terminal voltage of the semi-insulated PT from exceeding the withstand value.

[0027] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A single-neutral-point-connected current-sensitive harmonic elimination device, characterized in that: It includes a unit consisting of a PTC thermistor (1) and a PPTC thermistor (2) connected in series, and then connected in parallel with a thin film capacitor (3) and a varistor (5). The unit forms a main circuit through N series connections. The main circuit is connected to the primary neutral point of the PT via a wire (4) and the end is grounded. The device also includes a terminal block (6), a base (7), a housing (8), a circuit board (9), and a filler (10). The terminal block (6) is fixed to the primary neutral point of the PT by screws. The base (7) is fixed to the grounding bar. The housing (8) encloses the circuit board (9). The filler (10) fills the inside of the housing (8). The circuit board (9) integrates a PTC thermistor (1), a PPTC thermistor (2), a film capacitor (3), and a varistor (5).

2. The single-neutral-point-connected current-sensitive harmonic elimination device according to claim 1, characterized in that: The PTC thermistor (1) has a withstand voltage of VDC800V-1000V, an R25℃ of 0.8-1.0KΩ, and a Curie temperature of 70-100℃.

3. The single-neutral-point-connected current-sensitive harmonic elimination device according to claim 1, characterized in that: The PPTC thermistor (2) has a withstand voltage of VDC800V-1000V, an R value of 40-60Ω at 25℃, an operating current of 50-100mA, and an operating time of ≤1.5S.

4. The single-neutral-point-connected current-sensitive harmonic elimination device according to claim 1, characterized in that: The film capacitor (3) has a withstand voltage of VDC1000V-2000V and a capacitance of 50-80nF.

5. A single-neutral-point-connected current-sensitive harmonic elimination device according to claim 1, characterized in that: The filler (10) is GN-7055 two-component addition-type liquid silicone rubber with a breakdown strength of 20kV / mm and a thermal conductivity of 5.0W / (mK).

6. A single-neutral-point-connected current-sensitive harmonic suppression device according to claim 5, characterized in that: The base (7) is made of aluminum alloy and is fixed to the grounding bar with bolts; the outer shell (8) is made of epoxy resin with high thermal conductivity.

7. A single-neutral-point-connected current-sensitive harmonic elimination device according to claim 5, characterized in that: The device is compatible with 6kV-20kV semi-insulated electromagnetic voltage transformers. At this time, the clamping voltage of the varistor (5) is Vac120V, and the number of units connected in series is N=25.

8. A single-neutral-point-connected current-sensitive harmonic elimination device according to claim 1, characterized in that: The device is compatible with a 35kV semi-insulated electromagnetic voltage transformer. At this time, the clamping voltage of the varistor (5) is Vac125V, and the number of units connected in series is N=40.

9. A single-neutral-point-connected current-sensitive harmonic elimination device according to claim 1, characterized in that: When the PT experiences a ferromagnetic saturation resonance overvoltage, the PTC thermistor (1) and the PPTC thermistor (2) work together to achieve a two-stage resistance transformation. The varistor (5) conducts when the N terminal of the semi-insulated PT reaches the upper limit of the withstand voltage, forming a grounding discharge path.

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