A steep wave test loop integrated with an impulse current measurement function

Abstract

This invention discloses a steep wave test circuit integrating impulse current measurement function, comprising: a main capacitor as an energy storage element; a wavefront resistor and a wave tail resistor connected in series in the discharge main circuit of the main capacitor; the wavefront resistor controls the voltage rise time, and the wave tail resistor controls the decay time; a steepening sphere gap connected after the wavefront resistor to generate a steep wave; a loop inductance, a stray inductance existing between the conductor and the steepening sphere gap, which is an inherent inductance; a steepening capacitor, one end connected to the output terminal of the steepening sphere gap and the other end grounded, providing a low impedance path at the moment of discharge to accelerate the establishment of the voltage front and generate an extremely steep wavefront; a steep wave voltage divider connected in parallel across the test specimen to measure the steep wave voltage applied to the test specimen; a test specimen connected between the high-voltage terminal of the steep wave voltage divider and ground to withstand the impulse voltage; and a measuring coil wrapped around the test specimen or grounding wire to measure the impulse current flowing through the test specimen.

Description

Technical Field

[0001] This invention relates to the field of high voltage testing technology, and more specifically, to a steep wave test circuit with integrated impulse current measurement function. Background Technology

[0002] Disc suspension insulators are widely used in power transmission lines, serving multiple functions including electrical insulation, mechanical support, adaptability to environmental changes, and ensuring power system stability. These functions collectively ensure the safe and reliable operation of the power system, providing a solid power guarantee for economic and social development.

[0003] Steep wave test (air impulse breakdown test) is a key method for verifying the internal breakdown performance of UHV disc insulators (especially type B insulators), and can effectively detect potential defects in the insulator head structure, bonding process, etc. To ensure the consistency and comparability of test results, the national standard GB / T 20642-2006 clearly specifies the test voltage waveform (e.g., wavefront time 100~200ns, amplitude deviation not exceeding 10%) and test procedures.

[0004] Existing steep-wave test circuits typically consist of an impulse voltage generator, a steepening spherical gap, a steepening capacitor, and a measurement system. Due to differences in the capacity of the impulse voltage generator, the amplitude and waveform of the current flowing through the insulator under test vary significantly during steep-wave testing, affecting the comparability of the test requirements. However, traditional testing methods only focus on acquiring and interpreting the voltage waveform across the test object, without simultaneously measuring the instantaneous impulse current flowing through the insulator. This leads to the following problems: It is impossible to quantify the differences in current impulse intensity exerted on the test insulator by impulse voltage generators of different capacities; It is difficult to assess the current withstand capability of insulators under steep wave impacts; Comparing voltage waveforms only between different laboratories cannot fully reproduce current stress conditions, affecting the comparability of test results.

[0005] Therefore, there is an urgent need for a device and method that can accurately measure the instantaneous impulse current flowing through a disc insulator during a steep wave test. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a steep wave test circuit that integrates impulse current measurement functionality.

[0007] According to one aspect of the present invention, a steep wave test circuit integrating impulse current measurement function is provided, comprising: Main capacitor: As an energy storage element, it is charged in parallel with charging resistors. When discharging, its voltage forms a waveform through the tail resistor and the head resistor. Wavefront resistor and wavetail resistor: connected in series in the main discharge circuit of the main capacitor; the wavefront resistor controls the voltage rise time, and the wavetail resistor controls the decay time. Steepening spherical gap: Connected after the wavefront resistor, when the main capacitor voltage is charged to a certain value, the main spherical gap breaks down, which then triggers the steepening spherical gap, reducing the circuit inductance and generating a steep wave; Loop inductance: Stray inductance existing between the conductor and the steepened ball gap, belonging to inherent inductance; Steepening capacitor: One end is connected to the output terminal of the steepening spherical gap, and the other end is grounded. It provides a low impedance path at the moment of discharge, accelerates the establishment of the voltage front, and is used to generate an extremely steep wavefront. Steep wave voltage divider: Connected in parallel across the test sample to measure the steep wave voltage applied to the test sample; Test sample: Connected between the high-voltage terminal of the steep-wave voltage divider and ground, to withstand impulse voltage; Measuring coil: Wrapped around the test sample or grounding wire, used to measure the impulse current flowing through the test sample.

[0008] Optionally, the steep wave test circuit with integrated impulse current measurement function adopts a self-integrating Rogowski coil, which is connected to the grounding side lead of the test insulator to achieve non-contact measurement.

[0009] Optionally, it also includes: a non-inductive coaxial shunt connected in series between the test insulator and the ground, with a resistance value not greater than 0.1Ω and a response time ≤5ns.

[0010] Optionally, it also includes: a tuning inductor and a tuning resistor connected in series between the steepening ball gap output and the test object, which, together with a steep wave voltage divider, utilize the high amplitude voltage generated by LC oscillation to cause the insulator to flash over and form a steep wave.

[0011] Optionally, the value of the tuning inductor is 5~20μH; the value of the tuning resistor is 20~60Ω.

[0012] The beneficial effects of this invention are: (1) The first realization of impulse current measurement in steep wave test: using Rogowski coil or non-inductive shunt, with a response time ≤5ns, it can accurately capture the waveform of steep wave impulse current with a wavefront time of 100~200ns, filling the gap in existing technology.

[0013] (2) Provide a complete current-voltage joint evaluation method: By synchronously recording voltage and current waveforms, the instantaneous impedance change of the insulator under steep wave impact can be calculated, which more comprehensively reflects the internal breakdown process of the insulator and improves the defect detection rate.

[0014] (3) High waveform quality: By optimizing the steepening capacitance and the steepening of the sphere gap, a steep wave waveform that conforms to the national standard is generated, with small oscillation and high amplitude accuracy, providing stable test conditions for current measurement.

[0015] (4) Reasonable layout: The compact loop layout effectively reduces the adverse effects of loop inductance on the waveform. The current sensor is installed close to the grounding terminal, minimizing the stray parameters introduced by the measurement loop and ensuring measurement accuracy.

[0016] (5) Good system compatibility: The adaptability of current measurement under different capacity impulse voltage generators is clarified. The measuring device is universal and can be transferred between different laboratories, improving the comparability of test results. Attached Figure Description

[0017] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures: Figure 1 This is a steep wave test circuit diagram with integrated impulse current measurement function provided by an exemplary embodiment of the present invention; Figure 2 This is a schematic diagram of the steep wave test circuit arrangement with integrated impulse current measurement function provided by an exemplary embodiment of the present invention. Detailed Implementation

[0018] Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0019] It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0020] Those skilled in the art will understand that the terms "first," "second," etc., in the embodiments of the present invention are only used to distinguish different steps, devices, or modules, and do not represent any specific technical meaning, nor do they indicate a necessary logical order between them.

[0021] It should also be understood that in the embodiments of the present invention, "multiple" can refer to two or more, and "at least one" can refer to one, two or more.

[0022] It should also be understood that any component, data or structure mentioned in the embodiments of the present invention can generally be understood as one or more unless explicitly defined or given contrary instructions in the context.

[0023] Furthermore, the term "and / or" in this invention is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this invention generally indicates that the preceding and following related objects have an "or" relationship.

[0024] It should also be understood that the description of the various embodiments in this invention emphasizes the differences between the various embodiments, and the similarities or similarities can be referred to each other. For the sake of brevity, they will not be described in detail.

[0025] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0026] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0027] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0028] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0029] Figure 1 This is a steep wave test circuit diagram with integrated impulse current measurement function provided in an exemplary embodiment of the present invention. (See diagram below.) Figure 1 As shown, the steep wave test circuit with integrated impulse current measurement function includes: Main capacitor: As an energy storage element, it is charged in parallel with charging resistors. When discharging, its voltage forms a waveform through the tail resistor and the head resistor. Wavefront resistor and wavetail resistor: connected in series in the main discharge circuit of the main capacitor; the wavefront resistor controls the voltage rise time, and the wavetail resistor controls the decay time. Steepening spherical gap: Connected after the wavefront resistor, when the main capacitor voltage is charged to a certain value, the main spherical gap breaks down, which then triggers the steepening spherical gap, reducing the circuit inductance and generating a steep wave; Loop inductance: Stray inductance existing between the conductor and the steepened ball gap, belonging to inherent inductance; Steepening capacitor: One end is connected to the output terminal of the steepening spherical gap, and the other end is grounded. It provides a low impedance path at the moment of discharge, accelerates the establishment of the voltage front, and is used to generate an extremely steep wavefront. Steep wave voltage divider: Connected in parallel across the test sample to measure the steep wave voltage applied to the test sample; Test sample: Connected between the high-voltage terminal of the steep-wave voltage divider and ground, to withstand impulse voltage; Measuring coil: Wrapped around the test sample or grounding wire, used to measure the impulse current flowing through the test sample.

[0030] Specifically, based on actual commissioning experience, taking the CDYH-1400kV / 35kJ impulse voltage generator (main capacitor 0.036μF, 7-stage series connection) as an example, with a 400pF steepening capacitor and a steepening circuit configuration with a ball gap distance of 60~80mm, the peak impulse current flowing through the 160kN disc insulator is approximately 13~30kA, and the wavefront time is approximately 120~180ns. When the steepening ball gap distance is too small (approximately 60mm), the waveform is prone to inflection points, and the current steepness fluctuates significantly; when the ball gap distance is adjusted to 80mm and a 60Ω tuning resistor is connected in series on the steepening output side, the current waveform tends to be smoother, and the repeatability is improved. Significant differences in the amplitude and waveform of impulse current under the same circuit parameters were observed in insulators of different models (120kN, 160kN, 210kN, 300kN, 420kN, etc.), indicating that it is necessary to collect impulse current data synchronously during steep wave tests in order to achieve quantitative comparison of test conditions between different test samples and different laboratories.

[0031] This invention proposes a steep-wave test circuit integrating impulse current measurement function, and through systematic research, determines the type of measuring device, connection method, and circuit parameter configuration. The specific technical solution is as follows: 1. For example Figure 1 As shown, the overall structure of the test circuit The test circuit includes: an impulse voltage generator body, a steepening spherical gap, a steepening capacitor, a resistive voltage divider, the test specimen, and an impulse current measuring device. The steepening capacitor and the steepening spherical gap are connected in parallel and then connected in series between the impulse voltage generator body and the test specimen. The circuit connection adopts a compact arrangement to minimize circuit inductance and stray capacitance. Figure 1 As shown: Main capacitor: As an energy storage element, it is charged in parallel with charging resistors. When discharging, its voltage forms a waveform through the tail resistor and the head resistor. Wavefront resistor and wavetail resistor: connected in series in the main discharge circuit of the main capacitor; the wavefront resistor controls the voltage rise time, and the wavetail resistor controls the decay time. Steepening spherical gap: Connected after the wavefront resistor, when the main capacitor voltage is charged to a certain value, the main spherical gap breaks down, which then triggers the steepening spherical gap, reducing the circuit inductance and generating a steep wave; Loop inductance: Stray inductance existing between the conductor and the steepened spherical gap, belonging to inherent inductance. Loop inductance impedes rapid changes in current and is detrimental to the formation of steep waves. Therefore, compact design should be adopted to minimize loop inductance; Steepening capacitor: One end is connected to the output terminal of the steepening spherical gap, and the other end is grounded. It provides a low impedance path at the moment of discharge, accelerates the establishment of the voltage front, and is used to generate an extremely steep wavefront. Steep wave voltage divider: Connected in parallel across the test sample to measure the steep wave voltage applied to the test sample; Test sample: Connected between the high-voltage terminal of the steep-wave voltage divider and ground, to withstand impulse voltage; Measuring coil: Wrapped around the test sample or grounding wire, used to measure the impulse current flowing through the test sample.

[0032] The impulse current measuring device adopts one or a combination of the following three schemes: Option 1: Use a self-integrating Rogowski coil, which is connected to the grounding lead of the insulator under test to achieve non-contact measurement without affecting the parameters of the steep wave main circuit.

[0033] Option 2: Use a non-inductive coaxial shunt connected in series between the test insulator and the ground, with a resistance value not greater than 0.1Ω and a response time ≤5ns.

[0034] Option 3 (Alternative): When it is necessary to reduce the impact on the main circuit parameters and further improve the steep wave oscillation, a tuning inductor (L≈5~20μH) and a tuning resistor (R≈20~60Ω) can be connected in series between the steepening spherical gap output and the test object. Combined with a weakly damped capacitor voltage divider (approximately 400pF), the high-amplitude voltage generated by LC oscillation causes the insulator to flashover and form a steep wave. This option eliminates the need for separate discharge of the steepening spherical gap, reduces the charging voltage of the impulse voltage generator by 30~50%, effectively reduces energy waste and test noise, and makes the oscillation after waveform truncation easier to cross zero, resulting in better matching with the standard waveform. In this option, a Rogowski coil can still be connected to the grounding side of the test object to perform impulse current measurement; the measurement principle remains unchanged.

[0035] The voltage signal output by the measuring device is connected to a high-speed oscilloscope (bandwidth ≥ 500MHz, sampling rate ≥ 5GS / s) after being matched with an impedance, and the current waveform is recorded synchronously, including current amplitude, wavefront time, half-peak time, current rate of change, etc.

[0036] Loop parameter settings Based on preliminary modeling, simulation, and experimental verification, the present invention has determined the following preferred parameter ranges: Table 1 Design range of loop parameters

[0037] When the steepening capacitance is 400pF and the sphere gap is 80mm, the peak voltage applied to the insulator can be stabilized at 2.85~3.19pu (1p.u.=145kV), with minimal waveform oscillation.

[0038] In a specific embodiment of the present invention, a CDYH-1400kV / 35kJ impulse voltage generator (main capacitor 0.036μF) is used, according to... Figure 2The circuit was constructed. The steepening capacitor was set to 400pF, the steepening sphere gap (sphere diameter 300mm) distance was set to 80mm, and the measured circuit inductance was 18μH. The impulse voltage generator output voltage was adjusted to 490kV (approximately 3.38pu). A self-integrating Rogowski coil (sensitivity 0.5mV / A, response time 3ns) was connected to the grounding side of the test object (U160B type disc suspension insulator). A LeCroy WaveRunner 8404M oscilloscope (bandwidth 4GHz, sampling rate 20GS / s) was used.

[0039] A positive polarity steep wave was applied, and the voltage wavefront time was recorded synchronously at 150 ns with a peak value of 495 kV; the current wavefront time was recorded at 145 ns with a peak value of 320 A. The waveforms were smooth with no significant oscillations. The test was repeated 5 times, with voltage peak deviation ≤3% and current peak deviation ≤5%, verifying the repeatability of the measuring device.

[0040] Table 2 Comparison of steep wave impulse test parameters for different types of insulators (CDYH-1400kV / 35kJ generator, 7-stage series connection, wavefront resistance Rf=7×120Ω / / 60Ω / / 20Ω, wave tail resistance Rt=7×6kΩ / / 280Ω, steepening capacitance 400pF, parallel 100pF auxiliary capacitor)

[0041] Note: Up is the peak cutoff voltage; T1 is the wavefront time; S=Up / T1 is the voltage steepness; all data are from the actual commissioning records of the CDYH-1400kV / 35kJ impulse voltage generator, and all tests meet the waveform requirements of GB / T 20642. For the U160B type UHV disc insulator, the synchronously measured peak impulse current is approximately 320A, and the wavefront time is approximately 145ns.

[0042] The beneficial effects of this invention are: (1) The first realization of impulse current measurement in steep wave test: using Rogowski coil or non-inductive shunt, with a response time ≤5ns, it can accurately capture the waveform of steep wave impulse current with a wavefront time of 100~200ns, filling the gap in existing technology.

[0043] (2) Provide a complete current-voltage joint evaluation method: By synchronously recording voltage and current waveforms, the instantaneous impedance change of the insulator under steep wave impact can be calculated, which more comprehensively reflects the internal breakdown process of the insulator and improves the defect detection rate.

[0044] (3) High waveform quality: By optimizing the steepening capacitance and the steepening of the sphere gap, a steep wave waveform that conforms to the national standard is generated, with small oscillation and high amplitude accuracy, providing stable test conditions for current measurement.

[0045] (4) Reasonable layout: The compact loop layout effectively reduces the adverse effects of loop inductance on the waveform. The current sensor is installed close to the grounding terminal, minimizing the stray parameters introduced by the measurement loop and ensuring measurement accuracy.

[0046] (5) Good system compatibility: The adaptability of current measurement under different capacity impulse voltage generators is clarified. The measuring device is universal and can be transferred between different laboratories, improving the comparability of test results.

[0047] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the invention to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A steep wave test circuit integrating impulse current measurement function, characterized in that, include: Main capacitor: As an energy storage element, it is charged in parallel with charging resistors. When discharging, its voltage forms a waveform through the tail resistor and the head resistor. Wavefront resistor and wavetail resistor: connected in series in the main discharge circuit of the main capacitor; the wavefront resistor controls the voltage rise time, and the wavetail resistor controls the decay time. Steepening spherical gap: Connected after the wavefront resistor, when the main capacitor voltage is charged to a certain value, the main spherical gap breaks down, which then triggers the steepening spherical gap, reducing the circuit inductance and generating a steep wave; Loop inductance: Stray inductance existing between the conductor and the steepened spherical gap, belonging to inherent inductance; Steepening capacitor: One end is connected to the output terminal of the steepening spherical gap, and the other end is grounded. It provides a low impedance path at the moment of discharge, accelerates the establishment of the voltage front, and is used to generate an extremely steep wavefront. Steep wave voltage divider: Connected in parallel across the test sample to measure the steep wave voltage applied to the test sample; Test sample: Connected between the high-voltage terminal of the steep-wave voltage divider and ground, to withstand impulse voltage; Measuring coil: Wrapped around the test sample or grounding wire, used to measure the impulse current flowing through the test sample.

2. The steep wave test circuit with integrated impulse current measurement function according to claim 1, characterized in that, A self-integrating Rogowski coil is used, which is connected to the grounding lead of the test insulator to achieve non-contact measurement.

3. The steep wave test circuit with integrated impulse current measurement function according to claim 1, characterized in that, Also includes: A non-inductive coaxial shunt is connected in series between the test insulator and the ground, with a resistance value not exceeding 0.1Ω and a response time ≤5ns.

4. The steep wave test circuit with integrated impulse current measurement function according to claim 1, characterized in that, Also includes: The steepening spherical gap output is connected in series with the tuning inductor and tuning resistor between the test sample and the steep wave voltage divider. The high amplitude voltage generated by LC oscillation causes the insulator to flash over and form a steep wave.

5. The steep wave test circuit with integrated impulse current measurement function according to claim 1, characterized in that, The value of the tuning inductor is 5~20μH; the value of the tuning resistor is 20~60Ω.

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