A pre-magnetized pulse transformer type zero value insulator detection device and method

Abstract

The application discloses a pre-magnetized pulse transformer type zero-value insulator detection device and method, and relates to the field of insulator detection. pre and a main excitation power supply u main ; the reverse pre-excitation power supply u pre is connected with the primary side of the pulse transformer through the second switch tube Q2; the main excitation power supply u main is connected with the primary side of the pulse transformer through C1 and Q1; the pulse transformer adopts a high-remanence-ratio ferrite core; the primary side is connected with the bipolar pulse excitation circuit, and the secondary side is connected with the insulator to be detected; the primary side breakdown detection unit is connected with the primary energy storage capacitor C1; and the control and calculation unit is connected with the bipolar pulse excitation circuit and the primary side breakdown detection unit respectively. The application solves the problems of poor portability and high misjudgment rate of the existing detection device.

Description

Technical Field

[0001] This invention relates to the field of power equipment testing technology, specifically to a pre-magnetized pulse transformer type zero-value insulator testing device and method. Background Technology

[0002] Currently, disc suspension porcelain insulators are among the most widely used insulation components in high-voltage transmission lines. During long-term operation, they are susceptible to corona discharge, pollution, mechanical stress, and aging, leading to zero-value or low-resistance faults, resulting in loss of insulation performance and seriously threatening the safe and stable operation of the lines. The industry mainly uses the distributed voltage method, spark gap method, and impulse voltage method for zero-value insulator testing. Among these, the impulse voltage method is more reliable because it can directly simulate the overvoltage conditions experienced by the insulator, and its application is gradually moving from the laboratory to the field of transmission lines.

[0003] However, existing impulse voltage detection devices generally have shortcomings: traditional high-voltage impulse generators are bulky and heavy, rely on power frequency boosting circuits, and are difficult to adapt to the portable operation requirements of transmission lines; some miniaturized devices use pulse transformer structures without pre-magnetization, resulting in low core flux utilization, insufficient output high voltage, and easy waveform distortion, which cannot meet the detection requirements of ≥50kV standard impulse voltage; at the same time, existing methods can only complete a single high-voltage impulse detection, making it difficult to effectively distinguish between zero-value faults of insulators and low-resistance states caused by surface contamination, resulting in a high misjudgment rate and failing to provide accurate fault judgment basis for line operation and maintenance.

[0004] Therefore, there is an urgent need for a pre-magnetized pulse transformer type zero-value insulator detection device to solve the problems of poor portability, insufficient high voltage output, and high false judgment rate of existing detection devices. Summary of the Invention

[0005] To address these issues, the present invention provides a pre-magnetized pulse transformer type zero-value insulator detection device and method, which solves the problems of poor portability, insufficient high-voltage output, inability to effectively distinguish between zero-value faults and low surface resistance, and high false alarm rate of existing zero-value insulator detection devices.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a pre-magnetized pulse transformer type zero-value insulator detection device, characterized in that it includes a bipolar pulse excitation circuit, a pulse transformer, a primary-side breakdown detection unit, and a control and calculation unit;

[0007] The bipolar pulse excitation circuit includes: a primary-side energy storage capacitor C1, a first switching transistor Q1, a second switching transistor Q2, a first diode D1, and a reverse pre-excitation power supply u. pre and main excitation power supply u main The reverse pre-excitation power supply u preThe second switch Q2 is connected to the primary side of the pulse transformer to apply a reverse pre-excitation pulse, shifting the core operating point to near the negative saturation region; the main excitation power supply u main The primary side of the pulse transformer is connected via the primary-side energy storage capacitor C1 and the first switching transistor Q1, and is used to apply a positive main excitation pulse after pre-excitation;

[0008] The pulse transformer uses a high remanence ratio ferrite core; the primary side of the pulse transformer is connected to a bipolar pulse excitation circuit, and the secondary side is connected to the insulator under test; the pulse transformer is used to boost the low-voltage pulse on the primary side into a high-voltage impulse voltage.

[0009] The primary-side breakdown detection unit is connected to the primary-side energy storage capacitor C1 and is used to collect the voltage of the primary-side energy storage capacitor C1 in real time and calculate the voltage drop rate.

[0010] The control and calculation unit is connected to the bipolar pulse excitation circuit and the primary-side breakdown detection unit, respectively, and is used to control the pre-excitation and main excitation timing, process voltage data, and determine the insulator status.

[0011] As a preferred embodiment of a pre-magnetized pulse transformer type zero-value insulator detection device, the primary-side energy storage capacitor C1 is an electrolytic capacitor or film capacitor with low equivalent internal resistance; the reverse pre-excitation power supply is a low-voltage DC power supply; the main excitation power supply is a high-voltage DC power supply; the first diode D1 is connected in series in the main excitation circuit to block reverse current; the reverse pre-excitation circuit and the forward main excitation circuit are independent of each other and are controlled by corresponding switching transistors respectively.

[0012] As a preferred embodiment of a pre-magnetized pulse transformer type zero-value insulator detection device, the core of the pulse transformer is a ferrite core with a high remanence ratio; the number of turns on the primary side of the pulse transformer is less than the number of turns on the secondary side, and the voltage is boosted from low-voltage pulse to high-voltage impulse voltage through the turns ratio; the core is in the negative saturation region after reverse pre-excitation, and crosses from the negative saturation region to the positive saturation region during positive main excitation, thereby maximizing the utilization of magnetic flux.

[0013] As a preferred embodiment of a pre-magnetized pulse transformer type zero-value insulator detection device, the primary-side breakdown detection unit includes a voltage acquisition module, a differential calculation module, and a threshold comparison module; the voltage acquisition module is used to acquire the voltage signal of the primary-side energy storage capacitor C1; the differential calculation module is used to calculate the voltage drop rate; the threshold comparison module is used to compare the rate with a preset threshold and output a judgment signal; the detection circuit of the primary-side breakdown detection unit is located on the low-voltage side and is electrically isolated from the high-voltage output side of the pulse transformer.

[0014] As a preferred embodiment of a pre-magnetized pulse transformer type zero-value insulator detection device, the control and calculation unit includes a timing control module, a digital filtering module, and a state discrimination module. The timing control module is used to control the sequence and interval of the reverse pre-excitation pulse and the forward main excitation pulse. The digital filtering module is used to filter out high-frequency interference in the voltage signal. The state discrimination module identifies the insulator's normal, low-resistance, or zero-value state based on the voltage drop rate. When the control and calculation unit initially determines that the insulator is abnormal, it automatically triggers a low-voltage secondary excitation process to distinguish between zero-value faults and surface low-resistance states.

[0015] This invention also provides a method for detecting zero-value insulators of the pre-magnetized pulse transformer type, comprising:

[0016] After the device initialization is complete, the control and calculation unit controls the main excitation power supply u. main Charge the primary-side energy storage capacitor C1 to prepare energy for high-voltage detection.

[0017] Based on the charging completion signal of the primary-side energy storage capacitor C1, the control and calculation unit controls the second switch Q2 to turn on, and through the reverse pre-excitation power supply u pre A reverse pre-excitation pulse is applied to the primary side of the pulse transformer, causing the core operating point of the pulse transformer to move to the negative saturation region;

[0018] Based on the completion signal of the reverse pre-excitation pulse application, the control and calculation unit turns off the second switch Q2 and delays it, while controlling the first switch Q1 to turn on, and through the main excitation power supply u main A positive main excitation pulse is applied to the primary side of the pulse transformer via the primary side energy storage capacitor C1; the pulse transformer boosts the low-voltage pulse into a high-voltage impulse voltage and applies it to the insulator under test;

[0019] Based on the positive main excitation pulse applied signal, the primary-side breakdown detection unit collects the voltage signal of the primary-side energy storage capacitor C1 in real time and calculates the voltage drop rate within a set time.

[0020] The voltage drop rate is compared with a first voltage drop rate threshold; if the voltage drop rate is not greater than the first voltage drop rate threshold, the insulator under test is determined to be normal and the test ends; if the voltage drop rate is greater than the first voltage drop rate threshold, the insulator under test is determined to be abnormal and a low voltage verification process is triggered.

[0021] If the insulator under test is determined to be abnormal, the control and calculation unit delays and waits for the residual charge on the surface of the insulator under test to dissipate before controlling the main excitation power supply u. main Reduce the output voltage to perform low-voltage charging on the primary-side energy storage capacitor C1;

[0022] After the primary-side energy storage capacitor C1 completes low-voltage charging, it repeatedly performs pre-excitation, main excitation and voltage drop rate calculation under low voltage to obtain the secondary voltage drop rate.

[0023] The secondary voltage drop rate is compared with a second voltage drop rate threshold. If the secondary voltage drop rate is not greater than the second voltage drop rate threshold, the insulator under test is determined to be in a low resistance state. If the secondary voltage drop rate is greater than the second voltage drop rate threshold, the insulator under test is determined to be in a zero value state.

[0024] As a preferred embodiment of the pre-magnetized pulse transformer type zero-value insulator detection method, the reverse pre-excitation pulse and the positive main excitation pulse are time-independent and are controlled by the second switch Q2 and the first switch Q1 respectively; the volt-second product of the reverse pre-excitation and the positive main excitation satisfies the set ratio constraint, so that the magnetic core of the pulse transformer crosses from the negative saturation region to the positive saturation region;

[0025] The set ratio constraint is:

[0026] 0.3≤ (u pre ×t pre ) / (u main ×t main ≤0.8

[0027] In the formula, u pre ×t pre The volt-second product of the reverse pre-excitation; u main ×t main It is the volt-second product of the positive main excitation.

[0028] As a preferred embodiment of the detection method for zero-value insulators of pre-magnetized pulse transformers, when the primary breakdown detection unit acquires the voltage signal of the primary energy storage capacitor C1, the voltage signal is digitally filtered to remove high-frequency interference; the voltage signal acquisition and processing of the primary breakdown detection unit are both completed on the low-voltage side, maintaining electrical isolation from the high-voltage output side of the pulse transformer.

[0029] As a preferred embodiment of the pre-magnetized pulse transformer type zero-value insulator detection method, in the low-voltage verification process, the delay time of the control and calculation unit meets the requirement of dissipation of residual charge on the surface of the insulator under test; the low-voltage charging voltage of the primary side energy storage capacitor C1 is a preset ratio of the high-voltage charging voltage, and the output low-voltage impulse voltage is adapted to the verification requirements.

[0030] As a preferred embodiment of a pre-magnetized pulse transformer-type zero-value insulator detection method, the pulse transformer adopts a high remanence ratio ferrite core, and achieves the step-up conversion from low-voltage pulse to high-voltage impulse voltage through the primary and secondary turns ratio;

[0031] The primary-secondary turn ratio is:

[0032] n≥u outmax / (2πfΔBA e N1)

[0033] In the formula, n is the turns ratio of the primary and secondary sides; f is the equivalent pulse frequency; u outmax ΔB is the maximum impulse voltage that the secondary side of the pulse transformer needs to output; ΔB is the change in magnetic flux density of the magnetic core during the excitation process; A e N1 is the effective cross-sectional area of ​​the pulse transformer core; N2 is the number of turns of the primary winding of the pulse transformer.

[0034] The present invention has the following advantages:

[0035] First, the core's operating state is optimized, resulting in high conversion efficiency. A high-remanence ferrite core, combined with pre-magnetization technology, allows the core to operate across the entire hysteresis loop from the negative to the positive half-cycle, avoiding flux dead zones during unidirectional excitation. The volt-second product of the reverse pre-excitation and the main excitation is controlled within the range of 0.3 to 0.8, ensuring the core always operates from -B... max When positive excitation is initiated, the energy conversion efficiency can reach over 85%, and damage to the switching transistor caused by magnetic saturation is avoided.

[0036] Secondly, the detection circuit is simplified, and safety is improved. The breakdown state is determined by monitoring the voltage of the primary-side energy storage capacitor, eliminating the need for a voltage divider or sensor on the high-voltage side. The detection circuit is located on the low-voltage side of the primary side, completely isolated from the high-voltage output side.

[0037] Third, it adapts to complex field environments and offers high detection accuracy. By adjusting the output voltage twice, the influence of changes in the insulator surface condition under different environmental conditions on the detection results can be eliminated. The low-voltage verification mode delay design ensures that residual charges on the insulator surface are fully dissipated, improving the accuracy of secondary discrimination.

[0038] Fourth, it is highly automated and easy to operate. The control unit automatically completes the entire process of pre-magnetization, high voltage application, voltage monitoring, and fault diagnosis. Based on the voltage drop of the two excitations, it automatically outputs a clear conclusion of "normal", "low resistance" or "zero value", without the need for manual interpretation of waveforms, making it suitable for quick operation by on-site inspection personnel. Attached Figure Description

[0039] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0040] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0041] Figure 1 This is a circuit topology diagram of a pre-magnetized pulse transformer type zero-value insulator detection device provided in Embodiment 1 of the present invention;

[0042] Figure 2 This is a flowchart illustrating a method for detecting zero-value insulators using a pre-magnetized pulse transformer, as provided in Embodiment 2 of the present invention.

[0043] Figure 3 This is a schematic flowchart of a specific embodiment of the method for detecting zero-value insulators using a pre-magnetized pulse transformer, as provided in Embodiment 2 of the present invention.

[0044] Figure 4 This is a schematic diagram of the working trajectory of the hysteresis loop of the pre-magnetized pulse transformer in the detection method for a pre-magnetized pulse transformer type zero-value insulator provided in Embodiment 2 of the present invention;

[0045] Figure 5 This is a schematic diagram comparing the voltage waveforms of the primary energy storage capacitor in a pre-magnetized pulse transformer-type zero-value insulator detection method provided in Embodiment 2 of the present invention. Detailed Implementation

[0046] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Example 1

[0048] See Figure 1Embodiment 1 of the present invention provides a pre-magnetized pulse transformer type zero-value insulator detection device, including a bipolar pulse excitation circuit, a pulse transformer, a primary-side breakdown detection unit, and a control and calculation unit;

[0049] Specifically, this device adopts a modular collaborative architecture, using a bipolar pulse excitation circuit as the energy core. A pulse transformer converts low-voltage pulses into high-voltage impulses. A primary-side breakdown detection unit performs non-contact fault feature acquisition, and a control and computing unit ultimately achieves fully automated control and intelligent judgment. Compared to traditional devices, this invention overcomes the core utilization bottleneck of unidirectional excitation through pre-magnetization technology, avoids the safety risks of high-voltage side measurement through primary-side detection, and solves the problem of low-resistance misjudgment through secondary verification, achieving miniaturization, lightweight design, and high accuracy of the detection device.

[0050] The bipolar pulse excitation circuit includes: a primary-side energy storage capacitor C1, a first switching transistor Q1, a second switching transistor Q2, a first diode D1, and a reverse pre-excitation power supply u. pre and main excitation power supply u main The reverse pre-excitation power supply u pre The second switch Q2 is connected to the primary side of the pulse transformer to apply a reverse pre-excitation pulse, shifting the core operating point to near the negative saturation region; the main excitation power supply u main The primary side of the pulse transformer is connected via the primary-side energy storage capacitor C1 and the first switching transistor Q1, and is used to apply a positive main excitation pulse after pre-excitation.

[0051] Specifically, the bipolar pulse excitation circuit adopts a time-division independent control dual-loop structure, and the working process is divided into two stages: the first stage is the reverse pre-magnetization stage, in which the control and calculation unit outputs a signal to turn on the second switch Q2, and the low-voltage reverse pre-excitation power supply u pre Injecting a reverse current into the primary side of the pulse transformer causes the operating point of the magnetic core to shift from the initial residual magnetization point B. r The circuit gradually moves to the vicinity of the negative saturation region (-Bmax) to reserve the maximum flux change space for subsequent positive excitation. The second stage is the main excitation stage. After turning off the second switch Q2 and delaying for 10~50μs to ensure the core state is stable, the first switch Q1 is turned on. The pre-charged primary-side energy storage capacitor C1 releases energy to the primary side of the pulse transformer through the main excitation circuit, generating a positive high-voltage pulse. The first diode D1 is connected in series in the main excitation circuit to block reverse current from flowing back to the main excitation power supply u. main This circuit protects the power supply and switching transistors. Through pre-magnetization, the change in magnetic flux in the core is reduced from ΔB≈B in traditional unidirectional excitation. max Increase to ΔB≈2B max The utilization rate of the magnetic core is more than doubled.

[0052] The pulse transformer uses a high remanence ratio ferrite core; the primary side of the pulse transformer is connected to a bipolar pulse excitation circuit, and the secondary side is connected to the insulator under test; the pulse transformer is used to boost the low-voltage pulse on the primary side into a high-voltage impulse voltage.

[0053] Specifically, the pulse transformer achieves voltage boosting based on Faraday's law of electromagnetic induction, and selects a remanence ratio B. r / B s A high remanence ratio ferrite core (such as PC95 material) of >0.85, combined with pre-magnetization technology, can achieve full hysteresis loop utilization of the core. The primary winding receives low-voltage pulses from the bipolar pulse excitation circuit, and the voltage is boosted to a standard impulse voltage of ≥50kV by adjusting the primary-to-secondary turns ratio before being applied to the insulator under test. Because the pre-magnetization technology significantly increases the flux change, under the same output voltage requirements, the effective cross-sectional area of ​​the core can be reduced to 40%~50% of that of traditional designs, the number of primary turns can be controlled at 10~25 turns, and the number of secondary turns at 6000~10000 turns, significantly reducing the size and weight of the transformer and meeting the needs of portable field testing.

[0054] The primary-side breakdown detection unit is connected to the primary-side energy storage capacitor C1 and is used to acquire the voltage of the primary-side energy storage capacitor C1 in real time and calculate the voltage drop rate.

[0055] Specifically, the primary-side breakdown detection unit operates based on the transformer impedance reflection principle: the load impedance of the secondary side of the pulse transformer is reflected to the primary side through the square of the turns ratio, directly affecting the discharge rate of the primary-side energy storage capacitor C1. When the insulator under test is normal, its equivalent resistance is greater than 100MΩ, and the impedance reflected to the primary side is extremely high. The primary-side energy storage capacitor C1 discharges slowly only through capacitive displacement current, and the voltage drops slowly in an exponential manner. When the insulator is in a zero-value or low-resistance state, a large current is generated on the secondary side, which is reflected to the primary side to form a low-resistance load, and the voltage of the primary-side energy storage capacitor C1 drops rapidly. The primary-side breakdown detection unit collects the voltage across C1 in real time through a high-precision voltage sensor, and calculates the voltage drop rate through a differentiating circuit, which serves as the core basis for judging the insulator's condition. This detection method does not require the installation of any sensors on the 50kV high-voltage side. The detection circuit is entirely located on the low-voltage side (<400V), achieving electrical isolation from the high-voltage output side, which greatly improves the safety and reliability of the device.

[0056] The control and calculation unit is connected to the bipolar pulse excitation circuit and the primary-side breakdown detection unit, respectively, and is used to control the pre-excitation and main excitation timing, process voltage data, and determine the insulator status.

[0057] Specifically, the control and computing unit is the core control hub of the device, employing a high-speed microcontroller in conjunction with a high-speed ADC with a sampling rate ≥1MS / s to achieve fully automated control. Its operation process is as follows: first, it completes system initialization and battery power detection, then controls the main excitation power supply u... main The primary-side energy storage capacitor C1 is charged to a set voltage. Then, the second switch Q2 and the first switch Q1 are switched on and off sequentially according to a preset timing sequence to achieve accurate timing control of reverse pre-excitation and forward main excitation. At the same time, the voltage signal of the primary-side energy storage capacitor C1 is collected in real time, and high-frequency interference is eliminated by digital filtering algorithm. Finally, the insulator status is judged based on the comparison result of the voltage drop rate and the preset threshold. When it is initially judged to be abnormal, the low voltage secondary verification process is automatically triggered, and finally, a clear detection result of "normal", "low resistance (needs cleaning)" or "zero value (needs replacement)" is output.

[0058] In this embodiment, the primary-side energy storage capacitor C1 is an electrolytic capacitor or a film capacitor with low equivalent internal resistance; the reverse pre-excitation power supply is a low-voltage DC power supply; the main excitation power supply is a high-voltage DC power supply; the first diode D1 is connected in series in the main excitation circuit to block reverse current; the reverse pre-excitation circuit and the forward main excitation circuit are independent of each other and are controlled by corresponding switching transistors.

[0059] Specifically, the primary-side energy storage capacitor C1 is an electrolytic capacitor or film capacitor with low equivalent internal resistance. These capacitors have good high-frequency charging and discharging characteristics and pulse current tolerance, allowing for rapid energy release during the main excitation while reducing heat generation and energy loss, ensuring stable excitation pulse output and distortion-free waveform. The reverse pre-excitation power supply uses a low-voltage DC power supply, requiring only a small amount of energy to generate a reverse current pulse, causing the pulse transformer core to enter the negative saturation region early, providing maximum flux change space for subsequent main excitation. The main excitation power supply uses a high-voltage DC power supply to charge the primary-side energy storage capacitor C1 at high voltage, providing sufficient energy support for the pulse transformer to output a ≥50kV high-voltage impulse voltage. The first diode D1 is connected in series in the main excitation circuit, allowing only the forward excitation current to pass through, effectively blocking the induced current generated by the reverse recovery of the core, and preventing reverse voltage backflow from damaging the main excitation power supply and switching devices. The reverse pre-excitation circuit and the forward main excitation circuit operate independently and in a time-sharing manner. They are controlled by the second switch Q2 and the first switch Q1, respectively, to avoid mutual interference, cancellation or superposition of the currents in the two circuits. This ensures that the pre-magnetization timing and the main excitation timing are accurate and controllable and do not affect each other, significantly improving the circuit's operational stability, safety and detection reliability.

[0060] In this embodiment, the magnetic core of the pulse transformer is a ferrite core with a high remanence ratio; the number of turns on the primary side of the pulse transformer is less than the number of turns on the secondary side, and the voltage is boosted from low voltage pulse to high voltage impulse voltage through the turns ratio; the magnetic core is in the negative saturation region after reverse pre-excitation, and crosses from the negative saturation region to the positive saturation region during positive main excitation, thereby maximizing the utilization of magnetic flux.

[0061] Specifically, the pulse transformer uses a high remanence ratio ferrite core, with a remanence ratio of B. r / B s With a magnetic flux density >0.85, and preferably made of PC95 material, this core offers advantages over ordinary ferrite cores, including strong remanence retention, low high-frequency loss, and stable permeability. It is well-suited for bidirectional excitation by bipolar pulses, providing a reliable magnetic circuit foundation for bidirectional saturation magnetization. The pulse transformer employs a winding design with fewer turns on the primary side and more turns on the secondary side. The primary side turns are controlled at 10-25 turns, and the secondary side turns at 6000-10000 turns. Based on Faraday's law of electromagnetic induction, and through a reasonable matching of the primary and secondary turn ratios, the 100-300V low-voltage pulse output from the bipolar pulse excitation circuit is boosted to the ≥50kV high-voltage impulse voltage required for zero-value detection of insulators, accurately meeting the industry standard requirements for zero-value detection of disc-type suspension porcelain insulators. During operation, the core is first magnetized to the negative saturation region by a reverse pre-excitation pulse, stabilizing the core's operating point at a corresponding magnetic flux density of -B. max The state is as follows: After the pre-excitation is completed and the core state is stable, a positive main excitation pulse is applied, and the core operating point rapidly crosses from the negative saturation region to the positive saturation region, corresponding to a magnetic flux density of +B. max This makes the change in magnetic flux density of the magnetic core ΔB≈2B max This design enables full-range utilization of the magnetic core's hysteresis loop, maximizing magnetic flux utilization. Under the same high-voltage output requirements, it reduces the effective cross-sectional area of ​​the magnetic core to 40%~50% of traditional designs without pre-magnetization, significantly reducing the size and weight of the pulse transformer. This adapts to the practical needs of portable on-site testing in transmission lines, while simultaneously improving the energy conversion efficiency of the pulse transformer. It ensures stable high-voltage impulse voltage output and distortion-free waveform, providing reliable high-voltage excitation for accurate insulator condition detection.

[0062] In this embodiment, the primary-side breakdown detection unit includes a voltage acquisition module, a differential calculation module, and a threshold comparison module; the voltage acquisition module is used to acquire the voltage signal of the primary-side energy storage capacitor C1; the differential calculation module is used to calculate the voltage drop rate; the threshold comparison module is used to compare the rate with a preset threshold and output a judgment signal; the detection circuit of the primary-side breakdown detection unit is located on the low-voltage side and is electrically isolated from the high-voltage output side of the pulse transformer.

[0063] Specifically, the primary-side breakdown detection unit consists of a voltage acquisition module, a differential calculation module, and a threshold comparison module connected sequentially. These modules work together to acquire, process, and preliminarily determine fault characteristic signals. The voltage acquisition module uses a high-precision voltage sensor with a sampling rate ≥1MS / s, directly connected in parallel across the primary-side energy storage capacitor C1. It can capture rapid changes in the capacitor voltage in real time. Its detection circuit is entirely located on the low-voltage side, with an operating voltage not exceeding 400V, and maintains complete electrical isolation from the 50kV high-voltage output side of the pulse transformer. The differential calculation module receives the continuous voltage signal output from the voltage acquisition module and processes it using an analog differential circuit or a digital differential algorithm to calculate the voltage drop rate per unit time. This rate directly reflects the discharge speed of the primary-side energy storage capacitor C1. The threshold comparison module has pre-stored a first voltage drop rate threshold and a second voltage drop rate threshold. It compares the voltage drop rate output from the differential calculation module with the corresponding threshold and outputs a corresponding status judgment signal to the control and calculation unit.

[0064] The primary-side breakdown detection unit operates based on the transformer impedance reflection principle. The impedance value of the secondary load of the pulse transformer is reflected back to the primary side through the square of the turns ratio of the primary and secondary sides, directly changing the equivalent impedance of the primary circuit and thus affecting the discharge characteristics of the primary-side energy storage capacitor C1. When the insulator under test is normal, its equivalent resistance is greater than 100MΩ, and the impedance reflected to the primary side is extremely high. The primary-side energy storage capacitor C1 discharges slowly only through the capacitive displacement current generated by the leakage inductance and distributed capacitance of the transformer winding, and the voltage drops slowly exponentially. When the insulator is at zero resistance or in a low-resistance state, the secondary circuit conducts and generates a large current, which is reflected back to the primary side to form a low-resistance load. The primary-side energy storage capacitor C1 rapidly releases energy through this low-resistance circuit, and the voltage drops sharply. This detection method does not require the installation of any sensors or measuring equipment on the high-voltage side, fundamentally avoiding the safety risks of high-voltage measurement. At the same time, it greatly simplifies the device structure, reduces the impact of high-voltage side interference on the detection results, and improves the stability and reliability of the detection process.

[0065] In summary, the operating principle of this invention is as follows:

[0066] After device initialization, the control and calculation unit first completes system self-test and battery power detection. Then, it controls the main excitation power supply to charge the primary-side energy storage capacitor C1 with high voltage until it reaches the rated voltage of 100-300V, after which it enters standby mode. During detection startup, the control and calculation unit first outputs a signal to turn on the second switch Q2, injecting a reverse current pulse from the 5-24V reverse pre-excitation power supply into the primary side of the pulse transformer, thus enabling the remanence ratio B to operate. r / B s The operating point of the PC95 high remanence ferrite core with a remanence ratio >0.85 gradually shifts from the initial remanence point and stabilizes in the negative saturation region, corresponding to a magnetic flux density of -B.max This reserves the maximum magnetic flux variation space for subsequent positive excitation.

[0067] After pre-excitation, the control and calculation unit turns off the second switch Q2 and delays for 10~50μs to ensure the core state is stable before turning on the first switch Q1. The pre-charged primary-side energy storage capacitor C1 releases a large current pulse to the primary side of the pulse transformer through the main excitation circuit. At this time, the core operating point rapidly crosses from the negative saturation region to the positive saturation region, corresponding to a magnetic flux density of +B. max The change in magnetic flux density ΔB≈2B max This enables the full utilization of the magnetic core hysteresis loop. The pulse transformer matches the turns ratio of the 10-25 turns primary winding to the 6000-10000 turns secondary winding, boosting the low-voltage pulse on the primary side to a standard impulse voltage of ≥50kV and applying it to the insulator under test.

[0068] While the positive main excitation is applied, the primary-side breakdown detection unit acquires the voltage signal across the primary-side energy storage capacitor C1 in real time using a voltage sensor with a sampling rate ≥1MS / s. The voltage drop rate is then calculated by the differential operation module. Based on the transformer impedance reflection principle, the load impedance of the secondary side of the pulse transformer is reflected to the primary side through the square of the turns ratio, directly affecting the discharge rate of the primary-side energy storage capacitor C1: when the insulator under test is normal, its equivalent resistance is greater than 100MΩ, the impedance reflected to the primary side is extremely high, and the capacitor voltage drops slowly in an exponential manner; when the insulator is in a zero-value or low-resistance state, a large current is generated on the secondary side, which is reflected to the primary side to form a low-resistance load, and the capacitor voltage drops rapidly. The threshold comparison module compares the calculated voltage drop rate with the first voltage drop rate threshold. If the rate is not greater than the first threshold, the control and calculation unit determines that the insulator is normal and ends the detection; if the rate is greater than the first threshold, the insulator is determined to be abnormal and the low-voltage verification process is automatically triggered.

[0069] After entering the low-voltage verification process, the control and calculation unit first delays the process to allow the residual charge on the surface of the insulator under test to fully dissipate. Then, it controls the main excitation power supply to reduce its output voltage to 30%~50% of its rated value to perform low-voltage charging on the primary-side energy storage capacitor C1. After charging is complete, the above reverse pre-excitation, forward main excitation, and voltage drop rate calculation process is repeated to obtain the secondary voltage drop rate. The control and calculation unit compares the secondary voltage drop rate with a second voltage drop rate threshold. If the secondary rate is not greater than the second threshold, the insulator under test is determined to be in a low-resistance state; if the secondary rate is greater than the second threshold, the insulator under test is determined to be in a zero-value state, and the corresponding detection result is finally output.

[0070] Example 2

[0071] See Figure 2 and Figure 3Embodiment 2 of the present invention also provides a method for detecting zero-value insulators of pre-magnetized pulse transformer type, comprising:

[0072] S1. After the device initialization is completed, the control and calculation unit controls the main excitation power supply u. main Charge the primary-side energy storage capacitor C1 to prepare energy for high-voltage detection.

[0073] S2. Based on the charging completion signal of the primary-side energy storage capacitor C1, the control and calculation unit controls the second switch Q2 to turn on, and transmits the signal through the reverse pre-excitation power supply u. pre A reverse pre-excitation pulse is applied to the primary side of the pulse transformer, causing the core operating point of the pulse transformer to move to the negative saturation region;

[0074] S3. Based on the completion signal applied by the reverse pre-excitation pulse, the control and calculation unit turns off the second switch Q2 and delays it, while controlling the first switch Q1 to turn on, and through the main excitation power supply u main A positive main excitation pulse is applied to the primary side of the pulse transformer via the primary side energy storage capacitor C1; the pulse transformer boosts the low-voltage pulse into a high-voltage impulse voltage and applies it to the insulator under test;

[0075] S4. Based on the positive main excitation pulse applied signal, the primary side breakdown detection unit collects the voltage signal of the primary side energy storage capacitor C1 in real time and calculates the voltage drop rate within a set time.

[0076] S5. Compare the voltage drop rate with the first voltage drop rate threshold; if the voltage drop rate is not greater than the first voltage drop rate threshold, the insulator under test is determined to be normal and the test ends; if the voltage drop rate is greater than the first voltage drop rate threshold, the insulator under test is determined to be abnormal and the low voltage verification process is triggered.

[0077] S6. If the insulator under test is determined to be abnormal, the control and calculation unit delays and waits for the residual charge on the surface of the insulator under test to dissipate before controlling the main excitation power supply u. main Reduce the output voltage to perform low-voltage charging on the primary-side energy storage capacitor C1;

[0078] S7. After the primary-side energy storage capacitor C1 completes low-voltage charging, it repeatedly performs pre-excitation, main excitation and voltage drop rate calculation under low voltage to obtain the secondary voltage drop rate.

[0079] S8. Compare the secondary voltage drop rate with the second voltage drop rate threshold; if the secondary voltage drop rate is not greater than the second voltage drop rate threshold, the insulator under test is determined to be in a low resistance state; if the secondary voltage drop rate is greater than the second voltage drop rate threshold, the insulator under test is determined to be in a zero value state.

[0080] In this embodiment, in step S1, after the device initialization is completed, the control and calculation unit controls the main excitation power supply u. main The primary-side energy storage capacitor C1 is charged to prepare the energy for high-voltage detection.

[0081] Specifically, during the device initialization phase, the control and computing unit first executes the system self-test program, completing operations such as battery power detection, switch state reset, sampling channel calibration, and parameter loading to ensure that each module is in normal working condition. After the self-test passes, the control and computing unit outputs a control signal to start the main excitation power supply. The main excitation power supply is a 100~300V high-voltage DC power supply, which charges the primary-side energy storage capacitor C1 in a constant current charging mode. When the voltage across the capacitor reaches the preset rated value, the main excitation power supply automatically shuts off, completing the energy reserve for high-voltage detection. By adopting the energy storage capacitor charging and discharging working mode, a large current output can be provided instantaneously for the main excitation, meeting the energy requirements for generating high-voltage impulse voltage and avoiding the problem of insufficient output capacity caused by direct power supply.

[0082] In this embodiment, in step S2, based on the charging completion signal of the primary-side energy storage capacitor C1, the control and calculation unit controls the second switch Q2 to turn on, and through the reverse pre-excitation power supply u pre A reverse pre-excitation pulse is applied to the primary side of the pulse transformer, causing the core operating point of the pulse transformer to shift to the negative saturation region.

[0083] Specifically, such as Figure 4 As shown, after receiving the charging completion signal of the primary-side energy storage capacitor C1, the control and calculation unit immediately outputs a drive signal to turn on the second switch Q2, with the on-time controlled between 10 and 50 μs. The reverse pre-excitation power supply is a 5-24V low-voltage DC power supply, which injects a reverse current pulse into the primary side of the pulse transformer through the turned-on second switch Q2, thereby enabling the remanence ratio B to be used. r / B s The operating point of the PC95 high remanence ferrite core, with a remanence ratio >0.85, gradually shifts from the initial remanence point and stabilizes in the negative saturation region, corresponding to a magnetic flux density of -B. max This step requires only a small amount of energy to pre-magnetize the magnetic core, reserving the maximum flux change space for subsequent positive main excitation. It is a core prerequisite for realizing the utilization of the magnetic core's full hysteresis loop.

[0084] In this embodiment, in step S3, based on the application of the reverse pre-excitation pulse completion signal, the control and calculation unit turns off the second switch Q2 and delays it, while controlling the first switch Q1 to turn on, and through the main excitation power supply u main A positive main excitation pulse is applied to the primary side of the pulse transformer via the primary side energy storage capacitor C1; the pulse transformer boosts the low-voltage pulse into a high-voltage impulse voltage and applies it to the insulator under test.

[0085] Specifically, such as Figure 4 As shown, after the reverse pre-excitation pulse is applied, the control and calculation unit immediately turns off the second switch Q2 and delays for 10~50μs to ensure the core state is completely stable and to avoid residual reverse current interfering with the main excitation process. After the delay, the control and calculation unit outputs a drive signal to turn on the first switch Q1. The pre-charged primary-side energy storage capacitor C1 rapidly releases energy to the primary side of the pulse transformer through the main excitation circuit, generating a positive large current pulse. The pulse transformer adopts a winding design with 10~25 turns on the primary side and 6000~10000 turns on the secondary side. Based on Faraday's law of electromagnetic induction, it boosts the low-voltage pulse on the primary side to a standard impulse voltage of ≥50kV and applies it to both ends of the insulator under test through the high-voltage output terminal. At this time, the core operating point rapidly crosses from the negative saturation region to the positive saturation region, and the change in magnetic flux density ΔB≈2B max This significantly improves the energy conversion efficiency of the magnetic core.

[0086] The pulse transformer achieves the step-up conversion from low-voltage pulse to high-voltage impulse voltage through the primary-to-secondary turns ratio;

[0087] The primary-secondary turn ratio is:

[0088] n≥u outmax / (2πfΔBA e N1)

[0089] In the formula, n is the turns ratio of the primary and secondary sides; f is the equivalent pulse frequency; u outmax ΔB is the maximum impulse voltage that the secondary side of the pulse transformer needs to output; ΔB is the change in magnetic flux density of the magnetic core during the excitation process; A e N1 is the effective cross-sectional area of ​​the pulse transformer core; N2 is the number of turns of the primary winding of the pulse transformer.

[0090] In this embodiment, the reverse pre-excitation pulse and the positive main excitation pulse are time-independent and are controlled by the second switch Q2 and the first switch Q1 respectively. The volt-second product of the reverse pre-excitation and the positive main excitation satisfies the set ratio constraint, so that the magnetic core of the pulse transformer crosses from the negative saturation region to the positive saturation region.

[0091] The set ratio constraint is:

[0092] 0.3≤ (u pre ×t pre ) / (u main ×t main ≤0.8

[0093] In the formula, u pre ×t pre The volt-second product of the reverse pre-excitation; u main ×t main It is the volt-second product of the positive main excitation.

[0094] In this embodiment, in step S4, based on the positive main excitation pulse applied signal, the primary-side breakdown detection unit collects the voltage signal of the primary-side energy storage capacitor C1 in real time and calculates the voltage drop rate within a set time.

[0095] Specifically, such as Figure 5 As shown, the control and calculation unit outputs the turn-on signal of the first switch Q1 and simultaneously sends a data acquisition trigger signal to the primary-side breakdown detection unit. The primary-side breakdown detection unit uses a voltage sensor with a sampling rate ≥1 MS / s to acquire the continuous voltage signal across the primary-side energy storage capacitor C1 in real time, with the acquisition duration covering the complete discharge process of the main excitation pulse. After acquisition, the differential operation module processes the voltage signal and calculates the voltage drop rate within a set time window of 10~100 μs after the application of the main excitation pulse. This rate directly reflects the discharge speed of the primary-side energy storage capacitor C1 and is a core characteristic quantity for determining the insulation state of the insulator.

[0096] In this embodiment, in step S5, the voltage drop rate is compared with a first voltage drop rate threshold; if the voltage drop rate is not greater than the first voltage drop rate threshold, the insulator under test is determined to be normal and the test ends; if the voltage drop rate is greater than the first voltage drop rate threshold, the insulator under test is determined to be abnormal and a low voltage verification process is triggered.

[0097] Specifically, such as Figure 5 As shown, the threshold comparison module compares the calculated voltage drop rate with a pre-stored first voltage drop rate threshold, which is determined statistically through a large amount of field test data of normal disc suspension porcelain insulators. When the voltage drop rate is not greater than the first threshold, it indicates that the insulation performance of the insulator under test is good, and the control and calculation unit determines it to be in a normal state, and the current test process ends. When the voltage drop rate is greater than the first threshold, it indicates that the insulator under test has an insulation defect, which may be a zero-value fault or a low-resistance state caused by surface contamination. The control and calculation unit determines it to be in an abnormal state and automatically triggers the low-voltage verification process.

[0098] In this embodiment, in step S6, if the insulator under test is determined to be abnormal, the control and calculation unit delays and waits for the residual charge on the surface of the insulator under test to dissipate before controlling the main excitation power supply u. main The output voltage is reduced to perform low-voltage charging on the primary-side energy storage capacitor C1.

[0099] Specifically, after determining that the insulator under test is abnormal, the control and calculation unit first enters a delay waiting phase, with the delay time set to 1-5 seconds. This ensures that the residual charge generated on the surface of the insulator under test due to the high-voltage impact is fully dissipated, avoiding interference from the residual charge with the secondary detection results. After the delay, the control and calculation unit outputs a control signal to reduce the output voltage of the main excitation power supply to 30%-50% of its rated value, i.e., 30-150V. Subsequently, it performs low-voltage charging on the primary-side energy storage capacitor C1 using a constant current charging method. After charging is completed, the main excitation power supply is automatically turned off, preparing energy for the low-voltage verification process.

[0100] In this embodiment, in step S7, after the primary-side energy storage capacitor C1 completes low-voltage charging, it repeatedly performs pre-excitation, main excitation, and secondary calculation of voltage drop rate under low voltage to obtain the secondary voltage drop rate.

[0101] Specifically, after the primary-side energy storage capacitor C1 completes low-voltage charging, the control and calculation unit executes reverse pre-excitation, delay stabilization, and forward main excitation operations sequentially, following the same timing logic as high-voltage detection. During the reverse pre-excitation phase, energy is still provided by a 5-24V low-voltage DC power supply, causing the core operating point to shift back to the negative saturation region. During the forward main excitation phase, the low-voltage charged primary-side energy storage capacitor C1 releases energy to the primary side of the pulse transformer, which outputs a corresponding proportion of low-voltage impulse voltage and applies it to the insulator under test. Simultaneously, the primary-side breakdown detection unit repeatedly executes the voltage signal acquisition and processing flow to calculate the secondary voltage drop rate under low-voltage conditions.

[0102] In this embodiment, in step S8, the secondary voltage drop rate is compared with the second voltage drop rate threshold; if the secondary voltage drop rate is not greater than the second voltage drop rate threshold, the insulator under test is determined to be in a low resistance state; if the secondary voltage drop rate is greater than the second voltage drop rate threshold, the insulator under test is determined to be in a zero value state.

[0103] Specifically, such as Figure 5As shown, the control and calculation unit compares the secondary voltage drop rate with a pre-stored second voltage drop rate threshold. This threshold is specifically set for the insulator discharge characteristics under low-voltage conditions and is lower than the first voltage drop rate threshold. When the secondary voltage drop rate is not greater than the second threshold, it indicates that the insulation defect is caused by low resistance due to surface contamination of the insulator, and the insulation performance can be restored by cleaning. When the secondary voltage drop rate is greater than the second threshold, it indicates that the internal insulation structure of the insulator has completely failed, and it is judged to be in a zero-value state, requiring immediate replacement. This secondary verification mechanism can effectively distinguish between two different types of insulation defects, significantly reducing the detection misjudgment rate and providing a reliable decision-making basis for transmission line operation and maintenance.

[0104] In this embodiment, the device was adaptively optimized to meet the testing requirements in the -40℃ low-temperature environment of northern winters. Under low-temperature conditions, the saturation magnetic flux density B of the ferrite core... max The current will increase as the temperature decreases. If a pre-excitation pulse of fixed duration is used, it may lead to over-excitation, causing the magnetic core to enter the deep reverse saturation region, generating excessive reverse current and damaging the switching device.

[0105] This invention employs a pre-excitation current closed-loop control technology, in which a current sensor is connected in series in the reverse pre-excitation loop to detect the primary-side current waveform in real time. When the magnetic core has not reached saturation, the primary-side current increases linearly with time; when the magnetic core enters the saturation region, the primary-side current exhibits a clear inflection point and rises rapidly. The control unit monitors the current waveform in real time, and immediately stops pre-excitation when the saturation inflection point is detected, ensuring that the magnetic core operating point is always at -B. max This design ensures the flux change during the subsequent main excitation phase while avoiding device damage caused by excessive pre-excitation.

[0106] Verified by a -40℃ low-temperature environment simulation test, the output voltage fluctuation of the device under low-temperature environment does not exceed ±5%, and the operating temperature of the switching devices is stable within a safe range, which can meet the field testing requirements under extreme low-temperature environments.

[0107] In one possible embodiment, a portable insulator zero-value detection device and control process are provided as follows:

[0108] This embodiment provides a portable pre-magnetized pulse transformer type zero-value insulator detection device, with an overall weight of no more than 3kg. It can be operated by hand and is suitable for rapid on-site detection of transmission lines.

[0109] The pulse generation unit of the device consists of a reverse pre-excitation circuit and a main excitation circuit. The reverse pre-excitation circuit is powered by a 9V low-voltage battery pack and connected to the primary side of the pulse transformer via a 10Ω current-limiting resistor R1 and an IRF540 MOSFET Q1. It can apply a reverse current pulse with a duration of 20μs and a pulse current amplitude of approximately 0.5A, pre-magnetizing the pulse transformer core to the negative saturation region. The main excitation circuit uses a 20μF / 450V primary-side energy storage capacitor C1. After charging to its rated voltage of 300V, a positive main excitation pulse is applied 30μs after the pre-excitation ends via an IKW40N65H5 IGBT Q2.

[0110] The pulse transformer uses an EFD25 type PC95 ferrite core with an effective cross-sectional area A. e =52mm², primary winding turns N1=20 turns, secondary winding turns N2=6000 turns, turns ratio n=300. Due to the use of bidirectional pre-magnetization excitation technology, the core flux density change ΔB≈0.6T, which is twice that of the traditional unidirectional excitation method. Theoretically calculated, the peak output voltage of the device is: V o ᵤ t =n×ΔB×A e / Δt=300×0.6×52×10⁻ 6 / (5×10⁻ 6 The voltage is approximately 93kV, which fully meets the testing requirement of not less than 50kV in the DL / T2453-2021 standard. The energy of a single discharge is: E = ½C1V² = 0.5 × 20 × 10⁻⁻ 6 ×300²=0.9J Taking into account the transformer conversion efficiency and the contribution of pre-excitation energy, the total output energy of the device is ≥2J, which can reliably break down the internal air gap of the zero-value insulator.

[0111] The primary-side detection unit uses an INA128 differential amplifier to acquire the voltage signal across the primary-side energy storage capacitor C1, which is then converted from analog to digital by an ADS7822 12-bit ADC. The sampling interval is 10μs. The detection unit calculates the capacitor voltage drop ΔV 100μs after the application of the positive main excitation pulse. When the insulator under test is normal, its equivalent parallel resistance Rᵢ is... ns >100MΩ, the impedance reflected to the primary side is extremely high, the capacitor voltage drops slowly, ΔV<5V; when the insulator breaks down, its equivalent resistance Rᵢ ns When the impedance is less than 1kΩ, a short-circuit loop forms on the secondary side, reflecting back to the primary side as a low-impedance load, causing the capacitor voltage to drop rapidly, ΔV > 50V. This embodiment sets a voltage drop threshold K. th =30V / 100μs. When the detected ΔV>30V, the device determines it to be a zero-value insulator, the LCD display shows "zero value" and an audible and visual alarm is issued; otherwise, it displays "normal".

[0112] The device control process is as follows:

[0113] After the system is powered on, it first completes initialization and checks whether the battery level meets the detection requirements. When the battery level is sufficient, it controls the main excitation power supply to charge the primary-side energy storage capacitor C1 to a set voltage of 300V. After charging is complete, MOSFET Q1 is closed, and a 20μs reverse pre-excitation pulse is applied. A 30μs delay ensures that the core operating point is stable at -B. max Disconnect Q1, close IGBT Q2, and apply a positive main pulse; simultaneously start the ADC and continuously sample 100 voltage data points within 1ms; calculate the voltage drop rate dV / dt within a 100μs time window; output the detection result according to the DL / T2453-2021 standard judgment criteria; finally, release the residual charge in the circuit through the discharge resistor to prepare for the next detection.

[0114] In one possible embodiment, an example of testing an insulator with a strength rating of 210kN is provided as follows:

[0115] This embodiment tests a disc suspension porcelain insulator with a strength rating of 210kN. According to Table 1 of the DL / T2453-2021 standard, the zero value determination voltage for this grade of insulator is 50kV. A measured voltage <35kV is determined to be zero, and a measured voltage ≥35kV is determined to be normal.

[0116] To meet the testing requirements, this embodiment adjusts the charging voltage of the primary-side energy storage capacitor C1 to 220V, corresponding to a peak output voltage of 50kV on the secondary side of the pulse transformer. Field testing results show that when the insulator under test is in a normal state, the voltage of the primary-side energy storage capacitor slowly decreases from 220V to 215V, with a voltage drop of ΔV=5V within 100μs; when the insulator under test is in a zero-value state, the voltage of the primary-side energy storage capacitor rapidly decreases from 220V to 160V, with a voltage drop of ΔV=60V within 100μs.

[0117] This embodiment sets a software-determined threshold ΔV. th =30V. When the detected voltage drop is less than 30V, it is judged as a normal insulator; when it is greater than or equal to 30V, it is judged as a zero-value insulator. A field test of 100 insulators showed that the test results under this parameter configuration were completely consistent with the test results of the laboratory standard method, enabling reliable identification of 210kN level insulators.

[0118] In one possible embodiment, an example of testing for transmission lines in rainy seasons or polluted areas is provided as follows:

[0119] T1, Full Voltage Impulse Detection:

[0120] The control unit charges the primary-side energy storage capacitor C1 to 300V, corresponding to a 50kV standard impulse voltage output from the secondary side of the pulse transformer, and applies a high-voltage pulse according to the pre-magnetization process. If the ADC detects a voltage drop ΔV1 < 30V within 100μs, it indicates that the insulator has good insulation performance, and a "normal" test result is directly output; if ΔV1 ≥ 30V, it indicates that the insulator has an insulation defect, and the low-voltage verification test step is initiated.

[0121] T2, Low Voltage Verification Test:

[0122] The control unit automatically sets the charging voltage of the primary-side energy storage capacitor to 100V, corresponding to a 15kV impulse voltage output on the secondary side. This voltage is lower than the zero-value judgment threshold of 35kV specified in the DL / T2453-2021 standard. After waiting 80ms to ensure that the residual charge on the insulator surface has fully dissipated, the same pre-magnetization process is applied again, and the voltage drop ΔV2 within 100μs is detected and compared with the second judgment threshold K2=20V.

[0123] Scenario A: The first 50kV high-voltage impact on the zero-value insulator caused the internal air gap to break down, forming a conductive path. The second 15kV low-voltage impact was below the breakdown sustaining voltage, and the conductive path automatically extinguished, causing the insulator to return to a high-resistance state. At this time, the detected voltage drop ΔV2≈8V is less than the second threshold of 20V, and the system outputs a "zero-value" alarm, indicating "internal breakdown, replacement recommended".

[0124] Scenario B: Low-resistance insulator (damp / dirty surface). The first 50kV high-voltage surge creates leakage current on the insulator surface; the second 15kV low-voltage surge still exceeds the surface conductivity threshold. The surface resistance depends only on the degree of dirtiness and humidity, and does not change with the applied voltage; therefore, significant leakage current still exists. At this point, the detected voltage drop ΔV2≈25V, which is greater than or equal to the second threshold of 20V. The system outputs a "low resistance" warning, indicating "Surface dirty / damp, cleaning recommended."

[0125] Verified through on-site testing in heavily polluted areas, this secondary discrimination mechanism can reduce the false detection rate from over 20% with traditional methods to below 3%, significantly improving the reliability of the detection results.

[0126] The application scenarios of this invention are as follows:

[0127] In the daily operation and maintenance inspection of transmission lines, this invention relies on a pre-magnetized pulse transformer architecture to achieve a portable design, which can complete the screening of zero value and low resistance status of disc suspension porcelain insulators on site, and is suitable for rapid inspection of each pole in the field.

[0128] In heavily polluted areas and humid transmission line scenarios during the rainy season, this invention uses a discrimination logic that combines full-voltage impulse with low-voltage verification to distinguish between zero-value faults inside insulators and low-resistance phenomena caused by surface contamination and moisture, thereby reducing misjudgments during operation and maintenance.

[0129] In the cold and frigid field operation scenarios of northern regions, this invention is equipped with a closed-loop control mechanism for the pre-excitation current of the magnetic core, which can adapt to the fluctuation characteristics of the magnetic core parameters in a low temperature environment of -40℃ and stably complete the insulator testing work.

[0130] In specialized testing scenarios for high-strength insulators such as 210kN, this invention can flexibly adjust the primary-side charging voltage to match the standard voltage requirements, adapting to the withstand voltage determination and status identification needs of insulators of different specifications.

[0131] In the scenario of batch sampling inspection of insulators in substations, the present invention has a lightweight structure and simple operation process, which can meet the needs of continuous and rapid testing of multiple sets of insulators in the substation, and improve the efficiency of batch operation and maintenance.

[0132] In the scenario of troubleshooting and emergency repair of power transmission line faults, this invention does not require high-voltage external equipment. It can generate a qualified impulse voltage by relying on the built-in power supply, which can quickly locate the faulty insulator and support the timely restoration of the line.

[0133] The present invention has been described in a relatively specific and detailed manner above through general descriptions and specific embodiments. It should be understood that, based on the technical concept of the present invention, several conventional adjustments or further innovations can be made to these specific embodiments; however, as long as they do not depart from the technical concept of the present invention, the technical solutions obtained by these conventional adjustments or further innovations also fall within the protection scope of the claims of the present invention.

Claims

1. A pre-magnetized pulse transformer type zero-value insulator detection device, characterized in that, It includes a bipolar pulse excitation circuit, a pulse transformer, a primary-side breakdown detection unit, and a control and calculation unit; The bipolar pulse excitation circuit includes: a primary-side energy storage capacitor C1, a first switching transistor Q1, a second switching transistor Q2, a first diode D1, and a reverse pre-excitation power supply u. pre and main excitation power supply u main The reverse pre-excitation power supply u pre The second switch Q2 is connected to the primary side of the pulse transformer to apply a reverse pre-excitation pulse, shifting the core operating point to near the negative saturation region; the main excitation power supply u main The primary side of the pulse transformer is connected via the primary-side energy storage capacitor C1 and the first switching transistor Q1, and is used to apply a positive main excitation pulse after pre-excitation; The pulse transformer uses a high remanence ratio ferrite core; the primary side of the pulse transformer is connected to a bipolar pulse excitation circuit, and the secondary side is connected to the insulator under test; the pulse transformer is used to boost the low-voltage pulse on the primary side into a high-voltage impulse voltage. The primary-side breakdown detection unit is connected to the primary-side energy storage capacitor C1 and is used to collect the voltage of the primary-side energy storage capacitor C1 in real time and calculate the voltage drop rate. The control and calculation unit is connected to the bipolar pulse excitation circuit and the primary-side breakdown detection unit, respectively, and is used to control the pre-excitation and main excitation timing, process voltage data, and determine the insulator status.

2. The pre-magnetized pulse transformer type zero-value insulator detection device according to claim 1, characterized in that, The primary-side energy storage capacitor C1 is an electrolytic capacitor or a film capacitor with low equivalent internal resistance; the reverse pre-excitation power supply is a low-voltage DC power supply; the main excitation power supply is a high-voltage DC power supply; the first diode D1 is connected in series in the main excitation circuit to block reverse current; the reverse pre-excitation circuit and the forward main excitation circuit are independent of each other and are controlled by corresponding switching transistors.

3. The pre-magnetized pulse transformer type zero-value insulator detection device according to claim 2, characterized in that, The pulse transformer has a high remanence ratio ferrite core; the primary winding of the pulse transformer has fewer turns than the secondary winding, and the turns ratio is used to boost the voltage from low-voltage pulse to high-voltage impulse voltage; the core is in the negative saturation region after reverse pre-excitation, and crosses from the negative saturation region to the positive saturation region during positive main excitation, thereby maximizing the utilization of magnetic flux.

4. The pre-magnetized pulse transformer type zero-value insulator detection device according to claim 3, characterized in that, The primary-side breakdown detection unit includes a voltage acquisition module, a differential calculation module, and a threshold comparison module. The voltage acquisition module is used to acquire the voltage signal of the primary-side energy storage capacitor C1. The differential calculation module is used to calculate the voltage drop rate. The threshold comparison module is used to compare the rate with a preset threshold and output a judgment signal. The detection circuit of the primary-side breakdown detection unit is located on the low-voltage side and is electrically isolated from the high-voltage output side of the pulse transformer.

5. The pre-magnetized pulse transformer type zero-value insulator detection device according to claim 4, characterized in that, The control and calculation unit includes a timing control module, a digital filtering module, and a state discrimination module; the timing control module is used to control the sequence and interval of the reverse pre-excitation pulse and the forward main excitation pulse; the digital filtering module is used to filter out high-frequency interference in the voltage signal; The state discrimination module identifies the insulator's normal, low resistance, or zero-value state based on the voltage drop rate; when the control and calculation unit initially determines that the insulator is abnormal, it automatically triggers a low-voltage secondary excitation process to distinguish between the insulator's zero-value fault and its surface low resistance state.

6. A method for detecting zero-value insulators of pre-magnetized pulse transformer type, characterized in that, include: After the device initialization is complete, the control and calculation unit controls the main excitation power supply u. main Charge the primary-side energy storage capacitor C1 to prepare energy for high-voltage detection. Based on the charging completion signal of the primary-side energy storage capacitor C1, the control and calculation unit controls the second switch Q2 to turn on, and through the reverse pre-excitation power supply u pre A reverse pre-excitation pulse is applied to the primary side of the pulse transformer, causing the core operating point of the pulse transformer to move to the negative saturation region; Based on the completion signal of the reverse pre-excitation pulse, the control and calculation unit turns off the second switch Q2 and delays it, while controlling the first switch Q1 to turn on, and through the main excitation power supply u main A positive main excitation pulse is applied to the primary side of the pulse transformer via the primary side energy storage capacitor C1; The pulse transformer boosts the low-voltage pulse into a high-voltage impulse voltage and applies it to the insulator under test. Based on the positive main excitation pulse applied signal, the primary-side breakdown detection unit collects the voltage signal of the primary-side energy storage capacitor C1 in real time and calculates the voltage drop rate within a set time. The voltage drop rate is compared with a first voltage drop rate threshold; If the voltage drop rate is not greater than the first voltage drop rate threshold, the insulator under test is determined to be normal and the test ends. If the voltage drop rate is greater than the first voltage drop rate threshold, the insulator under test is determined to be abnormal and the low voltage verification process is triggered. If the insulator under test is determined to be abnormal, the control and calculation unit delays and waits for the residual charge on the surface of the insulator under test to dissipate before controlling the main excitation power supply u. main Reduce the output voltage to perform low-voltage charging on the primary-side energy storage capacitor C1; After the primary-side energy storage capacitor C1 completes low-voltage charging, it repeatedly performs pre-excitation, main excitation and voltage drop rate calculation under low voltage to obtain the secondary voltage drop rate. The secondary voltage drop rate is compared with the second voltage drop rate threshold; if the secondary voltage drop rate is not greater than the second voltage drop rate threshold, the insulator under test is determined to be in a low resistance state. If the secondary voltage drop rate is greater than the second voltage drop rate threshold, the insulator under test is determined to be in a zero-value state.

7. The method for detecting a pre-magnetized pulse transformer type zero-value insulator according to claim 6, characterized in that, The reverse pre-excitation pulse and the positive main excitation pulse are time-independent and are controlled by the second switch Q2 and the first switch Q1 respectively. The volt-second product of the reverse pre-excitation and the positive main excitation satisfies the set ratio constraint, so that the magnetic core of the pulse transformer crosses from the negative saturation region to the positive saturation region. The set ratio constraint is: 0.3≤ (in pre ×t pre ) / (in main ×t main ) ≤0.8 In the formula, u pre ×t pre The volt-second product of the reverse pre-excitation; u main ×t main It is the volt-second product of the positive main excitation.

8. The method for detecting a pre-magnetized pulse transformer type zero-value insulator according to claim 7, characterized in that, When the primary-side breakdown detection unit acquires the voltage signal of the primary-side energy storage capacitor C1, the voltage signal is digitally filtered to remove high-frequency interference. The voltage signal acquisition and processing of the primary-side breakdown detection unit are both completed on the low-voltage side, maintaining electrical isolation from the high-voltage output side of the pulse transformer.

9. The method for detecting a pre-magnetized pulse transformer type zero-value insulator according to claim 8, characterized in that, In the low-voltage verification process, the delay time of the control and calculation unit meets the requirement of dissipating residual charge on the surface of the insulator under test; the low-voltage charging voltage of the primary side energy storage capacitor C1 is a preset ratio of the high-voltage charging voltage, and the output low-voltage impulse voltage is adapted to the verification requirements.

10. The method for detecting a pre-magnetized pulse transformer type zero-value insulator according to claim 9, characterized in that, The pulse transformer uses a high remanence ratio ferrite core and achieves the step-up conversion from low-voltage pulse to high-voltage impulse voltage through the primary and secondary turns ratio; The primary-secondary turn ratio is: n≥u outmax / (2πfΔBA e N1) In the formula, n is the turns ratio of the primary and secondary sides; f is the equivalent pulse frequency; u outmax ΔB is the maximum impulse voltage that the secondary side of the pulse transformer needs to output; ΔB is the change in magnetic flux density of the magnetic core during the excitation process; A e N1 is the effective cross-sectional area of ​​the pulse transformer core; N2 is the number of turns of the primary winding of the pulse transformer.

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