A pulse injection device and method for online calibration of partial discharge quantities

Abstract

The application relates to a pulse injection device and method for local discharge amount online calibration, wherein the device comprises a signal generation branch, a protection branch, a high-voltage coupling capacitor and a voltage limiting protection impedance arranged in a switch cabinet; one end of the voltage limiting protection impedance is grounded, the other end is connected with one end of the high-voltage coupling capacitor, the other end of the high-voltage coupling capacitor is connected with a high-voltage loop inside the switch cabinet; a connection point of the voltage limiting protection impedance and the high-voltage coupling capacitor is used as a calibration pulse injection point, the calibration pulse injection point is connected with the signal generation branch and the protection branch through a voltage division capacitor respectively; the signal generation branch is used for injecting a square wave pulse signal to the calibration pulse injection point; and the protection branch is used for ensuring voltage stability of the high-voltage loop inside the switch cabinet when the signal generation branch is put into use or disconnected.

Description

Technical Field

[0001] This invention relates to a pulse injection device and method for online calibration of partial discharge quantity, belonging to the field of partial discharge quantity calibration technology. Background Technology

[0002] High-voltage switchgear plays a crucial role in the normal operation of my country's power system. All equipment in the power system operates stably under the real-time regulation of the switchgear, and it is widely used in substations as an important component of the power system. Its main function is to control the opening and closing of power system circuits. When a fault occurs in some equipment of the power system, the switchgear disconnects the faulty circuit through its control device, thereby ensuring the safety of electrical equipment. Therefore, it is evident that switchgear plays a vital role in the safe and reliable operation of the power system.

[0003] In recent years, with the rapid development of the national economy and the continuous improvement of people's living standards, the demand for electricity has been increasing, and voltage levels have been gradually rising, placing higher demands on the stability and reliability of the power system. Strengthening research on online monitoring, fault diagnosis, and condition assessment technologies for power transmission and transformation equipment is of great significance for improving equipment utilization and operational reliability, and ensuring the safe and economical operation of the power grid. The transition from planned maintenance to condition-based maintenance in power system operation and maintenance has become an inevitable trend. Partial discharge is a major cause of insulation degradation and also an important sign and manifestation of insulation degradation.

[0004] High-frequency pulsed current partial discharge detection, as an important means of detecting the health status of electrical equipment, plays a crucial role in switchgear fault detection. The pulsed current method refers to the phenomenon where partial discharge occurs within the switchgear, generating a certain amount of charge and creating an apparent discharge charge across the sample. This apparent discharge charge forms a pulsed current through the partial discharge test circuit. A pulsed voltage signal can be acquired by using a matched detection impedance. Under fixed test circuit parameters, the magnitude of the pulsed voltage signal is proportional to the apparent discharge charge of the sample. The pulsed current method has advantages such as high sensitivity, accuracy, transmission stability, and resistance to spatial interference, and is currently the most widely used method in power systems. With the gradual promotion of live-line testing of switchgear, the performance of the high-frequency pulsed current partial discharge detection method is increasingly attracting the attention of engineers. Partial discharge calibration is one of the key factors restricting the accuracy of test results.

[0005] Calibration of apparent discharge is a prerequisite for online monitoring of partial discharge in transformers using the pulse current method. Currently, there are two main methods for calibrating online partial discharge monitoring systems for transformers: offline calibration and online calibration.

[0006] Traditional methods for calibrating partial discharge calibrators employ the discrete component method, which involves separately measuring the square wave voltage and injection capacitance within the calibrator and multiplying them as the calibration result. This discrete component calibration method has the following problems: First, to measure the step voltage and capacitance, the casing of the calibrator under test must be opened to locate the step voltage output terminal and capacitance terminal. If the instrument cannot be opened, it is difficult to measure using the discrete component method. Even if the instrument is opened, it is sometimes difficult to determine the corresponding measurement terminals. Second, the capacitance is usually a small capacitor in the picofarad range, and most do not have shielding electrodes, making them susceptible to stray parameters and unable to accurately measure the equivalent capacitance of the circuit, resulting in significant measurement uncertainty.

[0007] Traditional methods require the transformer under test to be de-energized and to maintain the same wiring configuration as in operation, making it impossible to frequently calibrate the monitoring system. Therefore, researchers have proposed the following online calibration methods.

[0008] 1. Impedance method: The impedance method refers to inserting a small impedance in series with the grounding wire of the equipment under test, and connecting a fast changeover switch in parallel across the two ends. The switch operates at a frequency of 50Hz, which generates a pulse voltage across the resistor R (Cx is the equivalent capacitance of the equipment under test, Ck is the equivalent capacitance of the line and equipment connected to the equipment, and Zd is the detection element). By controlling the switch K, the pulse voltage across the resistor R can be made to meet the IEC requirements for the correction voltage waveform.

[0009] 2. Coupling Method: The correction voltage signal is coupled to the ground wire of the device under test through the Rogowski coil. According to the law of electromagnetic induction, an induced voltage Δu will be generated on the ground wire. This voltage and the equivalent capacitance Cx of the device can form a correction charge, which is equivalent to injecting a correction charge of Cx*Δu from the two ends of the device.

[0010] The experimental results show that although the correction results of the impedance method and the coupling method are basically consistent with the square wave correction results recommended by IEC, the operation of the above two methods is very complicated and difficult to implement, and neither is ideal. Summary of the Invention

[0011] To address the problems existing in the prior art, this invention proposes a pulse injection device and method for online calibration of partial discharge quantity.

[0012] The technical solution of the present invention is as follows:

[0013] On one hand, the present invention provides a pulse injection device for online calibration of partial discharge quantity, comprising:

[0014] Signal generation branch, protection branch, and high-voltage coupling capacitors and voltage limiting protection impedances installed in the switch cabinet;

[0015] One end of the voltage limiting protection impedance is grounded, and the other end is connected to one end of the high-voltage coupling capacitor. The other end of the high-voltage coupling capacitor is connected to the high-voltage circuit inside the switch cabinet.

[0016] The connection point of the voltage limiting protection impedance and the high voltage coupling capacitor is used as the calibration pulse injection point. The calibration pulse injection point is connected to the signal generation branch and the protection branch respectively through a voltage divider capacitor.

[0017] The signal generation branch is used to inject a square wave pulse signal into the calibration pulse injection point;

[0018] The protection branch is used to ensure the voltage stability of the high-voltage circuit inside the switch cabinet when the signal generation branch is put into use or disconnected.

[0019] In a preferred embodiment, the signal generation branch specifically includes:

[0020] Equivalent ideal voltage source, signal generator internal resistance, and signal generation branch switch;

[0021] One end of the equivalent ideal voltage source is grounded, and the other end is connected to one end of the internal resistance of the signal generator. The other end of the internal resistance of the signal generator is connected to one end of the signal generation branch switch, and the other end of the signal generation branch switch is connected to the voltage divider capacitor.

[0022] In a preferred embodiment, the protection branch specifically includes:

[0023] Protect the branch circuit resistor and protect the branch circuit switch;

[0024] One end of the protection branch resistor is grounded, and the other end is connected to one end of the protection branch switch. The other end of the protection branch switch is connected to the voltage divider capacitor.

[0025] On the other hand, the present invention also provides a pulse injection method for online calibration of partial discharge quantity, implemented based on the pulse injection device for online calibration of partial discharge quantity described in any embodiment of the present invention, the method comprising the following steps:

[0026] In the power outage state, the signal generation branch and the protection branch are connected at the calibration pulse injection point. When connected, the protection branch switch is in the closed state and the signal generation branch switch is in the open state.

[0027] Determine whether the voltage of the high-voltage circuit inside the switchgear is stable. Once stable, activate the signal generation branch, close the signal generation branch switch, and disconnect the protection branch switch.

[0028] Begin the apparent discharge calibration, adjust the amplitude of the equivalent ideal voltage source, and calculate the calibration scale;

[0029] After completing the calibration calculation, determine whether the voltage of the high-voltage circuit inside the switchgear is stable. Once stable, close the protection branch switch first, then open the signal generation branch switch, and remove the signal generation branch and protection branch from the calibration pulse injection point.

[0030] In a preferred embodiment, the method for determining whether the voltage of the high-voltage circuit inside the switchgear is stable is specifically as follows:

[0031] Monitor whether the voltage at the connection point between the protection branch and the voltage divider capacitor is stable. When the voltage at the connection point between the protection branch and the voltage divider capacitor is stable, it is determined that the voltage of the high-voltage circuit inside the switchgear is stable.

[0032] The present invention has the following beneficial effects:

[0033] This invention discloses a pulse injection device and method for online calibration of partial discharge quantity. By protecting the high-voltage circuit, the stability of the voltage is ensured, thereby ensuring that the signal generation branch is not affected by voltage oscillation when connected. This ensures the safety of the pulse source while not affecting the safe operation of the switchgear equipment. On this basis, online quantitative calibration of the partial discharge quantity of the switchgear is achieved. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the circuit principle of the device according to Embodiment 1 of the present invention;

[0035] Figure 2 This is an example waveform diagram of the injected pulse signal in an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the method flow of Embodiment 2 of the present invention.

[0037] The attached figures are labeled as follows:

[0038] 1. Switchgear equipment capacitors; 2. Line distributed capacitance; 3. High-voltage coupling capacitors; 4. Voltage divider capacitors; 5. Voltage limiting protection impedance; 6. Protection branch; 7. Protection branch switch; 8. Protection branch resistor; 9. Signal generation branch; 10. Signal generation branch switch; 11. Signal generator internal resistance; 12. Equivalent ideal voltage source. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0040] It should be understood that the step numbers used in the text are for ease of description only and are not intended to limit the order in which the steps are performed.

[0041] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0042] The terms “comprising” and “including” indicate the presence of the described feature, whole, step, operation, element and / or component, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0043] The term “and / or” refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes these combinations.

[0044] Example 1:

[0045] See Figure 1 This embodiment provides a pulse injection device for online calibration of partial discharge quantity, comprising:

[0046] like Figure 1 As shown, the pulse injection device for online calibration of partial discharge quantity specifically includes a high-voltage coupling capacitor 3, a voltage limiting protection impedance 5, a protection branch 6, and a signal generation branch 9; wherein, the protection branch 6 and the signal generation branch 9 are located outside the switch cabinet, the high-voltage coupling capacitor 3 and the voltage limiting protection impedance 5 are located inside the switch cabinet, and the signal generation branch 9 includes a signal generator.

[0047] One end of the voltage limiting protection impedance 5 is grounded, and the other end is connected to one end of the high-voltage coupling capacitor 3. The other end of the high-voltage coupling capacitor 3 is connected to the high-voltage circuit inside the switch cabinet. The high-voltage circuit inside the switch cabinet includes the switch cabinet equipment capacitor 1 and the line distribution capacitor 2.

[0048] The connection point between the voltage-limiting protection impedance 5 and the high-voltage coupling capacitor 3 is used as the calibration pulse injection point, i.e. Figure 1 The node containing point a, the calibrated pulse injection point, is connected to the signal generation branch 9 and the protection branch 6 respectively through a voltage divider capacitor 4; the voltage divider capacitor 4 and the high-voltage coupling capacitor 3 together constitute the calibrating capacitor in the pulse signal injection circuit. After the high-voltage signal in the switchgear high-voltage circuit is divided by the high-voltage coupling capacitor 3 and the voltage divider capacitor 4, the high-voltage signal in the switchgear high-voltage circuit can be divided to a voltage range suitable for the operating voltage of the signal generator in the signal generation branch 9. The voltage division ratio depends on the capacitance values ​​of these two capacitors.

[0049] The signal generation branch 9 is used to inject a square wave pulse signal into the calibration pulse injection point;

[0050] The protection branch 6 is used to ensure the voltage stability of the high-voltage circuit inside the switch cabinet when the signal generation branch is put into use or disconnected.

[0051] When an external branch suddenly connects to or disconnects from the high-voltage circuit of the switchgear, voltage oscillations are inevitable at the connection point. Directly connecting or disconnecting the signal generation branch 9 could affect its normal service life due to these voltage oscillations. Therefore, this embodiment includes a protection branch 6. Before connecting the signal generation branch 9, the protection branch 6 is connected to monitor the stability of the voltage in the high-voltage circuit inside the switchgear. If the voltage signal is stable, it indicates that the protection branch 6 has functioned, and the signal generation branch 9 can continue to be connected to the high-voltage circuit of the switchgear. Since the signal generation branch 9 is already safely and reliably connected to the high-voltage circuit, the protection branch 6 is no longer needed. Similarly, before disconnecting the signal generation branch 9, the voltage is stabilized by connecting the protection branch, allowing the signal generation branch 9 to be safely and reliably disconnected from the high-voltage circuit of the switchgear. Through this process, connecting the protection branch 6 to the high-voltage circuit of the switchgear before connecting or disconnecting the signal generation branch 9 reduces the impact of voltage oscillations on the signal generation branch 9 and ensures its normal operating life.

[0052] In one embodiment, the signal generation branch 9 specifically includes:

[0053] The equivalent ideal voltage source 12 of the signal generator, the internal resistance 11 of the signal generator, and the signal generation branch switch 10;

[0054] One end of the equivalent ideal voltage source 12 is grounded, and the other end is connected to one end of the internal resistance 11 of the signal generator. The other end of the internal resistance 11 of the signal generator is connected to one end of the signal generation branch switch 10, and the other end of the signal generation branch switch 10 is connected to the voltage divider capacitor 4.

[0055] The signal generator injects a square wave signal into the calibration pulse injection point a, and its waveform is as follows: Figure 2 As shown.

[0056] The pulse signal emitted by the signal generator first passes through the internal resistor 11 of the signal generator, which limits the current and ensures that the output voltage of the signal generator remains stable. Next, it passes through the voltage divider capacitor 4 and the high-voltage coupling capacitor 3 before being injected into the switchgear busbar. The amount of charge injected by the signal generator at the calibration point can be calculated using the following formula:

[0057]

[0058] Among them, C d C is the value of the high-voltage coupling capacitor. i U0 is the voltage divider capacitor value, and U0 is the pulse signal amplitude.

[0059] In one embodiment, the aforementioned protection branch 6 specifically includes:

[0060] Protective branch resistor 8 and protective branch switch 7;

[0061] One end of the protection branch resistor 7 is grounded, and the other end is connected to one end of the protection branch switch 8. The other end of the protection branch switch 8 is connected to the voltage divider capacitor 4.

[0062] Example 2:

[0063] This embodiment provides a pulse injection method for online calibration of partial discharge quantity, which is implemented based on the pulse injection device for online calibration of partial discharge quantity described in Embodiment 1 above. See details below. Figure 3 The online calibration pulse injection method specifically includes the following steps:

[0064] S100. Complete the circuit connection, specifically including: in the power outage state, set up a calibration pulse access node in the switch cabinet, connect the signal generation branch and the protection branch at the calibration pulse injection point, and when connected, the protection branch switch is in the closed state and the signal generation branch switch is in the open state.

[0065] S200, Activate the signal generation branch, specifically including: determining whether the voltage of the high-voltage circuit inside the switchgear is stable, activating the signal generation branch after it is stable, closing the signal generation branch switch, and disconnecting the protection branch switch.

[0066] S300, Start the apparent discharge quantity calibration, adjust the amplitude of the equivalent ideal voltage source of the signal generator, and calculate the calibration scale;

[0067] S400. After completing the calibration scale calculation, determine whether the voltage of the high-voltage circuit inside the switchgear is stable. After it is stable, first close the protection branch switch, then open the signal generation branch switch, and remove the signal generation branch and protection branch from the calibration pulse injection point.

[0068] Based on this embodiment, a pulse signal is injected into the high-voltage circuit inside the switchgear through a high-voltage capacitor at the calibration pulse injection point. The response reading of the measuring device is then read to obtain the graduation coefficient, thereby achieving online calibration of the equipment's partial discharge. The signal generation branch can be safely and reliably connected to the high-voltage circuit via a protection branch.

[0069] In one embodiment, the method for determining whether the voltage of the high-voltage circuit inside the switchgear is stable in steps S200 and S400 is as follows:

[0070] Use appropriate measuring equipment or sensors to monitor the connection points between the protection branch and the voltage divider capacitor. Figure 1 Whether the voltage at point b is stable, when the voltage at the connection node between the protection branch and the voltage divider capacitor is stable, it is determined that the voltage of the high-voltage circuit inside the switchgear is stable.

[0071] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, A and B simultaneously, or B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, at least one of a, b, and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0072] Those skilled in the art will recognize that the units and algorithm steps described in the embodiments disclosed herein can be implemented using electronic hardware, computer software, or a combination of electronic hardware and software. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0073] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0074] In the several embodiments provided in this application, any function, if implemented as a software functional unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0075] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A pulse injection device for online calibration of partial discharge quantity, characterized in that, include: Signal generation branch, protection branch, and high-voltage coupling capacitors and voltage limiting protection impedances installed in the switch cabinet; One end of the voltage limiting protection impedance is grounded, and the other end is connected to one end of the high-voltage coupling capacitor. The other end of the high-voltage coupling capacitor is connected to the high-voltage circuit inside the switch cabinet. The connection point of the voltage limiting protection impedance and the high voltage coupling capacitor is used as the calibration pulse injection point. The calibration pulse injection point is connected to the signal generation branch and the protection branch respectively through a voltage divider capacitor. The signal generation branch is used to inject a square wave pulse signal into the calibration pulse injection point; The protection branch is used to ensure the voltage stability of the high-voltage circuit inside the switch cabinet when the signal generation branch is put into use or disconnected. The signal generation branch specifically includes: Equivalent ideal voltage source, signal generator internal resistance, and signal generation branch switch; One end of the equivalent ideal voltage source is grounded, and the other end is connected to one end of the internal resistance of the signal generator. The other end of the internal resistance of the signal generator is connected to one end of the signal generation branch switch, and the other end of the signal generation branch switch is connected to the voltage divider capacitor.

2. The pulse injection device for online calibration of partial discharge quantity according to claim 1, characterized in that, The protection branch specifically includes: Protect the branch circuit resistor and protect the branch circuit switch; One end of the protection branch resistor is grounded, and the other end is connected to one end of the protection branch switch. The other end of the protection branch switch is connected to the voltage divider capacitor.

3. A pulse injection method for online calibration of partial discharge quantity, implemented based on the pulse injection device for online calibration of partial discharge quantity as described in any one of claims 1-2, characterized in that, The method includes the following steps: In the power outage state, the signal generation branch and the protection branch are connected at the calibration pulse injection point. When connected, the protection branch switch is in the closed state and the signal generation branch switch is in the open state. Determine whether the voltage of the high-voltage circuit inside the switchgear is stable. Once stable, activate the signal generation branch, close the signal generation branch switch, and disconnect the protection branch switch. Begin the apparent discharge calibration, adjust the amplitude of the equivalent ideal voltage source, and calculate the calibration scale; After completing the calibration calculation, determine whether the voltage of the high-voltage circuit inside the switchgear is stable. Once stable, close the protection branch switch first, then open the signal generation branch switch, and remove the signal generation branch and protection branch from the calibration pulse injection point.

4. The pulse injection method for online calibration of partial discharge quantity according to claim 3, characterized in that, The specific steps for determining whether the voltage in the high-voltage circuit inside the switchgear is stable are as follows: Monitor whether the voltage at the connection point between the protection branch and the voltage divider capacitor is stable. When the voltage at the connection point between the protection branch and the voltage divider capacitor is stable, it is determined that the voltage of the high-voltage circuit inside the switchgear is stable.

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