External synchronizing signal conditioning circuit for partial discharge detection and partial discharge monitoring device

Abstract

The invention relates to an external synchronizing signal conditioning circuit for partial discharge detection and a partial discharge monitoring device, and belongs to the field of live detection and online monitoring of power equipment. According to the invention, firstly, the transformer is used for converting the power frequency voltage into the low voltage which can be detected by the chip, then the comparator is used for converting the sine wave of the low voltage into the square wave, and the Schmidt inverter is used for shaping the square wave, so that the acquisition module of the partial discharge monitoring device can be effectively triggered; therefore, phase angle information of the power frequency power supply is provided for the partial discharge monitoring device. The external synchronizing signal conditioning circuit for partial discharge detection can be integrated on a circuit board in a partial discharge monitoring device, miniaturization of the partial discharge monitoring device is achieved, accurate drawing of a PRPD atlas and a PRPS atlas of partial discharge signals and accurate detection of the partial discharge signals can be achieved, and field installation and construction are facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of live detection and online monitoring of electric power equipment, and in particular to an external synchronous signal conditioning circuit for partial discharge detection and a partial discharge monitoring device. Background Art

[0002] The discharge of the insulation of power equipment in a local area under the action of a sufficiently strong electric field is called partial discharge (or PD for short). Partial discharge will eventually cause insulation breakdown of the electrical equipment, have a direct impact on the operation of the electrical equipment, and seriously threaten the life safety of related personnel. Therefore, partial discharge detection is very important for the insulation evaluation of electrical equipment and the safe operation of the power system.

[0003] The PRPD (Phase Resolved Partial Discharge) and PRPS (Phase Resolved Pulse Sequence) of partial discharge are used for partial discharge detection and are important tools for analyzing and diagnosing the insulation status of electrical equipment. The PRPD spectrum is a graph that corresponds the amplitude of the partial discharge signal to the phase angle of the power frequency voltage, and displays the discharge activity in a complete voltage cycle from 0° to 360°; the PRPS spectrum is a three-dimensional spectrum that plots the pulse signal according to the three dimensions of power frequency phase-amplitude-power frequency cycle. Both spectra require accurate acquisition of the correspondence between the partial discharge signal and the power frequency phase angle.

[0004] There are two main types of analytical and diagnostic equipment used to detect partial discharges in the industry, including handheld instruments and online monitoring devices: ① Most handheld instruments simulate power frequency signals through software. Although they are easy to carry, the simulated power frequency signals are not accurate enough, which will cause a large phase deviation of the partial discharge signal and cannot be used in scenarios that require high precision. ② The online monitoring device can generate high-precision PRPD and PRPS spectra of partial discharge signals, but it needs to be equipped with an external power frequency signal synchronization device or module, which is large in size and is not conducive to the matching of electrical parameters and on-site installation and construction. Summary of the invention

[0005] The purpose of the present invention is to provide an external synchronous signal conditioning circuit for partial discharge detection to solve the problem that the external power frequency signal synchronization device used in the existing partial discharge online monitoring solution is large in size, which is not conducive to the matching of electrical parameters and on-site installation and construction; and also provide a partial discharge monitoring device to solve the problem that the existing solution for analyzing and diagnosing partial discharge of electrical equipment cannot take into account both detection accuracy and convenience for on-site installation and construction.

[0006] To achieve the above object, the solution of the present invention includes: The technical solution of an external synchronous signal conditioning circuit for partial discharge detection of the present invention comprises a voltage conversion module whose input end is used to connect to the power frequency power supply corresponding to the high-voltage equipment to be tested, a waveform conversion module used to convert the sine wave of the power frequency power supply into a square wave, and a waveform shaping module used to shape the square wave to obtain steeper rising and falling edges; the voltage conversion module is used to convert the voltage of the power frequency power supply into the working voltage of the waveform conversion module, the output end of the voltage conversion module is connected to the input end of the waveform conversion module, and the output end of the waveform conversion module is connected to the input end of the waveform shaping module; the output end of the waveform shaping module is used to provide a square wave signal capable of obtaining power frequency phase angle information for partial discharge detection.

[0007] Furthermore, the voltage conversion module includes a transformer, the contact point of the primary winding of the transformer serves as the input end of the voltage conversion module, and the contact point of the secondary winding of the transformer serves as the output end of the voltage conversion module.

[0008] Furthermore, the transformer is a variable ratio transformer.

[0009] Furthermore, the waveform conversion module includes a comparator; the non-phase input end of the comparator is connected to one end of the secondary winding of the transformer, and the other end of the secondary winding of the transformer is grounded; the inverting input end of the comparator is grounded through a voltage divider resistor, and the comparator and the resistor constitute a zero-crossing detection circuit; the output end of the comparator serves as the output end of the waveform conversion module.

[0010] Furthermore, the waveform shaping module includes a Schmitt inverter; the input end of the Schmitt inverter serves as the input end of the waveform shaping module, and the output end of the Schmitt inverter serves as the output end of the waveform shaping module.

[0011] A technical solution of a partial discharge monitoring device of the present invention comprises an external synchronous signal conditioning circuit; the external synchronous signal conditioning circuit comprises a voltage conversion module whose input end is used to connect to an industrial frequency power supply corresponding to a high-voltage device to be tested, a waveform conversion module used to convert the waveform of the industrial frequency power supply into a square wave, and a waveform shaping module used to shape the square wave to obtain a steeper rising edge and falling edge; the voltage conversion module is used to convert the voltage of the industrial frequency power supply into an operating voltage of the waveform conversion module, the output end of the voltage conversion module is connected to the input end of the waveform conversion module, and the output end of the waveform conversion module is connected to the input end of the waveform shaping module; the output end of the waveform shaping module is used to provide a square wave signal capable of obtaining industrial frequency phase angle information for partial discharge detection.

[0012] Furthermore, the voltage conversion module includes a transformer, the contact of the primary winding of the transformer serves as the input end of the voltage conversion module, and the contact of the secondary winding of the transformer serves as the output end of the voltage conversion module; a contact in the secondary winding of the transformer is grounded.

[0013] Furthermore, the transformer is a variable ratio transformer.

[0014] Furthermore, the waveform conversion module includes a comparator; the non-phase input end of the comparator is connected to one end of the secondary winding of the transformer, the inverting input end of the comparator is grounded through a voltage divider resistor, and the comparator and the resistor constitute a zero-crossing detection circuit; the output end of the comparator serves as the output end of the waveform conversion module.

[0015] Furthermore, the waveform shaping module in the partial discharge monitoring device includes a Schmidt inverter; the input end of the Schmidt inverter serves as the input end of the waveform shaping module, and the output end of the Schmidt inverter serves as the output end of the waveform shaping module.

[0016] The present invention miniaturizes the external synchronous signal conditioning circuit for partial discharge detection so that it can be integrated into the circuit board in the partial discharge monitoring device, so that the partial discharge monitoring device does not need an additional signal synchronization device or module. It can improve the accuracy of the partial discharge signal PRPD spectrum and PRPS spectrum and facilitate on-site installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A module diagram of an external synchronous signal conditioning circuit for partial discharge detection according to the present invention; Figure 2 A circuit schematic diagram of an external synchronous signal conditioning circuit for partial discharge detection according to the present invention; Figure 3 This is a waveform conversion diagram of an external synchronous signal conditioning circuit for partial discharge detection according to the present invention. DETAILED DESCRIPTION

[0018] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0019] The concept of the present invention is that an external synchronous signal conditioning circuit for partial discharge detection of the present invention includes a voltage conversion module, a waveform conversion module and a waveform shaping module, and the voltage conversion module is connected to the waveform conversion module, and the waveform conversion module is connected to the waveform shaping module. The voltage conversion module obtains the signal to be tested from the corresponding power supply of the high-voltage equipment to be tested, and converts the sine wave. The converted sine wave amplitude voltage can match the working voltage of the conditioning circuit of the present invention and the frequency remains unchanged. The waveform conversion module then converts the converted sine wave into a square wave with unchanged amplitude and frequency. The purpose is that the square wave has a very fast response speed when used as a trigger source, and can effectively trigger the acquisition module of the monitoring device, which is convenient for subsequent detection. Finally, the waveform shaping module shapes the square wave to make its rising edge and falling edge steeper and the amplitude more stable. The partial discharge monitoring device integrated with the external synchronous signal conditioning circuit has high precision and stable detection effect, and realizes the miniaturization of the partial discharge monitoring device.

[0020] Circuit Example: An external synchronous signal conditioning circuit for partial discharge detection in this embodiment is as follows: Figure 1 The figure shows a module diagram of the external synchronous signal conditioning circuit of the present invention, which includes a voltage conversion module 1, a waveform conversion module 2 and a waveform shaping module 3, wherein the voltage conversion module 1 is connected to the waveform conversion module 2, and the waveform conversion module 2 is connected to the waveform shaping module 3.

[0021] The voltage conversion module 1 converts the 220V / 50HZ sine wave of the corresponding power supply of the high-voltage equipment to be tested into a sine wave with an amplitude of 5V / 50Hz. The amplitude is the working voltage of the external synchronous signal conditioning circuit, and the phase and frequency remain unchanged, so as to accurately obtain the accurate power frequency signal. The waveform conversion module 2 converts the 5V / 50Hz sine wave into a 5V / 50Hz square wave. The square wave signal is usually more stable and not easily interfered with. The rising and falling edges of the square wave signal are steep, and its response speed is very fast when used as a trigger source. It can effectively trigger the acquisition module of the monitoring device, which is convenient for the subsequent detection of the power frequency phase angle. The waveform shaping module 3 shapes the square wave to make its rising and falling edges steeper and its amplitude more stable.

[0022] The circuit schematic diagram of the external synchronous signal conditioning circuit of the present invention is as follows Figure 2 As shown, it includes a micro transformer T1, a voltage comparator U1B, a Schmidt inverter U2 and other necessary circuit components. The connections are as follows: the primary winding of the micro transformer T1 is used to connect the corresponding power supply of the high voltage device to be tested, the secondary winding of the micro transformer T1 is respectively connected to the positive input terminal and ground of the comparator U1B, the inverting input of the comparator U1B is grounded to form a zero-crossing detection circuit, and the output terminal of the comparator U1B is connected to the input terminal of the Schmidt inverter U2.

[0023] In order to prevent excessive current from damaging electronic devices, a current limiting resistor is connected in series between the positive input terminal of the voltage comparator U1B and the input terminal of the Schmidt inverter U2. The circuit of this embodiment connects resistors R1 and R3 in series between the micro-transformer T1 and the positive input terminal of the comparator U1B, and between the output terminal of the comparator U1B and the input terminal of the Schmidt inverter U2, respectively. The negative input terminal of the comparator U1B is grounded through the resistor R2, and the secondary winding of the micro-transformer T1 passes through the resistor R4 in series at the output terminal of the Schmidt inverter U2.

[0024] In this embodiment, when the conditioning circuit is working, a 220V / 50Hz sine wave enters the primary winding of the micro-transformer T1, and a 5V / 50Hz sine wave is generated in the secondary winding. The 5V / 50Hz sine wave enters the comparator U1B. The comparator has two input terminals. When the voltage V+ at the non-inverting input terminal is greater than the voltage V- at the inverting input terminal, the output terminal of the comparator will output a high level. When V+ < V-, the output terminal of the comparator will output a low level, realizing the conversion of the sine wave into a square wave. Moreover, the zero-crossing circuit built by the comparator U1B can quickly detect the switching points of the positive and negative half-cycles of the sine wave, and is suitable for use in scenarios of synchronous control. The square wave output by the comparator enters the Schmitt inverter U2, and the Schmitt inverter U2 shapes the square wave, making the rising edge and falling edge of the square wave steeper and the amplitude more stable, which can effectively trigger the acquisition module of the monitoring device and make the detection result more accurate.

[0025] Furthermore, the micro-transformer can also use a variable-ratio transformer, which can be adjusted according to the differences in electrical parameters and convert sine waves without being limited to converting a 220V / 50Hz sine wave into a 5V / 50Hz sine wave, making the applicable range of the conditioning circuit of the present invention wider.

[0026] The waveform conversion diagram of the external synchronization signal conditioning circuit of the present invention is as Figure 3 shown. First, the 220V / 50Hz sine wave is converted into a 5V / 50Hz sine wave, and then into a 5V / 50Hz square wave. It can be seen that the amplitude decreases, the sine wave becomes a square wave, but the frequency and phase remain unchanged, which is convenient for detection.

[0027] Device embodiment: A partial discharge monitoring device includes an external synchronization signal conditioning circuit for partial discharge detection of the present invention and a monitoring device capable of analyzing square wave signals for partial discharge detection; the transformer of the conditioning circuit is connected to the corresponding power supply of the substation maintenance power supply or the switch PT power supply and other high-voltage equipment to be measured to obtain the signal to be measured, and the output terminal of the Schmitt inverter is connected to a monitoring device capable of analyzing square wave signals to obtain the power frequency phase angle and perform partial discharge detection. The partial discharge monitoring device in this embodiment reduces the voltage of the power supply to a voltage range that can work normally, converts the sine wave in the detection power supply into a square wave, and at the same time does not change its phase and frequency. The square wave can effectively trigger the acquisition module of the monitoring device, realizing the precise drawing of the PRPD and PRPS maps of partial discharge and the accurate detection of partial discharge signals.

[0028] The present invention miniaturizes the external synchronization signal conditioning circuit, enabling it to be integrated into the circuit board inside the partial discharge monitoring device, so that the partial discharge monitoring device does not need to additionally install a signal synchronization device or module. It not only realizes the precise drawing of the PRPD map and PRPS map of partial discharge and the accurate detection of partial discharge signals, but also is convenient for on-site installation.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The patent protection scope of the present invention shall be based on the claims. All equivalent structural changes made using the contents of the description and drawings of the present invention should also be included in the protection scope of the present invention.

Claims

1. An external synchronous signal conditioning circuit for partial discharge detection, characterized in that , including a voltage conversion module whose input end is used to connect to the power frequency power supply corresponding to the high-voltage equipment to be tested, a waveform conversion module used to convert the waveform of the power frequency power supply into a square wave, and a waveform shaping module used to shape the square wave to obtain steeper rising and falling edges; the voltage conversion module is used to convert the voltage of the power frequency power supply into the working voltage of the waveform conversion module, the output end of the voltage conversion module is connected to the input end of the waveform conversion module, and the output end of the waveform conversion module is connected to the input end of the waveform shaping module; the output end of the waveform shaping module is used to provide a square wave signal with power frequency phase angle information for partial discharge detection.

2. The external synchronous signal conditioning circuit for partial discharge detection according to claim 1, characterized in that: The voltage conversion module includes a transformer, the contact point of the primary winding of the transformer serves as the input end of the voltage conversion module, and the contact point of the secondary winding of the transformer serves as the output end of the voltage conversion module.

3. The external synchronous signal conditioning circuit for partial discharge detection according to claim 2, characterized in that: The transformer is a variable ratio transformer.

4. The external synchronous signal conditioning circuit for partial discharge detection according to claim 2, characterized in that: The waveform conversion module includes a comparator; the non-phase input end of the comparator is connected to one end of the secondary winding of the transformer, and the other end of the secondary winding of the transformer is grounded; the inverting input end of the comparator is grounded through a voltage-dividing resistor, and the comparator and the resistor constitute a zero-crossing detection circuit; the output end of the comparator serves as the output end of the waveform conversion module.

5. The external synchronous signal conditioning circuit for partial discharge detection according to claim 1, characterized in that: The waveform shaping module comprises a Schmitt inverter; the input end of the Schmitt inverter serves as the input end of the waveform shaping module, and the output end of the Schmitt inverter serves as the output end of the waveform shaping module.

6. A partial discharge monitoring device, characterized in that: It comprises an external synchronous signal conditioning circuit; the external synchronous signal conditioning circuit comprises a voltage conversion module whose input end is used to connect to the power frequency power supply corresponding to the high-voltage equipment to be tested, a waveform conversion module used to convert the waveform of the power frequency power supply into a square wave, and a waveform shaping module used to shape the square wave to obtain steeper rising and falling edges; the voltage conversion module is used to convert the voltage of the power frequency power supply into the working voltage of the waveform conversion module, the output end of the voltage conversion module is connected to the input end of the waveform conversion module, and the output end of the waveform conversion module is connected to the input end of the waveform shaping module; the output end of the waveform shaping module is used to provide a square wave signal capable of obtaining power frequency phase angle information for partial discharge detection.

7. The partial discharge monitoring device according to claim 6, characterized in that: The voltage conversion module includes a transformer, the contact point of the primary winding of the transformer serves as the input end of the voltage conversion module, and the contact point of the secondary winding of the transformer serves as the output end of the voltage conversion module.

8. The partial discharge monitoring device according to claim 7, characterized in that: The transformer is a variable ratio transformer.

9. The partial discharge monitoring device according to claim 7, characterized in that: The waveform conversion module includes a comparator; the non-phase input end of the comparator is connected to one end of the secondary winding of the transformer, and the other end of the secondary winding of the transformer is grounded; the inverting input end of the comparator is grounded through a voltage-dividing resistor, and the comparator and the resistor constitute a zero-crossing detection circuit; the output end of the comparator serves as the output end of the waveform conversion module.

10. The partial discharge monitoring device according to claim 6, characterized in that: The waveform shaping module comprises a Schmitt inverter; the input end of the Schmitt inverter serves as the input end of the waveform shaping module, and the output end of the Schmitt inverter serves as the output end of the waveform shaping module.

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