CN113219264B - On-site measurement device and method for surface charge of high-voltage direct-current sleeve - Google Patents
On-site measurement device and method for surface charge of high-voltage direct-current sleeve Download PDFInfo
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- CN113219264B CN113219264B CN202110593897.3A CN202110593897A CN113219264B CN 113219264 B CN113219264 B CN 113219264B CN 202110593897 A CN202110593897 A CN 202110593897A CN 113219264 B CN113219264 B CN 113219264B
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention discloses a field measurement device and a measurement method for surface charge of a high-voltage direct-current sleeve, comprising the following steps: the lifting table and the stepping unit are used for carrying out radial and axial two-dimensional step scanning on the high-voltage direct-current sleeve; the epoxy frame is arranged on the lifting table and the stepping unit and moves along with the lifting table and the stepping unit, and the high-voltage direct-current sleeve passes through the center of the epoxy frame; a plurality of induction electrodes and signal acquisition modules in the electrostatic probe scanning unit are arranged in holes reserved in the epoxy frame; radial and axial two-dimensional step scanning is carried out on the high-voltage direct-current sleeve through the lifting table and the stepping unit, sinusoidal displacement occurs on the induction electrode relative to the surface of the high-voltage direct-current sleeve, sinusoidal current is induced by the signal acquisition device, the current is converted and then processed, and the surface charge density distribution of the high-voltage direct-current sleeve is calculated. The method is suitable for field test, and can rapidly, safely and accurately measure the surface charge distribution of the high-voltage direct-current sleeve.
Description
Technical Field
The invention relates to the technical field of high-voltage and insulating material surface charge measurement, in particular to a field measurement device and a field measurement method for high-voltage direct-current sleeve surface charge.
Background
Because the resources and the electricity consumption demands of China are reversely distributed, development strategies of national networking, western electric east delivery, north electric south supply and energy optimization configuration must be implemented in order to solve the problem of unbalanced energy distribution and demand and realize national energy optimization configuration. Along with the continuous development of a direct current transmission system, a converter transformer is used as key power equipment for completing alternating current-direct current conversion, and is required to bear the full voltage and the full current of the system and is positioned at a core position in the whole power grid. The valve side sleeve and the direct current wall bushing (hereinafter referred to as direct current sleeve) of the converter transformer are key components for connecting a valve hall of a converter station with an alternating current field and a direct current field device, bear direct current voltage and harmonic current in operation, resist outdoor pollution and rain and snow, and have severe requirements on performances such as insulation, heat, machinery and sealing. However, at present, the most advanced dc bushing research and development key technology is only mastered by very few foreign companies, and as the voltage level is increased and the number of operation is increased, the dc bushing faults frequently occur, the fault cause is not clear, and more students and technicians aim at the bushing. Researches show that the sleeve is influenced by an electric field in the operation process, charges can be accumulated at the umbrella skirt at the intersection of a solid-gas interface to form surface charges, and a large amount of accumulated surface charges can distort the field intensity of the umbrella skirt, so that the withstand voltage of the sleeve is reduced, the electrical performance is reduced, and accidents are easily caused. Therefore, the method has very important academic significance and engineering value for in-depth research on the surface charge distribution of the high-voltage direct-current bushing so as to improve the working reliability of the direct-current bushing and ensure the safe and stable operation of the whole power system.
The surface charge measurement technique is one of important techniques for grasping the mechanism of discharge of an insulating surface. Currently, common surface charge measurement techniques include dust-patterning, pockels electro-optical effect, electrostatic probe, and the like. However, the existing methods have obvious defects, and the dust method has the defects that the surface charge value cannot be accurately measured, and the charge distribution of the medium surface can be changed in the spraying process, so that the surface charge condition of the medium surface is changed. The Pockels effect method is only suitable for measuring transparent film insulation test samples. The electrostatic probe method can effectively ensure the measurement resolution and greatly reduce the requirement of the probe inlet capacitance on the stability, so that the electrostatic probe scanning method is the most feasible implementation mode for measuring the surface charge of the insulating material at present. However, the measurement range of the existing electrostatic probe method is limited, and the field measurement cannot be performed under a higher voltage level. Most of the existing test objects surround GIS and insulators, the test methods using the sleeve as a research object are few, and the existing static measurement device and method cannot be suitable for on-site sleeve surface measurement.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the related art to some extent.
Therefore, an object of the present invention is to provide a device for measuring the surface charge of a high-voltage dc bushing in situ, which can overcome the drawbacks of the prior art that the surface charge cannot be measured accurately on site, at high voltage, on uneven surfaces and in large-sized structures.
Another object of the present invention is to provide a method for in-situ measurement of surface charge of a high voltage dc bushing.
In order to achieve the above object, an embodiment of the present invention provides an in-situ measurement device for surface charge of a high voltage dc bushing, including: the device comprises a lifting table, a stepping unit, an epoxy frame, an electrostatic probe scanning unit, a high-voltage direct-current sleeve, a high-voltage lead and a capacitive voltage divider;
the high-voltage direct current sleeve is connected with the high-voltage lead, and the capacitive divider is used for providing high-voltage direct current and transmitting the high-voltage direct current to the high-voltage direct current sleeve through the high-voltage lead;
the lifting platform and the stepping unit are ground equipment and are used for carrying out radial and axial two-dimensional step scanning on the high-voltage direct-current sleeve;
the epoxy frame is arranged on the lifting table and the stepping unit and moves along with the lifting table and the stepping unit, and the high-voltage direct-current sleeve passes through the center of the epoxy frame;
a plurality of induction electrodes and signal acquisition modules in the static probe scanning unit are arranged in reserved holes of the epoxy frame and are fixed through a fixing knob; and carrying out radial and axial two-dimensional step scanning on the high-voltage direct-current sleeve through the lifting table and the stepping unit, enabling the induction electrode to generate sinusoidal regular displacement relative to the surface of the high-voltage direct-current sleeve, utilizing the signal acquisition device to induce sinusoidal regular-change current, carrying out signal conversion on the current, then processing the current, and calculating the surface charge density distribution of the high-voltage direct-current sleeve.
Optionally, the induction electrodes are embedded in the upper, lower, left and right holes of the epoxy frame, and the distances between the induction electrodes and the surface of the high-voltage direct-current sleeve are the same.
Optionally, the static probe scanning unit comprises a metal shell, the induction electrode, a high-resistance insulating blocking medium, a voltage equalizing electrode, the signal acquisition module, a signal conversion module, a wireless acquisition transmission system, data acquisition and processing software and a UPS uninterrupted direct current power supply;
the high-resistance insulating blocking medium is equidistantly arranged in front of the induction electrode and connected with the signal acquisition module, and is used for dividing voltage under direct current to protect the induction electrode from breakdown;
the voltage equalizing electrode is connected with the metal shell, is in the same plane with the induction electrode but is not contacted with the induction electrode, and is used for homogenizing an electric field;
the signal acquisition module is arranged in the metal shell and is used for sensing the current of the induction electrode, which is slightly and sinusoidally changed relative to the surface of the high-voltage direct-current sleeve;
the signal conversion module is connected with the signal acquisition module and is used for converting the analog signals acquired by the signal acquisition module into digital signals;
the wireless acquisition and transmission system is connected with the signal conversion module and the data acquisition and processing software and is used for transmitting the digital signals converted by the signal conversion module to the data acquisition and processing software;
the data acquisition and processing software is used for converting the digital signals into analog signals, displaying potential waveforms and carrying out charge inversion to obtain the surface charge density distribution of the high-voltage direct-current sleeve;
the UPS uninterrupted DC power supply is used for supplying power to the static probe scanning unit;
optionally, the signal acquisition module comprises a differential operational amplifier, a sinusoidal oscillator and a pre-proportioner;
the differential operational amplifier is used for removing the potential on the high-resistance insulating blocking medium to obtain the real potential of the surface of the direct current sleeve;
the sine oscillator is used for driving the induction electrode to generate sine displacement change;
the prepositive proportional amplifier is used for receiving the analog signals transmitted from the induction electrode, and the feedback loop of the prepositive proportional amplifier is provided with an adjustable resistor for changing the amplification factor.
Optionally, the signal conversion module includes: the phase sensitive detector, the integrator, the protection resistor and the auxiliary power supply;
the phase sensitive detector is used for detecting the phase of a current waveform and converting an analog signal into a digital signal;
the integrator is used for carrying out accumulation processing on the input signals to obtain a result, and the output end of the integrator is grounded through the protection resistor;
the auxiliary power supply is used for feeding back signals to the induction electrode, so that the surface potential of the induction electrode is the same as that of the high-voltage direct-current sleeve.
Optionally, the wireless acquisition and transmission system comprises a wireless sending module and a wireless receiving module;
the wireless transmitting module is connected with the signal conversion module, and the wireless receiving module is connected with the data acquisition and processing software.
Optionally, a connecting shaft opening and closing structure is arranged on the epoxy frame to open and close, so that the high-voltage direct-current sleeve enters the center of the epoxy frame.
Optionally, a support frame is arranged at the bottom of the epoxy frame and used for stepping on the sliding rail.
In order to achieve the above objective, another embodiment of the present invention provides a method for in-situ measurement of surface charge of a high voltage dc bushing, comprising the steps of:
adjusting the installation position of a field measurement device of the surface charge of the high-voltage direct-current sleeve;
carrying out no-load test on the high-voltage direct-current sleeve, setting the polarization time and the polarization voltage of the high-voltage direct-current sleeve, and carrying out pressure relief treatment on a wall-through sleeve guide rod after the polarization time is reached;
opening a connecting shaft opening and closing structure of the epoxy frame, controlling a lifting table and a stepping unit to enable the epoxy frame to ascend at a constant speed, radially scanning the high-voltage direct-current sleeve, stopping scanning until a probe at the lowest part of the epoxy frame reaches a preset distance, and closing the upper end of the epoxy frame to store radial scanning data;
the lifting table and the stepping unit are controlled to perform axial stepping scanning on the surface of the high-voltage direct-current sleeve, and axial scanning data are stored;
and carrying out surface charge density inversion calculation according to the radial scanning data and the stored axial scanning data to obtain the surface charge density distribution of the high-voltage direct-current sleeve.
The device and the method for measuring the surface charge of the high-voltage direct-current sleeve in the embodiment of the invention have the following advantages:
1. the device is suitable for field measurement, is suitable for environments complicated and changeable with the field, and can reliably and rapidly measure;
2. the invention is suitable for high voltage measurement, and can be used for measuring the sleeve with the voltage of 400kV and above;
3. the invention is suitable for measuring the uneven surface of a large-size sleeve, and the umbrella skirt on the surface of the sleeve is uneven;
4. the reading can be measured remotely, and the safety of the personnel is ensured. The invention is small in size, is wholly insulated and self-powered, allows measurements to be performed with maximum security without requiring direct connection to the system under inspection, and allows remote measurements of the component to be tested, whereby an operator can stand remotely and does not need to power down the system for inspection.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a schematic diagram of an in-situ measurement device for surface charge of a high voltage DC bushing according to one embodiment of the invention;
FIG. 2 is a schematic diagram of an electrostatic probe unit according to one embodiment of the invention;
FIG. 3 is a schematic diagram of overall signal transmission according to one embodiment of the invention;
FIG. 4 is a schematic diagram of a design flow according to one embodiment of the invention;
fig. 5 is a flow chart of a method for in-situ measurement of surface charge of a high voltage dc bushing according to one embodiment of the invention.
Reference numerals: the device comprises a lifting platform, a stepping unit, a 2-epoxy frame, a 3-static probe scanning unit, a 3, 4-fixing knob, a 5-reinforcing structure, a 6-connecting shaft opening and closing structure, a 7-sensing electrode, an 8-supporting frame, a 9-sliding rail, a 10-porous socket line row, an 11-wireless transmitting module, a 12-pre-proportion amplifier, a 13-sine oscillator, a 14-UPS uninterrupted direct current power supply, a 15-wireless receiving module, 16-data acquisition and processing software, a 17-protection resistor, a 18-phase sensitive detector, a 19-integrator, a 20-auxiliary power supply, a 21-signal conversion module, a 22-signal acquisition module, a 23-high-voltage direct current sleeve, a 24-simulation wall, a 25-high-voltage lead, a 26-capacitor voltage divider, a 27-differential operational amplifier, a 28-high-resistance insulation blocking medium, a 29-voltage equalizing electrode and a 30-metal shell.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
In the following, an in-situ measurement device and a measurement method for the surface charge of a high-voltage direct-current bushing according to an embodiment of the present invention are described with reference to the accompanying drawings.
An in-situ measurement device for surface charge of a high voltage dc bushing according to an embodiment of the present invention will be described with reference to the accompanying drawings.
Fig. 1 is a schematic view of an in-situ measurement device for surface charge of a high voltage dc bushing according to an embodiment of the present invention.
As shown in fig. 1, the in-situ measurement device of the surface charge of the high-voltage direct-current bushing comprises: elevating platform and step unit 1, epoxy frame 2, static probe scanning unit 3, high voltage direct current sleeve 23, high voltage lead 25, electric capacity divider 26.
The high voltage dc bushing 23 is connected to a high voltage lead 25, and a capacitive voltage divider 26 is used to provide high voltage dc and to transfer the high voltage dc to the high voltage dc bushing 23 via the high voltage lead 25.
The lifting table and stepping unit 1 is a ground device for performing radial and axial two-dimensional step scanning on the high-voltage direct-current sleeve 23.
The epoxy frame 2 is mounted on the lifting table and the stepping unit 1, and moves along with the lifting table and the stepping unit 1, and the high-voltage direct-current sleeve 23 penetrates through the center of the epoxy frame 2.
A plurality of induction electrodes 7 and signal acquisition modules 22 in the electrostatic probe scanning unit 3 are arranged in reserved holes of the epoxy frame 2 and are fixed through a fixing knob 4; the high-voltage direct current sleeve 23 is subjected to radial and axial two-dimensional step scanning through the lifting table and the stepping unit 1, sinusoidal displacement occurs to the sensing electrode 7 relative to the surface of the high-voltage direct current sleeve 23, sinusoidal current is sensed by the signal acquisition device 22, the current is converted and then processed, and the charge density distribution of the surface of the high-voltage direct current sleeve is calculated.
Alternatively, in some embodiments, the sensing electrodes 7 are embedded in four holes of the epoxy frame 2, i.e., the upper, lower, left, and right holes, and each sensing electrode 7 is spaced the same distance from the surface of the high voltage dc bushing 23.
As shown in fig. 1, 2 and 3, the epoxy frame 2 can be opened and closed by the axle opening and closing structure 6 so that the sleeve can enter the center of the epoxy frame.
The reinforcing structure is designed at the bottom of the epoxy frame 2, so that the influence of shaking of the epoxy frame 2 in the scanning process on experimental results is avoided. Holes are reserved on the upper part, the lower part, the left part and the right part of the epoxy frame 2 and are used for arranging the induction electrode 7 and the signal acquisition module 22. The fixing knob 4 is arranged outside the hole and used for fixing and stepping the induction electrode 7, so that the induction electrode is ensured not to shake in the measuring process, and the distance between each induction electrode and the sleeve is ensured to be the same.
Optionally, in some embodiments, the electrostatic probe scanning unit includes a metal housing 30, an inductive electrode 7, a high resistance insulating barrier medium 28, a voltage equalizing electrode 29, a signal acquisition module 22, a signal conversion module 21, wireless acquisition and transmission systems (11 and 15), data acquisition and processing software 16, a UPS uninterruptible dc power supply 14.
A high-resistance insulating barrier medium 28 is equidistantly arranged in front of the induction electrode 7 and is connected with the signal acquisition module 22 for voltage division under direct current to protect the induction electrode 7 from breakdown.
The voltage equalizing electrode 29 is connected with the metal casing 30, is in the same plane with the induction electrode 7 but is not contacted with each other, and is used for equalizing the electric field.
The signal acquisition module 22 is disposed inside the metal casing 30, and is used for sensing the current of the sensing electrode 7, which is slightly and sinusoidally changed relative to the surface of the sleeve.
The signal conversion module 21 is connected to the signal acquisition module 22, and is configured to convert the analog signal acquired by the signal acquisition module 22 into a digital signal.
The wireless acquisition and transmission system is connected with the signal conversion module 21 and the data acquisition and processing software 16, and is used for transmitting the digital signal converted by the signal conversion module 21 to the data acquisition and processing software 16.
The data acquisition and processing software 16 is used for converting the digital signals into analog signals, displaying potential waveforms and performing charge inversion to obtain the surface charge density distribution of the high-voltage direct-current sleeve.
The UPS uninterruptible dc power supply 14 is used to power the electrostatic probe scanning unit.
As shown in fig. 1, 2 and 3, the electrostatic probe scanning unit 3 includes a high-resistance insulating blocking medium 28, a voltage equalizing electrode 29, an induction electrode 7, a signal acquisition module 22, a signal conversion module 21, wireless acquisition and transmission systems (11 and 15), data acquisition and processing software 16, and a UPS uninterruptible dc power supply 14. The high-resistance insulating barrier medium 28 serves as a voltage dividing unit under direct current to protect the induction electrode 7 from breakdown. The voltage equalizing electrode 29 is connected to the metal casing 30 as a voltage equalizing unit for protecting the induction electrode and the internal weak current device. The sensing electrode 7 will generate a tiny sinusoidal displacement relative to the surface of the sleeve, at this time, the signal acquisition device 22 will sense a sinusoidal current, modulate the analog signal into a digital signal through the signal conversion device 21, transmit the signal through the wireless acquisition and transmission system, and the data acquisition and processing software 16 demodulates the digital signal into an analog signal.
The sensing electrodes are firmly embedded in the upper, lower, left and right walls of the epoxy frame and the same distance between each electrode and the surface of the sleeve is ensured. The vibration direction of the induction electrode is perpendicular to the surface to be measured, and the distance between the induction electrode and the surface to be measured is changed in a sine rule. When the sensing electrode approaches the surface to be measured, an equivalent capacitance C is generated between the sensing electrode and the surface to be measured, and the magnitude of the capacitance C can be expressed by the following formula:
wherein epsilon is the dielectric constant of the gas between the sensing electrode and the surface to be measured, D 0 For sensing the distance between the electrode and the surface to be measured, D 1 For the amplitude of the sensing electrode, ω is the angular frequency of the sensing electrode vibration and S is the sensing electrode surface area. Let the potential of the measured surface be U 1 The potential on the induction electrode is U 2 The potential difference between the two is Δu=u 1 -U 2 . If ΔU+.0 is present, then a current i will flow through the sense electrode, which has the following magnitude:
wherein the gas isDielectric constant epsilon, area S of sensing electrode, vibration frequency omega, vibration amplitude D 1 As a constant, it can be seen from the above equation that the current i is proportional to the potential difference Δu and inversely proportional to D 0 2 . Thus, if D is maintained during measurement 0 Unchanged, then i is related to deltau only.
Optionally, in some embodiments, the signal acquisition module 22 includes a differential op-amp 27, a sinusoidal oscillator 13, and a pre-amp 12.
The differential op-amp 27 is used to remove the potential on the high resistance insulating barrier medium 28 to obtain the true potential of the dc bushing surface 23.
The sinusoidal oscillator 13 is used for driving the induction electrode 7 to perform sinusoidal displacement change.
The pre-amplifier 12 is used for receiving the analog signal transmitted from the sensing electrode 7, and an adjustable resistor is arranged on the feedback loop of the pre-amplifier 12 to change the amplification factor.
Optionally, in some embodiments, the signal conversion module 21 includes: a phase sensitive detector 18, an integrator 19, a protection resistor 17, an auxiliary power supply 20.
The phase sensitive detector 18 is used to detect the phase of the current waveform and to convert the analog signal into a digital signal.
The integrator 19 is used for performing accumulation processing on the input signals to calculate a result, and the output end is grounded through the protection resistor 17.
The auxiliary power supply 20 is used for feeding back signals to the sensing electrode 7, so that the surface potential of the sensing electrode 7 is the same as that of the high-voltage direct-current sleeve 23.
Specifically, the signal conversion module comprises a phase sensitive detector, an integrator, a protection resistor and an auxiliary power supply. After i is amplified by a two-stage amplifying circuit, the i is input to a phase sensitive detector in a signal conversion module, and the phase sensitive detector can detect the phase of a current waveform and is used for converting an analog signal into a digital signal; the integrator is used for carrying out accumulation processing on the input signals to obtain a result, and the output end is grounded through the protection resistor; the auxiliary voltage source in the signal conversion module is controlled to output direct-current high voltage to the induction electrode by the magnitude of the result, and at the moment, delta U changes to cause i to change accordingly, so that negative feedback is formed, and the surface potential of the induction electrode is the same as that of the sleeve finally. At this time, the output voltage of the voltage source in the signal conversion module is the potential of the measured surface, and meanwhile, as the potentials of the voltage source and the signal conversion module are the same, breakdown is not easy to occur, thereby achieving the purpose of protecting the induction electrode.
The wireless acquisition and transmission system comprises a wireless transmitting module 11 and a wireless receiving module 15. The transmission module 11 is connected to the signal conversion module 21, wherein the transmission module provides a BNC connector to externally provide the output signals of the amplifiers, respectively; the wireless receiving module 15 is connected to the PC terminal where the data acquisition and processing software 16 is located, wherein a synchronization circuit is built in the wireless receiving module for detecting the voltage amplitude of the source object by capacitive coupling, so that the detected signals are synchronized with the voltage generating them.
The data acquisition and processing software 16 is used for converting digital signals into analog signals and displaying potential waveforms, and provides functional settings for acquisition, processing and storage and/or transmission of acquired signals, supporting USB3.0, bluetooth 4.0, ethernet, wiFi and other technologies for communication.
The UPS uninterrupted DC power supply is used for providing 12V stable DC power supply.
In practice, when the invention is applied to potential measurement, the output potential at the measured point is the superposition of the combined actions of all the surface charges of the measured surface. Therefore, the key of researching the solid-gas interface charge by adopting the method is how to calculate the density distribution of the surface charge of the insulator according to the surface potential distribution of the insulator measured by the probe, namely the surface charge inversion calculation based on the surface potential.
As shown in fig. 4, which is a main design idea of an embodiment of the invention, the signal that can be obtained by the device has an increased amplitude due to the use of a series of amplifier stages.
The specific structure will be described in detail with reference to the accompanying drawings.
As shown in fig. 1, an overall structure of the embodiment is shown. The device comprises a lifting table, a stepping unit 1, an epoxy frame 2, an electrostatic probe scanning unit 3, a high-voltage direct-current sleeve 23, a high-voltage lead 25 and a capacitive voltage divider 26. The high voltage dc bushing 23 passes through the analog wall 24 and the capacitive divider 26 provides high voltage dc and is connected to the high voltage dc bushing 23 by the high voltage lead 25. The elevator and stepping unit 1 is ground equipment, and can perform radial and axial two-dimensional step scanning on the high-voltage direct-current sleeve 23. The bottom of the epoxy frame 2 is provided with a supporting frame 8 for stepping on a sliding rail 9. The epoxy frame 2 is stably arranged on the lifting platform and can move along with the platform. The upper part of the epoxy frame 2 can be opened and closed by the connecting shaft opening and closing structure 6, so that the sleeve 23 can enter the center of the epoxy frame 2. The reinforcing structure 5 is designed at the bottom of the frame, so that the frame is prevented from shaking in the scanning process, and experimental results are prevented from being influenced. Holes are reserved on the upper part, the lower part, the left part and the right part of the frame for arranging the induction electrode 7 and the signal acquisition module 22. The sensing electrodes 7 are firmly embedded in the four walls of the epoxy frame 2, up, down, left and right, and the distance between each electrode and the surface of the sleeve is ensured to be the same. The fixing knob 4 is arranged outside the hole and used for fixing and stepping the induction electrode 7, so that the induction electrode is ensured not to shake in the measuring process, and the distance between each induction electrode and the sleeve is ensured to be the same.
As shown in fig. 2, the electrostatic probe unit includes an induction electrode 7, a voltage equalizing electrode 29, a metal casing 30, and a signal acquisition module 22. Wherein, high resistance insulating barrier medium 28 is equidistantly arranged in front of each sensing electrode for voltage division and has the function of protecting the sensing electrode, and the barrier medium 28 is connected with differential operational amplifier 27. The voltage equalizing electrodes 29, which are in the same plane as the sensing electrodes 7 but are not in contact with each other, serve to equalize the electric field, preventing air from being broken down due to the fact that the measuring distance is too short, the electric field becomes large. The signal acquisition module 22 includes a differential operational amplifier 27, a sinusoidal oscillator 13 and a pre-scaler 12. The differential operational amplifier 27 is used for removing the potential on the high-resistance insulating blocking medium 28 so as to obtain the real potential of the surface of the sleeve; the sine oscillator 13 is used for driving the induction electrode 7 to generate tiny sine displacement change; the pre-proportional amplifier 12 is used for receiving the analog signals transmitted by the sensing electrode 7, an adjustable resistor is arranged on a feedback loop of the pre-proportional amplifier to change the amplification factor, and 4 gear knobs with different ranges are arranged through the adjustable resistor; wherein the signal channel acquisition frequency is 10Hz, i.e. one signal is acquired every 0.1 s.
As shown in fig. 3, the signal transmission system includes a signal conversion module 21, a wireless acquisition and transmission system, data acquisition and processing software 16, and a UPS uninterruptible dc power supply 14. The sensing electrode 7 will generate a tiny sinusoidal displacement relative to the surface of the sleeve 23, at this time, the signal acquisition device 22 will sense a sinusoidal current, modulate the analog signal into a digital signal through the signal conversion device 21, transmit the signal through the wireless acquisition and transmission system, and the data acquisition and processing software 16 demodulates the digital signal into an analog signal.
The signal conversion module 21 comprises a phase sensitive detector 18, an integrator 19, a protection resistor 17 and an auxiliary power supply 20. The phase sensitive detector 18 may detect the phase of the current waveform for converting the analog signal to a digital signal; the integrator 19 is used for performing accumulation processing on the input signals to calculate a result, and the output end is grounded through the protection resistor 17; the auxiliary power supply 20 feeds back signals to the induction electrode, so that the surface potential of the induction electrode is the same as that of the sleeve, and breakdown is not easy to occur, thereby achieving the purpose of protecting the induction electrode 7.
Acquisition and processing software 16 is used to convert the digital signals to analog signals, display the potential waveforms and perform charge inversion. Wherein, the signal received from the wireless receiving module 15 is transmitted to the communication module at the PC end through USB serial port communication; the data bit is 8 bits, and one bit is a stop bit; the serial communication rate is 9600bps/s, namely 9600 bit binary codes can be transmitted per second; the number of signal channels is set to be at most 4 channels, namely, the signal waveforms of at most 4 channels can be displayed simultaneously.
According to the field measurement device for the surface charge of the high-voltage direct-current sleeve, provided by the embodiment of the invention, the surface area of the sensing electrode of the probe is increased through the preposed blocking medium so as to adapt to a high-field intensity environment; the variable range is set to solve the problem that current saturation exists under high field intensity and measurement cannot be performed, so that the technical difficulty that the prior art cannot perform on-site measurement is overcome; the problem that large-size and complex surfaces cannot be accurately measured is solved by arranging two-dimensional stepping; through digital signal processing and remote signal transmission, the risk of operation under high pressure of on-site staff is reduced. The invention takes 400kV dry-type direct current sleeve as an example, designs a set of system for carrying out field measurement on the surface charge of the high-voltage direct current sleeve, provides a novel measurement means for accurately measuring the surface charge of the high-voltage direct current sleeve, and is not only suitable for high-voltage class, but also suitable for carrying out field measurement on the sleeve with complex surface structure. The method is suitable for field test, and can rapidly, safely and accurately measure the surface charge distribution of the high-voltage direct-current sleeve.
Next, an in-situ measurement method of the surface charge of the high-voltage direct-current bushing according to an embodiment of the present invention will be described with reference to the accompanying drawings.
Fig. 5 is a flow chart of a method for in-situ measurement of surface charge of a high voltage dc bushing according to one embodiment of the invention.
As shown in fig. 5, the in-situ measurement method of the surface charge of the high-voltage direct-current bushing comprises the following steps:
s1, adjusting the installation position of a field measurement device of the surface charge of the high-voltage direct-current sleeve.
S2, carrying out no-load test on the high-voltage direct-current sleeve, setting the polarization time and the polarization voltage of the high-voltage direct-current sleeve, and carrying out pressure relief treatment on the wall-through sleeve guide rod after the polarization time is reached.
S3, opening a connecting shaft opening and closing structure of the epoxy frame, controlling the lifting table and the stepping unit to enable the epoxy frame to ascend at a constant speed, radially scanning the high-voltage direct-current sleeve, stopping scanning until the lowest probe of the epoxy frame reaches a preset distance, and closing the upper end of the epoxy frame to store radial scanning data.
S4, axial step scanning is carried out on the surface of the high-voltage direct-current sleeve by controlling the lifting table and the stepping unit, and axial scanning data are stored.
S5, carrying out surface charge density inversion calculation according to the radial scanning data and the saved axial scanning data to obtain the surface charge density distribution of the high-voltage direct current sleeve.
Specifically, the field measurement method of the surface charge of the high-voltage direct-current sleeve is as follows:
step 1: the experimental device is ensured to be connected correctly, and the reliable grounding and normal communication are ensured;
step 2: the static measuring device performs field calibration and zeroing, the induction electrodes 7 are adjusted to safe and reasonable positions (the higher the measured voltage level is, the larger the allowance between the induction electrodes 7 and the sleeve 23 is), the same distance between the 4 induction electrodes 7 and the sleeve is ensured, and at the moment, the zeroing knob is turned to perform zeroing; if the numerical value is larger after the zeroing knob is used on site, the zeroing can be performed by using matched software.
Step 3: the positions of the lifting table, the stepping unit 1, the epoxy frame 2 and the direct current sleeve 23 are adjusted. Ensuring that the lower lifting platform 1 and the epoxy frame 2 are adjusted to be parallel to the sleeve 23, and ensuring that the distance between the epoxy frame 2 and the sleeve 23 is within a specified error range after the epoxy frame 2 ascends;
step 4: before beginning the experiment, the field environment needs to be recorded in detail, including but not limited to: weather, temperature, humidity, wind direction, wind speed;
step 5: carrying out no-load test on the wall bushing 23, setting the bushing polarization time and polarization voltage, and keeping the slide rail and the measuring system away from the wall bushing during pressurization;
step 6: after the polarization time is reached, the pressure (or short circuit) is removed from the wall bushing guide rod;
step 7: after the safety and the epoxy frame 2 are determined to be in the open state, the lifting table is rapidly controlled, so that the epoxy frame 2 ascends at a constant speed.
Step 8: during the ascending period, the sleeve is radially scanned until the lowest probe of the epoxy frame 2 reaches a specified distance, the scanning is stopped, radial scanning data are stored, and the upper end of the epoxy frame is closed.
Step 9: by controlling the stepping motor, the electrostatic measuring system 3 is moved to the sleeve outer sheath measuring start end. An axial step measurement is started at the casing surface. By controlling the speed and the position of the sliding rail, the quick scanning of the surface potential of the horizontal different positions of the sleeve is realized (the total scanning time is controlled within a short time, for the 400kV sleeve, according to one-point calculation of one umbrella skirt measurement, the measurement is finished when reaching the termination end, the measurement point is divided in advance, the stepping motor is moved to one-point position, hovers for a period of time after stabilization, and then steps to the next-point position for measurement, and the starting umbrella skirt and the termination umbrella skirt are required to cooperate with the polarization voltage of the sleeve to ensure that the equipment is at a safe distance.
Step 10: after measurement, the related system resets and axial scanning data are saved; it is recommended to repeat the measurement of step 9 for 1-2 times;
step 11: after the depolarization experiment is finished in the step 10, the epoxy frame is moved to the initial position of the measurement ground after the needed depolarization time is reached;
step 12: adjusting different experimental groups, and then performing the experiments of the steps 7 to 11;
step 13: and carrying out surface charge density inversion calculation by using the measured surface potential.
It should be noted that the foregoing explanation of the apparatus method embodiment is also applicable to the method of this embodiment, and will not be repeated here.
The field measurement method of the surface charge of the high-voltage direct-current sleeve provided by the embodiment of the invention is suitable for field measurement, is suitable for environments complicated and changeable with the field, and can reliably and rapidly measure; the device is suitable for high-voltage measurement and can be used for measuring a sleeve of 400kV or more; the method is suitable for uneven surface measurement of a large-size sleeve, and the uneven umbrella skirt on the surface of the sleeve is still suitable; the reading can be measured remotely, and the safety of the personnel is ensured. The small size, overall insulation and self-powering allow measurements to be performed with maximum security without requiring direct connection to the system under inspection, and also allow remote measurements of the component to be tested, whereby the operator can stand far away and without having to power down the system for detection.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.
Claims (8)
1. An in-situ measurement device for surface charge of a high voltage dc bushing, comprising: the device comprises a lifting table, a stepping unit, an epoxy frame, an electrostatic probe scanning unit, a high-voltage direct-current sleeve, a high-voltage lead and a capacitive voltage divider;
the high-voltage direct current sleeve is connected with the high-voltage lead, and the capacitive divider is used for providing high-voltage direct current and transmitting the high-voltage direct current to the high-voltage direct current sleeve through the high-voltage lead;
the lifting platform and the stepping unit are ground equipment and are used for carrying out radial and axial two-dimensional step scanning on the high-voltage direct-current sleeve;
the epoxy frame is arranged on the lifting table and the stepping unit and moves along with the lifting table and the stepping unit, and the high-voltage direct-current sleeve passes through the center of the epoxy frame;
a plurality of induction electrodes and signal acquisition modules in the static probe scanning unit are arranged in reserved holes of the epoxy frame and are fixed through a fixing knob; radial and axial two-dimensional step scanning is carried out on the high-voltage direct-current sleeve through the lifting table and the stepping unit, sinusoidal regular displacement occurs to the induction electrode relative to the surface of the high-voltage direct-current sleeve, sinusoidal regular changing current is induced by the signal acquisition device, signal conversion is carried out on the current, then the current is processed, and the surface charge density distribution of the high-voltage direct-current sleeve is calculated;
the epoxy frame is provided with a connecting shaft opening and closing structure for opening and closing, so that the high-voltage direct-current sleeve enters the center of the epoxy frame.
2. The device of claim 1, wherein the sensing electrodes are embedded in four holes of the epoxy frame, namely, upper hole, lower hole, left hole and right hole, and each sensing electrode is at the same distance from the surface of the high-voltage direct-current sleeve.
3. The device of claim 1, wherein the electrostatic probe scanning unit comprises a metal housing, the sensing electrode, a high-resistance insulating barrier medium, a voltage equalizing electrode, the signal acquisition module, a signal conversion module, a wireless acquisition transmission system, data acquisition and processing software, and a UPS uninterruptible dc power supply;
the high-resistance insulating blocking medium is equidistantly arranged in front of the induction electrode and connected with the signal acquisition module, and is used for dividing voltage under direct current to protect the induction electrode from breakdown;
the voltage equalizing electrode is connected with the metal shell, is in the same plane with the induction electrode but is not contacted with the induction electrode, and is used for homogenizing an electric field;
the signal acquisition module is arranged in the metal shell and is used for sensing the current of the induction electrode, which is slightly and sinusoidally changed relative to the surface of the high-voltage direct-current sleeve;
the signal conversion module is connected with the signal acquisition module and is used for converting the analog signals acquired by the signal acquisition module into digital signals;
the wireless acquisition and transmission system is connected with the signal conversion module and the data acquisition and processing software and is used for transmitting the digital signals converted by the signal conversion module to the data acquisition and processing software;
the data acquisition and processing software is used for converting the digital signals into analog signals, displaying potential waveforms and carrying out charge inversion to obtain the surface charge density distribution of the high-voltage direct-current sleeve;
the UPS uninterrupted DC power supply is used for supplying power to the static probe scanning unit.
4. The apparatus of claim 3, wherein the signal acquisition module comprises a differential op-amp, a sinusoidal oscillator, and a pre-amp;
the differential operational amplifier is used for removing the potential on the high-resistance insulating blocking medium to obtain the real potential on the surface of the high-voltage direct-current sleeve;
the sine oscillator is used for driving the induction electrode to generate sine displacement change;
the prepositive proportional amplifier is used for receiving the analog signals transmitted from the induction electrode, and the feedback loop of the prepositive proportional amplifier is provided with an adjustable resistor for changing the amplification factor.
5. The apparatus of claim 3, wherein the signal conversion module comprises: the phase sensitive detector, the integrator, the protection resistor and the auxiliary power supply;
the phase sensitive detector is used for detecting the phase of a current waveform and converting an analog signal into a digital signal;
the integrator is used for carrying out accumulation processing on the input signals to obtain a result, and the output end of the integrator is grounded through the protection resistor;
the auxiliary power supply is used for feeding back signals to the induction electrode, so that the surface potential of the induction electrode is the same as that of the high-voltage direct-current sleeve.
6. The apparatus of claim 3, wherein the wireless acquisition and transmission system comprises a wireless transmit module and a wireless receive module;
the wireless transmitting module is connected with the signal conversion module, and the wireless receiving module is connected with the data acquisition and processing software.
7. The device of claim 1, wherein the epoxy frame has a support frame disposed at the bottom for stepping on a slide rail.
8. A method for in-situ measurement of surface charge of a high voltage dc bushing, characterized in that it is applied to an in-situ measurement device of surface charge of a high voltage dc bushing according to any one of claims 1 to 7, comprising the steps of:
adjusting the installation position of a field measurement device of the surface charge of the high-voltage direct-current sleeve;
carrying out no-load test on the high-voltage direct-current sleeve, setting the polarization time and the polarization voltage of the high-voltage direct-current sleeve, and carrying out pressure relief treatment on a guide rod of the high-voltage direct-current sleeve after the polarization time is reached;
opening a connecting shaft opening and closing structure of the epoxy frame, controlling a lifting table and a stepping unit to enable the epoxy frame to ascend at a constant speed, radially scanning the high-voltage direct-current sleeve, stopping scanning until a probe at the lowest part of the epoxy frame reaches a preset distance, and closing the upper end of the epoxy frame to store radial scanning data;
the lifting table and the stepping unit are controlled to perform axial stepping scanning on the surface of the high-voltage direct-current sleeve, and axial scanning data are stored;
and carrying out surface charge density inversion calculation according to the radial scanning data and the axial scanning data to obtain the surface charge density distribution of the high-voltage direct-current sleeve.
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| CN114236253B (en) * | 2021-12-13 | 2022-10-25 | 西安交通大学 | Surface charge measurement system of super/extra-high voltage wall bushing scaling model |
| CN114527337B (en) * | 2022-01-14 | 2023-04-21 | 深圳市中明科技股份有限公司 | Non-contact type electrostatic field detection sensing probe device and system |
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