CN109342910B - Full-electric partial discharge detection device and detection method - Google Patents
Full-electric partial discharge detection device and detection method Download PDFInfo
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/14—Circuits therefor, e.g. for generating test voltages, sensing circuits
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
- G01R31/1263—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
- G01R31/1272—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation of cable, line or wire insulation, e.g. using partial discharge measurements
Abstract
The invention discloses a full-electric partial discharge detection device and a detection method, wherein the detection device comprises the following steps: the system comprises a high-voltage charging unit, a capacitor matrix unit, a voltage regulating unit, an inversion unit, a power electronic switch unit, an inductance matrix unit, a measuring unit and a host system; the output end of the high-voltage charging unit is connected with the input end of the capacitor matrix unit, and the high-voltage charging unit is used for providing electric energy for the capacitor matrix unit; the output end of the capacitor matrix unit is connected with the input end of the voltage regulating unit, and the output end of the voltage regulating unit is connected with the input end of the inversion unit; a power electronic switch unit is connected in parallel between the two output ends of the inversion unit; one output end of the inversion unit is grounded, and the other output end of the inversion unit is connected with the inductance matrix unit in series; the inductance matrix unit is used for connecting a tested product; the measuring unit is used for being connected in parallel at two ends of a tested product; the host system is connected with the control electrode of the switching device in each unit. The invention does not need an extra high-power supply and can improve the detection efficiency.
Description
Technical Field
The invention belongs to the technical field of insulation state detection of power equipment, and particularly relates to a full-electric partial discharge detection device and a detection method.
Background
With the development of the times, the lives of people are gradually improved, and the electricity consumption in China is sharply increased. In order to meet the increasing demand of electric power, the power transmission network in China develops rapidly, and the capacity and the voltage level of electric power equipment are continuously improved. The insulation performance of power equipment is becoming more and more acute, and high-capacity and high-voltage power equipment puts higher requirements on insulation state detection technology.
In engineering, a voltage withstand test is mainly used for evaluating the insulation state of the power equipment, however, some local non-penetrating defects cannot be found by the voltage withstand test, and the high voltage of the voltage withstand test can promote the local defects on the power equipment to be further developed and worsened, so that the case that the newly completed power equipment fails after being operated for a period of time with points is not rare.
Partial discharge is a main manifestation form of insulation failure of the power equipment in an early stage, and is a main cause of insulation aging and a main characteristic parameter for representing an insulation condition, so that the partial discharge detection is a typical method for detecting a non-penetrating defect of the power equipment. Compared with a withstand voltage test, the pressurization time of the partial discharge detection test is short, and the defect deterioration of the power equipment caused by continuous high voltage can be avoided.
For power equipment with large equivalent capacitance value of 110kV or above, the power frequency voltage withstanding method cannot be applied on site due to the limitation of power supply capacity, and the common alternative methods at present mainly comprise a direct current voltage method, a variable frequency alternating current voltage method, a 0.1Hz ultralow frequency voltage method and the like. However, the dc voltage may cause space charge accumulation in the power equipment, which results in the operating voltage of the power equipment after being put into use being higher than the rated voltage thereof, and thus the aging of the equipment is accelerated. The equivalence of using 0.1Hz ultralow frequency voltage to replace power frequency alternating current voltage is not good, and the validity of the detection result is yet to be researched. At present, the frequency modulation type series resonance method is most commonly used for generating voltage with the frequency range of 30-300Hz instead of power frequency alternating current voltage. The international large grid Conference (CIGRE)21-09 working group states in the 1997 report: the 30-300Hz alternating current withstand voltage test has good equivalence with power frequency withstand voltage, and the method is more effective as the withstand voltage test of high-voltage power equipment such as a crosslinked polyethylene cable than other methods.
For the field test of the power equipment with large equivalent capacitance value of 110kV and above, the test has higher requirement on the output power of the power supply, and currently, a diesel generator is generally adopted to provide energy for the test equipment. However, the quality of the electric energy generated by the diesel generator is low, the harmonic distortion rate is high, and the measurement sensitivity is seriously influenced particularly in a partial discharge detection test. And the diesel generator is large in size, heavy in mass and inconvenient to transport, and the test efficiency is influenced. In summary, there is a need for a new type of all-electric partial discharge detection apparatus and method for large capacity power equipment.
Disclosure of Invention
The invention aims to provide a full-electric partial discharge detection device and a detection method, and aims to solve the problems that a high-power supply is difficult to provide on site and the detection efficiency is low in the current detection test of power transmission equipment.
In order to achieve the purpose, the invention adopts the following technical scheme:
an all-electric type partial discharge detection apparatus comprising: the system comprises a high-voltage charging unit, a capacitor matrix unit, a voltage regulating unit, an inversion unit, a power electronic switch unit, an inductance matrix unit, a measuring unit and a host system; the output end of the high-voltage charging unit is connected with the input end of the capacitor matrix unit, and the high-voltage charging unit is used for providing electric energy for the capacitor matrix unit; the output end of the capacitor matrix unit is connected with the input end of the voltage regulating unit, and the output end of the voltage regulating unit is connected with the input end of the inversion unit; a power electronic switch unit is connected in parallel between the two output ends of the inversion unit; one output end of the inversion unit is grounded, and the other output end of the inversion unit is connected with the inductance matrix unit in series; the inductance matrix unit is used for connecting a tested product; the measuring unit is used for being connected in parallel at two ends of a tested product; the host system is connected with the control electrode of the switching device in each unit.
Further, the high-voltage charging unit comprises a battery pack, a charging protection resistor and a booster circuit; one end of the battery pack is connected with the charging protection resistor in series; the booster circuit realizes the direct current booster circuit by combining a voltage doubling circuit in a resonance mode, the output voltage amplitude of the direct current booster circuit is controlled by utilizing feedback regulation, and the output end of the booster circuit is the output end of the high-voltage charging unit; the battery pack is matched with the charging protection resistor, so that the peak value of the output current of the battery pack is less than or equal to 10A.
Further, the capacitance matrix unit includes: an overvoltage protection circuit and a capacitor; the overvoltage protection circuit is connected with the capacitor in parallel; wherein the volume of the capacitor is less than or equal to 0.5m3The mass is less than or equal to 25kg, and the instantaneous output power reaches more than 500 kVA.
Further, the inverter unit includes: an inverter circuit and a transformer; the inverter circuit controls the single-phase bridge inverter circuit in a square wave PWM modulation mode; the transformer adopts silicon steel sheet as magnetic core material, the frequency range is 0-400Hz, the transformation ratio is 220V:1000V, and the secondary side of the transformer is provided with a high-voltage arrester.
Further, the power electronic switching unit comprises: the power electronic switch circuit, the power supply circuit and the drive circuit; the power electronic switch circuit is formed by connecting a plurality of insulated gate bipolar transistors and buffer voltage-sharing protection circuits thereof in series; the power supply circuit adopts a flyback multi-output isolated power supply topological structure; the flyback multi-output isolated power supply topological structure consists of a primary side circuit and a secondary side circuit; each insulated gate bipolar transistor is provided with an independent secondary side circuit, and the primary side circuit and the secondary side circuit adopt a 'loose coupling' mode to transmit energy by using a magnetic field; the driving circuit uses the capacitor as an energy supply element, the power supply circuit charges the capacitor of the driving circuit, when the driving circuit drives the insulated gate bipolar transistor to be switched on, the power supply circuit is switched off, and only the capacitor supplies energy to the driving circuit.
Furthermore, the specific form that the primary side circuit and the secondary side circuit adopt a 'loose coupling' mode to transmit energy by utilizing a magnetic field is that a primary side circuit winding and a secondary side winding are both a conducting wire which passes through and bypasses a magnetic core, and one primary side circuit supplies energy to the secondary side circuits which are matched with all the insulated gate bipolar transistors.
Furthermore, the inductance matrix unit is formed by serially connecting inductors wound by a plurality of nanocrystalline magnetic rings, the total inductance is higher than or equal to 3H, the mass is less than or equal to 20KG, and a magnetic circuit is closed.
Further, the measuring unit includes: a partial discharge detection unit and a high voltage measurement unit; the coupling capacitor of the partial discharge detection unit and the high-voltage arm of the high-voltage measurement unit share one capacitor.
Further, the host system includes: an upper computer and a lower computer;
the lower computer main body is an FPGA and is used for providing control signals for each semiconductor switch device in the system;
the upper computer is a portable computer and stores a human-computer interaction interface, partial discharge positioning software and a resonant frequency algorithm;
the resonant frequency algorithm is characterized in that an inverter unit outputs a pulse width of 1ms and a voltage of UCThe peak value of the response voltage on the capacitive test article is measured to be Uo(ii) a The capacitance is calculated by the formula as,
in the formula, L is the inductance value of the inductance matrix unit, R is the equivalent series resistance value of the inductance matrix unit, and k is the transformation ratio of the transformer contained in the inverter unit;
the expression for calculating the resonance frequency f is,
wherein C is the capacitance of the sample, and L is the inductance of the inductance matrix unit.
A full-electric partial discharge detection method comprises the following steps:
charging, namely charging the capacitor stack of the capacitor matrix unit to a preset voltage value through the high-voltage charging unit, cutting off the high-voltage charging unit, and providing electric energy for the rear electrode circuit through the voltage regulating circuit by utilizing the charged capacitor stack of the capacitor matrix unit;
calculating resonance frequency, outputting a square wave with a preset time duration and an amplitude value of the preset voltage value by using an inverter unit, and measuring to obtain a response waveform peak value U on the tested productoCalculating to obtain the resonant frequency f of the tested product and the inductance matrix unit;
pressurizing, namely outputting a voltage wave of the resonant frequency by using the inverter unit to enable the tested product and the inductance matrix unit to be in a resonant state; changing the amplitude of the output voltage wave through the voltage regulating unit to enable the voltage on the tested object to reach a preset amplitude;
and oscillating, turning off the inversion unit, turning on the power electronic switch unit, enabling the tested object and the inductance matrix unit to enter an underdamped oscillation state, and detecting a partial discharge signal through the measuring unit.
Compared with the prior art, the invention has the following beneficial effects:
the invention is provided with the high-voltage charging unit and the capacitor matrix unit, the capacitor stack of the capacitor matrix unit has strong instantaneous power output capability, and the capacitor stack is utilized to supply energy to equipment without an additional high-power supply. The invention utilizes the oscillatory wave technology based on the frequency modulation type series resonance principle, can complete the partial discharge detection of the power transmission equipment to be detected in a short time through the inversion unit, the power electronic switch unit, the inductance matrix unit and the measurement unit, and can improve the detection efficiency. The invention can improve the efficiency of the field test and the detection precision of the partial discharge, and has important practical value in engineering.
Furthermore, the invention utilizes the battery pack to charge the capacitor stack, utilizes the capacitor stack to supply energy to the equipment, combines the advantages of large energy storage capacity of the battery pack and strong instantaneous output power capacity of the capacitor stack, and can solve the problem that a high-power supply is difficult to provide in a field test of power transmission equipment. The characteristics of no switching noise output and capability of outputting short-time high power output of the capacitor matrix are utilized to replace the current common diesel generator, and the noise from a power supply end during partial discharge measurement can be effectively reduced.
Furthermore, the transformer adopts a special silicon steel sheet as a magnetic core material, the frequency range of the transformer is 0-400Hz, the transformation ratio is 220V:1000V, high-frequency switching noise caused by the action of the inverter can be filtered, and the harmonic rate of secondary side output voltage of the transformer is reduced. The secondary side of the transformer is provided with a high-voltage arrester, so that the damage to the detection device caused by overvoltage and overcurrent after flowing through the transformer due to the fault of the tested equipment or the action of a power electronic switch in the measurement is avoided.
Furthermore, the power electronic switch circuit is formed by connecting a plurality of Insulated Gate Bipolar Transistors (IGBTs) and a buffer voltage-sharing protection circuit in series, so that the problem of uneven voltage division caused by the dispersity of the turn-off resistance of the IGBTs is solved. When overvoltage which can damage the series IGBT appears at two ends of the power electronic switch circuit, the protection circuit acts to release overshoot energy, and the detection device is guaranteed not to be damaged; and the capacitance energy storage element is adopted to drive the IGBT to be switched on, so that interference signals introduced by IGBT driving signals are reduced. A loose coupling flyback multi-output isolation power supply topological structure is adopted to provide the IGBT driving circuit with functions, and the electrical isolation of the high-voltage circuit and the low-voltage circuit is achieved.
Furthermore, the primary side circuit winding and the secondary side winding are both a lead which passes through and bypasses the magnetic core, and one primary side circuit has the function of a secondary side circuit which is matched with all IGBTs. The circuit structure ensures the electrical isolation of each IGBT power supply circuit, and can effectively avoid all devices from being damaged due to overvoltage on a single device.
Furthermore, the inductance matrix unit is formed by connecting a plurality of annular iron core inductors with air gaps in series and parallel, a magnetic circuit is closed, the total turn-to-turn capacitance of the reactor can be reduced, and the sensitivity of partial discharge detection is increased; meanwhile, the control and measurement circuit can be prevented from being interfered by the leakage of electromagnetic wave radiation in the oscillation process.
The method of the invention utilizes the oscillatory wave technology based on the frequency modulation type series resonance principle to complete the partial discharge detection of the power transmission equipment in a short time, thereby improving the detection efficiency.
Drawings
FIG. 1 is a schematic structural diagram of an all-electric partial discharge detector according to the present invention;
FIG. 2 is a schematic diagram of the IGBT power supply circuit and the driving circuit in the embodiment of the invention;
FIG. 3 is a schematic diagram of a "loose coupling" connection in an embodiment of the present invention;
FIG. 4 is a schematic diagram of the high voltage waveform output by the apparatus of the present invention during operation;
in fig. 1, a high-voltage charging unit 11; a capacitance matrix unit 12; a voltage regulating unit 13; an inverter unit 14; a power electronic switching unit 15; an inductance matrix unit 16; the test object 17; a measuring unit 18; a host system 19.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples.
Referring to fig. 1, an all-electric partial discharge detection apparatus according to the present invention includes: the system comprises a high-voltage charging unit 11, a capacitor matrix unit 12, a voltage regulating unit 13, an inverter unit 14, a power electronic switch unit 15, an inductance matrix unit 16, a measuring unit 18 and a host system 19. The output end of the high-voltage charging unit 11 is connected with the input end of the capacitor matrix unit 12 to provide energy for the capacitor matrix unit 12. The output end of the capacitor matrix unit 12 is connected with the input end of the voltage regulating unit 13, and the output end of the voltage regulating unit 13 is connected with the input end of the inversion unit 14. A power electronic switch unit 15 is connected in parallel between two output ends of the inversion unit 14, one output end is grounded, and the other output end is connected with the tested object 17 after being connected with the inductance matrix unit 16 in series. The measuring unit 18 is connected in parallel across the test object 17. The host system 19 is connected to the control electrodes of the switching devices in each cell.
The high-voltage charging unit 11 consists of a battery pack, a charging protection resistor and a boosting circuit; the battery pack is matched with the charging protection resistor, so that the peak value of the output current of the battery pack is ensured to be less than 10A, and the battery pack is prevented from being damaged due to larger output power; and the booster circuit realizes a small-sized direct current booster circuit by combining a voltage doubling circuit in a resonance mode, and controls the amplitude of the output voltage of the direct current booster circuit by utilizing feedback regulation. For example, the voltage boost circuit is a conventional voltage doubler circuit.
The capacitor matrix unit 12 is connected in parallel with the low-voltage ends of the high-voltage charging unit 11 and the voltage regulating unit 13, the capacitor matrix unit 12 is formed by connecting an overvoltage protection circuit and a large-capacity capacitor in parallel, the capacity value of the capacitor depends on the equivalent capacity value of the tested object 17, the capacitor matrix unit is generally formed by connecting more than 50 large-capacity electrolytic capacitors with 4700 mu F and withstand voltage of 450V in parallel, and the volume of the capacitor matrix unit is not more than 0.5m3The mass is not more than 25kg, the instantaneous output power can reach 500kVA or more, and higher power can be easily obtained according to actual requirements.
And the voltage regulating unit 13 combines a feedback control technology, a resonance technology and a full-bridge rectification technology to realize high-efficiency and high-precision direct current voltage regulation.
The inverter unit 14 is composed of an inverter circuit and a transformer. The inverter circuit controls the single-phase bridge inverter circuit by using a square wave PWM modulation mode, so that the action times of the inverter in each modulation period can be reduced, and the harmonic rate of output voltage is reduced. The transformer adopts a special silicon steel sheet as a magnetic core material, the frequency range is 0-400Hz, the transformation ratio is 220V:1000V, high-frequency switching noise caused by the action of the inverter can be filtered, and the harmonic rate of the secondary side output voltage of the transformer is reduced. The secondary side of the transformer is provided with a high-voltage arrester, so that the damage to the detection device caused by overvoltage and overcurrent after flowing through the transformer due to the fault of the tested equipment or the action of a power electronic switch in the measurement is avoided.
The power electronic switching unit 15 is composed of a power electronic switching circuit, a power supply circuit, and a drive circuit. The power electronic switch circuit is formed by connecting a plurality of Insulated Gate Bipolar Transistors (IGBTs) and a buffer voltage-sharing protection circuit in series, and the problem of uneven voltage division caused by dispersity of the turn-off resistance of the IGBTs is solved. When overvoltage which can damage the series IGBT appears at two ends of the power electronic switch circuit, the protection circuit acts to release overshoot energy, and the detection device is guaranteed not to be damaged. The power supply circuit adopts a flyback multi-output isolated power supply topological structure, and the flyback multi-output isolated power supply topological structure consists of a primary side circuit and a secondary side circuit.
Referring to fig. 2 and fig. 3, each IGBT is provided with a separate secondary side circuit to supply power to its driving circuit, and the primary side circuit and the secondary side circuit use a "loose coupling" method to transfer energy by using a magnetic field, which is embodied in that the primary side circuit winding and the secondary side winding are both a wire passing through a magnetic core, and a primary side circuit provides the secondary side circuit function for all IGBTs. The circuit structure ensures the electrical isolation of each IGBT power supply circuit, and can effectively avoid all devices from being damaged due to overvoltage on a single device. And the driving circuit uses the capacitor as a functional element, the power supply circuit charges the capacitor, when the circuit drives the IGBT to be switched on, the power supply circuit is switched off, and only the capacitor supplies energy to the driving circuit. The electric energy provided by the capacitor is pure, the harmonic distortion rate is low, and interference signals introduced by IGBT driving signals are greatly reduced.
The inductance matrix unit 16 is formed by serially connecting inductors wound by a plurality of nanocrystalline magnetic rings, the total inductance is not lower than 3H, the mass is not more than 20KG, a magnetic circuit is closed, and the phenomenon that periodically-changed current radiates a periodically-changed strong magnetic field to the surrounding space through the inductors in the working process of the device to interfere the normal work of an equipment control system and a measurement system is avoided; in addition, the magnetic circuit is closed, so that electromagnetic interference caused by resonance can be reduced.
The measuring unit 18 is composed of a partial discharge detecting unit and a high voltage measuring unit, wherein a coupling capacitor of the partial discharge detecting unit and a high voltage arm of the high voltage measuring unit share one capacitor, and a high voltage non-partial discharge capacitor with withstand voltage of 60kV and a capacitance value of 2 muF is adopted.
The host system 19 comprises an upper computer and a lower computer, wherein the lower computer main body is an FPGA and provides control signals for each semiconductor switch device in the system; the upper computer is a portable computer and mainly comprises a human-computer interaction interface, partial discharge positioning software, a resonant frequency algorithm and the like.
The resonant frequency algorithm outputs a pulse width of 1ms and a voltage of U through an inverter circuit contained in an inverter unitCThe peak value of the response voltage on the capacitive test article can be measured to be Uo. The capacitance calculation formula is shown as formula 1, wherein L is an inductance value of the inductance matrix unit, R is an equivalent series resistance value of the inductance matrix unit, and k is a transformation ratio of a transformer included in the inverter circuit. The resonant frequency f can be calculated according to the formula 2 by using the capacitance value C of the test sample and the inductance value of the inductance matrix unit.
The invention is improved on the basis of the principle of a frequency modulation type series resonance test, so that the invention is suitable for a partial discharge detection test of power equipment; the characteristics of strong short-time power output capability and low harmonic rate of output voltage waveform of the capacitor matrix module are utilized, so that the problem that a high-power low-noise power supply is difficult to provide during field test of large-equivalent capacitance value power equipment with the voltage of 110kV or above is solved; the isolation of the high-voltage switch and the control circuit is realized by utilizing a flyback multi-output isolated power supply topological structure in loose coupling; the modularized inductance matrix unit is used for realizing the magnetic circuit sealing of the reactor, so that the weight of the equipment is greatly reduced while the partial discharge detection precision is improved. Through the scheme, the efficiency of the field test of the power equipment with the large equivalent capacitance value of the voltage of 110kV or more and the detection precision of partial discharge are improved, and the method has important practical value in engineering. The invention can be applied to the partial discharge detection device of high-capacity capacitive high-voltage power equipment such as cables, generators and the like. The detection device of the invention is powered by the built-in battery pack, and can save external high-power supplies such as a generator and the like during field measurement, improve the noise resistance of the equipment and realize the electrical isolation of high-voltage and low-voltage parts. The invention can improve the technical level of the related field and has wide application prospect.
The invention relates to a using method, namely a detection method, of a full-electric partial discharge detection device for large-capacity capacitive power equipment, which mainly comprises the following 4 steps:
charging: and starting the battery pack to charge the capacitor stack to 700V, cutting off the battery pack, and providing electric energy for the rear electrode circuit by using the capacitor stack through the voltage regulating circuit.
Calculating the resonance frequency: an inverter circuit is utilized to output a square wave with the duration of 1ms and the amplitude of 700V, and the peak value of the response waveform on the capacitive test article is U through measurementoThe resonant frequency f between the capacitive sample and the inductance matrix unit 16 is calculated by using the above equations 1 and 2.
Pressurizing: and the inverter circuit is used for outputting voltage waves of the resonant frequency, so that the tested object and the inductance matrix unit are in a resonant state. The amplitude of the output voltage wave is changed through the voltage regulating unit, so that the voltage on the tested object reaches the preset amplitude. The voltage waveform across the test article at this stage is shown in the resonant stressed state in fig. 4.
Oscillating: and switching off the inverter circuit, switching on the power electronic switch unit, enabling the tested object and the inductance matrix unit to enter an underdamped oscillation state, and detecting a partial discharge signal through the measuring unit. The voltage waveform across the test article at this stage is shown in the ringing state in fig. 4.
Examples
The invention relates to a full-electric partial discharge detection device, which comprises: the high-voltage charging system comprises a high-voltage charging unit, a capacitor matrix unit, a voltage regulating unit, an inversion unit, a power electronic switch unit, an inductance matrix unit, a measuring unit and a host system. The output end of the high-voltage charging unit is connected with the input end of the capacitor matrix unit to provide energy for the capacitor matrix unit. The output end of the capacitor matrix unit is connected with the input end of the voltage regulating unit, and the output end of the voltage regulating unit is connected with the input end of the inversion unit. And a power electronic switch unit is connected between the two output ends of the inversion unit in parallel, one output end is grounded, and the other output end is connected with the tested object after being connected with the inductance matrix unit in series. The measuring units are connected in parallel at two ends of the tested object. The host system is connected with the control electrode of the switching device in each unit. The power electronic switch unit is formed by reversely connecting two IGBTs in series in a common emitter mode, and on-off control is carried out by adopting the loose coupling isolation power supply mode. And the collectors of the two series-connected IGBTs are respectively connected with two ends of the high-voltage side of the transformer in the inversion unit. The inductance matrix unit is formed by connecting a plurality of inductors in series, and the capacitance matrix unit is formed by connecting a plurality of capacitors in parallel.
In summary, the present invention is a full-electric partial discharge detection device for large-capacity capacitive power equipment. The device comprises a high-voltage charging unit, a capacitor matrix unit, a voltage regulating unit, an inversion unit, a power electronic switch unit, an inductance matrix unit, a measuring unit and a host system, and can apply oscillating wave voltage with the peak value of 250kV at most and the frequency range of 30-500Hz to the tested power equipment. Experiments show that the insulation characteristics of the power equipment are similar to those of the power frequency under the action of the oscillating wave voltage with the frequency within the range of 30-500Hz, so that the oscillating wave voltage can simulate the power frequency alternating current high voltage to carry out off-line detection tests on various high-capacity capacitive power equipment including cables, large generators and the like, the test effectiveness is ensured, and the requirements of the tests on the power supply capacity are reduced. The invention utilizes the characteristics of no switching noise output and short-time high power output of the capacitor matrix to replace the currently common diesel generator, and effectively reduces the noise from a power supply end during partial discharge measurement. After the power equipment is boosted to a preset value by using a frequency modulation type series resonance technology, the power electronic switch unit is closed to generate oscillation waves. The power electronic switch unit adopts a flyback isolation power supply, and the power supply unit is not electrically connected with the main circuit, so that the influence of noise at the power end is reduced, and the safety of equipment is improved. The inductance matrix is formed by connecting a plurality of reactors with closed magnetic circuits in series, the closed magnetic circuits limit the radiation range of an electromagnetic field in the oscillation process, and the interference of oscillation current on the control of the measuring unit and the power electronic switch is greatly reduced. The full-electric partial discharge detection device can evaluate the insulation state of electric equipment such as cables and the like, solves the problem that the current electric equipment offline detection device with the voltage level of 110kV and above depends on a high-power supply, greatly reduces noise interference, improves measurement precision, greatly reduces the volume and weight of test equipment, is convenient for field carrying and installation, and has important engineering practical value.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and those skilled in the art can make various modifications, equivalent changes and modifications within the scope of the present invention by using the above disclosed technical contents.
Claims (8)
1. An all-electric partial discharge detection device, comprising: the device comprises a high-voltage charging unit (11), a capacitor matrix unit (12), a voltage regulating unit (13), an inversion unit (14), a power electronic switch unit (15), an inductance matrix unit (16), a measuring unit (18) and a host system (19);
the output end of the high-voltage charging unit (11) is connected with the input end of the capacitor matrix unit (12), and the high-voltage charging unit (11) is used for providing energy for the capacitor matrix unit (12); the output end of the capacitor matrix unit (12) is connected with the input end of the voltage regulating unit (13), and the output end of the voltage regulating unit (13) is connected with the input end of the inversion unit (14); a power electronic switch unit (15) is connected in parallel between the two output ends of the inversion unit (14); one output end of the inversion unit (14) is grounded, and the other output end is connected with the inductance matrix unit (16) in series; the inductance matrix unit (16) is used for connecting a tested object (17); the measuring unit (18) is used for being connected in parallel at two ends of the tested object (17); the host system (19) is connected with the control electrode of the switching device in each unit;
the power electronic switch unit (15) comprises: the power electronic switch circuit, the power supply circuit and the drive circuit;
the power electronic switch circuit is formed by connecting a plurality of insulated gate bipolar transistors and buffer voltage-sharing protection circuits thereof in series;
the power supply circuit adopts a flyback multi-output isolated power supply topological structure; the flyback multi-output isolated power supply topological structure consists of a primary side circuit and a secondary side circuit; each insulated gate bipolar transistor is provided with an independent secondary side circuit, and the primary side circuit and the secondary side circuit adopt a 'loose coupling' mode to transmit energy by using a magnetic field; the driving circuit uses a capacitor as an energy supply element, the power supply circuit charges the capacitor of the driving circuit, when the driving circuit drives the insulated gate bipolar transistor to be switched on, the power supply circuit is switched off, and only the capacitor supplies energy to the driving circuit;
the primary side circuit and the secondary side circuit adopt a 'loose coupling' mode to transmit energy by utilizing a magnetic field in a specific form that a primary side circuit winding and a secondary side winding are both a conducting wire which passes through a magnetic core in a penetrating mode, and one primary side circuit supplies energy to the secondary side circuits matched with all insulated gate bipolar transistors.
2. An all-electric partial discharge detection device according to claim 1, wherein the high-voltage charging unit (11) comprises a battery pack, a charge protection resistor and a booster circuit;
one end of the battery pack is connected with the charging protection resistor in series;
the booster circuit realizes the direct current booster circuit by combining a voltage doubling circuit in a resonance mode, and controls the output voltage amplitude of the direct current booster circuit by utilizing feedback regulation;
the battery pack is matched with the charging protection resistor, so that the peak value of the output current of the battery pack is less than or equal to 10A.
3. An all-electric partial discharge detection device according to claim 1, wherein the capacitance matrix unit (12) comprises: an overvoltage protection circuit and a capacitor; the overvoltage protection circuit is connected with the capacitor in parallel;
wherein the volume of the capacitor is less than or equal to 0.5m3The mass is less than or equal to 25kg, and the instantaneous output power reaches more than 500 kVA.
4. An all-electric partial discharge detection device according to claim 1, wherein the inverter unit (14) comprises: an inverter circuit and a transformer;
the inverter circuit controls the single-phase bridge inverter circuit in a square wave PWM modulation mode; the transformer adopts silicon steel sheet as magnetic core material, the frequency range is 0-400Hz, the transformation ratio is 220V:1000V, and the secondary side of the transformer is provided with a high-voltage arrester.
5. The all-electric partial discharge detector according to claim 1, wherein the inductor matrix unit (16) is formed by connecting inductors wound by a plurality of nanocrystalline magnetic rings in series, the total inductance is higher than or equal to 3H, the mass is less than or equal to 20KG, and the magnetic circuit is closed.
6. An all-electric partial discharge detection device according to claim 1, characterized in that the measuring unit (18) comprises: a partial discharge detection unit and a high voltage measurement unit; the coupling capacitor of the partial discharge detection unit and the high-voltage arm of the high-voltage measurement unit share one capacitor.
7. An all-electric partial discharge detection device according to claim 1, characterized in that the host system (19) comprises: an upper computer and a lower computer;
the lower computer main body is an FPGA and is used for providing control signals for each semiconductor switch device in the full-electric partial discharge detection device;
the upper computer is a portable computer and stores a human-computer interaction interface, partial discharge positioning software and a resonant frequency algorithm;
the resonant frequency algorithm is characterized in that an inverter unit outputs a pulse width of 1ms and a voltage of UCThe peak value of the response voltage on the capacitive test article is measured to be Uo(ii) a The capacitance is calculated by the formula as,
in the formula, L is the inductance value of the inductance matrix unit, R is the equivalent series resistance value of the inductance matrix unit, and k is the transformation ratio of the transformer contained in the inverter unit;
the expression for calculating the resonance frequency f is,
wherein C is the capacitance of the sample, and L is the inductance of the inductance matrix unit.
8. An all-electric partial discharge detection method, based on the detection device of any one of claims 1 to 7, comprising the steps of:
charging, namely charging the capacitor matrix unit (12) to a preset voltage value through the high-voltage charging unit (11), cutting off the high-voltage charging unit (11), and providing electric energy for the inverter unit (14) through the voltage regulating unit (13) by utilizing the charged capacitor matrix unit (12);
calculating resonance frequency, outputting a square wave which lasts for preset time and has amplitude of the preset voltage value by using an inverter unit (14), and measuring to obtain a response voltage peak value U on the tested product (17)oCalculating and obtaining the resonant frequency f of the tested object (17) and the inductance matrix unit (16);
pressurizing, namely outputting a resonant frequency voltage wave by using the inverter unit (14) to enable the tested object (17) and the inductance matrix unit (16) to be in a resonant state; the amplitude of the resonant frequency voltage wave is changed through the voltage regulating unit (13), so that the voltage on the tested object (17) reaches a preset amplitude;
and oscillating, turning off the inverter unit (14), turning on the power electronic switch unit (15), enabling the tested object (17) and the inductance matrix unit (16) to enter an underdamped oscillation state, and detecting a partial discharge signal through the measuring unit (18).
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| CN109901034B (en) * | 2019-04-02 | 2020-12-01 | 国网陕西省电力公司电力科学研究院 | Power cable partial discharge detection device and evaluation method based on multi-stage power supply and series resonance |
| CN110879337A (en) * | 2019-11-06 | 2020-03-13 | 广州供电局有限公司 | Oscillating wave voltage generating circuit and cable partial discharge detection device |
| DE102020214614B3 (en) * | 2019-12-06 | 2021-05-06 | Gunter Kries | Circuit arrangement for voltage testing and partial discharge detection |
| CN110907781B (en) * | 2019-12-30 | 2021-01-05 | 华北电力大学 | High-frequency transformer insulation test system and use method thereof |
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