CN111693802A - Frequency-adjustable cosine square wave voltage generation device and method - Google Patents
Frequency-adjustable cosine square wave voltage generation device and method Download PDFInfo
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- CN111693802A CN111693802A CN202010441972.XA CN202010441972A CN111693802A CN 111693802 A CN111693802 A CN 111693802A CN 202010441972 A CN202010441972 A CN 202010441972A CN 111693802 A CN111693802 A CN 111693802A
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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
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M13/00—Testing of machine parts
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
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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
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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
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Abstract
The invention relates to a frequency-adjustable cosine square wave voltage generating device which comprises a bottom plate, an inductance supporting column arranged on the bottom plate, a control unit, an isolating switch and a control panel, wherein an inductor is arranged at the top end of the inductance supporting column, a positive polarity direct current source and a frequency-adjustable positive polarity switch are fixed at the top of the control unit, a negative polarity direct current source is fixedly connected to the positive polarity direct current source, a frequency-adjustable negative polarity switch is fixedly connected to the frequency-adjustable positive polarity switch, and a voltage divider and a coupling capacitor are fixedly connected to the outer side of the inductor. The frequency of the invention is adjustable, and a more compact structure is adopted, so that the breakdown and creepage voltage in the direct current charging process are improved; the insulating property and the safety performance of the cable are enhanced by adopting an automatic discharging mode.
Description
Technical Field
The invention belongs to the field of safe operation of distribution cables, and particularly relates to a cosine square wave voltage generating device and method with adjustable frequency.
Background
The cause of the power cable fault can be summarized as follows:
(A) aging and deterioration of an insulating medium: due to the long-term continuous work of the power cable, the external insulating material of the cable can be changed to a certain extent, and meanwhile, the insulating capability of the cable can be seriously reduced due to the influence of external factors.
(B) Insulating medium is affected with damp: due to the quality problem and the installation technical problem of the joint of the power cable, the joint of the power cable is usually not sealed, so that the joint of the cable is often affected with damp. Meanwhile, the cable line has certain defects, and the insulating medium of the cable is very easily influenced by environmental factors, so that the cable cannot be normally used.
(C) Cable overheating: when the power cable line is laid underground, the air gap inside the insulating medium of the cable is often free, and the problem of local serious overheating of the power cable is caused. Once local line overheating occurs to the power cable, the external insulation of the line is easily aged, so that the external insulation effect of the power cable is reduced.
(D) Causes of mechanical damage: in the process of the practical use of the power cable, the damage of the power cable caused by some external factors often occurs. The joint or the insulation of the power cable is damaged, so that the normal use of the power cable is influenced. In general, the damage of the power cable mainly includes the reasons of construction external damage, external environment, and the like.
(E) The material has the following defects: in the manufacturing process of the power cable, the manufacturing materials are not standardized, and the constructor does not perform finished product inspection on the power cable in the construction process, so that the power cable has the phenomenon of external insulator defect. Meanwhile, the cable needs some parts for assistance when being connected, and the parts do not meet the quality requirement when being processed, so that poor contact occurs in the later period, and the power cable breaks down.
Crosslinked polyethylene (XLPE) cables have become the mainstream of urban power transmission and distribution networks due to the advantages of excellent insulating property, easiness in manufacturing, simplicity in installation and laying, safety and reliability in power supply, small workload in operation and maintenance and the like. However, due to the harsh operating environment of the distribution cable, periodic tests are required to determine the operational reliability thereof.
Major accidents of domestic and foreign power grids are caused by cable defects, which causes huge economic loss and adverse social influence. The effective detection of the cable has important significance for preventing cable accidents and improving the reliability of a power grid. At present, three main tests of cable detection are voltage-withstanding test, dielectric loss measurement and partial discharge measurement, different devices are needed for testing, efficiency is low, and time consumption is long. Available test methods mainly include a resonance method, a direct current method, an oscillation wave method and an ultra-low frequency method. The direct current method is mainly applied to the withstand voltage test of the oil-filled cable, and is not suitable for the detection of the crosslinked polyethylene cable due to the accumulation of space charges. The oscillating voltage method is effective for partial discharge detection and can also be used for measuring dielectric loss, but cannot be used for withstand voltage test and is insensitive to defects such as water trees. The resonance method can meet the pressure-resistant requirement, but because the equipment has large volume and high price, the resonance method is difficult to popularize in the pressure-resistant test of the crosslinked polyethylene cable. The 0.1Hz ultralow frequency test method can simultaneously meet the requirements of withstand voltage, dielectric loss and partial discharge tests, is sensitive to defects such as water trees and the like, and is a medium and low voltage crosslinked polyethylene power cable withstand voltage test technology recommended by the International Electrotechnical Commission (IEC). The voltage-resistant and dielectric loss detection device for the cable is developed based on the ultralow frequency technology, and has important significance for guaranteeing the power supply reliability of the cable, shortening the test time and improving the test efficiency.
The withstand voltage test of the cable is an important means for checking the insulating property of the cable, the cosine square wave voltage is a standard waveform of the withstand voltage test, the traditional frequency is 0.1Hz and is not adjustable, the detection time for defects such as water trees is long, and the efficiency is low. The growth and breakdown of water trees is affected by the frequency of the electric field, and as the frequency increases, the breakdown time decreases.
Disclosure of Invention
In order to overcome the defects of the existing 0.1Hz cosine square wave voltage generation method and device and comprehensively consider factors such as experiment time, convenience, investment time, economy and the like, the invention provides the frequency-adjustable cosine square wave voltage generation method and device, which starts from the long voltage withstanding time with non-adjustable frequency and improves the traditional cosine square wave voltage generation method and device with the frequency of 0.1 Hz. The detection effect is more economical, efficient, reliable and stable.
The invention adopts the following technical scheme:
a cosine square wave voltage generating device with adjustable frequency comprises a bottom plate, an inductance supporting column arranged on the bottom plate, a control unit, an isolating switch and a control panel, wherein an inductor is arranged at the top end of the inductance supporting column; the two ends of the frequency-adjustable positive switch and the frequency-adjustable negative switch which are connected in series are connected in parallel to the two ends of the isolating switch and the positive direct-current source; and the negative direct current source is connected in parallel at two ends of the frequency-adjustable negative switch.
The inductor, the top of the isolating switch and the top of the negative polarity switch are electrically connected through a corrugated pipe, a wire outlet end at the bottom of the positive polarity switch is connected with a device ground, the bottom of the isolating switch and a positive polarity direct current source are electrically connected through screw fastening, a high-voltage wire outlet end of the negative polarity direct current source is fixed through screws by leading out electrodes at the middle parts of the positive polarity switch and the negative polarity switch, and a voltage divider and a coupling capacitor are fixedly connected to the outer side of the inductor through screws to achieve the electrical connection and fixing.
The voltage divider is used for measuring the voltage of the cable to be measured, and the coupling capacitor is used for measuring the partial discharge of the cable to be measured.
Further, the inductor and the tested resistor form an L-C circuit.
Furthermore, the inductance support column is made of an insulating material.
Furthermore, a no-corona outgoing line is adopted below the inductor.
Further, the frequency-adjustable positive polarity switch and the frequency-adjustable negative polarity switch are connected in series.
Further, the voltage divider is connected in parallel with the coupling capacitor.
Furthermore, casters are arranged below the bottom plate.
Further, the inductor also comprises an outer shielding box, and the interval between the inductor and the outer shielding box is more than 5 cm.
A frequency-adjustable cosine square wave voltage generation method utilizes the frequency-adjustable cosine square wave voltage generation device, and a control unit controls and outputs a positive-polarity withstand voltage waveform, a negative-polarity withstand voltage waveform, a positive-polarity oscillation waveform and a negative-polarity oscillation waveform.
In the frequency-adjustable cosine square wave voltage generation method, the control unit controls and outputs a positive polarity oscillation waveform and a negative polarity oscillation waveform.
The invention has the beneficial effects that: the frequency of the invention is adjustable, and a more compact structure is adopted, so that the breakdown and creepage voltage in the direct current charging process are improved; the automatic discharging mode is adopted, so that the insulating property and the safety performance of the cable are enhanced. The device can be used for detecting serious water trees, electric trees, connector quality problems, mechanical damage, internal defects of cable insulation and the like. The cosine square wave voltage generating method and device with adjustable frequency are simple in structure, good in economical efficiency, higher in reliability and more comprehensive in function.
Drawings
FIG. 1 is a schematic diagram of the apparatus of the present invention.
Fig. 2 is a schematic diagram of the hardware structure of the present invention.
Fig. 3 is a right side view of fig. 2.
Wherein: the device comprises a caster 1, a bottom plate 2, a panel 3, a positive polarity direct current source 4, a negative polarity direct current source 5, a control unit 6, a frequency-adjustable positive polarity switch 7, a frequency-adjustable negative polarity switch 8, an inductance support column 9, an inductance 10, a voltage divider 11, a coupling capacitor 12 and an isolation switch 13.
FIG. 4 is a waveform diagram of the output of the apparatus of the present invention.
Fig. 5 is a graph of the voltage waveform of the tank circuit corresponding to process 3 in fig. 4.
Fig. 6 is a graph of the voltage waveform of the tank circuit corresponding to process 5 in fig. 4.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the application, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, but the present application may be practiced in other ways than those described herein, and it will be apparent to those of ordinary skill in the art that the present application is not limited to the specific embodiments disclosed below.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The invention provides a frequency-adjustable cosine square wave voltage generating method and device, and aims to provide a frequency-adjustable cosine square wave voltage generating device to realize rapid detection of the performance of a cable.
The device principle is as follows: the cable was pressurized to a test voltage of 3U 0. After 0.5-5 seconds, the charge stored in the cable is discharged through a change-over switch, and the discharging process is actually to charge an L-C circuit (consisting of the tested cable, a capacitor and an inductor), and then the cosine oscillation function of the L-C circuit enables all the stored energy to reversely charge the cable with opposite polarity. The switching slope is similar to a 50Hz sine wave and has a similar effect to the 50Hz test.
The energy loss in the process is very small, and only a little supplementary charging is needed in each period. Therefore, compared with the common alternating voltage test or sine ultralow frequency test method, the method requires a very small and light high-voltage power supply and test equipment. Has very important reference value for further popularizing new technology.
For the convenience of field test, an integrated structure is adopted in design, frequency-adjustable ultralow frequency equipment is taken as a whole, a voltage division structure from top to bottom is formed in the L-C energy interaction process in the polarity conversion process, the voltage division structure refers to that an inductor winding mode adopts a sectional type mode of dividing the inductor into 4 sections from top to bottom, epoxy casting and the like, a switch vertical structure, a voltage divider coupling capacitor placing position and a wire outlet end are adopted, a specific physical placing position is given as shown in figure 2, and the position placing and the switch, the inductor, the coupling capacitor and the voltage division resistor are designed to form a structure with the voltage division from top to bottom layer by layer. In order to improve the breakdown and creepage voltage in the direct current charging process, the breakdown voltage refers to the distance between a high-voltage end and the ground, and the ground short circuit phenomenon caused by the existence of sharp objects around the high-voltage end, and the creepage voltage refers to the ground short circuit phenomenon of the voltage along the air or an insulating support surface, so that the insulating distance from the bottom of an inductor to a shielding box is increased.
The insulating support rod and the top plate around the inductor are far away from the inductor as far as possible, and are at least 5cm away from the inductor, and the parameters are reasonably designed and meet the requirements of an oscillatory wave system and an ultralow frequency system; finally, an electrical outlet and a switch are arranged below the inductor, and a connector which is not easy to generate corona, such as a circular electrode, a round cap screw, a corrugated pipe and the like, is adopted below the inductor to reduce corona during direct-current charging. The switch is preferably placed at the front end of the inductor, namely a physical position and an electrical position, the electric field intensity at the bottom of the inductor is high, and the switch is placed right below the inductor to increase the attenuation of the oscillating wave so as to reduce the influence of a strong magnetic field and an electric field of the inductor on the conduction and partial discharge of the switch.
The free adjustment of the cosine square wave frequency in the range of 0.1Hz-1Hz is realized by controlling the conduction time of the polarity conversion switch through software and matched hardware.
A block diagram of a frequency-adjustable cosine square wave voltage generating apparatus of the present invention is shown in fig. 1, and includes: the circuit comprises a non-partial discharge inductor L, an isolating switch, a polarity conversion switch (comprising a positive polarity switch and a negative polarity switch), a positive polarity direct current source and a negative polarity direct current source. The positive polarity direct current source is fixedly connected with a negative polarity direct current source, the frequency-adjustable positive polarity switch is fixedly connected with a frequency-adjustable negative polarity switch, and the inductor, the tested cable, the positive polarity direct current source and the isolating switch are connected in series; two ends of the positive switch and the negative switch after being connected in series are connected in parallel at two ends of the isolating switch and the positive direct current source; and the negative polarity direct current source is connected in parallel at two ends of the negative polarity switch.
In connection with the modular connection of fig. 1, the hardware mounting arrangement of the present invention is shown in fig. 2 and 3. 4 casters 1 are connected to a bottom plate 2 by screws for supporting, a front panel 3 is fixed at the middle of the edge of the bottom plate 2 by screws, a control unit 6 is fixed at the center of the upper part of the bottom plate 2 by screws, a positive polarity direct current source 4 is arranged at the upper left part of the control unit 6 and is fixed on the bottom plate 2 by screws, a negative polarity direct current source 5 is arranged at the upper part of the positive polarity direct current source 4 and is fixed on the positive polarity direct current source 4 by screws, a positive polarity switch 7 with adjustable frequency is arranged at the upper left part of the control unit 6, a negative polarity switch 8 with adjustable frequency is fixed at the upper part of the positive polarity switch 7 by screws, the positive polarity switch 7 and the negative polarity switch 8 are internally connected by flexible wires for electrical connection, the positive polarity direct current source 4, the negative polarity direct current source 5 and the negative polarity switch 8 are electrically connected to the bottom, the voltage divider 11 and the coupling capacitor 12 are electrically connected in parallel and fixed on the upper surface of the inductor by screws.
The inductor 10, the top of the positive polarity switch 7 and the isolating switch 13 are electrically connected by adopting a corrugated pipe, the wire outlet end of the negative polarity switch 8 is connected with the equipment ground, the bottom of the isolating switch and the positive polarity direct current source are electrically connected by adopting screw fastening, and the middle leading-out electrode of the polarity conversion switch (the electrical connection part of the positive polarity switch and the negative polarity switch) is fixed with the high-voltage wire outlet end of the negative polarity direct current source by using screws. The top end of the inductor is a high-voltage outlet end which is connected with a capacitor to be detected or a cable.
The direct current source is used for pressurizing and energy supplementing, and an emergency stop and safety control mode is added, so that the device is safer and more reliable.
The polarity conversion switch is composed of single switches connected in series, and forms a voltage division structure from top to bottom in a voltage-resistant working state, so that the breakdown and creepage voltage of the switches in the direct current charging process are improved.
Control panel adopts import switch pilot lamp, and alternating current power supply takes boat form switch, original papers such as indicating device state, realizes functions such as human-computer interaction, status indication, interchange input.
The control unit adopts NI-USB-6211, NI-USB-5133 and a trigger and control system to realize the functions of switch on and switch off control, direct current source control, voltage acquisition, partial discharge acquisition and the like.
The inductance, the fretwork in the middle of the terminal shape design is the cylinder, considers the voltage too high in the design, its curvature radius of maximize, and the fillet is all polished into to the cylinder sideline to prevent point discharge.
In order to improve the breakdown and creepage voltage of the inductor in the direct current charging process, the bottom of the inductor is designed with a non-partial discharge base, and the base is square and made of glass fiber materials, so that the base has the advantages of no partial discharge, small occupied area, high strength and the like and is used for placing the inductor and leading out a low-voltage end of the inductor. Each inductor is divided into 4 segments during winding, so the actual interlayer voltage should be 350V. Therefore, the turn-to-turn voltage and the interlayer voltage are both far smaller than the effective value of breakdown voltage of 3.8kV under the national standard, and the parameter design meets the requirements of an oscillating wave system.
Secondly, the inductor is designed to be an outgoing line at the upper end part and the lower end part, the corona-proof shielding terminal is reasonably designed, the reasonable terminal is an electrode which is not easy to generate corona and is convenient to connect, and the electrode is a cylindrical electrode with a threaded hole.
And finally, if the vacuum degree of the reactor in epoxy pouring is not up to the standard, bubbles and foreign matters are mixed in the reactor in the pouring process. Epoxy pouring of solid insulating materials causes uneven distribution of electric field strength among the conductors. If the vacuum is not sufficient, the insulator will always produce some very small defects and voids during the manufacturing process. These voids are filled with air, which has a lower breakdown strength than the surrounding solid material. And the dielectric constant of gases is always lower than that of solid insulating materials. Thus resulting in a higher electric field strength at the cavities than at the insulating material. Therefore, under the normal working field intensity of the insulation, the voltage value born by the cavity can exceed the breakdown voltage value, and the cavity starts to break down. It is not practical to remove the bubbles completely, and the bubbles can be reduced and reduced by stirring, increasing the vacuum degree and in a dust-free workshop.
Fig. 4 is a waveform diagram of an output of the frequency tunable ultra-low frequency voltage withstanding device according to the present invention, and the present invention includes: positive polarity withstand voltage, negative polarity withstand voltage, positive polarity oscillation, and negative polarity oscillation.
During the cosine test, the cable is pressurized to 3U0The test voltage of (1). After 0.5-5 seconds (according to different frequencies, the diagram is a 0.1Hz diagram), the charges stored in the cable are discharged through a change-over switch, the discharging process is actually to charge an L-C circuit, and then the cosine oscillation function of the L-C circuit enables all the stored energy to be reversely charged to the cable, and the polarity is opposite. The switching slope is similar to a 50Hz sine wave and has a similar effect to the 50Hz test.
The L-C circuit in the invention is composed of a cable capacitor, an auxiliary capacitor (used when the length of the tested cable is short) and an inductor.
Negative voltage withstand, cable pressurized to 3U0The test voltage of (1). As in processes 1 and 2 of fig. 4, maintaining this voltage is the negative withstand voltage.
After the negative polarity is oscillated and pressurized for 0.5-5 seconds (according to different frequencies, the diagram is a 0.1Hz diagram), the charges stored in the cable are discharged through a change-over switch, and the discharging process is actually to charge an L-C circuit, as shown in the process 3 in FIG. 4.
The positive voltage withstanding and negative voltage oscillation utilize the cosine oscillation function of L-C circuit to reversely charge the stored energy to the cable, and the opposite polarity pressurizes the cable to 3U0As shown in process 4 of fig. 4, maintaining this voltage is a positive polarity withstand voltage.
After positive polarity oscillation and positive polarity pressurization for 0.5-5 seconds, the charge stored in the cable is discharged again through a change-over switch, and the discharging process is actually charging an L-C circuit, as shown in the process 5 in FIG. 4.
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects: the ultra-low frequency withstand voltage device has a conversion slope similar to a 50Hz sine wave and has an effect similar to that of the 50Hz test. Since the energy loss during "energy recycling" is small, only a small boost charge is required per cycle. Therefore, compared with the common alternating voltage test and other test methods, the method requires a very small and light high-voltage power supply and test equipment.
The specific working principle of the device of the invention is as follows:
the ultralow frequency voltage withstand test device takes cosine square waves as test waveforms, the working principle of the ultralow frequency voltage withstand test device is that the conversion slope generated by charging and discharging of a power cable is similar to a sine wave, the polarity conversion time is generally 2-6 ms, the polarity conversion time of voltage in a general power frequency voltage withstand test sample is 10ms, and the voltage polarity conversion time of two voltage withstand test methods is very close, so that the method has good equivalence with a power frequency test. This test is based on periodically alternating polarity every 0.5-5 s to obtain a frequency of 0.1 Hz. The switch from one pole to the other is produced by two polarity reversing switches, a capacitor consisting of a choke (inductance) and the capacitance of the cable itself, which can be connected in parallel with a system capacitor of 0.5uF when the length of the cable to be tested is short and is not sufficient to produce resonance. This device is a high power resonant tank. After the cable is connected, the energy stored in the cable capacitance is transferred via the rectifier to the choke coil, the cable first discharging its energy in the form of a magnetic field stored in the choke coil. When zero is reached, the choke releases its energy and adds the voltage back to the cable with the opposite polarity. As a result, the cable is charged with opposite polarity, and this transition through the resonant tank produces a smooth cosine voltage waveform with a width of 2-6 ms, which varies like a 50Hz sine wave. As shown in fig. 5 and 6.
The relative arrangement of the components and steps, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
In the description of the present application, it is to be understood that the orientation or positional relationship indicated by the directional terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal" and "top, bottom", etc., are generally based on the orientation or positional relationship shown in the drawings, and are used for convenience of description and simplicity of description only, and in the case of not making a reverse description, these directional terms do not indicate and imply that the device or element being referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore, should not be considered as limiting the scope of the present application; the terms "inner and outer" refer to the inner and outer relative to the profile of the respective component itself.
Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may be otherwise variously oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
Claims (10)
1. A frequency-adjustable cosine square wave voltage generating device is characterized by comprising a bottom plate, an inductance supporting column, a control unit, an isolating switch and a control panel, wherein the inductance supporting column is arranged on the bottom plate, an inductance is arranged at the top end of the inductance supporting column, a positive polarity direct current source and a frequency-adjustable positive polarity switch are fixed at the top of the control unit, a negative polarity direct current source is fixedly connected onto the positive polarity direct current source, a frequency-adjustable negative polarity switch is fixedly connected onto the frequency-adjustable positive polarity switch, and the inductance, a tested cable, the positive polarity direct current source and the isolating switch are connected in series; the two ends of the frequency-adjustable positive switch and the frequency-adjustable negative switch which are connected in series are connected in parallel to the two ends of the isolating switch and the positive direct-current source; the negative direct current source is connected in parallel at two ends of the frequency-adjustable negative switch, and the outer side of the inductor is fixedly connected with the voltage divider and the coupling capacitor.
2. The apparatus of claim 1, wherein the inductor and the resistor to be tested form an L-C circuit.
3. The apparatus of claim 2, wherein the inductor support posts are made of an insulating material.
4. The apparatus of claim 3, wherein a non-corona wire is disposed under the inductor.
5. The apparatus according to claim 4, wherein the frequency-adjustable positive polarity switch and the frequency-adjustable negative polarity switch are connected in series.
6. The apparatus according to claim 5, wherein the voltage divider and the coupling capacitor are connected in parallel with the cable to be measured.
7. The apparatus according to claim 6, wherein casters are disposed under the base plate.
8. The apparatus according to claim 7, further comprising an outer shield, wherein the inductor is spaced from the outer shield by more than 5 cm.
9. A method for generating a cosine square-wave voltage with adjustable frequency, characterized in that, by using the cosine square-wave voltage generating device with adjustable frequency as claimed in any of claims 1 to 8, a control unit controls to output a positive-polarity withstand voltage waveform, a negative-polarity withstand voltage waveform, a positive-polarity oscillation waveform and a negative-polarity oscillation waveform.
10. The method according to claim 9, wherein the control unit controls the output of the positive polarity oscillating waveform and the negative polarity oscillating waveform.
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Application publication date: 20200922 |