CN110716080B - High-voltage transmission line three-phase voltage harmonic synchronous detection method - Google Patents
High-voltage transmission line three-phase voltage harmonic synchronous detection method Download PDFInfo
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- CN110716080B CN110716080B CN201910962755.2A CN201910962755A CN110716080B CN 110716080 B CN110716080 B CN 110716080B CN 201910962755 A CN201910962755 A CN 201910962755A CN 110716080 B CN110716080 B CN 110716080B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0084—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring voltage only
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- G—PHYSICS
- G01—MEASURING; TESTING
- 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
- G01R1/02—General constructional details
- G01R1/04—Housings; Supporting members; Arrangements of terminals
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/04—Voltage dividers
- G01R15/06—Voltage dividers having reactive components, e.g. capacitive transformer
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/16—Spectrum analysis; Fourier analysis
- G01R23/165—Spectrum analysis; Fourier analysis using filters
- G01R23/167—Spectrum analysis; Fourier analysis using filters with digital filters
Abstract
The invention provides a high-voltage transmission line three-phase voltage harmonic synchronous detection method, which comprises the following steps: the three detection devices are respectively close to or contact with the high-voltage transmission line, and a first stray capacitor and a second stray capacitor which are formed are connected with the voltage division capacitor in series; the method comprises the steps that a far-end handheld device sends 50Hz square wave signals modulated by ASK to three signal processing units to enable the three signal processing units to be started synchronously, each signal processing unit starts to collect voltage at two ends of a voltage division capacitor after receiving the square wave signals, harmonic content of voltage of a power transmission line is calculated according to the voltage, and then a calculation result is sent to the handheld device. The invention realizes direct synchronous detection of the harmonic content of the three-phase high-voltage transmission line by utilizing electric field coupling, has simple and convenient detection, high precision, no limit of voltage grade of the voltage transmission line and wide application range.
Description
Technical Field
The invention relates to the field of harmonic detection, in particular to a three-phase voltage harmonic synchronous detection method for a high-voltage transmission line.
Background
The traditional harmonic detection method for the high-voltage transmission line adopts a wired mode, namely, a harmonic detector is connected to a PT/CVT secondary side in a transformer substation, the voltage on a bus is detected by detecting a small voltage signal of the PT/CVT secondary side, and the harmonic content in the transmission line is indirectly obtained. According to statistics, Capacitor Voltage Transformers (CVTs) are almost all used for voltage transformers with voltage class of above 72.5kV abroad, and CVTs are widely used for voltage transformers with voltage class of 110kV and above at home. However, the method is not applicable to harmonic analysis due to the inherent influence of the transmission characteristics of the CVT, and the CVT cannot be used for harmonic measurement according to the specific regulations of national standard GB/T14549 Power quality public grid harmonic and IEC related standards. The reason is that the harmonic content of the voltage signal is measured secondarily by the CVT, and then the harmonic content of the line is calculated according to the proportion, the harmonic of different frequencies can be attenuated according to different proportions due to the capacitance characteristic of the CVT, the attenuation proportion is not in a linear proportion relation, so that the measurement result has great deviation, and the maximum deviation amount can reach 36.70%, therefore, the harmonic voltage test result measured from the CVT can cause the false phenomenon that the power supply voltage of a plurality of public connection points is unqualified. Therefore, the traditional measurement result for detecting the harmonic waves of the high-voltage line by means of the CVT is not accurate enough, and the traditional detection mode can only measure the internal line of the transformer substation, and the harmonic waves of the high-voltage line outside the transformer substation can not be measured due to the fact that the CVT cabinet is not installed. Meanwhile, for a 10kV high-voltage line, because a primary side neutral point of the CVT is connected with a detuning resistor in series to be grounded, the measurement result of harmonic voltage reflecting zero sequence characteristics (such as 3-order harmonic) can be influenced, and finally, the test result of the total distortion rate of the harmonic voltage is influenced.
Disclosure of Invention
The invention aims to provide a method for synchronously detecting three-phase voltage harmonic waves of a high-voltage transmission line aiming at the defects of the prior art, which realizes synchronous detection of the harmonic wave content of the three-phase high-voltage transmission line by utilizing electric field coupling, has the advantages of simple and convenient detection, high precision, no limitation of the voltage grade of the high-voltage transmission line and wide application range.
The invention is realized by the following technical scheme:
a three-phase voltage harmonic synchronous detection method for a high-voltage transmission line comprises the following steps:
A. the detection devices comprise a PCB, metal electrodes, voltage-dividing capacitors and a signal processing unit, wherein the metal electrodes, the voltage-dividing capacitors and the signal processing unit are respectively arranged on the PCB;
B. the method comprises the steps that a far-end handheld device sends 50Hz square wave signals modulated by ASK to three signal processing units to enable the three signal processing units to be started synchronously, each signal processing unit starts to collect voltage at two ends of a voltage division capacitor after receiving the square wave signals, harmonic content of voltage of a power transmission line is calculated according to the voltage, and then a calculation result is sent to the handheld device.
Further, the PCB board includes first PCB board and second PCB board, and first PCB board is circular structure and stratum copper facing, and the second PCB board includes rectangle portion and the trapezoidal portion of setting on rectangle portion, and the perpendicular spot welding of rectangle portion is connected on first PCB board, the metal electrode sets up at trapezoidal portion top, and during the use, first PCB board keeps parallel with the ground basically.
Further, detection device still includes the electrode installed part, and the electrode installed part is including setting up riser, the diaphragm of setting in riser upper end and the first double-screw bolt of setting on the diaphragm of trapezoidal portion upper end, first double-screw bolt periphery are provided with first external screw thread, the top is provided with first interior screw hole, the metal electrode lower extreme is provided with the second double-screw bolt that matches with first screw, the metal electrode pass through the electrode installed part with the partial pressure electric capacity electricity is connected.
Further, detection device is still including the metal voltage-sharing cover that covers the PCB board and the insulating casing of setting in metal voltage-sharing cover periphery, the longitudinal section of metal voltage-sharing cover and insulating casing with second PCB plate shape is the same, the metal voltage-sharing cover with the ground end elasticity electricity of second PCB board is connected, the insulating casing top is provided with first recess, is provided with the confession in the first recess the first hole of stepping down that first double-screw bolt wore out, and the nut that matches with first external screw thread locks in order to fix insulating casing, metal voltage-sharing cover and second PCB board in the first recess.
Furthermore, the detection device further comprises a spring arranged between the second PCB and the metal voltage-sharing cover, one end of the spring is welded at the ground end of the second PCB, the other end of the spring can be electrically connected with the metal voltage-sharing cover, and after the metal voltage-sharing cover covers the second PCB, the spring is compressed by the metal voltage-sharing cover to realize reliable elastic electric contact between the metal voltage-sharing cover and the ground end of the second PCB.
Furthermore, the signal processing unit comprises a follower amplifier with an input end connected with the voltage-dividing capacitor, an IDT90E36 chip with an input end connected with the output end of the follower amplifier, and a first microprocessor with an input end connected with the output end of the IDT90E36 chip, the handheld device comprises a second microprocessor, a key unit connected with the input end of the second microprocessor, and a display unit connected with the output end of the second microprocessor, and the first microprocessor and the second microprocessor are in wireless two-way communication connection.
Furthermore, the signal processing unit comprises a following amplifier with an input end connected with the voltage division capacitor, and a first microprocessor with an input end connected with an output end of the following amplifier, the handheld device comprises a second microprocessor, a key unit connected with an input end of the second microprocessor, and a display unit connected with an output end of the second microprocessor, and the first microprocessor and the second microprocessor are in wireless two-way communication connection.
Furthermore, the metal pressure equalizing cover comprises a hollow cylinder and a hollow frustum arranged at the upper end of the hollow cylinder, the hollow cylinder and the hollow frustum are integrally formed, the metal pressure equalizing cover is made of a copper material, and the thickness of the metal pressure equalizing cover is 0.05-0.15 mm.
Further, the step a further includes: and the three insulated telescopic rods detachably connected with the detection devices respectively approach or contact the detection devices to the high-voltage transmission line.
Further, detection device passes through the telescopic link connecting piece and can dismantle with insulating telescopic link and be connected, insulating casing outside lower part is provided with the boss, be provided with the spacing step of second on the boss, and it has the through-hole to open, the telescopic link connecting piece has the arcwall face that matches with insulating casing, be provided with on the arcwall face with the second recess that can supply the boss embedding, be provided with the second screw on the second recess, first bolt passes the spacing step of second, through-hole locking through opening the utensil is in the second screw, telescopic link connecting piece lower extreme is provided with the third screw, the telescopic link top is provided with the third double-screw bolt that matches with the third screw.
The invention has the following beneficial effects:
1. when the detection is carried out, the three detection devices are respectively close to a three-phase high-voltage transmission line, due to the effect of electric field coupling, a first stray capacitor is formed between a metal electrode of each detection device and the transmission line, and a second stray capacitor is formed between the bottom of a PCB (printed circuit board) and the ground (when the metal electrode contacts the transmission line, the first stray capacitor is zero, but the second stray capacitor still exists), the first stray capacitor and the second stray capacitor are connected in series with a voltage-dividing capacitor, the voltage at two ends of the voltage-dividing capacitor is obtained by connecting a signal processing unit with the voltage-dividing capacitor, the harmonic content of the voltage of the transmission line is calculated according to the voltage, the detection process is simple and convenient, and the detection result is high in precision; the handheld device sends ASK modulated synchronous square wave signals to the three detection devices respectively, so that the synchronism of voltage acquisition of the three-phase high-voltage line can be ensured, and the detection precision is further improved; the PCB is covered by the metal voltage-sharing cover, so that the phenomenon that the detection result is influenced by point discharge of components on the PCB in high voltage can be avoided; the invention utilizes the stray capacitance voltage division principle, and the voltage division capacitor is completely isolated from the ground, so the voltage grade which can be born is not limited, the requirement of the highest voltage grade 1100kV voltage at home and abroad can be met, and the application range is wide.
2. The PCB comprises a first PCB and a second PCB, wherein the first PCB is of a circular structure and is coated with copper, when the first PCB is basically parallel to the ground, a second stray capacitor can be formed between the first PCB and the ground, and an electrode mounting part is arranged on the second PCB, so that the metal electrode and the voltage dividing capacitor are reliably electrically connected, and the metal voltage equalizing cover and the insulating shell can be conveniently mounted.
3. The metal voltage-sharing cover is elastically and electrically connected with the ground end of the second PCB through the spring, the connection structure is simple and reliable, the signal processing unit and the metal voltage-sharing cover can be ensured to be in an equipotential state, the problem of electric field concentration is solved, and the voltage resistance is improved.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of a first embodiment of the present invention.
Fig. 2 is an exploded view of fig. 1.
Fig. 3 is a schematic structural diagram of an insulating housing according to an embodiment of the invention.
Fig. 4 is a schematic structural view of an insulating telescopic rod connecting piece according to an embodiment of the present invention.
Fig. 5 is a schematic block diagram of a first embodiment of the invention.
Fig. 6 is a schematic circuit diagram of a detection apparatus according to an embodiment of the invention.
Fig. 7 is a schematic circuit diagram of a third embodiment of the present invention.
Fig. 8 is a schematic circuit diagram of a fourth embodiment of the present invention.
Wherein, 1, a detection device; 11. a metal electrode; 111. a second stud; 12. a voltage-dividing capacitor; 13. a follower amplifier; 14. IDT90E36 chip; 15. a first microprocessor; 16. an acousto-optic prompt unit; l, a hollow inductor; r1, resistance; r2, high-pressure discharge tube; d1, a diode; 13. a follower amplifier; 14. IDT90E36 chip; 2. a wireless communication device; 21. a first wireless transceiving device; 22. a second wireless transceiver; 3. a handheld device; 31. a second microprocessor; 32. a key unit; 33. a display unit; 4. an insulating telescopic rod connecting piece; 41. an arc-shaped surface; 42. a second groove; 43. a second screw hole; 44. a third screw hole; 5. an insulating housing; 51. a first groove; 52. a first abdicating hole; 53. a nut; 54. an extension block; 55. a boss; 56. a through hole; 6. insulating telescopic links; 61. a third stud; 7. a second PCB board; 71. a rectangular portion; 72. a trapezoidal portion; 73. a vertical plate; 74. a transverse plate; 75. a first stud; 76. an O-shaped ring notch; 77. a spring; 78. a first PCB board; 79. a circular base; 8. a metal voltage-sharing cover; IC3, power chip; c2, an energy storage capacitor; d2, diac; d3, light emitting diode; r3, current limiting resistor.
Detailed Description
The first embodiment is as follows:
as shown in fig. 1 to 6, the harmonic detection system of the high-voltage transmission line comprises three insulating telescopic rods 6, three detection devices 1 respectively arranged on the three insulating telescopic rods 6, a wireless communication device 2 and a handheld device 3 respectively connected with the three detection devices 1 in a bidirectional communication manner, the handheld device 3 is arranged at a far end, the detection device 1 comprises a PCB board, metal electrodes 11 respectively arranged on the PCB board, a voltage-dividing capacitor 12, an air-core inductor L, a resistor R1, a high-voltage discharge tube R2, a diode D1, an RC filter circuit, a signal processing unit and an acousto-optic prompting unit, a metal voltage-equalizing cover 8 covering the PCB board and an insulating shell 5 arranged at the periphery of the metal voltage-equalizing cover 8, the PCB board is coated with copper, the signal processing unit comprises a following amplifier 13 with an input end connected with the voltage-dividing capacitor 12 in parallel, an IDT90E36 chip 14 with an input end connected with an output end of the following amplifier 13, and a first microprocessor 15 with an input end connected with an output end of the IDT90E36 chip 14, the sound and light prompting unit comprises a first light emitting diode and a second light emitting diode which are respectively connected with the first microprocessor 15, the handheld device 3 comprises a second microprocessor 31, a key unit 32 connected with the input end of the second microprocessor 31 and a display unit 33 connected with the output end of the second microprocessor 31, the first microprocessor 15 and the second microprocessor 31 are in wireless two-way communication connection through the wireless communication device 2 to realize data transmission, and after the key unit 32 of the handheld device 3 inputs a command, the second microprocessor 31 respectively sends ASK modulated synchronous 50Hz square wave signals to the first microprocessor 15 of each detection device 1 to synchronously start the detection devices. The voltage of the high-voltage transmission line is very high, so the electric field intensity distributed around the high-voltage transmission line is very high, when the high-voltage transmission line works, when the metal electrode 11 is close to the high-voltage transmission line, according to the electric field theory, a certain electric charge quantity can be induced on the metal electrode 11, so that a first stray capacitor is formed between the metal electrode 11 and the high-voltage transmission line, and a second stray capacitor is formed between the metal electrode 11 and the ground, when the metal electrode is coupled to the first stray capacitor and/or the second stray capacitor, the first microprocessor 15 controls the first light-emitting diode to emit light, when the electric field intensity distributed around the high-voltage transmission line is too strong, the first microprocessor 15 controls the second light-emitting diode to emit light, the first microprocessor 15 controls the first light-emitting diode and the second light-emitting diode to emit light, the prior art is adopted, the first stray capacitor and the second stray capacitor are connected in series with the voltage dividing capacitor 12, the signal processing unit is connected in parallel with the voltage dividing capacitor 12 to obtain voltage signals at two ends, and after calculating the content of each harmonic of the voltage of the power transmission line according to the voltage signal, the calculation result is sent to the handheld device 3 and displayed by the display unit 33. The wireless communication device 2 includes a first wireless transceiver 21 connected to the first microprocessor 15 and a second wireless transceiver 22 connected to the second microprocessor 31, where the first wireless transceiver 21 and the second wireless transceiver 22 are both in the prior art. The key unit 32 and the display unit 33 are both related art.
The resistor R1, the hollow-core inductor L and the voltage dividing capacitor 12 are connected in series and then connected in parallel with the high-voltage discharge tube R2, the metal electrode 11 is reliably and electrically connected with a collection connection point of the high-voltage discharge tube R2 and the resistor R1, the follower amplifier 13, the diode D1 and the RC filter circuit are all connected in parallel with the voltage dividing capacitor 12, the diode D1 is used for performing transient suppression on voltage signals at two ends of the voltage dividing capacitor 12, the RC filter circuit is used for performing anti-aliasing filtering processing on the voltage signals, the voltage at two ends of the voltage dividing capacitor 12 enters the follower amplifier 13 after passing through the diode D1 and the RC filter circuit, the output end of the follower amplifier 13 is connected with the signal processing unit, after the detection device 1 is close to a power transmission line, the coupled first stray capacitor is connected in series with the resistor R1, the second stray capacitor is connected in series with the voltage dividing capacitor 12, namely, the first stray capacitor, the resistor R1, the hollow-core inductor L, the voltage dividing capacitor 12 and the second stray capacitor are connected in series and then connected in parallel with the high-voltage discharge tube R2, so can divide voltage according to certain proportion with transmission line's voltage, resistance R1 and hollow inductance L's effect lies in preventing that metal electrode 11 from discharging to the transmission line and destroying divider capacitance 12, guarantees the reliability that detection device 1 used under high-voltage environment, and high-pressure discharge tube R2 is used for providing a discharge route for divider capacitance 12 to avoid too high voltage to damage divider capacitance 12.
In this embodiment, the voltage-dividing capacitor 12 is a nonpolar capacitor with withstand voltage greater than 63VAC and capacity of 0.01 μ F; the resistor R1 adopts a power resistor R1 of 100k omega/2W and is used for limiting the current of the capacitor loop; the hollow-core inductor L is 100 mu H/5A and is used for preventing the detection device 1 from generating instantaneous discharge when approaching the power transmission line and limiting current mutation; the high-pressure discharge tube R2 is a discharge tube rated at 60 VAC.
The PCB comprises a first PCB 78, a second PCB 7 and a circular base 79, the first PCB 78 is arranged on the circular base 79 through bolts, the first PCB 78 is also of a circular structure and is coated with copper on the ground, 2 indicator lamps with different light-emitting colors are welded on the first PCB, the indicator lamps are respectively coupled to an electric field for indication and an electric field signal over-strong indication, the second PCB 7 comprises a rectangular portion 71 and a trapezoidal portion 72 arranged on the rectangular portion 71, the lowest end of the rectangular portion 71 is vertically connected to the first PCB 78 in a spot welding mode, welding spots are used as transmission leads of signals, the first PCB 78 is horizontally arranged, metal electrodes 11 are detachably arranged at the uppermost end of the trapezoidal portion 72 through electrode mounting pieces 73 and are required to be reliably and electrically connected with the first PCB 78, and during use, the ground of the first PCB 78 is basically parallel to the ground so as to be capable of coupling out a second stray capacitor. Electrode installation part 73 includes through second bolt locking at the riser 73 of trapezoidal portion 72 topmost, set up at riser 74 upper end and set up the first double-screw bolt 75 on horizontal board 74, first double-screw bolt 75 periphery is provided with first external screw thread, the top is provided with first interior screw hole, metal electrode 11 lower extreme is provided with the second double-screw bolt 111 that matches with first interior screw hole, metal electrode 11 upper end can be the hook type, the Y type, acicular or column, in this embodiment, metal electrode 11 upper end is the Y type, metal electrode 11 realizes the electricity through electrode installation part 73 and partial pressure electric capacity 12 and is connected. Still be provided with O type circle notch 76 on the riser 73, also be provided with O type circle notch on the circular base 79, arrange O type circle in the O type circle notch, can guarantee that electrode mounting part 73 is sealed well when fixed with insulating casing 5.
The longitudinal sections of the metal voltage-sharing cover 8 and the insulating shell 5 are the same as the shape of the second PCB 7, specifically, the metal voltage-sharing cover 8 and the insulating shell 5 both comprise a hollow cylinder and a hollow frustum arranged at the upper end of the hollow cylinder, the hollow cylinder and the hollow frustum are integrally formed, the diameter of the hollow cylinder is matched with the diameter of the circular base 79, the metal voltage-sharing cover 8 is made of copper material and has a thickness of 0.1mm, the insulating shell 5 is made of insulating plastic, a circular first groove 51 is arranged at the top of the insulating shell 5, a first abdicating hole 52 for the first stud 75 to penetrate out is arranged in the first groove 51, a nut 53 matched with the first external thread is locked on the first stud 75, the peripheral diameter of the nut 53 is matched with the diameter of the first groove 51, so that when the nut 53 is locked on the first stud 75, the nut 53 is just positioned in the first groove 51, thereby fixing the insulating shell 5, the metal voltage-sharing cover 8 and the second PCB 7, the nut 53 is made of a non-metallic material.
The insulating telescopic rod 6 is fixedly connected with the insulating shell 5 through an insulating telescopic rod connecting piece 4, one side of the lower end of the insulating shell 5 is provided with an extending block 54 extending downwards, the outer side of the extending block 54 is provided with a boss 55, the boss 55 is provided with a second limiting step and is provided with a through hole 56, the insulating telescopic rod connecting piece 4 is provided with an arc surface 41 matched with the insulating shell 5, the arc surface 41 is provided with a second groove 42 for the boss 55 to be embedded into, the second groove 42 is provided with a second screw hole 43, a first bolt passes through the second limiting step and is locked in the second screw hole 43 through the opened through hole 56, the lower end of the insulating telescopic rod connecting piece 4 is provided with a third screw hole, the top end of the insulating telescopic rod 6 is provided with a third screw bolt 61 and a third screw hole 44 matched with the third screw hole, the insulating shell 5 is in surface contact with the insulating telescopic rod connecting piece 4, and the use process can be effectively prevented, the insulating shell 5 rotates relative to the insulating telescopic rod 6.
The metal voltage-sharing cover 8 is elastically and electrically connected with the ground end of the second PCB 7, so as to ensure reliable electrical connection between the metal voltage-sharing cover 8 and the second PCB 7, the elastic connection is specifically that a spring 77 is arranged between the second PCB 7 and the metal voltage-sharing cover 8, one end of the spring 77 is welded on the second PCB 7 so as to be electrically connected with the ground end of the second PCB 7, after the metal voltage-sharing cover 8 covers the second PCB 7, the spring 77 is compressed by the metal voltage-sharing cover 8, so that the elastic electrical contact between the metal voltage-sharing cover 8 and the ground end of the second PCB 7 is realized.
In this embodiment, the first microprocessor 15 and the second microprocessor 31 are both STM32 microprocessors, ASK modulation of a 50Hz square wave signal is realized by programming of the STM32 microprocessor, and for the prior art, the second microprocessor 31 is awakened after receiving the square wave signal, so as to start to acquire the voltage at two ends of the voltage dividing capacitor 12, and the IDT90E36 chip 14 calculates the voltage to obtain 2-32 th and 3-31 th harmonic contents of the power transmission line.
The method for synchronously detecting the three-phase voltage harmonic waves of the high-voltage transmission line comprises the following steps:
A. the three detection devices 1 are respectively close to the high-voltage transmission line, each detection device 1 comprises a PCB, metal electrodes 11, voltage-dividing capacitors 12 and a signal processing unit, the metal electrodes 11, the voltage-dividing capacitors 12 and the signal processing unit are respectively arranged on the PCB, a first stray capacitor is formed between each metal electrode 11 and the high-voltage transmission line, a second stray capacitor is formed between the ground layer of the PCB and the ground, and the first stray capacitor and the second stray capacitor are connected in series with the voltage-dividing capacitors 12;
B. the method comprises the steps that a remote handheld device 3 sends 50Hz square wave signals modulated by ASK to three signal processing units to enable the three signal processing units to be started synchronously, each signal processing unit starts to collect voltage at two ends of a voltage division capacitor 12 after receiving the square wave signals, the harmonic content of the voltage of a power transmission line is calculated according to the voltage, and then a calculation result is sent to the handheld device 3 or stored in a U disk connected with the signal processing units.
The invention utilizes the principle that a capacitor is formed between a conductor arranged in a space and a power transmission line and the ground respectively, and the formed capacitor is connected with the voltage division capacitor 12 in series for voltage division, when the power transmission line has voltage, a voltage signal is induced at two ends of the voltage division capacitor 12 according to the voltage division effect of the series capacitor, namely, the voltage of the power transmission line is divided according to a certain proportion, and the harmonic content of the voltage signal is analyzed, so that the harmonic content of the power transmission line can be obtained.
In this embodiment, the detection device 1 is close to the power transmission line, the first stray capacitor is coupled between the metal electrode 11 and the power transmission line, and the second stray capacitor is coupled between the PCB and the ground, in another embodiment, the detection device 1 may also be in contact with the power transmission line, so although the first stray capacitor is no longer coupled between the metal electrode 11 and the power transmission line (i.e., the first stray capacitor is zero), the second stray capacitor is coupled between the PCB and the ground, and the second stray capacitor is connected in series with the voltage dividing capacitor 12, so that the voltage at two ends of the voltage dividing capacitor 12 can still be subjected to harmonic analysis.
In this embodiment, be close to or contact transmission line with detection device 1 through insulating telescopic link 6, ensured staff's personal safety, and to the high tension transmission line of higher voltage class, can hang detection device 1 at the unmanned aerial vehicle lower extreme, be close to transmission line with detection device 1 through unmanned aerial vehicle, thoroughly stop that the staff takes place dangerous condition and take place.
Example two:
the difference between this embodiment and the first embodiment is: the signal processing unit comprises a following amplifier with an input end connected with the voltage-dividing capacitor and a first microprocessor with an input end connected with the output end of the following amplifier, the handheld device comprises a second microprocessor, a key unit connected with the input end of the second microprocessor and a display unit connected with the output end of the second microprocessor, and the first microprocessor and the second microprocessor are in wireless two-way communication connection through a wireless communication device. The voltage at two ends of the voltage-dividing capacitor is directly subjected to harmonic analysis by the first microprocessor, and because the FFT operational capability of the first microprocessor is limited, the FFT with limited points can only be processed, so that when a periodic signal in a time domain is intercepted, an integral multiple period cannot be intercepted, an infinite sample cannot be obtained during signal analysis, as long as the interception is asynchronous, the occurrence of frequency spectrum leakage can be caused, in order to reduce the frequency spectrum leakage component of the harmonic wave, the accuracy of harmonic wave detection is further improved, the attenuation of spectral line amplitude values outside the main frequency is required to be further accelerated, and the mutual interference among the harmonic waves is avoided. Therefore, windowing processing needs to be performed on the signal after sampling, the frequency resolution of fourier analysis is mainly affected by the width of the main lobe of the window function, and the leakage degree depends on the relative amplitudes of the main lobe and the side lobes.
Example three:
as shown in fig. 7, the present embodiment is different from the first embodiment in that: the power transmission line harmonic detection device is provided with a self-powered unit, and specifically comprises the following components: the detection device comprises a first PCB, a second PCB, metal electrodes, a voltage-dividing capacitor, a signal processing unit and a self-powered unit, wherein the signal processing unit is the same as the first embodiment, the first PCB is horizontally arranged, the ground layer of the first PCB is coated with copper, the second PCB is vertically welded on the first PCB, the metal electrodes are arranged at the upper end of the second PCB, the voltage-dividing capacitor, the signal processing unit and the self-powered unit are arranged on the second PCB, the metal electrodes are connected with the voltage-dividing capacitor in series, the self-powered unit comprises a rectifying circuit, an electric energy chip IC3 and an energy storage capacitor C2, the input end of the signal processing unit and the input end of the rectifying circuit are both connected with the voltage-dividing capacitor, the output end of the rectifying circuit is connected with the input end of the electric energy chip IC3, the output end of the electric energy chip IC3 is connected with the energy storage capacitor C2, the energy storage capacitor C2 is connected with a corresponding power supply end of the signal processing unit to provide working electric energy for the signal processing unit, and specifically, the energy storage capacitor C2 is connected with a power supply end of the first microprocessor 15, when the circuit works, a first stray capacitor is formed between the metal electrode and the power transmission line, a second stray capacitor is formed between the first PCB layer and the ground, the first stray capacitor and the second stray capacitor are connected in series with the voltage dividing capacitor, the signal processing unit acquires voltage signals at two ends of the voltage dividing capacitor, and the harmonic content of the voltage of the power transmission line is calculated according to the voltage signals. In this embodiment, the power chip IC3 is of type LTC 3588-2.
Example four:
as shown in fig. 8, the present embodiment is different from the first embodiment in that: the power transmission line is characterized by further comprising an electrified detection circuit, the electrified detection circuit comprises a rectifying circuit, an energy storage capacitor C2, a bidirectional trigger diode D2, a light emitting diode D3 and a current-limiting resistor R3, the input end of the rectifying circuit is connected with a voltage-dividing capacitor, the output end of the rectifying circuit is connected with an energy storage capacitor C2, the bidirectional trigger diode D2, the light emitting diode D3 and the current-limiting resistor R3 are connected in series and then connected with the energy storage capacitor C2 in parallel, and when the power transmission line is electrified, the light emitting diode D3 emits light for indicating.
The above description is only a preferred embodiment of the present invention, and therefore should not be taken as limiting the scope of the invention, which is defined by the appended claims and their equivalents and modifications within the scope of the description.
Claims (7)
1. A three-phase voltage harmonic synchronous detection method for a high-voltage transmission line is characterized by comprising the following steps: the method comprises the following steps:
A. the detection devices comprise a PCB, metal electrodes, voltage-dividing capacitors and a signal processing unit, wherein the metal electrodes, the voltage-dividing capacitors and the signal processing unit are respectively arranged on the PCB;
B. the method comprises the steps that a far-end handheld device sends ASK-modulated 50Hz square wave signals to three signal processing units to be synchronously started, each signal processing unit starts to acquire voltages at two ends of a voltage division capacitor after receiving the square wave signals, harmonic content of voltage of a power transmission line is calculated according to the voltages, and then calculation results are sent to the handheld device;
the PCB comprises a first PCB and a second PCB, the first PCB is of a circular structure and is coated with copper, the second PCB comprises a rectangular part and a trapezoidal part arranged on the rectangular part, the rectangular part is vertically connected to the first PCB in a spot welding manner, the metal electrode is arranged at the uppermost end of the trapezoidal part, and when the PCB is used, the first PCB is basically parallel to the ground;
the detection device further comprises an electrode mounting piece, the electrode mounting piece comprises a vertical plate arranged at the upper end of the trapezoid part, a transverse plate arranged at the upper end of the vertical plate and a first stud arranged on the transverse plate, first external threads are arranged on the periphery of the first stud, a first internal screw hole is formed in the top of the first external screw hole, a second stud matched with the first internal screw hole is arranged at the lower end of the metal electrode, and the metal electrode is electrically connected with the voltage-dividing capacitor through the electrode mounting piece;
the detection device further comprises a metal voltage-sharing cover covering the PCB and an insulating shell arranged on the periphery of the metal voltage-sharing cover, the longitudinal sections of the metal voltage-sharing cover and the insulating shell are the same in shape of the second PCB, the metal voltage-sharing cover is electrically connected with the ground end of the second PCB, a first groove is formed in the top of the insulating shell, a first yielding hole allowing the first stud to penetrate out is formed in the first groove, and a nut matched with the first external thread is locked in the first groove to fix the insulating shell, the metal voltage-sharing cover and the second PCB.
2. The method for synchronously detecting the three-phase voltage harmonics of the high-voltage transmission line according to claim 1, characterized in that: the detection device further comprises a spring arranged between the second PCB and the metal voltage-sharing cover, one end of the spring is welded at the ground end of the second PCB, the other end of the spring can be electrically connected with the metal voltage-sharing cover, and after the metal voltage-sharing cover covers the second PCB, the spring is compressed by the metal voltage-sharing cover to realize reliable elastic electric contact between the metal voltage-sharing cover and the ground end of the second PCB.
3. The method for synchronously detecting the three-phase voltage harmonics of the high-voltage transmission line according to claim 1 or 2, characterized in that: the signal processing unit comprises a follower amplifier, an IDT90E36 chip and a first microprocessor, wherein the input end of the follower amplifier is connected with the output end of the voltage division capacitor, the IDT90E36 chip is connected with the output end of the follower amplifier, the input end of the first microprocessor is connected with the output end of the IDT90E36 chip, the handheld device comprises a second microprocessor, a key unit and a display unit, the key unit is connected with the input end of the second microprocessor, the display unit is connected with the output end of the second microprocessor, and the first microprocessor and the second microprocessor are in wireless two-way communication connection.
4. The method for synchronously detecting the three-phase voltage harmonics of the high-voltage transmission line according to claim 1 or 2, characterized in that: the signal processing unit comprises a following amplifier with an input end connected with the voltage division capacitor and a first microprocessor with an input end connected with an output end of the following amplifier, the handheld device comprises a second microprocessor, a key unit connected with the input end of the second microprocessor and a display unit connected with the output end of the second microprocessor, and the first microprocessor and the second microprocessor are in wireless two-way communication connection.
5. The method for synchronously detecting the three-phase voltage harmonics of the high-voltage transmission line according to claim 1, characterized in that: the metal pressure equalizing cover comprises a hollow cylinder and a hollow frustum arranged at the upper end of the hollow cylinder, the hollow cylinder and the hollow frustum are integrally formed, the metal pressure equalizing cover is made of a copper material, and the thickness of the metal pressure equalizing cover is 0.05-0.15 mm.
6. The method for synchronously detecting the three-phase voltage harmonics of the high-voltage transmission line according to claim 1 or 2, characterized in that: the step A further comprises the following steps: and the three insulated telescopic rods detachably connected with the detection devices respectively approach or contact the detection devices to the high-voltage transmission line.
7. The method for synchronously detecting the three-phase voltage harmonics of the high-voltage transmission line according to claim 6, characterized in that: detection device passes through the telescopic link connecting piece and can dismantle with insulating telescopic link and be connected, insulating casing outside lower part is provided with the boss, be provided with the spacing step of second on the boss to it has the through-hole to open, the telescopic link connecting piece has the arcwall face that matches with insulating casing, be provided with on the arcwall face with the second recess that can supply the boss embedding, be provided with the second screw on the second recess, first bolt passes the spacing step of second, through-hole locking through opening the utensil is in the second screw, telescopic link connecting piece lower extreme is provided with the third screw, the telescopic link top is provided with the third double-screw bolt that matches with the third screw.
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