Test circuit and impedance data analysis method based on tower impact impedance measurement

Abstract

A test circuit based on the measurement of pole tower impulse impedance includes: an impulse current generator, an injection line, a current measuring device and a voltage measuring device; the high voltage end of the impulse current generator is connected to the pole tower ground wire cross arm through the injection line, the high voltage end of the voltage measuring device is connected to the pole tower top through a wire, the wire is fixed by a fourth insulating bracket, the wire is located between the fourth insulating bracket and the pole tower and the line segment is arranged horizontally and the length is greater than the height of the pole tower; the low voltage end of the impulse current generator and the low voltage end of the voltage measuring device are both connected to the pole tower foot through a grounding cable, and the injection line and the grounding cable are both arranged overhead; the current measuring device is arranged at one end of the injection line close to the pole tower, and the distance between the first insulating bracket and the pole tower is greater than the height of the pole tower. The present invention realizes the measurement of the impulse impedance of the pole tower itself, and provides data support for lightning protection grounding design.

Description

Technical Field

[0001] The invention relates to the field of pole tower high voltage test, and in particular to a test loop based on pole tower impact impedance measurement and an impedance data analysis method. Background Art

[0002] The impulse resistance of transmission line towers is an important parameter for evaluating the lightning strike performance of the line. When a tower is struck by lightning, the potential at the top of the tower increases, and the tower insulator is prone to strike flashover. If the tower impedance increases, the potential at the top of the tower will also increase when the tower is struck by lightning under the same lightning current, and the risk of strike flashover of the tower insulator increases, which is more likely to cause lightning tripping and other situations.

[0003] With the needs of social development, the transmission level of overhead lines is gradually improving, and the height of transmission towers is also increasing. At the same time, the use of new metal materials such as weathering steel for the tower body may increase the impact impedance of the tower, thereby reducing the lightning protection level of the tower. Domestically, many on-site impact impedance tests have been conducted on overhead line towers, all of which are overall impedance measurements of the towers and their grounding devices. However, considering the different soil resistivity in different regions and the different settings of the tower grounding devices, the test results are less applicable, and it is even more impossible to perform self-impedance analysis on a certain type of tower.

[0004] In this case, it is particularly important to measure and analyze the impact impedance of the tower itself. The measurement results can be combined with various types of grounding impedances in various places to better evaluate the impact response of the tower.

[0005] In summary, the impulse impedance of the tower has a great influence on the lightning resistance level of the tower. At the same time, in order to ensure that the measurement data has higher research significance and value, it is very important to measure and analyze the impulse impedance of the tower itself. Therefore, how to measure and analyze the tower body impulse impedance has become a technical problem that needs to be solved urgently. Summary of the invention

[0006] In order to solve the defect of the above-mentioned prior art that there is no technology for measuring the impact impedance of the tower itself, the present invention proposes a test circuit based on the tower impact impedance measurement and an impedance data analysis method.

[0007] The present invention adopts the following technical solutions:

[0008] A test circuit based on tower impulse impedance measurement, comprising: an impulse current generator, an injection line, a current measuring device and a voltage measuring device;

[0009] The high-voltage end of the impulse current generator is connected to the ground wire cross arm of the pole tower through an injection line, and the high-voltage end of the voltage measuring device is connected to the top of the pole tower through a conductor, which is fixed by a fourth insulating bracket. The conductor is located between the fourth insulating bracket and the pole tower and is horizontally arranged, and its length is greater than the height of the pole tower; the low-voltage end of the impulse current generator and the low-voltage end of the voltage measuring device are both connected to the foot of the pole tower through a grounding cable, and the injection line and the grounding cable are both overhead;

[0010] The current measuring device is arranged at one end of the injection line close to the tower.

[0011] Preferably, each tower foot of the tower is connected to a low-voltage end of the impulse current generator and a low-voltage end of the voltage measuring device through a grounding cable.

[0012] Preferably, it also includes a first insulating support arranged on the ground and a second insulating support arranged on the conductor cross arm of the tower, the first insulating support is used to fix the near-ground end of the injection line, the distance between the first insulating support and the tower is greater than the height of the tower; the second insulating support is used to support the injection line; the first insulating support is the same height as the tower, the angle between the injection line located between the first insulating support and the second insulating support and the center line of the tower is 90 degrees, and the angle between the injection line and the conductor is 90 degrees. .

[0013] Preferably, the second insulating bracket includes an L-shaped cylindrical insulating bracket and a U-shaped bolt; a fixed base is installed on the pole tower conductor crossarm, and the short end of the L-shaped cylindrical insulating bracket is connected to the fixed base; the U-shaped bolt is arranged on the L-shaped cylindrical insulating bracket away from the fixed base, and the injection line passes through the U-shaped bolt and is fixed.

[0014] Preferably, the injection line between the first insulating support and the second insulating support is arranged horizontally.

[0015] Preferably, a terminal is provided at one end of the injection line close to the pole tower, and the terminal is connected to the top of the pole tower.

[0016] Preferably, the injection wire is an aluminum stranded wire with an outer layer wrapped with an insulating layer.

[0017] Preferably, one end of the injection line close to the tower is fixed by a tension string arranged on the tower, and the tension string includes: a QP-7 ball head, an insulator string, a W-7 bowl head, a Z-7 right-angle hanging plate, a wedge-shaped wire clamp and two U-0770 hanging rings; the installation method of the tension string is: a U-0770 hanging ring is installed on the ground wire installation hole at the top of the tower, and the U-0770 hanging ring is connected to the QP-7 ball head arranged at the upper end of the insulator string through another U-0770 hanging ring, and the W-7 bowl head arranged at the lower end of the insulator string is connected to the wedge-shaped wire clamp through the Z-7 right-angle hanging plate, and the wedge-shaped wire clamp is used to fix the injection line and make the injection line extend at least 1m to 1.5m long as a live head, and the front end insulation of the live head is stripped to expose the wire core, and the wire core is connected to the top of the tower through a wiring terminal.

[0018] Preferably, the grounding cable is made of copper tape or copper wire, and the grounding cable is suspended in the air through a plurality of third insulating brackets; the height of the grounding cable from the ground is at least 50 cm.

[0019] The current measuring device uses a Rogowski coil, and the voltage measuring device uses a voltage divider.

[0020] An impedance data analysis method for a test loop based on tower impact impedance measurement comprises the following steps:

[0021] S1. Setting the test loop based on tower impact impedance measurement, collecting electrical data through a current measuring device and a voltage measuring device, the electrical data including current and voltage;

[0022] S2, screened current data and voltage data with the same time length and measurement accuracy;

[0023] S3. Filter the screened current and the screened voltage, and then perform Fourier transform on the filtered current and voltage, analyze the frequency composition of the signal, and calculate the frequency domain impedance.

[0024] The advantages of the present invention are:

[0025] (1) The present invention realizes the measurement of the impulse impedance of the pole tower itself, providing data support for lightning protection and grounding design. The impedance results measured by the present invention can be combined with the soil resistivity, grounding grid settings, etc. in various places to analyze the impulse response level of the pole towers in various places, so as to determine the lightning protection level of the pole towers, thereby improving the pertinence and rationality of the lightning protection measures for the pole towers.

[0026] (2) The fourth insulating support is at the same height as the pole tower, so that the conductor is perpendicular to the pole tower, which greatly reduces the electromagnetic coupling between the pole tower and the injection line. The distance between the fourth insulating support and the pole tower is greater than the height of the pole tower, which further reduces the electromagnetic coupling between the pole tower and the injection line.

[0027] (3) The present invention effectively improves the significance and value of the tower impact impedance test. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of a test circuit based on tower impact impedance measurement;

[0029] Figure 2 for Figure 1 A partial enlarged view of

[0030] Figure 3 This is a panoramic view of the test wiring.

[0031] FIG. 4( a ) is a front view of the fixed base.

[0032] FIG4( b ) is a top view of the fixed base.

[0033] Figure 5 This is the fixing diagram of the second insulating bracket and the pole tower conductor crossarm.

[0034] FIG. 6( a ) is a front view of the clamp.

[0035] FIG6( b ) is a top view of the clamp.

[0036] Figure 7 The second insulating bracket and the injection line are fixed

[0037] Figure 8 The present invention is a flow chart of an impedance data analysis method of a test loop based on tower impact impedance measurement;

[0038] Fig. 9 is the impulse current generator waveform;

[0039] Fig.10 Input tower impulse current waveform when the conductor is set vertically to the tower.

[0040] Diagram: impulse current generator 1, injection line 2, tower ground wire crossarm 3, tension string 4, ground wire mounting hole 5, current measuring device 6, first insulating bracket 7, second insulating bracket 8, tower conductor crossarm 9, grounding cable 10, tower foot 11, third insulating bracket 12, voltage measuring device 13, conductor 14, fourth insulating bracket 15, base 16, clamp 17, U-bolt 18, L-shaped cylindrical insulating bracket 19. DETAILED DESCRIPTION

[0041] The present embodiment proposes a test circuit based on tower impulse impedance measurement, which includes: an impulse current generator 1 , an injection line 2 , a current measuring device 6 and a voltage measuring device 13 .

[0042] The high voltage end of the impulse current generator 1 is connected to the tower ground wire cross arm 3 through the injection line 2, and the high voltage end of the voltage measuring device 13 is connected to the top of the tower through the conductor 14, and the conductor 14 is supported and fixed by the fourth insulating bracket 15. The low voltage end of the impulse current generator 1 and the low voltage end of the voltage measuring device 13 are connected to the tower foot 11 through the grounding cable 10, and the injection line 2 and the grounding cable 10 are both arranged overhead.

[0043] In this embodiment, the fourth insulating support 15 is at the same height as the pole tower, so that the conductor 14 is perpendicular to the center line of the pole tower, and the distance between the fourth insulating support 15 and the pole tower is greater than the height of the pole tower. The line segment of the conductor 14 between the fourth insulating support 15 and the pole tower is horizontally arranged and its length is greater than the height of the pole tower, thereby greatly reducing the electromagnetic coupling between the pole tower and the injection line.

[0044] The current measuring device 6 is arranged at one end of the injection line 2 close to the pole tower. In specific implementation, a terminal is arranged at one end of the injection line 2 close to the pole tower, and the terminal is connected to the top of the pole tower to ensure a stable connection between the injection line 2 and the pole tower, thereby ensuring the stability of the current in the experimental loop. The current measuring device 6 can be specifically arranged at the connection between the injection line 2 and the pole tower, that is, the current measuring device 6 is connected to the terminal to collect the current signal.

[0045] In this embodiment, each tower foot 11 of the tower is connected to the low voltage end of the impulse current generator 1 and the low voltage end of the voltage measuring device through a grounding cable 10.

[0046] Specifically, in this embodiment, the grounding cable 10 is made of a copper strip or copper wire with low resistance, and the grounding cable 10 is suspended in the air through a plurality of third insulating brackets 12. The height of the grounding cable 10 from the ground is at least 50 cm.

[0047] The current measuring device 6 adopts a Rogowski coil, and the voltage measuring device adopts a voltage divider.

[0048] In this embodiment, it also includes a first insulating bracket 7 arranged on the ground and a second insulating bracket 8 arranged on the tower conductor cross arm 9. The first insulating bracket 7 is used to fix the near-ground end of the injection line 2, and the second insulating bracket 8 is used to support the injection line 2.

[0049] The distance between the first insulating support 7 and the pole tower is greater than the height of the pole tower, that is, the distance between the center line of the first insulating support 7 and the center line of the pole tower is greater than the height of the pole tower, and the first insulating support 7 is at the same height as the pole tower.

[0050] In this embodiment, the closer the injection line 2 between the first insulating support 7 and the second insulating support 8 is to the verticality of the pole tower, the smaller the electromagnetic field interference. In a specific implementation, the injection line 2 is set by the first insulating support 7 and the second insulating support 8 to ensure that the angle between the injection line 2 between the first insulating support 7 and the second insulating support 8 and the center line of the pole tower is close to 90 degrees. In a specific implementation, the injection line 2 between the first insulating support 7 and the second insulating support 8 can be set horizontally by setting the height of the first insulating support 7, that is, the injection line 2 of this section is set vertically to the center line of the pole tower to achieve minimum electromagnetic field interference.

[0051] Meanwhile, in the specific implementation, in order to increase the distance between the first insulating support 7 and the pole tower, the impulse current generator 1 should be set as far away from the pole tower as possible, and the distance between the impulse current generator 1 and the pole tower is at least greater than the height of the pole tower. In addition, in this embodiment, the angle between the injection line 2 and the conductor 14 is 90 degrees.

[0052] In this embodiment, the second insulating bracket 8 is composed of an L-shaped cylindrical insulating bracket 19 arranged on the pole tower conductor cross arm 9 and a U-shaped bolt 18 arranged at the end of the L-shaped cylindrical insulating bracket 19 away from the pole tower, and the L-shaped cylindrical insulating bracket 19 is made of epoxy resin material. The injection line 2 passes through the U-shaped bolt and is fixed. Specifically, in this embodiment, a fixed base 16 is installed on the pole tower conductor cross arm, the short end of the L-shaped cylindrical insulating bracket is locked and connected with the fixed base 16 through a clamp 17, and the U-shaped bolt 18 is arranged at the long end of the L-shaped cylindrical insulating bracket 19.

[0053] Specifically, in this embodiment, the injection line 2 uses an aluminum stranded wire with an outer layer wrapped with an insulating layer. The end of the injection line 2 close to the pole tower is fixed by a tension string 4 set on the pole tower to insulate and support the injection line 2. Specifically, in this embodiment, the tension string 4 is installed on the ground wire installation hole 5 at the top of the pole tower. The tension string 4 includes: a QP-7 ball head, an insulator string, a W-7 bowl head, a Z-7 right-angle hanging plate, a wedge-shaped wire clamp and two U-0770 hanging rings. The installation method of the tension string is as follows: a U-0770 hanging ring is installed on the ground wire installation hole 5 at the top of the pole tower, and the U-0770 hanging ring is connected to the QP-7 ball head set at the upper end of the insulator string through another U-0770 hanging ring, and the W-7 bowl head set at the lower end of the insulator string is connected to the wedge-shaped wire clamp through the Z-7 right-angle hanging plate. The wedge-shaped wire clamp is used to fix the injection line 2 and make the injection line 2 extend at least 1m to 1.5m long as a live head. The front end insulation layer of the live head is stripped to expose the wire core, i.e., the aluminum stranded wire, and the wire core is connected to the top of the pole tower through a terminal.

[0054] This embodiment also proposes an impedance data analysis method for a test loop based on tower impact impedance measurement, which includes the following steps.

[0055] S1. Set up a test loop based on tower impulse impedance measurement provided in this embodiment, and collect electrical data through the current measuring device 6 and the voltage measuring device 13. The electrical data includes current and voltage.

[0056] S2. Screening the collected electrical data to select current data and voltage data with the same time length and measurement accuracy.

[0057] Specifically, data is screened according to the current waveform and voltage waveform, and the lightning current collected by the current measuring device and the transient voltage waveform of the tower collected by the voltage measuring device are selected. It is ensured that the waveform peak value corresponding to the selected current data is within the measuring range of the current measuring device, and the waveform peak value corresponding to the voltage data is within the measuring range of the voltage measuring device, so as to ensure the measurement accuracy.

[0058] S3. Filter the screened current and the screened voltage, and then perform Fourier transform on the filtered current and voltage, analyze the frequency composition of the signal, and calculate the frequency domain impedance.

[0059] Specifically, in this embodiment, the waveform corresponding to the current data is filtered according to the bandwidth and noise of the current measuring device, and the waveform corresponding to the voltage data is filtered according to the bandwidth and noise of the voltage measuring device, specifically using low-pass filtering.

[0060] In this implementation, the waveform is subjected to Fourier transformation to determine the frequency range of the impulse signal, and a cutoff frequency of ≥10T is used for filtering to obtain a useful signal. The filtered time domain waveform is subjected to Fourier transformation and solved: the voltage and current waveforms are subjected to Fourier transformation, the frequency composition of the signal is analyzed, and the impedance value is solved in the frequency domain. The calculation formula is expressed by the following formula (1):

[0061]

[0062] Where: V(ω) is the frequency domain voltage signal, I(ω) is the frequency domain current signal.

[0063] Hereinafter, the effect of disposing the fourth insulating bracket 15 in this embodiment will be verified.

[0064] Example 1

[0065] In this embodiment, according to Figure 3 Build a simulation model.

[0066] In this embodiment, the height setting of the fourth insulating support 15 is verified. Specifically, during the simulation process, only the height of the fourth insulating support 15 is changed to change the angle between the injection line 2 and the tower.

[0067] In this embodiment, when the peak current of the impulse generator is 80.6A, the signal waveform is as follows: Fig. 9 As shown, the conductor 14 is arranged vertically with the tower. At this time, the peak value of the input tower impulse current is about 77.3A, and the signal waveform is as follows: Fig.10 When the conductor 14 and the pole tower form an angle of 60°, 45°, and 30°, respectively, the same impulse generator is used. Affected by electromagnetic coupling, the peak value of the input pole tower impulse current is 59.9A, 56.0A, and 54.1A, which are only 77.5%, 72.4%, and 69.9% of the input pole tower impulse current when the vertical setting is adopted.

[0068] Example 2

[0069] In this embodiment, according to Figure 3 Build a simulation model.

[0070] In this embodiment, the distance setting between the fourth insulating support 15 and the pole tower is verified. Specifically, during the simulation process, only the distance between the fourth insulating support 15 and the pole tower is changed.

[0071] In this embodiment, when the peak current of the impulse generator is 79.9A, when the distance between the fourth insulating support 15 and the pole tower is the same as the pole tower height, the peak current injected into the pole tower is 69.2A; when the distance between the fourth insulating support 15 and the pole tower is half the pole tower height, the peak current injected into the pole tower is 63.2A. It can be seen that when the distance between the fourth insulating support 15 and the pole tower is less than the pole tower height setting, the injection of the pole tower impulse current is greatly affected by the distance.

[0072] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A test circuit based on tower impact impedance measurement, characterized in that: include: An impulse current generator (1), an injection line (2), a current measuring device (6) and a voltage measuring device (13); The high-voltage end of the impulse current generator (1) is connected to the pole tower ground wire cross arm (3) through an injection line (2), and the high-voltage end of the voltage measuring device (13) is connected to the top of the pole tower through a conductor (14), the conductor (14) is fixed by a fourth insulating bracket (15), and the conductor (14) is arranged horizontally in a line segment between the fourth insulating bracket (15) and the pole tower, and its length is greater than the height of the pole tower; the low-voltage end of the impulse current generator (1) and the low-voltage end of the voltage measuring device (13) are both connected to the pole tower foot (11) through a grounding cable (10), and the injection line (2) and the grounding cable (10) are both arranged overhead; The current measuring device (6) is arranged at one end of the injection line (2) close to the pole tower.

2. The test circuit based on tower impact impedance measurement according to claim 1, characterized in that: Each tower foot (11) of the tower is connected to a low-voltage end of an impulse current generator (1) and a low-voltage end of a voltage measuring device (13) via a grounding cable (10).

3. The test circuit based on tower impact impedance measurement according to claim 1, characterized in that: It also comprises a first insulating support (7) arranged on the ground and a second insulating support (8) arranged on a pole tower conductor cross arm (9); the first insulating support (7) is used to fix the near-ground end of the injection line (2); the distance between the first insulating support (7) and the pole tower is greater than the height of the pole tower; the second insulating support (8) is used to support the injection line; the angle between the injection line (2) located between the first insulating support (7) and the second insulating support (8) and the pole tower center line is 90 degrees, and the angle between the injection line (2) and the conductor (14) is 90 degrees.

4. The test circuit based on tower impact impedance measurement according to claim 3, characterized in that: The second insulating support (8) comprises an L-shaped cylindrical insulating support (19) and a U-shaped bolt (18); a fixed base (16) is installed on the tower conductor cross arm (9); the L-shaped cylindrical insulating support (19) is connected to the fixed base (16); the U-shaped bolt (18) is arranged at one end of the L-shaped cylindrical insulating support (19) away from the fixed base (16); the injection line (2) passes through the U-shaped bolt (18) and is fixed.

5. The test circuit based on tower impact impedance measurement according to claim 3, characterized in that: The injection line (2) located between the first insulating support (7) and the second insulating support (8) is arranged horizontally.

6. The test circuit based on tower impact impedance measurement according to claim 1, characterized in that: A connection terminal is provided at one end of the injection line (2) close to the pole tower, and the connection terminal is connected to the top of the pole tower.

7. The test circuit based on tower impact impedance measurement according to claim 5, characterized in that: The injection line (2) is an aluminum stranded wire with an outer layer wrapped with an insulating layer.

8. The test circuit based on tower impact impedance measurement according to claim 6, characterized in that: The end of the injection line (2) close to the pole tower is fixed by a tension string (4) arranged on the pole tower, and the tension string (4) includes: a QP-7 ball head, an insulator string, a W-7 bowl head, a Z-7 right-angle hanging plate, a wedge-shaped wire clamp and two U-0770 hanging rings; the installation method of the tension string is: a U-0770 hanging ring is installed on the ground wire installation hole (5) at the top of the pole tower, the U-0770 hanging ring is connected to the QP-7 ball head arranged at the upper end of the insulator string through another U-0770 hanging ring, and the W-7 bowl head arranged at the lower end of the insulator string is connected to the wedge-shaped wire clamp through the Z-7 right-angle hanging plate, the wedge-shaped wire clamp is used to fix the injection line (2) and make the injection line (2) extend at least 1m to 1.5m long as a live head, the front end insulation of the live head is peeled off to expose the wire core, and the wire core is connected to the top of the pole tower through a wiring terminal.

9. The test circuit based on tower impact impedance measurement according to claim 1, characterized in that: The grounding cable (10) is made of a copper strip or a copper wire, and the grounding cable (10) is suspended in the air through a plurality of third insulating brackets (12); the height of the grounding cable (10) is at least 50 cm above the ground; The current measuring device (6) adopts a Rogowski coil, and the voltage measuring device adopts a voltage divider.

10. An impedance data analysis method for a test loop based on tower impact impedance measurement, characterized in that: The following steps are involved: S1. Setting a test circuit based on tower impact impedance measurement as described in any one of claims 1 to 9, collecting electrical data through a current measuring device (6) and a voltage measuring device (13), the electrical data including current and voltage; S2, screened current data and voltage data with the same time length and measurement accuracy; S3. Filter the screened current and the screened voltage, and then perform Fourier transform on the filtered current and voltage, analyze the frequency composition of the signal, and calculate the frequency domain impedance.

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