Non-intrusive signal injection cable grounding loop detection device and abnormal point positioning method

Abstract

The invention discloses a non-intrusive signal injection cable grounding loop detection device and an abnormal point positioning method, and belongs to the technical field of power equipment state detection, the detection principle is based on a time domain reflectometer principle, and the abnormal point of the cable grounding loop is determined by measuring the reflection condition of an injected signal in the cable grounding loop. And detecting and positioning an abnormal point in the cable grounding loop. In order to realize non-intrusive detection, the device disclosed by the invention realizes non-contact injection and measurement of signals by utilizing a capacitive coupling effect, and meanwhile, in order to control directional propagation of pulses in a cable grounding loop, a choke device is adopted near an injection point to control the propagation direction of the injected signals. According to the device, through a non-intrusive detection mode, detection and positioning of abnormal points in a cable grounding loop in operation are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of power equipment status detection, and more particularly to a cable grounding loop detection device and an abnormal point positioning method using non-invasive signal injection. Background Art

[0002] Production and life in modern society mainly rely on electricity to provide energy sources. Ensuring the safety and reliability of power supply is an important part of national security construction. Cable lines are one of the main carriers of power supply, especially in load centers such as cities, factories and mines, where cables are widely used. However, due to the influence of construction technology and external factors during operation, the grounding loop of the cable has abnormal grounding and poor grounding. This causes abnormal induced current and induced voltage in the metal shielding layer of the cable, resulting in overheating or overvoltage of the metal shielding layer, which endangers the health of the cable. Therefore, in the daily operation and maintenance and inspection of the cable, detecting abnormal conditions in the cable grounding loop and locating abnormal points are one of the important measures to ensure the safe and stable operation of the cable.

[0003] Existing cable ground loop detection methods mainly include anomaly loop current detection, ground voltage test, loop resistance test, leakage current test, ground impedance test and insulation resistance test. Among the above methods, except for the ground impedance test technology, other technologies are usually unable to locate abnormal grounding points. At the same time, the existing detection methods use contact detection and even require power outage detection. Therefore, the above detection methods not only have certain risks, but the detection is also limited by the power outage time and cannot be carried out in daily operation and maintenance.

[0004] Therefore, how to provide a cable ground loop detection device and an abnormal point locating method with non-invasive signal injection is a problem that those skilled in the art need to solve urgently. Summary of the invention

[0005] In view of this, the present invention provides a cable grounding loop detection device and an abnormal point locating method with non-invasive signal injection. Based on the existing reflectometer principle, by adopting non-invasive signal injection and detection technology, as well as traveling wave blocking technology, non-invasive detection and positioning of abnormal points in the cable grounding loop are achieved.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A non-intrusive signal injection cable ground loop detection device comprises: a signal injection and measurement device and a choke device;

[0008] The signal injection and measurement device includes: a flexible electrode plate, a signal generating unit, a measuring unit and a signal connecting line. The flexible electrode plate is connected to the signal generating unit via the signal connecting line, and the measuring unit is connected to the signal generating unit, so as to obtain the injection signal applied to the flexible electrode plate and the reflected signal coupled by the electrode plate.

[0009] Preferably, the signal generating unit comprises a matching resistor and a signal generator connected in sequence, the positive pole of the signal generator is connected to one end of the matching resistor, and the negative pole of the signal generator is grounded; the other end of the matching resistor is connected to the flexible electrode plate through the signal connecting line.

[0010] Preferably, the measuring unit includes a data collector and a sampling resistor, the data collector is connected to both ends of the sampling resistor to measure and record the voltage across the sampling resistor; one end of the sampling resistor is grounded, and the other end of the sampling resistor is connected to the flexible electrode plate.

[0011] Preferably, the data collector output is connected to a host computer for transmitting the measurement results for data analysis by the host computer.

[0012] Preferably, the choke device is an annular caliper composed of two semicircular magnetic rings.

[0013] On the other hand, the present invention provides a method for locating abnormal points in a cable grounding loop by non-invasive signal injection, which uses the above-mentioned non-invasive signal injection cable grounding loop detection device to collect the injection signal applied to the flexible electrode plate and the reflected signal coupled by the electrode plate, and uses an adaptive matching filtering method to identify and locate abnormal points in the cable grounding loop.

[0014] Preferably, an adaptive matched filtering method is used to identify and locate abnormal points in the cable grounding loop, including:

[0015] For the reflection signals collected at different times, an adaptive matched filter is used to perform adaptive matched filtering calculation on the reflection signals;

[0016] When an extreme value exists in the result of the adaptive matched filtering of the measurement signal, it is determined that a reflection signal caused by an abnormal point exists;

[0017] According to the positive and negative characteristics of the extreme value, the type of the abnormal point in the cable grounding loop is judged. If the extreme value is positive, the cable grounding loop has a defect of poor grounding and large grounding resistance; if the extreme value is negative, it means that the cable has a defect of outer sheath damage, resulting in a new abnormal grounding point;

[0018] The position of the abnormal point in the cable grounding loop is determined according to the time corresponding to the extreme value.

[0019] Preferably, for the reflection signals at different times, the calculation formula of the adaptive matched filter is as follows:

[0020]

[0021] In the formula, H ( ω ) is the injected pulse spectrum function; γ c is the propagation constant in the cable ground loop; l p It is the distance between the abnormal point of the cable grounding loop and the measuring point of the device.

[0022] Preferably, adaptive matched filtering is used to calculate the measurement signal, and the calculation formula is as follows:

[0023] V p (t) = ∫V ( τ ) h t( t-τ ) dτ

[0024] In the formula, the function h t( t ) is the adaptive matched filter H t( ω ) Corresponding time domain expression; Function V(t) is the reflection signal in the cable ground loop collected by the measuring device; V p ( t ) is the adaptive matched filtering result of the reflected signal; τ is the integral variable.

[0025] Preferably, the calculation formula for the abnormal point position in the cable grounding loop is as follows:

[0026]

[0027] Where, t p is the moment corresponding to the extreme point, v p is the wave velocity of the cable ground loop.

[0028] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a non-invasive signal injection cable grounding loop detection device and an abnormal point positioning method. First, signal injection and measurement are achieved through non-invasive technology to ensure that the detection process is safe and convenient, and to avoid interference with cable operation. Secondly, the device adopts a signal directional injection method, which reduces the difficulty of signal analysis and significantly improves the reliability of abnormality detection and the positioning accuracy of abnormal points. Furthermore, by combining the reflectometer principle with non-invasive detection technology and traveling wave blocking technology, effective detection and positioning of abnormal points in the cable grounding loop are achieved, bringing technological innovation to the field of cable detection. In addition, the device supports daily operation and maintenance, and can perform detection at any time without affecting the operation of the cable, which helps to timely discover and deal with potential problems and reduce operation and maintenance costs. Finally, the present invention has broad application prospects in engineering practice, is of great significance for improving the safety and reliability of power grids, and shows important engineering practice value and promotion and application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 It is a principle structure diagram of the device of the present invention;

[0031] Figure 2 It is a schematic diagram of the installation of the device of the present invention;

[0032] Figure 3 is the measurement result of the device in a specific embodiment. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The embodiment of the present invention discloses a cable ground loop detection device with non-intrusive signal injection, such as Figure 1 As shown, it includes: a signal injection and measurement device A and a choke device B;

[0035] The signal injection and measurement device A includes: a flexible electrode plate P1, a signal generating unit S, a measuring unit M and a signal connecting line C1. The flexible electrode plate P1 is connected to the signal generating unit S through the signal connecting line C1, and the measuring unit M is connected to the signal generating unit S, so as to obtain the injection signal applied to the flexible electrode plate P1 and the reflected signal coupled by the electrode plate.

[0036] Among them, the flexible electrode plate P1 is a bendable rectangular flat electrode, and the surface of the flat electrode is covered with insulating rubber to protect the electrode. The electrode is connected to the lead wire, which is connected to the connector outside the flexible electrode through the insulating rubber, and then connected to other devices. The connector uses a standard N-type coaxial connector. When installing, the flexible electrode plate P1 needs to be wrapped and tightly attached to the surface of the cable, naturally bend with the cable surface, and be fixed to the cable by the surface binding belt.

[0037] Furthermore, the installation position of the choke device is near the flexible electrode plate P1, and its installation direction is determined by the position of the cable segment CA to be tested. If the cable segment CA to be tested is on the left side of the flexible electrode plate P1, the choke device B is installed on the right side of the flexible electrode plate P1; vice versa.

[0038] Specifically, the signal generating unit S includes a matching resistor R1 and a signal generator S1 connected in sequence, the positive electrode of the signal generator S1 is connected to one end of the matching resistor R1, and the negative electrode of the signal generator S1 is grounded; the other end of the matching resistor R1 is connected to the flexible electrode plate P1 through a signal connection line C1. The signal generator S1 is used to generate the required injection signal, and the matching resistor R1 is used to adjust the coupling characteristics of the injection device to ensure that the signal can be coupled to the cable metal shielding layer in a maximum power manner.

[0039] Furthermore, the other end of the matching resistor R1 is connected to a standard N-type coaxial connector through a signal line C1 , and the N-type coaxial connector and the N-type coaxial connector on the flexible electrode board form a pair of mutually matching N-type coaxial connectors.

[0040] Furthermore, the measuring unit M includes a data collector M1 and a sampling resistor R2. The data collector M1 is connected to both ends of the sampling resistor R2 to measure and record the voltage across the sampling resistor R2. The sampling resistor R2 is used to capture the injection signal applied to the flexible electrode plate P1 and the reflected signal coupled by the electrode plate. One end of the sampling resistor R2 is grounded, and the other end is connected to one end of the matching resistor R1 connected to the N-type connector.

[0041] In another embodiment, the output of the data collector M1 is connected to a host computer for transmitting the measurement results for data analysis by the host computer.

[0042] In another embodiment, the choke device B is a ring caliper composed of two semicircular magnetic rings. The material of the magnetic ring is nickel-zinc ferrite, which has a high saturation magnetic induction intensity, a large relative magnetic permeability at high frequency, and a good suppression effect on the injected high-frequency signal. When in use, the caliper is opened, the cable passes through the ring of the caliper, and then the caliper is closed to make the two petals of the magnetic ring tightly closed.

[0043] On the other hand, the present invention provides a method for locating abnormal points in a cable grounding loop by non-invasive signal injection, using the above-mentioned non-invasive signal injection cable grounding loop detection device to collect the injection signal applied to the flexible electrode plate and the reflected signal coupled by the electrode plate, and using an adaptive matching filtering method to identify and locate abnormal points in the cable grounding loop. When the pulse signal propagates inside the cable, due to the influence of the cable shielding layer and the soil resistivity, the pulse signal attenuates and disperses, causing the waveform of the pulse signal to change. The adaptive matching filtering method is to consider the influence of the waveform change, use an adaptive matching filter for the reflection signals collected at different times, and perform matched filtering calculations on the reflection signals.

[0044] Furthermore, an adaptive matched filtering method is used to identify and locate abnormal points in the cable grounding loop, including:

[0045] For the reflection signals collected at different times, an adaptive matched filter is used to perform adaptive matched filtering calculation on the reflection signals;

[0046] When there is an extreme value in the result of matched filtering of the measurement signal, it is determined that there is a reflection signal caused by an abnormal point;

[0047] According to the positive and negative characteristics of the extreme value, the type of abnormal point in the cable grounding loop is determined. If the extreme value is positive, the cable grounding loop has a defect of poor grounding and large grounding resistance; if the extreme value is negative, it means that the cable has a defect of outer sheath damage, resulting in a new abnormal grounding point;

[0048] The location of the abnormal point in the cable grounding loop is determined based on the time corresponding to the extreme value.

[0049] Specifically, for the reflected signals at different times, the calculation formula of the adaptive matched filter is as follows:

[0050]

[0051] In the formula, H ( ω ) is the injected pulse spectrum function, which can be used to analyze the injected pulse signal h ( t ) Perform Fourier transform to get; γ cis the propagation constant in the cable grounding loop, which is calculated by the finite element method based on the structural parameters of the cable and the soil resistivity. p It is the distance between the abnormal point of the cable grounding loop and the measuring point of the device.

[0052] Preferably, adaptive matched filtering is used to calculate the measurement signal, and the calculation formula is as follows:

[0053] V p (t) = ∫V(τ)h t (t-τ)dτ

[0054] In the formula, the function h t( t ) is the adaptive matched filter H t( ω ) The corresponding time domain expression can be obtained by inverse Fourier transform; the function V(t) is the reflected signal in the cable grounding loop collected by the device; V p ( t ) is the adaptive matched filtering result of the reflected signal; the variable τ is the integral variable.

[0055] Specifically, the calculation formula for the abnormal point position in the cable grounding loop is as follows:

[0056]

[0057] Where, t p is the time corresponding to the extreme point, and the measured start time of the injection pulse is taken as the timing 0, v p is the cable ground loop wave velocity.

[0058] The present invention provides a non-intrusive signal injection cable ground loop detection device, which is installed as follows when in use: Figure 2 The cable model in the embodiment is FY-YJLW03-Z 127 / 220kV1×2500mm 2 ,according to Figure 2 The topology shown in the figure is used to install the flexible electrode board and the choke device, and connect the flexible electrode board to the detection host. The signal generator is set to generate a pulse signal with a rising edge of 50ns, a falling edge of 50ns, and a pulse width of 200ns. The reflected waveform of the cable ground loop is as follows: Figure 3 As shown. By analyzing the reflected waveform, it can be seen that there is an abnormal grounding point in the cable grounding loop at a distance of 232m from the measurement point. After on-site investigation, it was found that the outer sheath of the cable was damaged at this location, resulting in the metal shielding layer of the cable being connected to the metal of the cable bracket, resulting in abnormal grounding. The distance measured on site was 230m. Compared with the positioning results, the positioning error of this device was 0.86%.

[0059] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0060] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A cable ground loop detection device with non-intrusive signal injection, characterized in that: include: Signal injection and measurement devices and choke devices; The signal injection and measurement device includes: a flexible electrode plate, a signal generating unit, a measuring unit and a signal connecting line. The flexible electrode plate is connected to the signal generating unit via the signal connecting line, and the measuring unit is connected to the signal generating unit, so as to obtain the injection signal applied to the flexible electrode plate and the reflected signal coupled by the electrode plate.

2. A cable ground loop detection device with non-intrusive signal injection according to claim 1, characterized in that: The signal generating unit comprises a matching resistor and a signal generator connected in sequence, the positive electrode of the signal generator is connected to one end of the matching resistor, and the negative electrode of the signal generator is grounded; the other end of the matching resistor is connected to the flexible electrode plate through the signal connecting line.

3. The cable ground loop detection device of non-intrusive signal injection according to claim 1, characterized in that: The measuring unit comprises a data collector and a sampling resistor. The data collector is connected to both ends of the sampling resistor to measure and record the voltage across the sampling resistor. One end of the sampling resistor is grounded, and the other end of the sampling resistor is connected to the flexible electrode plate.

4. The cable ground loop detection device of non-intrusive signal injection according to claim 3, characterized in that: The data acquisition device output is connected to a host computer for transmitting the measurement results for data analysis by the host computer.

5. The cable ground loop detection device of non-intrusive signal injection according to claim 1, characterized in that: The choke device is an annular caliper composed of two semicircular magnetic rings.

6. A method for locating abnormal points in a cable grounding loop by non-invasive signal injection, characterized in that: A cable grounding loop detection device with non-invasive signal injection as described in any one of claims 1 to 5 is used to collect the injection signal applied to the flexible electrode plate and the reflected signal coupled by the electrode plate, and an adaptive matching filtering method is used to identify and locate abnormal points in the cable grounding loop.

7. The method for locating abnormal points in a cable grounding loop by non-intrusive signal injection according to claim 6, characterized in that: Adaptive matching filtering is used to identify and locate abnormal points in the cable grounding loop, including: For the reflection signals collected at different times, an adaptive matched filter is used to perform adaptive matched filtering calculation on the reflection signals; When there is an extreme value in the result of the adaptive matched filtering of the measurement signal, it is determined that there is a reflection signal caused by an abnormal point; According to the positive and negative characteristics of the extreme value, the type of the abnormal point in the cable grounding loop is judged. If the extreme value is positive, the cable grounding loop has a defect of poor grounding and large grounding resistance; if the extreme value is negative, it means that the cable has a defect of outer sheath damage, resulting in a new abnormal grounding point; The position of the abnormal point in the cable grounding loop is determined according to the time corresponding to the extreme value.

8. The method for locating abnormal points in a cable grounding loop by non-intrusive signal injection according to claim 7, characterized in that: For the reflected signals at different times, the calculation formula of the adaptive matched filter is as follows: Where H(ω) is the injected pulse spectrum function; γ c is the propagation constant in the cable ground loop; l p It is the distance between the abnormal point of the cable grounding loop and the measuring point of the device.

9. The method for locating abnormal points in a cable grounding loop by non-intrusive signal injection according to claim 7, characterized in that: Adaptive matched filtering is used to calculate the measured signal. The calculation formula is as follows: V p (t)=∫V(τ)h t (t-τ)dτ In the formula, the function h t (t) is the adaptive matched filter H t (ω) corresponding to the time domain expression; the function V(t) is the reflection signal in the cable grounding loop collected by the measuring device; V p (t) is the adaptive matched filtering result of the reflected signal; τ is the integral variable.

10. The method for locating abnormal points in a cable grounding loop by non-intrusive signal injection according to claim 8, characterized in that: The calculation formula for the abnormal point position in the cable grounding loop is as follows: Where, t p is the moment corresponding to the extreme point, v p is the wave velocity of the cable ground loop.

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