Online cable fault positioning method

Abstract

The invention relates to an online cable fault positioning method, which constructs a set of fault positioning system capable of carrying out fault positioning and fault type judgment on online cable faults, reflects fault information by means of a spread spectrum time domain reflection method, designs an isolated coupling magnetic ring, and improves the fault positioning accuracy. Performing non-contact coupling injection and receiving on a detection signal to realize non-contact fault detection; the method has the advantages that the method is simple, online detection is achieved, and uninterruptible power failure positioning is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of cable fault locating, and in particular relates to an online cable fault locating method. Background Art

[0002] With the development of society, the scope of power system laying has greatly increased. At the same time, cables are subject to aging corrosion and external force damage, which lead to circuit breakage, short circuit and damage. At present, most cable detection uses cable offline detection, that is, troubleshooting after power failure, which is time-consuming and will cause losses to social production and residents' lives. Therefore, it is very necessary to provide an online cable fault location method that is simple, realizes online detection, and realizes uninterrupted power supply fault location. Summary of the invention

[0003] 1. Technical issues

[0004] In view of the above-mentioned existing technical status, this application mainly addresses the following technical problems:

[0005] 1. Currently, most cable detection methods are offline cable detection;

[0006] 2. Offline detection is to troubleshoot after power failure, which is time-consuming and will cause losses to social production and residents' lives.

[0007] (II) Technical solution

[0008] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide an online cable fault locating method which is simple in method, realizes online detection and realizes uninterrupted power supply fault locating.

[0009] The object of the present invention is achieved by: a method for locating an online cable fault, the method comprising the following steps:

[0010] Step 1: Selection of detection signal;

[0011] Step 2: Generation of detection signal;

[0012] Step 3: The modulated signal is transmitted for detection to achieve isolated detection of the online cable;

[0013] Step 4: Reflection signal processing.

[0014] Furthermore, the selection of the detection signal in step 1 is specifically as follows: a pseudo-random (PN) sequence is used to perform multiplication modulation with sinusoidal signals of frequencies of 1 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz to select a modulation signal.

[0015] Furthermore, the generation of the detection signal in step 2 is specifically as follows: a 32-bit M sequence is generated by using a 5-stage shift register with linear feedback, and the 32-bit M sequence is multiplied and modulated with a sinusoidal signal to generate a random sequence signal.

[0016] Furthermore, the step 3 is specifically as follows: the m sequence is modulated with sinusoidal signals of 1 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz respectively, and during fault detection, the modulated signals are transmitted and detected in sequence from high frequency to low frequency.

[0017] Furthermore, the reflected signal processing in step 4 is specifically: using a cross-correlation operation, x1(t) is the transmitted signal, x2(t) is the reflected signal, and τ is the delay time of the reflected signal: Use x1(t) and x2(t) to represent the transmitted signal s1(t) and the reflected signal s2(t+τ) for unification; perform cross-correlation operation on the transmitted signal and the reflected signal: Rx1x2(τ)=∫[x1(t)*x2(t)]dt, Rx1x2(τ) function is the cross-correlation operation of x1(t) and x2(t), i.e., convolution integral. An obvious peak point will appear in the waveform at the moment t=τ, and the fault location and fault type information can be obtained according to the peak point position, size and polarity.

[0018] An online cable fault locating system executes the online cable fault locating method as described above, the system comprises an online signal isolation coupling injection device, the online signal isolation coupling injection device comprises a non-contact isolation inductive coupler connector and an inductive non-contact coupler, the non-contact isolation inductive coupler connector connects a signal transmitting and receiving device; the inductive non-contact coupler is an inductive coupler, and the inductive coupler adopts a caliper structure.

[0019] Furthermore, the contactless isolated inductive coupler connector is installed outside the shielding shell, and the inside of the shielding shell is an annular magnetic core.

[0020] Furthermore, the inductive coupler includes: a shielding layer, a cable winding located inside the shielding layer, an annular magnet located inside the cable winding, and a coaxial connector electrically connected to the cable winding.

[0021] Furthermore, the coaxial connector is the input and output end of signal transmission; the annular magnet adopts a stacking design and is composed of six layers of annular magnetic cores.

[0022] Furthermore, the system also includes a detection signal generation and processing circuit module, which includes an FPGA integrated chip, a digital-to-analog conversion module and an analog-to-digital conversion module; the FPGA integrated chip is used to generate a detection signal; the digital-to-analog conversion module is an AD9708 conversion module, which is used to perform digital-to-analog conversion on the digital signal and inject it into the cable after amplification; the analog-to-digital conversion module is an AD9481 conversion module, which is used to collect the reflected signal and transmit the data to the FPGA integrated chip for processing.

[0023] (III) Beneficial effects

[0024] 1. The present invention relates to a traveling wave reflection method based on a pseudo-random sequence and a sinusoidal signal modulated by binary phase shift keying (BPSK) to determine the cable fault location;

[0025] 2. The present invention provides an inductive non-contact coupler for isolated signal injection and acquisition, so as to realize fault location without power failure of the cable;

[0026] 3. The present invention can detect cable faults online and provide fault location data in real time without power outage, making it convenient for staff to carry out timely repairs and preventive maintenance to ensure stable operation of the cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the time domain sequence diagram of the M sequence of the present invention.

[0028] Figure 2 It is a schematic diagram of the detection signal generated by the sine wave and m-sequence modulation of the present invention.

[0029] Figure 3 This is a schematic diagram of the installation of the non-contact isolation injection magnetic ring of the present invention.

[0030] Figure 4 It is a schematic diagram of the non-contact isolation injection magnetic ring structure of the present invention.

[0031] In the figure: 3-1, non-contact isolation inductive coupler connector 3-2, annular magnetic core 3-3, shielding shell 4, inductive non-contact coupler 4-1, coaxial connector 4-2, cable winding 4-3, shielding layer 4-4, annular magnet. DETAILED DESCRIPTION

[0032] The purpose of the present invention is to construct a fault location method and system which can determine the fault branch of a T-type multi-branch cable fault, accurately locate the fault, and determine the fault type.

[0033] The present invention is further described below in conjunction with embodiments and / or drawings.

[0034] Example 1

[0035] like Figure 1-4 As shown, a method for locating an online cable fault comprises the following steps:

[0036] Step 1: Selection of detection signal;

[0037] Step 2: Generation of detection signal;

[0038] Step 3: The modulated signal is transmitted for detection to achieve isolated detection of the online cable;

[0039] Step 4: Reflection signal processing.

[0040] The selection of the detection signal in step 1 is specifically as follows: a pseudo-random (PN) sequence is used to perform multiplication modulation with sinusoidal signals of frequencies 1 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz, and a modulation signal is selected.

[0041] The generation of the detection signal in step 2 is specifically as follows: a 32-bit M sequence is generated by using a 5-stage shift register with linear feedback, and the 32-bit M sequence is multiplied and modulated with a sinusoidal signal to generate a random sequence signal.

[0042] The step 3 is specifically as follows: the m sequence is modulated with sinusoidal signals of 1 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz respectively, and during fault detection, the modulated signals are transmitted and detected in sequence from high frequency to low frequency.

[0043] The reflected signal processing in step 4 is specifically: using cross-correlation operation, x1(t) is the transmitted signal, x2(t) is the reflected signal, and τ is the delay time of the reflected signal: Use x1(t) and x2(t) to represent the transmitted signal s1(t) and the reflected signal s2(t+τ) for unification; perform cross-correlation operation on the transmitted signal and the reflected signal: Rx1x2(τ)=∫[x1(t)*x2(t)]dt, Rx1x2(τ) function is the cross-correlation operation of x1(t) and x2(t), i.e., convolution integral. An obvious peak point will appear in the waveform at the moment t=τ, and the fault location and fault type information can be obtained according to the peak point position, size and polarity.

[0044] The present invention is an online cable fault location method. In use, the present invention relates to a traveling wave reflection method based on binary phase shift keying (BPSK) modulation of a pseudo-random sequence and a sinusoidal signal to determine the cable fault location; the present invention formulates an inductive non-contact coupler to perform isolated signal injection and collection, thereby realizing fault location without power failure of the cable; the present invention can detect online cable faults and provide fault location data in real time without power failure, thereby facilitating timely repairs and preventive maintenance by staff and ensuring stable operation of the cable; the present invention has the advantages of simple method, realization of online detection, and realization of fault location without power failure.

[0045] Example 2

[0046] like Figure 1-4 As shown, an online cable fault locating system executes the online cable fault locating method as described above, with the purpose of constructing a fault locating system that can locate online cable faults and determine the fault type, reflects fault information based on the spread spectrum time domain reflectometry, designs an isolated coupling magnetic ring, performs non-contact coupling injection and reception of detection signals, and realizes non-contact fault detection. Specifically, the system includes an online signal isolation coupling injection device, the online signal isolation coupling injection device includes a non-contact isolation inductive coupler connector and an inductive non-contact coupler, the non-contact isolation inductive coupler connector connects a signal transmitting and receiving device; the inductive non-contact coupler is an inductive coupler, and the inductive coupler adopts a caliper structure.

[0047] In the present invention, the inductive non-contact coupler: a nickel-zinc ferrite magnetic ring with high magnetic permeability is selected to install high magnetic permeability magnetic rings on the outside of the signal transmission line and the cable to be tested respectively and serve as the primary and secondary sides of the coupling structure, which can realize bidirectional coupling transmission of high-frequency signals and realize non-contact online isolation; in order to solve the problems of attenuation and signal waveform distortion in the coupling process, the nickel-zinc ferrite material is selected.

[0048] The contactless isolation inductive coupler connector is installed outside the shielding shell, and the inside of the shielding shell is a ring-shaped magnetic core.

[0049] The inductive coupler comprises: a shielding layer, a cable winding located inside the shielding layer, a ring magnet located inside the cable winding, and a coaxial connector electrically connected to the cable winding.

[0050] The coaxial connector is the input and output end of signal transmission; the annular magnet adopts a stacking design and is composed of six layers of annular magnetic cores.

[0051] In the present invention, the signal transmission cable is equivalent to the primary side of the transformer in the inductive coupler, and the cable is used as the secondary side to achieve bidirectional coupling of high-frequency signals; L coil is the self-inductance of the signal transmitting coil, Lcable is the self-inductance of the cable, M is the mutual inductance of the two; E m is the induced electromotive force; u is the induced voltage value of the secondary cable; since the power frequency is 50Hz, the cable side is equivalent to no current for the coupling mechanism, and the induced voltage of the cable can be considered to be equal to the induced electromotive force; L coil is the effective value of the current of the signal transmitting coil; The voltage value of the induced signal on the cable side depends on the mutual inductance between the signal transmitting coil and the cable, as well as the current value of the transmitting signal itself. Therefore, the mutual inductance can be designed to be as large as possible. The coupling device is equivalent to a transformer structure, so the self-inductance and mutual inductance are related functions of the magnetic permeability of the magnetic core, which can be expressed as: N1 is the number of turns of the primary coil winding; N2 is the number of turns of the secondary cable side coil winding; μ m is the relative magnetic permeability of the core; R0 is μ m =1 when the magnetic resistance value; the number of turns of the primary and secondary coils is 1, and the nickel-zinc ferrite material with a saturation magnetic density of 290mT is used. Since the coupler is in a non-saturated working state when the maximum current passing through the cable is 10A, its minimum inner diameter meets the requirement of being greater than 5mm, and the relative magnetic permeability is 1500; the core material is HF70.

[0052] The system of the present invention can realize separate detection of each branch of the online T-type branch cable, without power off and using multiple sets of equipment to detect different branches. It only needs to perform online isolation injection of signals on one end side, and through wireless relay switch control, separate detection of different branches can be realized, thereby improving the efficiency of multi-branch cable fault detection.

[0053] The system also includes a detection signal generation and processing circuit module, which includes an FPGA integrated chip, a digital-to-analog conversion module and an analog-to-digital conversion module; the FPGA integrated chip is used to generate a detection signal; the digital-to-analog conversion module is an AD9708 conversion module, which is used to perform digital-to-analog conversion on a digital signal and inject it into the cable after amplification; the analog-to-digital conversion module is an AD9481 conversion module, which is used to collect the reflected signal and transmit the data to the FPGA integrated chip for processing.

[0054] Aiming at the problems that it is difficult to detect faults in online multi-branch cables and it is difficult to identify faulty branches, the present invention proposes to use an inductive coupler to couple, inject and collect high-frequency signals for isolation, and designs a shielded magnetic ring to selectively pass signals from different branches of the T-shaped branch cable, thereby realizing separate detection of specific branch faults in the multi-branch cable. In the fault detection of the T-shaped multi-branch cable, there is no need to use multiple sets of equipment, and there is no need to invasively destroy the cable at the branch. The present invention can realize isolated detection of online cables without power off, thereby improving the fault detection efficiency of the multi-branch cable.

[0055] The present invention is an online cable fault location system. In use, the present invention relates to a traveling wave reflection method based on binary phase shift keying (BPSK) modulation of a pseudo-random sequence and a sinusoidal signal to determine the cable fault location; the present invention formulates an inductive non-contact coupler to perform isolated signal injection and collection, thereby realizing fault location without power failure of the cable; the present invention can detect online cable faults and provide fault location data in real time without power failure, thereby facilitating staff to perform timely emergency repairs and preventive maintenance, thereby ensuring stable operation of the cable; the present invention has the advantages of simple method, realization of online detection, and realization of fault location without power failure.

Claims

1. An online cable fault location method, characterized in that: The method comprises the following steps: Step 1: Selection of detection signal; Step 2: Generation of detection signal; Step 3: The modulated signal is transmitted for detection to achieve isolated detection of the online cable; Step 4: Reflection signal processing.

2. An online cable fault location method according to claim 1, characterized in that: The selection of the detection signal in step 1 is specifically as follows: a pseudo-random (PN) sequence is used to perform multiplication modulation with sinusoidal signals of frequencies 1 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz, and a modulation signal is selected.

3. An online cable fault location method according to claim 1, characterized in that: The generation of the detection signal in step 2 is specifically as follows: a 32-bit M sequence is generated by using a 5-stage shift register with linear feedback, and the 32-bit M sequence is multiplied and modulated with a sinusoidal signal to generate a random sequence signal.

4. An online cable fault location method according to claim 1, characterized in that: The step 3 is specifically as follows: the m sequence is modulated with sinusoidal signals of 1 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz respectively, and during fault detection, the modulated signals are transmitted and detected in sequence from high frequency to low frequency.

5. The method for locating an online cable fault according to claim 1, characterized in that: The reflected signal processing in step 4 is specifically: using cross-correlation operation, x1(t) is the transmitted signal, x2(t) is the reflected signal, and τ is the delay time of the reflected signal: Use x1(t) and x2(t) to represent the transmitted signal s1(t) and the reflected signal s2(t+τ) for unification; perform cross-correlation operation on the transmitted signal and the reflected signal: Rx1x2(τ)=∫[x1(t)*x2(t)]dt, Rx1x2(τ) function is the cross-correlation operation of x1(t) and x2(t), i.e., convolution integral. An obvious peak point will appear in the waveform at the moment t=τ, and the fault location and fault type information can be obtained according to the peak point position, size and polarity.

6. An online cable fault locating system, executing the online cable fault locating method according to any one of claims 1 to 5, characterized in that: The system comprises an online signal isolation coupling injection device, which comprises a contactless isolation inductive coupler connector and an inductive contactless coupler, wherein the contactless isolation inductive coupler connector is connected to a signal transmitting and receiving device; the inductive contactless coupler is an inductive coupler, and the inductive coupler adopts a caliper structure.

7. An online cable fault location system as claimed in claim 6, characterized in that: The contactless isolation inductive coupler connector is installed outside the shielding shell, and the inside of the shielding shell is a ring-shaped magnetic core.

8. An online cable fault location system as claimed in claim 6, characterized in that: The inductive coupler comprises: a shielding layer, a cable winding located inside the shielding layer, a ring magnet located inside the cable winding, and a coaxial connector electrically connected to the cable winding.

9. An online cable fault location system as claimed in claim 8, characterized in that: The coaxial connector is the input and output end of signal transmission; the annular magnet adopts a stacking design and is composed of six layers of annular magnetic cores.

10. An online cable fault location system according to claim 1, characterized in that: The system also includes a detection signal generation and processing circuit module, which includes an FPGA integrated chip, a digital-to-analog conversion module and an analog-to-digital conversion module; the FPGA integrated chip is used to generate a detection signal; the digital-to-analog conversion module is an AD9708 conversion module, which is used to perform digital-to-analog conversion on a digital signal and inject it into the cable after amplification; the analog-to-digital conversion module is an AD9481 conversion module, which is used to collect the reflected signal and transmit the data to the FPGA integrated chip for processing.

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