Cable positioning method and system based on partial discharge signal arrival time identification

Abstract

The invention relates to a cable positioning method and system based on partial discharge signal arrival time identification, and the method comprises the steps: employing a high-frequency current sensor with a time service function, and sensing a high-frequency partial discharge signal of the partial discharge of a cable grounding lower lead in a single-end or double-end connection mode; the high-frequency partial discharge signals are conditioned and collected; identifying the arrival time of the partial discharge signal from the collected high-frequency partial discharge signal based on a signal energy criterion; and positioning a cable defect position according to the cable length and the signal arrival time difference. Compared with the prior art, power failure of the cable is not needed, fault point positioning is achieved under the condition that normal operation of the cable is not affected, automatic implementation can be achieved, manual intervention errors are reduced, and the accuracy and efficiency of power cable fault point positioning are greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cable fault location, and in particular to a cable location method and system based on partial discharge signal arrival time recognition. Background Art

[0002] Power cables have the advantages of excellent insulation performance, easy installation, no ground space occupation, high power supply reliability, etc. In recent years, they have gradually replaced overhead lines to become the main way of power transmission in cities, and their proportion in the entire power system transmission line has increased year by year. The commonly used cable test methods currently include AC and DC withstand voltage tests, ultra-low frequency withstand voltage tests, and partial discharge and dielectric loss measurements based on oscillating wave voltage. The above traditional methods are only applicable to offline detection of cables and cannot be applied to the status monitoring of cables in operation.

[0003] At the same time, since cables are usually buried underground or laid in cable tunnels, locating their fault points can help cable operation and maintenance managers quickly find the defect location and formulate reasonable maintenance strategies to ensure the stability of cable operation and the reliability of power supply of the power grid. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art cable fault location positioning methods including the bridge method and the pulse method. The above methods have certain limitations in practical applications: the measurement accuracy of the bridge method is subject to the influence of the guide wire, and it is not suitable for flashover or high-resistance faults, and the low-voltage pulse reflection method cannot be used for flashover faults or high-resistance faults; at the same time, the above two methods are power outage test items, which affect the normal operation of the cable, and provide a cable positioning method and system based on partial discharge signal arrival time recognition.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A cable positioning method based on partial discharge signal arrival time recognition comprises the following steps:

[0007] A high-frequency current sensor with a timing function is used to sense the high-frequency partial discharge signal of the partial discharge of the cable grounding lead in a single-end or double-end connection mode;

[0008] Condition and collect high-frequency partial discharge signals;

[0009] Based on the signal energy criterion, the arrival time of the partial discharge signal is identified from the collected high-frequency partial discharge signal;

[0010] The cable defect position is located according to the cable length and the signal arrival time difference. The signal arrival time difference is the arrival time difference between the high-frequency partial discharge signal and its reflected signal in a single-end connection mode, and is the arrival time difference of the high-frequency partial discharge signal generated by the fault current received by the high-frequency current sensors at both ends in a double-end connection mode.

[0011] Furthermore, the frequency range of the high-frequency current sensor is 16kHz to 50MHz.

[0012] Furthermore, the high-frequency current sensor has a built-in iron core, a coil, a Beidou timing module and a power supply module. The coil is wrapped around the outside of the iron core, and the high-frequency current sensor is installed through the core at the cable terminal or the middle joint grounding lead.

[0013] Furthermore, the conditioning of the high-frequency partial discharge signal is specifically performed by a high-frequency partial discharge signal conditioning circuit, and the high-frequency partial discharge signal conditioning circuit includes a signal amplifier, a signal filter and an A / D converter connected in sequence.

[0014] Furthermore, the calculation process of the signal energy criterion includes the following steps:

[0015] Calculate the energy accumulation curve of the given signal x;

[0016] Calculate the negative trend of the signal based on the total energy of the signal from the energy accumulation curve;

[0017] The signal energy criterion curve is calculated based on the sum of the energy accumulation curve and the signal negative trend.

[0018] Furthermore, the calculation expression of the energy accumulation curve is:

[0019]

[0020] In the formula, S i is the energy accumulation curve of signal x, i is the sampling index value, x k is the kth segment of signal x, and N is the signal sampling length;

[0021] The calculation expression of the negative trend of the signal is:

[0022]

[0023] Where σ is the negative trend of the signal, S N is the total signal energy, α is the trend coefficient;

[0024] The calculation expression of the signal energy criterion is:

[0025]

[0026] In the formula, EC k is the signal energy criterion curve.

[0027] Furthermore, the arrival time of the partial discharge signal is the time corresponding to the lowest point of the amplitude in the signal energy criterion curve.

[0028] Furthermore, the calculation expression for locating the cable defect position in the single-end connection mode is:

[0029]

[0030] Where x is the cable defect position, L is the cable length, v is the propagation speed of the high-frequency partial discharge signal in the cable, v is the signal arrival time difference, and is the arrival time difference between the high-frequency partial discharge signal and its reflected signal.

[0031] Furthermore, the calculation expression for locating the cable defect position in the double-end connection mode is:

[0032]

[0033] Where x is the cable defect position, L is the cable length, v is the propagation speed of the high-frequency partial discharge signal in the cable, v is the signal arrival time difference, and is the arrival time difference of the high-frequency partial discharge signals generated by the fault current received by the high-frequency current sensors at both ends.

[0034] The present invention also provides a cable locating system based on the cable locating method based on the partial discharge signal arrival time identification as described above, comprising:

[0035] The high-frequency current sensor with timing function senses the high-frequency partial discharge signal of the partial discharge of the cable grounding lead in a single-ended or double-ended connection mode;

[0036] High-frequency partial discharge signal conditioning and acquisition circuit, used for conditioning and acquiring high-frequency partial discharge signals;

[0037] The host computer is used to identify the arrival time of the partial discharge signal from the collected high-frequency partial discharge signal based on the signal energy criterion;

[0038] The cable defect position is located according to the cable length and the signal arrival time difference. The signal arrival time difference is the arrival time difference between the high-frequency partial discharge signal and its reflected signal in a single-end connection mode, and is the arrival time difference of the high-frequency partial discharge signal generated by the fault current received by the high-frequency current sensors at both ends in a double-end connection mode.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] (1) Compared with the traditional bridge method and pulse method, the present invention adopts a high-frequency current method to obtain the local discharge signal inside the cable from the grounded lead at one or both ends of the cable, identifies the arrival time of the local discharge signal based on the local discharge signal, and finally locates the cable defect position based on the cable length and the signal arrival time difference. This method does not require the cable to be powered off and can locate the fault point without affecting the normal operation of the cable.

[0041] (2) The present invention automatically identifies the arrival time of the local discharge signal based on the signal energy criterion. The sum of the signal energy accumulation curve and the negative trend is defined as the signal energy criterion curve. The time corresponding to the lowest point of the amplitude on the signal energy criterion curve is the arrival time of the local discharge signal. It can further automatically realize the signal time difference and fault location, reduce the error of manual intervention, and greatly improve the accuracy and efficiency of locating the fault point of the power cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic flow chart of a cable positioning method based on partial discharge signal arrival time recognition provided in an embodiment of the present invention;

[0043] Figure 2 A structural diagram of a high-frequency partial discharge signal conditioning and acquisition device provided in an embodiment of the present invention;

[0044] Figure 3 A schematic diagram of a curve for automatically identifying the arrival time of a partial discharge signal based on a signal energy criterion provided in an embodiment of the present invention;

[0045] Figure 4 A schematic diagram of a single-ended test mode provided in an embodiment of the present invention;

[0046] Figure 5 A schematic diagram of a process for automatically determining a signal arrival time difference in a single-ended test mode provided in an embodiment of the present invention;

[0047] Figure 6 A schematic diagram of a double-ended test mode provided in an embodiment of the present invention;

[0048] Figure 7 A schematic diagram of a process for automatically determining a signal arrival time difference in a dual-end test mode provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0050] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0051] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0052] Example 1

[0053] like Figure 1 As shown, this embodiment provides a cable positioning method based on partial discharge signal arrival time recognition, which can be used for status monitoring of running cables, including the following steps:

[0054] S1: Use a high-frequency current sensor with a timing function to sense the high-frequency partial discharge signal of the partial discharge of the cable grounding lead in a single-end or double-end connection mode;

[0055] S2: Condition and collect high-frequency partial discharge signals;

[0056] S3: Based on the signal energy criterion, the arrival time of the partial discharge signal is identified from the collected high-frequency partial discharge signal;

[0057] S4: Locate the cable defect position based on the cable length and the signal arrival time difference. The signal arrival time difference is the arrival time difference between the high-frequency partial discharge signal and its reflected signal in the single-end connection mode, and is the arrival time difference of the high-frequency partial discharge signal generated by the fault current received by the high-frequency current sensors at both ends in the double-end connection mode.

[0058] Specifically, in step S1, the high-frequency current sensor has a built-in iron core, a coil, a Beidou timing module and a power module. The coil is wrapped around the outside of the iron core. The high-frequency current sensor is installed through the core at the cable terminal or the middle joint grounding lead. It can be installed in a single-end or double-end manner. The frequency range of the high-frequency current sensor is 16kHz to 50MHz. In this embodiment, the transmission impedance of the high-frequency current sensor is 16mV / mA, the sensitivity is 10pC, and the timing accuracy is 10ns.

[0059] In step S2, Figure 2As shown, the high-frequency partial discharge signal is conditioned specifically by a high-frequency partial discharge signal conditioning circuit, and the high-frequency partial discharge signal conditioning circuit includes a signal amplifier, a signal filter and an A / D converter connected in sequence. The high-frequency partial discharge signal is collected specifically by a data acquisition and FPGA preprocessing unit, which has a signal edge processing function and uploads the collected high-frequency partial discharge signal to a host computer through a communication cable. In this embodiment, the signal sampling rate of the data acquisition and FPGA preprocessing unit is 1GS / s, the sampling bandwidth is 200MHz, and the signal sampling accuracy is 16bit, which can realize the synchronous processing and collection of multi-channel high-frequency partial discharge signals.

[0060] Step S3 realizes automatic identification of the arrival time of the partial discharge signal based on the signal energy criterion, wherein the signal energy criterion calculation process is as follows:

[0061] (a) For a given signal x, calculate its energy accumulation curve:

[0062]

[0063] In the formula, S i is the energy accumulation curve of signal x, i is the sampling index value, x k is the kth segment of signal x, and N is the signal sampling length;

[0064] (b) Calculate the negative trend of the signal based on the total energy of the energy accumulation curve:

[0065]

[0066] Where σ is the negative trend of the signal, S N is the total signal energy, α is the trend coefficient;

[0067] (c) Calculate the signal energy criterion curve based on the sum of the energy accumulation curve and the signal negative trend:

[0068]

[0069] In the formula, EC k is the signal energy criterion curve.

[0070] According to the above definition, the arrival time of the local discharge signal automatically identified based on the signal energy criterion is recorded as the time corresponding to the lowest amplitude point on the signal energy criterion curve, such as Figure 3 shown.

[0071] In step S4, the cable defect position is located according to the cable length and the signal arrival time difference, which is specifically divided into two calculation methods: single-ended test mode and double-ended test mode:

[0072] (a) When using the single-ended test mode, the high-frequency current sensor at the test end receives the local discharge high-frequency current signal generated by the fault point and the reflected signal generated by the signal at the end of the cable, such as Figure 4 and Figure 5 As shown, the calculation method of defect point x is:

[0073]

[0074] Where x is the cable defect position, L is the cable length, v is the propagation speed of the high-frequency partial discharge signal in the cable, and v is the signal arrival time difference, which is the arrival time difference between the high-frequency partial discharge signal and its reflected signal. The time difference can be automatically determined according to the signal energy criterion.

[0075] (b) When the double-end test mode is adopted, the high-frequency current sensors installed at the beginning and end of the cable respectively receive the local discharge high-frequency current signals generated by the fault circuit, such as Figure 6 and Figure 7 As shown, the calculation method of defect point x is:

[0076]

[0077] Where x is the cable defect position, L is the cable length, v is the propagation speed of the high-frequency partial discharge signal in the cable, and v is the signal arrival time difference, which is the arrival time difference of the high-frequency partial discharge signal generated by the fault current received by the high-frequency current sensors at both ends. The time difference can be automatically determined according to the signal energy criterion.

[0078] Example 2

[0079] This embodiment provides a cable locating system based on a cable locating method based on partial discharge signal arrival time recognition as in Embodiment 1, comprising:

[0080] The high-frequency current sensor with timing function senses the high-frequency partial discharge signal of the partial discharge of the cable grounding lead in a single-ended or double-ended connection mode;

[0081] High-frequency partial discharge signal conditioning and acquisition circuit, used for conditioning and acquiring high-frequency partial discharge signals;

[0082] The host computer is used to identify the arrival time of the partial discharge signal from the collected high-frequency partial discharge signal based on the signal energy criterion;

[0083] The cable defect position is located according to the cable length and the signal arrival time difference. The signal arrival time difference is the arrival time difference between the high-frequency partial discharge signal and its reflected signal in the single-ended connection mode, and is the arrival time difference of the high-frequency partial discharge signal generated by the fault current received by the high-frequency current sensors at both ends in the double-ended connection mode.

[0084] It should be noted that the specific content and beneficial effects of the system of the present application can be found in the above-mentioned method embodiment, which will not be repeated here.

[0085] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A cable positioning method based on partial discharge signal arrival time recognition, characterized in that: The following steps are involved: A high-frequency current sensor with a timing function is used to sense the high-frequency partial discharge signal of the partial discharge of the cable grounding lead in a single-end or double-end connection mode; Condition and collect high-frequency partial discharge signals; Based on the signal energy criterion, the arrival time of the partial discharge signal is identified from the collected high-frequency partial discharge signal; The cable defect position is located according to the cable length and the signal arrival time difference. The signal arrival time difference is the arrival time difference between the high-frequency partial discharge signal and its reflected signal in a single-end connection mode, and is the arrival time difference of the high-frequency partial discharge signal generated by the fault current received by the high-frequency current sensors at both ends in a double-end connection mode.

2. A cable positioning method based on partial discharge signal arrival time recognition according to claim 1, characterized in that: The frequency range of the high-frequency current sensor is 16kHz to 50MHz.

3. A cable positioning method based on partial discharge signal arrival time recognition according to claim 1, characterized in that: The high-frequency current sensor has a built-in iron core, a coil, a Beidou timing module and a power module. The coil is wrapped around the outside of the iron core. The high-frequency current sensor is installed through the core at the cable terminal or the middle joint grounding lower lead.

4. A cable positioning method based on partial discharge signal arrival time recognition according to claim 1, characterized in that: The conditioning of the high-frequency partial discharge signal is specifically performed by a high-frequency partial discharge signal conditioning circuit, and the high-frequency partial discharge signal conditioning circuit includes a signal amplifier, a signal filter and an A / D converter connected in sequence.

5. The cable positioning method based on partial discharge signal arrival time recognition according to claim 1 is characterized in that: The calculation process of the signal energy criterion includes the following steps: Calculate the energy accumulation curve of the given signal x; Calculate the negative trend of the signal based on the total energy of the signal from the energy accumulation curve; The signal energy criterion curve is calculated based on the sum of the energy accumulation curve and the signal negative trend.

6. A cable positioning method based on partial discharge signal arrival time recognition according to claim 5, characterized in that: The calculation expression of the energy accumulation curve is: In the formula, S i is the energy accumulation curve of signal x, i is the sampling index value, x k is the kth segment of signal x, and N is the signal sampling length; The calculation expression of the negative trend of the signal is: Where σ is the negative trend of the signal, S N is the total signal energy, α is the trend coefficient; The calculation expression of the signal energy criterion is: In the formula, EC k is the signal energy criterion curve.

7. A cable positioning method based on partial discharge signal arrival time recognition according to claim 5, characterized in that: The arrival time of the partial discharge signal is the time corresponding to the lowest point of the amplitude in the signal energy criterion curve.

8. A cable positioning method based on partial discharge signal arrival time recognition according to claim 1, characterized in that: The calculation expression for locating the cable defect position in the single-end connection mode is: Where x is the cable defect position, L is the cable length, v is the propagation speed of the high-frequency partial discharge signal in the cable, v is the signal arrival time difference, and is the arrival time difference between the high-frequency partial discharge signal and its reflected signal.

9. A cable positioning method based on partial discharge signal arrival time recognition according to claim 1, characterized in that: The calculation expression for locating the cable defect position in the double-end connection mode is: Where x is the cable defect position, L is the cable length, v is the propagation speed of the high-frequency partial discharge signal in the cable, v is the signal arrival time difference, and is the arrival time difference of the high-frequency partial discharge signals generated by the fault current received by the high-frequency current sensors at both ends.

10. A cable locating system based on a cable locating method based on partial discharge signal arrival time recognition as claimed in any one of claims 1 to 9, characterized in that: include: The high-frequency current sensor with timing function senses the high-frequency partial discharge signal of the partial discharge of the cable grounding lead in a single-ended or double-ended connection mode; High-frequency partial discharge signal conditioning and acquisition circuit, used for conditioning and acquiring high-frequency partial discharge signals; The host computer is used to identify the arrival time of the partial discharge signal from the collected high-frequency partial discharge signal based on the signal energy criterion; The cable defect position is located according to the cable length and the signal arrival time difference. The signal arrival time difference is the arrival time difference between the high-frequency partial discharge signal and its reflected signal in a single-end connection mode, and is the arrival time difference of the high-frequency partial discharge signal generated by the fault current received by the high-frequency current sensors at both ends in a double-end connection mode.

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