A cable fault detection device

Abstract

The disclosed embodiment relates to a cable fault detection device, comprising: a first coil, one end of which is electrically connected to a signal acquisition unit, and the other end of which is wound around the outer layer of a cable body; a second coil, one end of which is electrically connected to the other end of the first coil, and the other end of which is wound around the outer layer of a grounding cable, and electrically connected to the signal acquisition unit via the outer layer, wherein the grounding cable is the grounding portion of the sheath of the cable body when the cable body is separated at the end. The use of this device can cause the sheath current in the cable body monitored by the coil and the current generated by the grounding cable to cancel each other out, thereby obtaining the transmission current of the cable core, thereby being able to safely and accurately determine whether the cable has a fault directly based on the magnitude of the transmission current.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the field of cable technology, and in particular to a device for detecting cable faults. Background Art

[0002] With the increase in the utilization rate and total amount of high-voltage cables, the operation and maintenance of cables has also increased accordingly. There is an urgent need for effective detection means to warn and locate hidden dangers and faults of cables. In the related technology, the cable body is passed through the coil sensor, and then the sheath grounding wire of the cable is passed through the coil sensor in the opposite direction, so that the sheath current on the body and the sheath current on the grounding wire enter and exit the coil sensor, and the two cancel each other out. Since the coil sensor passes through the body and the sheath at the same time, the inner diameter of the coil sensor is relatively large. For example, in order to adapt to most cable outer diameters of 220kV cables, the inner diameter of the sensor is generally required to be about 240mm. Therefore, the size of the sensor is relatively large and the production cost is high.

[0003] In other related technologies, when the cable core and sheath grounding wire of the cable are separated at the cable terminal, the coil sensor is installed on the cable core. The installation space of the cable core is limited, and it is too close to the insulation terminal of the cable terminal, which often causes danger. The coil sensor is installed on the grounding wire. Due to the insulation joint of the high-voltage cable and the discontinuous sheath of the cable (there will be direct grounding, protective grounding, and cross-interconnected grounding), the signal attenuation in the grounding sheath is large, and the fault traveling wave signal cannot be effectively detected. Summary of the Invention

[0004] Based on this, it is necessary to provide a cable fault detection device that can safely and accurately measure cable faults at a low cost in order to address the above technical problems.

[0005] In a first aspect, an embodiment of the present disclosure provides a device for detecting a cable fault, comprising:

[0006] a first coil, one end of the first coil being electrically connected to the signal acquisition unit, and the other end of the first coil being wound around the outer layer of the cable body;

[0007] A second coil, one end of the second coil is electrically connected to the other end of the first coil, the other end of the second coil is wound around the outer layer of the grounding cable, and is electrically connected to the signal acquisition unit through the outer layer. The grounding cable is the grounding portion of the sheath of the cable body when it is separated at the end.

[0008] In one embodiment, the cable fault detection device also includes a first annular support member, which is sleeved on the outer layer of the cable body. The other end of the first coil travels around the first annular support member in the circumferential direction of the first annular support member from a preset initial position, and then spirally wraps around the first annular support member in the opposite direction of the circumferential direction to return to the preset initial position.

[0009] In one embodiment, the cable fault detection device also includes a second annular support member, which is sleeved on the outer layer of the grounding cable. The other end of the second coil travels around the second annular support member in the circumferential direction of the second annular support member from a preset initial position of the second annular support member, and then spirally wraps around the second annular support member in the opposite direction of the circumferential direction to return to the preset initial position.

[0010] In one embodiment, the other end of the first coil is electrically connected to one end of the second coil via a first conductor of a second cable, and the other end of the second coil is electrically connected to a second conductor of the second cable.

[0011] In one embodiment, the other end of the second coil is electrically connected to the signal acquisition unit through the second conductor of the second cable and the first conductor of the first cable, and one end of the first coil is electrically connected to the signal acquisition unit through the first conductor of the first cable.

[0012] In one embodiment, the length of the first cable is greater than a first preset value, and the length of the second cable is greater than a second preset value.

[0013] In one embodiment, the first cable and the second cable are high-frequency coaxial cables.

[0014] In one embodiment, the mutual inductance of the first coil is the same as the mutual inductance of the second coil.

[0015] In one embodiment, the number of turns of the first coil and the second coil, the cross-sectional area of ​​the winding coil, and the inner radius of the winding coil satisfy the following formula:

[0016] N1×S1 / R1=N2×S2 / R2. N1 is the number of turns of the first coil, N2 is the number of turns of the second coil, S1 is the cross-sectional area of ​​the winding surface of the first coil, S2 is the cross-sectional area of ​​the winding surface of the second coil, R1 is the inner radius of the first coil after winding, and R2 is the inner radius of the second coil after winding.

[0017] In one embodiment, the signal acquisition unit is configured to convert the acquired signal into a transmission current of the cable, and send fault information when the transmission current is greater than a preset threshold.

[0018] In a second aspect, an embodiment of the present disclosure further provides a cable fault detection system, comprising:

[0019] Cable body;

[0020] The cable fault detection device as described in any one of the devices in the above disclosed embodiments.

[0021] The above-mentioned cable fault detection device is provided with a first coil on the cable body and a second coil on the grounding cable, and the first coil and the second coil are connected, so that the sheath current in the cable body and the current generated in the grounding cable monitored by the coil can offset each other, and the transmission current of the cable core is obtained, so that it can be safely and accurately judged whether the cable has a fault directly based on the size of the transmission current. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of a cable fault detection device in one embodiment;

[0023] Figure 2 Schematic diagram of the structure of a cable fault detection device in one embodiment. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure more clear, the embodiments of the present disclosure are further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present disclosure and are not intended to limit the embodiments of the present disclosure.

[0025] In one embodiment, Figure 1 As shown, a cable fault detection device is provided, comprising:

[0026] a first coil, one end of the first coil being electrically connected to the signal acquisition unit, and the other end of the first coil being wound around the outer layer of the cable body;

[0027] The cable body 101 comprises a cable core 103 and a sheath 102. The sheath 102 is a sealed metal sheath covering the cable to prevent moisture from seeping in. During power transmission, the generation of induced voltage in the sheath of high-voltage cables is a common phenomenon in power cables. This induced voltage generates sheath current in the sheath.

[0028] In the disclosed embodiment, the cable fault detection device includes a first coil 104, which is disposed on the cable body and is used to detect the current flowing through the cable body. One end of the coil is connected to a signal acquisition unit 109 for transmitting the collected signal to the signal acquisition unit 109. The other end of the coil is wound around the outer layer of the cable body to detect the current in the cable body.

[0029] A second coil, one end of the second coil is electrically connected to the other end of the first coil, the other end of the second coil is wound around the outer layer of the grounding cable, and is electrically connected to the signal acquisition unit through the outer layer. The grounding cable is the grounding portion of the sheath of the cable body when it is separated at the end.

[0030] In the embodiment of the present disclosure, the cable fault detection device also includes a second coil 106, which is a coil arranged on the grounding cable 105, wherein the grounding cable 105 is the portion of the sheath of the cable body 101 that is separated and grounded when the cable body 101 is separated. In one example, the cable will separate the cable core and the grounding cable at a preset position, wherein the grounding cable is the portion of the sheath of the cable body that is separated and grounded. One end of the second coil is electrically connected to the other end of the first coil, thereby realizing the series connection of the first coil and the second coil; the second coil is arranged on the outer layer of the grounding cable in a winding manner, and is used to detect the current in the grounding cable by winding the grounding cable into a coil. After the winding is completed, the other end of the second coil will be electrically connected to the signal acquisition unit, and is used to transmit the collected signal to the signal acquisition unit together with one end of the first coil.

[0031] The winding directions of the first and second coils are usually restricted so that when current flows through the cable, the electromotive forces generated on the first and second coils are in opposite directions.

[0032] In one example, because the cable body has a larger diameter and the grounding cable has a smaller diameter, the first coil has a larger diameter and the second coil has a smaller diameter. In one example, the inner diameter of the first coil can be 120 mm, and the inner diameter of the second coil can be 40 mm. The two coils are connected in series via a high-frequency coaxial cable; the series-connected coils are connected to the input of a cable fault acquisition device via the high-frequency coaxial cable.

[0033] In the embodiment of the present disclosure, a first coil is provided on the cable body, a second coil is provided on the grounding cable, and the first coil and the second coil are connected, so that the sheath current in the cable body and the current generated by the grounding cable monitored by the coil can cancel each other out, and the transmission current of the cable core can be obtained, so that it can be judged whether the cable has a fault based on the magnitude of the transmission current in a low-cost, safe and accurate manner. At the same time, since the embodiment of the present disclosure sets the coil on the cable body and the grounding cable, it avoids the situation where the coil is installed on the cable core too close to the insulation terminal, which may cause danger. The embodiment of the present disclosure has low requirements for the installation position of the coil, and is more practical, especially for installation at the middle joint, and the access circuit is simple, without the need for redundant connector interfaces.

[0034] In one embodiment, the cable fault detection device also includes a first annular support member, which is sleeved on the outer layer of the cable body. The other end of the first coil travels around the first annular support member in the circumferential direction of the first annular support member from the preset initial position of the first annular support member, and then spirally wraps around the first annular support member in the opposite direction of the circumferential direction to return to the preset initial position.

[0035] In the embodiment of the present disclosure, when the coil is wound, an annular support is further provided. The first annular support 201 is sleeved on the outer layer of the cable body. When the first coil is wound on the outer layer of the cable body, it can be wound on the first annular support. In one example, the first annular support is a hollow ring. The winding method is that the other end of the first coil starts from any preset initial position of the annular support and circles around the first annular support in the circumferential direction of the first annular support, and then spirally wraps around the first annular support in the opposite direction of the circumferential direction to return to the preset initial position of the annular support.

[0036] In one embodiment, the cable fault detection device also includes a second annular support member, which is sleeved on the outer layer of the grounding cable. The other end of the second coil travels around the second annular support member in the circumferential direction of the second annular support member from a preset initial position of the second annular support member, and then spirally wraps around the second annular support member in the opposite direction of the circumferential direction to return to the preset initial position.

[0037] In the disclosed embodiment, an annular support member is further provided during coil winding. The second annular support member 202 is sleeved on the outer layer of the grounding cable. When the second coil is wound around the outer layer of the cable body, it can be wound around the second annular support member. In one example, the second annular support member is a hollow ring. The winding method is such that the other end of the second coil starts from any preset initial position of the annular support member, travels around the circumference of the second annular support member once, and then spirally wraps around the second annular support member in the opposite direction of the circumference to return to the preset initial position of the annular support member.

[0038] The disclosed embodiment provides an annular support for coil winding, which can facilitate coil winding, standardize the parameters of the coil after winding, and accurately limit the coil parameters to obtain a desired detection signal.

[0039] In one embodiment, the other end of the first coil is electrically connected to one end of the second coil via a first conductor of a second cable, and the other end of the second coil is electrically connected to a second conductor of the second cable.

[0040] In the disclosed embodiment, the other end of the first coil is electrically connected to one end of the second coil via the first conductor of the second cable 107. The other end of the first coil is connected to one end of the first conductor of the second cable 107, and one end of the second coil is connected to the other end of the first conductor of the second cable. The other end of the second coil is connected to one end of the second conductor of the second cable after being wound around a ground cable.

[0041] In one embodiment, the other end of the second coil is electrically connected to the signal acquisition unit through the second conductor of the second cable and the first conductor of the first cable, and one end of the first coil is electrically connected to the signal acquisition unit through the first conductor of the first cable.

[0042] In the embodiment of the present disclosure, the other end of the second coil is first connected to the second conductor of the second cable 107, and then connected to the signal acquisition unit through the first conductor of the first cable 108, and one end of the first coil is connected to the signal acquisition unit through the first conductor of the first cable 108.

[0043] In the embodiment of the present disclosure, the first cable and the second cable are provided to realize the mutual connection among the first coil, the second coil and the signal acquisition unit.

[0044] In one embodiment, the length of the first cable is greater than a first preset value, and the length of the second cable is greater than a second preset value.

[0045] In the embodiment of the present disclosure, the length of the first cable 108 can be greater than a preset value, and the length of the second cable 107 can also be greater than a preset value. In one example, the preset value can be any length value within a controllable range.

[0046] In the embodiment of the present disclosure, the lengths of the first cable and the second cable can both be greater than a preset value, thereby reducing the restrictions on the installation position of the detection device and making the detection device more convenient and efficient to use.

[0047] In one embodiment, the first cable and the second cable are high frequency coaxial cables.

[0048] In the embodiment of the present disclosure, the first cable and the second cable are high-frequency coaxial cables.

[0049] In the embodiment of the present disclosure, by using a high-frequency coaxial cable to electrically connect the first coil, the second coil and the signal acquisition unit, the high-frequency signal can be prevented from significantly attenuating during transmission, so that the signal collected by the signal acquisition unit is more accurate, thereby improving the accuracy of fault detection.

[0050] In one embodiment, the mutual inductance of the first coil is the same as the mutual inductance of the second coil.

[0051] In the embodiment of the present disclosure, when the first coil and the second coil are provided, it is necessary to control the mutual inductance coefficients of the first coil and the second coil to be the same.

[0052] In this disclosed embodiment, by ensuring the mutual inductance of the first and second coils is the same, the electromotive force generated by the sheath current flowing through the first coil and the second coil are equal in magnitude and opposite in magnitude, thereby canceling each other out. This ensures that only the current flowing through the cable core, i.e., the transmission current, is retained, eliminating the influence of the sheath current and accurately capturing the fault signal.

[0053] In one example, in order to enable the two coils to be connected in series to cancel each other out, the turns and sizes of the first coil and the second coil should satisfy the following relationship:

[0054] U1=M1×2×f×π×I m

[0055] U2=M2×2×f×π×I m

[0056] Where U1 is the sheath voltage output by the first coil, U2 is the voltage output by the second coil, M1 is the mutual inductance coefficient of the first coil, M2 is the mutual inductance coefficient of the second coil, f is the frequency of the measured sheath signal, I mTherefore, if U1=U2, M1=M2 is required, that is, the mutual inductance of the first coil is equal to the mutual inductance of the second coil.

[0057] In one embodiment, the number of turns of the first coil and the second coil, the cross-sectional area of ​​the winding coil, and the inner radius of the winding coil satisfy the following formula:

[0058] N1×S1 / R1=N2×S2 / R2. N1 is the number of turns of the first coil, N2 is the number of turns of the second coil, S1 is the cross-sectional area of ​​the winding surface of the first coil, S2 is the cross-sectional area of ​​the winding surface of the second coil, R1 is the inner radius of the first coil after winding, and R2 is the inner radius of the second coil after winding.

[0059] In one example, let M1=M2, that is, μ0×N1×S1 / (2×π×R1)=μ0×N2×S2 / (2×π×R2)

[0060] Where μ0 is the magnetic permeability of vacuum; N1 is the number of turns of coil 1, S1 is the cross-sectional area of ​​the coil, and R1 is the diameter of coil 1; N2 is the number of turns of coil 2, S2 is the cross-sectional area of ​​the coil, and R2 is the diameter of coil 2.

[0061] After simplification, we get: N1×S1 / R1=N2×S2 / R2.

[0062] In the embodiment of the present disclosure, when setting the first coil and the second coil, the parameters of the first coil and the second coil will be set. According to the setting that the mutual inductance coefficient of the first coil and the mutual inductance coefficient of the second coil are the same, the number of turns, cross-sectional area and inner radius of the coil will be limited as follows: N1×S1 / R1=N2×S2 / R2. Among them, N1 is the number of turns of the first coil, N2 is the number of turns of the second coil, S1 is the cross-sectional area of ​​the winding surface of the first coil, S2 is the cross-sectional area of ​​the winding surface of the second coil, R1 is the inner radius after the first coil is wound, and R2 is the inner radius after the second coil is wound.

[0063] In this disclosed embodiment, by limiting the parameters of the first and second coils to equalize their mutual inductance, the electromotive force generated by the sheath current flowing through the first coil and the second coil are controlled to have equal magnitudes and opposite magnitudes, thereby canceling each other out. This retains only the current in the cable core, or the transmission current, eliminating the influence of the sheath current and accurately capturing fault signals.

[0064] In one embodiment, the signal acquisition unit is configured to convert the acquired signal into a transmission current of the cable, and send fault information when the transmission current is greater than a preset threshold.

[0065] In the disclosed embodiment, the signal acquisition unit converts the collected signal into the cable's transmission current, thereby determining whether the cable has experienced a fault based on the magnitude of the transmission current. When the transmission current exceeds a preset threshold, a fault traveling wave signal is generated, indicating a cable fault, at which point the signal acquisition unit transmits the fault information. It should be understood that the preset threshold is a user-defined threshold based on the magnitude of the transmission current when the cable is safe and when it is faulty.

[0066] In the embodiment of the present disclosure, the signal acquisition unit collects and converts the signal, determines whether a fault occurs, and sends fault information. The embodiment of the present disclosure can collect fault signals and send fault information, so that relevant personnel can obtain information about cable faults in a timely manner.

[0067] The present disclosure also provides a cable fault detection system, including:

[0068] Cable body;

[0069] The cable fault detection device as described in any one of the devices in the above disclosed embodiments.

[0070] In the disclosed embodiment, the fault detection system includes a cable body, and the components of the cable body include but are not limited to the cable core and sheath. The basic structure of the cable consists of four parts: the core, the insulation layer, the shielding layer and the protective layer. The core is the conductive part of the power cable, which is used to transmit electrical energy and is the main part of the cable; the insulation layer is used to electrically isolate the core from the ground and the cores of different phases from each other to ensure the transmission of electrical energy, and is an indispensable component of the power cable structure; the shielding layer, power cables of 15kV and above generally have a conductor shielding layer and an insulation shielding layer; the protective layer, the function of the protective layer is to protect the power cable from the intrusion of external impurities and moisture, and to prevent external forces from directly damaging the power cable. Cables can be divided into medium and low voltage power cables, high voltage cables, extra high voltage cables and ultra high voltage cables according to voltage levels. In addition, they can be divided into AC cables and DC cables according to current systems. At a preset position, the sheath of the cable body will be separated and grounded to become a grounding cable. It also includes the cable fault detection device described in any of the devices in the above-mentioned disclosed embodiments. The implementation solution to the problem provided by this device is the same as the implementation solution recorded in the above-mentioned method. Therefore, the specific limitations can be found in the limitations on the cable fault detection device above, which will not be repeated here.

[0071] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0072] The above-described embodiments merely represent several implementation methods of the embodiments of the present disclosure. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patents of the embodiments of the present disclosure. It should be noted that a person skilled in the art can make several modifications and improvements without departing from the concept of the embodiments of the present disclosure, and these modifications and improvements fall within the scope of protection of the embodiments of the present disclosure. Therefore, the scope of protection of the embodiments of the present disclosure shall be subject to the appended claims.

Claims

1. A cable fault detection device, characterized in that: include: a first coil, one end of the first coil being electrically connected to the signal acquisition unit, and the other end of the first coil being wound around the outer layer of the cable body; a second coil, one end of the second coil being electrically connected to the other end of the first coil, the other end of the second coil being wound around an outer layer of a grounding cable and electrically connected to the signal acquisition unit through the outer layer, the grounding cable being the grounding portion of the sheath of the cable body when the cable body is separated at the end; The winding manner of the first coil and the second coil is restricted in that the winding manner of the two coils is set so that when current passes through the cable, the electromotive forces generated on the first coil and the second coil are in opposite directions.

2. The cable fault detection device according to claim 1, characterized in that: It also includes a first annular support member, which is sleeved on the outer layer of the cable body. The other end of the first coil travels around the first annular support member in the circumferential direction of the first annular support member from the preset initial position of the first annular support member, and then spirally wraps around the first annular support member in the opposite direction of the circumferential direction to return to the preset initial position.

3. The cable fault detection device according to claim 1, characterized in that: It also includes a second annular support member, which is sleeved on the outer layer of the grounding cable. The other end of the second coil travels around the second annular support member in the circumferential direction from a preset initial position of the second annular support member, and then spirally wraps around the second annular support member in the opposite direction of the circumferential direction to return to the preset initial position.

4. The cable fault detection device according to claim 1, characterized in that: The other end of the first coil is electrically connected to one end of the second coil through the first conductor of the second cable, and the other end of the second coil is electrically connected to the second conductor of the second cable.

5. The cable fault detection device according to claim 4, characterized in that: The other end of the second coil is electrically connected to the signal acquisition unit through the second conductor of the second cable and the first conductor of the first cable. One end of the first coil is electrically connected to the signal acquisition unit through the first conductor of the first cable.

6. The cable fault detection device according to claim 4 or 5, characterized in that: The length of the first cable is greater than a first preset value, and the length of the second cable is greater than a second preset value.

7. The cable fault detection device according to claim 4, 5 or 6, characterized in that: The first cable and the second cable are high-frequency coaxial cables.

8. The cable fault detection device according to claim 1, characterized in that: The mutual inductance of the first coil is the same as the mutual inductance of the second coil.

9. The cable fault detection device according to claim 8, characterized in that: The number of turns of the first coil and the second coil, the cross-sectional area of ​​the winding coils, and the inner radius of the winding coils satisfy the following formula: N1×S1 / R1=N2×S2 / R2 Among them, N1 is the number of turns of the first coil, N2 is the number of turns of the second coil, S1 is the cross-sectional area of ​​the winding surface of the first coil, S2 is the cross-sectional area of ​​the winding surface of the second coil, R1 is the inner radius of the first coil after winding is completed, and R2 is the inner radius of the second coil after winding is completed.

10. The cable fault detection device according to claim 1, characterized in that: The signal acquisition unit is used to convert the acquired signal into a transmission current of the cable, and send fault information when the transmission current is greater than a preset threshold.

11. A cable fault detection system, characterized in that: include: Cable body; A cable fault detection device according to any one of claims 1 to 10.

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