A distributed detection system and method for partial discharge inside a cable

Abstract

The invention discloses a distributed detection system and method for partial discharge inside a cable. The detection system comprises a plurality of distributed pulse current detection units arranged between an outer semi-conductive layer and a metal armor layer inside the cable. The distributed pulse current detection units comprise a flexible electrode, a controllable switch, a pulse current detection impedance, a signal amplification module, a collection and control module, a communication module and a temperature difference energy acquisition module. One end of the flexible electrode is coupled with the cable insulation layer and the other end is electrically connected to the controllable switch. One end of the collection and control module is connected to the controllable switch and the other end is connected to the communication module. One end of the pulse current detection impedance is electrically connected to the controllable switch and the other end is electrically connected to the signal amplification module. The signal amplification module is connected to the collection and control module. The signal amplification module, the collection and control module and the communication module are all electrically connected to the temperature difference energy acquisition module. One end of the temperature difference energy acquisition module is connected to the outer semi-conductive layer and the other end is connected to the metal armor layer.

Description

Technical Field

[0001] The invention relates to the field of cable discharge detection, in particular to a distributed detection system and method for partial discharge inside a cable. Background Art

[0002] The traditional cable partial discharge distributed test system installs high-frequency partial discharge acquisition sensors and signal acquisition hosts at the joints and terminals of the high-voltage cable line to realize the simultaneous detection of partial discharge signals of multiple groups of cable accessories in the high-voltage cable line. The signals collected by each signal acquisition host are transmitted to the data analysis system in real time via optical fiber or wireless communication. Each sensor and signal acquisition host is powered by a 220kV power supply.

[0003] The above method has the following problems: 1) The sensor is installed externally, and the internal defect signal of the cable is greatly attenuated when transmitted to the outside, resulting in poor detection sensitivity; 2) The sensor and signal acquisition host are powered by a 220kV power supply, which cannot be applied in areas where there is no power supply such as pipe laying and direct burial on site; 3) If the collected signal is transmitted via optical fiber, an additional optical fiber channel needs to be added. If it is transmitted via wireless communication, a relay station needs to be added at the bend of the cable tunnel. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a distributed detection system and method for partial discharge inside a cable, wherein a distributed pulse current detection unit is placed inside the cable, and the need for external power supply is eliminated by extracting energy through temperature. Moreover, by coupling the signal into the conductor for transmission, the partial discharge conditions at different locations can be analyzed through different bandpass filters, thereby realizing distributed detection of partial discharge at different locations.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a distributed detection system for partial discharge inside a cable, comprising a plurality of distributed pulse current detection units arranged between an outer semi-conductive layer and a metal armor layer inside the cable, wherein the distributed pulse current detection unit comprises a flexible electrode, a controllable switch, a pulse current detection impedance, a signal amplification module, a collection and control module, a communication module and a temperature difference energy acquisition module, wherein one end of the flexible electrode is coupled to the cable insulation layer and the other end is electrically connected to the controllable switch, one end of the collection and control module is connected to the controllable switch and the other end is connected to the communication module, one end of the pulse current detection impedance is electrically connected to the controllable switch and the other end is electrically connected to the signal amplification module, the signal amplification module is electrically connected to the collection and control module, the signal amplification module, the collection and control module and the communication module are all electrically connected to the temperature difference energy acquisition module, one end of the temperature difference energy acquisition module is electrically connected to the outer semi-conductive layer and the other end is electrically connected to the metal armor layer.

[0006] A further improvement of the technical solution of the present invention is that the distance between two adjacent distributed pulse current detection units is 50-100m.

[0007] A further improvement of the technical solution of the present invention is that: the flexible electrode is a circular metal structure and the lower lead of the flexible electrode is located at a position 0.618 times the radius of the flexible electrode.

[0008] A further improvement of the technical solution of the present invention is: a distributed detection method for partial discharge inside a cable, comprising the following steps:

[0009] Step S1, using the cable insulation layer as a coupling capacitor and using a flexible electrode to couple local discharge to generate a pulse current signal;

[0010] Step S2, the pulse current signal is converted into a voltage signal through a pulse current detection impedance;

[0011] Step S3, the voltage signal is amplified by a signal amplification module set to a specific frequency, and the amplified voltage signal is transmitted to the acquisition and control module;

[0012] Step S4: When the amplified voltage signal is higher than the set threshold, it is considered that partial discharge exists, and the acquisition and control module sends a signal to the control communication module;

[0013] Step S5, the communication module modulates the amplified voltage signal into a carrier signal of a specific frequency, and then couples the carrier signal to the cable conductor for propagation through the flexible electrode;

[0014] Step S6, the temperature difference energy acquisition module obtains energy by relying on the temperature difference between the outer semi-conductive layer of the cable and the metal armor layer, and supplies energy to the signal amplification module, the acquisition and control module, and the communication module;

[0015] Step S7: At the end of the cable, a carrier signal in the cable conductor is obtained through a coupling device. The control communication modules at different positions use different carrier frequencies, and different bandpass filters are used to analyze the partial discharge conditions at different positions.

[0016] A further improvement of the technical solution of the present invention is that in step S6, the temperature difference between the outer semiconductive layer of the cable and the metal armor layer is 3-4°C.

[0017] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0018] 1. Compared with the traditional cable partial discharge detection device installed at the cable terminal or the middle joint, with the widespread application of long-length cables, the distance between each partial discharge monitoring device is more than 800 meters, and the internal defect signal of the cable is attenuated when transmitted to the outside, and the detection sensitivity is poor. By building multiple distributed pulse current detection units in the cable to detect the partial discharge inside the cable, the installation position is not limited by the joint position, and the defect signal attenuation is reduced by increasing the number of detection devices;

[0019] 2. Compared with the traditional cable partial discharge detection device which requires an external power supply, thereby increasing the investment level and reducing the reliability of the safe operation of the cable line in the tunnel, the present invention is powered by a temperature difference energy acquisition module, and does not require additional cable power supply;

[0020] 3. Compared with the traditional cable partial discharge detection device which transmits signals through optical fiber or external wireless networking, thereby increasing the project investment, the present invention couples the signal into the conductor for transmission, saving investment cost. At the end of the cable, the carrier signal in the cable conductor is obtained through a coupling device. The communication modules at different positions use different carrier frequencies. Therefore, the carrier signal in the cable conductor is obtained, and different bandpass filters can be used to analyze the partial discharge conditions at different positions, thereby realizing distributed detection of partial discharge at different positions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the internal structure of the cable of the present invention;

[0022] Figure 2 It is a schematic diagram of the structure of the distributed pulse current detection unit of the present invention;

[0023] Among them, 1. Distributed pulse current detection unit, 2. Cable conductor, 3. Inner semi-conductive layer, 4. Cable insulation layer, 5. Outer semi-conductive layer, 6. Metal shielding layer, 7. Inner sheath, 8. Metal armor layer, 9. Outer sheath, 10. Temperature difference energy acquisition module, 11. Flexible electrode, 12. Controllable switch, 13. Pulse current detection impedance, 14. Signal amplification module, 15. Collection and control module, 16. Communication module. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with embodiments:

[0025] like Figure 1As shown, the existing internal structure of the cable includes a conductor 2 and an inner semi-conductive layer 3, a cable insulation layer 4, an outer semi-conductive layer 5, a metal shielding layer 6, an inner sheath 7, a metal armor layer 8 and an outer sheath 9 which are sequentially arranged outside the conductor 2. Since the traditional cable partial discharge detection device is installed at the cable terminal head or the intermediate joint, the distance between each partial discharge monitoring device is more than 800 meters, and the internal defect signal of the cable is greatly attenuated when transmitted to the outside, and the detection sensitivity is poor. The present invention detects the partial discharge inside the cable by embedding multiple distributed pulse current detection units in the cable. The installation position is not limited by the joint position. By increasing the number of detection devices, the attenuation of the defect signal is reduced. A distributed detection system for partial discharge inside the cable of the present invention includes multiple distributed pulse current detection units 1 arranged between the outer semi-conductive layer 5 and the metal armor layer 8 inside the cable, and the distance between two adjacent distributed pulse current detection units 1 is 50-100m to ensure effective detection of small defect discharge.

[0026] like Figure 2 As shown, the distributed pulse current detection unit 1 includes a flexible electrode 11, a controllable switch 12, a pulse current detection impedance 13, a signal amplification module 14, an acquisition and control module 15, a communication module 16 and a temperature difference energy acquisition module 10. One end of the flexible electrode 11 is coupled to the cable insulation layer 4, and the other end is electrically connected to the controllable switch 12. The controllable switch 12 is used to adjust the connection mode of the flexible electrode 11. Through the control of the acquisition and control module 15, it is determined whether the whole system works in the signal detection mode or the communication signal sending mode.

[0027] The flexible electrode 11 is a circular metal structure. To obtain a better detection effect, the lower lead of the flexible electrode 11 is located at 0.618 times the radius of the flexible electrode 11. The acquisition and control module 15 is connected to the controllable switch 12 at one end and the communication module 16 at the other end. The pulse current detection impedance 13 is electrically connected to the controllable switch 12 at one end and the signal amplification module 14 at the other end. The signal amplification module 14 is electrically connected to the acquisition and control module 15. The signal amplification module 14, the acquisition and control module 15, and the communication module 16 are all electrically connected to the temperature difference energy extraction module 10. One end of the temperature difference energy extraction module 10 is electrically connected to the outer semi-conductive layer 5 and the other end is electrically connected to the metal armor layer 8.

[0028] A distributed detection method for partial discharge inside a cable comprises the following steps:

[0029] Step S1, using the cable insulation layer 4 as a coupling capacitor and using the flexible electrode 11 to couple the local discharge to generate a pulse current signal;

[0030] Step S2, the pulse current signal is converted into a voltage signal through the pulse current detection impedance 13;

[0031] Step S3, the voltage signal is amplified by the signal amplification module 14 set to a specific frequency, and the amplified voltage signal is transmitted to the acquisition and control module 15;

[0032] Step S4: When the amplified voltage signal is higher than the set threshold, it is considered that partial discharge exists, and the acquisition and control module 15 sends a signal to the control communication module 16;

[0033] Step S5, the communication module 16 modulates the amplified voltage signal into a carrier signal of a specific frequency, and then couples the carrier signal to the cable conductor 2 through the flexible electrode 11 for propagation;

[0034] Step S6, the heat source of the cable is the middle conductor 2, which is equivalent to thermal resistance from the inside to the outside, so the temperature of different layers of the cable is different. The temperature difference energy acquisition module 10 obtains energy by relying on the temperature difference between the outer semi-conductive layer 5 and the metal armor layer 8 of the cable. The temperature difference is 3-4°C, and supplies energy to the signal amplification module 14, the acquisition and control module 15, and the communication module 16. The power is supplied by the temperature difference energy acquisition module 10, and there is no need to connect an additional cable for power supply. Compared with the traditional cable partial discharge detection device, an external power supply is required, thereby increasing the investment level and reducing the reliability of safe operation of the cable line in the tunnel.

[0035] Step S7, at the end of the cable, the carrier signal in the cable conductor is obtained through the coupling device. The carrier frequencies used by the control communication modules 16 at different positions are different. Therefore, the carrier signal in the cable conductor is obtained, and the local discharge conditions at different positions can be analyzed through different bandpass filters. Compared with the problem of increasing engineering investment in traditional cable local discharge detection devices that transmit signals through optical fibers or external wireless networking, the present invention couples the signal into the conductor for transmission, saving investment costs, and detects local discharge inside the cable by building multiple distributed pulse current detection units into the cable. The installation position is not limited by the joint position, and the defect signal attenuation is reduced by increasing the number of detection devices.

Claims

1. A distributed detection system for partial discharge inside a cable, characterized in that: The invention comprises a plurality of distributed pulse current detection units (1) arranged between an outer semiconductive layer (5) and a metal armor layer (8) inside a cable, wherein the distributed pulse current detection units (1) comprise a flexible electrode (11), a controllable switch (12), a pulse current detection impedance (13), a signal amplification module (14), a collection and control module (15), a communication module (16) and a temperature difference energy acquisition module (10), wherein one end of the flexible electrode (11) is coupled to the cable insulation layer (4) and the other end is electrically connected to the controllable switch (12), and the collection and control module (15) is electrically connected to the controllable switch (12). ) one end of which is connected to a controllable switch (12) and the other end of which is connected to a communication module (16); one end of the pulse current detection impedance (13) is electrically connected to the controllable switch (12) and the other end of which is electrically connected to a signal amplification module (14); the signal amplification module (14) is electrically connected to a collection and control module (15); the signal amplification module (14), the collection and control module (15) and the communication module (16) are all electrically connected to a temperature difference energy extraction module (10); one end of the temperature difference energy extraction module (10) is electrically connected to an outer semi-conductive layer (5) and the other end of which is electrically connected to a metal armor layer (8); The distributed detection method for partial discharge inside the cable includes the following steps: Step S1, using the cable insulation layer (4) as a coupling capacitor and using the flexible electrode (11) to couple the local discharge to generate a pulse current signal; Step S2, the pulse current signal is converted into a voltage signal through a pulse current detection impedance (13); Step S3, the voltage signal is amplified by a signal amplification module (14) set to a specific frequency, and the amplified voltage signal is transmitted to a collection and control module (15); Step S4: When the amplified voltage signal is higher than a set threshold, it is considered that partial discharge exists, and at this time, the acquisition and control module (15) sends a signal to the control communication module (16); Step S5, the communication module (16) modulates the amplified voltage signal into a carrier signal of a specific frequency, and then couples the carrier signal to the cable conductor (2) for propagation through the flexible electrode (11); Step S6, the temperature difference energy acquisition module (10) obtains energy by relying on the temperature difference between the outer semi-conductive layer (5) of the cable and the metal armor layer (8), and supplies energy to the signal amplification module (14), the collection and control module (15), and the communication module (16); Step S7: At the end of the cable, a carrier signal in the cable conductor is obtained through a coupling device. The control communication modules (16) at different locations use different carrier frequencies, and different bandpass filters are used to analyze the partial discharge conditions at different locations.

2. A distributed detection system for partial discharge inside a cable according to claim 1, characterized in that: The distance between two adjacent distributed pulse current detection units (1) is 50-100m.

3. A distributed detection system for partial discharge inside a cable according to claim 1, characterized in that: The flexible electrode (11) is a circular metal structure, and the lower lead of the flexible electrode (11) is located at a position 0.618 times the radius of the flexible electrode (11).

4. A distributed detection system for partial discharge inside a cable according to claim 1, characterized in that: In step S6, the temperature difference between the outer semiconductive layer (5) of the cable and the metal armor layer (8) is 3-4°C.

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