Cable partial discharge inspection device

Abstract

The utility model discloses a cable partial discharge inspection device, which comprises a bipolar plate partial discharge sensor, the bipolar plate partial discharge sensor comprises a lower pressing plate, a main polar plate, an upper pressing plate and a voltage dividing polar plate, the main polar plate is of an opening structure, the inner side of the main polar plate is used for placing a cable, and the main polar plate and a cable core wire or a shielding layer form a coupling capacitor; the upper pressing plate and the lower pressing plate are both made of insulating materials, and the main polar plates and the voltage-dividing polar plates on the two sides of the upper pressing plate form voltage-dividing coupling capacitors. According to the utility model, the main pole plate and the voltage-dividing pole plate form a voltage-dividing coupling capacitor, and the voltage signals at the two ends of the voltage-dividing capacitor are measured to achieve the purpose of measuring the partial discharge signal of the cable body; a sensor adopting an electric field coupling principle is used for measuring high-frequency signals within the range of 1MHz-100MHz generated by partial discharge, the sensor can be placed at any position of a cable body, partial discharge signals in a medium-voltage three-core cable of 35kV and below are detected, and the problem that live inspection can not be carried out when a distribution network high-frequency current sensor is used in operation is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of power cable insulation monitoring, in particular to a cable partial discharge inspection device. Background Art

[0002] Cable partial discharge live inspection generally adopts the high-frequency current method to measure partial discharge. This method generally uses an open-type high-frequency current sensor stuck on the cable grounding wire to sense the partial discharge signal generated in the cable. Since the 3-core cable of the 35kV and below distribution network generally adopts a single-point grounding method, the copper shielding layers of the middle joints between the two sections of the cable are interconnected, and the high-frequency current sensor cannot measure partial discharge at the middle joint. In addition, the cable terminal is generally installed in the switch cabinet or ring network cabinet. For safety reasons, these electrical cabinets generally have five protection functions. The cabinet door cannot be opened during operation, and the high-frequency current sensor cannot be used to measure partial discharge at the cable terminal. This brings difficulties to the inspection work. The specific problems are as follows: (1) 35kV and below medium voltage For three-core cables, the traditional partial discharge measurement method cannot detect at the middle joint of the cable. It can only detect at the ground wire at one end of the cable. For cables longer than 2 km, there is a risk that the partial discharge signal cannot be detected due to attenuation. (2) For medium-voltage three-core cables of 35 kV and below, the grounding connection wire is often inside the switch cabinet / ring network cabinet with five protection functions. During live inspection, it is impossible to use a high-frequency current sensor to detect at the terminal ground wire. (3) Medium-voltage three-core cables of 35 kV and below are generally buried directly. There is only a vertical shaft at the middle joint of the cable. Water often accumulates underground and toxic gases may exist. There are safety risks for inspection personnel to go down the shaft. In addition, the cable terminals buried in the ground of the pole tower require high-altitude work during inspection, which also poses a safety risk. Utility Model Content

[0003] Purpose of the utility model: The purpose of the utility model is to provide an inspection device which can detect partial discharge signals inside a medium voltage 3-core cable of 35kV and below at any position of the cable body.

[0004] Technical solution: The cable partial discharge inspection device of the utility model comprises a bipolar plate partial discharge sensor, which comprises a lower pressure plate, a main pole plate, an upper pressure plate and a voltage-dividing pole plate from bottom to top. The main pole plate is an open structure, and the inner side is used to place the cable. The main pole plate and the cable core wire or the shielding layer form a coupling capacitor; the upper pressure plate and the lower pressure plate are both made of insulating material, and the main pole plates on both sides of the upper pressure plate and the voltage-dividing pole plates form a voltage-dividing coupling capacitor.

[0005] Preferably, the main pole plate is made of stainless steel or manganese steel, and the outer side of the main pole plate is sealed by rubber.

[0006] Optionally, the main pole plate is elastic, and consists of a first circular arc, a horizontal transition portion, and a second circular arc; utilizing the elasticity of the pole plate, it can be inserted into cables with different outer diameters for measurement.

[0007] Optionally, the main pole plate is an n-shaped rigid structure, and the diameter of the n-shaped semicircular arc matches the outer diameter of the cable.

[0008] Furthermore, the bipolar plate partial discharge sensor also includes an N-type RF female socket, which is connected to the input end of an amplifier or a high-frequency partial discharge detector with a filtering amplification circuit through a coaxial cable to transmit the measurement signal of the bipolar plate partial discharge sensor thereto.

[0009] Furthermore, the cable partial discharge inspection device also includes an upper connector, a lower connector and a locking mechanism, and the upper connector and the lower connector are rotatably connected via a connecting component.

[0010] Preferably, the upper end of the upper connector is an insulating rod interface.

[0011] Preferably, the locking mechanism is composed of two pairs of thin cylinders, a through-rod and an eccentric handle, and the thin cylindrical surfaces facing each other are rough surfaces.

[0012] Furthermore, the amplifier includes a shielded shell, a signal input interface, a signal output interface, a power switch, a charging interface and a circuit module; the circuit module includes a 100MHz low-pass filter, a signal amplification circuit and a power management module.

[0013] Beneficial effects: Compared with the prior art, the utility model has the following advantages: 1. The utility model forms a voltage-dividing coupling capacitor through the main plate and the voltage-dividing plate, and measures the voltage signal at both ends of the voltage-dividing capacitor to achieve the purpose of measuring the partial discharge signal of the cable body; 2. The utility model uses a sensor based on the electric field coupling principle to measure the high-frequency signal in the range of 1MHz to 100MHz generated by partial discharge. The sensor can be placed at any position of the cable body, and detects the internal discharge signal of the medium-voltage 3-core cable of 35kV and below, solving the problem that the high-frequency current sensor cannot be used for live inspection during operation; 3. The utility model can be used to measure the high-frequency signal generated by the partial discharge in the range of 1MHz to 100MHz. The new type adopts a bipolar plate capacitor voltage division method to avoid coupling higher voltage signals and damaging measuring instruments; 4. The main board of the utility model is made of stainless steel elastic material and coated with rubber, which is suitable for medium-voltage three-core cable detection of various diameters; 5. The utility model adopts an upper connector interface that matches the power insulating rod. The insulating rod can be installed during underground cable inspection, and partial discharge live inspection can be carried out quickly and safely. The working inspection personnel do not need to go down the well to carry out operations, avoiding the safety risks of underground operations; 6. The connection mechanism of the utility model can adjust the angle and connect to the insulating rod, so that partial discharge detection of the underground cable on the rod can be carried out without climbing. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of the utility model;

[0015] Figure 2 A schematic diagram of cable detection for the utility model;

[0016] Figure 3 It is a structural schematic diagram of a bipolar plate partial discharge sensor;

[0017] Figure 4 The equivalent circuit diagram of the main plate and the voltage divider plate;

[0018] Figure 5 It is the working diagram of the amplifier;

[0019] Figure 6 Schematic diagram of the structure of the main pole plate with an n-shaped rigid structure. DETAILED DESCRIPTION

[0020] The technical solution of the utility model is further described below in conjunction with the accompanying drawings.

[0021] The cable partial discharge inspection device described in the utility model includes a bipolar plate partial discharge sensor, which includes a lower pressure plate 4, a main pole plate 1, an upper pressure plate 3, a voltage-dividing pole plate 2, a shell 5 and an N-type radio frequency female socket 6. The main pole plate is an open structure, and the main pole plate and the cable core wire or the shielding layer form a coupling capacitor; the main pole plate 1 on both sides of the upper pressure plate 3 and the voltage-dividing pole plate 2 form a voltage-dividing coupling capacitor, and the voltage signal at both ends of the voltage-dividing capacitor is measured to achieve the purpose of measuring the partial discharge signal of the cable body.

[0022] The main plate 1 is made of elastic stainless steel or manganese steel. The inner side is used to place the cable, and the outer side is sealed with a certain thickness of rubber. The main plate is an open structure. The elasticity of the plate can be used to insert cables with different outer diameters for measurement. Figure 2 As shown. The main pole plate 1 and the cable core wire or shielding layer form a coupling capacitor; the upper pressure plate 3 is made of insulating material, and the main pole plates 1 on both sides thereof and the voltage-dividing pole plate 2 form a voltage-dividing coupling capacitor; the lower pressure plate 4 is made of insulating material and is used to fix the main pole plate, the N-type RF female socket 6 and the voltage-dividing pole plate 2 are tightly connected by screws, the N-type RF female socket 6 and the input end of the amplifier are connected by a coaxial cable, and the core wire of the coaxial cable and the main pole plate are connected by a copper wire.

[0023] The cable partial discharge inspection device also includes an upper connector 7, a lower connector 8 and a locking mechanism. The upper connector 7 and the lower connector 8 are rotatably connected through a connecting component 9, and the angle between them can be adjusted. The upper end of the upper connector 7 is an insulating rod interface, which can be connected to a 32mm standard insulating rod. The lower connector 8 is connected to the bipolar plate partial discharge sensor through an M14 screw. The locking mechanism consists of two pairs of thin cylinders, a through rod, and an eccentric handle. The two opposite thin cylindrical surfaces are rough surfaces. After the locking handle is tightened, the friction between them is increased.

[0024] In one embodiment, the bipolar plate partial discharge sensor can be directly connected to an existing high-frequency partial discharge detector with a filtering and amplifying circuit, or the partial discharge signal measured by the bipolar plate partial discharge sensor can be filtered and amplified through an independent amplifier and connected to an oscilloscope or other analytical instruments that do not have filtering and amplifying capabilities.

[0025] The amplifier is an independent module, including a shielded shell, a signal input interface, a signal output interface, a power switch, a charging interface and a circuit module; wherein the circuit module is composed of a 100MHz low-pass filter, a signal amplification circuit, a power management module and a rechargeable lithium battery. The signal measured by the bipolar plate partial discharge sensor is transmitted to the amplifier signal input terminal through the N-type connector 6. The working principle of the circuit module is as follows Figure 5 shown.

[0026] The bipolar plate partial discharge sensor of the utility model is as follows Figure 3 As shown, the voltage-dividing capacitor formed by the main plate 1 and the voltage-dividing plate 2 is as follows Figure 4 In the equivalent circuit diagram shown in FIG. 1 , C2 measures the voltage signal at both ends of the voltage-dividing capacitor to achieve the purpose of measuring the partial discharge signal of the cable body.

Claims

1. A cable partial discharge inspection device, characterized in that: The invention comprises a bipolar plate partial discharge sensor, which comprises, from bottom to top, a lower pressing plate (4), a main pole plate (1), an upper pressing plate (3) and a voltage-dividing plate (2). The main pole plate is an open structure, the inner side of which is used to place a cable, and the main pole plate and the cable core wire or shielding layer form a coupling capacitor; the upper pressing plate (3) and the lower pressing plate (4) are both made of insulating material, and the main pole plates (1) on both sides of the upper pressing plate (3) and the voltage-dividing plate (2) form a voltage-dividing coupling capacitor.

2. The cable partial discharge inspection device according to claim 1, characterized in that: The main pole plate (1) is made of stainless steel or manganese steel, and the outer side of the main pole plate is sealed by rubber.

3. The cable partial discharge inspection device according to claim 2 is characterized in that: The main pole plate (1) is of elastic type.

4. The cable partial discharge inspection device according to claim 3 is characterized in that: The main pole plate (1) consists of a first circular arc, a horizontal transition portion and a second circular arc.

5. The cable partial discharge inspection device according to claim 2, characterized in that: The main pole plate (1) is an n-shaped rigid structure.

6. The cable partial discharge inspection device according to claim 1, characterized in that: The bipolar plate partial discharge sensor also includes an N-type radio frequency female socket (6), which is connected to an input end of an amplifier or a high-frequency partial discharge detector having a filter amplifier circuit via a coaxial cable to transmit a measurement signal of the bipolar plate partial discharge sensor to the amplifier or the input end of a high-frequency partial discharge detector having a filter amplifier circuit.

7. The cable partial discharge inspection device according to claim 1, characterized in that: It also comprises an upper connecting head (7), a lower connecting head (8) and a locking mechanism. The upper connecting head (7) and the lower connecting head (8) are rotatably connected via a connecting component (9).

8. The cable partial discharge inspection device according to claim 7, characterized in that: The upper end of the upper connector (7) is an insulating rod interface.

9. The cable partial discharge inspection device according to claim 7, characterized in that: The locking mechanism is composed of two pairs of thin cylinders, a through-core rod and an eccentric handle, and the thin cylinder surfaces facing each other are rough surfaces.

10. The cable partial discharge inspection device according to claim 6, characterized in that: The amplifier includes a shielding shell, a signal input interface, a signal output interface, a power switch, a charging interface and a circuit module; the circuit module includes a 100MHz low-pass filter, a signal amplification circuit and a power management module.

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