A method and device for detecting live electrical connection defects of cable accessories lead seals

Abstract

The present invention discloses a method and device for detecting live electrical connection defects of lead seals of cable accessories. A current signal with known changes and distinguished from the industrial frequency is coupled and injected into the lead seal, which will produce a changing magnetic field on the surface of the lead seal. A signal sensor with a coupling coil is placed on the outer surface of the lead seal, and an induced electromotive force is generated in the coupling coil. The difference in the surface magnetic field is detected by the sensor, thereby realizing live detection of electrical connection defects at the lead seal point. The sensor can be moved axially once along the lead seal of the cable accessory to complete the test of the electrical connection of the lead seal. The operation is flexible, simple and convenient.

Description

Technical Field

[0001] The invention relates to a live detection method and device for electrical connection defects of cable accessory lead seals, belonging to the technical field of power transmission and transformation equipment. Background Art

[0002] At present, poor lead sealing connection of cable accessories can easily cause suspended discharge of metal inside the cable aluminum sheath or cable accessories, thus causing cable failure. Since the cable accessory lead sealing is wrapped with heat shrink tubing on the outside, and its inner side is in contact with the tail tube and aluminum sheath, the internal electrical connection of the lead sealing cannot be seen with the naked eye, which increases the difficulty of detecting the electrical connection of the lead sealing. The traditional method mainly uses eddy current flaw detection to detect the lead sealing defects of cable accessories inside the heat shrink tubing. Its main principle is to use the difference in magnetic permeability between air and metal. When the surface of the lead sealing defect is cracked or severely uneven, it causes the change of the induced voltage or induced current of the test coil, thereby judging the lead sealing defect. However, when the surface of the lead sealing part is smooth and the internal electrical connection is poorly contacted, this method is difficult to detect, and this method requires the probe to slide along the lead sealing surface, which is complicated to operate and has a long detection cycle. Summary of the invention

[0003] Purpose: In order to overcome the deficiencies in the prior art, the present invention provides a method and device for detecting electrical connection defects of lead seals in cable accessories under power supply, which can detect electrical connection defects of lead seals inside cables under power supply, and the operation is simple, convenient and efficient.

[0004] Technical solution: To solve the above technical problems, the technical solution adopted by the present invention is: a method for detecting electrical connection defects of cable accessory lead seals under voltage, comprising: injecting a current signal into the cable accessory lead seals;

[0005] By moving several sensors placed on the outer surface of the lead seal of the cable accessories, several induced electromotive forces on the surface of the lead seal are obtained;

[0006] Find out the maximum induced potential and the minimum induced potential in the sensor. When the absolute value of the difference between the maximum induced potential and the minimum induced potential is greater than the set threshold, there is an electrical connection defect in the lead sealing part of the cable accessories.

[0007] Furthermore, a current signal is injected into the lead seal of the cable accessories, specifically:

[0008] The current signal emitted by the coupling injection signal source is transmitted to the aluminum sheath of the cable body or the grounding lead of the cable accessories, and the current signal is transmitted to the lead sealing part of the cable accessories through the aluminum sheath of the cable body or the grounding lead of the accessories;

[0009] Furthermore, by moving several sensors placed on the outer surface of the lead seal of the cable accessories, several induced electromotive forces on the surface of the lead seal are obtained, specifically:

[0010] A number of sensors are made into a cylindrical shape by steering knuckle buckles and surround the surface of the lead-sealed part of the cable accessory. The sensors are moved axially along the lead-sealed part of the cable accessory through the test support rod. During the movement, the induced potential on the surface of the lead-sealed part is obtained through each sensor.

[0011] A live detection device for electrical connection defects of cable accessories lead seals, characterized by comprising: a coupled injection signal source, a signal sensor, and a signal display device connected in sequence;

[0012] The coupled injection signal source is used to inject current signals into the lead seal of the cable accessories; the signal sensor is used to obtain a number of induced electromotive forces on the surface of the lead seal of the cable accessories after the current signal is injected; and the signal display device is used to display the obtained several induced electromotive forces.

[0013] Furthermore, the coupling injection signal source includes a detachable through-hole transformer and a signal generator which are connected to each other; the signal generator is used to send a current signal to the detachable through-hole transformer, and the detachable through-hole transformer is used to be detachably mounted on the aluminum sheath of the cable body or the grounding lead of the cable accessory, and couple the signal sent by the signal generator into the aluminum sheath of the cable body or the grounding lead of the cable accessory, and transmit it to the lead sealing part of the cable accessory.

[0014] Furthermore, the signal types emitted by the signal generator include pulse signals, rectangular wave signals and triangular wave signals.

[0015] Furthermore, the signal sensor includes a plurality of sensors; the plurality of sensors are arranged on the surface of the lead sealing part of the cable accessory through a steering knuckle buckle steering sleeve.

[0016] Furthermore, the sensor includes a metal wire core and a coupling coil wound on the metal wire core; the steering knuckle buckles are installed at both ends of the metal wire core.

[0017] Furthermore, a roller is installed on one side of the sensor close to the lead sealing part of the cable accessories.

[0018] Furthermore, the signal sensor also includes a test support rod, one end of which is mechanically connected to the sensor, and the other end is a handle, through which the position of the sensor test is controlled.

[0019] The present invention injects a current signal into the lead seal of the cable accessory; moves a plurality of sensors placed on the outer surface of the lead seal of the cable accessory to obtain a plurality of induced electromotive forces on the surface of the lead seal; finds the maximum induced electromotive force and the minimum induced electromotive force in the sensor, and when the absolute value of the difference between the maximum induced electromotive force and the minimum induced electromotive force is greater than a set threshold value, an electrical connection defect exists in the lead seal of the cable accessory;

[0020] The sensor is made into a cylindrical shape through the steering knuckle buckle and wrapped around the lead sealing part of the cable accessory. The test can be completed by moving it axially along the lead sealing part of the cable accessory once. The operation is flexible, simple and convenient, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is an equivalent schematic diagram of cracking of lead seal of cable accessories;

[0022] Figure 2 This is a schematic diagram of the magnetic force lines penetrating the sensor when the cable accessories are normal;

[0023] Figure 3 This is a schematic diagram of the magnetic field lines penetrating into the sensor when the cable has crack defects;

[0024] Figure 4 It is a schematic diagram of the structure of a detection device in a specific embodiment of the present invention;

[0025] Figure 5 A schematic diagram of a sensor structure in a specific embodiment of the present invention;

[0026] The meanings of the marks in the figure are: 1-coupled injection signal source, 101-detachable through-core transformer, 102-signal generator, 2-signal sensor, 201-sensor, 202-test support rod, 3-signal display device. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings.

[0028] Cable accessory seals are used to connect accessory metal tubular parts, such as aluminum sheath and terminal tail tube, aluminum sheath and connector copper shell. The seals themselves are also tubular.

[0029] A current signal with known changes and different from the power frequency current signal is injected into the cable lead sealing part through the grounding lead coupling of the cable accessories. According to the Biot-Savart law, the current signal will produce a changing magnetic field on the lead sealing surface. A signal sensor with a coupling coil is placed on the outer surface of the lead sealing. According to Faraday's law of electromagnetic induction, an induced electromotive force will be generated in the coupling coil. If the electrical connection of the lead sealing part is poor, the uniformity of the current distribution inside the coupling coil will be changed, and the uniformity of the magnetic field on the surface of the lead sealing part will be changed at the same time. The difference of the magnetic field on the surface of the lead sealing part is detected by the sensor, thereby realizing the live detection of electrical connection defects in the lead sealing part.

[0030] Embodiment 1:

[0031] like Figure 4 As shown, a device for detecting live electrical connection defects of cable accessory lead seals comprises a coupled injection signal source 1, a signal sensor 2, and a signal display device 3 connected in sequence.

[0032] The coupling injection signal source 1 comprises a detachable through-core transformer 101 and a signal generator 102 connected to each other. A clamping component is provided on the detachable through-core transformer for realizing the opening and closing of the through-core transformer, and the detachable through-core transformer can be directly inserted without changing the aluminum sheath of the cable body or the grounding lead structure of the cable accessories.

[0033] The detachable through-hole transformer 101 is used to inject a current signal that changes and is different from the power frequency current signal into the aluminum sheath of the cable body or the grounding lead of the accessory. The detachable through-hole transformer 101 is connected to the signal generator 102 through a metal shielded connecting lead;

[0034] The signal from the signal generator 102 is coupled to the cable body aluminum sheath or the cable accessory grounding lead by the detachable through-hole transformer 101 using the electromagnetic induction principle, and is transmitted to the cable accessory lead sealing part through the cable body aluminum sheath or the cable accessory grounding lead. The signal generator 102 can send pulse signals, rectangular wave models, and triangular wave signals.

[0035] The signal sensor 2 includes a plurality of sensors 201 and a test support rod 202 .

[0036] Several sensors 201 are turned into a cylindrical shape through the steering knuckle buckle 20103, and are sleeved on the surface of the lead sealing part of the cable accessories. The cylindrical sensor can test the magnetic induced electromotive force of the outer surface of the lead sealing part by moving axially along the surface of the lead sealing part of the cable accessories once. The number of sensors to be assembled can be determined according to the outer diameter of the lead sealing part of the cable accessories, and can be assembled flexibly to complete the covering of the lead sealing part of the cable accessories. The signal sensor 2 is connected to the signal display device 3 through a radio frequency cable to transmit the test signal to the signal display device. The number of radio frequency cables is not less than 1 and is at least equal to the number of sensors. One radio frequency cable is connected to one sensor.

[0037] One end of the test support rod is mechanically connected to the sensor, and the other end is a handle, through which the position of the sensor test can be controlled.

[0038] like Figure 5 As shown, the sensor 201 includes a metal wire core 20101 and a coupling coil 20102 wound on the metal wire core;

[0039] The metal wire core 20101 and the coupling coil 20102 inductively collect the alternating coupling signal passing through the surface of the lead sealing part of the cable accessory. Preferably, the metal wire core 20101 is made of a high magnetic permeability material.

[0040] The steering knuckle buckle 20103 is installed at both ends of the metal wire core 20101 of the sensor, and is made of non-magnetic material, and can be connected and steered.

[0041] A roller 20104 is also installed on one side of the sensor 201 close to the lead sealing part of the cable accessory. During the test, the roller contacts and slides with the outer surface of the lead sealing part of the cable accessory to reduce friction.

[0042] The signal display device 3 is connected to the signal sensor 2 via a data lead, receives the electrical signal tested by the signal sensor 2, and displays the data.

[0043] Embodiment 2:

[0044] like Figure 1 As shown in the figure, the non-electrical connection of the cable lead seal will affect the transmission channel of the coupling current. The cable accessory lead seal part is equivalent to a cylindrical tubular structure. Figure 1 There is a defective electrical connection.

[0045] Due to the magnetic effect of the current, a magnetic field is generated around the current channel in the tubular structure, and the magnitude of the magnetic field is related to the magnitude of the coupled injection current and the distance between the test point and the central axis of the current channel.

[0046] like Figure 2 and 3 As shown, when cracks occur in the lead sealing component, the current channel changes, causing the magnetic field strength around the tubular structure to change. By detecting the change in magnetic field or magnetic induction intensity, non-electrical connection defects of the lead sealing can be detected and determined.

[0047] A method for detecting live electrical connection defects of cable accessories lead seals, comprising the steps of:

[0048] Step 1, a plurality of sensors 201 are turned into a cylindrical shape through a steering knuckle buckle 20103 and are placed around the surface of the lead-sealed part of the cable accessories, and the signal emitted by the signal generator 102 coupled to the signal source 1 is transmitted to the aluminum sheath of the cable body or the grounding lead of the cable accessories through the detachable through-core transformer 101, and the current signal is transmitted to the lead-sealed part of the cable accessories through the aluminum sheath of the cable body or the grounding lead of the accessories;

[0049] Step 2: Move the signal sensor once along the axial direction of the lead sealing part of the cable accessory through the test support rod 202. During the movement, the induced potential U on the surface of the lead sealing part is obtained through each sensor. i ,

[0050] U i is the induced potential of the i-th sensor;

[0051] Step 3: Find the maximum sensor induced potential U max =Max(U i ); the smallest sensor induced potential U min =Min(U i); Considering the errors caused by the sensor angle and position, the detection criteria are set as:

[0052] When|U max -U min |≤ΔU, indicating that the current channel inside the cable lead seal is axially symmetrical and the cable accessories lead seal is normal;

[0053] When|U max -U min |>ΔU, indicating that the current channel inside the cable seal is not axisymmetric and there is an electrical connection defect in the cable accessory seal. ΔB is the error value caused by the sensor angle and position, unit T; ΔU is the error value caused by the sensor angle and position, unit V.

[0054] Embodiment 3:

[0055] This embodiment uses 6 groups of sensors, namely N1, N2, N3, N4, N5, and N6, and their distances r from the center of the current channel in the cable accessory lead seal are set to r1, r2, r3, r4, r5, and r6 respectively. The magnetic induction intensity passing through the center of the sensor is taken as the average magnetic induction intensity of the sensor, which is set to B1, B2, B3, B4, B5, and B6 respectively, and the induced potential is set to U1, U2, U3, U4, U5, and U6 respectively. The signal display device displays the induced potential read by the sensor.

[0056] In this embodiment, Figure 2 As shown in Figure 2, when the sensor detects the L1 and L3 intervals in Figure 2, the cable accessories in the L1 and L3 intervals are sealed normally. Since the sensors are symmetrical to the current channel axis and have the same model, that is, r1=r2=r3=r4=r5=r6 and other n, I, S parameters are equal, substituting into formulas (1) and (2), we get B1=B2=B3=B4=B5=B6; U1=U2=U3=U4=U5=U6.

[0057] When |B max -B min |=0 or |U max -U min |=0, (at this time ΔB=0, ΔU=0) indicates that the lead sealing of the cable accessories is not defective.

[0058] When the sensor detects the L2 interval as shown in the figure, Figure 3 As shown, the cable is cracked in the L2 interval, and the sensor distance current channel is non-axisymmetric, that is, r1≠r2=r6≠r3=r5≠r4. Other parameters are equal. Substituting into formulas (1) and (2), it can be seen that B1≠B2=B6≠B3=B5≠B4; U1≠U2=U6≠U3=U5≠U4,

[0059] When |B max -Bmin |≠0 or |U max -U min |≠0, indicating that the lead seal of the cable accessories is defective.

[0060] The present invention provides a live detection device and method for electrical connection defects of cable accessory lead seals. The device and method can operate under power conditions. The device and method can inject signals into the aluminum sheath of the cable body or the grounding lead of the cable accessory by coupling, and transmit the signals to the lead sealing part of the cable accessory. The signal sensor can be moved axially once along the lead sealing part of the cable accessory to complete the test. The device and method are flexible, simple and convenient to operate, and have good application prospects.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for detecting live electrical connection defects of cable accessories lead seals, characterized in that: include: Inject current signal into the lead seal of cable accessories; By moving several sensors placed on the outer surface of the lead seal of the cable accessories, several induced electromotive forces on the surface of the lead seal are obtained; Find out the maximum induced potential and the minimum induced potential in the sensor. When the absolute value of the difference between the maximum induced potential and the minimum induced potential is greater than the set threshold, there is an electrical connection defect in the lead sealing part of the cable accessories. Inject current signal into the lead seal of cable accessories, specifically: The current signal emitted by the coupling injection signal source is transmitted to the aluminum sheath of the cable body or the grounding lead of the cable accessories, and the current signal is transmitted to the lead sealing part of the cable accessories through the aluminum sheath of the cable body or the grounding lead of the accessories.

2. According to the method for detecting the electrical connection defect of the lead seal of a cable accessory under the power supply condition as described in claim 1, it is characterized by: By moving several sensors placed on the outer surface of the lead seal of the cable accessories, several induced electromotive forces on the surface of the lead seal are obtained, specifically: A number of sensors are made into a cylindrical shape by steering knuckle buckles and surround the surface of the lead-sealed part of the cable accessory. The sensors are moved axially along the lead-sealed part of the cable accessory through the test support rod. During the movement, the induced potential on the surface of the lead-sealed part is obtained through each sensor.

3. A device for detecting electrical connection defects of cable accessories, characterized in that: include: A coupled injection signal source, a signal sensor, and a signal display device connected in sequence; The coupled injection signal source is used to inject current signals into the lead seals of cable accessories; The signal sensor is used to obtain a number of induced electromotive forces on the surface of the lead sealing part of the cable accessories after the current signal is injected; the signal display device is used to display the obtained several induced electromotive forces; The coupling injection signal source comprises a detachable through-hole transformer and a signal generator which are connected to each other; the signal generator is used to send a current signal to the detachable through-hole transformer, and the detachable through-hole transformer is used to be detachably mounted on the aluminum sheath of the cable body or the grounding lead of the cable accessories, and couple the signal sent by the signal generator into the aluminum sheath of the cable body or the grounding lead of the cable accessories, and transmit it to the lead sealing part of the cable accessories; The signal sensor comprises a plurality of sensors; the plurality of sensors are arranged on the surface of the lead sealing part of the cable accessories through a steering knuckle buckle steering sleeve.

4. A cable accessory lead seal electrical connection defect live detection device according to claim 3, characterized in that: The signal types emitted by the signal generator include pulse signals, rectangular wave signals and triangular wave signals.

5. A cable accessory lead seal electrical connection defect live detection device according to claim 3, characterized in that: The sensor comprises a metal wire core and a coupling coil wound on the metal wire core; the steering knuckle buckles are installed at both ends of the metal wire core.

6. A cable accessory lead seal electrical connection defect live detection device according to claim 3, characterized in that: A roller is also installed on one side of the sensor close to the lead sealing part of the cable accessories.

7. A cable accessory lead sealing electrical connection defect live detection device according to claim 3, characterized in that: The signal sensor also includes a test support rod, one end of which is mechanically connected to the sensor, and the other end is a handle, through which the position of the sensor test is controlled.

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