CN116047351A

CN116047351A - Novel adjustable open-close type power equipment leakage current detection device

Info

Publication number: CN116047351A
Application number: CN202211309612.XA
Authority: CN
Inventors: 李永福; 蒋西平; 龙英凯; 王谦; 张施令; 杜茗茗; 汪金刚; 胡晓旭; 傅雅梦; 李思全; 罗骁枭; 徐禄文; 吴照国; 杨勃
Original assignee: Electric Power Research Institute of State Grid Chongqing Electric Power Co Ltd; State Grid Corp of China SGCC
Current assignee: Electric Power Research Institute of State Grid Chongqing Electric Power Co Ltd; State Grid Corp of China SGCC
Priority date: 2022-10-25
Filing date: 2022-10-25
Publication date: 2023-05-02

Abstract

The invention relates to the technical field of weak current measurement, and provides a novel adjustable open-close type power equipment leakage current detection device which comprises a base assembly, a magnetic focusing ring, a sensing assembly, a controller, a cable shielding piece and a circuit shielding piece, wherein the base assembly is used for clamping a cable to be tested in an open-close mode, the magnetic focusing ring is used for collecting a magnetic field generated by the leakage current of the cable to be tested, the sensing assembly is used for detecting the intensity of the magnetic field, and the cable shielding piece and the circuit shielding piece are used for shielding external electromagnetic interference. According to the leakage current detection device provided by the invention, under the condition that the working of an original circuit is not influenced, the cable to be detected can be clamped into the magnetic focusing ring, and the cable shielding piece and the circuit shielding piece are used for shielding an external electromagnetic field, so that the detection environment at the cable to be detected is kept free from external interference, and a more accurate leakage current result is obtained.

Description

Novel adjustable open-close type power equipment leakage current detection device

Technical Field

The invention relates to the technical field of weak current measurement, in particular to a novel adjustable open-close type leakage current detection device for power equipment.

Background

In recent years, with the rapid development of the number and types of power equipment, the on-line monitoring of the insulation performance of the power equipment with an insulation layer such as a lightning arrester, an insulator and a sensor sleeve and the like and the real-time inspection of the running performance of the power equipment are particularly important for the stable and reliable running of a power system. The magnitude of leakage current is an important means for reflecting the insulation condition of equipment, the leakage current is often in the milliamp or microampere level, and a strong power frequency electromagnetic field exists in a power grid operation environment with high operation voltage level and large current, so that leakage current detection is easy to be interfered by the power frequency electromagnetic field, and the detection is inaccurate. The reason is that there is a method of collecting and enhancing the magnetic field signal formed by the leakage current through the magnetic focusing ring to reversely determine the magnitude of the leakage current, but the electromagnetic field generated by the circuit of the testing device itself and the interference of the external electromagnetic field can affect the measured current value, resulting in inaccurate measurement result.

Meanwhile, the existing leakage current detection needs to disconnect an original circuit, and the circuit is connected again after the cable to be detected is matched with the detection device, so that the operation is complex, the process is complex, the non-intervention operation is difficult to realize, and the leakage current detection work is not facilitated to be performed rapidly.

Therefore, a more reasonable technical scheme is required to be provided, and the technical problems in the prior art are solved.

Disclosure of Invention

In order to overcome at least one of the above-mentioned drawbacks, the present invention proposes a novel adjustable open-close type power equipment leakage current detection device, and through an open-close type detection structure, the non-intrusive matching with a cable to be detected is realized, so that the leakage current detection efficiency is improved; and the electromagnetic field outside the cable to be detected can be shielded, so that the influence on weak current detection is avoided, and the detection accuracy is improved.

In order to achieve the above object, the leakage current detection device disclosed by the present invention may adopt the following technical scheme:

novel adjustable open-close type power equipment leakage current detects device includes:

the base assembly comprises a fixed seat and a movable seat which are relatively opened and closed, and the opening and closing surfaces of the fixed seat and the movable seat form a clamping structure for clamping a cable to be tested;

the magnetic collecting ring is connected with the fixing seat and made of magnetic materials, and is aligned with the clamping structure to enable the cable to be tested to pass through the middle of the magnetic collecting ring, and an air gap for clamping the cable to be tested is formed in the magnetic collecting ring;

the sensing assembly is connected with the fixing seat and turned over, and the sensing assembly is turned over to enter the air gap opening or turned over to leave the air gap opening; the sensing component is used for detecting magnetic field signals generated by interaction of the cable to be tested and the magnetic focusing ring when the cable to be tested passes through the middle of the magnetic focusing ring;

the controller is electrically connected with the sensing assembly and is used for receiving and processing the magnetic field signals detected by the sensing assembly;

the cable shielding piece comprises two shielding parts which are movably arranged on the fixed seat and are opened and closed relatively, an air gap opening of the magnetic focusing ring is exposed when the two shielding parts are opened, the magnetic focusing ring and a testing section of the cable to be tested are closed when the two shielding parts are closed, and a non-testing section of the cable to be tested penetrates out of the cable shielding piece;

the circuit shielding piece covers the controller and moves relative to the fixed seat, the circuit shielding piece drives the controller and the sensing component to move and expose the air gap opening of the magnetic focusing ring when moving upwards, and the sensing component is placed into the air gap opening when the circuit shielding piece moves downwards to be attached to the base component.

According to the leakage current detection device disclosed by the invention, through the fixed seat and the movable seat which are arranged in an opening-closing manner, an air gap of the magnetic ring can be formed, a cable to be detected can be placed in and pass through the middle part of the magnetic ring without intervention of an original power supply circuit system, a magnetic field generated by the cable to be detected is collected by the magnetic ring, and meanwhile, electromagnetic shielding is carried out through the cable shielding piece and the circuit shielding piece, so that no environment interference is caused in the detection process; the sensing assembly is arranged in the air gap, and the controller is arranged outside the magnetic focusing ring, so that electromagnetic field induction detection generated by leakage current can be realized, and interference generated by an electromagnetic field generated by a circuit of the controller is avoided.

Further, in the present invention, the possible scheme of the clamping structure is not limited only, and may be a plurality of possible schemes, and optimization is performed herein and one of the possible options is given below: the clamping structure comprises clamping wire grooves respectively arranged on the fixed seat and the movable seat. When the scheme is adopted, the clamping wire grooves can clamp cables to be tested with different sizes, so that the cables to be tested are kept at the centered detection positions, the magnetic field generated by leakage current of the cables to be tested is collected on the magnetic collecting ring more accurately, and the detection precision can be improved.

Further, in the invention, considering that when different cables are clamped, the distance between the clamping surfaces of the fixed seat and the movable seat can be changed, if the diameter of the cable to be tested is too small, the clamping surfaces can be contacted, so that the stable clamping of the cable to be tested can be influenced, the structures of the fixed seat and the movable seat are optimized and improved, and the following feasible selection is given: the clamping surfaces of the fixing seat and/or the clamping wire grooves of the movable seat are convex, and when the movable seat is close to the fixing seat and the clamping wire grooves are close to each other so as to clamp the cable to be tested, the two clamping surfaces of the movable seat and the fixing seat keep a gap. When the scheme is adopted, the clamping surfaces of the fixed seat and the movable seat cannot be contacted and interfered, no matter how small the size of the cable to be tested is, a gap is reserved between the clamping surfaces after the cable to be tested is clamped by the clamping wire slot.

Still further, when the fixed seat and the movable seat are opened and closed relatively to clamp the cable to be tested, a certain damping is provided to protect the cable to be tested, and a scheme for providing damping is not limited only, for example, in some schemes, a torsion spring structure can be arranged at a hinge joint of the fixed seat and the movable seat, and optimization is performed and one of possible choices is given here: an elastic blocking piece is arranged between the fixed seat and the movable seat. In some possible implementations, the elastic blocking member is connected to the fixed seat or the movable seat, and when the elastic blocking member contacts the fixed seat and the movable seat at the same time, the elastic blocking member applies an elastic force to the fixed seat and the movable seat to prevent the fixed seat and the movable seat from continuing to approach. When adopting this scheme, the elasticity is blocked the piece and is intervened only when contact fixing base and movable seat simultaneously, and does not intervene at other moment, so can improve the operation convenience of movable seat.

Further, in the present invention, the structure of the elastic barrier is not limited only, and optimization is performed herein and one possible choice is given: the elastic blocking piece is one of a spring, an elastic telescopic rod, an elastic abutting arm and an elastic abutting block. When the scheme is adopted, the elastic blocking piece can be arranged on the movable seat or the fixed seat and provides enough elastic contact to protect the cable to be tested.

Further, in the present invention, the cable shield can be opened and closed, so as to enable the cable to be tested to be clamped into the magnetic focusing ring under the non-intervention condition, and meanwhile, the shielding effect can be maintained, the structure of the cable shield is not limited solely, and optimization is performed and one of the possible choices is given here: one shielding part of the cable shielding part is connected to the fixed seat or the movable seat and hinged with the other shielding part to turn over and open and close relatively, grooves for the cable to be tested to pass through are formed in the two shielding parts, and when the two shielding parts are closed, the grooves are spliced into a wire hole. When adopting such scheme, the laminating face of two shielding portions can adopt corresponding complex slot structure, reduces the magnetic leakage through the laminating face of buckling, also improves the shielding effect to external electromagnetic field.

Further, in the present invention, in order to maintain stability and reliability in shielding, the structure of the cable shield is optimized, and one of possible choices is given here: the two shielding parts are correspondingly provided with buckling structures, and are locked through the buckling structures when the two shielding parts are closed. When the scheme is adopted, the buckling structure can adopt structures such as a hasp and a lock catch.

Further, for better operation of the fixed and movable bases, optimization improvements are presented herein and one possible option is: the fixed seat and the movable seat are respectively connected with a handle structure for operating the opening and closing. When the scheme is adopted, the handle structure can be integrally formed with the fixed seat and the movable seat, and can also adopt a split type structure.

Still further, the handle structure itself may be used in a solution that is not limited solely, and is optimized and one possible choice is given here: the handle structure comprises a handle arm, and a handle hole is formed in the handle arm.

Further, the opening and closing structure of the fixed seat and the movable seat is not limited only, and one possible option is optimized and illustrated here: the fixed seat and the movable seat are correspondingly provided with hinge arms, and the two hinge arms are mutually matched and hinged to enable the fixed seat and the movable seat to be opened and closed relatively. When the scheme is adopted, the articulated arm, the fixed seat and the movable seat are integrally formed.

Compared with the prior art, the technical scheme disclosed by the invention has the following partial beneficial effects:

according to the leakage current detection device provided by the invention, under the condition that the working of an original circuit is not affected, the cable shielding piece is opened through the opening of the fixed seat and the movable seat, the sensing component is turned over to leave the air gap, a cable to be detected can be clamped into the magnetic focusing ring, the base component, the cable shielding piece and the circuit shielding piece can enter leakage current detection after being reset, and the external electromagnetic field is shielded through the cable shielding piece and the circuit shielding piece, so that the detection environment at the cable to be detected is kept free from external interference, and a more accurate leakage current result is obtained through detection.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic view of the overall structure of the detecting device, in which the base assembly is opened, the cable shield and the circuit shield are turned up, and in which the movable base is closed with the fixed base.

Fig. 2 is a schematic view of the entire structure of the detecting device, in which the base assembly is opened, the cable shield and the circuit shield are turned up, and in which the movable base is separated from the fixed base.

Fig. 3 is a schematic structural diagram of the detection device when in operation.

Fig. 4 is a schematic diagram of simulation of collecting magnetic fields generated by leakage currents of cables to be tested by the magnetic focusing ring.

Fig. 5 is a schematic structural diagram of the magnetic flux collecting ring.

Fig. 6 is a schematic diagram showing the influence of the track current on the induced magnetic field intensity of the TMR chip.

Fig. 7 is a schematic view of the shielding of the cable shield against the magnetic flux collecting ring.

Fig. 8 is a schematic diagram of the shielding at the circuit shield versus the controller.

Fig. 9 is a schematic diagram of a magnetic field simulation result of a shielding structure composed of a cable shield and a circuit shield.

Fig. 10 is a schematic diagram of a Lora communication transmission.

In the above figures, the meaning of each symbol is:

1. a fixing seat; 2. a movable seat; 3. a cable shield; 4. a circuit shield; 5. a handle; 6. a handle hole; 7. a magnetic ring; 8. a sensing assembly; 9. an articulated arm; 10. an elastic barrier; 11. clamping wire grooves; 12. and a clamping surface.

Detailed Description

The invention is further illustrated by the following description of specific embodiments in conjunction with the accompanying drawings.

Aiming at the existing leakage current detection, especially the detection of weak leakage current, the external electromagnetic field interference exists, and the detection precision is influenced, so that the situation that the leakage current has errors is judged; and the current leakage current detection device cannot realize non-intervention detection, and can realize detection only after the original circuit is removed and then the original circuit is connected, so that the operation is complicated. The following examples are optimized to overcome the deficiencies of the prior art.

Examples

As shown in fig. 1, 2 and 3, the embodiment provides a novel adjustable open-close type leakage current detection device for power equipment, which aims to collect and detect a magnetic field generated by a cable to be detected through a magnetic focusing ring 7, isolate the electromagnetic field around the cable to be detected through a cable shielding piece 3 and a circuit shielding piece 4, and further improve the accuracy of leakage current detection.

As the detection device provided in the present embodiment, one of its structures includes:

the base assembly comprises a fixed seat 1 and a movable seat 2 which are relatively opened and closed, and the opening and closing surfaces of the fixed seat 1 and the movable seat 2 form a clamping structure for clamping a cable to be tested.

In this embodiment, the clamping structure may be a solution, which is not limited only, but may be a plurality of possible solutions, and this embodiment is optimized and adopts one of the possible options: the clamping structure comprises clamping wire grooves 11 which are respectively arranged on the fixed seat 1 and the movable seat 2. When the scheme is adopted, the clamping wire grooves 11 can clamp cables to be tested with different sizes, so that the cables to be tested are kept at the centered detection positions, the magnetic field generated by the leakage current of the cables to be tested can be more accurate after the magnetic gathering ring 7 is used for collecting the magnetic field, and the detection precision can be further improved.

In this embodiment, considering that when clamping different cables, the distance between the clamping surfaces 12 of the fixed seat 1 and the movable seat 2 may change, if the diameter of the cable to be tested is too small, the clamping surfaces 12 may contact, which may affect the stable clamping of the cable to be tested, so that the structures of the fixed seat 1 and the movable seat 2 are optimized and improved, and the following feasible selection is adopted: the clamping surfaces 12 of the clamping wire grooves 11 of the fixed seat 1 and/or the movable seat 2 are convex, and when the movable seat 2 is close to the fixed seat 1 and the clamping wire grooves 11 are close to each other to clamp the cable to be tested, the two clamping surfaces 12 of the movable seat 2 and the fixed seat 1 keep a gap. When the scheme is adopted, the clamping surfaces 12 of the fixed seat 1 and the movable seat cannot be contacted and interfered, and no matter how small the size of the cable to be tested is, a gap is reserved between the clamping surfaces 12 after the cable to be tested is clamped by the clamping wire slot 11.

Preferably, in this embodiment, the fixed seat 1 and the movable seat 2 are made of epoxy resin materials.

When fixing base 1 and movable seat 2 open and shut relatively in order to hold and wait to survey the cable, provide certain damping in order to protect and wait to survey the cable, provide the scheme of damping and not only limited, for example in some schemes, can set up torsional spring structure in the articulated department of fixing base 1 and movable seat, this embodiment optimizes and adopts one of them feasible selection: an elastic blocking piece 10 is arranged between the fixed seat 1 and the movable seat 2, the elastic blocking piece 10 is connected to the fixed seat 1 or the movable seat 2, and when the elastic blocking piece 10 contacts the fixed seat 1 and the movable seat 2 at the same time, the elastic blocking piece 10 applies elastic force to the fixed seat 1 and the movable seat 2 to prevent the fixed seat 1 and the movable seat 2 from continuing to be close. When adopting such scheme, the elastic blocking piece 10 intervenes only when contacting fixing base 1 and movable seat 2 simultaneously, and does not intervene at other moments, so can improve movable seat 2's operation convenience.

Preferably, in this embodiment, the clamping surface 12 of the fixing seat is an inner concave surface, the clamping surface 12 of the movable seat is an outer convex surface, and the concave angle formed by the inner concave surface is larger than the convex angle formed by the outer convex surface, so that the clamping effect of the fixing seat and the movable seat is better.

Preferably, when the elastic blocking member 10 is provided, a mounting hole may be provided on the movable seat 2 or the fixed seat 1, and the elastic blocking member 10 is semi-hidden in the mounting hole.

In the present embodiment, the structure of the elastic barrier 10 is not limited only, but the present embodiment is optimized and adopts one of the possible choices: the elastic blocking member 10 includes a spring, an elastic telescopic rod, an elastic abutment arm or an elastic abutment block. With such a solution, the elastic blocking member 10 can be provided on the movable seat 2 or the fixed seat 1 and provide a sufficient elastic contact to protect the cable to be tested.

Preferably, for better operation of the fixed seat 1 and the movable seat 2, this embodiment is optimally modified and adopts one of the possible options: the fixed seat 1 and the movable seat 2 are respectively connected with a handle structure for operating opening and closing. When the scheme is adopted, the handle structure can be integrally formed with the fixed seat 1 and the movable seat 2, and can also adopt a split type structure.

Preferably, the handle structure itself is not limited solely, and one possible option is here to optimize and set out: the handle structure comprises a handle arm 5, and a handle hole 6 is formed in the handle arm 5.

In this embodiment, the opening and closing structures of the fixed seat 1 and the movable seat 2 are not limited solely, and one of the possible options is optimized and adopted in this embodiment: the fixed seat 1 and the movable seat 2 are correspondingly provided with articulated arms 9, and the two articulated arms 9 are mutually matched and articulated to enable the fixed seat 1 and the movable seat 2 to be opened and closed relatively. When the scheme is adopted, the articulated arm 9, the fixed seat 1 and the movable seat 2 are integrally formed.

The second structure of the detection device provided in this embodiment includes:

the magnetic focusing ring 7 is fixedly connected to the fixing seat 1, the magnetic focusing ring 7 is made of magnetic materials, meanwhile, the magnetic focusing ring 7 is aligned to the clamping structure so that a cable to be tested passes through the middle of the magnetic focusing ring 7, and the magnetic focusing ring 7 is further provided with an air gap for clamping the cable to be tested.

Preferably, the magnetic flux collecting ring 7 is made of permalloy in this embodiment, and its relative permeability is about 1000000.

As the detecting device provided in this embodiment, a third structure thereof includes:

the sensing component 8 for detecting the intensity of the magnetic field collected on the magnetic focusing ring 7 is connected with the fixing seat 1, overturns and enters the air gap opening or leaves the air gap opening.

Preferably, in the present embodiment, the sensing assembly 8 comprises a TMR sensor for detecting the magnetic field strength.

As the detecting device provided in the present embodiment, a fourth configuration thereof includes:

and the controller is electrically connected with the sensing assembly 8 and synchronously overturns.

Preferably, the controller in this embodiment may be a PLC or a single chip microcomputer, and in other possible schemes, a controller such as a raspberry pie may also be used.

Preferably, in this embodiment, the controller includes a PCB board, and the PCB board is spaced apart from the sensing component 8, and when the PCB board is electrically connected to the sensor, the wiring cable is not overlapped with the sensing component 8 up and down, so as to avoid interference of the magnetic field generated by the wiring cable on the detection of the sensing component 8.

The fifth configuration of the detection device provided in this embodiment includes:

the cable shielding piece 3 for shielding the external magnetic field of the magnetic focusing ring 7 comprises two shielding parts which are arranged on the fixing seat in a turnover mode and are opened and closed relatively, an air gap opening of the magnetic focusing ring 7 is exposed when the two shielding parts are opened, the magnetic focusing ring 7 and a testing section of a cable to be tested are closed when the two shielding parts are closed, and a non-testing section of the cable to be tested penetrates out of the cable shielding piece 3.

Preferably, in this embodiment, the cable shielding member 3 can be opened and closed, so as to enable the cable to be tested to be clamped into the magnetic focusing ring 7 under the non-intervention condition, and meanwhile, the shielding effect can be maintained, the structure of the cable shielding member 3 is not limited only, and this embodiment is optimized and adopts one of the possible choices: one shielding part of the cable shielding part 3 is connected to the fixed seat 1 or the movable seat 2 and hinged with the other shielding part to turn over and open relatively, grooves for the cable to be tested to pass through are formed in the two shielding parts, and when the two shielding parts are closed, the grooves are spliced into a wire hole. When adopting such scheme, the laminating face of two shielding portions can adopt corresponding complex slot structure, reduces the magnetic leakage through the laminating face of buckling, also improves the shielding effect to external electromagnetic field.

In this embodiment, in order to maintain a stable and reliable shielding, the structure of the cable shield 3 is optimized, one of the possible options being adopted here: the two shielding parts are correspondingly provided with buckling structures, and are locked through the buckling structures when the two shielding parts are closed. When the scheme is adopted, the buckling structure can adopt structures such as a hasp and a lock catch.

Preferably, in the present embodiment, the cable shield 3 is made of an aluminum material.

As the detection component provided in this embodiment, a sixth configuration thereof includes:

the circuit shielding piece 4 is used for isolating and shielding an electromagnetic field generated by the controller, covers the controller and turns over relative to the fixed seat 1, when the circuit shielding piece 4 turns over upwards, the controller and the sensing component 8 are driven to turn over and expose an air gap opening of the magnetic focusing ring 7, and when the circuit shielding piece 4 turns over downwards to be attached to the base component, the sensing component 8 is placed in the air gap opening.

Preferably, the circuit shielding member 4 in this embodiment adopts a double-layer shielding structure, the inner layer shielding is made of permalloy with high magnetic permeability, and the outer layer is made of aluminum.

The above-disclosed scheme explains the structural composition of the detection device provided in this embodiment, and the working principle thereof will be explained.

1. From the law of biot-savart, the magnetic field generated by the current-carrying wire at a certain point P in space is:

wherein r is the distance between the P point and the current-carrying wire, mu ₀ The magnetic permeability in vacuum is shown as I, the current passing through the lead is shown as B, and the magnetic induction intensity is shown as B.

The current passing through the inside of the current-carrying long straight wire AB is I, and the distance between a certain point P in space and the wire AB is r0, so that the magnetic field generated by the wire AB at the point P can be obtained as follows:

wherein θ ₁ An included angle theta formed by the connecting line of the point P and the point A and the lead ₂ The included angle formed by the connecting line of the point P and the point B and the lead.

When the length of the wire AB is fixed and the positions of the wire and the point P remain relatively fixed, the magnitude B of the magnetic field generated by the wire AB at the point P is proportional to the current value inside the wire.

The TMR chip outputs voltage in a certain magnetic field intensity range in a linear relation with the magnitude of the magnetic field in the direction of the sensed magnetic axis. Therefore, the current inversion calculation is carried out by utilizing the output voltage of the TMR chip according to the magnetic field size monitoring generated by the current, so as to achieve the purpose of current measurement.

2. With respect to current sensor

2.1 Supplementary explanation of magnetic ring structure

Because the measured current is weak, the magnetic field induced by the TMR chip is weak, the output voltage is extremely small, and subsequent signals cannot be processed and calculated, so that current inversion is realized. In the embodiment, a gap-formed magnetism gathering ring structure is adopted, a TMR chip is placed in an air gap port, and the intensity of a magnetic field sensed by the TMR chip is amplified, as shown in fig. 4. The magnetic gathering ring mainly plays a role of gathering a magnetic field generated by the lead, so that the magnetic gathering ring is made of soft magnetic materials.

According to the ampere loop theorem:

where H is the magnetic field strength, l is the length of the magnetic field passing path, and I is the current in the wire.

Substituting the parameters in fig. 3 can result in:

wherein H is _C Represents the magnetic field strength in the magnetic focusing ring, H _A Represents the magnetic field strength in the air gap, r ₀ Representing the average radius of the poly ring,

D ₁ is the inner diameter of the magnetic ring, D ₂ The outer diameter of the magnetic flux collecting ring is d, and the air gap of the magnetic flux collecting ring is d.

Let b=μ ₀ H _A ＝μH _C In substitution, it is possible to obtain:

mu is the relative permeability of permalloy.

Thus:

and B is the magnetic induction intensity in the air gap after the magnetic flux collecting ring is added.

Since the permeability mu of permalloy is far greater than that of air ₀ Therefore, the method can be simplified into:

when the magnetic flux collecting ring is not used, the magnetic induction B at the center of the air gap ₀ The method comprises the following steps:

the ratio of the magnetic induction intensity at the center of the air gap before and after the magnetic flux gathering ring is used is as follows:

based on the deduction, the gap size is designed according to the actual size of the TMR chip, and the overall size of the magnetic flux collecting ring is comprehensively determined according to the field weak current lead radius and the gap size.

2.2 Sensor supplement description

The main circuit of the sensor consists of a sensing chip, a power supply module, an instrument amplifier module, a zeroing and outputting module and a hardware filtering module. The sensing chip adopts TMR chip with low noise and high sensitivity. The power module provides working power for the TMR chip, the instrument chip, the operational amplifier chip and the filter chip. The main circuit amplifying module adopts a two-stage amplifying mode, the front stage adopts an instrument amplifier, the rear stage adopts an operational amplifier, and a subtracting circuit is added to realize the zeroing function of the main circuit. The hardware filtering adopts a fourth-order Baotewok filter to carry out low-pass filtering circuit design. Because the influence of noise on measurement accuracy is larger when weak current monitoring is oriented, the low-noise selection principle is held when each chip is selected.

In the design of the circuit board, the bypass capacitor and the decoupling capacitor are properly added at all power interfaces, and the capacitor is as close to the chip pins as possible so as to filter high-frequency electromagnetic interference signals on a power supply. The circuit wiring follows the minimum rule of the loop, namely the area surrounded by the signal line and the ground wire loop is reduced as much as possible during wiring, so that the interference of an external electromagnetic field to the circuit board can be reduced, and the electromagnetic radiation of the circuit board to the outside can be reduced. The isolation design is carried out between different electric networks, so that crosstalk is reduced; a certain distance is kept between the sensitive element and the device which is easy to generate interference; when parallel wiring is carried out, the distance between the signal lines is larger than the line width, chamfering is applied, and signal reflection and electromagnetic emission are avoided; the traces of adjacent layers are orthogonal.

Meanwhile, when the measured current is smaller than a certain value, the PCB wiring current near the TMR chip can cause interference to the magnetic field intensity sensed by the TMR. As shown in FIG. 5, the structure of the sensor is simplified, current lines in a shell around the TMR sensor in the PCB are drawn randomly, common ground is realized, and the TMR sensor is placed in a magnetic focusing ring gap. And keeping the current in the PCB shell unchanged (10 mA), changing the current value in the lead, and carrying out simulation solution. Since the TMR chip used for manufacturing the sensor is in the X-axis sensitivity direction, a magnification ratio comparison chart of the X-axis magnetic field direction before and after the sensor is placed is drawn, as shown in FIG. 6. As can be seen from the comparison chart, when the current passing through the lead is smaller than the current (10 mA) in the shell, the amplification factor is increased in a nonlinear manner, and when the current is larger, the influence of the current in the shell on the magnetic field measured by the sensor is qualitative, so that the influence of the PCB wiring on the weak current measurement accuracy is larger. Therefore, the PCB wiring around the TMR chip is planned, the PCB wiring does not pass through the lower part of the TMR chip, the wiring is more parallel to the X-axis direction, and the wiring vertical to the X-axis direction is furthest away from the TMR chip.

2.3 Description of the circuit shield

As shown in fig. 7, 8 and 9, stable electromagnetic interference shielding is realized for the TMR sensor chip and the main circuit. The inner shielding layer uses permalloy with high magnetic conductivity, and the outer shielding layer uses aluminum material. Electromagnetic interference waves pass through the aluminum shielding, so that electric field interference can be effectively restrained, partial magnetic field interference can be filtered, and further residual magnetic field interference can be well restrained through the permalloy shielding layer, so that electromagnetic interference shielding is realized.

The effectiveness of the shielding is expressed by shielding effectiveness SE as shown in the formula:

wherein H is ₀ Represents the magnetic field strength without shielding layer, H _s Indicating the magnetic field strength when the shielding layer is present; e (E) ₀ Represents the electric field strength without shielding layer E _s The electric field strength when the shielding layer is present is shown.

Under the condition that two wire interference sources exist outside, the magnetic field SE of the shielding structure designed by the patent can reach 33.1dB, the electric field SE can reach 77dB, and the simulation result is shown in figure 9.

The double-layer shielding design is carried out on the shielding structure of the sensor main circuit board, so that the electric field can be restrained while the magnetic field is shielded, and the external electromagnetic interference is reduced.

2.4 Lora communication transmission and cloud processing

As shown in fig. 10, the leakage current detection communication transmission process includes a power supply unit, a core processing unit, a Lora wireless transmission module, and a leakage current detection unit. The power supply unit takes electricity from the incoming line end, rectifies and filters the alternating current, then carries out AC/DC conversion, and changes the alternating current into stable low-voltage direct current which is supplied to the core processing unit, the leakage current detection unit and the Lora wireless transmission module. The leakage current detection unit converts the detected leakage current into a signal which can be identified by the core processing unit, then the signal is acquired, the current leakage current value is calculated, the core processing unit transmits the leakage current value to the Lora wireless transmission module in real time, the Lora wireless transmission module transmits leakage current data information to a base station in a certain range by adopting a customized protocol, the base station uploads the leakage current data information to the cloud server through a 4G network, the cloud server opens an interface, and the data and the state of each node switch can be checked through accessing through a mobile phone App and a PC, so that the purpose of real-time monitoring is realized.

The wireless communication mode based on the Lora technology has the advantages of long transmission distance, low working energy consumption, strong multi-interference immunity of mountable nodes and low cost, and can transmit measured leakage current data to an upper computer in real time, thereby being beneficial to users to grasp the leakage current change in time.

The above is an embodiment exemplified in this example, but this example is not limited to the above-described alternative embodiments, and a person skilled in the art may obtain various other embodiments by any combination of the above-described embodiments, and any person may obtain various other embodiments in the light of this example. The above detailed description should not be construed as limiting the scope of the present embodiments, which is defined in the appended claims.

Claims

1. Novel adjustable open-close type power equipment leakage current detects device, its characterized in that includes:

the base assembly comprises a fixed seat (1) and a movable seat (2) which are relatively opened and closed, and the opening and closing surfaces of the fixed seat (1) and the movable seat (2) form a clamping structure for clamping a cable to be tested;

the magnetic focusing ring (7) is connected with the fixing seat (1), the magnetic focusing ring (7) is made of magnetic materials, meanwhile, the magnetic focusing ring (7) is aligned to the clamping structure so that a cable to be tested passes through the middle part of the magnetic focusing ring (7), and the magnetic focusing ring (7) is also provided with an air gap for clamping the cable to be tested;

the sensing component (8) is connected with the fixing seat (1) and overturns, and the sensing component (8) overturns into the air gap opening or overturns out of the air gap opening; the sensing component (8) is used for detecting magnetic field signals generated by interaction of the cable to be tested and the magnetic focusing ring (7) when the cable to be tested passes through the middle of the magnetic focusing ring (7);

the controller is electrically connected with the sensing assembly (8) and is used for receiving and processing magnetic field signals detected by the sensing assembly (8);

the cable shielding piece (3) comprises two shielding parts which are movably arranged on the fixed seat and are movably matched with each other, an air gap opening of the magnetic focusing ring (7) is exposed when the two shielding parts are opened, the magnetic focusing ring (7) and a test section of a cable to be tested are closed when the two shielding parts are closed, and a non-test section of the cable to be tested penetrates out of the cable shielding piece (3);

the circuit shielding piece (4) covers the controller and moves relative to the fixed seat (1), the circuit shielding piece (4) drives the controller and the sensing assembly (8) to move and expose an air gap opening of the magnetic gathering ring (7) when moving upwards, and the sensing assembly (8) is placed into the air gap opening when the circuit shielding piece (4) moves downwards to be attached to the base assembly.

2. The novel adjustable open-close type power equipment leakage current detection device according to claim 1, wherein: the clamping structure comprises clamping wire grooves (11) which are respectively arranged on the fixed seat (1) and the movable seat (2).

3. The novel adjustable open-close type power equipment leakage current detection device according to claim 1 or 2, wherein: the clamping surfaces (12) where the clamping wire grooves (11) of the fixed seat (1) and/or the movable seat (2) are arranged are outwards convex, and when the movable seat (2) is close to the fixed seat (1) and the clamping wire grooves (11) are close to each other, the cable to be tested is clamped.

4. The novel adjustable open-close type power equipment leakage current detection device according to claim 1, wherein: an elastic blocking piece (10) is arranged between the fixed seat (1) and the movable seat (2).

5. The novel adjustable open-close type power equipment leakage current detection device according to claim 4, wherein: the elastic blocking piece (10) is one of a spring, an elastic telescopic rod, an elastic abutting arm and an elastic abutting block.

6. The novel adjustable open-close type power equipment leakage current detection device according to claim 1, wherein: one shielding part of the cable shielding part (3) is connected to the fixed seat (1) or the movable seat (2) and hinged with the other shielding part to be turned over and opened and closed relatively, grooves for the cable to be tested to pass through are formed in the two shielding parts, and when the two shielding parts are closed, the grooves are spliced into a wire hole.

7. The novel adjustable open-close type power equipment leakage current detection device according to claim 6, wherein: the two shielding parts are correspondingly provided with buckling structures, and are locked through the buckling structures when the two shielding parts are closed.

8. The novel adjustable open-close type power equipment leakage current detection device according to any one of claims 1, 2 and 4 to 7, wherein: the fixed seat (1) and the movable seat (2) are respectively connected with a handle structure for operating the opening and closing.

9. The novel adjustable open-close type power equipment leakage current detection device according to claim 8, wherein: the handle structure comprises a handle arm (5), and a handle hole (6) is formed in the handle arm (5).

10. The novel adjustable open-close type power equipment leakage current detection device according to claim 1, wherein: the fixed seat (1) and the movable seat (2) are correspondingly provided with hinge arms (9), and the two hinge arms (9) are mutually matched and hinged and enable the fixed seat (1) and the movable seat (2) to be opened and closed relatively.