Current detection system for three-phase collectively-packaged cable

Abstract

The utility model relates to a current detection system used for a three-phase collectively-wrapped cable. The current detection system comprises a master control module, a signal conditioner, three magnetic tunnel current sensors and a power supply module. The three magnetic tunnel current sensors are arranged on the outer surface of the three-phase collectively-wrapped cable, so that the three magnetic tunnel current sensors and the three cable cores are in one-to-one correspondence, and the current signal of each cable core can be accurately measured based on the tunnel magnetic resistance technology. Therefore, current parameters are provided for cable operation state and harmonic analysis, and guarantee is provided for stable operation of the cable, a power grid and electric equipment. Meanwhile, through the arrangement of the signal conditioner, current signals transmitted by the three magnetic tunnel current sensors can be received, stable current can be provided for the three magnetic tunnel current sensors, and continuous and stable operation of the magnetic tunnel current sensors is guaranteed.

Description

Technical Field

[0001] This utility model relates to the field of cable testing technology, specifically to a current detection system for three-phase bundled cables. Background Technology

[0002] The statements herein provide only background information related to this invention and do not necessarily constitute prior art.

[0003] Three-phase bundled cable refers to a multi-functional cable containing three independent cable cores separated by an insulation layer. Its structural feature is that the three cable cores are symmetrically distributed in a triangle within a metal sheath, generating symmetrical three-phase currents during operation. Based on its structural characteristics and excellent performance, the three-phase bundled cable is widely used in urban power supply, wind power plants, solar power plants, and industrial and mining enterprises. However, with the increasing complexity of power grid structures, rising equipment density, and the increasing proportion of aging cables, power distribution cable line faults are becoming more frequent, posing a serious threat to the cable lines and power users.

[0004] Currently, cable current detection is divided into two methods: offline detection and online detection. Offline detection, under conditions of power grid equipment channel limitations and strict control over planned power outage maintenance time, suffers from problems such as inability to comprehensively assess cable performance and shortened cable lifespan, and is therefore gradually being replaced by online monitoring. For online detection, existing current transformer (CT) loops and Rogowski coils are not suitable for current detection of three-phase bundled cables. This is because each phase current generated within a three-phase bundled cable produces an induced magnetic field, and the phase difference between the three phase currents causes the induced magnetic fields to cancel each other out, resulting in a measured current value of zero. Therefore, it is impossible to determine the operating status of the three-phase bundled cable, posing a certain threat to the stable operation of the power grid and electrical equipment. Utility Model Content

[0005] The technical problem to be solved by this utility model is to provide a current detection system for three-phase bundled cables. By using three magnetic tunnel current sensors and based on tunnel magnetoresistive technology, the current of the three cores in the three-phase bundled cable can be accurately obtained, and current parameters are provided for cable operation status and harmonic analysis. At the same time, a signal conditioner is used to deliver a stable current to the three magnetic tunnel current sensors, so that the three magnetic tunnel current sensors can operate stably, thereby ensuring the stable operation of the cable, power grid and electrical equipment.

[0006] The purpose of this invention is to provide a current detection system for a three-phase bundled cable. The three-phase bundled cable contains three cable cores arranged around the center of the cable, and the distance between any two adjacent cable cores is equal. The current detection system includes a main control module, a signal conditioner, three magnetic tunnel current sensors, and a power supply module. The signal conditioner is connected to the main control module and the three magnetic tunnel current sensors, and the power supply module is connected to the main control module and the signal conditioner.

[0007] The three magnetic tunnel current sensors are all fixed on the outer surface of the cable, and there is a one-to-one correspondence between the three magnetic tunnel current sensors and the three cable cores. At the same time, the center of the corresponding magnetic tunnel current sensor and the cable core is on the same straight line as the center of the cable.

[0008] The magnetic tunnel current sensor includes a tunnel magnetoresistive sensing chip, an input stage circuit, a signal channel, a modulation circuit, and an output stage circuit connected in sequence.

[0009] As a further technical solution, the tunnel magnetoresistive sensing chip in the magnetic tunnel current sensor is used to collect the current signal of the cable core.

[0010] As a further technical solution, the output stage circuit is connected to a signal conditioner.

[0011] As a further technical solution, the signal channel includes a low-frequency signal channel and a high-frequency signal channel that run in parallel.

[0012] As a further technical solution, the low-frequency signal channel includes a low-pass filter and a linear amplifier circuit connected in sequence.

[0013] As a further technical solution, the low-pass filter is connected to the input stage circuit, and the linear amplifier circuit is connected to the modulation circuit.

[0014] As a further technical solution, the high-frequency signal channel includes a bandpass filter and a logarithmic amplifier circuit connected in sequence.

[0015] As a further technical solution, the bandpass filter is connected to the input stage circuit, and the logarithmic amplifier circuit is connected to the modulation circuit.

[0016] As a further technical solution, the current detection system also includes a storage module, which is connected to the main control module.

[0017] As a further technical solution, the current detection system also includes a communication module, which is connected to the main control module.

[0018] The beneficial effects of one or more of the above technical solutions:

[0019] (1) This utility model sets three magnetic tunnel current sensors on the outer surface of a three-phase integrated cable, so that the three magnetic tunnel current sensors and the three cable cores form a one-to-one correspondence. Based on tunnel magnetoresistive technology, it can accurately measure the current signal of each cable core, thereby providing current parameters for cable operation status and harmonic analysis, and ensuring the stable operation of cables, power grids and electrical equipment.

[0020] (2) The present invention, through the signal conditioner, can not only receive the current signal transmitted by the three magnetic tunnel current sensors, but also provide a stable current for the three magnetic tunnel current sensors, thus ensuring the continuous and stable operation of the magnetic tunnel current sensors. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. For ease of understanding, the proportions between the various structural parts have been adjusted. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute a limitation of this application.

[0022] Figure 1 This is an overall structural diagram of a current detection system for a three-phase bundled cable according to the present invention.

[0023] Figure 2 This is a structural diagram of the magnetic tunnel current sensor in this utility model.

[0024] Figure 3 This is a circuit diagram of the tunnel magnetoresistive sensing chip in the magnetic tunnel current sensor of this utility model.

[0025] Figure 4 This is a schematic diagram showing the positions of the three magnetic tunnel current sensors installed on a three-phase bundled cable in this utility model.

[0026] The components include: 1. Main control module; 2. Signal conditioner; 3. Magnetic tunnel current sensor; 3-1. Magnetic tunnel current sensor a; 3-2. Magnetic tunnel current sensor b; 3-3. Magnetic tunnel current sensor c; 4. Power supply module; 5. Storage module; 6. Communication module; 7. Temperature detection module; 8. Three-phase bundled cable; 9. Cable core; 9-1. Cable core A; 9-2. Cable core B; 9-3. Cable core C; 10. Terminal; 11. Computing center. Detailed Implementation

[0027] The following is in conjunction with the appendix Figure 1-4 The technical solutions in the embodiments of this utility model will be clearly and completely described.

[0028] Example 1

[0029] Reference Figure 1A current detection system for three-phase bundled cables; (Refer to...) Figure 4 This embodiment describes a three-phase bundled cable 8, which includes three cable cores 9 arranged around the center of the cable. For clarity and understanding, cable cores A9-1, B9-2, and C9-3 are used to represent the three cable cores 9 in the three-phase bundled cable 8. Furthermore, the distance between any two adjacent cable cores 9 is the same, meaning the centers of the three cable cores 9 coincide with the three vertices of an equilateral triangle.

[0030] Reference Figure 1 The current detection system includes a main control module 1, a signal conditioner 2, three magnetic tunnel current sensors 3, and a power supply module 4. The signal conditioner 2 is connected not only to the main control module 1 but also to the three magnetic tunnel current sensors 3; while the power supply module 4 is connected to both the signal conditioner 2 and the main control module 1, thereby supplying power to both the signal conditioner 2 and the main control module 1.

[0031] Reference Figure 4 The three magnetic tunnel current sensors 3 are all fixed on the outer surface of the three-phase bundled cable 8, and the three magnetic tunnel current sensors 3 correspond one-to-one with the three cable cores 9 inside the three-phase bundled cable 8. At the same time, the center of the corresponding magnetic tunnel current sensor 3 and the cable core 9 is on the same straight line as the center of the three-phase bundled cable 8.

[0032] In this embodiment, the magnetic tunnel current sensor a3-1 and the cable core A9-1 are corresponding, and the center of the magnetic tunnel current sensor a3-1, the center of the cable core A9-1 and the center of the three-phase bundled cable 8 are located on the same straight line; at the same time, the magnetic tunnel current sensor b3-2 and the cable core B9-2 are corresponding, and the magnetic tunnel current sensor c3-3 and the cable core C9-3 are corresponding.

[0033] Based on the above settings, a detailed description will be given using the magnetic tunnel current sensor a3-1 and cable core A9-1 as examples:

[0034] Reference Figure 4 ,by Figure 4 The left and right directions are horizontal, and the up and down directions are vertical;

[0035] When the magnetic tunnel current sensor a3-1 is working, the magnetic fields generated by the currents inside the cable cores A9-1, B9-2, and C9-3 will all be detected by the magnetic tunnel current sensor a3-1; while the magnetic fields generated by the cable cores B9-2 and C9-3 will be vector-added at the location of the magnetic tunnel current sensor a3-1, thereby canceling the transverse magnetic field and retaining only the longitudinal magnetic field.

[0036] Then, according to the formula for the magnetic field strength formed by an electric current... (Where B is the magnetic field strength, u is the permeability, l is the current inside the cable, and r is the distance). The magnitude of the magnetic field generated by cable cores B9-2 and C9-3 is inversely proportional to the distance, therefore, the magnetic field has little impact on the magnetic tunnel current sensor a3-1. Furthermore, the magnetic fields generated by cable cores B9-2 and C9-3 cancel each other out. Compared to the magnetic field generated by the current in cable core A9-1, the impact of the magnetic fields generated by cable cores B9-2 and C9-3 on the magnetic tunnel current sensor a3-1 is negligible. Thus, the current data in cable core A9-1 can be detected by the magnetic tunnel current sensor a3-1. Even if the magnetic fields generated by cable cores B9-2 and C9-3 do have some impact on the detection of the magnetic tunnel current sensor a3-1, the current detection value will not be zero.

[0037] In this way, the current in each cable core 9 can be detected.

[0038] And reference Figure 2-3 The magnetic tunnel current sensor 3 includes a tunnel magnetoresistive sensing chip, an input stage circuit, a signal channel, a modulation circuit, and an output stage circuit connected in sequence.

[0039] The tunnel magnetoresistive sensing chip is used to acquire the current signal of the cable core 9; and the working principle of the tunnel magnetoresistive sensing chip is based on the tunnel effect. When current flows through the cable, a magnetic field that changes with the magnitude and direction of the current is generated around the cable 9; when the magnetic field acts on the tunnel magnetoresistive sensing chip, it causes a change in the equivalent bridge resistance inside the chip, thereby outputting a voltage signal.

[0040] When the tunnel magnetoresistive sensing chip outputs a voltage signal, the voltage signal enters the input stage circuit; the input stage circuit performs impedance matching with the tunnel magnetoresistive sensing chip and increases the signal driving capability to drive the subsequent circuits.

[0041] After processing by the input stage circuit, the original signal is divided into two channels: a low-frequency signal channel (0–200Hz) and a high-frequency signal channel (200kHz–1MHz). The low-frequency signal mainly reflects the power frequency operating current of the cable, while the high-frequency signal mainly reflects the high-frequency pulse current generated by abnormal events.

[0042] The low-frequency signal channel consists of a low-pass filter and a linear amplifier circuit. The input of the low-pass filter is connected to the input stage, and the output is connected to the linear amplifier circuit, with a bandwidth of 0–200Hz. The linear amplifier adjusts the filtered signal to a suitable voltage range through linear amplification.

[0043] The high-frequency signal channel consists of a bandpass filter and a logarithmic amplifier circuit. The input of the bandpass filter is connected to the input stage, and the output is connected to the logarithmic amplifier circuit, with a bandwidth of 200kHz to 1MHz. Because the dynamic range of the current signal generated by the high-frequency pulse signal is too large, a logarithmic amplifier circuit is used to compress and adjust the high-frequency signal.

[0044] The input of the modulation circuit is connected to both a linear amplifier circuit and a logarithmic amplifier circuit, while the output is connected to the output stage circuit. The function of the modulation circuit is to combine and modulate a low-frequency signal containing power frequency current information and a high-frequency signal containing pulse current information into a single mixed signal.

[0045] The input terminal of the output stage circuit is connected to the modulation circuit, which amplifies the mixed signal and provides the output driving capability.

[0046] And reference Figure 3 This is a circuit diagram of a magnetic tunnel current sensor 3; where U1 is the tunnel magnetoresistive sensing chip. U2, R1, R2, R3, and R4 constitute the input stage circuit. U3, R5, R6, R7, R8, C1, and C2 constitute a low-pass filter. U4, R9, R10, R11, and C3 constitute a linear amplifier circuit. The bandpass filter consists of a low-pass filter and a high-pass filter, where U5, R12, R13, R14, R15, C4, and C5 constitute the low-pass filter, and U6, R16, R17, R18, R19, C6, and C7 constitute the high-pass filter. U7, R20, C8, and C9 constitute a logarithmic amplifier. U8, R21, R22, R23, R24, C10, and C11 constitute a proportional operational amplifier, which also functions as a modulation circuit and output stage. J1 is the signal output connector.

[0047] Among them, U2, U3, U4, U5, and U6 are common circuit units, i.e., operational amplifiers, and U7 is a logarithmic operational amplifier; C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, and C11 are coupling capacitors; the above can be implemented using common electronic components, and no specific limitation is made in this embodiment.

[0048] Among them, U2, U3, U4, U5, and U6 are common circuit units, i.e., operational amplifiers, and U7 is a logarithmic operational amplifier; C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, and C11 are coupling capacitors; the above can be implemented using common electronic components, and no specific limitation is made in this embodiment.

[0049] After the output stage circuit outputs a signal, the signal is transmitted to the signal conditioner 2. In this embodiment, the signal conditioner 2 is not only used to receive the signal transmitted by the magnetic tunnel current sensor 3 and adjust the signal to a signal that the main control module 1 can receive, and finally transmit the adjusted signal to the main control module 1; it is also used to adjust the current signal supplied by the power supply module 4 into a signal that can be stably received by the magnetic tunnel current sensor 3, avoiding the problem that the magnetic tunnel current sensor 3 cannot operate normally due to signal changes caused by complex environment, magnetic field changes and other factors, thereby ensuring the stable operation of the magnetic tunnel current sensor 3.

[0050] Reference Figure 1 The current detection system also includes a storage module 5 and a communication module 6, both of which are connected to the main control module 1.

[0051] When the main control module 1 receives the current signal detected by the magnetic tunnel current sensor 3 from the signal conditioner 2, it first sends the data to the storage module 5 for storage, facilitating subsequent data retrieval. Simultaneously, the main control module 1 transmits the data to the terminal 10 and the computing center 11 via the communication module 6 and using methods such as Bluetooth and Wi-Fi.

[0052] The terminal 10 can be a smartphone or computer, which can monitor the current of the cable core 9 in the three-phase bundled cable 8 in real time; while the computing center 11 is a device with intelligent analysis algorithms, such as a large computer, which can analyze the operating status of the three-phase bundled cable 8 based on the data obtained from the main control module 1, and perform fault warning and fault location for the three-phase bundled cable 8.

[0053] To improve the accuracy of current detection data and enhance the integrity of the entire current detection system, the current detection system may also include a temperature detection module 7, which is used to detect the temperature data of the three-phase insulated cable 8. By analyzing the temperature data and current data together, the influence of temperature on the current signal can be reduced, thereby ensuring the accuracy of the acquired current signal data.

[0054] Although the specific embodiments of the present utility model have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present utility model. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solution of the present utility model are still within the scope of protection of the present utility model.

Claims

1. A current detection system for a three-phase bundled cable, wherein the three-phase bundled cable contains three cable cores arranged around the center of the cable, and the distance between any two adjacent cable cores is equal; characterized in that, The current detection system includes a main control module, a signal conditioner, three magnetic tunnel current sensors, and a power supply module. The signal conditioner is connected to the main control module and the three magnetic tunnel current sensors, and the power supply module is connected to the main control module and the signal conditioner. The three magnetic tunnel current sensors are all fixed on the outer surface of the cable, and there is a one-to-one correspondence between the three magnetic tunnel current sensors and the three cable cores. At the same time, the center of the corresponding magnetic tunnel current sensor and the cable core is on the same straight line as the center of the cable. The magnetic tunnel current sensor includes a tunnel magnetoresistive sensing chip, an input stage circuit, a signal channel, a modulation circuit, and an output stage circuit connected in sequence.

2. The current detection system for a three-phase bundled cable as described in claim 1, characterized in that, The tunnel magnetoresistive sensing chip in the magnetic tunnel current sensor is used to collect the current signal of the cable core.

3. A current detection system for a three-phase bundled cable as described in claim 1, characterized in that, The output stage circuit is connected to the signal conditioner.

4. A current detection system for a three-phase bundled cable as described in claim 1, characterized in that, The signal channels include low-frequency signal channels and high-frequency signal channels that run in parallel.

5. A current detection system for a three-phase bundled cable as described in claim 4, characterized in that, The low-frequency signal channel includes a low-pass filter and a linear amplifier circuit connected in sequence.

6. A current detection system for a three-phase bundled cable as described in claim 5, characterized in that, The low-pass filter is connected to the input stage circuit, and the linear amplifier circuit is connected to the modulation circuit.

7. A current detection system for a three-phase bundled cable as described in claim 4, characterized in that, The high-frequency signal channel includes a bandpass filter and a logarithmic amplifier circuit connected in sequence.

8. A current detection system for a three-phase bundled cable as described in claim 7, characterized in that, The bandpass filter is connected to the input stage circuit, and the logarithmic amplifier circuit is connected to the modulation circuit.

9. A current detection system for a three-phase bundled cable as described in claim 1, characterized in that, The current detection system also includes a storage module, which is connected to the main control module.

10. A current detection system for a three-phase bundled cable as described in claim 1, characterized in that, The current detection system also includes a communication module, which is connected to the main control module.

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