Time-sharing self-powered cable circulation current monitoring device

Abstract

The invention relates to the technical field of cable circulation current monitoring, in particular to a time-sharing self-powered cable circulation current monitoring device, which comprises a CT (Current Transformer) energy taking module comprising a current transformer and a rectifying circuit; the energy storage module comprises an energy storage capacitor and a charging comparator; the current signal processing module is used for dividing the voltage of the output end of the rectifying circuit and weakening the error amount of the pulsating direct current signal by outputting a first current value and a second current value; a 4G module; and the main controller is used for determining the current measurement value of the cable, adjusting the current monitoring frequency of the current transformer according to the fluctuation value of the current measurement value, and determining whether to adjust the transmission power of the current measurement value transmitted from the 4G module to the background or adjust the amplification gain of the pulsating direct current signal according to the number of abrupt change points in the current change image. According to the invention, the monitoring precision and the monitoring range are increased.

Description

Technical Field

[0001] The invention relates to the technical field of cable circulating current monitoring, and in particular to a time-sharing self-powered cable circulating current monitoring device. Background Art

[0002] In the prior art, when current passes through a cable or wire, a magnetic field is generated around it. This magnetic field changes with the change of current, that is, the magnitude and direction of the current determine the strength and direction of the magnetic field. The current transformer uses its special structure to allow the cable or wire to pass through its opening without direct contact with the transformer. When the cable or wire passes through the opening of the transformer, the magnetic field around it interacts with the internal components of the transformer. The sensing element inside the transformer senses the change in this magnetic field and generates a corresponding induced electromotive force or induced current. This induced current or electromotive force is proportional to the current in the cable or wire, so the current size in the cable or wire can be determined by measuring this induced current or electromotive force; the existing circulating current monitoring solution is installed in a traditional wired manner, as shown in the figure below. The current transformer is connected to the circulating current monitoring device by wire, and a DC24V power supply needs to be provided to the circulating current monitoring device. The data reading interface of the device is a 485 interface. The background management system needs to be connected to the circulating current monitoring device by wired means and use the communication protocol provided by the device to read the current signal. At the same time, an external power supply is required. The wiring is complicated and communication cables need to be laid separately. The wiring workload is large, the communication distance is short, and the current data cannot be read remotely.

[0003] Chinese Patent Publication No.: CN110954778A discloses a cable circulation monitoring device, including: a plurality of slave node systems arranged on site to collect cable grounding circulation status information and convert it into electrical signals, and obtain the cable position of the collected cable grounding circulation status information, and then upload the electrical signals and cable positions to a master node system; a master node system for receiving the electrical signals and cable positions of the cable grounding circulation status information uploaded by the plurality of slave node systems, performing data analysis on the electrical signals of the cable grounding circulation status information uploaded by the plurality of slave node systems to obtain the cable grounding circulation status data, and sending the cable grounding circulation status data and the corresponding cable positions to a remote monitoring service end; a communication network for data transmission between the master node system and the slave node system and between the master node system and the remote monitoring service end; and a remote monitoring service end for receiving the cable grounding circulation status data sent by the master node system to remotely monitor the plurality of slave node systems. It can be seen that the cable circulating current monitoring device has the problems of reduced monitoring accuracy and reduced monitoring range due to the incompatibility between the cable body and circulating current monitoring, and the inability to adapt to the working conditions of poor stability of small circulating currents due to the high power consumption of the monitoring equipment. Summary of the invention

[0004] To this end, the present invention provides a time-sharing self-powered cable circulating current monitoring device to overcome the problems in the prior art of reduced monitoring accuracy and reduced monitoring range due to the incompatibility between the cable body and circulating current monitoring, and the inability to adapt to the working conditions of poor stability of small circulating currents due to the high power consumption of the monitoring equipment.

[0005] To achieve the above object, the present invention provides a time-sharing self-powered cable circulating current monitoring device, comprising:

[0006] A CT energy acquisition module, which is connected to the cable and includes a current transformer for acquiring an AC current signal in the cable and a rectifier circuit connected to the current transformer for converting the AC current signal into a pulsating DC current signal;

[0007] A current signal processing module, connected to the CT energy acquisition module, for dividing the output voltage of the rectifier circuit and reducing the error of the pulsating DC current signal by outputting a first current value and a second current value;

[0008] An energy storage module, which is connected to the CT energy acquisition module, comprises an energy storage capacitor for converting the pulsating DC current signal into voltage energy for storage and a charging comparator connected to the energy storage capacitor for determining the charging state of the energy storage capacitor and the on / off state of the current signal processing module according to the real-time voltage of the energy storage capacitor;

[0009] A main controller is respectively connected to the CT energy acquisition module, the energy storage module and the current signal processing module, and is used to determine the current measurement value of the cable according to the first current value and the second current value, adjust the current monitoring frequency of the current transformer according to the fluctuation value of the current measurement value within a single monitoring cycle, and determine whether to adjust the transmission power of the current measurement value transmitted from the 4G module to the background, or adjust the amplification gain of the pulsating DC current signal according to the number of mutation points in the current change image within the single monitoring cycle.

[0010] The 4G module is connected to the energy storage module and the main controller respectively, and is used to transmit the current measurement value of the cable to the background.

[0011] Furthermore, the energy storage module further includes a relay connected to the rectifier circuit for switching from the energy storage path of the energy storage capacitor to the load path of the current signal processing module under the condition that the energy storage capacitor is fully charged;

[0012] The condition for the energy storage capacitor to be fully charged is that when the voltage of the energy storage capacitor reaches a preset voltage, the charging completion comparator is triggered and sends a charging completion signal to the main controller.

[0013] Furthermore, the current signal processing module includes:

[0014] An electric energy load, which is connected to the rectifier circuit and is used to divide the output voltage of the rectifier circuit;

[0015] A primary signal processing unit connected to the electric energy load to increase input impedance;

[0016] A secondary signal processing unit is connected to the primary signal processing unit and is used for filtering and amplifying the pulsating direct current signal output by the primary signal processing unit to output the first current value and the second current value.

[0017] Wherein, the electric energy load includes:

[0018] A first voltage-dividing circuit, connected to the relay, for outputting a first divided voltage to the primary signal processing unit;

[0019] A second voltage-dividing circuit, connected to the first voltage-dividing circuit, for outputting a second divided voltage to the primary signal processing unit;

[0020] The first voltage-dividing circuit includes a first voltage-dividing resistor, and the second voltage-dividing circuit includes a second voltage-dividing resistor; the resistance value of the first voltage-dividing resistor is greater than the resistance value of the second voltage-dividing resistor.

[0021] Furthermore, the primary signal processing unit includes:

[0022] A first voltage follower connected to the first voltage divider circuit to increase the input impedance of the first voltage divider circuit;

[0023] A second voltage follower connected to the second voltage divider circuit to increase the input impedance of the second voltage divider circuit;

[0024] A first pre-stage voltage divider, connected to the first voltage follower, for dividing the voltage output by the first voltage follower and outputting the voltage to the secondary signal processing unit;

[0025] A second front-stage voltage divider is connected to the second voltage follower and is used for dividing the voltage output by the second voltage follower and outputting the voltage to the secondary signal processing unit.

[0026] Furthermore, the secondary signal processing unit includes:

[0027] a first filtering circuit connected to the first front-stage voltage divider and configured to filter the pulsating DC current signal input by the first front-stage voltage divider;

[0028] a second filtering circuit connected to the second front-stage voltage divider and configured to filter the pulsating DC current signal input by the second front-stage voltage divider;

[0029] a first common-phase amplifier connected to the first filter circuit, configured to amplify the pulsating direct current signal output by the first filter circuit and output the first current value;

[0030] A second in-phase amplifier is connected to the second filtering circuit and is used for amplifying the pulsating direct current signal output by the second filtering circuit and outputting the second current value.

[0031] Further, the current measurement value of the cable includes the first current value and the second current value;

[0032] Among them, the first current value is the product of the ratio of the voltage of the first voltage-dividing circuit to the sum of the first voltage-dividing resistor and the second voltage-dividing resistor and the transformation ratio parameter of the current transformer, and the second current value is the product of the ratio of the voltage of the second voltage-dividing circuit to the second voltage-dividing resistor and the transformation ratio parameter of the current transformer.

[0033] Further, the main controller is connected to the current signal processing module to obtain the first current value and the second current value, and if the second current value is less than or equal to the preset range, the first current value is output as the current measurement value of the cable; if the second current value is greater than the preset range, the second current value is output as the current measurement value of the cable;

[0034] And, when the current measurement value is greater than the current measurement value threshold, it is determined that the current of the cable is too high, and the current high alarm information is reported to the background.

[0035] Furthermore, the main controller is connected to the current signal processing module to obtain the current measurement value in a single monitoring cycle, calculate the fluctuation value of the current measurement value, and increase the current monitoring frequency of the current transformer if the fluctuation value exceeds a preset fluctuation value;

[0036] Wherein, the fluctuation value is the standard deviation of the difference between the current measurement value and the average value of the current measurement value in a single monitoring cycle;

[0037] Wherein, the increase amplitude of the current monitoring frequency is positively correlated with the fluctuation value.

[0038] Further, the main controller is connected to the current signal processing module to obtain the current measurement value of the cable monitored in the single monitoring cycle, and draw a change image of the current measurement value, collect the highest point of the current measurement value in the change image of the current measurement value, and if the current measurement value of the highest point is greater than the current measurement value threshold, then the highest point is determined to be a mutation point;

[0039] If the number of mutation points is greater than the preset number of mutation points, it is determined that the stability of the transmission information does not meet the requirements, and the transmission power of the current measurement value transmitted from the 4G module to the background is increased;

[0040] The increase in the information transmission power is positively correlated with the number of mutation points.

[0041] Further, the main controller is connected to the current signal processing module, and is used to obtain the current measurement values ​​of the adjacent monitoring time points before and after the mutation point with the largest current measurement value to calculate the current change when the current measurement value of the mutation point is greater than the preset mutation current measurement value, and if the current change is greater than the preset current change, reduce the amplification gain of the first common-phase amplifier and the second common-phase amplifier;

[0042] Among them, the current change is the difference between the current measurement value at the mutation point with the largest current measurement value and the minimum value of the current measurement values ​​at adjacent monitoring time points before and after the mutation point with the largest current measurement value; the reduction amplitude of the amplification gain of the first common-phase amplifier and the second common-phase amplifier is proportional to the current change.

[0043] Compared with the prior art, the beneficial effect of the present invention lies in that the device of the present invention is provided with a CT energy acquisition module, an energy storage module, a current signal processing module, a 4G module and a main controller, and the CT energy acquisition module is used to simultaneously complete the information collection and power storage of the measured current on the cable, thereby realizing time-sharing self-power supply and cable circulating current monitoring, and does not require an external power supply such as a battery, and the wiring and installation are simple, thereby realizing the improvement of installation efficiency and the reduction of system failure rate, realizing low-power operation of the system, achieving microampere-level current consumption in standby mode, and improving the endurance of the system under voltage unstable working conditions; by providing a current signal processing module to amplify and filter the current signal, a large range and high-precision current measurement is realized at the same time, signal loss is reduced, and the current monitoring accuracy is improved; the main controller is powered by the energy storage module, and due to the large current fluctuation in the cable circulating current, the CT The energy-harvesting circuit cannot obtain electrical energy stably, and the cable circulating current is small, so the electrical energy obtained by the CT energy-harvesting circuit is very limited. Therefore, this current monitoring device needs to operate in low-power mode. When the system is idle, the 4G module and the operational amplifier power supply are turned off, and the main controller itself enters low-power mode, leaving only the key timer running to wake up the system regularly, further realizing low-power operation; by adjusting the current monitoring frequency, information transmission power and amplification gain of the pulsating DC current signal of the current transformer, the cable magnetic field is unstable due to cable aging, causing the current transformer to overheat, thereby causing the monitoring stability to decrease. By adjusting the information transmission power to increase the monitoring stability, or by adjusting the amplification gain of the pulsating DC current signal, the accuracy of the monitoring results caused by cable aging can be reduced, thereby improving the accuracy and reliability of monitoring.

[0044] Furthermore, the device of the present invention is provided with a current transformer, an energy storage capacitor, a relay and a charging completion comparator, and the CT power supply and current monitoring functions are completed in time-sharing through the current transformer, thereby realizing time-sharing self-powered monitoring, without the need for external power supplies such as batteries, and automatic hardware charging and discharging management; the excess current is consumed through the load path to protect the power input and current transformer of the sensitive energy storage capacitor, thereby extending the service life of the CT energy supply module; by dynamically adjusting the opening and closing of the load path, the load path can be replaced in time after the energy storage capacitor is charged, thereby improving the accuracy and stability of monitoring.

[0045] Furthermore, the device described in the present invention realizes large-range and high-precision current measurement at the same time by setting a first voltage-dividing circuit and a second voltage-dividing circuit, so that the device can adapt to current measurement requirements in different ranges, thereby improving the flexibility and accuracy of monitoring; the larger resistance value of the first voltage-dividing resistor can ensure effective voltage division of the signal under high current conditions, while the smaller resistance value of the second voltage-dividing resistor provides sufficient signal strength under low current conditions, thereby improving the sensitivity of monitoring; in addition, by setting the resistance value of the voltage-dividing resistor, the signal processing process can be further optimized, signal distortion can be reduced, and the accuracy of the monitoring data can be improved.

[0046] Furthermore, the device described in the present invention is used to improve the input impedance of the signal processing circuit and reduce signal loss by setting a first voltage follower, a second voltage follower, a first pre-stage voltage divider and a second pre-stage voltage divider. In order to further improve the current monitoring accuracy, it is necessary to amplify the voltage signal output by the voltage follower. Since the secondary signal processing circuit is powered by a single power supply, reverse amplification cannot be achieved, and only in-phase amplification can be used. However, the in-phase amplification circuit cannot achieve signal reduction, so the signal output by the voltage follower cannot be directly amplified. In order to use a single power supply to achieve signal amplification, a pre-stage voltage divider is used to divide the output voltage of the voltage follower, and then output it to the secondary signal processing, thereby achieving reverse amplification of the signal and improving the accuracy after amplification, thereby improving the monitoring accuracy of the current value.

[0047] Furthermore, the device of the present invention achieves current signal calibration by setting a first filtering circuit, a second filtering circuit, a first common-phase amplifier and a second common-phase amplifier, by filtering and amplifying the signal, thereby further improving the accuracy of the monitoring data; a single power supply plus common-phase amplification is used to achieve amplification and reduction of the current signal, and there is no need to use a separate circuit to generate positive and negative voltages to power the operational amplifier, thereby improving the monitoring stability.

[0048] Furthermore, the device described in the present invention sets a preset range. Since the first current value has a higher signal acquisition accuracy but a smaller range, and the second current value has a lower accuracy but a larger range, the accuracy of the monitoring result is improved by comprehensively evaluating the first current value and the second current value.

[0049] Furthermore, the device described in the present invention sets a preset fluctuation threshold. Since the current transformer is set on the cable, the distance between the cables is too close, which causes the magnetic field around the current transformer to be unstable, thereby causing the stability of the current transformer to decrease and the temperature to rise. By increasing the current monitoring frequency, the current transformer can restore stability and normal operating temperature in the next monitoring cycle, thereby improving the stability of the monitoring device and further improving the accuracy of the monitoring results.

[0050] Furthermore, the device of the present invention sets a preset number of mutation points. Due to wireless signal interference, hardware failure, software failure, changes in environmental factors and network coverage during data transmission, the stability of transmission is reduced, resulting in a mutation in the monitoring results. By increasing the information transmission power, the real-time and continuity of data transmission are improved, thereby achieving improved monitoring stability.

[0051] Furthermore, the device described in the present invention further verifies the monitoring results by setting a preset current change. Since the large current change causes the amplifier output to be saturated and thus the stability of the monitoring device to decrease, the amplification gain of the first common-phase amplifier and the second common-phase amplifier is reduced to reduce the output signal amplitude, thereby improving the stability of the monitoring device. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The overall structural block diagram of the time-sharing self-powered cable circulating current monitoring device according to the embodiment of the present invention is as follows:

[0053] Figure 2 It is a schematic diagram of the overall structure of a time-sharing self-powered cable circulating current monitoring device according to an embodiment of the present invention;

[0054] Figure 3 This is a schematic diagram of the CT energy-taking structure of the time-sharing self-powered cable circulating current monitoring device according to an embodiment of the present invention;

[0055] Figure 4 This is a schematic diagram of the structure of a current signal processing module of a time-sharing self-powered cable circulating current monitoring device according to an embodiment of the present invention;

[0056] Figure 5 This is a control logic flow chart of a main controller of a time-sharing self-powered cable circulating current monitoring device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0057] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0058] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0059] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0060] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0061] See also Figure 1 , Figure 2 , Figure 3 , Figure 4 as well as Figure 5 As shown, they are respectively an overall structural block diagram, an overall structural schematic diagram, a CT energy extraction structural schematic diagram, a current signal processing module structural schematic diagram and a control logic flow chart of the main controller of the time-sharing self-powered cable circulating current monitoring device of the embodiment of the present invention. A time-sharing self-powered cable circulating current monitoring device of the present invention comprises:

[0062] A CT energy acquisition module, which is connected to the cable and includes a current transformer for acquiring an AC current signal in the cable and a rectifier circuit connected to the current transformer for converting the AC current signal into a pulsating DC current signal;

[0063] A current signal processing module, connected to the CT energy acquisition module, for dividing the output voltage of the rectifier circuit and reducing the error of the pulsating DC current signal by outputting a first current value and a second current value;

[0064] An energy storage module, which is connected to the CT energy acquisition module, comprises an energy storage capacitor for converting the pulsating DC current signal into voltage energy for storage and a charging comparator connected to the energy storage capacitor for determining the charging state of the energy storage capacitor and the on / off state of the current signal processing module according to the real-time voltage of the energy storage capacitor;

[0065] A main controller is respectively connected to the CT energy acquisition module, the energy storage module and the current signal processing module, and is used to determine the current measurement value of the cable according to the first current value and the second current value, adjust the current monitoring frequency of the current transformer according to the fluctuation value of the current measurement value within a single monitoring cycle, and determine whether to adjust the transmission power of the current measurement value transmitted from the 4G module to the background, or adjust the amplification gain of the pulsating DC current signal according to the number of mutation points in the current change image within the single monitoring cycle.

[0066] The 4G module is connected to the energy storage module and the main controller respectively, and is used to transmit the current measurement value of the cable to the background.

[0067] Specifically, the main controller is an MCU, which samples and records the signal output by the current signal processing module through an ADC and converts it into a numerical value for calculation.

[0068] Specifically, the energy storage capacitor is also used to power the current signal processing module, the main controller and the 4G module.

[0069] Specifically, the working process of the time-sharing self-powered cable circulating current monitoring device described in the present invention is: the current transformer senses the measured current and outputs a current signal, the current transformer scales the input current signal to 1 / 1000 and inputs it into the rectifier circuit, the rectifier circuit converts the AC signal into a pulsating DC signal, in the initial state, the relay defaults to turning on the energy storage path to charge the energy storage capacitor, when the voltage of the energy storage capacitor reaches the set threshold, the charging completion comparator will monitor this state and send a charging completion signal to the system, the system will close the energy storage path of the energy storage capacitor, and activate the load path of the current signal processing module, so that the relay switches to the load path; the current of the load path is input to the first voltage divider circuit and the second voltage divider circuit. The circuit comprises a first voltage follower and a second voltage follower respectively improving the input impedance of the first voltage divider circuit and the second voltage divider circuit, a first pre-stage voltage divider and a second pre-stage voltage divider respectively divide the voltage output by the first voltage follower and the second voltage follower, and then output them to the first filter circuit and the second filter circuit respectively; the first filter circuit and the second filter circuit filter the input pulse DC signal into a DC signal, the first common-phase amplifier and the second common-phase amplifier amplify the DC signal and output it to the main controller for ADC sampling to convert the DC signal into a current value; the current value is analyzed to determine whether the current is too high, whether to adjust the interval monitoring time, whether to adjust the information transmission power, and whether to output the theoretical value of the voltage divider resistance.

[0070] In practice, the device of the present invention is provided with a CT energy acquisition module, an energy storage module, a current signal processing module, a 4G module and a main controller, and the CT energy acquisition module simultaneously completes the information collection and power storage of the measured current on the cable, thereby realizing time-sharing self-power supply and cable circulating current monitoring, and does not require an external power supply such as a battery. The wiring and installation are simple, and the installation efficiency is improved and the system failure rate is reduced. The low-power operation of the system is realized, and the current consumption reaches microampere level when in standby mode, thereby improving the endurance of the system under voltage unstable working conditions; the current signal processing module is provided to amplify and filter the current signal, and a large range and high-precision current measurement is realized at the same time, signal loss is reduced, and the current monitoring accuracy is improved; the main controller is powered by the energy storage module, and the CT energy acquisition circuit cannot be stable due to the large current fluctuation in the cable circulation. The CT energy-taking circuit obtains very limited electric energy because the cable circulating current is small. Therefore, the current monitoring device needs to operate in low-power mode. When the system is idle, the 4G module and the operational amplifier power supply are turned off, and the main controller itself enters low-power mode, leaving only the key timer running to wake up the system regularly, thereby further realizing low-power operation. By adjusting the current monitoring frequency, information transmission power and amplification gain of the pulsating DC current signal of the current transformer, the cable magnetic field is unstable due to cable aging, resulting in overheating of the current transformer, which in turn leads to a decrease in monitoring stability. By adjusting the information transmission power to increase monitoring stability, or by adjusting the amplification gain of the pulsating DC current signal, the decrease in accuracy of the monitoring results caused by cable aging can be reduced, thereby improving the accuracy and reliability of monitoring.

[0071] Specifically, the energy storage module further includes a relay connected to the rectifier circuit for switching from the energy storage path of the energy storage capacitor to the load path of the current signal processing module under the condition that the energy storage capacitor is fully charged;

[0072] The condition for the energy storage capacitor to be fully charged is that when the voltage of the energy storage capacitor reaches a preset voltage, the charging completion comparator is triggered and sends a charging completion signal to the main controller.

[0073] Specifically, the charge completion comparator is a voltage comparator that sends a charge completion signal when the voltage of the energy storage capacitor reaches its rated voltage.

[0074] In practice, the device of the present invention is provided with a current transformer, an energy storage capacitor, a relay and a charging completion comparator, and the CT power supply and current monitoring functions are completed in time-sharing through the current transformer, thereby realizing time-sharing self-powered monitoring, without the need for external power supplies such as batteries, and automatic hardware charging and discharging management; the excess current is consumed through the load path to protect the power input and current transformer of the sensitive energy storage capacitor, thereby extending the service life of the CT energy supply module; by dynamically adjusting the opening and closing of the load path, the load path can be replaced in time after the energy storage capacitor is charged, thereby improving the accuracy and stability of monitoring.

[0075] Specifically, the current signal processing module includes:

[0076] An electric energy load, which is connected to the rectifier circuit and is used to divide the output voltage of the rectifier circuit;

[0077] A primary signal processing unit connected to the electric energy load to increase input impedance;

[0078] A secondary signal processing unit is connected to the primary signal processing unit and is used for filtering and amplifying the pulsating direct current signal output by the primary signal processing unit to output the first current value and the second current value.

[0079] Wherein, the electric energy load includes:

[0080] A first voltage-dividing circuit, connected to the relay, for outputting a first divided voltage to the primary signal processing unit;

[0081] A second voltage divider circuit, connected to the first voltage divider circuit, for outputting a second divided voltage to the primary signal processing unit;

[0082] The first voltage-dividing circuit includes a first voltage-dividing resistor, and the second voltage-dividing circuit includes a second voltage-dividing resistor; the resistance value of the first voltage-dividing resistor is greater than the resistance value of the second voltage-dividing resistor.

[0083] In implementation, the device of the present invention uses a first voltage-dividing resistor with a resistance value of 4Ω and a second voltage-dividing resistor with a resistance value of 0.1Ω for monitoring operation.

[0084] In implementation, the device of the present invention realizes large-range and high-precision current measurement at the same time by setting a first voltage-dividing circuit and a second voltage-dividing circuit, so that the device can adapt to current measurement requirements in different ranges, thereby improving the flexibility and accuracy of monitoring; the larger resistance value of the first voltage-dividing resistor can ensure effective voltage division of the signal under high current conditions, while the smaller resistance value of the second voltage-dividing resistor provides sufficient signal strength under low current conditions, thereby improving the sensitivity of monitoring; in addition, by setting the resistance value of the voltage-dividing resistor, the signal processing process can be further optimized, signal distortion can be reduced, and the accuracy of the monitoring data can be improved.

[0085] Specifically, the primary signal processing unit includes:

[0086] A first voltage follower connected to the first voltage divider circuit to increase the input impedance of the first voltage divider circuit;

[0087] A second voltage follower connected to the second voltage divider circuit to increase the input impedance of the second voltage divider circuit;

[0088] a first pre-stage voltage divider connected to the first voltage follower, for dividing the voltage output by the first voltage follower and outputting the voltage to the secondary signal processing unit;

[0089] A second front-stage voltage divider is connected to the second voltage follower and is used for dividing the voltage output by the second voltage follower and outputting the voltage to the secondary signal processing unit.

[0090] Specifically, the first front-stage voltage divider divides the voltage output by the first voltage follower by 1 / 2, and the second front-stage voltage divider divides the voltage output by the second voltage follower by 1 / 2.

[0091] In implementation, the device of the present invention is used to improve the input impedance of the signal processing circuit and reduce signal loss by setting a first voltage follower, a second voltage follower, a first pre-stage voltage divider and a second pre-stage voltage divider. In order to further improve the current monitoring accuracy, it is necessary to amplify the voltage signal output by the voltage follower. Since the secondary signal processing circuit is powered by a single power supply, reverse amplification cannot be achieved, and only in-phase amplification can be used. However, the in-phase amplification circuit cannot achieve signal reduction, so the signal output by the voltage follower cannot be directly amplified. In order to use a single power supply to achieve signal amplification, a pre-stage voltage divider is used to divide the output voltage of the voltage follower, and then output it to the secondary signal processing, thereby achieving reverse amplification of the signal and improving the accuracy after amplification, thereby improving the monitoring accuracy of the current value.

[0092] Specifically, the secondary signal processing unit includes:

[0093] a first filtering circuit connected to the first front-stage voltage divider and configured to filter the pulsating DC current signal input by the first front-stage voltage divider;

[0094] a second filtering circuit connected to the second front-stage voltage divider and configured to filter the pulsating DC current signal input by the second front-stage voltage divider;

[0095] a first common-phase amplifier connected to the first filter circuit, configured to amplify the pulsating direct current signal output by the first filter circuit and output the first current value;

[0096] A second in-phase amplifier is connected to the second filtering circuit and is used for amplifying the pulsating direct current signal output by the second filtering circuit and outputting the second current value.

[0097] Specifically, the first in-phase amplifier and the second in-phase amplifier are also used to adjust and calibrate the amplification factor of the signal by adjusting the resistor.

[0098] In implementation, the device of the present invention achieves current signal calibration by setting a first filtering circuit, a second filtering circuit, a first common-phase amplifier and a second common-phase amplifier, filtering and amplifying the signal, and further improves the accuracy of the monitoring data; a single power supply plus common-phase amplification is used to achieve amplification and reduction of the current signal, and there is no need to use a separate circuit to generate positive and negative voltages to power the operational amplifier, thereby improving the monitoring stability.

[0099] Specifically, the current measurement value of the cable includes the first current value and the second current value;

[0100] Among them, the first current value is the product of the ratio of the voltage of the first voltage-dividing circuit to the sum of the first voltage-dividing resistor and the second voltage-dividing resistor and the transformation ratio parameter of the current transformer, and the second current value is the product of the ratio of the voltage of the second voltage-dividing circuit to the second voltage-dividing resistor and the transformation ratio parameter of the current transformer.

[0101] Specifically, the current value is calculated as follows:

[0102]

[0103] For the voltage value V_SENSE1 detection point of the first voltage divider circuit:

[0104]

[0105] For the voltage value V_SENSE2 detection point of the second voltage divider circuit:

[0106]

[0107] Wherein, I is the current value, R1 is the first voltage-dividing resistor, R2 is the second voltage-dividing resistor, V_SENSE1 is the voltage value of the first voltage-dividing circuit, and V_SENSE2 is the voltage value of the second voltage-dividing circuit.

[0108] The first filter circuit and the second filter circuit reflect the average value of the measured signal. Generally, the effective value is used to represent the magnitude of the AC current, so the average value needs to be converted into the effective value. For AC power, the conversion formula between the current peak value and the effective value is as follows:

[0109]

[0110] The conversion formula between the average value and peak value within a half cycle of AC current is as follows:

[0111]

[0112] Among them, I p Indicates the peak value, I avg is the average current value.

[0113] The conversion formula between effective value and average value can be obtained from formula 4 and formula 5 as follows:

[0114] I rms ≈I avg ×1.1(6)

[0115] Combining formula 1-6, the calculation formula for the measured current is as follows:

[0116]

[0117]

[0118] Where SCALE is the transformation ratio parameter of the current transformer. Using formula (7) and formula (8), the actual value of the current measurement of the cable can be calculated.

[0119] Specifically, the present invention uses a current transformer with a transformation ratio of 200:1, the operating voltage of the first common-phase amplifier and the second common-phase amplifier is 3.3V, and when the ratio of the input and output of the secondary signal processing unit is 1:1, combined with formula (2) and formula (3), the peak currents monitored by the primary signal processing unit and the secondary signal processing unit are calculated as follows:

[0120]

[0121]

[0122] Among them, I p1 Indicates the maximum peak current sampled and converted from the V_SENSE1 detection point, Ip2 represents the maximum current peak value sampled and converted by the V_SENSE2 detection point. According to formula (5), the maximum current average values ​​that can be monitored by the two signal processing circuits are:

[0123] I rmsmax1 ≈I p1 ×0.707=113.827A

[0124] I rmsmax2 ≈I p2 ×0.707=4666.2A

[0125] From the above results, it can be concluded that when the measured current is within 113A, high-precision measurement can be achieved, and when the measured current is within 113~4666A, large current measurement can be achieved.

[0126] Specifically, the main controller is connected to the current signal processing module to obtain the first current value and the second current value, and if the second current value is less than or equal to the preset range, the first current value is output as the current measurement value of the cable; if the second current value is greater than the preset range, the second current value is output as the current measurement value of the cable;

[0127] And, when the current measurement value is greater than the current measurement value threshold, it is determined that the current of the cable is too high, and the current high alarm information is reported to the background.

[0128] Specifically, the preset range is (0,113A].

[0129] Specifically, the current measurement value threshold is equal to the cable rated current.

[0130] In implementation, the device of the present invention sets a preset range. Since the first current value has a higher signal acquisition accuracy but a smaller range, and the second current value has a lower accuracy but a larger range, the accuracy of the monitoring results is improved by comprehensively evaluating the first current value and the second current value.

[0131] Specifically, the main controller is connected to the current signal processing module to obtain the current measurement value in a single monitoring cycle, calculate the fluctuation value of the current measurement value, and if the fluctuation value exceeds a preset fluctuation value, increase the current monitoring frequency of the current transformer;

[0132] Wherein, the fluctuation value is the standard deviation of the difference between the current measurement value and the average value of the current measurement value in a single monitoring cycle;

[0133] Wherein, the increase amplitude of the current monitoring frequency is positively correlated with the fluctuation value.

[0134] Specifically, the current monitoring frequency is the interval between the end time of a single monitoring cycle of the current transformer and the start time of the next adjacent monitoring cycle.

[0135] Optionally, the general value range of the duration of a single monitoring cycle is [6 hours, 10 hours].

[0136] Preferably, the preferred embodiment of the duration of a single monitoring cycle is 8 hours.

[0137] Optionally, a general value range of the preset fluctuation value is [1A, 1.04A].

[0138] Preferably, the preferred embodiment of the preset fluctuation value is 1.016A.

[0139] During implementation, when the difference between the fluctuation value and the preset fluctuation value is within 0.001A, the current monitoring frequency is increased by 0.25 hours; when the difference between the fluctuation value and the preset fluctuation value exceeds 0.001A, the current monitoring frequency is increased by 0.4 hours for every 0.001A exceeding it. For example, the fluctuation value is 1.018A, the current monitoring frequency is 1 hour, and the current monitoring frequency is increased to 1 hour + 0.25 hours + 0.4 hours = 1.65 hours.

[0140] In implementation, the device of the present invention sets a preset fluctuation threshold. Since the current transformer is set on the cable, the distance between the cables is too close, which causes the magnetic field around the current transformer to be unstable, thereby causing the stability of the current transformer to decrease and the temperature to rise. By increasing the current monitoring frequency, the current transformer can restore stability and normal operating temperature in the next monitoring cycle, thereby improving the stability of the monitoring device and further improving the accuracy of the monitoring results.

[0141] Specifically, the main controller is connected to the current signal processing module to obtain the current measurement value of the cable monitored in the single monitoring cycle, draw a change image of the current measurement value, collect the highest point of the current measurement value in the change image of the current measurement value, and if the current measurement value of the highest point is greater than the current measurement value threshold, then the highest point is determined to be a mutation point;

[0142] If the number of mutation points is greater than the preset number of mutation points, it is determined that the stability of the transmission information does not meet the requirements, and the transmission power of the current measurement value transmitted from the 4G module to the background is increased;

[0143] The increase in the information transmission power is positively correlated with the number of mutation points.

[0144] Specifically, the preset current value is 115% of the rated current of the cable.

[0145] In implementation, a current measurement value of the cable monitored within a single monitoring cycle exceeding 115% of the rated current of the cable is characterized as a sudden change current signal.

[0146] Optionally, a general value range of the preset number of mutation points is [45, 68].

[0147] Preferably, the preferred embodiment of the preset number of mutation points is 54.

[0148] Specifically, when the difference between the number of mutation points and the preset number of mutation points is within 2, the information transmission power increases by 0.5dBm; when the difference between the number of mutation points and the preset number of mutation points exceeds 2, the information transmission power increases by 0.5dBm for each additional difference. For example, if the number of mutation points is 58 and the current information transmission power is 22dBm, the information transmission power increases to 22dBm+0.5dBm+0.5dBm×2=23.5dBm.

[0149] Specifically, the increase in information transmission power cannot exceed 5dBm.

[0150] In implementation, the device of the present invention sets a preset number of mutation points. Due to wireless signal interference, hardware failure, software failure, changes in environmental factors and network coverage during data transmission, the stability of transmission decreases, resulting in mutations in monitoring results. By increasing the information transmission power, the real-time and continuity of data transmission are improved, thereby achieving improved monitoring stability.

[0151] Specifically, the main controller is connected to the current signal processing module, and is used to obtain the current measurement values ​​of adjacent monitoring time points before and after the mutation point with the largest current measurement value to calculate the current change when the current measurement value at the mutation point is greater than the preset mutation current measurement value, and if the current change is greater than the preset current change, reduce the amplification gain of the first common-phase amplifier and the second common-phase amplifier;

[0152] Among them, the current change is the difference between the current measurement value at the mutation point with the largest current measurement value and the minimum value of the current measurement values ​​at adjacent monitoring time points before and after the mutation point with the largest current measurement value; the reduction amplitude of the amplification gain of the first common-phase amplifier and the second common-phase amplifier is proportional to the current change.

[0153] Specifically, the general value range of the preset current change is [30A, 50A].

[0154] Preferably, the preset current variation is 40A.

[0155] In an implementation, the full scale of the first non-inverting amplifier and the second non-inverting amplifier is 20V.

[0156] In implementation, the new amplification gain after the reduction of the amplification gain of the first common-phase amplifier and the second common-phase amplifier is 10V divided by the ratio of the current change and the transformation ratio parameter of the current transformer. The reduction range of the amplification gain of the first common-phase amplifier and the second common-phase amplifier is the original amplification gain multiple minus the new amplification gain multiple. For example, if the current change is 45A and the current amplification gain multiple is 100 times, the new amplification gain should be 20V / (45A / 200)≈88.8 times.

[0157] During implementation, the device of the present invention further verifies the monitoring results by setting a preset current change. Since the large current change causes the amplifier output to be saturated and thus the stability of the monitoring device to decrease, the amplification gain of the first common-phase amplifier and the second common-phase amplifier is reduced to reduce the output signal amplitude, thereby improving the stability of the monitoring device.

[0158] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A time-sharing self-powered cable circulating current monitoring device, characterized in that: include: A CT energy acquisition module, which is connected to the cable and includes a current transformer for acquiring an AC current signal in the cable and a rectifier circuit connected to the current transformer for converting the AC current signal into a pulsating DC current signal; A current signal processing module, connected to the CT energy acquisition module, for dividing the output voltage of the rectifier circuit and reducing the error of the pulsating DC current signal by outputting a first current value and a second current value; An energy storage module, which is connected to the CT energy acquisition module, comprises an energy storage capacitor for converting the pulsating DC current signal into voltage energy for storage and a charging comparator connected to the energy storage capacitor for determining the charging state of the energy storage capacitor and the on / off state of the current signal processing module according to the real-time voltage of the energy storage capacitor; A main controller is respectively connected to the CT energy acquisition module, the energy storage module and the current signal processing module, and is used to determine the current measurement value of the cable according to the first current value and the second current value, adjust the current monitoring frequency of the current transformer according to the fluctuation value of the current measurement value within a single monitoring cycle, and determine whether to adjust the transmission power of the current measurement value transmitted from the 4G module to the background, or adjust the amplification gain of the pulsating DC current signal according to the number of mutation points in the current change image within the single monitoring cycle. The 4G module is connected to the energy storage module and the main controller respectively, and is used to transmit the current measurement value of the cable to the background.

2. The time-sharing self-powered cable circulating current monitoring device according to claim 1 is characterized in that: The energy storage module further includes a relay connected to the rectifier circuit for switching from the energy storage path of the energy storage capacitor to the load path of the current signal processing module under the condition that the energy storage capacitor is fully charged; The condition for the energy storage capacitor to be fully charged is that when the voltage of the energy storage capacitor reaches a preset voltage, the charging completion comparator is triggered and sends a charging completion signal to the main controller.

3. The time-sharing self-powered cable circulating current monitoring device according to claim 2 is characterized in that: The current signal processing module comprises: An electric energy load, which is connected to the rectifier circuit and is used to divide the output voltage of the rectifier circuit; A primary signal processing unit connected to the electric energy load to increase input impedance; A secondary signal processing unit is connected to the primary signal processing unit and is used for filtering and amplifying the pulsating direct current signal output by the primary signal processing unit to output the first current value and the second current value. Wherein, the electric energy load includes: A first voltage-dividing circuit, connected to the relay, for outputting a first divided voltage to the primary signal processing unit; A second voltage divider circuit, connected to the first voltage divider circuit, for outputting a second divided voltage to the primary signal processing unit; The first voltage-dividing circuit includes a first voltage-dividing resistor, and the second voltage-dividing circuit includes a second voltage-dividing resistor; the resistance value of the first voltage-dividing resistor is greater than the resistance value of the second voltage-dividing resistor.

4. The time-sharing self-powered cable circulating current monitoring device according to claim 3 is characterized in that: The primary signal processing unit comprises: A first voltage follower connected to the first voltage divider circuit to increase the input impedance of the first voltage divider circuit; A second voltage follower connected to the second voltage divider circuit to increase the input impedance of the second voltage divider circuit; a first pre-stage voltage divider connected to the first voltage follower, for dividing the voltage output by the first voltage follower and outputting the voltage to the secondary signal processing unit; A second front-stage voltage divider is connected to the second voltage follower and is used for dividing the voltage output by the second voltage follower and outputting the voltage to the secondary signal processing unit.

5. The time-sharing self-powered cable circulating current monitoring device according to claim 4 is characterized in that: The secondary signal processing unit comprises: a first filtering circuit connected to the first front-stage voltage divider and configured to filter the pulsating DC current signal input by the first front-stage voltage divider; a second filtering circuit connected to the second front-stage voltage divider and configured to filter the pulsating DC current signal input by the second front-stage voltage divider; a first common-phase amplifier connected to the first filter circuit, configured to amplify the pulsating direct current signal output by the first filter circuit and output the first current value; A second in-phase amplifier is connected to the second filtering circuit and is used for amplifying the pulsating direct current signal output by the second filtering circuit and outputting the second current value.

6. The time-sharing self-powered cable circulating current monitoring device according to claim 5, characterized in that: The current measurement value of the cable includes the first current value and the second current value; Among them, the first current value is the product of the ratio of the voltage of the first voltage-dividing circuit to the sum of the first voltage-dividing resistor and the second voltage-dividing resistor and the transformation ratio parameter of the current transformer, and the second current value is the product of the ratio of the voltage of the second voltage-dividing circuit to the second voltage-dividing resistor and the transformation ratio parameter of the current transformer.

7. The time-sharing self-powered cable circulating current monitoring device according to claim 6, characterized in that: The main controller is connected to the current signal processing module to obtain the first current value and the second current value, and if the second current value is less than or equal to a preset range, the first current value is output as the current measurement value of the cable; If the second current value is greater than the preset range, the second current value is output as the current measurement value of the cable; And, when the current measurement value is greater than the current measurement value threshold, it is determined that the current of the cable is too high, and the current high alarm information is reported to the background.

8. The time-sharing self-powered cable circulating current monitoring device according to claim 7, characterized in that: The main controller is connected to the current signal processing module to obtain the current measurement value in a single monitoring cycle, calculate the fluctuation value of the current measurement value, and increase the current monitoring frequency of the current transformer if the fluctuation value exceeds a preset fluctuation value; Wherein, the fluctuation value is the standard deviation of the difference between the current measurement value and the average value of the current measurement value in a single monitoring cycle; Wherein, the increase amplitude of the current monitoring frequency is positively correlated with the fluctuation value.

9. The time-sharing self-powered cable circulating current monitoring device according to claim 8, characterized in that: The main controller is connected to the current signal processing module to obtain the current measurement value of the cable monitored in the single monitoring cycle, draw a change image of the current measurement value, collect the highest point of the current measurement value in the change image of the current measurement value, and if the current measurement value of the highest point is greater than the current measurement value threshold, then the highest point is determined to be a mutation point; If the number of mutation points is greater than the preset number of mutation points, it is determined that the stability of the transmission information does not meet the requirements, and the transmission power of the current measurement value transmitted from the 4G module to the background is increased; The increase in the information transmission power is positively correlated with the number of mutation points.

10. The time-sharing self-powered cable circulating current monitoring device according to claim 9, characterized in that: The main controller is connected to the current signal processing module, and is used to obtain the current measurement values ​​of the adjacent monitoring time points before and after the mutation point with the largest current measurement value to calculate the current change amount when the current measurement value of the mutation point is greater than the preset mutation current measurement value, and if the current change amount is greater than the preset current change amount, reduce the amplification gain of the first common-phase amplifier and the second common-phase amplifier; Among them, the current change is the difference between the current measurement value at the mutation point with the largest current measurement value and the minimum value of the current measurement values ​​at adjacent monitoring time points before and after the mutation point with the largest current measurement value; the reduction amplitude of the amplification gain of the first common-phase amplifier and the second common-phase amplifier is proportional to the current change.

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