A sensor for measuring the temperature and current of a capacitor

Abstract

The present invention provides a sensor for measuring the temperature and current of a capacitor. The sensor housing has a housing with a center passing through the capacitor terminal. One side of the housing is provided with a heat conduction unit, which can transfer the heat dissipated by the capacitor to the sensor. The temperature of the capacitor is measured by a temperature measurement unit attached to the heat conduction unit. The measurement of the current generated during the operation of the capacitor is achieved by connecting the secondary winding of a current transformer concentric with the housing to a current measurement unit. By centrally arranging the temperature measurement and current measurement and installing them on the capacitor terminal, the sensor can achieve dead-angle-free and real-time temperature monitoring of all units of the capacitor bank, improve the sensitivity of detecting the unbalanced current of the capacitor, and realize early warning when a small number of cores of the capacitor units in the capacitor bank are damaged.

Description

Technical Field

[0001] The present invention relates to the field of power core measurement, and more particularly, to a sensor for measuring the temperature and current of a capacitor. Background Art

[0002] With the continuous development of reactive power compensation technology for AC power grids and DC power grids in China, capacitors are widely used in power systems. The number of capacitors used only for reactive power compensation has reached millions. In recent years, although there have been great improvements in production processes and dielectric material properties, capacitor failures still occur from time to time, making capacitors one of the equipment with a relatively high accident rate in power systems.

[0003] From the perspective of power grid operation, the main capacitor failures include: poor contact of wiring terminals, insulation aging, oil leakage, etc., which can cause abnormal temperature rise, bulging, or even explosion of capacitors. In actual operation, the operating state of capacitors is mainly monitored through two indicators: temperature and unbalanced current.

[0004] For capacitor temperature detection, infrared monitoring is widely used. A fixed infrared camera or a periodic infrared imager can be used for inspection. However, a fixed infrared camera is prone to monitoring dead zones, and the timeliness of inspection by an infrared imager is relatively poor.

[0005] The circuit for unbalanced current monitoring generally adopts the H-bridge connection method. Specifically, the capacitor bank is divided into two equal groups, and an unbalanced current transformer is connected between the intermediate potentials of the two groups of capacitors; or the currents of the two groups of capacitors are directly measured and compared. The H-bridge connection method has higher sensitivity than the comparison of two currents. When multiple cores in a capacitor are damaged and the unbalanced current exceeds the protection threshold, the unbalanced protection gives an alarm. However, when designing the unbalanced current transformer, it is necessary to take into account measuring extremely small unbalanced currents (generally in mA level) and withstanding large fault currents (generally in kA level), so the sensitivity is still insufficient. In order to avoid noise interference, the setting of the unbalanced current threshold cannot be too low. When the number of damaged cores is small and the change in the H-bridge unbalanced current is small and does not reach the protection threshold, no alarm will be given.

[0006] Therefore, a technology is needed that can achieve dead-zone-free and real-time temperature monitoring of all units of a capacitor bank, improve the sensitivity of capacitor unbalanced current detection, and realize early warning when a small number of cores in the capacitor units of the capacitor bank are damaged. Summary of the Invention

[0007] In order to solve the technical problems in the prior art that the measurement of capacitor temperature and current is separated, and the timeliness and accuracy of the measurement are insufficient, the present invention provides a sensor for measuring the temperature and current of a capacitor, and the sensor includes:

[0008] A housing for containing the remaining parts of the sensor except the heat conduction unit, with a through hole at its center for the capacitor terminal;

[0009] A current transformer having an annular iron core and a secondary winding wound around the iron core, the secondary winding being connected to the current measurement unit;

[0010] A heat conduction unit located on one side of the housing, with a through hole at its center for the capacitor terminal, for transferring the heat of the capacitor terminal and serving as a mounting interface, and being fastened to the capacitor terminal by the original bolts of the capacitor;

[0011] A temperature measurement unit attached to the heat conduction unit, for sending the collected temperature signal to the control unit according to the temperature data transmission instruction of the control unit, so as to measure the temperature at the capacitor terminal under monitoring;

[0012] A current measurement unit for sending the current signal output from the secondary winding of the current transformer collected to the control unit according to the current data transmission instruction of the control unit, so as to measure the current during the operation of the monitored capacitor;

[0013] A control unit for correcting the initial time of data acquisition to achieve synchronous data acquisition; regularly sending temperature data transmission instructions and current data transmission instructions to the temperature measurement unit and the current measurement unit respectively according to the set data acquisition frequency, performing edge calculation on the received temperature signal and current signal, and sending the data packet generated after packing the calculation result and the time signal to the communication unit;

[0014] A communication unit connected to the control unit, for receiving the data packet transmitted by the control unit, processing the processed packet, and converting it into a high-frequency electromagnetic wave for transmission.

[0015] Further, the sensor further includes an energy harvesting unit for supplying power to the control unit, the temperature measurement unit, the current measurement unit, and the communication unit.

[0016] Further, the energy harvesting unit is a disposable battery or a rechargeable battery with a rechargeable interface.

[0017] Further, the energy harvesting unit is a control circuit connected in series with the output terminal of the secondary winding of the current transformer and the current measurement unit, for converting the secondary current of the current transformer into a DC voltage to supply power to the current measurement unit, the temperature measurement unit, the control unit, and the communication unit.

[0018] Further, the energy harvesting unit includes:

[0019] A bypass circuit, which is configured to cut off the charging circuit according to a first cut-off instruction sent by the charging circuit during the charging process of the charging circuit, and to cut off the charging circuit according to a second cut-off instruction of the control unit when the current measurement unit is started;

[0020] A charging circuit, which is configured to convert the output current of a current transformer into a DC voltage when the current measurement unit stops working, and compare the DC voltage with a preset voltage threshold. When the DC voltage is greater than the preset voltage threshold, a first cut-off instruction is sent to the bypass circuit;

[0021] Further, the heat conduction unit is a heat conduction plate, whose shape is the same as the side of the housing, the inner diameter is smaller than the inner diameter of the housing, and larger than the diameter of the monitored capacitor terminal.

[0022] Further, the heat conduction unit is a metal sheet, whose thickness is not greater than 2 mm.

[0023] Further, the temperature measurement unit uses a digital temperature chip and is pasted on the heat conduction unit.

[0024] Further, the current measurement unit uses an AD conversion chip to convert the secondary current of the current transformer from an analog signal into a digital signal and send it to the control unit.

[0025] Further, the communication unit includes:

[0026] A communication operation module, which is configured to process the data packet transmitted by the control unit and transmit the processing result to the antenna module;

[0027] An antenna module, which is configured to convert the processing result of the communication operation module into a high-frequency electromagnetic wave for transmission.

[0028] The housing of the sensor for measuring the temperature and current of a capacitor provided by the technical solution of the present invention has a housing with a capacitor terminal passing through the center. One side of the housing is provided with a heat conduction unit, which can transfer the heat dissipated by the capacitor to the sensor. The temperature of the capacitor is measured by the temperature measurement unit attached to the heat conduction unit, and the current generated during the operation of the capacitor is measured by connecting the secondary winding of the current transformer concentric with the housing to the current measurement unit. By centrally setting the temperature measurement and current measurement and installing them on the capacitor terminal, the sensor can achieve dead-angle-free and real-time temperature monitoring of all units of the capacitor bank, improve the sensitivity of detecting the unbalanced current of the capacitor, and realize early warning when a small number of cores of the capacitor units in the capacitor bank are damaged. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] By referring to the following drawings, the exemplary embodiments of the present invention can be more fully understood:

[0030] Figure 1 Schematic structural diagram of a sensor for measuring the temperature and current of a capacitor according to a preferred embodiment of the present invention;

[0031] Figure 2 Schematic structural diagram of installing a sensor for measuring the temperature and current of a capacitor on the capacitor according to a preferred embodiment of the present invention; Detailed implementation manners

[0032] Now, exemplary embodiments of the present invention will be introduced with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely, and to fully convey the scope of the present invention to those skilled in the art. The terms in the exemplary embodiments shown in the drawings are not limitations on the present invention. In the drawings, the same units / cores are denoted by the same reference numerals.

[0033] Unless otherwise specified, the terms (including scientific and technical terms) used herein have the ordinary meaning understood by those skilled in the art. In addition, it can be understood that the terms defined in the commonly used dictionary should be understood to have a meaning consistent with the context of their related fields, and should not be understood as idealized or overly formal meanings.

[0034] Figure 1 Schematic structural diagram of a sensor for measuring the temperature and current of a capacitor according to a preferred embodiment of the present invention. As Figure 1 shown, the sensor 100 for measuring the temperature and current of a capacitor according to this preferred embodiment includes:

[0035] A housing 101, which is used to accommodate the rest of the sensor except the heat conduction unit, and has a through hole in the center that penetrates the capacitor terminal. The housing 101 is divided into two parts, where the upper half is a toroidal body and the lower half is square. There is a hole in the center of the toroidal body part, and the inner diameter of the toroid is slightly larger than the capacitor terminal mounting post, so that the sensor 100 can be sleeved on the capacitor terminal.

[0036] A current transformer 102, having a toroidal core and a secondary winding wound around the core, and the secondary winding is connected to the current measurement unit. The current transformer 102 is installed inside the housing and is concentric with the toroidal body part of the housing 101. The secondary winding of the current transformer 102 is wound around a circular closed core with enameled wire having a diameter of about 0.2 mm, and the core material is amorphous alloy. The turns ratio of the secondary winding is 100 A: 0.1 A, and the accuracy class is 0.2.

[0037] The heat conduction unit 103 is located on one side of the housing 101 and has a through-hole for the capacitor terminal in its center, which is used to transfer the heat of the capacitor terminal and serves as an installation interface, and is fastened to the capacitor terminal by the original bolts of the capacitor.

[0038] Figure 2 It is a schematic structural diagram of installing sensors for measuring the temperature and current of a capacitor on the capacitor according to a preferred embodiment of the present invention. As Figure 2 shown, for a capacitor bank, each capacitor has a terminal mounting post. Since the sensor according to the present invention has a through-hole in its center, the sensor can be conveniently fixed on the terminal mounting post, so that not only the heat on the terminal can be transferred to the sensor, but also the installation of the original connection wires is not affected, and no additional installation cost is increased.

[0039] Preferably, the heat conduction unit 103 is a heat conduction plate, whose shape is the same as that of the side of the housing, the inner diameter is smaller than the inner diameter of the housing, and larger than the diameter of the monitored capacitor terminal.

[0040] Preferably, the heat conduction unit 103 is a metal sheet, and its thickness is not more than 2 mm.

[0041] When the heat conduction unit 103 adopts a metal sheet with a thickness not more than 2 mm, on the one hand, it has good heat conduction performance, which can ensure the accuracy of the temperature measurement unit, and on the other hand, when installed at the capacitor terminal, it only occupies 2 mm of the length of the capacitor terminal bolt and does not affect the installation of the original connection wires.

[0042] The temperature measurement unit 104 is attached to the heat conduction unit 103 and is used to send the collected temperature signal to the control unit according to the temperature data transmission instruction of the control unit 106, so as to realize the measurement of the temperature at the monitored capacitor terminal.

[0043] Preferably, the temperature measurement unit 104 adopts a digital temperature chip and is pasted on the heat conduction unit 103. In addition to the digital temperature chip, other types of sensors for measuring temperature signals can be used as the temperature measurement unit.

[0044] The current measurement unit 105 is used to send the current signal output by the secondary winding of the current transformer collected to the control unit 106 according to the current data transmission instruction of the control unit 106, so as to realize the measurement of the current when the monitored capacitor is operating;

[0045] Preferably, the current measurement unit 105 uses an AD conversion chip to convert the secondary current of the current transformer from an analog signal to a digital signal and send it to the control unit.

[0046] A control unit 106, which is used to correct the initial time of data acquisition to achieve synchronous data acquisition; regularly send temperature data transmission instructions and current data transmission instructions to the temperature measurement unit and the current measurement unit respectively according to the set data acquisition frequency, perform edge computing on the received temperature signal and current signal, and send the data packet generated after packing the calculation result and the time signal to the communication unit 107.

[0047] The control unit 106 has a network time synchronization function. When monitoring the capacitor temperature and current, it can regularly receive the time signal transmitted by the communication unit 107 and correct the acquisition time through the network, so as to achieve synchronous acquisition and automatically time within a certain period. For the current signal transmitted by the current measurement unit 105, the control unit 106 obtains the effective value of the secondary current through data processing, converts it to obtain the effective value of the capacitor current, and summarizes the calculation results of the current and temperature, and regularly transmits the current, temperature and time signals to the communication unit 107 in a specified format.

[0048] A communication unit 107, which is connected to the control unit 106, is used to receive the data packet transmitted by the control unit 106, process the processing packet, and convert it into a high-frequency electromagnetic wave and transmit it.

[0049] Preferably, the communication unit 107 includes a communication operation module 171 and an antenna module 172. Among them, the communication operation module 171 is used to process the data transmitted by the control unit, and the antenna module 172 is used to communicate bidirectionally with an external wireless transceiver to exchange sensor information.

[0050] Preferably, the sensor 100 further includes an energy harvesting unit 108, which is used to supply power to the control unit 106, the temperature measurement unit 104, the current measurement unit 105 and the communication unit 107.

[0051] Preferably, the energy harvesting unit 108 is a disposable battery or a rechargeable battery with a rechargeable interface.

[0052] Preferably, the energy harvesting unit 108 is a control circuit, which is connected in series with the output end of the secondary winding of the current transformer 102 and the current measurement unit 105, and is used to convert the secondary current of the current transformer into a DC voltage to supply power to the current measurement unit 105, the temperature measurement unit 104, the control unit 106 and the communication unit 107.

[0053] Preferably, the energy harvesting unit 108 includes:

[0054] A bypass circuit, which is used to cut off the charging circuit according to the first cut-off instruction sent by the charging circuit during the charging process of the charging circuit, and cut off the charging circuit according to the second cut-off instruction of the control unit when the current measurement unit starts.

[0055] A charging circuit, which is configured to convert the output current of a current transformer into a DC voltage when the current measurement unit stops working, and compare the DC voltage with a preset voltage threshold. When the DC voltage is greater than the preset voltage threshold, a first cut-off instruction is sent to a bypass circuit.

[0056] Controlling the charging circuit through the bypass circuit can prevent the DC voltage from being too high when the energy extraction unit is the control circuit, and avoid increasing the current measurement error when the current measurement unit is working.

[0057] The present invention has been described with reference to a few embodiments. However, as is well known to those skilled in the art, other embodiments equivalent to those disclosed above of the present invention equally fall within the scope of the present invention as defined by the appended patent claims.

[0058] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless otherwise explicitly defined therein. All references to "a / the [device, component, etc.]" are to be construed openly as at least one instance of the device, component, etc., unless otherwise explicitly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed, unless explicitly stated.

[0059] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0060] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for realizing the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0061] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to work in a particular manner, such that the instructions stored in the computer-readable memory produce a manufacture including an instruction device that implements the functions specified in one or more of the processes Figure 1 or blocks Figure 1 specified in one or more of the blocks.

[0062] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable apparatus provide steps for implementing the functions specified in one or more of the processes Figure 1 or blocks Figure 1 specified in one or more of the blocks.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent replacements can still be made to the specific embodiments of the present invention. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A sensor for measuring the temperature and current of a capacitor, characterized in that, The sensor includes: A housing for containing the rest of the sensor except the heat conduction unit, and having a through hole at its center that penetrates the capacitor terminal; A current transformer having an annular iron core and a secondary winding wound around the iron core, and the secondary winding is connected to the current measurement unit; A heat conduction unit located on one side of the housing, having a through hole at its center that penetrates the capacitor terminal, for transferring the heat of the capacitor terminal and serving as an installation interface, and being fastened to the capacitor terminal by the original bolts of the capacitor; A temperature measurement unit that fits against the heat conduction unit, for sending the collected temperature signal to the control unit according to the temperature data transmission instruction of the control unit, so as to realize the measurement of the temperature at the monitored capacitor terminal; A current measurement unit for sending the current signal output from the secondary winding of the collected current transformer to the control unit according to the current data transmission instruction of the control unit, so as to realize the measurement of the current during the operation of the monitored capacitor; A control unit for correcting the initial time of data acquisition and realizing synchronous data acquisition; regularly sending temperature data transmission instructions and current data transmission instructions to the temperature measurement unit and the current measurement unit respectively according to the set data acquisition frequency, performing edge calculation on the received temperature signal and current signal, and sending the data packet generated after packing the calculation result and the time signal to the communication unit; A communication unit connected to the control unit, for receiving the data packet transmitted by the control unit, processing the data packet, and converting it into a high-frequency electromagnetic wave for transmission; 2. The sensor according to claim 1, characterized in that, The sensor further includes an energy harvesting unit for supplying power to the control unit, the temperature measurement unit, the current measurement unit, and the communication unit.

3. The sensor according to claim 2, characterized in that, The energy harvesting unit is a disposable battery or a rechargeable battery with a rechargeable interface.

4. The sensor according to claim 2, wherein The energy harvesting unit is a control circuit that is connected in series with the output end of the secondary winding of the current transformer and the current measurement unit, for converting the secondary current of the current transformer into a DC voltage to supply power to the current measurement unit, the temperature measurement unit, the control unit, and the communication unit.

5. The sensor according to claim 4, characterized in that, The energy harvesting unit includes: A bypass circuit for cutting off the charging circuit according to the first cut-off instruction sent by the charging circuit during the charging process of the charging circuit, and cutting off the charging circuit according to the second cut-off instruction of the control unit when the current measurement unit is started; A charging circuit for converting the output current of the current transformer into a DC voltage when the current measurement unit stops working, and comparing the DC voltage with a preset voltage threshold, and sending a first cut-off instruction to the bypass circuit when the DC voltage is greater than the preset voltage threshold.

6. The sensor according to claim 1, wherein The heat conduction unit is a heat conduction plate, whose shape is the same as that of the side of the housing, and the inner diameter is smaller than the inner diameter of the housing and larger than the diameter of the monitored capacitor terminal.

7. The sensor according to claim 6, characterized in that, The heat conduction unit is a metal sheet with a thickness not greater than 2 mm.

8. The sensor according to claim 1, characterized in that, The temperature measurement unit uses a digital temperature chip and is pasted on the heat conduction unit.

9. The sensor according to claim 1, wherein The current measurement unit uses an AD conversion chip to convert the secondary current of the current transformer from an analog signal into a digital signal and send it to the control unit.

10. The sensor according to claim 1, wherein The communication unit includes: A communication operation module, which is used to process the data packets transmitted by the control unit and transmit the processing results to the antenna module; An antenna module, which is used to convert the processing results of the communication operation module into high-frequency electromagnetic waves for transmission.

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