A passive compatible current sensor applicable to intelligent manufacturing and a processing method thereof

Abstract

The present invention belongs to the technical field of sensors, and discloses a passive compatible current sensor applicable to intelligent manufacturing and a processing method. In the sensor, the primary cable axially passes through the winding core and is connected in parallel with the primary busbar of the power grid to be measured; the secondary winding is wound on the winding core; the secondary output circuit successively includes: a TVS diode, a variable resistor and a micro-transformer; wherein, both ends of the TVS diode are connected in parallel across both ends of the secondary winding, both ends of the variable resistor are connected in parallel across both ends of the TVS diode, the input end of the micro-transformer is connected in parallel across both ends of the variable resistor, and the output ends respectively form a phase sequence output end and a zero sequence output end. Among them, the variable resistor is used to calibrate the relative shunt error and winding error. The present invention can realize the standardized and intelligent manufacturing of current sensors and the general application requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and particularly to a passive compatible current sensor applicable to intelligent manufacturing and a processing method thereof. Background Art

[0002] A current sensor is an electrical signal detection device, which is used to acquire a current signal, convert it into a required signal type for output, and then achieve purposes such as information processing and storage.

[0003] The through-core current sensor is the mainstream current sensor. Although it has been widely used in various electrical scenarios as a traditional circuit device with a simple structure. However, in the process of industrial development standardization and intelligent manufacturing, the existing current sensors have not been correspondingly improved with the actual development changes, resulting in the following defects in actual applications:

[0004] First of all, the existing through-core current sensors collect the full rated value of the primary rated current to be measured in the power grid. Therefore, in actual applications, different specifications of current sensors need to be designed for different primary rated currents; as a result, the current sensors cannot achieve universal design (that is, the same current sensor can meet the acquisition requirements of different primary rated currents) and standardized production.

[0005] Secondly, the acquisition of phase sequence signals and zero sequence signals cannot be compatible, that is, it is necessary to design independent phase sequence iron core windings and zero sequence iron core windings correspondingly; as a result, a large amount of manpower is consumed in the subsequent mold loading process, and the efficiency is difficult to improve.

[0006] Furthermore, after the coils of the phase sequence iron core winding and the zero sequence iron core winding are wound, it is also necessary to manually detect the coils one by one and manually adjust the number of turns of the coils based on the fair difference control principle, which is difficult to meet the current intelligent manufacturing requirements. Summary of the Invention

[0007] The purpose of the present invention is to provide a passive compatible current sensor applicable to intelligent manufacturing and a processing method thereof, so as to solve the technical problems that the existing current sensors cannot meet intelligent manufacturing, standardized production, and universal application.

[0008] To achieve the above object, the present invention proposes the following technical solutions:

[0009] In the first aspect, the present technical solution provides a passive compatible current sensor applicable to intelligent manufacturing, which sequentially includes: a primary cable, a secondary winding and a winding iron core, and a secondary output circuit;

[0010] The primary cable axially passes through the winding core and is connected in parallel with the primary busbar of the power grid to be measured; the secondary winding is wound around the winding core; the secondary output circuit successively includes: a TVS diode, a variable resistor, and a micro-transformer; wherein, both ends of the TVS diode are connected in parallel across the outgoing terminals of the secondary winding, both ends of the variable resistor are connected in parallel across both ends of the TVS diode, the input end of the micro-transformer is connected in parallel across both ends of the variable resistor, and the output ends respectively form a phase sequence output end and a zero sequence output end; wherein, the variable resistor is used to calibrate the relative shunt error of the primary cable and the winding error of the secondary winding;

[0011] And further includes the following steps:

[0012] Define the total current of the primary busbar as NI, and the shunt current of the primary cable as I2 = I / n; obtain the cross-sectional area of the primary cable as: S2 = (I / n) / j2, and obtain the cross-sectional area of the parallel part of the primary busbar in parallel with the primary cable as S1 = (NI - I / n) / j1; wherein, j1 / j2 = ρ2 / ρ1, j1 ≤ J1, j2 ≤ J2;

[0013] Wherein, I is the reference current of the primary busbar, N is any positive real number not less than 1; n is the shunt ratio of the primary cable, which is any positive real number greater than 1; j1 is the current density of the parallel part of the primary busbar, j2 is the current density of the primary cable, ρ2 is the resistivity of the primary cable, ρ1 is the resistivity of the parallel part of the primary busbar, J1 is the standard current density of the parallel part of the primary busbar, and J2 is the standard current density of the primary cable;

[0014] Calculate the relative shunt error of the shunt current on the primary cable;

[0015] Wherein, when the materials of the parallel part of the primary busbar and the primary cable are the same, the relative shunt error on the primary cable is ΔI2’ = 1 / (Nn + 1)(100%); when the materials of the parallel part of the primary busbar and the primary cable are different, the relative shunt error on the primary cable is ΔI2’ = 1 / (Nn)(100%);

[0016] Based on the materials of the parallel part of the primary busbar and the primary cable, obtain the cross-sectional area of the primary cable and the cross-sectional area of the parallel part of the primary busbar to select their specifications, and adjust the variable resistor to calibrate the relative shunt error, so that the same current sensor can achieve compatible acquisition of any rated primary current.

[0017] Further, the primary cable is a primary silicone rubber cable and is of a detachable structure.

[0018] Further, it includes a housing, and the secondary output circuit is deployed inside the housing;

[0019] An input port is provided on the housing, and the input port is connected in parallel with the secondary output circuit; the outgoing terminal of the secondary winding is detachably connected to the input port of the secondary output circuit.

[0020] Further, the housing is a metal housing, and an insulating layer is attached to the inner wall of the metal housing; the metal housing includes a main body and a top cover, and a sealing ring is provided between the main body and the top cover.

[0021] Further, a short-circuit grounding port is provided on the housing; the short-circuit grounding port is used for power frequency withstand voltage test and lightning strike test.

[0022] Further, the thermal stability value range of the adjustable resistor is: -20°C to +70°C.

[0023] Further, the material of the iron core in the micro-transformer is ultra-thin film alloy.

[0024] Further, the winding iron core is coated with liquid silicone rubber.

[0025] In a second aspect, the present technical solution provides a processing method for a passive compatible current sensor applicable to intelligent manufacturing, which is used to process the current sensor, and includes the following steps:

[0026] Wind the secondary winding around the winding iron core by a winding device; wherein, the winding error range after winding by the winding device is: not exceeding ±5%;

[0027] Based on S1=(NI-I / n) / j1, determine the cross-sectional area of the parallel part of the primary busbar, and then determine the specification of the parallel part of the primary busbar; based on S2=(I / n) / j2, determine the cross-sectional area of the primary cable, and then determine the specification of the primary cable; and incorporate the primary cable into the parallel part of the primary busbar with the above specification;

[0028] Wherein, j1 / j2=ρ2 / ρ1, j1≤J1, j2≤J2; wherein, when the materials of the parallel part of the primary busbar and the primary cable are the same, the relative shunt error on the primary cable is ΔI2’=1 / (Nn + 1)(100%); when the materials of the parallel part of the primary busbar and the primary cable are different, the relative shunt error on the primary cable is ΔI2’=1 / (Nn)(100%);

[0029] Wherein, the error range of the cross-sectional area of the parallel part of the primary busbar and the cross-sectional area of the primary cable is: not exceeding 5%;

[0030] The TVS diode, the adjustable resistor and the micro-transformer are successively connected in parallel and soldered on a PCB board, which is placed in a housing; then the outgoing terminal of the secondary winding is connected to the input port on the housing, and the adjustable resistor is adjusted to calibrate the winding error and the relative shunt error.

[0031] Further, after the TVS diode, the adjustable resistor and the micro-transformer are successively connected in parallel and soldered on a PCB board, which is placed in a housing; then the outgoing terminal of the secondary winding is connected to the input port on the housing, and the adjustable resistor is adjusted to calibrate the winding error and the relative shunt error; it includes:

[0032] Connect a voltmeter to the input end of the micro-transformer and apply a secondary load at a preset rated value of 100%.

[0033] Apply a preset shunt current to the primary cable and adjust the adjustable resistor so that the input voltage of the micro-transformer meets the preset requirements.

[0034] Judge that if the error value between the phase sequence voltage at the phase sequence output end and the zero sequence voltage at the zero sequence output end is within the error range, it is confirmed that the current sensor meets the application requirements.

[0035] Beneficial effects:

[0036] As can be seen from the above technical solutions, the technical solution of the present invention provides a passive compatible current sensor applicable to intelligent manufacturing to solve the technical defects that the existing current sensors cannot meet the requirements of intelligent manufacturing, standardized production and general application.

[0037] The sensor sequentially includes: a primary cable, a secondary winding and a winding core, and a secondary output circuit. The primary cable axially passes through the winding core and is connected in parallel with the primary bus of the power grid to be measured; the secondary winding is wound around the winding core; the secondary output circuit sequentially includes: a TVS diode, a variable resistor, and a micro-transformer; wherein, both ends of the TVS diode are connected in parallel across both ends of the secondary winding, both ends of the variable resistor are connected in parallel across both ends of the TVS diode, and the input end of the micro-transformer is connected in parallel across both ends of the variable resistor, and the output ends respectively form a phase sequence output end and a zero sequence output end. At this time, the TVS diode is used to protect the subsequent equipment against overvoltage, the variable resistor is used to convert the output current signal of the secondary winding into a voltage signal and provide it to the micro-transformer as the input voltage, and the micro-transformer is used to obtain the weak-current secondary signals output, specifically the phase sequence signal and the zero sequence signal. At the same time, in terms of error calibration, since the variable resistor is provided, the error existing in the machine winding process of the secondary winding can be calibrated, avoiding manual calibration; thus, the entire winding process no longer requires manual participation and can realize intelligent machine production. Furthermore, since a method for determining the specifications of the parallel part of the primary cable and the primary bus is also designed, that is, defining the total current of the primary bus as NI and the shunt current of the primary cable as I2 = I / n, at this time, the cross-sectional area of the primary cable is obtained as: S2 = (I / n) / j2; and the cross-sectional area of the parallel part of the primary bus is obtained as S1 = (NI - I / n) / j1. In order to improve the accuracy of obtaining the cross-sectional areas of both, the following restrictions are also made: j1 / j2 = ρ2 / ρ1, j1 ≤ J1, j2 ≤ J2; thus, the cross-sectional error caused by the insufficient actual finished product structure is avoided. At the same time, the corresponding relative shunt error is also calculated; that is, when the materials of the parallel part of the primary bus and the primary cable are the same, the relative shunt error on the primary cable is ΔI2’ = 1 / (Nn + 1)(100%); when the materials of the parallel part of the primary bus and the primary cable are different, the relative shunt error on the primary cable is ΔI2’ = 1 / (Nn)(100%). At this time, the relative shunt errors of the parallel part of the primary bus and the primary cable after the specification is selected can be eliminated based on the variable resistor to meet the actual application requirements. At this time, the current sensor can meet the compatible application under any primary rated current of the power grid, and there is no need to set current sensors of multiple specifications, thus realizing the standardized and generalized application requirements of the current sensor.

[0038] It should be understood that all combinations of the foregoing concepts and additional concepts described in more detail below can be regarded as part of the inventive subject matter of the present disclosure as long as such concepts do not conflict with each other.

[0039] The foregoing and other aspects, embodiments, and features of the teachings of the present invention can be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as the features and / or beneficial effects of exemplary embodiments, will be apparent from the following description or learned through the practice of specific embodiments in accordance with the teachings of the present invention. Brief Description of the Drawings

[0040] The drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in each figure may be represented by the same reference numeral. For the sake of clarity, not every component is labeled in each figure. Now, embodiments of various aspects of the present invention will be described by way of example and with reference to the drawings, wherein:

[0041] Figure 1 is a circuit structure diagram of the passive compatible current sensor applicable to intelligent manufacturing described in this embodiment;

[0042] Figure 2 is a hardware structure diagram of the passive compatible current sensor applicable to intelligent manufacturing described in this embodiment;

[0043] Figure 3 is a deployment diagram of the secondary output circuit on a PCB board described in this embodiment;

[0044] Figure 4 is a schematic structural diagram of the housing corresponding to the secondary output circuit described in this embodiment.

[0045] In the figure, the reference numerals are: 1 is the secondary output circuit, 2 is the winding iron core, 3 is the secondary winding, 4 is the outgoing terminal, 5 is the housing, 6 is the protective housing, 7 is the encapsulation, 8 is the epoxy resin board, and 9 is the copper foil. Detailed Embodiments

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention without creative efforts fall within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meaning as understood by those of ordinary skill in the art to which the present invention pertains.

[0047] As used in the description and claims of this application, words such as "first", "second" and similar terms do not denote any order, quantity or importance, but are only used to distinguish different components. Similarly, unless the context clearly indicates otherwise, singular words such as "a", "an" or "the" do not denote a limitation of quantity, but rather indicate the presence of at least one. Words such as "comprising" or "including" mean that the elements or items appearing before "comprising" or "including" cover the features, wholes, steps, operations, elements and / or components listed after "comprising" or "including", and do not exclude the existence or addition of one or more other features, wholes, steps, operations, elements, components and / or their collections. "Upper", "lower", "left", "right", etc. are only used to represent relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0048] In the process of the standardization and intelligent manufacturing of industrial development, the existing current sensors have not been correspondingly improved with the actual development and changes, resulting in the following defects in their actual applications: First, the existing through-core current sensors collect the full rated value of the primary rated current to be measured in the power grid. Therefore, in actual applications, current sensors of different specifications need to be designed for different primary rated currents; this further leads to the inability to achieve a universal design and standardized production of current sensors. Second, the acquisition of phase sequence signals and zero-sequence signals cannot be compatible, that is, it is necessary to design independent phase sequence iron core windings and zero-sequence iron core windings correspondingly; this further leads to time-consuming and laborious processes in subsequent die-setting processes; it is also necessary to manually detect each coil one by one, making it difficult to meet the current intelligent manufacturing requirements. Based on this, this embodiment aims to provide a passive compatible current sensor applicable to intelligent manufacturing to solve the above technical defects.

[0049] As shown in the following drawings, a specific introduction is made to the passive compatible current sensor applicable to intelligent manufacturing described in this embodiment.

[0050] Embodiment 1

[0051] Combined with Figures 1 to 4 As shown, the current sensor includes: a primary cable, a secondary winding 3, a winding iron core 2, and a secondary output circuit 1.

[0052] In terms of the specific structure, the primary cable axially passes through the winding core 2 and is connected in parallel with the primary busbar of the power grid to be measured; the secondary winding 3 is wound around the winding core 2. The winding core 2 is coated with liquid silicone rubber, and the secondary winding 3 and the winding core 2 are fixed in the protective shell 6 by means of mold, and then encapsulated in the potting 7. In this embodiment, the primary cable is specifically a primary silicone rubber cable and is designed as a detachable structure. Further, its insulation level matches the rated voltage of the connected power grid, and both ends of the primary cable are designed with structures convenient for fixed installation.

[0053] The secondary output circuit 1 successively includes: a TVS diode, a variable resistor and a micro-transformer. Specifically, both ends of the TVS diode are connected in parallel across the outgoing terminal 4 of the secondary winding 3, both ends of the variable resistor are connected in parallel across both ends of the TVS diode, the input end of the micro-transformer is connected in parallel across both ends of the variable resistor, and the output ends respectively form phase sequence output terminals Sa - San and zero sequence output terminals Sd - Sdn. In terms of the specific circuit layout, the TVS diode, the variable resistor and the micro-transformer are successively arranged on the epoxy resin board 8 and are electrically connected by copper foil 9 according to the above connection method.

[0054] Since the input value of the micro-transformer is very small, in order to meet the actual linear conversion requirements, the material of the iron core in the micro-transformer is set as ultra-thin film alloy, which has a relatively high initial magnetic permeability. At the same time, in order to meet the actual application requirements, the thermal stability value range of the variable resistor is set as: -20°C to +70°C, and the variation limit is ≤±0.5%.

[0055] Specifically, the following steps are further included for the specification selection and error calibration of the primary cable and the parallel part of the primary busbar:

[0056] First, define the total current of the primary busbar as NI, the shunt current of the primary cable as I2 = I / n, and obtain the cross-sectional area of the primary cable as: S2 = (I / n) / j2; and obtain the cross-sectional area of the parallel part of the primary busbar as S1 = (NI - I / n) / j1.

[0057] Wherein, I is the reference current of the primary busbar, N is any positive real number not less than 1; n is the shunt ratio of the primary cable, which is any positive real number greater than 1; j1 is the current surface density of the parallel part of the primary busbar, and j2 is the current surface density of the primary cable. Since the parallel part of the primary cable and the primary busbar are existing finished components, in order to avoid errors caused by finished product defects, the following constraint limitations are also made: j1 / j2 = ρ2 / ρ1, j1 ≤ J1, j2 ≤ J2. Wherein, ρ1 is the resistivity of the parallel part of the primary busbar, ρ2 is the resistivity of the primary cable; J1 is the standard current surface density of the parallel part of the primary busbar, and J2 is the standard current surface density of the primary cable.

[0058] Specifically, j1 / j2 = ρ2 / ρ1 is obtained through the following steps:

[0059] According to Ohm's law of parallel circuits, it can be known that:

[0060] I1 = [R2 / (R1 + R2)]NI (1);

[0061] I2 = [R1 / (R1 + R2)]NI (2);

[0062] Wherein, R1 is the wire resistance of the parallel part of the primary busbar, and R2 is the wire resistance of the primary cable.

[0063] Since the lengths of the parallel part of the primary busbar and the primary cable are basically equal, both are taken as L, it can be obtained that:

[0064] R1 = ρ1L / S1(3);

[0065] R2 = ρ2L / S2 (4);

[0066] Furthermore, it can be obtained that:

[0067] I1 = [ρ2S1 / (ρ1S2 + ρ2S1)]NI (5);

[0068] I2 = [ρ1S2 / (ρ1S2 + ρ2S1)]NI (6);

[0069] At the same time, from the value of current density, it can be known that:

[0070] I1 = j1S1; (7)

[0071] I2 = j2S2; (8)

[0072] Furthermore, there is the following equation relationship:

[0073] j1S1 = [ρ2S1 / (ρ1S2 + ρ2S1)]NI; (9)

[0074] j2 S2 = [ρ1 S2 / (ρ1 S2 + ρ2 S1)] NI; (10)

[0075] In summary, it can be obtained that:

[0076] j1 / j2 = ρ2 / ρ1.

[0077] Then, calculate the relative shunt error of the shunt current on the primary cable.

[0078] Specifically, when the material of the parallel part of the primary busbar is the same as that of the primary cable, the relative shunt error on the primary cable is ΔI2’ = 1 / (Nn + 1)(100%); when the material of the parallel part of the primary busbar is different from that of the primary cable, the relative shunt error on the primary cable is ΔI2’ = 1 / (Nn)(100%).

[0079] Specifically, when the materials of the two are the same, the way to obtain ΔI2’ = 1 / (Nn + 1)(100%) is as follows:

[0080] Take S1 = NI / j (mm 2 ), S2 = (I / n) / j (mm 2 ), then the absolute error of [S2 / (S1 + S2)] is:

[0081] △ = {[(I / n) / j] / [(NI - I / n) / j + (I / n) / j]} - {[(I / n) / j] / [NI / j + (I / n) / j]} = 1 / [Nn(Nn + 1)];

[0082] That is, ΔI2 = NI / [Nn(Nn + 1)] = I / [n(Nn + 1)];

[0083] The corresponding relative shunt error is: ΔI2’ = {I / [n(Nn + 1)]} / (I / n) = 1 / (Nn + 1)(100%).

[0084] When (Nn + 1) >> 1, the relative shunt error will become very small and can be corrected by adjusting the micro adjustable resistor subsequently, and it can also achieve compatible applications for a wide range of primary rated currents.

[0085] n takes the value according to the standard specified reference value, that is, 10A ≤ I2 ≤ 75A.

[0086] Specifically, when the materials of the two are different, the way to obtain ΔI2’ = 1 / (Nn) is as follows:

[0087] Similarly, the absolute error is: ΔI2 = (I / n) × [(ρ1S2) / (ρ1S2 + ρ2S1)];

[0088] Also, I2 = NI×[(ρ1S2) / (ρ1S2 + ρ2S1)];

[0089] Therefore, the corresponding relative shunt error is ΔI2’ = 1 / (Nn)(100%).

[0090] When (Nn) >> 1, the relative shunt error will become very small and can be corrected by adjusting the micro adjustable resistor subsequently, and it is also possible to achieve compatible applications for a wide range of primary rated currents.

[0091] Finally, based on the materials of the parallel part of the primary bus and the primary cable, obtain the cross-sectional area of the primary cable and the cross-sectional area of the parallel part of the primary bus to select their specifications, and adjust the adjustable resistor to calibrate the relative shunt error, so that the same current sensor can achieve compatible acquisition of any rated primary current.

[0092] In specific implementation, when obtaining the cross-sectional area, the following division is also carried out:

[0093] When the materials of the primary cable and the parallel part of the primary bus are the same, the specification confirmation is carried out according to the following steps:

[0094] The current surface density of the primary silicone rubber cable is selected according to the current surface density of the primary bus of the power grid to be measured. This is because the branch current of a parallel circuit is inversely proportional to the branch resistance, that is, when the materials of the primary cable and the parallel part of the primary bus are the same, the branch current of the parallel circuit is directly proportional to the cross-sectional area of the branch conductor.

[0095] Specifically, the ratio of the cross-sectional area size of the primary silicone rubber cable to the cross-sectional area size of the parallel part of the primary bus of the power grid to be measured is as follows: Let the current surface density of the primary bus specified by the standard be j (A / mm 2 )), then the current surface density of the primary silicone rubber cable and the current surface density of the parallel part of the primary bus are both selected as j (A / mm 2 ). Let the reference current of the power grid to be measured be I, and the shunt current of the primary silicone rubber cable is taken as I / n, where n can take any real number ≥ 1; then, the cross-sectional area of the parallel part of the primary bus is S1 = (I - I / n) / j (mm 2 ), and the cross-sectional area of the primary silicone rubber cable is S2 = (I / n) / j (mm 2 ). Among them, j1 / j2 = ρ2 / ρ1 = 1; j1 ≤ J1, j2 ≤ J2; and J1 = J2.

[0096] If the primary current of the power grid to be measured increases by N times to become NI, where N can take any real number ≥ 1, the cross-sectional area of the primary silicone rubber cable is S2 = (I / n) / j (mm 2), then as long as the cross-sectional area of the parallel part of the primary bus is taken as S1 = (NI - I / n) / j (mm 2 ), a compatible application with a wide range of primary rated currents can be achieved. Among them, the following constraints also need to be satisfied: j1 / j2 = ρ2 / ρ1 = 1; j1 ≤ J1, j2 ≤ J2; and J1 = J2.

[0097] When the materials of the primary cable and the parallel part of the primary bus are different, the specification confirmation is carried out according to the following steps:

[0098] Let the current density of the cross-section specified by the standard of the primary bus of the power grid to be measured be j1, and the cross-sectional area of the parallel part be S1; the current density of the cross-section specified by the standard of the conductor of the primary silicone rubber cable be j2, and the cross-sectional area be S2; the reference current to be measured be I. If the shunt current of the primary silicone rubber cable is taken as I2 = I / n, then the cross-sectional area of the conductor of the primary silicone rubber cable can be obtained as: S2 = I / (j2n); and the cross-sectional area of the parallel part of the primary bus is: S1 = I(n - 1) / (j1n). Among them, j1 / j2 = ρ2 / ρ1, j1 ≤ J1, j2 ≤ J2.

[0099] If the primary current of the power grid to be measured increases by N times to become NI, where N is a real number greater than 1, the shunt current of the primary silicone rubber cable is still taken as I2 = I / n, that is, S2 = I / (j2n), and then the cross-sectional area of the parallel part of the primary bus is obtained as: S1 = I(Nn - 1) / (j1n). That is, if the value of S1 is taken according to this, a compatible application with a wide range of primary rated currents can also be achieved. Among them, the following constraints also need to be satisfied: j1 / j2 = ρ2 / ρ1, j1 ≤ J1, j2 ≤ J2.

[0100] In specific implementation, the TVS diode is used for overvoltage protection of the subsequent device. The adjustable resistor is used to convert the output current signal of the secondary winding into a voltage signal and provide it to the micro-transformer as the input voltage. The micro-transformer is used to obtain the output weak-current secondary signals, specifically the phase sequence signal and the zero sequence signal. At the same time, in terms of error calibration, due to the setting of the adjustable resistor, the error existing in the machine winding process of the secondary winding can be calibrated, avoiding manual calibration. Thus, the entire winding process no longer requires manual participation and can achieve intelligent machine production. Moreover, since the selection method for the specifications of the parallel part of the primary cable and the primary busbar is also designed, that is, defining the total current of the primary busbar as NI and the shunt current of the primary cable as I2 = I / n. At this time, the cross-sectional area of the primary cable is obtained as: S2 = (I / n) / j2; and the cross-sectional area of the parallel part of the primary busbar is obtained as S1 = (NI - I / n) / j1. In order to improve the accuracy of obtaining the cross-sectional areas of both, the following restrictions are also made: j1 / j2 = ρ2 / ρ1, j1 ≤ J1, j2 ≤ J2; thus avoiding the cross-sectional error caused by the insufficient actual finished product structure. At the same time, the corresponding relative shunt error is also calculated; that is, when the materials of the parallel part of the primary busbar and the primary cable are the same, the relative shunt error on the primary cable is ΔI2’ = 1 / (Nn + 1)(100%); when the materials of the parallel part of the primary busbar and the primary cable are different, the relative shunt error on the primary cable is ΔI2’ = 1 / (Nn)(100%). At this time, the errors of the parallel part of the primary busbar and the primary cable after the specification selection can be eliminated based on the adjustable resistor to meet the actual application requirements. At this time, the current sensor can meet the compatible application under any grid primary rated current, and there is no need to set current sensors of multiple specifications, thus realizing the standardized and generalized application requirements of the current sensor.

[0101] Moreover, since the rated current of the primary silicone rubber cable is set as I / n, it is more conducive to heat dissipation during the operation of the primary conductor, reducing the high-temperature impact on the secondary winding, the winding iron core, and the distribution complete equipment. While the adjustable resistor is performing the above error calibration, it is also beneficial to enhance the flexibility of parameter matching.

[0102] As a specific implementation manner, in this embodiment, the secondary output circuit 1 is deployed in the housing 5, and an input port (S1 - S2) is provided on the housing 5. The input port (S1 - S2) is connected in parallel with the secondary output circuit 1; the lead - out terminal 4 of the secondary winding 3 is detachably connected to the input port (S1 - S2). At this time, the secondary output circuit 1 will be a detachable structure. At the same time, since the overall design of this embodiment adopts a passive principle scheme and does not require an additional working power supply, therefore, after the housing 5 is removed to remove the secondary output circuit 1 in this embodiment of the sensor, it can also be extended to the field of current transformers, enhancing the universality of practical applications. That is, when the output signal is a traditional strong - electricity signal, removing the housing 5 can meet the strong - electricity output requirements. At the same time, in order to perform subsequent power - frequency withstand voltage tests and lightning strike tests, a short - circuit grounding port is provided on the housing 5.

[0103] Embodiment 2

[0104] This embodiment also provides a processing method for a passive compatible current sensor applicable to intelligent manufacturing, which is used to process the above - mentioned current sensor. It includes the following steps:

[0105] Step S102: Wind the secondary winding on the winding core by a winding device.

[0106] In specific implementation, the winding error range after winding by the winding device is: not exceeding ±5%. Preferably, the winding error range is: not exceeding ±3%.

[0107] Step S104: Determine the cross - sectional area of the parallel part of the primary busbar based on S1=(NI - I / n) / j1, and then determine the specification of the parallel part of the primary busbar; determine the cross - sectional area of the primary cable based on S2=(I / n) / j2, and then determine the specification of the primary cable; and incorporate the primary cable into the parallel part of the primary busbar with the above - mentioned specification.

[0108] Specifically, j1 / j2 = ρ2 / ρ1, j1≤J1, j2≤J2. Among them, when the materials of the parallel part of the primary busbar and the primary cable are the same, the relative shunt error on the primary cable is ΔI2’ = 1 / (Nn + 1)(100%); when the materials of the parallel part of the primary busbar and the primary cable are different, the relative shunt error on the primary cable is ΔI2’ = 1 / (Nn)(100%).

[0109] At the same time, the error range of the cross - sectional area of the parallel part of the primary busbar and the cross - sectional area of the primary cable is not exceeding 5% to meet the actual application requirements.

[0110] Step S106: Weld the TVS diode, the adjustable resistor, and the micro-transformer in parallel on the PCB board in sequence, and place them in the housing; then connect the outgoing terminal of the secondary winding to the input port on the housing, and adjust the adjustable resistor to calibrate the winding error and the relative shunt error.

[0111] At this time, manual participation in the calibration of each turn of the winding is no longer required, thus realizing the automated production of the sensor winding and the sensor. At this time, the current sensor can meet the acquisition requirements of different rated primary currents, thus realizing the versatility and standardization of the sensor.

[0112] As a specific implementation manner, after step S106, the output signal is debugged and confirmed through the following steps to meet the actual application requirements:

[0113] Step S1072: Connect a voltmeter to the input end of the micro-transformer, and apply a secondary load at a preset rated value of 100%.

[0114] Step S1074: Apply a preset shunt current to the primary cable, and adjust the adjustable resistor so that the input voltage of the micro-transformer meets the preset requirements.

[0115] Step S1076: Judge that if the error value between the phase sequence voltage at the phase sequence output end and the zero sequence voltage at the zero sequence output end is within the error range, it is confirmed that the current sensor meets the application requirements.

[0116] Embodiment 3

[0117] Based on the above design and processing method of the current sensor, a medium-voltage current sensor with a specification of 10kV - 2000A is obtained in this embodiment.

[0118] Working principle design:

[0119] (1) Transformation of the primary current of the power grid to be measured

[0120] According to the transformation of the conductor cross-sectional area, the specific scheme is as follows:

[0121] When the materials of the primary cable and the parallel part of the primary busbar are the same, the specification confirmation is carried out according to the following steps:

[0122] The current surface density of the primary silicone rubber cable is selected according to the current surface density of the primary busbar of the power grid to be measured, because the branch current of a parallel circuit is inversely proportional to the branch resistance, that is, when the materials of the primary cable and the parallel part of the primary busbar are the same, the branch current of the parallel circuit is directly proportional to the branch conductor cross-sectional area.

[0123] Specifically, the ratio of the cross-sectional area size of the primary silicone rubber cable to the cross-sectional area size of the parallel part of the primary busbar of the power grid to be measured is as follows: Let the current surface density of the primary busbar specified by the standard be j (A / mm 2 ), then the current surface density of the primary silicone rubber cable and the current surface density of the parallel part of the primary busbar are both selected as j (A / mm 2 ). Let the reference current of the power grid to be measured be I, and the shunt current of the primary silicone rubber cable is taken as I / n, where n can be any real number greater than or equal to 1; then, the cross-sectional area of the parallel part with the primary busbar is S1 = (I - I / n) / j (mm 2 ), and the cross-sectional area of the primary silicone rubber cable is S2 = (I / n) / j (mm 2 ). Among them, j1 / j2 = ρ2 / ρ1 = 1; j1 ≤ J1, j2 ≤ J2; and J1 = J2.

[0124] If the primary current of the power grid to be measured increases by N times to become NI, where N can be any real number greater than or equal to 1, and the cross-sectional area of the primary silicone rubber cable is S2 = (I / n) / j (mm 2 ), then as long as the cross-sectional area of the parallel part with the primary busbar is taken as S1 = (NI - I / n) / j (mm 2 ); that is, a compatible application with a wide range of primary rated currents can be achieved. Among them, the following constraints also need to be satisfied: j1 / j2 = ρ2 / ρ1 = 1; j1 ≤ J1, j2 ≤ J2; and J1 = J2.

[0125] When the materials of the primary cable and the parallel part of the primary busbar are different, the specification confirmation is carried out according to the following steps:

[0126] Let the current surface density of the primary busbar of the power grid to be measured specified by the standard be j1, and the cross-sectional area of the parallel part be S1; the current surface density of the conductor of the primary silicone rubber cable specified by the standard be j2, and the cross-sectional area be S2; the reference current to be measured be I. If the shunt current of the primary silicone rubber cable is taken as I2 = I / n, then the cross-sectional area of the conductor of the primary silicone rubber cable can be obtained as: S2 = I / (j2n); and the cross-sectional area of the parallel part of the primary busbar is: S1 = I(n - 1) / (j1n). Among them, j1 / j2 = ρ2 / ρ1, j1 ≤ J1, j2 ≤ J2.

[0127] If the primary current of the power grid to be measured increases by N times to become NI, where N is a real number greater than 1, and the shunt current of the primary silicone rubber cable is still taken as I2 = I / n, that is, S2 = I / (j2n), and then the cross-sectional area of the parallel part of the primary busbar is obtained as: S1 = I(Nn - 1) / (j1n), that is, if the S1 value is taken according to this, a compatible application with a wide range of primary rated currents can also be achieved. Among them, the following constraints also need to be satisfied: j1 / j2 = ρ2 / ρ1, j1 ≤ J1, j2 ≤ J2.

[0128] (2)Conductor current transformation of the primary silicone rubber cable:

[0129] The primary silicone rubber cable symmetrically passes through the circular hole of the winding core around which the coil is wound. When there is a current in the primary silicone rubber cable (i.e., the shunt part of the transformation of the primary current of the power grid to be measured), an induced current reduced in proportion, that is, the secondary current, will be generated in the secondary coil.

[0130] (3)Current-voltage conversion:

[0131] To facilitate the standardized production of the micro-transformer, a micro-adjustable resistor is used to convert the secondary current into a standard voltage as the input voltage of the micro-transformer. The standard voltage generally takes 10V - 15V to ensure the safe and reliable operation of the micro-transformer.

[0132] (4)Convert the 10V - 15V voltage signal into a standard phase-sequence voltage signal and a zero-sequence voltage signal:

[0133] Through the micro-transformer, the standard voltage at the input end of the micro-transformer is transformed into a phase-sequence voltage of 1V and a zero-sequence voltage of 0.2V at the output end.

[0134] (5)Working principle of the protection circuit

[0135] For overvoltage protection, high-power TVS diodes are connected in parallel across the input end of the micro-transformer to achieve overvoltage protection. It should be noted here that they cannot be connected in parallel across the output end of the micro-transformer to avoid the serious impact on the micro-transformer caused by the short circuit of the high-power TVS diode during transient overvoltage protection. Generally, 1.2 - 1.5 times the input voltage of the micro-transformer is taken as the conduction action voltage of the high-power discharge diode.

[0136] When one of the following abnormal conditions occurs, the high-power discharge diode TVS will act: ① The secondary output end composed of the coil and the winding core is open; ② Overcurrent impact causes the voltage at the start end of the secondary output of the coil and the winding core to be higher than the set conduction voltage of the TVS diode. Thus, the purpose of limiting overvoltage is achieved, and the protection of the secondary output circuit and the terminal phase-sequence load and zero-sequence load is realized.

[0137] When the following conditions occur, the high-power discharge diode TVS will not act: ① The secondary output end of the coil and the winding core is short-circuited; ② The phase-sequence and zero-sequence loads are not connected.

[0138] Overall design of electrical parameters

[0139] (1) Rated insulation level: 10kV / 42kV / 75kV;

[0140] (2) Rated current: Total current of the primary busbar: 2000 A; Shunt current of the primary silicone rubber insulated cable of the current sensor: 50 A (taking n = 40); Secondary current of the current sensor: 0.2 A;

[0141] (3) Input voltage of the micro-transformer: 10 V;

[0142] (4) Rated secondary signal output voltage: Phase sequence 1 V, zero sequence 0.2 V;

[0143] (5) Accuracy: Phase sequence 0.5 level, zero sequence 5P level;

[0144] (6) Load: ≥20 kΩ;

[0145] (7) Creepage distance design: Outer creepage distance ≥250 mm.

[0146] Design, manufacture or preparation of main components and parts

[0147] (1)Determine the primary silicone rubber cable:

[0148] The primary silicone rubber cable adopts a detachable structure, and its insulation level matches the rated voltage of the power grid connected. Both ends of the cable are designed with a structure convenient for fixed installation. The specification confirmation is carried out according to the above method (the above has been specifically described and will not be repeated here).

[0149] (2)Winding iron core and secondary winding:

[0150] The magnetic flux density of the iron core is designed according to 50 A; For the convenience of automatic production, a set of coil windings and the winding iron core are used to complete the acquisition of phase sequence and zero sequence signals. Material of the secondary winding: Insulated enameled purple copper wire; Cross-sectional area of the wire: Selected according to the actual application conditions and national standards. The winding is wound according to the calculated number of turns, and the error is controlled within ±3%, and no semi-finished product test and verification are required;

[0151] (3)Outer protective shell of the secondary winding:

[0152] Material and structure: The inner layer is silicone rubber with relatively soft elasticity, and the outer layer is nylon with good elasticity.

[0153] (4)Epoxy resin: Flame retardant ULV0; Glass transition temperature 80 °C; There is a cavity at the bottom of the epoxy resin encapsulation for installing the secondary output circuit housing.

[0154] (5)Secondary output circuit printed circuit board:

[0155] Material: Epoxy resin board, thickness 2 mm; Conductive copper foil: Thickness 100 μm, width 6 mm; Coated with anti-oxidation paint on the surface.

[0156] (6)Micro adjustable resistor for current-voltage conversion:

[0157] Calculated according to a voltage of 10V and a current of 0.2A, the resistance value should be 50Ω. The actual resistance value is 75Ω, and the power is 5W, all with a certain margin. And it is soldered on the PCB circuit board.

[0158] (7) Miniature transformer:

[0159] The rated primary voltage is 10V; the measured secondary voltage is 1V; the secondary zero-sequence voltage is 0.2V. And it is soldered on the PCB circuit board.

[0160] (8) TVS diode:

[0161] The overvoltage protection TVS tube uses 15V / 1000W. And it is soldered on the PCB circuit board.

[0162] (9) The housing of the secondary output circuit:

[0163] The material is PBT flame-retardant ULV0; the sealing ring material is silicone rubber.

[0164] Assembly, injection molding, calibration

[0165] (1) Formation of the current sensor main body:

[0166] ① Connection and drying: Connect the outgoing wire terminals of the wound secondary winding to the wiring terminals, and perform high-temperature drying treatment at 110°C for 3h. ② Molding: Place symmetrically in the die-casting mold. ③ Die-casting: Inject epoxy resin and initially cure at 110°C for 1h. ④ Demolding and secondary curing: After demolding, cure at 95°C for 8h and 110°C for 8h. ⑤ Arrange the mounting base plate.

[0167] (2) Assembly of the secondary output circuit wiring: Solder the incoming and outgoing wires of the circuit board with the components soldered; and place it in the housing and fix it.

[0168] (3) Debugging and calibration of errors:

[0169] First, connect the wires according to the electrical schematic diagram, and connect a digital voltmeter to the input end of the miniature transformer.

[0170] Second, apply the secondary load at 100% of the rated value.

[0171] Then, apply the rated primary current, that is, I2 = 50A, and adjust the miniature adjustable resistor R for current-voltage conversion to make the voltage at the input end of the miniature transformer 10V.

[0172] Furthermore, observe whether the phase sequence voltage and zero-sequence voltage errors meet the requirements.

[0173] Finally, cover the top cover of the housing of the secondary output circuit, pad the sealing ring, and tighten the screws to fix it.

[0174] (4) Assembly.

[0175] Final product inspection

[0176] (1) Power frequency withstand voltage and partial discharge test:

[0177] First, connect the short - circuit grounding terminal of the secondary output circuit, the secondary terminal of the current sensor, and the grounding terminal together, and then connect them to the grounding wire of the high - voltage test bench. Pass the primary silicone rubber cable through the round hole of the winding core, twist the two ends of the cable together, and then connect them to the connection wire at the high - voltage end of the high - voltage test bench.

[0178] Then, raise the voltage uniformly to 42 kV and maintain it for 1 minute. During this period, there should be no breakdown or flashover of the product.

[0179] Continuously, after the voltage application time is up, lower the voltage uniformly to 14.4 kV and maintain it for 1 minute to observe partial discharge. During this period, the partial discharge quantity should be less than 10 pc.

[0180] After the test is completed, lower the voltage to 0 and then remove the sensor product.

[0181] (2) Lightning impulse test:

[0182] The standard lightning impulse voltage is a double - exponential wave with a front time T1 of 1.2 μs and a half - wave peak time T2 of 50 μs; the standard lightning impulse chopped wave is a voltage wave generated by truncating the standard lightning shock wave by an external gap after 2 μs - 5 μs. The deviation between the actual test waveform and the standard waveform should meet the requirements of GB / T16927.1 - 2011.

[0183] First, connect the short - circuit grounding terminals S1’ and S2’ of the secondary output circuit, the secondary terminals Sa - San, Sd - Sdn of the current sensor, and the grounding terminal together, and then connect them to the grounding wire of the high - voltage test bench. Pass the primary silicone rubber cable through the round hole of the sensor, twist the two ends of the cable together, and then connect them to the connection wire at the high - voltage end of the lightning impulse test bench.

[0184] Then, apply lightning impulses: Apply 5 positive - polarity lightning impulses with a peak value of 75 kV to the product.

[0185] After completing the positive - polarity lightning impulse test voltage, apply 1 negative - polarity lightning impulse voltage, and then apply 2 lightning chopped - wave voltages.

[0186] Continuously, apply 4 more lightning impulse voltages with a peak value of 75 kV.

[0187] If there is no breakdown or flashover during the test, when returning to the initial working state and retesting the product error, if the change in error does not exceed 1 / 2 of the error limit, the test is considered qualified.

[0188] (3)Precision error retest:

[0189] Meet the standard requirements or user requirements.

[0190] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field to which the present invention pertains can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to what is defined by the claims.

Claims

1. A passive compatible current sensor applicable to intelligent manufacturing, characterized in that, Including in order: Primary cable, secondary winding and winding core, secondary output circuit; The primary cable passes through the winding core axially and is connected in parallel with the primary busbar of the power grid to be tested; The secondary winding is wound on the winding core; the secondary output circuit includes: a TVS diode, an adjustable resistor and a micro transformer in sequence; wherein, the two ends of the TVS diode are connected in parallel across the output terminals of the secondary winding, the two ends of the adjustable resistor are connected in parallel across the two ends of the TVS diode, the input end of the micro transformer is connected in parallel across the two ends of the adjustable resistor, and the output ends form a phase sequence output end and a zero sequence output end respectively; wherein, the adjustable resistor is used to calibrate the relative shunt error of the primary cable and the winding error of the secondary winding; And also includes the following steps: Define the total current of the primary bus as NI, and the shunt current of the primary cable as I2=I / n; obtain the cross-sectional area of the primary cable as: S2=(I / n) / j2, and obtain the cross-sectional area of the parallel part of the primary bus connected in parallel with the primary cable as S1=(NI-I / n) / j1; wherein j1 / j2=ρ2 / ρ1, j1≤J1, j2≤J2; Where, I is the reference current of the primary bus, N is any positive real number not less than 1; n is the current split ratio of the primary cable, which is any positive real number greater than 1; j1 is the current surface density of the parallel part of the primary bus, j2 is the current surface density of the primary cable, ρ2 is the resistivity of the primary cable, ρ1 is the resistivity of the parallel part of the primary bus, J1 is the standard current surface density of the parallel part of the primary bus, and J2 is the standard current surface density of the primary cable; Calculate the relative shunt error of the shunt current on the primary cable; Wherein, when the material of the primary busbar parallel part is the same as that of the primary cable, the relative shunt error on the primary cable is ΔI2'=1 / (Nn+1)(100%); when the material of the primary busbar parallel part is different from that of the primary cable, the relative shunt error on the primary cable is ΔI2'=1 / (Nn)(100%); Based on the materials of the primary busbar parallel part and the primary cable, the cross-sectional area of the primary cable and the cross-sectional area of the primary busbar parallel part are obtained to select the specifications of the two, and the adjustable resistor is adjusted to calibrate the relative shunt error, so that the same current sensor can achieve compatible collection of any rated primary current.

2. The passive compatible current sensor applicable to intelligent manufacturing according to claim 1, wherein The primary cable is a primary silicone rubber cable and has a detachable structure.

3. The passive compatible current sensor applicable to intelligent manufacturing according to claim 1, characterized in that, comprising a housing, wherein the secondary output circuit is disposed in the housing; The housing is provided with an input port, and the input port is connected in parallel with the secondary output circuit; the output terminal of the secondary winding is detachably connected to the input port of the secondary output circuit.

4. The passive compatible current sensor applicable to intelligent manufacturing according to claim 3, characterized in that, The shell is a metal shell, and an insulating layer is attached to the inner wall of the metal shell; the metal shell includes a main body and a top cover, and a sealing ring is provided between the main body and the top cover.

5. The passive compatible current sensor applicable to intelligent manufacturing according to claim 3, characterized in that, The shell is provided with a short-circuit grounding port; the short-circuit grounding port is used for performing power frequency withstand voltage test and lightning strike test.

6. The passive compatible current sensor applicable to intelligent manufacturing according to claim 1, characterized in that, The thermal stability value range of the adjustable resistor is: -20°C to +70°C.

7. The passive compatible current sensor applicable to intelligent manufacturing according to claim 1, wherein The material of the iron core in the micro-transformer is ultra-thin film alloy.

8. The passive compatible current sensor applicable to intelligent manufacturing according to claim 1, characterized in that, The winding iron core is coated with liquid silicone rubber.

9. A processing method for a passive compatible current sensor applicable to intelligent manufacturing, characterized in that, For processing the current sensor described in claims 1 to 8, the following steps are included: Wind the secondary winding on the winding iron core by a winding device; wherein, the winding error range after winding by the winding device is: not exceeding ±5%; Determine the cross-sectional area of the parallel part of the primary busbar based on S1 = (NI - I / n) / j1, and then determine the specification of the parallel part of the primary busbar; determine the cross-sectional area of the primary cable based on S2 = (I / n) / j2, and then determine the specification of the primary cable; and incorporate the primary cable into the parallel part of the primary busbar with the above specification; Wherein, j1 / j2 = ρ2 / ρ1, j1 ≤ J1, j2 ≤ J2; wherein, when the materials of the parallel part of the primary busbar and the primary cable are the same, the relative shunt error on the primary cable is ΔI2’ = 1 / (Nn + 1)(100%); when the materials of the parallel part of the primary busbar and the primary cable are different, the relative shunt error on the primary cable is ΔI2’ = 1 / (Nn)(100%); Wherein, the error range of the cross-sectional area of the parallel part of the primary busbar and the cross-sectional area of the primary cable is: not exceeding 5%; Weld the TVS diode, the adjustable resistor and the micro-transformer in parallel on the PCB board in sequence and place them in the housing; then connect the outgoing terminal of the secondary winding to the input port on the housing, and adjust the adjustable resistor to calibrate the winding error and the relative shunt error.

10. The processing method of the passive compatible current sensor applicable to intelligent manufacturing according to claim 9, characterized in that, After welding the TVS diode, the adjustable resistor and the micro-transformer in parallel on the PCB board in sequence and placing them in the housing; then connecting the outgoing terminal of the secondary winding to the input port on the housing, and adjusting the adjustable resistor to calibrate the winding error and the relative shunt error; it includes: Connect a voltmeter to the input end of the micro-transformer and apply a secondary load at a preset rated value of 100%; Apply a preset shunt current to the primary cable and adjust the adjustable resistor to make the input voltage of the micro-transformer meet the preset requirements; Judge that if the error value between the phase sequence voltage at the phase sequence output terminal and the zero sequence voltage at the zero sequence output terminal is within the error range, it is confirmed that the current sensor meets the application requirements.

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