A current measurement circuit for a range non-linear surge arrester monitor

Abstract

The utility model relates to measurement technical field especially a kind of current measurement circuit suitable for range nonlinear lightning arrester monitor, it includes, lightning arrester main body, zinc oxide valve, power big resistance R1, rectifier bridge, current-limiting resistance piece, shunt resistance R5, compensation resistance R6 and direct current ammeter;The lightning arrester is connected in series with the zinc oxide valve;The input end of the rectifier bridge is connected in parallel with the zinc oxide valve;The shunt resistance R5 is connected in parallel with compensation resistance R6 and direct current ammeter;It is by primary protection circuit, secondary protection circuit and tertiary protection circuit and constitutes multistage protection circuit, withstands the big impact current generated by lightning stroke, ensure the voltage, current stability of measurement loop under lightning stroke etc. Extreme working condition, and can offset the resistance change in direct current ammeter caused by temperature, effectively improve the accuracy of the measurement result of direct current ammeter, realize the accurate monitoring of leakage current.

Description

Technical Field

[0001] This utility model relates to the field of measurement technology, and in particular to a current measurement circuit suitable for a range-nonlinear surge arrester monitor. Background Technology

[0002] Surge arrester monitors are widely used for measuring the leakage current of surge arresters. When a surge arrester is in operation, it is accompanied by the generation of lightning current. Lightning current is characterized by its short duration and large impulse current. During a lightning strike, the large impulse current acts on the surge arrester monitor through the surge arrester. The DC ammeter is one of the more vulnerable components in the entire monitor. Therefore, to accurately measure the leakage current of a surge arrester, it is necessary to first address the surge arrester monitor's resistance to impulses, fully protect the DC ammeter and other measuring elements, and improve the reliability of the surge arrester monitor.

[0003] Chinese utility model application CN205333720 U discloses an online current monitor for surge arresters with nonlinear range, including a signal sampling circuit, an AC / DC conversion circuit, a charging / discharging and filtering circuit, a current limiting and counting circuit, an overcurrent protection circuit, and a measurement and shunt circuit. This online current monitor for surge arresters ignores the influence of temperature on the internal resistance of the DC ammeter. Specifically, the resistance of the enameled wire of the magnetic core inside the DC ammeter changes with temperature. In the same region, the temperature can vary by tens of degrees between summer and winter. The resistive material inside the enameled wire will undergo thermal expansion and contraction, resulting in a change in the cross-sectional area of ​​the conductor and a change in resistance. The maximum change range can reach hundreds of ohms. When the internal resistance of the DC ammeter changes in this way, the current through the branch where the DC ammeter is located will change accordingly, ultimately leading to inaccurate measurement by the DC ammeter and the inability to achieve accurate monitoring of leakage current. Utility Model Content

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the present invention.

[0005] In view of the problem in the above or existing technologies that temperature changes cause changes in the internal resistance of the DC ammeter, resulting in inaccurate DC ammeter measurements and the inability to accurately monitor leakage current, this utility model is proposed.

[0006] Therefore, the purpose of this invention is to provide a current measurement circuit suitable for a range-nonlinear surge arrester monitor.

[0007] To solve the above-mentioned technical problems, this utility model provides the following technical solution: It includes a surge arrester body; a zinc oxide valve plate connected in series on the surge arrester body; a rectifier bridge connected in parallel on the zinc oxide valve plate; a high-power resistor disposed between the rectifier bridge and the zinc oxide valve plate; a current-limiting resistor connected in series on the rectifier bridge; a shunt resistor and a compensation resistor connected in series on the current-limiting resistor; a DC ammeter connected in series on the compensation resistor; the shunt resistor connected in parallel on the series circuit formed by the compensation resistor and the DC ammeter; the DC ammeter connected to the rectifier bridge; and a grounding module, wherein the zinc oxide valve plate is connected to the grounding module, and the rectifier bridge is connected to the grounding module.

[0008] As a preferred embodiment of this utility model for current measurement circuit of a range-nonlinear surge arrester monitor, it further includes: a filter capacitor connected in parallel to the rectifier bridge; a counter connected in series with the current-limiting resistor; a varistor connected in series with the high-power resistor and connected to the lower end of the zinc oxide valve plate; and a voltage regulator whose positive terminal is connected to the negative terminal of the negative side of the rectifier bridge.

[0009] As a preferred embodiment of this utility model for current measurement circuit of range-nonlinear surge arrester monitor, wherein: the voltage regulator includes a voltage regulator diode, the voltage regulator diode is connected in parallel with the varistor, and the voltage regulator diode is connected in series with the current-limiting resistor.

[0010] As a preferred embodiment of this utility model for current measurement circuit of range-nonlinear surge arrester monitor, wherein: the counter, the Zener diode, and the positive terminal of the Zener diode are connected to the negative terminal of the negative side of the rectifier bridge.

[0011] As a preferred embodiment of this utility model for current measurement circuit of range-nonlinear surge arrester monitor, the varistor includes a varistor connected in series with a high-power resistor, and a varistor connected in parallel across the Zener diode.

[0012] As a preferred embodiment of this utility model for the current measurement circuit of a range-nonlinear surge arrester monitor, the current-limiting resistor includes: a first current-limiting resistor connected in series with the positive terminal of a filter capacitor; a second current-limiting resistor connected in series with a Zener diode; and a third current-limiting resistor connected in series with the second current-limiting resistor.

[0013] As a preferred embodiment of this utility model for the current measurement circuit of a range-nonlinear surge arrester monitor, wherein the high-power resistor and the varistor constitute a first-level protection circuit.

[0014] As a preferred embodiment of this utility model for the current measurement circuit of a range-nonlinear surge arrester monitor, the Zener diode and the varistor constitute a secondary protection circuit.

[0015] As a preferred embodiment of this utility model for the current measurement circuit of a range-nonlinear surge arrester monitor, the Zener diode and the current-limiting resistor constitute a three-level protection circuit.

[0016] The beneficial effects of this utility model on the current measurement circuit of a range-nonlinear surge arrester monitor are as follows: This utility model uses a multi-level protection circuit consisting of a primary protection circuit, a secondary protection circuit, and a tertiary protection circuit to resist the large inrush current generated by lightning strikes, ensuring the stability of the voltage and current of the measurement circuit under extreme conditions such as lightning strikes. By matching and adjusting the values ​​of the shunt resistor, the compensation resistor, and the internal resistance of the DC ammeter, the changes in the internal resistance of the DC ammeter caused by temperature are offset, effectively improving the accuracy of the DC ammeter measurement results and realizing accurate monitoring of leakage current. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Among them:

[0018] Figure 1 This is an overall schematic diagram of the current measurement circuit suitable for a range-nonlinear surge arrester monitor.

[0019] Figure 2 This is a schematic diagram of the current flow direction in a current measurement circuit suitable for a non-linear range surge arrester monitor. Detailed Implementation

[0020] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0023] Example 1

[0024] Reference Figures 1-2 This is the first embodiment of the present invention, which provides a current measurement circuit suitable for a range-nonlinear surge arrester monitor. It includes: a surge arrester body A1; a zinc oxide valve plate A2 connected in series with the surge arrester body A1; a rectifier bridge A3 connected in parallel with the zinc oxide valve plate A2; a high-power resistor R1 disposed between the rectifier bridge A3 and the zinc oxide valve plate A2; a current-limiting resistor 1 connected in series with the rectifier bridge A3; a shunt resistor R5 and a compensation resistor R6 connected in series with the current-limiting resistor 1; a DC ammeter A4 connected in series with the compensation resistor R6; the shunt resistor R5 connected in parallel with the series circuit formed by the compensation resistor R6 and the DC ammeter A4; the DC ammeter A4 and the rectifier bridge A3 connected; and a grounding module A5, with the zinc oxide valve plate A2 connected to the grounding module A5 and the rectifier bridge A3 connected to the grounding module A5.

[0025] Specifically, the zinc oxide varistor A2 absorbs the surge current energy of the arrester body A1, protecting the subsequent circuits. The rectifier bridge A3 converts the AC current into DC current. The high-power resistor R1 matches the zinc oxide varistor A2, consuming the energy of the instantaneous large surge current. The shunt resistor R5 is the matching resistor for the non-uniform scale DC ammeter, connected in parallel with the branch containing the DC ammeter A4 and the compensation resistor R6 to calibrate the shunt current. The compensation resistor R6 is a temperature compensation resistor, improving the DC ammeter branch current's resistance to temperature interference and compensating for the influence of temperature changes on the DC ammeter's internal resistance. The DC ammeter A4 displays the leakage current data. The grounding module A5 allows the current to flow to the ground. The zinc oxide varistor A2 is located between the arrester body A1 and the grounding module A5. The resistance value of the compensation resistor R6 must be much greater than the internal resistance of the DC ammeter A4, at least 100 times. The varistor is disc-shaped, 60mm in diameter and 5mm in height, adapting to the circuit's current conduction requirements.

[0026] Furthermore, it also includes a filter capacitor C1, which is connected in parallel to the rectifier bridge A3; a counter A6, which is connected in series with the current-limiting resistor 1; a varistor 12, which is connected in series with the high-power resistor R1 and connected to the lower end of the zinc oxide valve plate A2; a Zener diode 2, whose positive terminal is connected to the negative terminal of the negative side of the rectifier bridge A3; the Zener diode 2 includes a Zener diode D1, which is connected in parallel with the varistor 12, and a Zener diode D2 connected in series with the current-limiting resistor 1; the positive terminals of the counter A6, Zener diode D1, and Zener diode D2 are connected to the negative terminal of the negative side of the rectifier bridge A3.

[0027] The filter capacitor C1 smooths the leakage current that has been rectified by the rectifier bridge A3, reducing the ripple component in the current and outputting a more stable DC signal. The counter A6 records the number of times the surge arrester body A1 operates. The Zener diode D1 is the second-stage voltage limiting element, protecting the DC ammeter. The Zener diode D2 is the third-stage voltage limiting element, protecting the DC ammeter. The current limiting resistor 1, the counter A6, and the Zener diode D1 are connected in series. The counter A6 and the Zener diode D1 are connected in parallel with the filter capacitor C1.

[0028] Furthermore, the varistor 12 includes a varistor RL1 connected in series with the high-power resistor R1, and a varistor RL2 connected in parallel across the Zener diode D2; the current-limiting resistor 1 includes a first current-limiting resistor R2 connected in series with the positive terminal of the filter capacitor C1; a second current-limiting resistor R3 connected in series with the Zener diode D2; and a third current-limiting resistor R4 connected in series with the second current-limiting resistor R3.

[0029] Among them, varistor RL1 is the first-stage voltage limiting element, protecting the DC ammeter. Varistor RL2, combined with Zener diode D1, limits the circuit voltage, protecting the DC ammeter. Current-limiting resistor R2 prevents damage to circuit components when the circuit carries an excessive current for an extended period. Current-limiting resistors R3, R4, R5, R6, and DC ammeter A4 form a series-parallel circuit, which shunts the circuit current and protects the components when the circuit carries an excessive current for an extended period. A high-power resistor R1 is connected in series at the upper end of zinc oxide valve plate A2, and then connected to the varistor. The resistor RL1 is connected to the lower end of the zinc oxide valve plate A2. The negative terminal of the negative side of the rectifier bridge A3 is connected in parallel with the filter capacitor C1. The current limiting resistor R3 is connected in series with the Zener diode D2, and then in parallel across the varistor RL2. The current limiting resistor R4 is located between the current limiting resistor R3 and the shunt resistor R5. The current through the current limiting resistor R4 is equal to the sum of the current through the shunt resistor R5 and the current through the compensation resistor R6. It should be noted that the current through the compensation resistor R6 is consistent with the current of the DC ammeter A4, ensuring that the ammeter can accurately collect the branch current and avoid measurement deviation caused by shunt current.

[0030] During use, the leakage current of the surge arrester body A1 is rectified by the rectifier bridge A3, generating a DC signal on the negative side. By matching and adjusting the values ​​of the shunt resistor R5, the compensation resistor R6, and the internal resistance of the DC ammeter A4, the current in the circuit can be measured, which can accurately indicate the magnitude of the current in the circuit. Specifically, when the temperature changes and the internal resistance of the DC ammeter A4 changes, since the compensation resistor R6 and the DC ammeter A4 are connected in series and the compensation resistor R6 is much larger than the internal resistance of the DC ammeter A4, the total resistance of the branch where the compensation resistor R6 and the DC ammeter A4 are located remains basically unchanged. The current in this branch remains unchanged, and the measured value of the DC ammeter A4 remains unchanged, so the magnitude of the current is not affected by the ambient temperature, effectively improving the accuracy of the measurement result of the DC ammeter A4 and realizing accurate monitoring of leakage current.

[0031] The leakage current from the surge arrester body A1 is rectified into a DC signal by the rectifier bridge A3 and flows to the current-limiting resistor R4. After passing through the current-limiting resistor R4, most of the current flows through the shunt resistor R5, and a small portion flows through the compensation resistor R6 and the DC ammeter A4. The two currents merge and flow through the rectifier bridge A3 to the grounding module A5, and then through the grounding module A5 to the ground, forming a complete current loop (e.g., ...). Figure 2 The direction of the middle arrow indicates the actual direction of current flow.

[0032] Example 2

[0033] Reference Figures 1-2 This is the second embodiment of the present invention. Unlike the previous embodiment, this embodiment provides a current measurement circuit suitable for a range-nonlinear surge arrester monitor. It includes a high-power resistor R1 and a varistor RL1 forming a first-level protection circuit; a Zener diode D1 and a varistor RL2 forming a second-level protection circuit; and a Zener diode D2 and a current-limiting resistor R3 forming a third-level protection circuit.

[0034] Specifically, the primary protection circuit, the secondary protection circuit, and the tertiary protection circuit are all connected in parallel in the circuit, and the protection voltage of each level of protection circuit decreases sequentially, forming a "graded interception and layered protection" architecture. Its core function is to resist the large surge current generated by lightning strikes and prevent the DC ammeter A4 from being damaged by overcurrent and overvoltage, thus laying a safe foundation for current measurement.

[0035] In use, a multi-level protection circuit is formed by a primary protection circuit, a secondary protection circuit, and a tertiary protection circuit to ensure the stability of the voltage and current of the measurement circuit under extreme conditions such as lightning strikes, thereby improving the reliability of the surge arrester monitor. In conjunction with Example 1, it overcomes the problem of inaccurate measurement of leakage current of the surge arrester body A1 caused by temperature changes.

[0036] It is important to note that the constructions and arrangements of this application shown in several different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., changes in the size, dimensions, structure, shape and proportion of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc.), mounting arrangements, use of materials, color, orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of elements may be inverted or otherwise altered, and the nature or number or position of discrete elements may be changed or altered. Therefore, all such modifications are intended to be included within the scope of this utility model. The order or sequence of any process or method steps may be changed or rearranged according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure described herein that performs the function, and not only structural equivalents but also equivalent structures. Without departing from the scope of this invention, other substitutions, modifications, alterations, and omissions may be made in the design, operation, and arrangement of the exemplary embodiments. Therefore, this invention is not limited to the specific embodiments, but extends to various modifications that still fall within the scope of the appended claims.

[0037] Furthermore, in order to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features that are not relevant to the best mode of carrying out the present invention as currently considered, or those features that are not relevant to implementing the present invention) may be omitted.

[0038] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.

[0039] It should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of this utility model without departing from the spirit and scope of the technical solution of this utility model, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.

Claims

1. A current measurement circuit suitable for a range-nonlinear surge arrester monitor, characterized in that: include, Lightning arrester body (A1); A zinc oxide valve plate (A2) is connected in series with the main body (A1) of the surge arrester; A rectifier bridge (A3) connected in parallel to the zinc oxide valve plate (A2); A high-power resistor (R1) is provided between the rectifier bridge (A3) and the zinc oxide valve plate (A2); A current-limiting resistor (1) is connected in series on the rectifier bridge (A3); The current-limiting resistor (1) is connected in series with a shunt resistor (R5) and a compensation resistor (R6); A DC ammeter (A4) is connected in series with the compensation resistor (R6); The shunt resistor (R5) is connected in parallel to the series circuit formed by the compensation resistor (R6) and the DC ammeter (A4); The DC ammeter (A4) and the rectifier bridge (A3) are connected; The grounding module (A5) is connected to the zinc oxide valve plate (A2), and the rectifier bridge (A3) is connected to the grounding module (A5).

2. The current measurement circuit for a range-nonlinear surge arrester monitor as described in claim 1, characterized in that: It also includes, A filter capacitor (C1) is connected in parallel to the rectifier bridge (A3); A counter (A6) is connected in series with the current-limiting resistor (1); The positive terminal of the voltage regulator (2) is connected to the negative terminal of the negative side of the rectifier bridge (A3); A varistor (3) is connected in series with the high-power resistor (R1) and connected to the lower end of the zinc oxide valve plate (A2).

3. The current measurement circuit for a range-nonlinear surge arrester monitor as described in claim 2, characterized in that: The Zener diode (2) includes a Zener diode (D1) connected in parallel with the varistor (3) and a Zener diode (D2) connected in series with the current limiting resistor (1).

4. The current measurement circuit for a range-nonlinear surge arrester monitor as described in claim 3, characterized in that: The positive terminals of the counter (A6), Zener diode (D1), and Zener diode (D2) are connected to the negative terminal of the negative side of the rectifier bridge (A3).

5. The current measurement circuit for a range-nonlinear surge arrester monitor as described in claim 4, characterized in that: The varistor (3) includes a varistor (RL1) connected in series with a high-power resistor (R1) and a varistor (RL2) connected in parallel across a Zener diode (D2).

6. The current measurement circuit for a range-nonlinear surge arrester monitor as described in claim 5, characterized in that: The current-limiting resistor (1) includes a current-limiting resistor (R2), which is connected in series with the positive terminal of the filter capacitor (C1). Current limiting resistor 2 (R3) is connected in series with Zener diode (D2); The current limiting resistor three (R4) is connected in series with the current limiting resistor two (R3).

7. The current measurement circuit for a range-nonlinear surge arrester monitor as described in claim 6, characterized in that: The high-power resistor (R1) and varistor (RL1) constitute a primary protection circuit.

8. The current measurement circuit for a range-nonlinear surge arrester monitor as described in claim 7, characterized in that: The Zener diode (D1) and varistor (RL2) constitute a secondary protection circuit.

9. The current measurement circuit for a range-nonlinear surge arrester monitor as described in claim 8, characterized in that: The Zener diode (D2) and current-limiting resistor (R3) constitute a three-level protection circuit.

Images