阅读说明：本技术 一种提高电压传感器带负载能力的电路和电路元件定值方法 (Circuit for improving load capacity of voltage sensor and circuit element constant value method ) 是由 郭以贺 谭明义 郑计平 孔东波 于 2020-12-21 设计创作，主要内容包括：本发明提供了一种提高电压传感器带负载能力的电路和电路元件定值方法,涉及配电设备领域,包括：连接至电压传感器的分压组件输出端的补偿电抗器,以及与补偿电抗器并联的抑制谐振支路,抑制谐振支路用于抑制补偿电抗器与分压组件以及输出侧等效电容之间的谐振现象,其中,补偿电抗器的输入端连接分压组件的输出端,补偿电抗器的输出端连接电压传感器的输出端,抑制谐振支路包括串联的支路电容和支路电阻或者只包含支路电阻。适用于三相电压传感器和零序电压传感器,通过优化补偿电路的结构,兼顾了电压传感器在工频下的带载能力提高和高频谐波噪声的抑制。(The invention provides a circuit for improving the loading capacity of a voltage sensor and a circuit element constant value method, which relate to the field of distribution equipment and comprise the following steps: the voltage sensor comprises a compensation reactor connected to the output end of a voltage division component of the voltage sensor, and a resonance inhibiting branch circuit connected with the compensation reactor in parallel, wherein the resonance inhibiting branch circuit is used for inhibiting resonance between the compensation reactor and the voltage division component and between the compensation reactor and an output-side equivalent capacitor, the input end of the compensation reactor is connected with the output end of the voltage division component, the output end of the compensation reactor is connected with the output end of the voltage sensor, and the resonance inhibiting branch circuit comprises a branch capacitor and a branch resistor which are connected in series or only comprises a branch resistor. The voltage sensor is suitable for three-phase voltage sensors and zero-sequence voltage sensors, and the load capacity of the voltage sensor under power frequency is improved and high-frequency harmonic noise is inhibited by optimizing the structure of the compensation circuit.)

1. A circuit for increasing the on-load capability of a voltage sensor, comprising: the voltage sensor comprises a compensation reactor connected to the output end of a voltage division component of a voltage sensor, and a resonance inhibiting branch circuit connected with the compensation reactor in parallel, wherein the resonance inhibiting branch circuit is used for inhibiting the resonance phenomenon between the compensation reactor and the voltage division component and between equivalent capacitors of an output side, the equivalent capacitors of the output side are equivalent capacitors formed after a cable is connected with the voltage sensor, the input end of the compensation reactor is connected with the output end of the voltage division component, the output end of the compensation reactor is connected with the output end of the voltage sensor, and the resonance inhibiting branch circuit comprises a branch capacitor and a branch resistor which are connected in series or only comprises the branch resistor.

2. The circuit of claim 1, wherein the voltage divider component is a capacitive voltage divider or a resistive voltage divider.

3. The circuit for improving the load carrying capacity of a voltage sensor according to claim 1, wherein the compensation reactor is connected in series in the zero sequence voltage output circuit.

4. The circuit of claim 1, wherein the compensation reactor is an inductive element, and a magnetic core of the inductive element is made of amorphous material and/or nanocrystalline material.

5. The circuit for improving the loading capacity of a voltage sensor according to claim 1, wherein the voltage dividing component comprises a high-voltage capacitor and a low-voltage capacitor, the three-phase voltage provided by the three-phase circuit is grounded after passing through a series circuit formed by at least one high-voltage capacitor and at least one low-voltage capacitor, and the input end of the compensating reactor is connected between the high-voltage capacitor and the low-voltage capacitor.

6. A circuit element value setting method applied to the circuit for improving the loading capacity of the voltage sensor according to any one of claims 1 to 5, characterized by comprising the following steps:

obtaining the overall equivalent capacitance of the voltage sensor, denoted C_a；

Obtaining a power frequency value, which is recorded as f₀；

The inductance value L of the compensation reactor is determined by the following formula:

obtaining the capacitance value of the equivalent capacitance formed after the voltage sensor is connected with the cable and recording the capacitance value as C_L；

The capacitance value C of the branch circuit capacitor_bShould satisfy C_a<C_b<C_LWherein, C_bThe values of (A) include:

resonance frequency f between voltage division components of compensation reactor and voltage sensor and equivalent capacitance formed after voltage sensor is connected with cable₁Determined by the following equation:

the value of the resistance R of the branch resistor is as follows: 2 pi · f₀·L≤R≤2π·f₁L, R values close to 2 π f₀L influences the improvement of the load capacity of the voltage sensor, and the R value is close to 2 pi · f₁L affects the suppression of the resonant branch pair f₁Suppression of resonance at frequency.

Technical Field

The invention relates to the field of power distribution equipment, in particular to a circuit for improving the loading capacity of a voltage sensor and a circuit element constant value method.

Background

The primary and secondary fusion of the power distribution equipment is an important way and means for realizing the on-site processing of faults, and is a necessary route for standardization and miniaturization of the power distribution equipment, device integration and operation and maintenance intellectualization. The three-phase voltage sensor and the zero-sequence voltage sensor are important components of the primary and secondary fusion equipment. At present, a voltage sensor mainly has two typical structures of an impedance voltage division type and a CVT (constant voltage transformer), while the voltage sensor based on the capacitance voltage division type is most widely applied, and the principle of the voltage sensor is that a high-voltage capacitance value and a low-voltage capacitance value are designed according to a certain proportion, and rated output voltage is obtained on a low-voltage capacitor to be used by a subsequent circuit. The main problems with this type of circuit are: when the capacitance value of the high-voltage capacitor is larger, the capacitive current flowing through the voltage sensor is larger, so that the normal operation of a power line is influenced, and the correct judgment of the relay protection device is influenced; when the capacitance value of the high-voltage capacitor is small, the carrying capacity of the voltage sensor is poor, and the precision of the sensor is affected by a connecting cable between the sensor and the measurement and control device and the input impedance of the measurement and control device. In summary, the main disadvantages of the prior art solutions are: from the point of load capacity, the larger the capacitance value of the internal capacitance of the sensor is, the better the capacitance value is, but at the moment, the capacitive current on the line becomes larger, the reactive power on the sensor becomes larger, and the safety and the stability of the operation of the power distribution network are not facilitated, namely, a contradiction exists between the load capacity and the power consumption of the sensor.

Disclosure of Invention

The invention aims to at least solve one of the technical problems in the prior art or the related technology, provides a circuit for improving the loading capacity of a voltage sensor and a circuit element constant value method, is suitable for a three-phase voltage sensor and a zero sequence voltage sensor, and gives consideration to the improvement of the loading capacity and the suppression of high-frequency harmonic noise under power frequency through optimizing the structure of a compensation circuit.

A first aspect of the present invention provides a circuit for improving the load carrying capacity of a voltage sensor, comprising: the compensation reactor that is connected to voltage sensor's partial pressure subassembly output to and the resonance branch road of restraineing parallelly connected with the compensation reactor, restrain the resonance branch road and be used for restraining the resonance phenomenon between compensation reactor and partial pressure subassembly and the output side equivalent capacitance, the output side equivalent capacitance is the equivalent capacitance that forms behind the voltage sensor connection cable, wherein, the output of partial pressure subassembly is connected to the input of compensation reactor, voltage sensor's output is connected to the output of compensation reactor, restrain the resonance branch road including the branch road electric capacity and the branch road resistance of establishing ties or only contain branch road resistance.

In the technical scheme, an equivalent capacitor is formed after the voltage sensor and measurement and control devices such as an FTU (feeder terminal unit) are connected with a cable, wherein the FTU is a switch monitoring device arranged beside a feeder switch (such as a circuit breaker, a load switch and a section switch). The resonance phenomenon can be generated between the compensation reactor and the voltage division component and between the compensation reactor and the equivalent capacitor, so that a larger harmonic voltage is formed on an input resistor of the measurement and control device to influence the measurement precision, and the harmonic voltage formed on the output side of the voltage sensor can be inhibited by the inhibition resonance branch circuit, so that the voltage sensor has a relatively flat output characteristic.

According to the circuit for improving the loading capacity of the voltage sensor provided by the invention, the voltage dividing component is preferably a capacitive voltage divider or a resistive voltage divider.

According to the circuit for improving the loading capacity of the voltage sensor, provided by the invention, the compensation reactor is preferably connected in series in the zero sequence/phase sequence voltage output circuit.

According to the circuit for improving the loading capacity of the voltage sensor, provided by the invention, preferably, the compensation reactor is an inductance element, and the magnetic core of the inductance element is made of an amorphous material and/or a nanocrystalline material.

According to the circuit for improving the loading capacity of the voltage sensor, preferably, the voltage dividing assembly comprises a high-voltage capacitor and a low-voltage capacitor, three-phase voltages provided by the three-phase circuit are grounded after passing through a series circuit formed by at least one high-voltage capacitor and at least one low-voltage capacitor respectively, and the input end of the compensating reactor is connected between the high-voltage capacitor and the low-voltage capacitor.

The second aspect of the present invention provides a circuit element value setting method, which is applied to the circuit provided in any of the above technical solutions to improve the loaded capacity of the voltage sensor, and the method includes: obtaining the overall equivalent capacitance of the voltage sensor, denoted C_a；

Obtaining a power frequency value, which is recorded as f₀；

The inductance value L of the compensation reactor is determined by the following formula:

obtaining the capacitance value of the equivalent capacitance formed after the voltage sensor is connected with the cable and recording the capacitance value as C_L；

The capacitance value C of the branch circuit capacitor_bShould satisfy C_a<C_b<C_LWherein, in the step (A),is C_bA value taking situation of (1);

resonance frequency f between voltage division components of compensation reactor and voltage sensor and equivalent capacitance formed after voltage sensor is connected with cable₁Determined by the following equation:

the value of the resistance R of the branch resistor is as follows: 2 pi · f₀·L≤R≤2π·f₁L, R values close to 2 π f₀L influences the improvement of the load capacity of the voltage sensor, and the R value is close to 2 pi · f₁L affects the suppression of the resonant branch pair f₁Suppression of resonance at frequency.

The beneficial effects obtained by the invention at least comprise: based on compensating reactor L, branch road electric capacity C, branch road resistance R constitute compensating circuit, have improved the load capacity of taking of electric capacity partial pressure formula sensor through the reasonable selection to L, C, R three numerical value, under the condition of same load, only need use the more little high-voltage capacitance of appearance value and low-voltage capacitance, the cost is reduced and the volume, in addition, this compensating circuit has still realized the comparatively flat amplitude-frequency characteristic in 50Hz and the higher harmonic scope, has avoided the interference of higher harmonic.

Drawings

FIG. 1 shows a schematic diagram of a circuit for increasing the load carrying capability of a voltage sensor in accordance with one embodiment of the present invention.

FIG. 2 shows a schematic diagram of a circuit for increasing the load carrying capability of a voltage sensor in accordance with yet another embodiment of the present invention.

FIG. 3 shows a schematic diagram of the amplitude-frequency characteristics of a sensor according to one embodiment of the invention.

Fig. 4 shows a schematic diagram of the amplitude-frequency characteristic after adding the suppressed resonance branch according to an embodiment of the present invention.

Fig. 5 shows a prior art phase voltage sensor circuit diagram.

Fig. 6 shows a circuit diagram of a zero sequence voltage sensor in the prior art.

Detailed Description

In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified. The terms "mounted," "connected," and "coupled" are to be construed broadly and may, for example, be fixedly coupled, detachably coupled, or integrally coupled; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

In the prior art, as shown in fig. 5 (phase voltage sensor) and fig. 6 (zero sequence voltage sensor), a/B/C is 10kV line voltage, a/B/C is three-phase voltage sensor output, and actually, three same circuits respectively output. d is the output of the zero sequence voltage sensor. C₁Represents a high-voltage capacitor, C₂And the low-voltage capacitor is represented, and in practice, the high-voltage and low-voltage capacitors may respectively consist of a plurality of capacitors connected in series and in parallel. C_LThe equivalent capacitance of the cable for connecting the representative sensor and the measuring and controlling devices such as FTU and the like can reach an actual measurement capacitance value of more than 1nF, R_LThe input resistance of the corresponding port of the measurement and control device is generally a few M omega. In carrying out the present invention, applicants have discovered that: take zero sequence voltage sensor as an example, without considering C_LAnd R_LTime, sensor output U_dnAnd an input voltage U_in(actually 10/√ 3kV) is given by:consider C_LAnd R_LWhen the temperature of the water is higher than the set temperature,C_Land R_LThe existence of (2) leads the output voltage to have smaller amplitude and advanced phase, which reflects the result that C is caused₁And C₂Is small in value (C)₁With a typical value of 200-600pF, C₂At 500-1600nF), the internal resistance of the sensor is large and the belt load capacity is not strong.

As shown in fig. 1, the disclosed circuit 100 for improving the loading capability of a voltage sensor includes: the voltage sensor comprises a compensation reactor 101 connected to the output end of a voltage division component 200 of a voltage sensor, and a resonance inhibiting branch circuit connected with the compensation reactor 101 in parallel, wherein the resonance inhibiting branch circuit is used for inhibiting resonance phenomena between the compensation reactor 101 and the voltage division component 200 and between the compensation reactor 101 and an output-side equivalent capacitor 300, the output-side equivalent capacitor 300 is an equivalent capacitor formed after a voltage sensor is connected with a cable, the input end of the compensation reactor 101 is connected with the output end of the voltage division component 200, the output end of the compensation reactor 101 is connected with the output end of the voltage sensor, and the resonance inhibiting branch circuit comprises a branch capacitor 102 and a branch resistor 103 which are connected in.

According to the circuit 100 for improving the loading capability of the voltage sensor disclosed in the above embodiment, the voltage dividing component 200 is preferably a capacitive voltage divider or a resistive voltage divider.

According to the circuit 100 for improving the loading capacity of the voltage sensor disclosed in the above embodiment, the compensation reactor 101 is preferably connected in series in the zero sequence voltage output circuit or the phase sequence voltage output circuit.

According to the circuit 100 for improving the loading capability of the voltage sensor disclosed in the above embodiment, preferably, the compensation reactor 101 is an inductance element, and the magnetic core of the inductance element is made of an amorphous material and/or a nanocrystalline material.

According to the circuit 100 for improving the loading capacity of the voltage sensor disclosed in the above embodiment, preferably, the voltage dividing assembly 200 includes a high-voltage capacitor and a low-voltage capacitor, the three-phase voltages provided by the three-phase circuit are grounded after passing through a series circuit formed by at least one high-voltage capacitor 201 and at least one low-voltage capacitor 202, and the input end of the compensation reactor 101 is connected between the high-voltage capacitor 201 and the low-voltage capacitor 202.

According to another embodiment of the present invention, there is provided a circuit element setting method applied to the circuit 100 for improving the loading capability of the voltage sensor provided in any of the above embodiments, the method including:

obtaining the overall equivalent capacitance of the voltage sensor, denoted C_a；

Obtaining a power frequency value, which is recorded as f₀；

The inductance value L of the compensation reactor is determined by the following formula:

obtaining the capacitance value of the equivalent capacitance formed after the voltage sensor is connected with the cable and recording as C_L；

The capacitance value C of the branch circuit capacitor_bShould satisfy C_a<C_b<C_LWherein, in the step (A),is C_bA value taking situation of (1);

resonance frequency f between voltage division components of compensation reactor and voltage sensor and equivalent capacitance formed after voltage sensor is connected with cable₁Determined by the following equation:

the value of the resistance R of the branch resistor is as follows: 2 pi · f₀·L≤R≤2π·f₁L, R values close to 2 π f₀L influences the improvement of the load capacity of the voltage sensor, and the R value is close to 2 pi · f₁L affects the suppression of the resonant branch pair f₁Suppression of resonance at frequency.

According to another embodiment of the present invention, as shown in fig. 2, R1 is an internal equivalent resistance of the inductor L, and the value of the inductor L is as follows: integral equivalent capacitance 3C with the sensor₁+C₂At power frequency f₀A series resonance is formed around 50Hz,such as 3C₁+C₂At a frequency of 600nF,in actual design, the error can be +/-20%, and amorphous/nanocrystalline materials are generally used as magnetic cores of inductors. Considering the loss of the magnetic core, the internal resistance R1 is generally below several hundred Ω. The internal resistance of the sensor at 50Hz can be reduced by the resonance, and the load capacity is improved, namely, the allowable R is added after L is added_LThe value of (A) is smaller, and considering that the actual inductance L value can be changed by more than 20% at different temperatures in the range of-40 ℃ to 70 ℃, R is allowed to be_LMay be reduced to below 1/3 without the addition of L.

When the sensor is connected to the connecting cable, L and C are connected_LAnd 3C₁+C₂Forming a new resonance frequency f₁，

When C is present_L＝1nF，3C₁+C₂At 600nF, f₁1225Hz, which is close to the 20 th harmonic of the power frequency of 50Hz, will be applied to the load R_LThe large harmonic voltage is formed, and the measurement precision is influenced. For this purpose, a capacitor C is connected in parallel across the inductor L₃And R₂Forming a new branch. The branch circuit has the function of changing the original state f₁The resonance phenomenon at the frequency gives the sensor a relatively flat output characteristic.

C₃Should have a capacitance value of 3C₁+C₂And C_LIts capacitive reactance at 50Hz is much greater than the inductive reactance of L, and the capacitive reactance at 20 th harmonic, i.e. 1000Hz, is much less than the inductive reactance of L, a possible value beingWhen C is present_L＝1nF，3C₁+C₂At 600nF, C₃Is in the range of about 10nF to about 30 nF.

In the compensating circuit C₃And L has a resonance frequency f₂,f₂The value of (A) is between 50Hz and 1000 Hz.

R₂Should have a value of 2 pi · f₀L and 2 π f₁·L，R₂Too small of a level will affect the belt load capacity lift, R₂Too large will not inhibit f₁The effect of resonance at frequency.

When considering the simplicity of circuit implementation, only R can be reserved₂Omission of C₃The accuracy of the sensor at 50Hz is slightly affected. The amplitude-frequency characteristics (normalized) of the sensor are shown in fig. 3 and 4: FIG. 3 is a graph showing the amplitude-frequency characteristic when L is added only; fig. 4 shows the amplitude-frequency characteristic after the resonance suppression branch is added.

In conclusion, the invention provides the L, C, R structure-based compensation circuit, the load capacity of the capacitive voltage division type sensor is improved through reasonable selection of the numerical values of the three, under the condition of the same load, only high-voltage and low-voltage capacitors with smaller capacitance values are needed, the cost and the volume are reduced, in addition, the compensation circuit realizes the relatively flat amplitude-frequency characteristic in the range of 50Hz and higher harmonics, and the interference of higher harmonics is avoided. The circuit for improving the loading capacity of the voltage sensor and the circuit element constant value method are suitable for a three-phase voltage sensor and a zero sequence voltage sensor, and the circuit with R or C + R is introduced to realize the flattening of amplitude-frequency characteristics by considering the capacitance of a cable or a load, namely the improvement of the loading capacity under power frequency and the suppression of high-frequency harmonic noise are considered.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.