Capacitive voltage division type voltage transformer suitable for broadband voltage measurement and measurement method

Abstract

The invention discloses a capacitive voltage division type voltage transformer suitable for broadband voltage measurement and a measurement method, and relates to the technical field of power grid broadband voltage measurement, the transformer mainly comprises a high-voltage capacitor and a low-voltage capacitor which are connected in series, a neutral point measurement coil and an impedance transformer. The measurement method relates to calculation in multiple aspects such as capacitance voltage division, inductance coil induction and circuit impedance matching, and accurate voltage measurement can be realized in a broadband range of 10Hz-1MHz. Compared with the prior art, the measuring precision is improved, the dynamic response characteristic and the broadband measuring capacity are good, the performance is stable and reliable, the structure is simple, and installation and maintenance are easy.

Description

Technical Field

[0001] The present invention relates to the technical field of broadband voltage measurement of power grids, and in particular to a capacitive voltage divider type voltage transformer suitable for broadband voltage measurement and a measurement method. Background Art

[0002] In modern power systems, voltage transformers, as important measuring equipment, play a key role in ensuring the safe and stable operation of the system. Traditional voltage transformers have certain limitations in some aspects.

[0003] On the one hand, due to the existence of detuning reactors and compensating reactors, although their design purpose is to reduce harmonics and frequency distortion, they limit the frequency response of the sensor. Generally, the measurement bandwidth of such sensors is below 10kHz, which is difficult to meet some application scenarios that require wide-band response, such as traveling wave positioning and high-order harmonic analysis. With the increasing demand for high-frequency signal measurement in power systems, the shortcomings of traditional transformers in this regard are becoming more and more obvious. On the other hand, the large capacitance of high-voltage capacitors makes the overall dynamic response characteristics of the sensor poor. When the voltage changes rapidly, the sensor cannot respond in time, which greatly affects the accuracy and timeliness of the measurement. At the same time, the introduction of detuning reactors and compensating reactors not only increases the complexity of the design, but also requires precise tuning and maintenance, thereby increasing the cost of the system. Moreover, the performance of reactors and capacitors is easily affected by temperature and other environmental factors, resulting in reduced measurement accuracy and stability. Especially in high-voltage environments, temperature changes may cause changes in capacitance and reactance values, which in turn have an adverse effect on the measurement results of the sensor.

[0004] In view of this, with the continuous development of power systems and the increasing requirements for measurement accuracy, it is particularly urgent to develop a capacitive voltage transformer with a wide-band voltage measurement having a measurement frequency band of 10Hz to 1MHz and good dynamic response characteristics. Summary of the invention

[0005] The purpose of the present invention is to provide a capacitive voltage divider type voltage transformer and a measurement method suitable for wide-band voltage measurement, by reducing the capacitance of the high-voltage capacitor, optimizing the voltage divider ratio, and improving the dynamic response characteristics; by adding a neutral point measurement coil, stable measurement of high-frequency signals is achieved; by adding an electronic impedance converter, the secondary input impedance is stabilized at more than 10MΩ to ensure the accurate transmission of wide-band voltage signals.

[0006] To achieve the above object, the present invention provides the following technical solution: a capacitor voltage divider type voltage transformer suitable for broadband voltage measurement, comprising a main circuit, characterized in that the main circuit is connected in series with a high-voltage capacitor and a low-voltage capacitor, the high-voltage capacitor C 1The value should ensure that it can withstand high voltages and maintain appropriate capacitive reactance at the highest operating frequency. The capacitance of the low-voltage capacitor C 2 Should be much larger than C 1 To ensure effective voltage division. A neutral point measurement coil is installed at the neutral point below the low voltage capacitor, and an impedance converter is connected in parallel between the low voltage capacitor and the front and rear end lines of the neutral point measurement coil, and the impedance converter is connected in parallel to an ammeter.

[0007] It is characterized in that the capacitance of the high voltage capacitor is C 1 , the high voltage capacitor value C 1 The calculation formula is:

[0008]

[0009] Where f is the frequency, X C1 is the high voltage capacitor C 1 The required capacitive reactance is to ensure that the capacitor has a sufficiently high impedance at the highest operating frequency, and that the voltage signal can be effectively transmitted without excessive attenuation at high frequencies, and to solve the problem of large capacitance of high-voltage capacitors in traditional capacitor-divider voltage transformers.

[0010] It is characterized in that the capacitance of the low-voltage capacitor is C 2 , the capacitance of the low voltage capacitor C 2 Should be much larger than C 1 To ensure effective voltage division. The low voltage capacitor value C 2 C is the high voltage capacitor value 1 10 times of that.

[0011] The invention is characterized in that the high voltage capacitor and the low voltage capacitor use ceramic capacitors. These capacitors have low equivalent series resistance (ESR) and low parasitic inductance and are suitable for high frequency applications.

[0012] The invention is characterized in that the neutral point measurement coil adopts an air-core coil and adopts a silver-plated copper wire or a tin-plated copper wire to reduce magnetic loss and parasitic effects. The neutral point measurement coil L should have a high inductance to ensure that it does not affect the measurement at low frequency and provides effective measurement at high frequency.

[0013] It is characterized in that the calculation formula of the neutral point measurement coil inductance value L is as follows:

[0014]

[0015] Where f is C 2 The resonant frequency resonates near the highest frequency, C 2 is the low voltage capacitor value;

[0016] The impedance converter includes an operational amplifier, the operational amplifier model is OPA656, and the impedance converter is a voltage follower function based on a simple operational amplifier OPA656 and a plurality of resistors. The operational amplifier is connected to a dual-unit power supply, and the positive and negative ends of the dual-unit power supply are respectively between +5V and -5V, +5V and -5V, to ensure the normal operation of the OPA656 operational amplifier. The OPA656 operates in a dual power supply mode, providing a larger signal swing, and is suitable for broadband applications.

[0017] Two 10μF capacitors are set at the input end of the power bypass of the operational amplifier. The two 10μF capacitors at the input end are used to stabilize the positive and negative power supplies of OPA659 to prevent power supply fluctuations from affecting the performance of the amplifier and maintain the low-frequency stability of the power supply to ensure that the operating voltage of the operational amplifier is not affected by transient interference.

[0018] Two 0.1μF capacitors are set at the output end to filter out high-frequency noise that may exist on the power line and prevent such noise from being coupled to the power pin of the operational amplifier through the power line, thereby avoiding affecting the performance of the operational amplifier. An output matching resistor is set between the output end of the operational amplifier and the output end of the circuit, and the output matching resistor is 50Ω. 50Ω is a standard impedance commonly used in communication systems and radio frequency circuits. The resistor is connected between the output end of the OPA659 and the output end of the circuit, and is mainly used for output impedance matching to ensure that the reflection of the signal on the transmission line or load is minimized, thereby reducing signal distortion and improving signal integrity. The impedance converter is configured in the unit gain mode in the circuit, and its main function is to convert a high-impedance signal source, that is, a voltage signal generated by a capacitive voltage divider, into a low-impedance output signal. This high input impedance and low output impedance feature enables the impedance converter to effectively avoid the load effect of the signal source, thereby maintaining the integrity and accuracy of the measurement signal and improving the measurement accuracy.

[0019] The circuit design of the impedance transformer is optimized for broadband measurement. Since the impedance transformer can stably process signals in the broadband range of 10Hz to 1MHz, it can effectively transmit high-frequency components, ensuring that the voltage transformer can accurately measure broadband voltage signals including high-order harmonics and traveling wave signals.

[0020] It is characterized in that the operational amplifier input resistance is 10 13 Ω.

[0021] A method for measuring a capacitor voltage transformer suitable for wide-band voltage measurement, in which the measurement of voltage signals involves calculation problems in multiple aspects such as capacitor voltage division, inductor coil induction, circuit impedance matching, etc. The method is characterized in that it comprises the following steps:

[0022] S1 capacitor divides the voltage. In the capacitor voltage divider, the high voltage signal V in Through the high voltage capacitor C 1 And low voltage capacitor C 2 Realize voltage division and get output voltage V out , the voltage V out The calculation formula is:

[0023]

[0024] Among them, V in Indicates high voltage signal, X C1 and X C2 They are high voltage capacitors C 1 And low voltage capacitor C 2 The capacitive reactance is calculated as:

[0025]

[0026] Where f is the frequency, C 1 is the high voltage capacitor value, C 2 is the low voltage capacitor value;

[0027] S2 calculates the voltage divider ratio and converts the capacitive reactance X obtained in the previous step into C1 , X C2 Substituting into the voltage V out Calculate the formula to get the voltage divider ratio formula:

[0028]

[0029] Calculation of the induced voltage of the S3 inductor. In the design of the wide-band capacitor voltage transformer, the neutral point measurement coil L is connected to the inductive high-voltage capacitor C. 1 The current change in the induced voltage V L This induced voltage may affect the low-voltage side output voltage V out If the induced voltage is too large, it may introduce measurement errors and cause output signal distortion; and under high-frequency conditions, the induced voltage of the neutral point measurement coil may cause resonance or resonance in the circuit. Therefore, calculating the magnitude of the induced voltage helps to evaluate the potential impact of the inductance effect on the measurement accuracy, and can also help predict the frequency and impact of these phenomena, so as to optimize the design, avoid unnecessary resonance or resonance, and ensure the stability and reliability of the transformer.

[0030] The neutral point measurement coil L is connected to the inductive high voltage capacitor C 1 The current change in the induced voltage V L , and its calculation formula is:

[0031]

[0032] Among them, L is the inductance of the coil, I is the current flowing through the coil, t is the time the current flows through the coil, and the current I flowing through the coil is the current I flowing through the low-voltage capacitor C1 , the formula is:

[0033]

[0034] Therefore, the induced voltage V on the coil L The calculation formula can be expressed as:

[0035]

[0036] Among them, V in Indicates high voltage signal, C 2 represents the capacitance of the low-voltage capacitor, L is the inductance of the coil, and t is the time for the current to flow through the coil. This induced voltage will affect the output voltage V after voltage division. out , the influence of this factor needs to be considered in practical applications.

[0037] The output voltage of the S4 impedance converter is calculated by first calculating the gain A of the operational amplifier. V , the gain of the OPA656 operational amplifier is: A V =1;

[0038] Calculate the output voltage V of the impedance converter out' , the V out' The calculation formula is:

[0039]

[0040] Where V out' The output voltage of the impedance converter depends on the capacitor voltage divider ratio and the operational amplifier A. V gain.

[0041] S5 calculates the total measured voltage, combining the above V out' Calculation formula and V L The total measured voltage is calculated by the formula V total :

[0042]

[0043] Among them, V out' represents the output voltage of the impedance converter, A V represents the gain of the operational amplifier, V in Indicates high voltage signal, C 1 With C 2represents the capacitance of the high-voltage capacitor and the low-voltage capacitor, L is the inductance of the coil, and t is the time for the current to flow through the coil. The formula comprehensively considers the effects of capacitor voltage division and induced voltage, and is a complete expression of the voltage signal measurement of the wide-band capacitor voltage division type voltage transformer. It describes in detail the voltage signal measurement process of the wide-band capacitor voltage division type voltage transformer. The design and performance of the transformer can be accurately calculated and analyzed to ensure accurate voltage measurement within the wide frequency range of 10Hz to 1MHz.

[0044] The operational amplifier used in the impedance converter does not use a feedback resistor to maintain a high input impedance.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] By properly selecting the capacitance of high-voltage and low-voltage capacitors and accurately calculating the capacitive reactance of high-voltage capacitors at different frequencies, stable voltage division is ensured over a wide frequency range. In particular, the high-voltage capacitor can maintain a suitable capacitive reactance at the highest operating frequency, effectively avoiding excessive signal attenuation and improving measurement accuracy. The neutral point measurement coil uses an air-core coil and silver-plated or tin-plated copper wire to reduce magnetic loss and parasitic effects. Accurately calculating the coil inductance value allows it to work effectively at both low and high frequencies. Accurate measurement of the induced voltage helps evaluate the impact of the inductance effect on the measurement accuracy, thereby optimizing the design and further improving the overall measurement accuracy.

[0047] The impedance converter based on the OPA656 operational amplifier can stably process signals in a wide frequency range (10Hz to 1MHz). The high input impedance is maintained without using feedback resistors. Through the optimization design of dual-unit power supply, setting appropriate capacitors to stabilize the power supply, and output matching resistors, the high impedance signal source is converted into a low impedance output signal, avoiding the load effect of the signal source and ensuring the integrity and accuracy of the measurement signal.

[0048] It can accurately measure broadband voltage signals including high-order harmonics and traveling wave signals, meeting the needs of modern power systems for monitoring signals of different frequencies. It can provide reliable measurement results regardless of whether it is in the case of conventional power frequency or high-frequency interference or special signals, and its applicable range covers a wide range of frequency bands from low frequency to high frequency.

[0049] Ceramic capacitors, air-core coils and high-performance operational amplifiers are used. These components have the advantages of low equivalent series resistance (ESR) and low parasitic inductance, and are suitable for high-frequency applications. At the same time, the components have high stability and reliability, and can maintain good performance in different working environments, ensuring the long-term stable operation of the voltage transformer.

[0050] The circuit design is fully optimized for broadband measurement, taking into account capacitor voltage division, inductor induction, impedance matching, etc. The synergy between the components makes the entire circuit have good performance stability within a wide frequency range, can effectively resist the influence of external interference and environmental changes, and ensure the reliability of the measurement results.

[0051] It consists of high-voltage capacitors, low-voltage capacitors, neutral point measurement coils and impedance transformers, and has a relatively simple structure. During installation, it does not require complicated operations or special tools, and can be quickly and easily connected to the power system or measurement equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A schematic diagram of the connection principle of a capacitor voltage divider type voltage transformer suitable for wide-band voltage measurement according to the present invention;

[0053] Figure 2 This is a circuit connection principle diagram of a capacitor voltage-dividing type voltage transformer impedance converter suitable for wide-band voltage measurement according to the present invention; DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present invention will be fully described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0055] like Figure 1-2 As shown, a capacitor voltage-dividing voltage transformer suitable for wide-band voltage measurement includes a main circuit, characterized in that the main circuit is connected in series with a high-voltage capacitor and a low-voltage capacitor in sequence, a neutral point measurement coil is installed and wound at the neutral point below the low-voltage capacitor, an impedance converter is connected in parallel before and after the low-voltage capacitor and the neutral point measurement coil, and the impedance converter is connected in parallel with an ammeter.

[0056] The capacitance of the high voltage capacitor is C 1 , the high voltage capacitor value C 1 The calculation formula is:

[0057]

[0058] Where f is the frequency, X C1 is the high voltage capacitor C 1 The required capacitive reactance.

[0059] The capacitance of the low voltage capacitor is C 2 , the low voltage capacitor value C 2 C is the high voltage capacitor value 1 10 times of that.

[0060] The high voltage capacitor and the low voltage capacitor use ceramic capacitors.

[0061] The neutral point measurement coil adopts an air-core coil and adopts a silver-plated copper wire or a tin-plated copper wire.

[0062] The calculation formula of the neutral point measurement coil inductance value L is as follows:

[0063]

[0064] Where f is C 2 The resonant frequency resonates near the highest frequency, C 2 is the low voltage capacitor value.

[0065] The impedance converter includes an operational amplifier, the operational amplifier model is OPA656, the operational amplifier is connected to a dual-unit power supply, the positive and negative ends of the dual-unit power supply are respectively between +5V and -5V, two 10μF capacitors are set at the input end of the power bypass of the operational amplifier, and two 0.1μF capacitors are set at the output end. An output matching resistor is set between the output end of the operational amplifier and the output end of the circuit, and the output matching resistor is 50Ω.

[0066] The operational amplifier input resistance is 10 13 Ω.

[0067] A capacitive voltage divider type voltage transformer measurement method suitable for wide-band voltage measurement, characterized in that it comprises the following steps:

[0068] S1 capacitor divides the voltage. In the capacitor voltage divider, the high voltage signal V in Through the high voltage capacitor C 1 And low voltage capacitor C 2 Realize voltage division and get output voltage V out , the voltage V out The calculation formula is:

[0069]

[0070] Among them, V in Indicates high voltage signal, X C1 and X C2 They are high voltage capacitors C 1 And low voltage capacitor C 2 The capacitive reactance is calculated as:

[0071]

[0072] Where f is the frequency, C 1 is the high voltage capacitor value, C 2 is the low voltage capacitor value;

[0073] S2 calculates the voltage divider ratio and converts the capacitive reactance X obtained in the previous step into C1 , XC2 Substituting into the voltage V out Calculate the formula to get the voltage divider ratio formula:

[0074]

[0075] The induced voltage calculation of S3 inductor coil, the neutral point measurement coil L through the inductive high voltage capacitor C 1 The current change in the induced voltage V L , and its calculation formula is:

[0076]

[0077] Among them, L is the inductance of the coil, I is the current flowing through the coil, t is the time the current flows through the coil, and the current I flowing through the coil is the current I flowing through the low-voltage capacitor C1 , the formula is:

[0078]

[0079] Therefore, the induced voltage V on the coil L The calculation formula can be expressed as:

[0080]

[0081] Among them, V in Indicates high voltage signal, C 2 It represents the capacitance of the low-voltage capacitor, L is the inductance of the coil, and t is the time that the current flows through the coil;

[0082] The output voltage of the S4 impedance converter is calculated by first calculating the gain A of the operational amplifier. V , the gain of the OPA656 operational amplifier is: A V =1;

[0083] Calculate the output voltage V of the impedance converter out' , the V out' The calculation formula is:

[0084]

[0085] Where V out' The output voltage of the impedance converter depends on the capacitor voltage divider ratio and the operational amplifier A. V Gain of

[0086] S5 calculates the total measured voltage, combining the above V out' Calculation formula and V L The total measured voltage is calculated by the formula V total :

[0087]

[0088] Among them, V out' represents the output voltage of the impedance converter, A V represents the gain of the operational amplifier, V in Indicates high voltage signal, C 1 With C 2 It represents the capacitance of high-voltage capacitor and low-voltage capacitor, L is the inductance of the coil, and t is the time that current flows through the coil.

[0089] The operational amplifier used in the impedance converter does not use a feedback resistor to maintain a high input impedance.

[0090] The specific method is to first select suitable ceramic capacitors as high-voltage capacitors and low-voltage capacitors according to the voltage level and frequency range to be measured. Make sure that the high-voltage capacitor can withstand high voltage while maintaining appropriate capacitive reactance at the highest operating frequency. The capacitance of the low-voltage capacitor should be much larger than that of the high-voltage capacitor, usually 10 times the capacitance of the high-voltage capacitor. When calculating the capacitance of the high-voltage capacitor, use the formula Where f is the frequency, X C1 is the high voltage capacitor C 1 The required capacitive reactance is determined to ensure that the capacitor has a sufficiently high impedance at the highest operating frequency and that the voltage signal can be effectively transmitted without excessive attenuation at high frequencies. An air-core coil is used as the neutral point measurement coil, and silver-plated copper wire or tin-plated copper wire is selected to reduce magnetic loss and parasitic effects. According to the design requirements, the inductance value of the neutral point measurement coil is determined. The inductance value calculation formula is L = Where f is C 2 The resonant frequency resonates near the highest frequency, C 2 is the capacitance of the low-voltage capacitor. Ensure that the coil has a high inductance so that it does not affect the measurement at low frequencies and provides effective measurement at high frequencies. The operational amplifier model OPA656 is selected as the core component of the impedance converter. This operational amplifier has the characteristics suitable for broadband applications and can stably process signals within a wide frequency range of 10Hz to 1MHz. Prepare a dual-unit power supply so that its positive and negative terminals are between +5V and -5V respectively to ensure the normal operation of the OPA656 operational amplifier. Connect the high-voltage capacitor and the low-voltage capacitor in series to the main line in turn. Wind the neutral point measurement coil at the neutral point below the low-voltage capacitor. Connect the impedance converter in parallel to the low-voltage capacitor and the front and back of the neutral point measurement coil. According to the pin connection requirements of the operational amplifier, correctly connect the dual-unit power supply, input resistor, output matching resistor and capacitor.

[0091] Then the total measured voltage is calculated according to the high voltage signal. In the capacitive voltage divider, the high voltage signal V in Through the high voltage capacitor C 1 And low voltage capacitor C 2Realize voltage division and get output voltage V out , the voltage V out The calculation formula is:

[0092]

[0093] Among them, V in Indicates high voltage signal, X C1 and X C2 They are high voltage capacitors C 1 And low voltage capacitor C 2 The capacitive reactance is calculated as:

[0094]

[0095] Where f is the frequency, C 1 is the high voltage capacitor value, C 2 is the low voltage capacitor value;

[0096] Calculate the voltage divider ratio and convert the capacitive reactance X obtained in the previous step into C1 , X C2 Substituting into the voltage V out Calculate the formula to get the voltage divider ratio formula:

[0097]

[0098] Calculate the induced voltage of the inductor coil, the neutral point measurement coil L through the inductive high voltage capacitor C 1 The current change in the induced voltage V L , and its calculation formula is:

[0099]

[0100] Among them, L is the inductance of the coil, I is the current flowing through the coil, t is the time the current flows through the coil, and the current I flowing through the coil is the current I flowing through the low-voltage capacitor C1 , the formula is:

[0101]

[0102] Therefore, the induced voltage V on the coil L The calculation formula can be expressed as:

[0103]

[0104] Among them, V in Indicates high voltage signal, C 2 It represents the capacitance of the low-voltage capacitor, L is the inductance of the coil, and t is the time that the current flows through the coil;

[0105] To calculate the output voltage of the impedance converter, first calculate the gain A of the operational amplifier.V , the gain of the OPA656 operational amplifier is: A V =1;

[0106] Calculate the output voltage V of the impedance converter out' , the V out' The calculation formula is:

[0107]

[0108] Where V out' The output voltage of the impedance converter depends on the capacitor voltage divider ratio and the operational amplifier A. V Gain of

[0109] Calculate the total measured voltage, combining the above V out' Calculation formula and V L The total measured voltage is calculated by the formula V total :

[0110]

[0111] Among them, V out' represents the output voltage of the impedance converter, A V represents the gain of the operational amplifier, V in Indicates high voltage signal, C 1 With C 2 It represents the capacitance of high-voltage capacitor and low-voltage capacitor, L is the inductance of the coil, and t is the time that current flows through the coil.

[0112] The influence of capacitor voltage division and induced voltage is comprehensively considered through the formula, and the design and performance of the transformer are accurately calculated and analyzed to ensure accurate voltage measurement within the wide frequency band of 10Hz to 1MHz.

Claims

1. A capacitive voltage divider type voltage transformer suitable for broadband voltage measurement, comprising a main circuit, characterized in that: The main line is connected in series with a high-voltage capacitor and a low-voltage capacitor in sequence, a neutral point measurement coil is wound around the neutral point below the low-voltage capacitor, an impedance converter is connected in parallel to the front and rear end lines of the low-voltage capacitor and the neutral point measurement coil, and the impedance converter is connected in parallel to an ammeter.

2. A capacitive voltage divider type voltage transformer suitable for broadband voltage measurement according to claim 1, characterized in that: The capacitance of the high-voltage capacitor is C1, and the calculation formula of the capacitance of the high-voltage capacitor C1 is: Where f is the frequency, X C1 is the required capacitive reactance of the high voltage capacitor C1.

3. A capacitive voltage divider type voltage transformer suitable for broadband voltage measurement according to claim 1, characterized in that: The capacitance of the low-voltage capacitor is C2, and the capacitance of the low-voltage capacitor C2 is 10 times the capacitance of the high-voltage capacitor C1.

4. A capacitive voltage divider type voltage transformer suitable for wide-band voltage measurement according to claim 1, characterized in that: The high voltage capacitor and the low voltage capacitor use ceramic capacitors.

5. The capacitive voltage divider type voltage transformer suitable for broadband voltage measurement according to claim 1, characterized in that: The neutral point measurement coil adopts an air-core coil and adopts a silver-plated copper wire or a tin-plated copper wire.

6. A capacitive voltage divider type voltage transformer suitable for wide-band voltage measurement according to claim 1, characterized in that: The calculation formula of the neutral point measurement coil inductance value L is as follows: Where f is the resonant frequency of C2 near the highest frequency, and C2 is the capacitance of the low-voltage capacitor.

7. A capacitive voltage divider type voltage transformer suitable for wide-band voltage measurement according to claim 1, characterized in that: The impedance converter includes an operational amplifier, the operational amplifier model is OPA656, the operational amplifier is connected to a dual-unit power supply, the positive and negative ends of the dual-unit power supply are respectively between +5V and -5V, two 10μF capacitors are set at the input end of the power bypass of the operational amplifier, and two 0.1μF capacitors are set at the output end. An output matching resistor is set between the output end of the operational amplifier and the output end of the circuit, and the output matching resistor is 50Ω.

8. The capacitive voltage divider type voltage transformer suitable for broadband voltage measurement according to claim 1, characterized in that: The operational amplifier input resistance is 10 13 Ω.

9. A method for measuring a capacitive voltage transformer suitable for wideband voltage measurement, characterized in that: The following steps are involved: S1 capacitor divides the voltage. In the capacitor voltage divider, the high voltage signal V in The output voltage V is obtained by dividing the voltage through the high-voltage capacitor C1 and the low-voltage capacitor C2. out , the voltage V out The calculation formula is: Among them, V in Indicates high voltage signal, X C1 and X C2 are the capacitive reactances of the high-voltage capacitor C1 and the low-voltage capacitor C2, respectively, and the calculation formula is: Where f is the frequency, C1 is the high voltage capacitor value, and C2 is the low voltage capacitor value; S2 calculates the voltage divider ratio and converts the capacitive reactance X obtained in the previous step into C1 , X C2 Substituting into the voltage V out Calculate the formula to get the voltage divider ratio formula: Calculation of the induced voltage of the S3 inductor. The neutral point measurement coil L generates an induced voltage V by sensing the current change in the high-voltage capacitor C1. L , and its calculation formula is: Among them, L is the inductance of the coil, I is the current flowing through the coil, t is the time the current flows through the coil, and the current I flowing through the coil is the current I flowing through the low-voltage capacitor C1 , the formula is: Therefore, the induced voltage V on the coil L The calculation formula can be expressed as: Among them, V in represents the high voltage signal, C2 represents the capacitance of the low voltage capacitor, L is the inductance of the coil, and t is the time for the current to flow through the coil; The output voltage of the S4 impedance converter is calculated by first calculating the gain A of the operational amplifier. V , the gain of the OPA656 operational amplifier is: A V =1; Calculate the output voltage V of the impedance converter out' , the V out' The calculation formula is: Where V out' The output voltage of the impedance converter depends on the capacitor voltage divider ratio and the operational amplifier A. V Gain of S5 calculates the total measured voltage, combining the above V out' Calculation formula and V L The total measured voltage is calculated by the formula V total : Among them, V out' represents the output voltage of the impedance converter, A V represents the gain of the operational amplifier, V in represents the high voltage signal, C1 and C2 represent the capacitance of the high voltage capacitor and the low voltage capacitor, L is the inductance of the coil, and t is the time the current flows through the coil.

10. A capacitive voltage transformer measurement method suitable for wide-band voltage measurement according to claim 9, characterized in that: The operational amplifier used in the impedance converter does not use a feedback resistor to maintain a high input impedance.

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