CN210273484U - Protective circuit of capacitance voltage division type electronic voltage transformer - Google Patents
Protective circuit of capacitance voltage division type electronic voltage transformer Download PDFInfo
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- CN210273484U CN210273484U CN201921361912.6U CN201921361912U CN210273484U CN 210273484 U CN210273484 U CN 210273484U CN 201921361912 U CN201921361912 U CN 201921361912U CN 210273484 U CN210273484 U CN 210273484U
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Abstract
The utility model relates to a protective circuit of a capacitance voltage-dividing electronic voltage transformer, which comprises a first-stage protective circuit and a second-stage protective circuit, wherein a common mode choke coil is arranged between the first-stage protective circuit and the second-stage protective circuit; the first-stage protection circuit comprises a piezoresistor and a gas discharge tube, the piezoresistor and the gas discharge tube are connected in series and then connected in parallel at two ends of a medium-voltage capacitor, and a first resistor is connected in parallel at two ends of the medium-voltage capacitor; the second-stage protection circuit comprises a common-mode protection circuit, a differential-mode protection circuit and a low-pass filter circuit, the common-mode protection circuit, the differential-mode protection circuit and the low-pass filter circuit are respectively connected with two ends of the output end of the common-mode choke coil, the low-pass filter circuit is connected with an amplifier, and the output end of the amplifier is connected with a signal conditioning circuit. The utility model discloses a protection circuit can improve capacitive voltage transformer's transient state performance to avoid follow-up signal conditioning circuit to avoid common mode voltage's influence.
Description
Technical Field
The utility model relates to an intelligent transformer substation technical field especially relates to a electric capacity partial pressure formula electronic voltage transformer's protection circuit.
Background
The capacitive voltage divider is arranged on the high-voltage primary equipment body. During operation of high voltage switchgear, the contact gap can produce a strong arcing phenomenon. Gap arcing is a very complex electro-physical process with wide frequency band, high capacity, diverse and unstable forms. Therefore, ultrahigh frequency electromagnetic waves are transmitted and reflected in free space or cavities with different shapes, high-frequency and high-voltage electromagnetic interference is generated, and serious interference and influence are caused to the signal acquisition and processing of the capacitive voltage divider. Therefore, the signal port needs to have processing measures such as protection, filtering and the like.
In a signal acquisition protection circuit of a capacitive voltage division type electronic voltage transformer, the current general design scheme is as follows: (1) a voltage dependent resistor or a transient voltage suppression diode (TVS for short) is connected in parallel with the medium-voltage capacitor to serve as a signal port protection measure; (2) a miniature voltage transformer is used as an electrical isolation device between a capacitive voltage divider and a signal acquisition system; (3) after the isolation device, the signal conditioning circuit is built directly with a general operational amplifier.
The circuits respectively have the following corresponding disadvantages: (1) the junction capacitance of the piezoresistor or the transient diode device is large, generally in the order of magnitude range of hundreds to thousands of pF, and the direct parallel connection with the medium-voltage capacitor can influence the signal measurement precision and increase the leakage current; (2) the miniature voltage transformer comprises an iron core, inhibits higher harmonic components and introduces phase difference up to several radian orders of magnitude; (3) the micro voltage transformer cannot suppress or offset common-mode voltage, and the general operational amplifier can damage devices when working under the condition of higher common-mode voltage.
SUMMERY OF THE UTILITY MODEL
The utility model provides a capacitance voltage division formula electronic voltage transformer's protection circuit can improve capacitance voltage transformer's transient state performance to avoid follow-up signal conditioning circuit to avoid common mode voltage's influence.
The specific contents of the utility model are as follows: a protection circuit of a capacitive voltage division type electronic voltage transformer comprises a first-stage protection circuit and a second-stage protection circuit, wherein a common mode choke coil is arranged between the first-stage protection circuit and the second-stage protection circuit;
the first-stage protection circuit comprises a piezoresistor and a gas discharge tube, the piezoresistor and the gas discharge tube are connected in series and then connected in parallel at two ends of a medium-voltage capacitor, and two ends of the medium-voltage capacitor are connected in parallel with a first resistor;
the second-stage protection circuit comprises a common-mode protection circuit, a differential-mode protection circuit and a low-pass filter circuit, the common-mode protection circuit, the differential-mode protection circuit and the low-pass filter circuit are respectively connected with two ends of the output end of the common-mode choke coil,
the low-pass filter circuit is connected with an amplifier, and the output end of the amplifier is connected with a signal conditioning circuit.
Further, the common mode protection circuit comprises a first transient diode and a second transient diode, and the first transient diode and the second transient diode are respectively connected with two ends of the common mode choke coil and grounded.
Further, the differential mode protection circuit comprises a third transient diode, and two ends of the third transient diode are respectively connected with two ends of the output end of the common mode choke coil.
Furthermore, the low-pass filter circuit comprises a second resistor, a third resistor, a first capacitor, a second capacitor and a third capacitor, the second resistor, the second capacitor, the third resistor and the third capacitor respectively form a common-mode low-pass filter circuit, and the second resistor, the third resistor and the first capacitor form a differential-mode low-pass filter circuit.
Further, the second resistor is arranged between the common mode choke coil and the first capacitor, one end of the second capacitor is arranged between the second resistor and the first capacitor, and the other end of the second capacitor is grounded; the third resistor is arranged between the common mode choke coil and the first capacitor, one end of the third capacitor is arranged between the third resistor and the first capacitor, and the other end of the third capacitor is grounded.
Furthermore, the protection circuit is installed at the port of the signal acquisition loop of the voltage transformer.
Furthermore, a high-voltage terminal, a medium-voltage terminal and a ground terminal are led out of the capacitive voltage divider, the medium-voltage terminal and the ground terminal are arranged on the medium-voltage capacitor, and the first-stage protection circuit is arranged at two ends of the medium-voltage capacitor.
The utility model has the advantages that: after the structure is adopted, the requirement of accurately measuring the capacitance voltage division signal under the environment of serious electromagnetic interference is met, the precision of a signal source (namely voltage division capacitance) is not influenced, the transient performance of the capacitance voltage transformer is improved, and a subsequent signal conditioning circuit is prevented from being influenced by common-mode voltage.
Drawings
The following further explains the embodiments of the present invention with reference to the drawings.
Fig. 1 is a schematic diagram of a protection circuit of the capacitive voltage-dividing electronic voltage transformer of the present invention.
Detailed Description
With reference to fig. 1, the present embodiment discloses a protection circuit for a capacitive voltage-dividing electronic voltage transformer, where the protection circuit is installed at a port of a signal acquisition loop of the voltage transformer. The capacitive voltage divider leads out a high-voltage terminal, a medium-voltage terminal and a grounding terminal, the medium-voltage terminal and the grounding terminal are arranged on a medium-voltage capacitor CL, and a first-stage protection loop is installed at two ends of the medium-voltage capacitor CL.
The protection circuit comprises a first-stage protection circuit and a second-stage protection circuit, wherein the first-stage protection circuit is connected with the second-stage protection circuit through a common mode choke coil L. The common mode choke coil L isolates the common mode interference at two ends of the capacitive voltage divider and the signal processing circuit, and cuts off a common mode interference transmission channel between the capacitive voltage divider and the signal processing circuit. Along with the increase of the common mode interference frequency, the inductance and the linearity of the common mode choke coil L are increased, which is equivalent to increasing the impedance of a common mode interference transmission path, playing a role in isolation and simultaneously realizing the cascading effect of front and rear two-stage protective devices.
Wherein, first order protection return circuit includes piezo-resistor MOV and gas discharge tube GDT, and the parallel connection is at medium voltage capacitor CL both ends behind piezo-resistor MOV and the gas discharge tube GDT series connection mutually, and first resistance R1 is parallelly connected at medium voltage capacitor CL both ends, and two inputs of common mode choke L are connected respectively at first resistance R1 both ends, and is concrete, and medium voltage terminal and ground terminal are still connected respectively to two inputs of common mode choke L.
The junction capacitance of the varistor MOV is large, typically on the order of a few to a dozen nF. The direct parallel connection of the voltage dependent resistor MOV to the side of the medium voltage capacitor CL is equivalent to directly adding the junction capacitance value to the value of the medium voltage capacitor CL, which affects the precision of the capacitive voltage divider. The junction capacitance of the gas discharge tube GDT is very small, typically in the order of one or two pF. The integral junction capacitance after the MOV and the GDT are connected in series is the value of the GDT, and the precision of the voltage division capacitor cannot be influenced. Since the divided voltage of the medium voltage capacitor CL is in the order of several volts, the clamping voltage of the first stage protection device is typically in the order of several tens of volts.
Proper sizing of the first resistor R1 in parallel with the piezoelectric capsule CL can significantly improve the transient performance of the capacitor voltage transformer. When the circuit is broken or short-circuited and the circuit voltage is suddenly changed, the capacity stored in the capacitive voltage divider is released through the first resistor R1 connected in parallel, so that the quick response and tracking measurement of the voltage change of the circuit are realized, and the transient characteristic requirement of the voltage transformer is met.
The second-stage protection loop comprises a first transient diode TVS1, a second transient diode TVS2, a third transient diode TVS3, a second resistor R2, a third resistor R3, a first capacitor C1, a second capacitor C2, a third capacitor C3 and a high common mode voltage differential amplifier D1.
The common mode protection circuit comprises a first transient diode TVS1 and a second transient diode TVS2, and the structure is that one end of the first transient diode TVS1 is connected with one of the output ends of the common mode choke L, and the other end of the first transient diode TVS1 is grounded; one end of the second transient diode TVS2 is connected to the other of the output ends of the common mode choke coil L, and the other end of the second transient diode TVS2 is grounded.
The differential mode protection circuit includes a third transient diode TVS3, and is configured such that two terminals of the third transient diode TVS3 are connected to two terminals of an output terminal of the common mode choke L, respectively, and the first transient diode TVS1 and the second transient diode TVS2 are both disposed between the common mode choke L and the third transient diode TVS 3.
The first transient diode TVS1, the second transient diode TVS2 implement common mode protection of the signal line, and the third transient diode TVS3 implement differential mode protection function. The supply voltage of the subsequent differential amplifier D1 is typically in the order of tens of volts, so the clamp voltage of the TVS transistor also takes tens of volts and is lower than the supply voltage of the differential amplifier D1.
The low-pass RC filter circuit comprises a second resistor R2, a third resistor R3, a first capacitor C1, a second capacitor C2 and a third capacitor C3, wherein the second resistor, the second capacitor, the third resistor and the third capacitor respectively form a common-mode low-pass filter circuit, and the second resistor, the third resistor and the first capacitor form a differential-mode low-pass filter circuit.
Specifically, the second resistor R2 is disposed between the common mode choke coil L and the first capacitor C1, one end of the second capacitor C2 is disposed between the second resistor R2 and the first capacitor C1, and the other end is grounded; the third resistor R3 is disposed between the common mode choke coil L and the first capacitor C1, and one end of the third capacitor C3 is disposed between the third resistor R3 and the first capacitor C1, and the other end is grounded. And the third transient diode TVS3, the second resistor R2, the first capacitor C1 and the third resistor R3 also form a loop.
The low-pass RC filter between the front and the back of the high common-mode voltage differential amplifier D1 mainly performs two functions: (1) the high common mode voltage differential amplifier D1 has a strong suppression function to common mode interference in a certain frequency band, so that before D1, the common mode choke L itself is an inductance device which needs to perform proper bandwidth limitation on signals (2), and a better filtering effect can be achieved by forming an LC filter circuit through the cooperation of capacitors. The second resistor R2 and the third resistor R3 are inserted between the common mode choke coil L and the first capacitor C1, and between the second capacitor C2 and the third capacitor C3, so that the LC resonance phenomenon is suppressed.
The high common-mode voltage differential amplifier D1 is a four-resistor classical differential amplifier, has excellent common-mode rejection ratio in a wider frequency range at a higher common-mode voltage, can accurately measure differential input signals, provides common-mode or differential-mode overvoltage protection for input, and improves the working reliability of a subsequent signal conditioning circuit.
The protection circuit comprises two stages of protection circuits which are connected in series through a common mode choke coil L; a resistor R1 is connected in parallel at the CL side of the medium-voltage capacitor, so that the transient performance of the capacitor voltage transformer is improved; the high common mode voltage differential amplifier D1 protects the subsequent signal conditioning circuitry from damaging devices. The signal protection circuit of the capacitive voltage-dividing electronic voltage transformer meets the requirement of accurately measuring capacitive voltage-dividing signals in a severe electromagnetic interference environment, does not affect the precision of a signal source (namely, a voltage-dividing capacitor), improves the transient performance of the capacitive voltage transformer, and avoids the influence of common-mode voltage on a subsequent signal conditioning circuit.
In the previous description, numerous specific details were set forth in order to provide a thorough understanding of the invention. The foregoing description is only illustrative of the preferred embodiments of the invention, which can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. All the contents that do not depart from the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical substance of the present invention all still belong to the protection scope of the technical solution of the present invention.
Claims (7)
1. The utility model provides a protection circuit of electric capacity partial pressure formula electronic voltage transformer which characterized in that: the protection circuit comprises a first-stage protection circuit and a second-stage protection circuit, wherein a common-mode choke coil is arranged between the first-stage protection circuit and the second-stage protection circuit;
the first-stage protection circuit comprises a piezoresistor and a gas discharge tube, the piezoresistor and the gas discharge tube are connected in series and then connected in parallel at two ends of a medium-voltage capacitor, and two ends of the medium-voltage capacitor are also connected in parallel with a first resistor;
the second-stage protection circuit comprises a common-mode protection circuit, a differential-mode protection circuit and a low-pass filter circuit, the common-mode protection circuit, the differential-mode protection circuit and the low-pass filter circuit are respectively connected with two ends of the output end of the common-mode choke coil,
the low-pass filter circuit is connected with an amplifier, and the output end of the amplifier is connected with a signal conditioning circuit.
2. The protection circuit of the capacitive voltage-dividing electronic voltage transformer according to claim 1, wherein: the common mode protection circuit comprises a first transient diode and a second transient diode, and the first transient diode and the second transient diode are respectively connected with two ends of the common mode choke coil and grounded.
3. The protection circuit of the capacitive voltage-dividing electronic voltage transformer according to claim 1, wherein: the differential mode protection circuit comprises a third transient diode, and two ends of the third transient diode are respectively connected with two ends of the output end of the common mode choke coil.
4. The protection circuit of the capacitive voltage-dividing electronic voltage transformer according to claim 3, wherein: the low-pass filter circuit comprises a second resistor, a third resistor, a first capacitor, a second capacitor and a third capacitor, wherein the second resistor, the second capacitor, the third resistor and the third capacitor respectively form a common-mode low-pass filter circuit, and the second resistor, the third resistor and the first capacitor form a differential-mode low-pass filter circuit.
5. The protection circuit of the capacitive voltage-dividing electronic voltage transformer according to claim 4, wherein: the second resistor is arranged between the common mode choke coil and the first capacitor, one end of the second capacitor is arranged between the second resistor and the first capacitor, and the other end of the second capacitor is grounded; the third resistor is arranged between the common mode choke coil and the first capacitor, one end of the third capacitor is arranged between the third resistor and the first capacitor, and the other end of the third capacitor is grounded.
6. The protection circuit of the capacitive voltage-dividing electronic voltage transformer according to claim 1, wherein: the protection circuit is installed at the port of the voltage transformer signal acquisition loop.
7. The protection circuit of the capacitive voltage-dividing electronic voltage transformer according to claim 1, wherein: a high-voltage terminal, a medium-voltage terminal and a grounding terminal are led out of the capacitive voltage divider, the medium-voltage terminal and the grounding terminal are arranged on the medium-voltage capacitor, and the first-stage protection circuit is arranged at two ends of the medium-voltage capacitor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921361912.6U CN210273484U (en) | 2019-08-21 | 2019-08-21 | Protective circuit of capacitance voltage division type electronic voltage transformer |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921361912.6U CN210273484U (en) | 2019-08-21 | 2019-08-21 | Protective circuit of capacitance voltage division type electronic voltage transformer |
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| CN210273484U true CN210273484U (en) | 2020-04-07 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201921361912.6U Active CN210273484U (en) | 2019-08-21 | 2019-08-21 | Protective circuit of capacitance voltage division type electronic voltage transformer |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110429565A (en) * | 2019-08-21 | 2019-11-08 | 南京大全自动化科技有限公司 | A kind of protection circuit of capacitance-voltage-distributing type electronic type voltage transformer |
| CN114188926A (en) * | 2022-01-10 | 2022-03-15 | 智道网联科技(北京)有限公司 | Interface protection circuit, system and electronic equipment |
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2019
- 2019-08-21 CN CN201921361912.6U patent/CN210273484U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110429565A (en) * | 2019-08-21 | 2019-11-08 | 南京大全自动化科技有限公司 | A kind of protection circuit of capacitance-voltage-distributing type electronic type voltage transformer |
| CN114188926A (en) * | 2022-01-10 | 2022-03-15 | 智道网联科技(北京)有限公司 | Interface protection circuit, system and electronic equipment |
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