A method and system for monitoring and protecting an ac-dc superimposed test circuit

Abstract

The application discloses a kind of for AC-DC superposition test loop monitoring and protection method and system, wherein the method comprises: the divider M is set between the high voltage end of test sample CX and ground, and the AC-DC composite voltage signal of test sample CX is measured by the secondary side voltage sensor VT1 of divider M;Resistance RT is set in the DC circuit of test sample CX, and the DC voltage signal of resistance RT is measured by the voltage sensor VT2 connected in parallel with resistance RT;Current transformer CT1 is set in the series resonance circuit of test sample CX, compensation inductance L, direct-current capacitor C1, and the first AC current signal of test sample CX is measured by current transformer CT1;Current transformer CT2 is set in the circuit of transformer T1 and compensation inductance L, and the second AC current signal of compensation inductance L is measured by current transformer CT2;AC-DC composite voltage signal, DC voltage signal, first AC current signal and second AC current signal are sent to data acquisition module.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high voltage test technology, more particularly, to a method and system for monitoring and protecting an AC-DC superimposed test circuit. BACKGROUND

[0002] The durability test and aging damage test of high-voltage dry capacitors are very critical parts of product type tests, mainly evaluating the long-term operation reliability of products. High-voltage dry capacitors applied in flexible HVDC valves, SVG, and rail transit are generally operated under a composite voltage of AC-DC superposition.

[0003] The prior art (application publication number: CN 113447779 A) provides a test circuit principle of AC-DC superposition, which can be used for AC-DC superimposed test of high-voltage dry capacitors. However, during the durability test and aging damage test of high-voltage dry capacitors, there is a high possibility of self-healing failure leading to test product explosion. The circuit proposed by the prior art lacks corresponding voltage and current monitoring and fault protection methods. When the test product capacitor fails, it cannot be discovered and measures cannot be taken in time. Further development of the fault can easily lead to an explosion accident, threatening the safety of equipment and personnel.

[0004] For the test circuit of high-voltage dry capacitors under AC-DC superposition, both the voltage and the current in the circuit contain DC and AC components. The monitoring system requires the ability to measure multiple voltage and current components simultaneously, and the ability to set fault protection measures according to multiple monitoring quantities. A special monitoring and protection method and device need to be designed. In addition, the DC current in the circuit can reach about 1A during charging, while the stable operation process generally only has a few mA, with a large amplitude range. It is difficult to ensure accuracy using conventional current measurement methods. The DC current monitoring method also needs to be designed specifically.

[0005] Therefore, for the AC-DC superimposed test circuit, a practical monitoring and protection method and system need to be proposed. SUMMARY

[0006] The technical solution of the present application provides a method and device for monitoring and protecting an AC-DC superimposed test circuit, to solve the problem of how to monitor and protect an AC-DC superimposed test circuit.

[0007] To solve the above problems, the present application provides a method for monitoring and protecting an AC-DC superimposed test circuit, which comprises:

[0008] A voltage divider M is arranged between the high-voltage end of the test product CX and the ground, and the AC-DC composite voltage signal of the test product CX is measured by a voltage sensor VT1 on the secondary side of the voltage divider M;

[0009] A resistor RT is arranged in a direct current loop of the test sample CX, and a direct current voltage signal of the resistor RT is measured by a voltage sensor VT2 connected in parallel with the resistor RT;

[0010] A current transformer CT1 is arranged in a series resonance loop composed of the test sample CX, a compensation inductor L, and a direct current blocking capacitor C1, and a first alternating current signal of the test sample CX is measured by the current transformer CT1;

[0011] A current transformer CT2 is arranged in a loop of the transformer T1 and the compensation inductor L, and a second alternating current signal of the compensation inductor L is measured by the current transformer CT2;

[0012] The alternating current voltage signal, the direct current voltage signal, the first alternating current signal, and the second alternating current signal are transmitted to a data acquisition module.

[0013] Preferably, the method further comprises:

[0014] A direct current voltage amplitude V is obtained by averaging the alternating current voltage signal in one period DC , and an alternating current voltage signal is obtained by subtracting the direct current voltage amplitude V from the alternating current voltage signal DC , and an alternating current voltage value V is calculated based on the alternating current voltage signal AC .

[0015] Preferably, the method further comprises:

[0016] A direct current current amplitude I is obtained by dividing the direct current voltage signal by the resistance of the resistor RT DC .

[0017] Preferably, the method further comprises:

[0018] An alternating current I is calculated based on the first alternating current signal AC1 ;

[0019] An alternating current I is calculated based on the second alternating current signal AC2 .

[0020] Preferably, the method further comprises:

[0021] When the direct current current amplitude I DC is greater than a first threshold value, a protection action is warned;

[0022] When the direct current current amplitude I DC is greater than a second threshold value, a protection action is tripped.

[0023] Preferably, the method further comprises:

[0024] When the direct current voltage amplitude V DC The protection action trips when the direct current voltage amplitude V

[0025] Preferably, it further comprises:

[0026] When the alternating current I AC2 The protection action trips when the alternating current I

[0027] Preferably, it further comprises:

[0028] The first threshold value is 20 mA, and the second threshold value is 100 mA.

[0029] Preferably, it further comprises:

[0030] The third threshold value is 50 A.

[0031] Based on another aspect of the present application, the present application provides a system for monitoring and protecting an AC-DC superimposed test loop, the system comprising:

[0032] A first measuring unit is configured to set a voltage divider M between a high voltage end of a test sample CX and ground, and measure an AC-DC composite voltage signal of the test sample CX through a voltage sensor VT1 on a secondary side of the voltage divider M;

[0033] A second measuring unit is configured to set a resistor RT in a DC loop of the test sample CX, and measure a DC voltage signal of the resistor RT through a voltage sensor VT2 connected in parallel with the resistor RT;

[0034] A third measuring unit is configured to set a current transformer CT1 in a series resonance loop composed of the test sample CX, a compensation inductor L, and a DC blocking capacitor C1, and measure a first alternating current signal of the test sample CX through the current transformer CT1;

[0035] A fourth measuring unit is configured to set a current transformer CT2 in a loop of a transformer T1 and the compensation inductor L, and measure a second alternating current signal of the compensation inductor L through the current transformer CT2;

[0036] A sending unit is configured to send the AC-DC composite voltage signal, the DC voltage signal, the first alternating current signal, and the second alternating current signal to a data acquisition module.

[0037] The technical scheme of the present application provides a method and system for monitoring and protecting an AC-DC superimposed test loop, wherein the method comprises: arranging a voltage divider M between a high voltage end of a test sample CX and the ground, measuring an AC-DC composite voltage signal of the test sample CX through a secondary side voltage sensor VT1 of the voltage divider M; arranging a resistor RT in a DC loop of the test sample CX, measuring a DC voltage signal of the resistor RT through a voltage sensor VT2 connected in parallel with the resistor RT; arranging a current transformer CT1 in a series resonance loop composed of the test sample CX, a compensation inductor L and a DC blocking capacitor C1, measuring a first AC current signal of the test sample CX through the current transformer CT1; arranging a current transformer CT2 in a loop of a transformer T1 and the compensation inductor L, measuring a second AC current signal of the compensation inductor L through the current transformer CT2; and sending the AC-DC composite voltage signal, the DC voltage signal, the first AC current signal and the second AC current signal to a data acquisition module. The method and system for monitoring and protecting an AC-DC superimposed test loop can realize accurate measurement and real-time monitoring of AC and DC voltage and current in an AC-DC superimposed test loop of a dry-type capacitor, set a fault protection action threshold according to the voltage and current, quickly act to cut off the power supply when the test sample fails, avoid further development of the fault, ensure the safety of the dry-type capacitor endurance test and aging destruction test, and have important application value for improving the safety and reliability of the dry-type capacitor type test. BRIEF DESCRIPTION OF DRAWINGS

[0038] The exemplary embodiments of this application can be more fully understood with reference to the following description when taken in connection with the following drawings, in which:

[0039] Figure 1 A flow chart of a method for monitoring and protecting an AC-DC superimposed test loop according to a preferred embodiment of the present application;

[0040] Figure 2 A schematic diagram of a principle of monitoring and protecting an AC-DC superimposed test loop according to a preferred embodiment of the present application; and

[0041] Figure 3 A block diagram of a system for monitoring and protecting an AC-DC superimposed test loop according to a preferred embodiment of the present application. DETAILED DESCRIPTION

[0042] Reference will now be made to the drawings to describe the exemplary embodiments of the present application in greater detail. The present application can, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art. Like reference numerals refer to like elements throughout the specification.

[0043] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0044] Figure 1 A flow chart of a method for monitoring and protecting an AC-DC superimposed test circuit according to a preferred embodiment of the present application.

[0045] As shown in Figure 1 , the present application provides a method for monitoring and protecting an AC-DC superimposed test circuit, the method comprising:

[0046] Step 101: setting a voltage divider M between a high voltage end of a test sample CX and ground, and measuring an AC-DC composite voltage signal of the test sample CX through a voltage sensor VT1 on a secondary side of the voltage divider M.

[0047] The AC-DC superimposed voltage applied to the test sample CX is measured by a resistance-capacitance voltage divider M, which is connected between the high voltage end of CX and ground, as shown in Figure 2 , the model of the voltage divider can be selected as 10kV, and the division ratio is 1000:1. A composite voltage signal containing DC and AC components is obtained on the voltage sensor VT1 on the secondary side of the voltage divider, and the voltage signal is transmitted to the corresponding acquisition port of the data acquisition module through a signal line.

[0048] Step 102: setting a resistance RT in a DC circuit of the test sample CX, and measuring a DC voltage signal of the resistance RT through a voltage sensor VT2 connected in parallel with the resistance RT.

[0049] The DC current flowing through the test sample CX in the present application reaches about 1A during the charging process, and only 5mA during the normal operation process after the voltage is stabilized. The accuracy of a conventional DC current measurement unit is generally 1%, and if a measurement unit with a range of 2A is used, the measurement resolution is only 20mA, and the measurement error is large during the normal operation process; if a measurement unit with a resolution of 1mA is used, the DC current will exceed the range during the charging process, causing damage to the measurement unit. Therefore, a small resistance RT is connected in series in the DC circuit in the present application, and the DC current on the test sample is indirectly obtained by measuring the voltage on the RT, as shown in Figure 2 , the RT is connected to the low voltage side of the DC circuit, and the resistance of the RT can be preferably 2Ω, and the capacity can be selected as 20W. The voltage sensor VT2 is used to measure the voltage on the resistance RT, and then the signal is transmitted to the corresponding port of the data acquisition module.

[0050] Step 103: Set the current transformer CT1 in the series resonant circuit composed of the test sample CX, the compensation inductor L, and the DC blocking capacitor C1, and measure the first AC current signal of the test sample CX through the current transformer CT1.

[0051] The alternating current on the test sample CX of this invention is measured by a current transformer CT1. CT1 is connected in a series resonant circuit consisting of the test sample CX, the compensation inductor L, and the DC blocking capacitor C1, and should be installed on the low-voltage side. The range of the transformer CT1 is selected as 1kA, and the coil diameter is required to be greater than 5cm to allow it to pass smoothly through the copper busbar of the circuit. The current signal on CT1 is also transmitted to the corresponding port of the data acquisition module.

[0052] Step 104: Set the current transformer CT2 in the circuit between transformer T1 and compensation inductor L, and measure the second AC current signal of compensation inductor L through the current transformer CT2;

[0053] The circuit of this invention uses inductor L to compensate for the capacity of the test sample CX in order to reduce the demand on power supply capacity. The magnitude of the compensated current will directly correspond to the primary side of transformer T1 and the voltage regulator VG1 circuit. Due to the power supply capacity limitation, the compensated current should not exceed a certain limit. Therefore, the AC current value after inductor L compensation is measured in the circuit through CT2. The range of CT2 is selected as 100A, and the current signal on it is also transmitted to the corresponding port of the data acquisition module.

[0054] Step 105: Send the AC / DC composite voltage signal, DC voltage signal, first AC current signal, and second AC current signal to the data acquisition module.

[0055] Preferably, the method further includes:

[0056] The DC voltage amplitude V is obtained by averaging the AC / DC composite voltage signal over one cycle. DC Then, the DC voltage amplitude V is subtracted from the AC / DC composite voltage signal. DC Obtain the AC voltage signal, and calculate the AC voltage value V based on the AC voltage signal. AC .

[0057] Preferably, the method further includes:

[0058] Dividing the DC voltage signal by the resistance RT yields the DC current amplitude I. DC .

[0059] Preferably, the method further includes:

[0060] Calculate the AC current I based on the first AC current signal. AC1 ;

[0061] Calculate the AC current I based on the second AC current signal. AC2.

[0062] Preferably, it further includes:

[0063] When the DC current amplitude I DC When the value exceeds the first threshold, the protection system will issue an alarm.

[0064] When the DC current amplitude I DC If the value exceeds the second threshold, the protection mechanism will trip.

[0065] Preferably, it further includes:

[0066] When the DC voltage amplitude V DC When the voltage drops to 0.9 times the rated voltage, the protection trips.

[0067] Preferably, it further includes:

[0068] When the alternating current I AC2 When the value exceeds the third threshold, the protection mechanism trips.

[0069] Preferably, it further includes:

[0070] The first threshold is 20mA, and the second threshold is 100mA.

[0071] Preferably, it further includes:

[0072] The third threshold is 50A.

[0073] In this invention, the data acquisition module selects a sampling rate of 1kHz to transmit the sampled AC and DC voltage and current signals to the analysis and control module for analysis and processing of each composite signal.

[0074] The DC voltage amplitude V of the AC / DC composite voltage signal input to VT1 in this invention is obtained by averaging over one cycle. DC Then subtract V from the composite voltage signal DC By obtaining the AC voltage signal, the effective value V of the AC voltage can be calculated. AC .

[0075] The DC voltage signal input to VT2 in this invention is divided by the resistance value of resistor RT (2Ω) to obtain the DC current amplitude I. DC .

[0076] The effective value I of the AC current input signals of CT1 and CT2 in this invention can be directly calculated. AC1 and I AC2 .

[0077] The present invention will use the above-mentioned V DC I DC V AC I AC1 I AC2The signal is transmitted to the display module for real-time monitoring, and simultaneously to the storage module for storage. The storage frequency can be selected once per minute.

[0078] This invention formulates a fault determination method based on the circuit voltage and current characteristics when the test sample fails, and issues a protection action signal through the analysis and control module when a fault occurs.

[0079] This invention is applicable to test samples that are highly likely to fail self-healing during testing, resulting in internal short-circuit faults. At this time, the main characteristics of the circuit include a rapid decrease in DC voltage, a significant increase in DC current, and an overshoot in AC current. These characteristics can be used to develop a fault determination method.

[0080] After the self-healing failure inside the sample, the DC current I of this invention... DC It will increase significantly, but the degree of failure will differ. DC There are differences; this invention sets I. DC When the current is greater than 20mA, the protection system will activate and issue an alarm. The alarm function is set in the display module to send a fault signal, and the test personnel will determine whether to terminate the test based on the on-site situation. DC When the current is greater than 100mA, the protection trips and transmits the trip signal to switches K1 and K2 on the AC and DC sides of the voltage regulator, disconnecting the power supply on both sides to prevent the internal fault of the test sample from developing further and causing greater damage.

[0081] In this invention, after a self-healing failure occurs within the test sample, the energy stored in the sample's capacitor is released through the failure point. Since the charging rate is less than the energy release rate, the DC voltage of the test sample will decrease. During normal operation, if V... DC The circuit breaker will trip when the voltage drops to 0.9 times the rated voltage.

[0082] In this invention, when a short-circuit fault occurs inside the sample, the AC circuit current will generate a large overshoot. The compensated AC current I AC2 Define it as a decision quantity, and set I. AC2 If the current exceeds 50A, the circuit breaker will trip.

[0083] The analysis and control module of this invention is equipped with the above three fault protections, which work together and serve as backups for each other to ensure effective protection of the circuit equipment and test personnel in the event of a sample failure.

[0084] This invention provides necessary monitoring and protection for AC / DC superposition test circuits of high-voltage dry capacitors. When a test specimen malfunctions, it promptly alerts the test personnel and trips the circuit power supply as soon as possible to prevent the test specimen malfunction from escalating and causing an explosion.

[0085] This invention solves the problem that the DC current of a test sample differs greatly in magnitude during the charging and normal operation processes, making it difficult to measure accurately at the same time. It provides a simple and practical method and device for measuring the DC current of a test sample.

[0086] This invention can display the measured key voltage and current parameters of the circuit in real time, allowing test personnel to understand the status of the test sample at any time. At the same time, the voltage and current parameters can be stored and retrieved for review during later test processes, improving the traceability of the test process.

[0087] This invention makes the AC / DC superposition test circuit more reliable and safer in actual use, and has important application value for promoting the method of using AC / DC superposition for durability and aging damage testing of high-voltage dry capacitors.

[0088] Figure 2 This is a schematic diagram of the monitoring and protection principle of the AC / DC superposition test circuit according to a preferred embodiment of the present invention. Figure 2 In the diagram, VG1 and VG2 are voltage regulators; K1 and K2 are voltage regulator power switches; T1 and T2 are transformers; L is a compensating reactor; C1 is a DC blocking capacitor; CX is a test capacitor; D is a rectifier silicon stack; M is a resistive-capacitive voltage divider; VT1 and VT2 are voltage measurement units; and CT1 and CT2 are AC current measurement units.

[0089] Figure 3 This is a system structure diagram of a preferred embodiment of the present invention for monitoring and protecting an AC / DC superimposed test circuit. Figure 3 As shown, the present invention provides a system for monitoring and protecting an AC / DC superimposed test circuit, the system comprising:

[0090] The first measuring unit 301 is used to set the voltage divider M between the high voltage end of the test sample CX and ground, and to measure the AC / DC composite voltage signal of the test sample CX through the secondary side voltage sensor VT1 of the voltage divider M.

[0091] The second measuring unit 302 is used to set the resistor RT in the DC circuit of the sample CX and measure the DC voltage signal of the resistor RT by a voltage sensor VT2 connected in parallel with the resistor RT.

[0092] The third measurement unit 303 is used to set the current transformer CT1 in the series resonant circuit composed of the test sample CX, the compensation inductor L, and the DC blocking capacitor C1, and to measure the first AC current signal of the test sample CX through the current transformer CT1.

[0093] The fourth measurement unit 304 is used to set the current transformer CT2 in the circuit of transformer T1 and compensation inductor L, and to measure the second AC current signal of the compensation inductor L through the current transformer CT2.

[0094] The transmitting unit 305 is used to transmit the AC / DC composite voltage signal, the DC voltage signal, the first AC current signal, and the second AC current signal to the data acquisition module.

[0095] Preferably, the DC voltage amplitude V is obtained by averaging the AC / DC composite voltage signal over one cycle. DC Then, the DC voltage amplitude V is subtracted from the AC / DC composite voltage signal. DC Obtain the AC voltage signal, and calculate the AC voltage value V based on the AC voltage signal. AC .

[0096] Preferably, the DC current amplitude I is obtained by dividing the DC voltage signal by the resistance value of the resistor RT. DC .

[0097] Preferably, the AC current I is calculated based on the first AC current signal. AC1 ;

[0098] Calculate the AC current I based on the second AC current signal. AC2 .

[0099] Preferably, when the DC current amplitude I DC When the value exceeds the first threshold, the protection system will issue an alarm.

[0100] When the DC current amplitude I DC If the value exceeds the second threshold, the protection mechanism will trip.

[0101] Preferably, when the DC voltage amplitude V DC When the voltage drops to 0.9 times the rated voltage, the protection trips.

[0102] Preferably, when the alternating current I AC2 When the value exceeds the third threshold, the protection mechanism trips.

[0103] Preferably, the first threshold is 20mA and the second threshold is 100mA.

[0104] Preferably, the third threshold is 50A.

[0105] The preferred embodiment of the present invention provides a system 300 for monitoring and protecting an AC / DC superimposed test circuit, which corresponds to another preferred embodiment of the present invention, a method 100 for monitoring and protecting an AC / DC superimposed test circuit. These will not be described in detail here.

[0106] The invention has been described with reference to a few embodiments. However, as will be known to those skilled in the art, and as defined in the appended claims, other embodiments besides those disclosed above fall equivalently within the scope of the invention.

[0107] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / the / the [device, component, etc.]” ​​are openly interpreted as at least one instance of said device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless explicitly stated otherwise.

Claims

1. A method for monitoring and protecting an AC / DC superimposed test circuit, the method comprising: The voltage divider M is placed between the high voltage end of the test sample CX and ground, and the AC / DC composite voltage signal of the test sample CX is measured by the voltage sensor VT1 on the secondary side of the voltage divider M. A resistor RT is placed in the DC circuit of the test sample CX, and the DC voltage signal of the resistor RT is measured by a voltage sensor VT2 connected in parallel with the resistor RT. A current transformer CT1 is placed in the series resonant circuit composed of the test sample CX, the compensation inductor L, and the DC blocking capacitor C1. The first AC current signal of the test sample CX is measured through the current transformer CT1. A current transformer CT2 is placed in the circuit between transformer T1 and compensation inductor L, and the second AC current signal of the compensation inductor L is measured through the current transformer CT2. The AC / DC composite voltage signal, the DC voltage signal, the first AC current signal, and the second AC current signal are sent to the data acquisition module; The DC current amplitude I is obtained by dividing the DC voltage signal by the resistance value of the resistor RT. DC ; When the DC current amplitude I DC When the value exceeds the first threshold, the protection system will issue an alarm. When the DC current amplitude I DC If the value exceeds the second threshold, the protection mechanism will trip.

2. The method according to claim 1, further comprising: The DC voltage amplitude V is obtained by averaging the AC / DC composite voltage signal over one period. DC Then, the DC voltage amplitude V is subtracted from the AC / DC composite voltage signal. DC Obtain the AC voltage signal, and calculate the AC voltage value V based on the AC voltage signal. AC .

3. The method according to claim 1, further comprising: Calculate the AC current I based on the first AC current signal. AC1 ; Calculate the AC current I based on the second AC current signal. AC2 .

4. The method according to claim 2, further comprising: When the DC voltage amplitude V DC When the voltage drops to 0.9 times the rated voltage, the protection trips.

5. The method according to claim 3, further comprising: When the alternating current I AC2 When the value exceeds the third threshold, the protection mechanism trips.

6. The method according to claim 1, further comprising: The first threshold is 20mA, and the second threshold is 100mA.

7. The method according to claim 5, further comprising: The third threshold is 50A.

8. A system for monitoring and protecting an AC / DC superimposed test circuit, the system comprising: The first measurement unit is used to set the voltage divider M between the high voltage end of the test sample CX and ground, and to measure the AC / DC composite voltage signal of the test sample CX through the voltage sensor VT1 on the secondary side of the voltage divider M. The second measuring unit is used to set the resistor RT in the DC circuit of the sample CX and measure the DC voltage signal of the resistor RT by a voltage sensor VT2 connected in parallel with the resistor RT. The third measurement unit is used to set the current transformer CT1 in the series resonant circuit composed of the test sample CX, the compensation inductor L, and the DC blocking capacitor C1, and to measure the first AC current signal of the test sample CX through the current transformer CT1. The fourth measurement unit is used to set the current transformer CT2 in the circuit between the transformer T1 and the compensation inductor L, and to measure the second AC current signal of the compensation inductor L through the current transformer CT2. The transmitting unit is used to transmit the AC / DC composite voltage signal, the DC voltage signal, the first AC current signal, and the second AC current signal to the data acquisition module; and to divide the DC voltage signal by the resistance value of the resistor RT to obtain the DC current amplitude I. DC When the amplitude of the DC current I DC When the DC current amplitude exceeds the first threshold, the protection system will issue an alarm; when the DC current amplitude I... DC If the value exceeds the second threshold, the protection mechanism will trip.

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