CN113702714B - Method for measuring capacitance value of high-voltage arm of direct-current voltage transformer - Google Patents
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- G—PHYSICS
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Abstract
The application discloses a method for measuring a capacitance value of a high-voltage arm of a direct-current voltage transformer, and belongs to the technical field of direct-current transmission engineering. The method of the application comprises the following steps: connecting a reference capacitance voltage divider high-voltage arm capacitor and a reference capacitance voltage divider low-voltage arm adjustable capacitor in series to serve as a reference capacitance voltage divider; the method comprises the steps that a middle voltage end of a reference capacitive voltage divider is connected with an alternating current differential measuring instrument and then connected with a middle voltage end of a direct current voltage transformer, and a high voltage end of the reference capacitive voltage divider is connected with a primary voltage terminal of a high voltage arm of the direct current voltage transformer to construct an alternating current balance bridge; the method comprises the steps of simultaneously connecting the voltage output by an alternating current excitation power supply to a primary voltage terminal of a direct current voltage transformer and a high voltage end of a reference capacitor voltage divider; and adjusting the balance bridge to balance the potential of the balance bridge, acquiring measurement data, and determining the capacitance value of the high-voltage arm of the direct-current voltage transformer according to the measurement data. The application improves the stability of the high-voltage arm capacitance value test.
Description
Technical Field
The application relates to the technical field of direct current transmission engineering, in particular to a method for measuring a capacitance value of a high-voltage arm of a direct current voltage transformer.
Background
The direct-current voltage transformer is used as important equipment for measuring the voltage of the direct-current power transmission system, and has the main function of converting primary direct-current high voltage of an electrode wire to be measured into a low-voltage signal meeting the requirements of a secondary measurement system and a secondary protection system according to a certain proportion under the condition of meeting the requirement of certain accuracy, so that the reliable, stable and safe operation of the direct-current power transmission system is ensured.
The primary body of the direct-current voltage transformer generally adopts the principle of resistance-capacitance voltage division, the high-voltage arm of the direct-current voltage transformer mainly bears rated voltage and transient overvoltage on a polar line, and the direct-current voltage transformer is similar to a combination of a resistor and a capacitor with huge size, and according to different voltage grades, the height of the primary body part of the direct-current voltage transformer is different from a few meters to tens of meters, so that the method and the capability for accurately measuring the resistance-capacitance parameters of the primary body of the direct-current voltage transformer are difficult.
At present, in the direct current transmission engineering, primary voltages of a direct current polar line and a neutral line are measured by adopting a direct current voltage transformer. The primary body of the direct current voltage transformer is based on the principle of a resistor-capacitor voltage divider, and is actually a resistor-capacitor voltage divider. The primary high voltage and the secondary medium voltage are typical voltage division type high voltage measuring equipment by taking the grounding end of the low voltage arm as an electrical reference point. The high-voltage arm is formed by connecting a plurality of high-voltage resistors and high-voltage capacitors in series and in parallel, and one-time high voltage is mainly born by the high-voltage arm.
The parallel capacitor has two main roles in the dc voltage transformer:
1. and the electric field is balanced, and the electric field in the vertical direction of the direct-current voltage transformer is balanced in one transient process by utilizing the characteristic that voltages at two ends of the capacitor are kept unchanged in the transient process.
2. The frequency characteristic is improved, the resistor-capacitor voltage divider has the frequency response characteristic from direct current to high frequency, the impedance characteristic matching of a high voltage arm and a low voltage arm of the resistor-capacitor voltage divider is mainly depended, the parallel capacitor plays a very important role in the impedance matching of the high voltage arm and the low voltage arm, the characteristics of the direct current voltage transformer depend on accurate measurement of various parameters of a resistor and a capacitor element of the high voltage arm, however, the accurate measurement of the capacitance value of the high voltage arm of the direct current voltage transformer is still a difficult problem until now, and an effective and reliable testing method and a testing instrument are not available until now for accurately measuring the capacitance value of the high voltage arm of the direct current voltage transformer.
The main problems are:
1. anti-interference problem. The high-voltage arm has huge physical size, long test lead and large test loop, the conventional RLC bridge is generally used for testing low-voltage parameters such as electronic components, the test level is generally in the voltage level, the test current is generally in the nA level-mA level, and when the high-voltage arm is used for testing the capacitance of the high-voltage arm of the direct-current voltage transformer, the high-voltage arm is easily interfered by electromagnetic environment, and the measurement accuracy is unreliable.
2. The parallel resistors interfere with the capacitance measurement. The high-voltage arm resistor and the capacitor of the direct-current voltage transformer are formed by serially and parallelly connecting a plurality of unit resistors and capacitors, belong to a typical passive RC network, are physically undetachable, the design value of the resistance value of the high-voltage arm is generally between hundreds of MΩ and GΩ, the insulation resistance of the high-voltage arm capacitor is about tens of GΩ, the orders of magnitude of the two resistance value parameters are different approximately, and in a conventional capacitance testing method, the resistance value of the high-voltage arm is processed according to the insulation resistance of the capacitor, so that the capacitance testing result is inaccurate.
Disclosure of Invention
In view of the above problems, the present application provides a method for measuring a capacitance value of a high voltage arm of a dc voltage transformer, including:
connecting a reference capacitance voltage divider high-voltage arm capacitor and a reference capacitance voltage divider low-voltage arm adjustable capacitor in series to serve as a reference capacitance voltage divider;
the method comprises the steps that a middle voltage end of a reference capacitive voltage divider is connected with an alternating current differential measuring instrument and then connected with a middle voltage end of a direct current voltage transformer, and a high voltage end of the reference capacitive voltage divider is connected with a primary voltage terminal of a high voltage arm of the direct current voltage transformer to construct an alternating current balance bridge;
the method comprises the steps of simultaneously connecting the voltage output by an alternating current excitation power supply to a primary voltage terminal of a direct current voltage transformer and a high voltage end of a reference capacitor voltage divider;
and adjusting the AC balance bridge to ensure that the AC balance bridge reaches potential balance, acquiring measurement data, and determining the capacitance value of the high-voltage arm of the DC voltage transformer according to the measurement data.
Optionally, acquiring measurement data specifically includes:
measuring a capacitance value C2 of a low-voltage arm of the direct-current voltage transformer;
calculating a preset capacitance Cn2 of the reference capacitance divider low-voltage arm adjustable capacitor;
determining the optimal working frequency of the alternating current excitation power supply, controlling the alternating current excitation power supply to output test voltage according to the optimal working frequency, adjusting the capacitance Cn2 of the adjustable capacitor of the low-voltage arm of the reference capacitance divider until the indication value of the alternating current differential meter tends to zero, and recording the capacitance Cn2 of the adjustable capacitor of the low-voltage arm of the reference capacitance divider;
and determining a capacitance value C1 of the high-voltage arm of the direct-current voltage transformer according to the C2, cn1 and Cn2.
Alternatively, c1= (c2×cn1)/Cn 2.
Optionally, the preset value of Cn 2=cn1×k, where K is the design value of the voltage dividing ratio of the dc voltage transformer.
Optionally, determining the optimal operating frequency of the ac excitation power source specifically includes:
according to the design value of the resistance value of the high-voltage arm of the direct-current voltage transformer and the design value of the capacitance value of the high-voltage arm of the direct-current voltage transformer, calculating the impedance value Z and the capacitance value X of the high-voltage arm of the direct-current voltage transformer C According to preset conditions, impedance value Z and capacitance value X C And calculating the optimal working frequency of the alternating current excitation power supply.
Optionally, the preset condition is Z approximately equal to X C 。
Optionally, the medium voltage end of the direct current voltage transformer, the medium voltage end of the reference capacitive voltage divider and the alternating current differential meter form a differential measurement loop.
Optionally, the test voltage includes: alternating test voltages of different magnitudes and frequencies.
The application improves the stability of the high-voltage arm capacitance value test and realizes the precise measurement of the high-voltage arm capacitance value of the direct-current voltage transformer.
Drawings
FIG. 1 is a flow chart of the method of the present application;
fig. 2 is a schematic diagram of a primary body structure of a typical dc voltage transformer according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a primary body circuit of a typical DC voltage transformer in an embodiment of the application;
fig. 4 is a schematic diagram of a capacitance value test of a primary high-voltage arm of a dc voltage transformer according to an embodiment of the present application;
FIG. 5 is a schematic diagram of an example of a + -800 kV direct current voltage transformer in an embodiment of the application;
FIG. 6 is a wiring diagram of an example of a capacitance test of a primary high voltage arm of a direct current voltage transformer of + -800 kV in an embodiment of the application;
wherein 1 is a primary body of the direct-current voltage transformer, 2 is a high-voltage arm resistor of the direct-current voltage transformer, 3 is a low-voltage arm resistor of the direct-current voltage transformer, 4 is a high-voltage arm capacitor of the direct-current voltage transformer, 5 is a low-voltage arm capacitor of the direct-current voltage transformer, 6 is a medium-voltage end of the direct-current voltage transformer, the device comprises a reference voltage divider, a reference voltage divider high-voltage arm capacitor, an alternating current differential measuring instrument, an alternating current excitation power supply and an alternating current excitation power supply, wherein 7 is a grounding end of a resistor branch of a low-voltage arm of a direct current voltage transformer, 8 is a grounding end of a capacitor branch of the low-voltage arm of the direct current voltage transformer, 9 is the reference voltage divider, 10 is the reference voltage divider high-voltage arm capacitor, 11 is the reference voltage divider low-voltage arm adjustable capacitor, 12 is the alternating current differential measuring instrument and 13 is the alternating current excitation power supply.
Detailed Description
The exemplary embodiments of the present application will now be described with reference to the accompanying drawings, however, the present application may be embodied in many different forms and is not limited to the examples described herein, which are provided to fully and completely disclose the present application and fully convey the scope of the application to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the application. In the drawings, like elements/components are referred to by like reference numerals.
Unless otherwise indicated, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, it will be understood that terms 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.
The application provides a method for measuring the capacitance value of a high-voltage arm of a direct-current voltage transformer, which is shown in fig. 1 and comprises the following steps:
connecting a reference capacitance voltage divider high-voltage arm capacitor and a reference capacitance voltage divider low-voltage arm adjustable capacitor in series to serve as a reference capacitance voltage divider;
the method comprises the steps that a middle voltage end of a reference capacitive voltage divider is connected with an alternating current differential measuring instrument and then connected with a middle voltage end of a direct current voltage transformer, and a high voltage end of the reference capacitive voltage divider is connected with a primary voltage terminal of a high voltage arm of the direct current voltage transformer to construct an alternating current balance bridge;
the method comprises the steps of simultaneously connecting the voltage output by an alternating current excitation power supply to a primary voltage terminal of a direct current voltage transformer and a high voltage end of a reference capacitor voltage divider;
and adjusting the AC balance bridge to ensure that the AC balance bridge reaches potential balance, acquiring measurement data, and determining the capacitance value of the high-voltage arm of the DC voltage transformer according to the measurement data.
The method for acquiring the measurement data specifically comprises the following steps:
measuring a capacitance value C2 of a low-voltage arm of the direct-current voltage transformer;
calculating a preset capacitance Cn2 of the reference capacitance divider low-voltage arm adjustable capacitor;
determining the optimal working frequency of the alternating current excitation power supply, controlling the alternating current excitation power supply to output test voltage according to the optimal working frequency, adjusting the capacitance Cn2 of the adjustable capacitor of the low-voltage arm of the reference capacitance divider until the indication value of the alternating current differential meter tends to zero, and recording the capacitance Cn2 of the adjustable capacitor of the low-voltage arm of the reference capacitance divider;
and determining a capacitance value C1 of the high-voltage arm of the direct-current voltage transformer according to the C2, cn1 and Cn2.
Wherein c1= (c2×cn1)/Cn 2.
Wherein, preset value of Cn 2=cn1×k, where K is the design value of the voltage dividing ratio of the dc voltage transformer.
Wherein, confirm the best operating frequency of the alternating current excitation power, include specifically:
according to the design value of the resistance value of the high-voltage arm of the direct-current voltage transformer and the design value of the capacitance value of the high-voltage arm of the direct-current voltage transformer, calculating the impedance value Z and the capacitance value X of the high-voltage arm of the direct-current voltage transformer C According to preset conditions, impedance value Z and capacitance value X C And calculating the optimal working frequency of the alternating current excitation power supply.
Wherein the preset condition is Z (approximately) X C 。
The medium voltage end of the direct current voltage transformer and the medium voltage end of the reference capacitive voltage divider form a differential measurement loop with the alternating current differential measurement instrument.
Wherein, test voltage includes: alternating test voltages of different magnitudes and frequencies.
The application is further illustrated by the following examples:
the structure and principle of the dc voltage transformer are shown in fig. 2 and 3, in which a primary dc voltage is applied to the high voltage terminal of the primary body 1 of the dc voltage transformer. The high-voltage arm of the direct-current voltage transformer is formed by connecting a high-voltage arm resistor 2 of the direct-current voltage transformer and a high-voltage arm capacitor 3 of the direct-current voltage transformer in series and parallel. The low-voltage arm of the direct-current voltage transformer is formed by connecting a low-voltage arm resistor 4 of the direct-current voltage transformer and a low-voltage arm capacitor 5 of the direct-current voltage transformer in parallel. The high-voltage arm and the low-voltage arm are connected in series to form a primary body 1 of the direct-current voltage transformer. The primary direct-current voltage is divided in series through the high-voltage arm and the low-voltage arm to generate medium-voltage, and the medium-voltage is output by the medium-voltage end 6 of the direct-current voltage transformer. The grounding end 7 of the low-voltage arm resistor branch of the direct-current voltage transformer and the grounding end 8 of the capacitor branch of the low-voltage arm of the direct-current voltage transformer are led out from the flange at the bottom of the direct-current voltage transformer and are grounded. As shown in fig. 1 and 2, the primary body of the dc voltage transformer is essentially a passive resistive-capacitive voltage divider network.
Fig. 4 is a schematic diagram of a capacitance value test of a primary high-voltage arm of the dc voltage transformer. The application adopts a direct-current voltage transformer primary body 1, a reference capacitance voltage divider 9, an alternating current differential measuring instrument 12 and an alternating current excitation power supply 13 to form a complete alternating current balance bridge, and the alternating current differential measuring instrument 12 is connected with a direct-current voltage transformer medium-voltage end 6 and a medium-voltage end of the reference capacitance voltage divider 9 to form a differential measuring loop. The ac excitation power supply 13 is connected to the dc voltage transformer primary body 1 and the high voltage end of the reference capacitive voltage divider 9, and provides excitation ac voltage to the ac balancing bridge. And adjusting the capacitance value of the low voltage arm 11 of the reference capacitive voltage divider to ensure that the AC balance bridge achieves potential balance, and obtaining the capacitance value of the high voltage arm of the DC voltage transformer through a calculation method.
As shown in fig. 4, the high-voltage arm resistor 2 and the high-voltage arm capacitor 3 of the direct-current voltage transformer belong to a parallel resistance-capacitance network, and the impedance value of the high-voltage arm of the direct-current voltage transformer is represented by the formula:
wherein: r is the high-voltage arm of the direct-current voltage transformerA direct current resistance value of the resistor 2; x is X C The capacitance resistance value of the high-voltage arm capacitor 3 of the direct-current voltage transformer;
and is also provided with
f is the working frequency of the alternating current excitation power supply 13, and C is the capacitance value of the high-voltage arm capacitor 3 of the direct current voltage transformer.
The application reduces the capacitance X in the impedance Z of the high voltage arm of the direct current voltage transformer by adjusting the working frequency of the alternating current excitation power supply 13 in order to furthest eliminate the influence of the resistance R of the high voltage arm resistor 2 of the direct current voltage transformer on the measurement of the capacitance C of the high voltage arm capacitor 3 of the direct current voltage transformer C The ratio of the resistance value R to Z (X) C At the moment, the alternating current balance bridge is equivalent to a pure capacitance balance bridge, so that the influence of the resistance value R of the high-voltage arm resistor 2 of the direct current voltage transformer on the measurement of the capacitance value C of the high-voltage arm capacitor 3 of the direct current voltage transformer is reduced to an acceptable range, and the precise measurement of the capacitance value of the high-voltage arm of the direct current voltage transformer is completed.
In normal test, the grounding end 7 of the low-voltage arm resistor branch of the direct-current voltage transformer is opened and suspended, and the grounding end 8 of the capacitor branch of the low-voltage arm of the direct-current voltage transformer is grounded.
According to a principle diagram of testing the capacitance value of a primary body high-voltage arm of the direct-current voltage transformer, the testing process is as follows:
1. disconnecting the grounding of the grounding end 8 of the capacitor branch of the low-voltage arm of the direct-current voltage transformer;
2. measuring a capacitance value C2 of the low-voltage arm capacitor 5 of the direct-current voltage transformer by using a capacitance meter;
3. restoring the grounding of the grounding end 8 of the capacitor branch of the low-voltage arm of the direct-current voltage transformer;
4. according to fig. 3, a direct-current voltage transformer primary body 1, a reference capacitance divider 9, an alternating-current differential measuring instrument 12 and an alternating-current excitation power supply 13 are connected;
5. the design value of the voltage division ratio K of the reference direct-current voltage transformer sample and the capacitance value Cn1 of the reference capacitance divider high-voltage arm capacitor 10 are referenced, the preset capacitance value Cn2 of the reference capacitance divider low-voltage arm adjustable capacitor 11 is calculated, and the calculation formula is as follows: cn2=cn1×the design value of the voltage division ratio K of the direct current voltage transformer;
6. according to the design value of the resistance value R of the high-voltage arm resistor 2 of the direct-current voltage transformer and the design value of the capacitance value of the high-voltage arm capacitor 3 of the direct-current voltage transformer, calculating the impedance value Z and the capacitance resistance value X of the high-voltage arm of the direct-current voltage transformer C According to Z.apprxeq.X C Calculating the optimal working frequency of the AC excitation power supply 13, outputting test voltage by the AC excitation power supply 13, adjusting the capacitance Cn2 of the reference capacitance divider low-voltage arm adjustable capacitor 11 according to the indication voltage of the AC differential meter 12 until the indication value of the AC differential meter 12 tends to zero, and recording the capacitance Cn2;
7. calculating a capacitance value C1 of the high-voltage arm capacitor 3 of the direct-current voltage transformer under the corresponding test voltage and frequency according to a formula C1= (C2×Cn1)/Cn2;
8. repeating the step 6 and the step 7, and sequentially completing the test of the capacitance value C1 of the high-voltage arm capacitor 3 of the direct-current voltage transformer under different amplitude test voltages;
the application is used for a sample machine example of a +/-800 kV direct-current voltage transformer, and design values of parameters of high and low voltage arms of the sample machine of the +/-800 kV direct-current voltage transformer are as follows: high voltage arm resistance 400mΩ, high voltage arm capacitor capacitance 412.5pF, low voltage arm resistance 100kΩ, low voltage arm capacitor capacitance 1.65uF, design voltage division ratio K:4000, the medium voltage 200V is designed, and various parameters are shown in fig. 6.
The parameters of the high-arm capacitor of the reference voltage divider are as follows: capacitance 200pF, tolerance 0.02%.
The parameters of the low-arm adjustable capacitor of the reference voltage divider are as follows: model: RX7-0 decimal capacitor box, tolerance 0.02%, capacitance value adjustment range: (0-10) × (0.0001+0.001+0.1+0.001+0.1) μf; model: RX7-7 decimal capacitor box, tolerance 0.02%, capacitance value adjustment range: (0-10). Times.0.1. Mu.F.
The alternating current differential measuring instrument adopts an alternating current voltage gear of a desk-top universal meter, and the model is as follows: DMM7510, resolution 712 bits, input impedance: 10MΩ//150pF, accuracy grade: 0.06% (10 Hz-20 kHz), minimum measurement range: 0.1uV to 100mV.
Ac excitation power supply: model ATG-2161, differential maximum output voltage 1600Vp-p (+ -800 Vp), working frequency DC-150 kHz (-3 dB).
The testing process comprises the following steps:
1. disconnecting the grounding end of the low-voltage arm resistor branch;
2. using the capacitance measurement function of the DMM7510 of the desk multimeter to measure the capacitance value C2 of the low-voltage arm capacitor, wherein the measured value is 1.6358uF;
3. the test loop is connected according to fig. 6;
4. according to the design value of the voltage division ratio K of the direct-current voltage transformer sample and the capacitance value Cn1 of the reference capacitance voltage divider high-voltage arm capacitor 10, calculating the preset capacitance value Cn2 of the reference capacitance voltage divider low-voltage arm adjustable capacitor 11 to be 800nF;
5. and calculating and setting the output frequency of the alternating current excitation power supply ATG-2161 to be 1000Hz according to the design value 400MΩ of the high-voltage arm resistance value of the direct current voltage transformer sample and the design value 412.5pF of the high-voltage arm capacitance value of the direct current voltage transformer.
6. Setting the output test voltage of an alternating current excitation power supply ATG-2161 as 100V, adjusting the capacitance Cn2 of an adjustable capacitor box RX7 of a low-voltage arm of a reference capacitance voltage divider until the indication value of an alternating current differential measuring instrument is less than 10uV, and recording the capacitance Cn2;
7. calculating a capacitance value C1 of the high-voltage arm capacitor at the corresponding test voltage and frequency according to the formula c1= (c2×cn1)/Cn 2;
8. repeating the step 6 and the step 7, and sequentially completing the test of the capacitance value C1 of the high-voltage arm capacitor under different amplitude test voltages; the test data are shown in table 1.
TABLE 1
The application improves the stability of the high-voltage arm capacitance value test and realizes the precise measurement of the high-voltage arm capacitance value of the direct-current voltage transformer.
The application adopts the principle of an alternating current balance bridge to construct a high-voltage alternating current balance bridge with high stability. By utilizing the direct difference measurement principle of the AC balance bridge, the test result is only related to the bridge arm voltage difference value and the phase of the AC balance bridge, so that common mode interference is greatly reduced, and the stability of the high-voltage arm capacitance value test is improved.
The application adopts the principle of an alternating current balance bridge to construct a high-voltage alternating current balance bridge with high stability, reduces the ratio of the capacitance resistance value to the resistance value in the impedance value of the high-voltage arm of the direct current voltage transformer by adjusting the output frequency of an alternating current excitation power supply until the impedance value is approximately equal to the capacitance resistance value, enables the alternating current balance bridge to be approximately equivalent to the pure capacitance balance bridge, reduces the influence of the resistance value of the high-voltage arm of the direct current voltage transformer on the measurement of the capacitance value of the high-voltage arm to an acceptable range, and realizes the precise measurement of the capacitance value of the high-voltage arm of the direct current voltage transformer.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. The scheme in the embodiment of the application can be realized by adopting various computer languages, such as object-oriented programming language Java, an transliteration script language JavaScript and the like.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (5)
1. A method for measuring a capacitance value of a high voltage arm of a direct current voltage transformer, the method comprising:
connecting a reference capacitance voltage divider high-voltage arm capacitor and a reference capacitance voltage divider low-voltage arm adjustable capacitor in series to serve as a reference capacitance voltage divider;
the method comprises the steps that a middle voltage end of a reference capacitive voltage divider is connected with an alternating current differential measuring instrument and then connected with a middle voltage end of a direct current voltage transformer, and a high voltage end of the reference capacitive voltage divider is connected with a primary voltage terminal of a high voltage arm of the direct current voltage transformer to construct an alternating current balance bridge;
the method comprises the steps of simultaneously connecting the voltage output by an alternating current excitation power supply to a primary voltage terminal of a direct current voltage transformer and a high voltage end of a reference capacitor voltage divider;
adjusting an alternating current balance bridge to enable the alternating current balance bridge to achieve potential balance, acquiring measurement data, and determining a capacitance value of a high-voltage arm of the direct current voltage transformer according to the measurement data;
the obtaining measurement data specifically includes:
measuring a capacitance value C2 of a low-voltage arm of the direct-current voltage transformer;
calculating a preset capacitance Cn2 of the reference capacitance divider low-voltage arm adjustable capacitor;
determining the optimal working frequency of the alternating current excitation power supply, controlling the alternating current excitation power supply to output test voltage according to the optimal working frequency, adjusting the capacitance Cn2 of the adjustable capacitor of the low-voltage arm of the reference capacitance divider until the indication value of the alternating current differential meter tends to zero, and recording the capacitance Cn2 of the adjustable capacitor of the low-voltage arm of the reference capacitance divider;
determining a capacitance value C1 of a high-voltage arm of the direct-current voltage transformer according to C2, cn1 and Cn2 recorded when the indication value of the alternating-current differential meter approaches zero;
the c1= (c2×cn1)/Cn 2.
2. The method of claim 1, wherein the preset value of Cn2 = Cn1 x K, where K is a design value of the voltage divider ratio of the dc voltage transformer.
3. The method according to claim 1, wherein determining the optimal operating frequency of the ac excitation power source comprises:
according to the design value of the resistance value of the high-voltage arm of the direct-current voltage transformer and the design value of the capacitance value of the high-voltage arm of the direct-current voltage transformer, calculating the impedance value Z and the capacitance value X of the high-voltage arm of the direct-current voltage transformer C According to preset conditions, impedance value Z and capacitance value X C Calculating an optimum for an ac excitation power sourceAn operating frequency.
4. A method according to claim 3, wherein the predetermined condition is z≡x C 。
5. The method of claim 1, the test voltage comprising: alternating test voltages of different magnitudes and frequencies.
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| CN202110819167.0A CN113702714B (en) | 2021-07-20 | 2021-07-20 | Method for measuring capacitance value of high-voltage arm of direct-current voltage transformer |
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