CN113702714A - Method for measuring capacitance value of high-voltage arm of direct-current voltage transformer - Google Patents
Method for measuring capacitance value of high-voltage arm of direct-current voltage transformer Download PDFInfo
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Abstract
The invention 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 power transmission engineering. The method comprises the following steps: connecting a reference capacitive voltage divider high-voltage arm capacitor and a reference capacitive voltage divider low-voltage arm adjustable capacitor in series to serve as a reference capacitive voltage divider; connecting the medium voltage end of a reference capacitive voltage divider into an alternating current differential measuring instrument, then connecting the medium voltage end of a direct current voltage transformer, and connecting the high voltage end of the reference capacitive voltage divider into a primary voltage terminal of a high voltage arm of the direct current voltage transformer to construct an alternating current balance bridge; simultaneously connecting the voltage output by the alternating current excitation power supply to a primary voltage terminal of a direct current voltage transformer and a high voltage end of a reference capacitive voltage divider; and adjusting the balance bridge to enable the balance bridge to reach potential balance, 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 invention improves the stability of the capacitance value test of the high-voltage arm.
Description
Technical Field
The present invention relates to the field of dc transmission engineering, and more particularly, to a method for measuring a capacitance value of a high-voltage arm of a dc 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 mainly has the functions of converting primary direct-current high voltage of polar lines to be measured into low-voltage signals 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 a resistance-capacitance voltage division principle, a high-voltage arm of the direct current voltage transformer mainly bears rated voltage and transient overvoltage on a polar line, the direct current voltage transformer is similar to a combination of a resistor and a capacitor with huge sizes, the height size of the primary body part of the direct current voltage transformer is different from several meters to tens of meters according to different voltage grades, and the method and the capability difficulty exist in accurately measuring the resistance-capacitance parameters of the primary body of the direct current voltage transformer.
At present, in a direct current transmission project, 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 resistance-capacitance voltage divider, and is actually a resistance-capacitance voltage divider. The primary high voltage and the secondary medium voltage both take the grounding end of the low-voltage arm as an electrical reference point, and are typical voltage division type high-voltage measuring equipment. Wherein, its high-voltage arm is connected in series and parallelly by a plurality of high-voltage resistor and high-voltage capacitor and constitutes, and once high voltage is mainly born by the high-voltage arm.
The parallel capacitor has two main functions in the direct current 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 the primary transient process by utilizing the characteristic that the voltages at two ends of the capacitor are kept unchanged in the transient process.
2. The frequency characteristic is improved, the resistance-capacitance voltage divider has the frequency response characteristic from direct current to high frequency, the impedance characteristic of the high-voltage arm and the low-voltage arm of the resistance-capacitance voltage divider is mainly matched, the parallel capacitor plays an important role in 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 the high-voltage arm resistor and the low-voltage arm capacitor, however, accurate measurement of the capacitance value of the high-voltage arm of the direct current voltage transformer is still a difficult problem, and an effective and reliable test method and a test instrument are not available so far to accurately measure the capacitance of the high-voltage arm of the direct current voltage transformer.
The main problems are as follows:
1. and (4) the anti-interference problem is solved. 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 of electronic components and the like, the test level is generally at a voltage level, the test current is generally at a nA level to a mA level, and when the conventional RLC bridge is used for testing the high-voltage arm capacitance of a direct-current voltage transformer, the conventional RLC bridge is easily interfered by an electromagnetic environment and has unreliable measurement accuracy.
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 connecting a plurality of unit resistors and capacitors in series and in parallel, belong to a typical passive RC network and cannot be disconnected physically, the design value of the resistance value of the high-voltage arm is generally between hundreds of M omega and G omega, the insulation resistance of the high-voltage arm capacitor is about tens of G omega, the difference of the order of magnitude of the two resistance value parameters is close to that of the high-voltage arm resistor, and in the 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 inaccuracy of the capacitance testing result is caused.
Disclosure of Invention
In order to solve the above problem, the present invention provides a method for measuring a capacitance value of a high-voltage arm of a dc voltage transformer, comprising:
connecting a reference capacitive voltage divider high-voltage arm capacitor and a reference capacitive voltage divider low-voltage arm adjustable capacitor in series to serve as a reference capacitive voltage divider;
connecting the medium voltage end of a reference capacitive voltage divider into an alternating current differential measuring instrument, then connecting the medium voltage end of a direct current voltage transformer, and connecting the high voltage end of the reference capacitive voltage divider into a primary voltage terminal of a high voltage arm of the direct current voltage transformer to construct an alternating current balance bridge;
simultaneously connecting the voltage output by the alternating current excitation power supply to a primary voltage terminal of a direct current voltage transformer and a high voltage end of a reference capacitive voltage divider;
and adjusting the alternating current balance bridge to enable the alternating current balance bridge to reach potential balance, acquiring measurement data, and determining the capacitance value of the high-voltage arm of the direct current voltage transformer according to the measurement data.
Optionally, the obtaining of the measurement data specifically includes:
measuring a capacitance value C2 of a low-voltage arm of the direct-current voltage transformer;
calculating a preset capacitance value Cn2 of a low-voltage arm adjustable capacitor of the reference capacitive divider;
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 value Cn2 of the adjustable capacitor of the low-voltage arm of the reference capacitive voltage divider until the indication value of the alternating-current difference measuring instrument tends to zero, and recording the capacitance value Cn2 of the adjustable capacitor of the low-voltage arm of the reference capacitive voltage divider;
and determining the capacitance value C1 of the high-voltage arm of the direct-current voltage transformer according to C2, Cn1 and Cn 2.
Alternatively, C1 ═ (C2 × Cn1)/Cn 2.
Optionally, the preset value of Cn2 is Cn1 × K, where K is a design value of the voltage division ratio of the dc voltage transformer.
Optionally, determining an optimal operating frequency of the ac excitation power supply specifically includes:
calculating the impedance value Z and the capacitive reactance value X of the high-voltage arm of the direct-current voltage transformer 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 transformerCAccording to the preset conditions, the impedance value Z and the capacitive reactance value XCAnd calculating the optimal working frequency of the alternating current excitation power supply.
Optionally, the preset condition is that Z is approximately equal to XC。
Optionally, the medium voltage end of the dc voltage transformer, the medium voltage end of the reference capacitive voltage divider, and the ac difference meter form a difference measurement loop.
Optionally, the test voltage comprises: alternating test voltages of different amplitudes and frequencies.
The invention improves the stability of the capacitance value test of the high-voltage arm and realizes the precise measurement of the capacitance value of the high-voltage arm of the direct-current voltage transformer.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
fig. 2 is a schematic structural diagram of a primary body of a typical dc voltage transformer in an embodiment of the present invention;
FIG. 3 is a schematic diagram of a primary bulk circuit of an exemplary DC voltage transformer in accordance with an embodiment of the present invention;
FIG. 4 is a schematic diagram of a capacitance value test of a high-voltage arm of a primary body of the DC voltage transformer in the embodiment of the invention;
FIG. 5 is a schematic diagram of an example of a + -800 kV DC voltage transformer in an embodiment of the invention;
FIG. 6 is a wiring diagram of an exemplary capacitance value test of a high-voltage arm of a primary body of a +/-800 kV direct-current voltage transformer in the embodiment of the invention;
the device comprises a primary body of the direct-current voltage transformer, a high-voltage arm resistor of the direct-current voltage transformer, a low-voltage arm resistor of the direct-current voltage transformer, a capacitor of the direct-current voltage transformer, a low-voltage arm capacitor of the direct-current voltage transformer, a medium-voltage end of the direct-current voltage transformer, a resistance branch grounding end of the low-voltage arm of the direct-current voltage transformer, a capacitance branch grounding end of the low-voltage arm of the direct-current voltage transformer, a reference capacitance divider, a high-voltage arm capacitor of the reference capacitance divider, an adjustable capacitor of the low-voltage arm of the reference capacitance divider, an alternating-current differential measuring instrument and an alternating-current excitation power supply, wherein the primary body of the direct-current voltage transformer is 1, the high-voltage arm resistor of the direct-current voltage transformer is 2, the low-voltage arm resistor of the direct-current voltage transformer is 3, the high-voltage arm capacitor of the direct-current voltage transformer, the reference capacitance divider is 5, the medium-voltage arm capacitor of the direct-voltage arm resistor of the direct-current voltage transformer, the direct-current differential measuring instrument is 7, the direct-current differential measuring instrument, the alternating-voltage differential measuring instrument is 8, and the reference capacitance voltage differential measuring instrument.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention 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 invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, 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 invention belongs. Further, it will be 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.
The invention provides a method for measuring a capacitance value of a high-voltage arm of a direct-current voltage transformer, as shown in fig. 1, comprising the following steps:
connecting a reference capacitive voltage divider high-voltage arm capacitor and a reference capacitive voltage divider low-voltage arm adjustable capacitor in series to serve as a reference capacitive voltage divider;
connecting the medium voltage end of a reference capacitive voltage divider into an alternating current differential measuring instrument, then connecting the medium voltage end of a direct current voltage transformer, and connecting the high voltage end of the reference capacitive voltage divider into a primary voltage terminal of a high voltage arm of the direct current voltage transformer to construct an alternating current balance bridge;
simultaneously connecting the voltage output by the alternating current excitation power supply to a primary voltage terminal of a direct current voltage transformer and a high voltage end of a reference capacitive voltage divider;
and adjusting the alternating current balance bridge to enable the alternating current balance bridge to reach potential balance, acquiring measurement data, and determining the capacitance value of the high-voltage arm of the direct current voltage transformer according to the measurement data.
Wherein, 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 value Cn2 of a low-voltage arm adjustable capacitor of the reference capacitive divider;
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 value Cn2 of the adjustable capacitor of the low-voltage arm of the reference capacitive voltage divider until the indication value of the alternating-current difference measuring instrument tends to zero, and recording the capacitance value Cn2 of the adjustable capacitor of the low-voltage arm of the reference capacitive voltage divider;
and determining the capacitance value C1 of the high-voltage arm of the direct-current voltage transformer according to C2, Cn1 and Cn 2.
Wherein, C1 ═ C2 × Cn1)/Cn 2.
The preset value of the Cn2 is Cn1 multiplied by K, wherein K is a design value of the voltage division ratio of the direct-current voltage transformer.
The method for determining the optimal working frequency of the alternating current excitation power supply specifically comprises the following steps:
calculating the impedance value Z and the capacitive reactance value X of the high-voltage arm of the direct-current voltage transformer 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 transformerCAccording to the preset conditions, the impedance value Z and the capacitive reactance value XCAnd calculating the optimal working frequency of the alternating current excitation power supply.
Wherein the preset condition is that Z is approximately equal to XC。
The medium voltage end of the direct current voltage transformer, the medium voltage end of the reference capacitive voltage divider and the alternating current difference meter form a difference measuring loop.
Wherein, test voltage includes: alternating test voltages of different amplitudes and frequencies.
The invention 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 a high voltage terminal of a primary body 1 of the dc voltage transformer. The high-voltage arm of the direct-current voltage transformer is formed by connecting a direct-current voltage transformer high-voltage arm resistor 2 and a direct-current voltage transformer high-voltage arm capacitor 3 in series and in parallel. The low-voltage arm of the direct-current voltage transformer is formed by connecting a direct-current voltage transformer low-voltage arm resistor 4 and a direct-current voltage transformer low-voltage arm capacitor 5 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 by the high-low voltage arms in series to generate medium voltage, and the medium voltage is output by a medium voltage end 6 of the direct current voltage transformer. And a low-voltage arm resistance branch grounding end 7 of the direct-current voltage transformer and a low-voltage arm capacitance branch grounding end 8 of the direct-current voltage transformer are led out from a bottom flange 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 resistor-capacitor voltage divider network.
Fig. 4 is a schematic diagram of a capacitance value test of a high-voltage arm of a primary body of a direct-current voltage transformer. The invention adopts a primary body 1 of a direct current voltage transformer, a reference capacitive voltage divider 9, an alternating current difference meter 12 and an alternating current excitation power supply 13 to form a set of complete alternating current balance bridge, and the alternating current difference meter 12 is connected with a medium voltage end 6 of the direct current voltage transformer and a medium voltage end of the reference capacitive voltage divider 9 to form a difference measuring loop. The AC excitation power supply 13 is connected to the primary body 1 of the DC voltage transformer and the high-voltage end of the reference capacitive voltage divider 9, and provides excitation AC voltage for the AC balance bridge. And adjusting the capacitance value of the low-voltage arm 11 of the reference capacitive voltage divider to enable the alternating-current balance bridge to reach potential balance, and obtaining the capacitance value of the high-voltage arm of the direct-current voltage transformer by a calculation method.
As shown in fig. 4, the dc voltage transformer high-voltage arm resistor 2 and the dc voltage transformer high-voltage arm capacitor 3 belong to a parallel resistance-capacitance network, and the impedance value of the dc voltage transformer high-voltage arm is represented by the formula:
wherein: r is the direct current resistance value of the high-voltage arm resistor 2 of the direct current voltage transformer; xCThe capacitance reactance value of the high-voltage arm capacitor 3 of the direct-current voltage transformer is obtained;
and is
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 invention aims to eliminate 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 to the maximum extent, and reduces the capacitive reactance value X in the high-voltage arm impedance value Z of the direct-current voltage transformer by adjusting the working frequency of the alternating-current excitation power supply 13CThe ratio of the resistance value R to the resistance value R until Z is approximately equal to XCAt 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.
When the low-voltage arm resistance branch circuit of the direct-current voltage transformer is normally tested, the grounding end 7 of the low-voltage arm resistance branch circuit of the direct-current voltage transformer is open and suspended, and the grounding end 8 of the low-voltage arm capacitance branch circuit of the direct-current voltage transformer is grounded.
According to a primary body high-voltage arm capacitance value test schematic diagram of the direct-current voltage transformer, the test process is as follows:
1. disconnecting the grounding end 8 of the low-voltage arm capacitor branch of the direct-current voltage transformer from the ground;
2. measuring the 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 low-voltage arm capacitor branch of the direct-current voltage transformer;
4. according to the figure 3, a primary body 1 of the direct current voltage transformer, a reference capacitive voltage divider 9, an alternating current difference meter 12 and an alternating current excitation power supply 13 are connected;
5. and calculating a preset capacitance value Cn2 of the reference capacitive voltage divider low-voltage arm adjustable capacitor 11 by referring to the design value of the voltage division ratio K of the direct-current voltage transformer test sample and the capacitance value Cn1 of the reference capacitive voltage divider high-voltage arm capacitor 10, wherein the calculation formula is as follows: cn2 is designed value of Cn1 multiplied by the voltage division ratio K of the direct current voltage transformer;
6. calculating the impedance value Z and the capacitive reactance value X of the high-voltage arm of the direct-current voltage transformer 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 transformerCAccording to Z ≈ XCCalculating the optimal working frequency of the AC excitation power supply 13, outputting a test voltage by the AC excitation power supply 13, adjusting the capacitance Cn2 of the reference capacitive voltage divider low-voltage arm adjustable capacitor 11 according to the indicating value voltage of the AC difference meter 12 until the indicating value of the AC difference meter 12 tends to zero, and recording a capacitance Cn 2;
7. calculating the capacitance value C1 of the dc voltage transformer high-voltage arm capacitor 3 corresponding to the test voltage and frequency according to the formula C1 ═ C2 × Cn1)/Cn 2;
8. repeating the step 6 and the step 7, and sequentially testing the capacitance value C1 of the high-voltage arm capacitor 3 of the direct-current voltage transformer under different amplitude test voltages;
the invention is used for a sample machine example of a +/-800 kV direct current voltage transformer, and the design values of all 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 value 400M omega, high-voltage arm capacitor capacitance value 412.5pF, low-voltage arm resistance value 100K omega, low-voltage arm capacitor capacitance value 1.65uF, design voltage divider ratio K: 4000 medium voltage 200V is designed, and the parameters are shown in fig. 6.
The parameters of the high arm capacitor of the reference voltage divider are as follows: capacitance value 200pF, tolerance 0.02%.
The parameters of the low-arm tunable capacitor of the reference voltage divider are as follows: the model is as follows: RX7-0 decimal capacitor box, tolerance 0.02%, capacitance value regulating range: (0-10) × (0.0001+0.001+0.1+0.001+0.1) μ F; the model is as follows: RX7-7 decimal capacitor box, tolerance 0.02%, capacitance value regulating range: (0-10). times.0.1. mu.F.
The AC difference meter adopts the AC voltage grade, model of the desk multimeter: DMM7510, resolution 712 bits, input impedance: 10M Ω//150pF, accuracy grade: 0.06% (10 Hz-20 kHz), minimum measurement range: 0.1uV to 100 mV.
An alternating current excitation power supply: the model ATG-2161, the differential maximum output voltage 1600Vp-p (+ -800 Vp), the working frequency DC-150 kHz (-3 dB).
The testing process comprises the following steps:
1. disconnecting the grounding end of the low-voltage arm resistance branch;
2. measuring the capacitance value C2 of the low-voltage arm capacitor by using the capacitance measuring function of the DMM7510 of the desk multimeter, wherein the measured value is 1.6358 uF;
3. connecting the test loop according to fig. 6;
4. calculating a preset capacitance value Cn2 of a reference capacitive voltage divider low-voltage arm adjustable capacitor 11 to be 800nF according to a design value of a voltage division ratio K of a direct-current voltage transformer test sample and a capacitance value Cn1 of a reference capacitive voltage divider high-voltage arm capacitor 10;
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 of the resistance value of the high-voltage arm of the direct current voltage transformer test sample of 400M omega and the design value of the capacitance value of the high-voltage arm of the direct current voltage transformer of 412.5 pF.
6. Setting the output test voltage of an alternating current excitation power supply ATG-2161 as 100V, adjusting the capacitance Cn2 of the reference capacitive voltage divider low-voltage arm adjustable capacitor box RX7 until the indication value of the alternating current differential measuring instrument is less than 10uV, and recording the capacitance Cn 2;
7. calculating the capacitance value C1 of the high-voltage arm capacitor at the corresponding test voltage and frequency according to the formula C1 ═ C2 xcn 1)/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 invention improves the stability of the capacitance value test of the high-voltage arm and realizes the precise measurement of the capacitance value of the high-voltage arm of the direct-current voltage transformer.
The invention adopts the principle of the alternating current balance bridge to construct the high-voltage alternating current balance bridge with high stability. By utilizing the direct difference measurement principle of the alternating-current balance bridge, the test result is only related to the bridge arm voltage difference value and the phase of the alternating-current balance bridge, so that the common-mode interference is greatly reduced, and the stability of the high-voltage arm capacitance value test is improved.
The invention adopts the AC balance bridge principle to construct a high-voltage AC balance bridge with high stability, reduces the ratio of a capacitance value to a resistance value in the impedance value of the high-voltage arm of the DC voltage transformer by adjusting the output frequency of an AC excitation power supply until the impedance value is approximately equal to the capacitance value, so that the AC balance bridge is approximately equivalent to a pure capacitance balance bridge, the influence of the resistance value of the high-voltage arm of the DC voltage transformer on the measurement of the capacitance value of the high-voltage arm is reduced to an acceptable range, and the precise measurement of the capacitance value of the high-voltage arm of the DC voltage transformer is realized.
As will be appreciated by one skilled in the art, 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 implemented by adopting various computer languages, such as object-oriented programming language Java and transliterated scripting language JavaScript.
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 flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams 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 the 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. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.
Claims (8)
1. A method for measuring a capacitance value of a high voltage arm of a dc voltage transformer, the method comprising:
connecting a reference capacitive voltage divider high-voltage arm capacitor and a reference capacitive voltage divider low-voltage arm adjustable capacitor in series to serve as a reference capacitive voltage divider;
connecting the medium voltage end of a reference capacitive voltage divider into an alternating current differential measuring instrument, then connecting the medium voltage end of a direct current voltage transformer, and connecting the high voltage end of the reference capacitive voltage divider into a primary voltage terminal of a high voltage arm of the direct current voltage transformer to construct an alternating current balance bridge;
simultaneously connecting the voltage output by the alternating current excitation power supply to a primary voltage terminal of a direct current voltage transformer and a high voltage end of a reference capacitive voltage divider;
and adjusting the alternating current balance bridge to enable the alternating current balance bridge to reach potential balance, acquiring measurement data, and determining the capacitance value of the high-voltage arm of the direct current voltage transformer according to the measurement data.
2. The method according to claim 1, wherein the acquiring of the measurement data specifically comprises:
measuring a capacitance value C2 of a low-voltage arm of the direct-current voltage transformer;
calculating a preset capacitance value Cn2 of a low-voltage arm adjustable capacitor of the reference capacitive divider;
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 value Cn2 of the adjustable capacitor of the low-voltage arm of the reference capacitive voltage divider until the indication value of the alternating-current difference measuring instrument tends to zero, and recording the capacitance value Cn2 of the adjustable capacitor of the low-voltage arm of the reference capacitive voltage divider;
and determining the capacitance value C1 of the high-voltage arm of the direct-current voltage transformer according to C2, Cn1 and Cn 2.
3. The method of claim 2, the C1 ═ (C2 xcn 1)/Cn 2.
4. The method of claim 2, the preset value of Cn2 ═ Cn1 xk, where K is a design value of dc voltage transformer voltage divider ratio.
5. The method according to claim 2, wherein the determining the optimal operating frequency of the ac excitation power supply specifically comprises:
calculating the impedance value Z and the capacitive reactance value X of the high-voltage arm of the direct-current voltage transformer 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 transformerCAccording to the preset conditions, the impedance value Z and the capacitive reactance value XCAnd calculating the optimal working frequency of the alternating current excitation power supply.
6. The method of claim 5, the preset condition being Z ≈ XC。
7. The method of claim 1, wherein the medium voltage terminal of the dc voltage transformer, the medium voltage terminal of the reference capacitive divider, and the ac differentiator form a differentiator loop.
8. The method of claim 2, the testing voltage, comprising: alternating test voltages of different amplitudes and frequencies.
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