Excitation inrush current suppression analysis method and analysis device based on first half-wave residual magnetism measurement

Abstract

The present invention discloses an excitation inrush current suppression analysis method based on first half-wave residual magnetism measurement and an excitation inrush current suppression analysis device for realizing the method. The method comprises: performing closing operations at different angles on a demagnetized single-phase transformer, and measuring the first half-wave peak value of the inrush current after each closing, and obtaining a mapping relationship between the closing angle and the first half-wave peak value of the inrush current; performing an opening operation on the single-phase transformer at any opening angle to obtain the residual magnetism Φ to be measured. r After stabilization, the single-phase transformer of the present invention is closed according to the predetermined closing angle k and the peak value I of the first half-wave of the inrush current is measured. m Based on the mapping relationship between closing angle and first half-wave peak value of inrush current, determine the first half-wave peak value I m The corresponding closing angle α; calculate the residual magnetism Φ to be measured at the current opening angle r =Φ m cosα‑Φ m cosk,Φ m The invention can quickly analyze the residual magnetism at each opening angle with high analysis accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of transformer excitation inrush current suppression, and more specifically, relates to an excitation inrush current suppression analysis method and an analysis device based on first half-wave residual magnetism measurement. Background Art

[0002] The power transformer is an important power equipment that realizes energy transmission and transformation by means of electromagnetic induction. The transmission medium is mainly ferromagnetic material. Different ferromagnetic materials have different physical properties, but they all have saturation and hysteresis problems. When the transformer is out of operation from the power grid, the magnetic field of its core suddenly loses excitation. Due to the hysteresis effect, it will maintain a certain residual magnetism. The size and direction of the residual magnetism are mainly determined by the opening angle of the voltage. When closing the switch again, the residual magnetism of the power transformer core may cause the transformer to saturate the core instantly, generate a large amplitude excitation inrush current, cause the transformer protection to malfunction, and the transformer fails to close. At the same time, it will also cause an impact on the transformer, shortening the operating life of the transformer.

[0003] In recent years, research on the inrush current suppression technology of phase-selective control circuit breakers has gradually attracted attention. That is, the closing angle is controlled according to the residual magnetism state before closing, so that the pre-induced magnetic flux is equal to the residual magnetism of the transformer core, which can effectively avoid the large excitation inrush current caused by magnetic flux saturation. However, after the transformer is out of operation, the residual magnetism in the core is basically in a steady state and cannot be measured using the principle of electromagnetic induction. The core is a closed loop and cannot be measured by inserting a fluxmeter into the magnetic circuit. Most of the existing transformer core residual magnetism measurement methods have many uncertain factors and the feasibility of the measurement scheme is not high. Therefore, how to accurately and quantitatively measure the residual magnetism of the transformer core, and then obtain the optimal closing angle for phase-selective closing, and achieve a good inrush current suppression effect, is a problem worthy of attention. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides an excitation inrush current suppression analysis method and analysis device based on the first half-wave residual magnetism measurement, the purpose of which is to calculate the core residual magnetism at each opening angle in a more accurate manner.

[0005] To achieve the above object, according to one aspect of the present invention, a method for analyzing excitation inrush current suppression based on first half-wave residual magnetism measurement is provided, comprising:

[0006] Under the set voltage level, the demagnetized single-phase transformer is closed at different angles, and the peak value of the first half-wave of the inrush current after each closing is measured to obtain the mapping relationship between the closing angle and the peak value of the first half-wave of the inrush current.

[0007] At the same voltage level, the single-phase transformer is opened at any opening angle. The single-phase transformer after opening has the residual magnetism to be measured Φ rAfter stabilization, the single-phase transformer is closed at a predetermined closing angle k, and the peak value of the first half-wave of the inrush current after closing is measured. m ;

[0008] Based on the mapping relationship between closing angle and the peak value of the first half-wave of the inrush current, determine the peak value of the first half-wave of the inrush current I m The corresponding closing angle α;

[0009] Calculate the residual magnetism Φ to be measured at the current opening angle r =Φ m cosα-Φ m cosk,Φ m is the saturation flux of the single-phase transformer.

[0010] In one embodiment, the predetermined closing angle k = 90°, the residual magnetism to be measured at the current opening angle Φ r =Φ m cosα.

[0011] In one of the embodiments, it also includes: determining that the optimal closing angle for inrush current suppression at the current opening angle is α.

[0012] In one of the embodiments, when determining the mapping relationship between the closing angle and the peak value of the first half-wave of the inrush current, the closing angle is changed within the range of 0-180°.

[0013] In one of the embodiments, when determining the mapping relationship between the closing angle and the first half-wave peak value of the inrush current, a closing angle-first half-wave peak value curve of the inrush current is obtained by polynomial fitting.

[0014] In one embodiment, a 0-90° and 90°-180° segmented fitting method is adopted to obtain a 0-90° fitting curve and a 90°-180° fitting curve.

[0015] In one embodiment, when I m If the part that falls into the unfitted part between the two curves, the corresponding closing angle is considered to be 90°.

[0016] According to another aspect of the present invention, a magnetizing inrush current suppression analysis device based on first half-wave residual magnetism measurement is provided, which is used to analyze the residual magnetism Φ to be measured after the single-phase transformer is opened at any opening angle. r ,include;

[0017] A fitting unit is used to fit the closing angles of different closing operations on the demagnetized single-phase transformer and the first half-wave peak value of the inrush current under each closing angle, so as to obtain a mapping relationship between the closing angle and the first half-wave peak value of the inrush current;

[0018] A mapping unit is used to obtain the residual magnetism Φ to be measured. rThe predetermined closing angle k for the closing operation of the single-phase transformer and the first half-wave peak value I of the inrush current after the closing operation at the predetermined closing angle k m Based on the mapping relationship between closing angle and the peak value of the first half-wave of the inrush current, determine the peak value of the first half-wave of the inrush current I m The corresponding closing angle α;

[0019] The residual magnetism calculation unit is used to calculate the residual magnetism Φ to be measured at the current opening angle. r =Φ m cosα-Φ m cos k,Φ m is the saturation flux of the single-phase transformer.

[0020] In one embodiment, it also includes:

[0021] The optimal closing angle calculation unit is used to calculate the optimal closing angle for inrush current suppression under the current opening angle as arc(cosα-Φ m cos k).

[0022] In one of the embodiments, the predetermined closing angle k=90°, and the optimal closing angle for inrush current suppression at the current opening angle is α.

[0023] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0024] The present invention first obtains the peak value of the first half-wave of the inrush current caused by the closing angle without residual magnetic flux through multiple experiments, and obtains the mapping relationship between the closing angle and the first half-wave peak value of the inrush current through data processing. Then, the opening angle is selected, and the transformer is made to have residual magnetic flux Φ by the opening operation. r , the remanence Φ r The value of is the quantity to be determined. Then select a closing angle, that is, the preset closing angle k, for the residual magnetism Φ r The transformer continues to close the circuit breaker and measures the peak value of the first half-wave of the inrush current after closing. m . When the peak value of the first half wave of the surge current I m Substitute the mapping relationship between closing angle and first half-wave peak value of inrush current into the closing angle α without residual magnetic flux. In the present invention, the first half-wave peak value of inrush current caused by closing the circuit breaker under the two conditions of residual magnetic flux and no residual magnetic flux is used as a reference. When the two are the same, it is approximately considered that the corresponding bias magnetization is the same. For the residual magnetic flux Φ r The bias magnetism caused by closing the transformer is Φ r +Φ m cos k, the bias caused by closing the transformer without residual flux is Φ m cosα, then we can approximate that Φ r +Φ mcos k=Φ m cosα, and then calculate the residual magnetism Φ to be measured at the current opening angle r =Φ m cosα-Φ m cos k. The above method can quickly analyze the residual magnetism at each opening angle with high calculation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flowchart of the steps of an analysis method for suppressing excitation inrush current based on first half-wave residual magnetism measurement according to an embodiment;

[0026] Figure 2 An experimental wiring diagram of a test device of an embodiment;

[0027] Figure 3 Schematic diagram of the relationship between the closing angle and the first half-wave peak value of the inrush current according to an embodiment. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] like Figure 1 The figure is a flowchart of a method for analyzing excitation inrush current suppression based on first half-wave residual magnetism measurement in one embodiment, the method at least comprising the following steps:

[0030] Step S100: Under the set voltage level, the demagnetized single-phase transformer is closed at different angles, and the first half-wave peak value of the inrush current after each closing is measured to obtain a mapping relationship between the closing angle and the first half-wave peak value of the inrush current.

[0031] This step is to obtain the first half-wave peak value of the inrush current caused by the same demagnetized transformer at different closing angles, and determine the mapping relationship between the closing angle and the first half-wave peak value of the inrush current through a large amount of data without residual magnetism.

[0032] In one embodiment, the following can be constructed: Figure 2The device shown obtains the data required for analysis. After setting the voltage, the demagnetized single-phase transformer is closed at different angles. The closing angle can be controlled by a closing angle controller. The transformer is demagnetized before each closing so that it can be closed without residual magnetism. The first half-wave peak value of the inrush current after each closing is measured by an oscilloscope to obtain multiple combinations of closing angles and corresponding first half-wave peak values ​​of the inrush current. Through data processing, the mapping relationship between the closing angle and the first half-wave peak value of the inrush current is obtained.

[0033] In one embodiment, the peak value of the first half-wave of the inrush current at different closing angles within the range of 0-180° is measured by an oscilloscope, and the step length can be 10°. The smaller the step length, the more accurate the measurement result. In one embodiment, the obtained data is subjected to polynomial curve fitting to obtain a closing angle-first half-wave peak value curve of the inrush current. Furthermore, in order to reduce the influence of noise and zero drift on current measurement, a 0-90° and 90-180° segmented fitting method is adopted. The fitting results of the demagnetization closing angle-first half-wave peak value curve are shown in FIG. Figure 3 shown.

[0034] Step S200: Under the same voltage level, the single-phase transformer is opened at any opening angle. The single-phase transformer after opening has a residual magnetism Φ to be measured. r After stabilization, the single-phase transformer is closed at the predetermined closing angle k, and the peak value of the first half-wave of the inrush current after closing is measured. m .

[0035] The voltage in step S100 and step S200 remains the same. Select a trip angle, and control the circuit breaker to perform a trip operation according to the trip angle through a trip angle controller, so that the transformer obtains the residual magnetism Φ to be measured. r After a certain period of time, the transformer is closed by the closing angle controller according to the preset closing angle k, and the peak value of the first half-wave of the inrush current after closing is measured by the recorder. m .

[0036] Step S300: Based on the mapping relationship between the closing angle and the first half-wave peak value of the inrush current, determine the first half-wave peak value I m The corresponding closing angle α.

[0037] In one embodiment, it can be determined first that m Which section of the fitting curve does it belong to in the closing angle-inrush current first half-wave peak curve? Then, I m Substitute the fitting curve equation of the corresponding section to obtain the corresponding closing angle α. If the Im amplitude is extremely small and falls in the unfitted part between the two curves, it can be approximately considered that the corresponding closing angle is 90°.

[0038] Step S400: Calculate the residual magnetism Φ to be measured at the current opening angle r =Φm cosα-Φ m cosk,Φ m is the saturation flux of the single-phase transformer.

[0039] In the demagnetized state, the transformer residual magnetism is 0, and the bias magnetism is only the closing pre-induction flux Φ m cosα, the magnitude of the bias magnetism makes the peak value of the first half-wave of the inrush current in this case I1. Φ m is the saturation flux of a single-phase transformer. r In the case of , after a period of time, the circuit breaker is closed at the closing angle k, and the bias magnetic magnitude is Φ r +Φ m cosk, the magnitude of the bias magnetization makes the peak value of the first half-wave of the inrush current in this case equal to I2. In the present invention, the peak value of the first half-wave of the inrush current is used as the comparison object, and I1=I2 is obtained. r +Φ m cos k=Φ m cosα, and the residual magnetism Φ to be measured corresponding to the current opening angle is calculated r =Φ m cosα-Φ m In one embodiment, the preferred closing angle k = 90°, at which time the residual magnetism to be measured Φ r =Φ m cosα, the optimal closing angle for inrush current suppression at the current opening angle is α, so that the residual magnetic flux is exactly equal to the pre-induction magnetic flux.

[0040] Correspondingly, the present invention also discloses an excitation inrush current suppression analysis device based on the first half-wave residual magnetism measurement, which is used to analyze the residual magnetism Φ to be measured after the single-phase transformer is opened at any opening angle. r , which at least includes;

[0041] The fitting unit is used to fit the closing angles of different closing operations on the demagnetized single-phase transformer and the first half-wave peak value of the inrush current under each closing angle, and obtain the mapping relationship between the closing angle and the first half-wave peak value of the inrush current. Specifically, when the demagnetized single-phase transformer is closed at different angles and the first half-wave peak value of the inrush current after each closing is measured, each combination of the closing angle and the corresponding first half-wave peak value of the inrush current are input into the fitting unit to obtain the mapping relationship between the closing angle and the first half-wave peak value of the inrush current.

[0042] A mapping unit is used to obtain the residual magnetism Φ to be measured. r The predetermined closing angle k for the closing operation of the single-phase transformer and the first half-wave peak value I of the inrush current after the closing operation at the predetermined closing angle k m Based on the mapping relationship between closing angle and the peak value of the first half-wave of the inrush current, determine the peak value of the first half-wave of the inrush current I mSpecifically, when the transformer is opened, the transformer has a residual magnetism Φ to be measured. r After that, the single-phase transformer is closed according to the predetermined closing angle k, and the peak value of the first half-wave of the inrush current after closing is measured. m , the closing angle k and the measured inrush current first half-wave peak value I m Input mapping unit, the mapping unit determines the peak value of the first half wave of the inrush current I based on the mapping relationship between the closing angle and the first half wave peak value of the inrush current m The corresponding closing angle α.

[0043] The residual magnetism calculation unit is used to calculate the residual magnetism Φ to be measured at the current opening angle. r =Φ m cosα-Φ m cos k,Φ m is the saturation flux of the single-phase transformer.

[0044] In one embodiment, the analysis device further includes an optimal closing angle calculation unit for calculating the optimal closing angle for inrush current suppression under the current opening angle as arc(cosα-Φ m cos k). Furthermore, the closing angle k=90° is selected, and the optimal closing angle for inrush current suppression under the current opening angle is α.

[0045] The present invention first obtains the mapping relationship between the closing angle and the first half-wave peak value of the inrush current without residual magnetism. Then, the transformer is made to have residual magnetism Φ by opening the switch. r , the remanence Φ r The value of is the quantity to be determined. Then select the preset closing angle k, and for the residual magnetism Φ r The transformer continues to close the circuit breaker and measures the peak value of the first half-wave of the inrush current after closing. m . When the peak value of the first half wave of the surge current I m Substitute the mapping relationship between closing angle and first half-wave peak value of inrush current into the closing angle α without residual magnetic flux. In the present invention, the first half-wave peak value of inrush current caused by closing the circuit breaker under the two conditions of residual magnetic flux and no residual magnetic flux is used as a reference. When the two are the same, it is approximately considered that the corresponding bias magnetization is the same. For the residual magnetic flux Φ r The bias magnetism caused by closing the transformer is Φ r +Φ m cos k, the bias caused by closing the transformer without residual flux is Φ m cosα, then we can approximate that Φ r +Φ m cos k=Φ m cosα, and then calculate the residual magnetism Φ to be measured at the current opening angle r =Φ m cosα-Φm cos k. The above method can quickly analyze the residual magnetism at each opening angle with high calculation accuracy.

[0046] It will be easily understood by those skilled in the art that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A magnetizing inrush current suppression analysis method based on first half-wave residual magnetism measurement, characterized in that: include: Under the set voltage level, the demagnetized single-phase transformer is closed at different angles, and the peak value of the first half-wave of the inrush current after each closing is measured to obtain the mapping relationship between the closing angle and the peak value of the first half-wave of the inrush current. At the same voltage level, the single-phase transformer is opened at any opening angle. The single-phase transformer after opening has the residual magnetism to be measured Φ r After stabilization, the single-phase transformer is closed at a predetermined closing angle k, and the peak value of the first half-wave of the inrush current after closing is measured. m ; Based on the mapping relationship between closing angle and the peak value of the first half-wave of the inrush current, determine the peak value of the first half-wave of the inrush current I m The corresponding closing angle α; Calculate the residual magnetism Φ to be measured at the current opening angle r =Φ m cosα-Φ m cosk,Φ m is the saturation flux of the single-phase transformer.

2. The excitation inrush current suppression analysis method based on first half-wave residual magnetism measurement according to claim 1, characterized in that: The preset closing angle k = 90°, the residual magnetism to be measured at the current opening angle Φ r =Φ m cosα.

3. The excitation inrush current suppression analysis method based on first half-wave residual magnetism measurement according to claim 2 is characterized in that: Also includes: The optimal closing angle for inrush current suppression under the current opening angle is determined to be α.

4. The magnetizing inrush current suppression analysis method based on first half-wave residual magnetism measurement according to claim 1, characterized in that: When determining the mapping relationship between the closing angle and the peak value of the first half wave of the inrush current, the closing angle is changed within the range of 0-180°.

5. The excitation inrush current suppression analysis method based on first half-wave residual magnetism measurement according to claim 4 is characterized in that: When determining the mapping relationship between the closing angle and the first half-wave peak value of the inrush current, a closing angle-first half-wave peak value curve of the inrush current is obtained by polynomial fitting.

6. The excitation inrush current suppression analysis method based on first half-wave residual magnetism measurement according to claim 5, characterized in that: The 0-90° and 90°-180° segmented fitting methods are adopted to obtain the 0-90° fitting curve and the 90°-180° fitting curve.

7. The excitation inrush current suppression analysis method based on first half-wave residual magnetism measurement according to claim 6, characterized in that: When I m If the part that falls into the unfitted part between the two curves, the corresponding closing angle is considered to be 90°.

8. An excitation inrush current suppression analysis device based on the first half-wave residual magnetism measurement, used to analyze the residual magnetism Φ to be measured after the single-phase transformer is opened at any opening angle r , characterized in that, include; A fitting unit is used to fit the closing angles of different closing operations on the demagnetized single-phase transformer and the first half-wave peak value of the inrush current under each closing angle, so as to obtain a mapping relationship between the closing angle and the first half-wave peak value of the inrush current; A mapping unit is used to obtain the residual magnetism Φ to be measured. r The predetermined closing angle k for the closing operation of the single-phase transformer and the first half-wave peak value I of the inrush current after the closing operation at the predetermined closing angle k m Based on the mapping relationship between closing angle and the peak value of the first half-wave of the inrush current, determine the peak value of the first half-wave of the inrush current I m The corresponding closing angle α; The residual magnetism calculation unit is used to calculate the residual magnetism Φ to be measured at the current opening angle. r =Φ m cosα-Φ m cos k,Φ m is the saturation flux of the single-phase transformer.

9. The excitation inrush current suppression analysis device based on first half-wave residual magnetism measurement according to claim 8, characterized in that: Also includes: The optimal closing angle calculation unit is used to calculate the optimal closing angle for inrush current suppression under the current opening angle as arc(cosα-Φ m cos k).

10. The excitation inrush current suppression analysis device based on first half-wave residual magnetism measurement according to claim 9, characterized in that: The preset closing angle k=90°, and the optimal closing angle for inrush current suppression at the current opening angle is α.

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