Current transformer saturation characteristic test platform and method with superimposed DC component

Abstract

The present invention relates to a current transformer saturation characteristic test platform and method with a superimposed DC component, and its technical characteristics are: the test platform includes a DC constant current source, an AC current source and an oscilloscope, the DC constant current source and the AC current source are connected to the primary side of the current transformer, the DC constant current source is used to apply DC current excitation to the current transformer, and the AC current source outputs AC current to the current transformer; the secondary side of the current transformer is connected to the oscilloscope, and the oscilloscope is used to record and output the secondary information of the current transformer. The present invention can effectively analyze the influence of different DC components on the saturation characteristics of electromagnetic current transformers, and can be used to guide the selection, operation and maintenance strategies of electromagnetic current transformers, thereby preventing the occurrence of electromagnetic current transformer failures, improving the reliability of equipment safety and power grid safety, and improving the safe and reliable operation level of the power grid.

Description

Technical Field

[0001] The invention belongs to the technical field of current transformers, and in particular to a current transformer saturation characteristic test platform and method with a superimposed direct current component. Background Art

[0002] The current transformer is a device that converts the large current on the primary side into the small current on the secondary side for measurement based on the principle of electromagnetic induction. The current transformer consists of a closed iron core and windings. Its working state is close to short circuit, and it plays the role of current conversion and electrical isolation. It is an important device in the power system. When the power grid is short-circuited, operated overvoltage, lightning overvoltage, etc., a certain DC component will be generated in the system, and with the construction of new power systems, a certain DC component or harmonics will be introduced into the power grid. When the DC component is superimposed on the AC current on the primary side, since the DC component does not have primary or secondary induction, it can be considered that all of it is used for excitation. At this time, it will quickly cause the transformer to be magnetically saturated and transient saturation will occur. This situation may cause the AC waveform to clip, causing the secondary current waveform to be distorted. In severe cases, it will affect the accuracy of the relay protection action, causing protection malfunctions, and threatening the safe and stable operation of the power system. Therefore, how to accurately analyze the impact of the superimposed DC component on the current transformer is an urgent problem that needs to be solved. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide a current transformer saturation characteristic testing platform and method for a superimposed DC component which has a reasonable design and can accurately analyze the influence of the superimposed DC component on the current transformer.

[0004] The present invention solves the existing technical problems by adopting the following technical solutions:

[0005] A current transformer saturation characteristic test platform with a superimposed DC component comprises a DC constant current source, an AC current source and an oscilloscope, wherein the DC constant current source and the AC current source are connected to the primary side of the current transformer, the DC constant current source is used to apply DC current excitation to the current transformer, and the AC current source outputs AC current to the current transformer; the secondary side of the current transformer is connected to the oscilloscope, and the oscilloscope is used to record and output secondary information of the current transformer.

[0006] Moreover, the current transformer is an electromagnetic current transformer.

[0007] Moreover, the output current of the AC current source is 0-5000A.

[0008] A testing method for a current transformer saturation characteristic testing platform with a superimposed DC component comprises the following steps:

[0009] Step 1: When no DC current is applied to the primary side of the current transformer, an AC current is applied to the primary side to measure the primary AC current value I at which the current transformer is saturated. ABH0 ;

[0010] Step 2, applying a given value of direct current to the primary side of the current transformer, and applying an alternating current to the primary side;

[0011] Step 3: Control the AC current source to gradually increase the output AC current, observe the secondary current waveform through the oscilloscope on the secondary side, and record the primary AC current value when the current waveform is distorted to obtain the primary AC current value I when the current transformer is saturated when there is a DC component in the primary winding of the current transformer. ABHi ;

[0012] Step 4, comparing the primary AC current value of the current transformer saturated obtained in step 1 with the primary AC current value of the current transformer saturated obtained in step 3, and calculating the saturation current bias rate f of the current transformer under the DC component;

[0013] Step 5, repeating steps 2 to 4, measuring the saturated primary AC current value when different DC components exist in the primary winding of the current transformer, and then obtaining the variation curve of the primary saturation current of the current transformer with the DC current component, and the variation curve of the saturation current bias rate.

[0014] Moreover, the current transformer is an electromagnetic current transformer.

[0015] Moreover, the saturation current bias rate f of the current transformer under the DC component is obtained by the following calculation formula:

[0016] f=(I ABH0- I ABHi ) / I ABH0 *100%.

[0017] The advantages and positive effects of the present invention are:

[0018] The present invention connects a DC constant current source and an AC current source to the primary side of a current transformer, applies DC current excitation to the current transformer through the DC constant current source, outputs an AC current of 0 to 5000A to the current transformer through the AC current source, and records and displays secondary current and voltage information through a secondary connected current waveform oscilloscope, thereby being able to effectively analyze the influence of different DC components on the saturation characteristics of the electromagnetic current transformer, and can be used to guide the selection, operation and maintenance strategies of the electromagnetic current transformer, thereby preventing the occurrence of electromagnetic current transformer failures, improving the reliability of equipment safety and power grid safety, and improving the safe and reliable operation level of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a wiring schematic diagram of a current transformer saturation characteristic test platform with a superimposed DC component of the present invention;

[0020] Figure 2 The present invention is a flow chart of the current transformer saturation characteristic test method with superimposed DC component. DETAILED DESCRIPTION

[0021] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0022] The present invention proposes a current transformer saturation characteristic test platform with superimposed DC component, such as Figure 1 As shown, it includes a DC constant current source, an AC current source and an oscilloscope. In this embodiment, the current transformer to be tested is an electromagnetic current transformer, and the primary side of the electromagnetic current transformer to be tested is connected to a DC constant current source and an AC current source, the DC constant current source is used to apply DC current excitation to the electromagnetic current transformer, and the AC current source can output an AC current of 0 to 5000A to the electromagnetic current transformer; the secondary side of the electromagnetic current transformer is connected to an oscilloscope, and the oscilloscope can record secondary current information and output current waveforms and voltage waveforms.

[0023] Based on the above-mentioned current transformer saturation characteristic test platform with superimposed DC component, the present invention also proposes a current transformer saturation characteristic test method with superimposed DC component, such as Figure 2 As shown, the following steps are included:

[0024] Step 1: When no DC current is applied to the primary side of the electromagnetic current transformer, an AC current is applied to the primary side to measure the primary AC current value I at which the current transformer is saturated. ABH0 .

[0025] Step 2: Apply a given DC current I to the primary side of the electromagnetic current transformer. DC , and at the same time apply AC current excitation I on the primary side AC .

[0026] Step 3: Control the AC current source to gradually increase the output AC current, and observe the secondary current waveform through the current waveform oscilloscope on the secondary side. When the current waveform is distorted (clipping, peak wave, etc.), record the primary AC current value I ABH , indicating that the current transformer has been saturated at this time, so when there is a DC component I in the primary winding of the electromagnetic current transformer DC When the current transformer is saturated, the primary AC current value I ABHi .

[0027] Step 4: Compare the primary AC current value of the current transformer saturated obtained in step 1 with the primary AC current value of the current transformer saturated obtained in step 3, and calculate the saturation current bias rate f of the current transformer under the DC component.

[0028] In this step, the saturation current bias rate of the current transformer under the DC component is calculated by the following formula:

[0029] f=(I ABH0- I ABHi ) / I ABH0 *100%.

[0030] Step 5: Repeat steps 2 to 4 to measure the different DC components I in the primary winding of the electromagnetic current transformer. DCi When the saturated primary AC current I ABHi The value can be obtained, and then the variation curve of the primary saturation current of the current transformer with the DC current component and the variation curve of the saturation current bias rate can be obtained, so as to realize the analysis function of the influence of the saturation characteristics of the electromagnetic current transformer under different DC components.

[0031] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific implementation manner. Any other implementation manners derived by those skilled in the art based on the technical solution of the present invention also fall within the scope of protection of the present invention.

Claims

1. A test method for a current transformer saturation characteristic test platform with a superimposed DC component, the current transformer saturation characteristic test platform with a superimposed DC component comprising a DC constant current source, an AC current source and an oscilloscope, the DC constant current source and the AC current source are connected to the primary side of the current transformer, the DC constant current source is used to apply DC current excitation to the current transformer, and the AC current source outputs AC current to the current transformer; the secondary side of the current transformer is connected to the oscilloscope, and the oscilloscope is used to record and output secondary information of the current transformer, characterized in that: The test method comprises the following steps: Step 1: When no DC current is applied to the primary side of the current transformer, an AC current is applied to the primary side to measure the primary AC current value I at which the current transformer is saturated. ABH0 ; Step 2, applying a given value of direct current to the primary side of the current transformer, and applying an alternating current to the primary side; Step 3: Control the AC current source to gradually increase the output AC current, observe the secondary current waveform through the oscilloscope on the secondary side, and record the primary AC current value when the current waveform is distorted to obtain the primary AC current value I when the current transformer is saturated when there is a DC component in the primary winding of the current transformer. ABHi ; Step 4, comparing the primary AC current value of the current transformer saturated obtained in step 1 with the primary AC current value of the current transformer saturated obtained in step 3, and calculating the saturation current bias rate f of the current transformer under the DC component; Step 5, repeating steps 2 to 4, measuring the saturated primary AC current value when different DC components exist in the primary winding of the current transformer, and then obtaining the variation curve of the primary saturation current of the current transformer with the DC current component, and the variation curve of the saturation current bias rate.

2. The testing method of the current transformer saturation characteristic testing platform with superimposed DC component according to claim 1 is characterized in that: The current transformer is an electromagnetic current transformer.

3. The testing method of the current transformer saturation characteristic testing platform with superimposed DC component according to claim 1 is characterized in that: The saturation current bias rate f of the current transformer under the DC component is obtained by the following calculation formula: f=(I ABH0 -I ABHi ) / I ABH0 *100%。

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