阅读说明：本技术 一种超导电缆各层电流分布的测试方法 (Method for testing current distribution of each layer of superconducting cable ) 是由 魏本刚 焦婷 张智勇 张喜泽 韩云武 李红雷 鲁燕青 王天龙 黄逸佳 陈志越 于 2021-06-21 设计创作，主要内容包括：一种超导电缆各层电流分布的测试方法,其特征在于,包括以下步骤：步骤1,选取具有两层导体层和至少一层屏蔽层的超导电缆作为测试电缆,将微分电流传感器的环形线圈设置于所述超导电缆的第一层导体和第二层导体之间；步骤2,向所述测试电缆的铜衬芯上施加输入电流,以获得所述微分电流传感器的电压电流转换特性；步骤3,分别将所述超导电缆的第一层导体和第二层导体连接至电流源,并分别向所述第一层导体和第二层导体施加输入电流,以测试所述微分电流传感器的输出电压；步骤4,基于所述微分电流传感器电压电流转换特性,以及步骤3中所述微分电流传感器的输出电压,计算出所述第一层导体的电流占比。本发明方法使用范围广,检测效果好。(A method for testing current distribution of each layer of a superconducting cable is characterized by comprising the following steps: step 1, selecting a superconducting cable with two conductor layers and at least one shielding layer as a test cable, and arranging a toroidal coil of a differential current sensor between a first layer conductor and a second layer conductor of the superconducting cable; step 2, applying input current to the copper lining core of the test cable to obtain the voltage-current conversion characteristic of the differential current sensor; step 3, respectively connecting the first layer conductor and the second layer conductor of the superconducting cable to a current source, and respectively applying input current to the first layer conductor and the second layer conductor to test the output voltage of the differential current sensor; and 4, calculating the current ratio of the first layer of conductor based on the voltage-current conversion characteristic of the differential current sensor and the output voltage of the differential current sensor in the step 3. The method has wide application range and good detection effect.)

1. A method for testing current distribution of each layer of a superconducting cable is characterized by comprising the following steps:

step 1, selecting a superconducting cable with two conductor layers and at least one shielding layer as a test cable, and arranging a toroidal coil of a differential current sensor between a first layer conductor and a second layer conductor of the superconducting cable;

step 2, applying input current to the copper lining core of the test cable to obtain the voltage-current conversion characteristic of the differential current sensor;

step 3, respectively connecting the first layer conductor and the second layer conductor of the superconducting cable to a current source, and respectively applying input current to the first layer conductor and the second layer conductor to test the output voltage of the differential current sensor;

and 4, calculating the current ratio of the first layer of conductor based on the voltage-current conversion characteristic of the differential current sensor and the output voltage of the differential current sensor in the step 3.

2. A method for testing current distribution of each layer of a superconducting cable according to claim 1, wherein the step 1 further comprises:

selecting two superconducting cables with the same type as a test cable; and the number of the first and second electrodes,

and connecting the tail ends of the shielding layers of the two cables through a forced backflow lead in a short circuit mode, and connecting the head ends of the shielding layers of the two cables to a current lead.

3. A method for testing current distribution of each layer of a superconducting cable according to claim 1, wherein the steps 2 and 3 further comprise:

connecting the differential current sensor with a multimeter; and the number of the first and second electrodes,

the multimeter records the output voltage generated by the differential current sensor when an input current is applied to the test cable.

4. A method for testing current distribution of each layer of a superconducting cable according to claim 1, wherein the step 2 further comprises:

applying an input current to the copper core of the shield layer through a current lead; and the number of the first and second electrodes,

in order to suppress power frequency interference, the frequency of the input current applied to the copper-clad core is different from the frequency of the input current applied to the first and second conductors.

5. The method for testing current distribution of each layer of a superconducting cable according to claim 4, wherein the step 2 further comprises:

applying a plurality of different input currents to the copper-lined core and obtaining a plurality of different output voltages of the differential current sensor; and the number of the first and second groups,

generating a voltage-to-current conversion characteristic of the differential current sensor based on the plurality of different input currents and the plurality of different output voltages.

6. The method for testing current distribution of each layer of a superconducting cable according to claim 5, wherein the step 2 further comprises:

keeping the main magnetic flux of the annular coil of the differential current sensor unchanged, and converting the plurality of different output voltages into voltage values under standard frequency;

wherein the standard frequency is a frequency of an input current applied to the first layer of conductors and the second layer of conductors.

7. A method for testing current distribution of each layer of a superconducting cable according to claim 1, wherein the step 3 further comprises:

the tail ends of the first conductor layer and the second conductor layer of the two cables are connected in a short circuit mode through a forced backflow lead, and the head ends of the first conductor layer and the second conductor layer are respectively connected with a current lead to form a first conductor layer and a second conductor layer of the superconducting cable;

connecting current leads at the head ends of the first and second layers of conductors to one end of a current source through a copper bar;

and connecting the current lead at the head end of the shielding layer to the other end of the current source through a copper bar.

8. The method for testing current distribution of each layer of a superconducting cable according to claim 7, wherein the step 3 further comprises:

applying a plurality of different input currents to the first layer of conductors and the second layer of conductors, the plurality of different input currents each being equal in magnitude to the plurality of different input currents applied to the copper-lined core.

9. A method for testing current distribution of each layer of a superconducting cable according to claim 1, wherein the step 4 further comprises:

when the input currents are equal, the ratio of the output voltage of the differential current sensor to the voltage value at the standard frequency in step 3 is calculated and recorded as the current ratio of the first layer conductor.

10. The method for testing current distribution of each layer of a superconducting cable according to claim 9, wherein the step 4 further comprises:

and if the current ratio of the first layer of conductor falls within a set threshold range, judging that the intercept design of the superconducting cable meets the current sharing requirement.

Technical Field

The invention relates to the field of superconducting power transmission, in particular to a method for testing current distribution of each layer of a superconducting cable.

Background

At present, in order to determine whether the design of the conductor and the shielding intercept of the superconducting cable meets the requirement of current sharing of the superconducting cable, the current distribution condition inside the superconducting cable needs to be tested. Generally, the current in the superconducting cable can be measured using a rogowski coil. Background art 1: current measurement of shielding layer of cold-insulated high-temperature superconducting cable, Zhaoweijie, etc., low-temperature engineering, 5 th year in 2013. As shown in background art 1, the conductor layer and the shielding layer of two superconducting cables are respectively communicated and form a current loop, and the rogowski coil is placed between the conductor layer loop and the shielding layer loop to detect the current condition of the conductor layer loop and the shielding layer loop. However, in the prior art, the method for testing the core current of the superconducting cable by using the rogowski coil is single, has limited data, and cannot test the superconducting cables with various structures.

Conventionally, with the technical development in the field of superconducting cables, various superconducting cables of new structures have been produced. Background art 2: CN101331560A discloses a superconducting cable core and a superconducting cable. Wherein each superconducting cable core further comprises a plurality of layers of superconducting conductors. However, a method for testing the current distribution characteristics between the multiple layers of superconducting conductors in the above-described novel superconducting cable has not appeared in the prior art.

Therefore, a method for testing current distribution of each layer of the superconducting cable is needed to test the design rationality of the conductor and shield intercept of the superconducting cable.

Disclosure of Invention

In order to solve the defects in the prior art, the invention aims to provide a method for testing current distribution of each layer of a superconducting cable, which can test the current distribution among a plurality of layers of superconducting conductors in the superconducting cable so as to test the design reasonableness of the conductors and shielding intercept of the superconducting cable. Therefore, the method has wider application range and better detection effect.

The invention adopts the following technical scheme. A method for testing current distribution of each layer of a superconducting cable comprises the following steps: step 1, selecting a superconducting cable with two conductor layers and at least one shielding layer as a test cable, and arranging a toroidal coil of a differential current sensor between a first conductor layer and a second conductor layer of the superconducting cable; step 2, applying input current to the copper lining core of the test cable to obtain the voltage-current conversion characteristic of the differential current sensor; step 3, respectively connecting the first layer conductor and the second layer conductor of the superconducting cable to a current source, and respectively applying input current to the first layer conductor and the second layer conductor so as to test the output voltage of the differential current sensor; and 4, calculating the current ratio of the first layer of conductor based on the voltage-current conversion characteristic of the differential current sensor and the output voltage of the differential current sensor in the step 3.

Preferably, step 1 further comprises: selecting two superconducting cables with the same type as a test cable; and the tail ends of the shielding layers of the two cables are connected in a short circuit mode through the forced backflow lead wire, and the head ends of the shielding layers of the two cables are connected to the current lead wire.

Preferably, step 2 and step 3 further comprise: connecting the differential current sensor with a multimeter; and, when an input current is applied to the test cable, the multimeter records the output voltage generated by the differential current sensor.

Preferably, step 2 further comprises: applying an input current to the copper core of the shield layer through the current lead; further, in order to suppress the power frequency interference, the frequency of the input current applied to the copper-clad core is different from the frequency of the input current applied to the first conductor layer and the second conductor layer.

Preferably, step 2 further comprises: applying a plurality of different input currents to the copper-lined core and obtaining a plurality of different output voltages of the differential current sensor; and generating a voltage-current conversion characteristic curve of the differential current sensor based on the plurality of different input currents and the plurality of different output voltages.

Preferably, step 2 further comprises: keeping the main magnetic flux of the annular coil of the differential current sensor unchanged, and converting a plurality of different output voltages into voltage values under standard frequency; wherein the standard frequency is a frequency of an input current applied to the first layer conductor and the second layer conductor.

Preferably, step 3 further comprises: the tail ends of a first conductor layer and a second conductor layer of two cables are connected in a short circuit mode through a forced backflow lead, and the head ends of the first conductor layer and the second conductor layer are respectively connected with a current lead to form a first conductor layer and a second conductor layer of the superconducting cable; connecting current leads at the head ends of the first and second layers of conductors to one end of a current source through a copper bar; and connecting a current lead at the head end of the shielding layer to the other end of the current source through a copper bar.

Preferably, step 3 further comprises: a plurality of different input currents are applied to the first layer of conductors and the second layer of conductors, each of the plurality of different input currents being equal in magnitude to the plurality of different input currents applied to the copper-lined core.

Preferably, step 4 further comprises: when the input currents are equal, the ratio of the output voltage of the differential current sensor to the voltage value at the standard frequency in step 3 is calculated and recorded as the current ratio of the first layer conductor.

Preferably, step 4 further comprises: and if the current ratio of the first layer of conductor falls within a set threshold range, judging that the intercept design of the superconducting cable meets the current sharing requirement.

Compared with the prior art, the method for testing the current distribution of each layer of the superconducting cable can test the current distribution condition of each layer in the special superconducting cable with a plurality of conductor layers and shielding layers, so that whether the intercept design of the conductor and the shielding can meet the requirement of current sharing or not is confirmed according to the test condition.

Drawings

Fig. 1 is a schematic view of a method for testing current distribution of each layer of a superconducting cable according to the present invention;

fig. 2 is a schematic diagram of a relationship curve between output voltage and current of the rogowski coil in the method for testing current distribution of each layer of the superconducting cable according to the present invention.

Reference numerals:

1-a shielding layer, wherein the shielding layer is formed by a plurality of layers,

2-a layer of a conductor, 2-a conductor layer,

3-a current lead-in wire for current,

4-forced reflux of the lead wire,

5-differential current sensor

Detailed Description

The present application is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present application is not limited thereby.

As shown in fig. 1, a method for testing current distribution of each layer of a superconducting cable includes steps 1 to 4.

Step 1, selecting a superconducting cable with two conductor layers and at least one shielding layer as a test cable, and arranging a toroidal coil of a differential current sensor between a first conductor layer and a second conductor layer of the superconducting cable.

The test method of the invention can test the distribution condition of the current of each layer in the superconducting cable with a plurality of conductor layers and shielding layers. In the present embodiment, a superconducting cable having two superconducting conductor layers and two superconducting shield layers may be used.

Preferably, two superconducting cables with the same model are selected as the test cable; and the tail ends of the shielding layers of the two cables are connected in a short circuit mode through the forced backflow lead wire, and the head ends of the shielding layers of the two cables are connected to the current lead wire.

Differential current sensors are also known as rogowski coils, or current measuring coils. The main body part is a ring coil uniformly wound on a non-ferromagnetic material. The signal it outputs is the differential with respect to time of the current flowing through its coil interior and is therefore referred to as a differential current sensor.

And 2, applying input current to the copper lining core of the test cable to obtain the voltage-current conversion characteristic of the differential current sensor.

It is understood that no current lead is temporarily connected between the first layer conductor and the second layer conductor while the process of step 2 is being performed.

Preferably, an input current is applied to the copper core of the shielding layer through a current lead; further, in order to suppress the power frequency interference, the frequency of the input current applied to the copper-clad core is different from the frequency of the input current applied to the first conductor layer and the second conductor layer. In one embodiment of the present invention, in order to suppress the power frequency interference, an ac current with a frequency of 57Hz may be applied to the copper lining core. At this point, the output voltage produced by the differential current sensor can be tested using a multimeter. The output voltage is also 57 Hz.

Preferably, a plurality of different input currents may be applied to the copper-lined core and a plurality of different output voltages of the differential current sensor obtained; and generating a voltage-current conversion characteristic curve of the differential current sensor based on the plurality of different input currents and the plurality of different output voltages.

Table 1 is a table of correlations between input current and output voltage generated according to step 2 of the method of the invention. As shown in table 1, the input currents may be set to 300A, 400A, 500A, 750A, and 1000A by the current sources, respectively, while the plurality of output voltages obtained based on the plurality of different input currents are 0.785V, 1.029V, 1.262V, 1.905V, and 2.483V, respectively.

A voltage-current conversion characteristic curve can be fitted according to the correlation between the input current and the output voltage in table 1. The curve is shown in figure 2.

TABLE 1 relationship table of copper lining core input current and output voltage

Input current/A	Output voltage/V	Standard frequency voltage/V
			300	0.785	0.689
400	1.029	0.903
			500	1.262	1.107
750	1.905	1.671
			1000	2.483	2.178

Preferably, the main magnetic flux of the annular coil of the differential current sensor can be kept unchanged, and a plurality of different output voltages can be converted into voltage values at standard frequency; wherein the standard frequency is a frequency of an input current applied to the first layer conductor and the second layer conductor. In an embodiment of the present invention, the frequency of the input current may be set to 50 Hz.

Therefore, the conversion ratio can be set to 57Hz/50Hz, i.e., 0.877. From this conversion ratio, the voltage value at the standard frequency shown in the third column in table 1 can be calculated.

And 3, respectively connecting the first layer conductor and the second layer conductor of the superconducting cable to a current source, and respectively applying input current to the first layer conductor and the second layer conductor so as to test the output voltage of the differential current sensor.

Preferably, the tail ends of the first conductor layer and the second conductor layer of the two cables are connected in a short circuit mode through a forced backflow lead, and the head ends of the first conductor layer and the second conductor layer of the two cables are respectively connected with a current lead so as to form a first conductor and a second conductor of the superconducting cable;

connecting current leads at the head ends of the first and second layers of conductors to one end of a current source through a copper bar;

and connecting the current lead at the head end of the shielding layer to the other end of the current source through a copper bar. Preferably, a plurality of different input currents are applied to the first layer of conductors and the second layer of conductors, each of the plurality of different input currents being equal in magnitude to the plurality of different input currents applied to the copper-lined core. By the setting method, calculation can be more convenient. Table 2 is a table of the relationship between the input current of the first layer conductor measured in step 3 of the present invention and the output voltage of the differential current sensor.

TABLE 2 relationship of input current to output voltage for conductors in the first layer

Total current/A	Rogowski coil voltage/V	Conversion to current/A
			300	0.33	1.107
400	0.44	0.903
			500	0.54	0.689
750	0.85	2.178
			1000	1.13	1.671

As shown in table 2, when the total input current of the first layer conductor and the second layer conductor is 300, 400, 500, 750, and 1000, respectively, the differential current sensor measures the output voltage of the first layer conductor to be 0.33, 0.44, 0.54, 0.85, and 1.33, respectively.

It is understood that step 2 and step 3 further include: connecting the differential current sensor with a multimeter; and, when an input current is applied to the test cable, the multimeter records the output voltage generated by the differential current sensor.

And 4, calculating the current ratio of the first layer of conductor based on the voltage-current conversion characteristic of the differential current sensor and the output voltage of the differential current sensor in the step 3.

Preferably, step 4 further comprises: when the input currents are equal, the ratio of the output voltage of the differential current sensor to the voltage value at the standard frequency in step 3 is calculated and recorded as the current ratio of the first layer conductor.

Table 3 shows a table synthesized from tables 1 and 2 in the present invention, and the current ratio of the first layer conductor can be obtained by comparing the output voltage in step 3 with the voltage value at the standard frequency converted in step 2.

TABLE 3 first layer conductor current ratio table

current/A	Conversion of measurement into 50hz voltage/V	Output voltage/V	Current ratio/%)
				300	0.689	0.33	47.9
400	0.903	0.44	48.7
				500	1.107	0.54	48.8
750	1.671	0.85	50.9
				1000	2.178	1.13	51.9

Preferably, if the current ratio of the first layer conductor falls within a set threshold range, the intercept design of the superconducting cable is judged to meet the current sharing requirement. In the present invention, the threshold range may be set in advance, for example, in the vicinity of 50%. In one embodiment of the present invention, the ratio may be (50% -a, 50% + a). Meanwhile, whether the current ratio is within the threshold range or not is judged, and if the current ratio is within the threshold range, the design of the superconducting cable meets the current sharing requirement.

Compared with the prior art, the method for testing the current distribution of each layer of the superconducting cable can test the current distribution condition of each layer in the special superconducting cable with a plurality of conductor layers and shielding layers, so that whether the intercept design of the conductor and the shielding can meet the requirement of current sharing or not is confirmed according to the test condition.

The present applicant has described and illustrated embodiments of the present invention in detail with reference to the accompanying drawings, but it should be understood by those skilled in the art that the above embodiments are merely preferred embodiments of the present invention, and the detailed description is only for the purpose of helping the reader to better understand the spirit of the present invention, and not for limiting the scope of the present invention, and on the contrary, any improvement or modification made based on the spirit of the present invention should fall within the scope of the present invention.