阅读说明：本技术 高压屏蔽电缆电磁屏蔽效能的测量方法和测量装置 (Method and device for measuring electromagnetic shielding effectiveness of high-voltage shielded cable ) 是由 李立嘉 沈涛 崔强 石磊 夏志立 于 2020-07-13 设计创作，主要内容包括：本发明公开了一种高压屏蔽电缆电磁屏蔽效能的测量方法,在30MHz-1GHz频段,按照如下步骤进行测量：S1：在电缆段连接一根已知插入损耗的同轴电缆以代替被测屏蔽电缆,在第一电流探头所在的被测频点测量功率值,在第二电流探头所在的被测频点测量功率值,消除系统测量误差；S2：在电缆段连接被测屏蔽电缆,测量第二电流探头所在的被测频点的功率值得到P<Sub>1</Sub>；S3：同时移动功率吸收钳和辅助吸收钳,找到被测频率点的最大值P<Sub>2</Sub>；S4：屏蔽电缆在该频点的屏效值为SE＝P<Sub>1</Sub>-P<Sub>2</Sub>。在9KHz-30MHz频段采用另一种测量步骤。该方法能够准确测量高压屏蔽电缆的电磁屏蔽效能。(The invention discloses a method for measuring electromagnetic shielding effectiveness of a high-voltage shielded cable, which comprises the following steps of: s1: connecting a coaxial cable with known insertion loss to the cable section to replace a tested shielded cable, measuring a power value at a tested frequency point where the first current probe is positioned, measuring a power value at a tested frequency point where the second current probe is positioned, and eliminating a system measurement error; s2: connecting the tested shielded cable to the cable section, and measuring the power value of the tested frequency point where the second current probe is located to obtain P 1 (ii) a S3: simultaneously moving the power absorption clamp and the auxiliary absorption clamp to find the maximum value P of the measured frequency point 2 (ii) a S4: the effective shielding value of the shielded cable at the frequency point is SE ═ P 1 ‑P 2 . Another measurement procedure is adopted in the frequency band of 9KHz-30 MHz. The method can accurately measure the electromagnetic shielding effectiveness of the high-voltage shielded cable.)

1. The method for measuring the electromagnetic shielding effectiveness of the high-voltage shielded cable is characterized in that a measuring device is established in a frequency band of 30MHz-1GHz as follows:

arranging a signal generator and a terminal load at two ends, sequentially connecting a first current probe, a wall-penetrating base, a cable section and a second current probe from the signal generator to the terminal load, connecting a movable auxiliary absorption clamp and a power absorption clamp on the cable section, and connecting the power absorption clamp with a receiver; arranging a reflection grounding plate at the through-wall base;

the measurement was carried out as follows:

s1: connecting a coaxial cable with known insertion loss to the cable section to replace a tested shielded cable, measuring a power value at a tested frequency point where the first current probe is positioned, measuring a power value at a tested frequency point where the second current probe is positioned, and eliminating a system measurement error;

s2: connecting the screen to be tested to the cable sectionThe shielded cable measures the power value of the measured frequency point where the second current probe is positioned to obtain P₁；

S3: simultaneously moving the power absorption clamp and the auxiliary absorption clamp to find the maximum value P of the measured frequency point₂；

S4: the effective shielding value of the shielded cable at the frequency point is SE ═ P₁-P₂。

2. The method for measuring the electromagnetic shielding effectiveness of the high-voltage shielded cable according to claim 1, wherein a current probe calibration device is further disposed at the first current probe and the second current probe.

3. The method for measuring the electromagnetic shielding effectiveness of the high-voltage shielded cable according to claim 1, wherein an electric measuring guide rail is further arranged beside the cable section.

4. The method for measuring the electromagnetic shielding effectiveness of the high-voltage shielded cable according to claim 1, wherein the measuring device is established in the frequency band of 9KHz to 30MHz as follows:

arranging a signal generator and a terminal load at two ends, and sequentially connecting a wall penetrating base, a third current probe, a cable section and a fourth current probe from the signal generator to the terminal load; arranging a reflection grounding plate at the through-wall base;

the measurement was carried out as follows:

s1: connecting a coaxial cable with known insertion loss to the cable section to replace a tested shielded cable, measuring a power value at a tested frequency point where the third current probe is positioned, measuring a power value at a tested frequency point where the fourth current probe is positioned, and eliminating a system measurement error;

s2: the cable section is connected with the tested shielded cable, the power value is measured at the tested frequency point where the third current probe is positioned, the power value is measured at the tested frequency point where the fourth current probe is positioned, and P is obtained₁；

S3: moving the position of the third current probe or the fourth current probe, measuring at three positions of the measured shielded cable, and averaging to obtain the average valueTo P₂Or finding the maximum leak value as P₂；

S4: the effective shielding value of the shielded cable at the frequency point is SE ═ P₁-P₂。

5. The method for measuring the electromagnetic shielding effectiveness of the high-voltage shielded cable according to claim 4, wherein a current probe calibration device is further disposed at the third current probe and the fourth current probe.

6. A device for measuring electromagnetic shielding effectiveness of a high-voltage shielded cable, which is suitable for the measuring method according to claim 1, and is characterized by comprising, in a frequency band of 30MHz-1 GHz: the device comprises a signal generator and a terminal load which are positioned at two ends, wherein a first current probe, a wall penetrating base, a cable section and a second current probe are sequentially connected from the signal generator to the terminal load; and a reflection grounding plate is arranged at the through-wall base.

7. The apparatus for measuring the electromagnetic shielding effectiveness of a high-voltage shielded cable according to claim 6, wherein the apparatus further comprises a signal generator and a terminal load disposed at two ends of the apparatus, wherein the signal generator and the terminal load are sequentially connected to the wall base, the third current probe, the cable segment and the fourth current probe from the signal generator to the terminal load; and a reflection grounding plate is arranged at the through-wall base.

Technical Field

The invention relates to a technology for testing electromagnetic shielding effectiveness of a high-voltage shielded cable, in particular to a method and a device for measuring the electromagnetic shielding effectiveness of the high-voltage shielded cable.

Background

The high-voltage cable is used for transmitting large currents such as direct-current voltage, power frequency voltage and the like. In the transmission switching process, a large number of radio frequency interference signals can be generated, severe electromagnetic pollution is caused to the use environment, in order to inhibit electromagnetic interference, a shielding layer is added outside a high-voltage cable, and the high-voltage shielding cable is formed and is widely applied to the fields of electric automobiles, power communication, aerospace, naval vessel military industry and the like. How to evaluate the shielding effectiveness of a high-voltage shielded cable is a problem of intense research, and the surface transfer impedance of the high-voltage shielded cable is measured by a line injection method or a triple-axis method to represent the shielding effectiveness of the cable. But encounter many problems and difficulties in implementation.

From the measurement port impedance classification, shielded cables can be classified into two types, fixed impedance shielded cables (e.g., 50 Ω coaxial cables, with impedance maintained at 50 Ω over a frequency range) and non-fixed impedance shielded cables (e.g., various shielded wires). Fixed impedance shielded cables are typically used for radio frequency signal transmission, while non-fixed impedance shielded cables are typically used for high voltage power transmission.

A method for measuring the electromagnetic shielding effectiveness of a fixed-impedance shielded cable, such as the power absorption clamp method, is to obtain a reference measured value P by using the characteristic that the impedance of the measured shielded cable is not changed (the whole measuring system is a 50 omega system)₁. The maximum value P of the leakage radio frequency signal of the tested shielded cable is searched on a 6000mm test guide rail by using power absorption pliers₂. Effective shielding value SE (equal to P) of shielded cable at measuring frequency point₁-P₂. The measurable frequency range is 30MHz-1 GHz.

The electromagnetic shielding effectiveness of an unfixed impedance shielded cable cannot be measured by using a method for measuring the electromagnetic shielding effectiveness of a fixed impedance shielded cable. The port impedance of the non-fixed impedance shielded cable can change along with frequency, length, thickness, manufacturing process and the like. Radio frequency signals are reflected at junctions where impedance discontinuities occur. How much the RF signal is reflected is not clear enough to obtain an accurate reference measurement P₁Obtaining no P₁A measurement of the electromagnetic shielding effectiveness cannot be achieved. This is why up to now there is no international oneA uniformly accepted measurement method is used to measure the cause of electromagnetic shielding effectiveness of non-fixed impedance shielded cables.

Disclosure of Invention

The invention aims to provide a method and a device for measuring the electromagnetic shielding effectiveness of a high-voltage shielded cable, which are used for accurately measuring the electromagnetic shielding effectiveness of a non-fixed impedance shielded cable.

In order to achieve the above object, in a first aspect, the present invention provides a method for measuring electromagnetic shielding effectiveness of a high-voltage shielded cable, wherein a measuring device is established in a frequency range of 30MHz to 1GHz as follows:

arranging a signal generator and a terminal load at two ends, sequentially connecting a first current probe, a wall-penetrating base, a cable section and a second current probe from the signal generator to the terminal load, connecting a movable auxiliary absorption clamp and a power absorption clamp on the cable section, and connecting the power absorption clamp with a receiver; arranging a reflection grounding plate at the through-wall base;

the measurement was carried out as follows:

s1: connecting a coaxial cable with known insertion loss to the cable section to replace a tested shielded cable, measuring a power value at a tested frequency point where the first current probe is positioned, measuring a power value at a tested frequency point where the second current probe is positioned, and eliminating a system measurement error;

s2: connecting the tested shielded cable to the cable section, and measuring the power value of the tested frequency point where the second current probe is located to obtain P₁；

S3: simultaneously moving the power absorption clamp and the auxiliary absorption clamp to find the maximum value P of the measured frequency point₂；

S4: the effective shielding value of the shielded cable at the frequency point is SE ═ P₁-P₂。

Further, a current probe calibration device is arranged at the first current probe and the second current probe.

Furthermore, an electric measuring guide rail is arranged beside the cable section.

Further, in the frequency band of 9KHz-30MHz, a measuring device is established according to the following modes:

arranging a signal generator and a terminal load at two ends, and sequentially connecting a wall penetrating base, a third current probe, a cable section and a fourth current probe from the signal generator to the terminal load; arranging a reflection grounding plate at the through-wall base;

the measurement was carried out as follows:

s1: connecting a coaxial cable with known insertion loss to the cable section to replace a tested shielded cable, measuring a power value at a tested frequency point where the third current probe is positioned, measuring a power value at a tested frequency point where the fourth current probe is positioned, and eliminating a system measurement error;

s2: the cable section is connected with the tested shielded cable, the power value is measured at the tested frequency point where the third current probe is positioned, the power value is measured at the tested frequency point where the fourth current probe is positioned, and P is obtained₁；

S3: moving the position of the third current probe or the fourth current probe, measuring at three positions of the measured shielded cable, and averaging to obtain P₂Or finding the maximum leak value as P₂；

S4: the effective shielding value of the shielded cable at the frequency point is SE ═ P₁-P₂。

Further, a current probe calibration device is arranged at the third current probe and the fourth current probe.

In a second aspect, the present invention further provides a device for measuring electromagnetic shielding effectiveness of a high-voltage shielded cable, which is suitable for the above measuring method, and includes: the device comprises a signal generator and a terminal load which are positioned at two ends, wherein a first current probe, a wall penetrating base, a cable section and a second current probe are sequentially connected from the signal generator to the terminal load; and a reflection grounding plate is arranged at the through-wall base.

Furthermore, the frequency range of 9KHz-30MHz, the measuring device also comprises a signal generator and a terminal load which are arranged at two ends, and the signal generator and the terminal load are sequentially connected with the wall-through base, the third current probe, the cable section and the fourth current probe; and a reflection grounding plate is arranged at the through-wall base.

Compared with the prior art, the method can accurately measure the reference value P of the non-fixed impedance shielded cable by a reasonably-built measuring system and applying an innovative measuring method₁And finally obtaining the electromagnetic shielding effectiveness of the non-fixed impedance shielded cable on the basis.

Drawings

FIG. 1 is a diagram of a vector network analyzer test connection;

FIG. 2 is a diagram showing the test results of the impedance value of a 0.6m thin wire cable;

FIG. 3 is a diagram showing the test results of attenuation values of 0.6m thin wire cables;

FIG. 4 is a diagram showing the results of the test of the impedance value of a 1.2m thin wire cable;

FIG. 5 is a graph showing the test results of attenuation values of 1.2m thin wire cables;

FIG. 6 is a diagram showing the results of the test of the impedance value of a thin wire cable of 6 m;

FIG. 7 is a graph showing the test results of attenuation values of a 6m thin wire cable;

FIG. 8 is a diagram of the results of testing the impedance of a 0.6m thick wire cable;

FIG. 9 is a graph showing the test results of attenuation values of 0.6m thick cable;

FIG. 10 is a graph showing the results of testing the impedance of a 1.2m thick wire cable;

FIG. 11 is a graph showing the test results of attenuation values of 1.2m thick-line cables;

FIG. 12 is a diagram showing the results of testing the impedance of a 6m thick-wire cable;

FIG. 13 is a graph showing the test results of attenuation values of cables with 6m thick wires;

fig. 14 is a device (30MHz-1GHz band) for measuring electromagnetic shielding effectiveness of a high-voltage shielded cable according to an embodiment of the present invention;

FIG. 15 is a schematic diagram of an apparatus for measuring electromagnetic shielding effectiveness of a high-voltage shielded cable (frequency band of 9kHz-30MHz) according to an embodiment of the present invention;

FIG. 16 is a graph of effective value test curve (9kHz-30MHz) for a 6m thin wire cable screen;

FIG. 17 is a graph showing the screen effective value test curve (30MHz-300MHz) of a 6m thin wire cable.

Detailed Description

The principles and spirit of the present invention will be described with reference to a number of exemplary embodiments shown in the drawings. It should be understood that these embodiments are described only to enable those skilled in the art to better understand and to implement the present invention, and are not intended to limit the scope of the present invention in any way.

Before describing the technical solutions of the embodiments of the present invention, the present invention is first described in the research and analysis, which are important for the present invention, and the inventors have made creative efforts for this purpose.

Reference measurement P needed by considering how to obtain non-fixed impedance shielded cable screen effect measurement₁In the invention, the characteristics and the change rule of the vector network analyzer are firstly researched by the vector network analyzer. Fig. 1 is a test connection diagram. Fig. 2 to 7 show the results of impedance and attenuation tests for different lengths of the same shielded cable. Fig. 8 to 13 show the results of impedance and attenuation tests for different lengths of another shielded cable. The relevant test data are shown in tables 1-6.

TABLE 10.6 m Fine line impedance and attenuation values

Frequency of	Impedance (L)	Attenuation value
			30kHz	49Ω	0dB
50kHz	49Ω	0dB
			494kHz	50Ω	0dB
1MHz	50Ω	-1dB
			10MHz	44Ω	0dB
57MHz	14Ω	-2dB
			140MHz	49Ω	0dB
226MHz	23Ω	-3dB
			286MHz	49Ω	-2dB
363MHz	30Ω	-3dB
			400MHz	49Ω	-2dB

TABLE 21.2 m Fine line impedance and attenuation values

Frequency of	Impedance (L)	Attenuation value
			30kHz	49Ω	0dB
1MHz	49Ω	0dB
			10MHz	33Ω	0dB
37MHz	13Ω	-3dB
			69MHz	44Ω	-1dB
110MHz	17Ω	-3dB
			147MHz	37Ω	-1dB
187MHz	24Ω	-3dB
			215MHz	44Ω	-2dB
248MHz	21Ω	-4dB
			286MHz	46Ω	-2dB
330MHz	30Ω	-4dB
			363MHz	44Ω	-3dB
400MHz	31Ω	-4dB

TABLE 36 m Fine line impedance and attenuation values

TABLE 40.6 m bold line impedance and attenuation values

Frequency of	Impedance (L)	Attenuation value
			30kHz	50Ω	0dB
1Mhz	50Ω	0dB
			9Mhz	24Ω	-2dB
39Mhz	4Ω	-7dB
			75Mhz	44Ω	-1dB
116Mhz	6Ω	-7dB
			154Mhz	36Ω	-1dB
196Mhz	11Ω	-6dB
			226Mhz	42Ω	-2dB
273Mhz	13Ω	-7dB
			300Mhz	42Ω	-2dB
346Mhz	14Ω	-7dB
			381Mhz	37Ω	-2dB
400Mhz	8Ω	-5dB

TABLE 66 m Thick line impedance and attenuation values

Frequency of	Impedance (L)	Attenuation value
			30kHz	49Ω	0dB
518kHz	45Ω	0dB
			1MHz	35Ω	-1dB
7MHz	4Ω	-6dB
			14MHz	38Ω	-1dB
22MHz	5Ω	-7dB
			27MHz	36Ω	-2dB
35MHz	4Ω	-7dB
			42MHz	32Ω	-2dB
49MHz	5Ω	-7dB
			57MHz	30Ω	-2dB
62MHz	5Ω	-7dB
			72MHz	26Ω	-3dB
49MHz	7Ω	-7dB
			87MHz	21Ω	-4dB
237MHz	10Ω	-9dB
			273MHz	21Ω	-7dB
381MHz	14Ω	-10dB

As can be seen from fig. 2-13: different cables or the same cable length will have the following characteristics:

the impedance of the shielded cable varies and is large with the change of frequency.

② the same shielded cable length is different and the impedance is also different and the variation is large.

And thirdly, when the geometric dimension of the same shielded cable is fixed, the impedance changes only as a function of frequency (single variable).

Fourthly, when the geometric dimension, the structural form, the measuring frequency and other factors of the cable are determined, the impedance is a fixed value, and the attenuation is a fixed value.

The same shielded cable has no linear relation between length and attenuation (at some frequency points, the insertion loss is not always large when the long line is long)

Sixthly, the impedance varies greatly with the frequency, but is less than 50 omega.

The impedance of the cable below 1MHz is basically unchanged.

That is, when a shielded cable of a certain length and a non-fixed impedance is placed in a 50 Ω measuring system, the desired reference measured value P can be obtained accurately by measuring the attenuation₁The measured shielded cable can be regarded as a radio frequency attenuator changing along with the change of frequency in a 50 omega measuring system, and the change of the S21 value really reflects a measurement reference value P caused by the change of frequency, impedance and reflection of a radio frequency signal in the measured shielded cable₁The difference between the change of the reference value P and the maximum screen effect measurement method of the fixed impedance shielded cable is that the reference value P is the reference value P in the screen effect measurement of the non-fixed impedance shielded cable₁The measurement is changed according to the type, length, frequency and the like of the cable, and the measurement is needed from time to time (the reference value is greatly changed, and double measurement errors are brought).

Accordingly, the embodiment of the invention puts the shielded cable into a 50 omega measuring system, and the reference value P of the screen effect measurement can be obtained by measuring the attenuation₁Two sets of devices are designed for dividing the measuring frequency of 9kHz-1GHz into two parts of 30MHz-1GHz and 9kHz-30MHz respectively to measure the screen effect, so that the attenuation value P can be obtained₂。

The 30MHz-1GHz cable screen effect measuring device and method:

the frequency band of 30MHz-1GHz is measured by the measuring device of FIG. 14. Two current probe calibration devices are connected in series on the basis of the original device for measuring the screen effect of the 50 omega coaxial cable, and on the basis of ensuring that the whole measuring system (except the measured shielded cable) is a 50 omega system in the measuring frequency band, the current probe is utilized to obtain the reference value P of the measuring signal₁The attenuation measurement P is obtained by finding the maximum value of the leakage signal on a 600mm measuring rail by means of power absorption clamps and coupling clamps₂So as to obtain the screen effect measured value SE-P of the shielded cable₁-P₂。

Specifically, a signal generator 11 and a terminal load 17 are arranged at two ends, a first current probe 13a, an N-N wall socket 18, a cable section and a second current probe 13b are sequentially connected from the signal generator 11 to the terminal load 17, a movable auxiliary absorption clamp 14 and a power absorption clamp 15 are connected to the cable section, and the power absorption clamp 15 is connected to a receiver 110. A 2m multiplied by 2mm grounded reflection copper plate 19 is arranged at the through-wall base 18, an electric measuring guide rail 16 with the length of 6m is arranged beside the cable section, and a current probe calibration device 12 is arranged at the first current probe 13a and the second current probe 13 b. Wherein, the cable section is used for arranging the tested shielded cable 111 or a cable for eliminating system measurement errors.

The measurement method is carried out as follows:

s1: a50 omega coaxial cable with known insertion loss is used for replacing the tested shielded cable 111, and power values of two points are measured A, D at the tested frequency point, so that system measurement errors are eliminated.

S2: connecting the tested shielded cable 111, and measuring the power value of the D point on the tested frequency point to obtain P₁

S3: simultaneously moving the power absorption clamp and the auxiliary absorption clamp to find the maximum value P of the measured frequency point₂

S4: the effective shielding value of the shielded cable at the frequency point is SE ═ P₁-P₂；

The shielding value of the shielded cable obtained by the method is independent of the length of the shielded cable in the frequency band of 30MHz-1GHz, and the method is recommended to be carried out in a shielded room.

The 9kHz-30MHz cable screen effect testing device and method comprises the following steps:

and measuring the shielding effectiveness of the 9KHz-30MHz frequency band shielding cable. In principle, similar methods can be applied, but the practical implementation is difficult. The wavelength of 30MHz is 10 meters, the reference value and the maximum leakage value of the measuring frequency of the shielded cable above 30MHz are found in the half wavelength, but the wavelength of 10MHz is 30 meters, the wavelength of 3MHz is 100 meters, the wavelength of 1MHz is 300 meters … …, the wavelength of 10KHz is 30000 meters, and then P is found in the half wavelength₁And P₂It is difficult.

As discussed above, the characteristic impedance of the shielded cable in the frequency band below 1MHz has a small change, substantially 50 Ω (in the case of a termination load of 50 Ω), that is, the measurement uncertainty of the shielded cable below 1MHz caused by reflection is small and can be ignored, if the maximum leakage of the shielded cable with half wavelength is not to be found, half of the wavelength of 1MHz is taken, and the maximum leakage is not to be found in the frequency band below 1 MHz.

Because the length of the same type of shielded cable is different, the impedance is different, and the reflection is different. The effective value of the measurement screen will also be different. Therefore, the screen effective value of the shielded cable is measured in the frequency range of 9KHz-30MHz, and the measurement is carried out based on the length of the shielded cable actually used. If the manufacturer of the shielded cable has conditions (can build a measuring environment with half wavelength), the screen effective value of the shielded cable can be measured by the same measuring method.

It should be noted that, it is most accurate to measure the screen effective value of the half-wavelength shielded cable by using this measurement method, (for this shielded cable line as a whole), and it is most suitable for the actual use (for the user of the shielded cable) to measure the screen effective value of the shielded cable with the actual used length.

The screen effect measuring connection of the 9KHz-30MHz frequency range shielded cable is as shown in FIG. 15, a signal generator 21 and a terminal load 26 are arranged at two ends, and an N-N wall penetrating base 22, a third current probe 25a, a cable section and a second current probe 25b are sequentially connected from the signal generator 21 to the terminal load 26; a 2m multiplied by 2m grounding reflection copper plate 23 is arranged at the through-wall base; the third current probe 25a and the fourth current probe 25b are also provided with a current probe calibration device 24, and are also connected with a grounding copper plate 28. The device is also equipped with a 0.8m high non-metallic test stand 27.

The measurement was carried out as follows:

s1: a50 omega coaxial cable with known insertion loss is used for replacing a tested shielded cable, and power values of two points are measured A, E at a tested frequency point, so that system measurement errors are eliminated.

S2: connecting the tested shielded cable, and measuring the power values of the two points E on the tested frequency point to obtain P₁

S3: the position of the current probe 25 (the current probe 25 may be the third current probe 25a or the fourth current probe 25b) is moved, the three positions are B, C, D measured, and P is obtained by averaging₂(or finding the maximum leakage value P₂)

S4: the effective shielding value SE of the shielded cable at the frequency point is equal to P₁-P₂

Test results

Tables 7 and 8 are screen effective values measured when the same shielded cable is different in length;

the table 9 and the table 10 are screen effective values measured when the other shielding cables of the same type have different lengths;

table 11 shows the screen effective values measured for another shielded cable.

And (4) setting the screen effective value SE as the E point value- (the maximum value of the B point value, the C point value and the D point value).

TABLE 70.6 thick line test results

Date: wire length: 0.6m type: output amplitude of thick line source of 110dBuV

Frequency of	A point value	E point value	B point value	C point value	D point value	Screen effective value
							10kHz
	110	108	81	81	82	26
							50kHz	112	104	71	71	71	33
100kHz	110	106	67	67	67	39
							500kHz	107	105	55	55	55	50
1MHz	105.7	103.6	50.6	50.6	50.6	53
							5MHz	106.4	104.2	57.4	56.4	56.4	46.8
10MHz	109	103.2	52.3	52.3	52.3	50.9
							20MHz	111	100.7	52.8	52.8	52.8	47.9
30MHz	111.4	99	51.3	50.3	51.3	47.7

TABLE 81.2 m thick line test results

Date: wire length: 1.2m type: output amplitude of thick line source of 110dBuV

Frequency of	A point value	E point value	B point value	C point value	D point value	Screen effective value
							10kHz	107	107	79	79	79	28
50kHz	109	106	65	66	66	40
							100kHz	108	102	62	62	62	40
500kHz	104	100	51	51	51	49
							1MHz	100.7	97.6	45.6	40.6	46.6	51
5MHz	95.2	90.4	54.4	51.4	54.4	40.8
							10MHz	106.2	91	46.3	46.3	46.3	59.9
20MHz	95.7	92	48.8	53.8	47.8	41.9
							30MHz	107.2	96.7	54.3	54.3	54.3	42.4

TABLE 90.6 m Fine line test results

Date: wire length: 0.6m type: output amplitude of thin line source of 110dBuV

Frequency of	A point value	E point value	B point value	C point value	D point value	Screen effective value
							10kHz	108	108	86	86	86	22
50kHz	110	106	75	75	75	31
							100kHz	110	106	72	72	72	34
500kHz	107	105	61	61	61	44
							1MHz	105.7	103.6	56.6	56.6	56.6	47
5MHz	106.4	104.2	60.4	60.4	60.4	43.8
							10MHz	108	104.2	57.3	58.3	58.3	45.9
20MHz	110	102.7	55.8	57.8	56.8	44.9
							30MHz	110.4	101	54.3	53.3	54.3	46.7

TABLE 101.2 m Fine line test results

Date: wire length: 1.2m type: output amplitude of thin line source of 110dBuV

Frequency of	A point value	E point value	B point value	C point value	D point value	Screen effective value
							10kHz	109	107	90	90	90	19
50kHz	110	106	78	78	78	28
							100kHz	110	106	74	74	74	32
500kHz	107	104	61	61	61	43
							1MHz	105.7	103.6	55.6	55.6	55.6	48
5MHz	107.4	104.2	57.4	57.4	57.4	46.8
							10MHz	109	103.2	55.3	55.3	55.3	47.9
20MHz	111	100.7	55.8	54.8	55.8	44.9
							30MHz	110.4	100	53.3	51.3	54.3	45.7

TABLE 116 m Fine line test results

Date: 12/2 line length: the model of 6m is: output amplitude of thin line source of 110dBuV

Frequency of	A point value	E point value	C point value	Screen effective value
					30MHz	109.3	101	61	40
50MHz	101.7	100.6	68.1	32.5
					100MHz	107.1	98.3	66.4	31.9
120MHz	108.2	97.5	65.1	32.4
					150MHz	106	98.2	77.8	20.4
200MHz	105.3	90.3	71.1	19.2
					250MHz	105	90	71.5	18.5
300MHz	100	87	64.5	22.5
					400MHz	99	86	75.9	10.1

FIG. 16 is a screen virtual value test curve (9kHz-30MHz) of a 6m fine line cable, and FIG. 17 is a screen virtual value test curve (30MHz-300MHz) of the 6m fine line cable.

It must be noted that: the joint part of the tested shielded cable must adopt strict shielding measures. And ensuring that the screen effective value of the part is higher than that of the tested shielded cable.

The method for measuring the electromagnetic shielding effectiveness of the high-voltage shielded cable, namely the current probe method, provided by the embodiment of the invention is proved to be accurate in test data and good in repeatability through tests and verifications for several months. The problem of measuring the electromagnetic shielding effectiveness of the high-voltage shielding cable in the frequency range of 9kHz-400MHz is basically solved, and the measuring frequency range can be expanded to 9kHz-1 GHz. The method is also suitable for testing the shielding effectiveness of the coaxial cable.

The embodiment provides a novel method for measuring the electromagnetic shielding effectiveness of a high-voltage shielded cable, namely a current probe method. The method is based on the basic principle of electromagnetic shielding effectiveness measurement. The high-voltage shielded cable to be measured is put into a specially-arranged 50 omega measuring system. Through the current probe and the calibration device thereof, a reference measurement value P required by the measurement of the electromagnetic shielding effectiveness of the high-voltage shielded cable is accurately obtained in the frequency range of 9kHz-1GHz₁. Obtaining a shielded attenuation measured value P by using a current probe at a frequency range of 9kHz-30MHz₂Obtaining the shielded attenuation measured value P by using a power absorption clamp in the frequency range of 30MHz-1GHz₂So as to measure the effective shielding value SE (SE is P) of the high-voltage shielded cable₁-P₂)

The method provides effective shielding indexes of the high-voltage shielding cable for further application of the high-voltage shielding cable in the fields of power communication, electric automobiles, aerospace, ship manufacturing and the like, and provides beneficial help for solving the problem of system-level electromagnetic compatibility.

The inventive concept is explained in detail herein using specific examples, which are given only to aid in understanding the core concepts of the invention. It should be understood that any obvious modifications, equivalents and other improvements made by those skilled in the art without departing from the spirit of the present invention are included in the scope of the present invention.