CN111220855B - Method for measuring conducted interference signal in strong electromagnetic environment - Google Patents
Method for measuring conducted interference signal in strong electromagnetic environment Download PDFInfo
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- CN111220855B CN111220855B CN202010074060.3A CN202010074060A CN111220855B CN 111220855 B CN111220855 B CN 111220855B CN 202010074060 A CN202010074060 A CN 202010074060A CN 111220855 B CN111220855 B CN 111220855B
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- G01R29/0814—Field measurements related to measuring influence on or from apparatus, components or humans, e.g. in ESD, EMI, EMC, EMP testing, measuring radiation leakage; detecting presence of micro- or radiowave emitters; dosimetry; testing shielding; measurements related to lightning
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Abstract
The invention belongs to a method for testing conducted interference signals, which solves the technical problems that in the existing method for testing the circuit conducted interference signals of a complex circuit system under the strong electromagnetic environment, the accurate measurement is difficult to be carried out by a testing method specified by an electromagnetic compatibility standard, and when a conventional testing probe used for testing signals such as voltage, current and the like is used for testing, a background interference signal and a useful signal which are induced by the conventional testing probe are easy to mix, so that the real conducted interference signals cannot be accurately distinguished, and provides a method for measuring the conducted interference signals under the strong electromagnetic environment. And accurate measurement of the ground line conduction current interference signal.
Description
Technical Field
The invention belongs to a method for testing conducted interference signals, and particularly relates to a method for measuring conducted interference signals in a strong electromagnetic environment.
Background
Under strong electromagnetic environment, electromagnetic radiation outside the circuit system can be inductively coupled into the circuit system through structures such as an antenna, a cable and a closed loop, and strong unnecessary conduction interference is formed inside the circuit system; in the operation process of the complex circuit system, external electromagnetic radiation and conducted interference can be generated, so that the severity of the external electromagnetic environment and the internal conducted interference is increased. Under the action of strong electromagnetic environment and conducted interference, once the electromagnetism is incompatible, sensitive terminals in the circuit system, including a chip, a processor, a comparator, a circuit board and the like, have the problems of disturbance, function loss, device damage, circuit burning and the like, and the stability and reliability of the circuit system are seriously reduced. The electromagnetic incompatibility and interference problems of complex circuit systems in strong electromagnetic environments are researched and solved, and the premise and the foundation are that accurate measurement and evaluation must be carried out on circuit conducted interference of a problem line.
Under the external strong electromagnetic environment stronger than kV/m level, the conductive interference signals in the complex circuit are difficult to be accurately measured by the existing testing method specified by the electromagnetic compatibility standard; even if the conventional test probe for testing signals such as voltage, current and the like is not connected with a circuit, the conventional test probe is only short-circuited in a strong electromagnetic environment, namely, a strong background interference signal is induced on the output side of the probe, and when the background interference signal of the probe and a useful signal are mixed together, the original real conduction interference signal in a line cannot be accurately distinguished at all.
Disclosure of Invention
The invention mainly aims to solve the technical problems that in the existing method for testing the circuit conducted interference signals of a complex circuit system in a strong electromagnetic environment, the testing method specified by an electromagnetic compatibility standard is difficult to accurately measure, and when a conventional test probe used for testing signals such as voltage, current and the like is used for testing, a background interference signal and a useful signal induced by the conventional test probe are easy to mix, so that real conducted interference signals cannot be accurately distinguished, and provides the method for measuring the conducted interference signals in the strong electromagnetic environment.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for measuring conducted interference signals in a strong electromagnetic environment is characterized by comprising the following steps:
s1, throwing wire leading-out and connection of shielded three-way test cable
S1.1, taking a section of shielded three-way test cable wrapped with a shielding layer outside, and dividing all signal wires to be tested in the shielded three-way test cable into two parts to form corresponding swing wires to be tested;
s1.2, wrapping a conductive shielding layer on the outer side of the to-be-measured swing line, reserving wiring terminals at the end parts, and marking at each wiring terminal;
s1.3, forming a small hole in the middle of the shielding three-way test cable, and enabling the wiring terminals of each throwing line to be tested to penetrate out of the small hole to form a throwing line bundle to be tested; wrapping a conductive shielding layer outside the to-be-detected swing wire bundle and at a gap between the to-be-detected swing wire bundle and the small hole, and reserving a wiring terminal of each to-be-detected swing wire in the to-be-detected swing wire bundle;
s1.4, connecting the shielded three-way test cable processed in the step S1.3 between a signal transmission cable outside the case and a cable socket matched with the case for switching;
s2, differential Voltage Probe Shielding
S2.1, connecting a differential voltage probe with the bandwidth of more than or equal to 1GHz with an oscilloscope;
s2.2, connecting the test end of the differential voltage probe with the lead terminal corresponding to the wiring terminal of each wire to be tested in the wire bundle to be tested;
s2.3, sequentially wrapping a purple copper net and a purple copper foil at the joint of the differential voltage probe and the swing wire harness to be tested from inside to outside, so that the shielded three-way test cable is shielded from the differential voltage probe;
s3, connecting the grounding wire in series with a shielding current indicating resistor
S3.1, placing two red copper plates in parallel on the same plane, and reserving a gap which is less than or equal to 30mm between the two red copper plates;
s3.2, uniformly arranging n resistance values along the gap and marking as R0The two pins of each non-inductive metal film resistor are respectively welded on the two copper plates, and the n non-inductive metal film resistors are connected in parallel to form a current indicating resistor R, wherein R is R0/n，R≤0.1Ω；
S3.3, connecting the whole body formed by the two red copper plates and the current indicating resistor in series to a grounding wire to be tested;
s4, coaxial shielding test cable sampling leading-out
S4.1, taking the coaxial double-layer shielding test cable, enabling the core wire, the inner shielding layer and the outer shielding layer at one end of the coaxial double-layer shielding test cable to be mutually insulated, and respectively welding the core wire and the inner shielding layer lead of the coaxial double-layer shielding test cable to the two red copper plates in the step S3;
s4.2, sequentially wrapping an insulating layer and a red copper foil outside the current indicating resistor, the core wire at one end of the coaxial double-layer shielding test cable, the lead wire of the inner shielding layer and the two red copper plates from inside to outside;
s4.3, connecting the other end of the coaxial double-layer shielding test cable with the oscilloscope;
s5, isolation power supply oscilloscope test
Connecting the oscilloscope with commercial power through a second isolation transformer;
s6, testing the conductive interference signal
And measuring a conducted voltage interference signal between a signal wire and a grounding shell in the shielded three-way test cable through the differential voltage probe, or measuring a transient conducted voltage interference signal between any two points on the surface of the grounding shell through the differential voltage probe, or measuring a conducted current interference signal of the grounding wire to be tested through an oscilloscope.
Further, in step S1.1, the length of the shielded three-way test cable is less than or equal to 100mm, the exterior of the shielded three-way test cable is wrapped by a double-layer wire mesh shielding sleeve, and the mesh diameter of the wire mesh is less than or equal to 200 meshes; and every two of the signal wires in the shielded three-way test cable are twisted in pairs.
Further, in the step S1.1, the length of the to-be-measured swing line is less than or equal to 30 mm; in the step S1.2, at least three layers of purple copper foils are adopted as the conductive shielding layer, and the thickness of a single layer of purple copper foil is more than or equal to 50 microns; in step S1.3, at least three layers of red copper foil are used as the conductive shielding layer, and the thickness of a single layer of red copper foil is greater than or equal to 50 μm.
Further, a step S1.5 of conducting performance test is also included between the step S1.4 and the step 2; and taking the universal meter, respectively putting two meter needles of the universal meter on the purple copper foil wrapped outside the swing wire harness to be tested and the shielding layer outside the shielding three-way testing cable, starting buzzing test of the universal meter, if the buzzing sounds, enabling the purple copper foil wrapped outside the swing wire harness to be tested to be in conductive contact with the shielding layer outside the shielding three-way testing cable to meet the preset requirement, and otherwise, reprocessing the purple copper foil wrapped outside the swing wire harness to be tested until the buzzing sounds of the universal meter.
Further, in step S2.1, the differential voltage probe includes a sampling circuit board, a DC-DC isolated power supply line, and a sampling signal output coaxial cable;
one end of the DC-DC isolation power supply line is connected with a first isolation transformer, the other end of the DC-DC isolation power supply line is connected with a power supply input port of the sampling circuit board, and the outside of the DC-DC isolation power supply line is sequentially wrapped with a red copper foil, a red copper net and a red copper foil from inside to outside; the first isolation transformer is connected with a mains supply, an equivalent distributed capacitance between a primary winding and a secondary winding of the first isolation transformer is less than or equal to 0.5nF under the frequency of 30MHz, a secondary output end of the first isolation transformer floats to the ground, and a distributed capacitance of the secondary output end of the first isolation transformer to the ground under the no-load condition is less than or equal to 0.5nF under the frequency of 30 MHz;
the sampling signal output coaxial cable is externally wrapped with a double-layer wire mesh shielding sleeve, and the mesh diameter of the wire mesh is less than or equal to 200 meshes; one end of the sampling signal output coaxial cable is connected with the signal output end of the sampling circuit board, and the other end of the sampling signal output coaxial cable is connected with any one of the signal input channels of the oscilloscope;
the sampling circuit board is externally wrapped with a red copper foil, a red copper mesh and a red copper foil from inside to outside in sequence, the sampling circuit board is provided with two twisted-pair shielding test wires, and the tail ends of the two test wires are connected with test clamps.
Further, in step S5, the equivalent distributed capacitance between the primary winding and the secondary winding of the second isolation transformer is less than or equal to 0.5nF at a frequency of 30MHz, the secondary output terminal of the second isolation transformer floats to the ground, and the distributed capacitance of the secondary output terminal to the ground under an idle condition of the second isolation transformer is less than or equal to 0.5nF at a frequency of 30 MHz.
Further, in step S6, the step of measuring the conducted voltage interference signal between the signal line in the shielded three-way test cable and the grounding enclosure through the differential voltage probe is specifically that one test clip of the differential voltage probe is connected to a lead terminal corresponding to a connection terminal of each wire throwing to be tested of the wire throwing bundle of the shielded three-way test cable, and the other test clip is connected to a conductive shielding layer outside the wire throwing bundle to be tested of the shielded three-way test cable; sequentially wrapping a red copper net and a red copper foil outside the connecting terminal and the two test clamps of each swing wire to be tested of the swing wire harness to be tested from inside to outside; and measuring the conducted voltage interference signal between the signal line in the shielded three-way test cable and the grounding shell by using an oscilloscope.
Further, sequentially wrapping the connecting terminal of each wire throwing to be detected of the wire throwing bundle to be detected and the two test clamps from inside to outside with the purple copper net and the purple copper foil, namely, sequentially wrapping 3 layers of the purple copper nets with meshes not larger than 200 meshes on the connecting terminal of each wire throwing to be detected of the wire throwing bundle to be detected and the two test clamps from inside to outside, and continuously wrapping 3 layers of the purple copper foils on the outer parts of the purple copper nets in a seamless mode, wherein the thickness of the single layer of the purple copper foil is larger than or equal to 50 mu m.
Further, in step S6, the step of measuring the transient conducted voltage interference signal between any two points on the surface of the grounded enclosure through the differential voltage probe is specifically that two test clips of the differential voltage probe are respectively in conductive contact with any two points to be measured on the surface of the grounded enclosure, two test wires corresponding to the two test clips are both attached to the surface of the grounded enclosure, a purple copper foil tape is used to attach and encapsulate the test wires to the surface of the grounded enclosure, the test wires are in a flat and straight state, and the transient conducted voltage interference signal between any two points on the surface of the grounded enclosure is measured through an oscilloscope.
Furthermore, the test wire is attached to and packaged on the surface of the grounding shell by the red copper foil adhesive tape, specifically, at least three layers of red copper foils are adopted to shield the test wire, and the thickness of a single layer of red copper foil is more than or equal to 50 μm.
Compared with the prior art, the invention has the beneficial effects that:
1. the method for measuring the conducted interference signals in the strong electromagnetic environment reasonably constructs an outer shielding layer by adopting the shielded three-way test cable throwing line leading-out, the differential voltage probe for power supply isolation for shielding sampling and the isolated power supply oscilloscope for testing, and controls the additionally introduced background interference noise amplitude of test structures such as the differential voltage probe, the shielded three-way test cable throwing line and the like to be below 0.2V under the strong electromagnetic environment stronger than 1kV/m, thereby realizing the accurate measurement of the conducted voltage interference signals among the signal lines in the transmission cable of the circuit system, between the signal lines and the ground and between any two points on the surface of the grounding shell; the ground wire is connected in series with the small current indicating resistor for shielding, the coaxial shielding test cable is sampled and led out, the power supply oscilloscope is isolated for testing, the shielding layer is reasonably constructed, the background interference is not more than 0.1A, and the measurement of transient conducted ground current interference signals of the ground wire of the circuit system in the strong electromagnetic environment is realized. The invention measures the frequency range of the interference signal from direct current to 1GHz, provides support for accurately measuring the conducted interference signal in the strong electromagnetic environment, and has the characteristics of low background noise, good environmental electromagnetic interference resistance and convenient operation.
2. The shielding three-way test cable is proper in length, and the shielding layer is fully wrapped outside the shielding three-way test cable, so that interference is avoided.
3. According to the invention, through the conductivity test, before the step S2, the conductivity between the outer side of the swinging wire harness to be tested and the outer shielding layer of the shielding three-way test cable is confirmed through the universal meter, so that the subsequent measurement accuracy is ensured.
4. The differential voltage probe provided by the invention consists of a sampling circuit board, a DC-DC isolation power supply circuit and a sampling signal output coaxial cable, and has a better isolation and shielding effect after shielding treatment.
5. The two test clips of the differential voltage probe are respectively connected with the lead terminal corresponding to the wire throwing wiring terminal to be tested and the conductive shielding layer outside the wire throwing wiring harness to be tested of the shielding three-way test cable, so that a conducted voltage interference signal between a signal wire in the shielding three-way test cable and a grounding shell can be measured; the two test clips are respectively connected to any two points on the surface of the grounding shell and can also be used for measuring a conducted voltage interference signal between the any two points; the measuring method of the invention can realize the measurement of a plurality of interference signals only by changing the testing position of the testing clamp.
Drawings
FIG. 1 is a schematic diagram illustrating the detection of a signal interfering with the conducted voltage of a to-be-tested shunt winding of a shielded three-way test cable according to an embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating the detection of interference signals of conducted voltage between any two points on the surface of the grounded enclosure according to an embodiment of the present invention;
fig. 3 is a schematic diagram of detecting a conducted current interference signal of a ground line to be tested according to an embodiment of the invention.
The system comprises a signal transmission cable 1, a shielded three-way test cable 2, a chassis 3, a to-be-tested wire throwing 4, a system outer cylinder 5, a red copper plate 6, a coaxial double-layer shielded test cable 7, a non-inductive metal film resistor 8, an oscilloscope 9, a first isolation transformer 10 and a second isolation transformer 11.
Detailed Description
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention and the accompanying drawings, and it is obvious that the described embodiments do not limit the present invention.
The invention discloses a method for measuring conducted interference signals in a strong electromagnetic environment, which comprises the following steps:
s1, the shielded three-way test cable 2 is led out and connected by throwing line
S1.1, taking a section of shielded three-way test cable 2 wrapped with a shielding layer outside, and dividing all signal wires to be tested in the shielded three-way test cable into two parts to form corresponding throwing wires 4 to be tested;
s1.2, wrapping a conductive shielding layer on the outer side of the to-be-detected swing line 4, reserving wiring terminals at the end parts, and marking at each wiring terminal;
s1.3, forming a small hole in the middle of the shielding three-way test cable 2, and enabling the wiring terminals of the throwing wires 4 to be tested to penetrate out of the small hole to form a throwing wire harness to be tested; wrapping a conductive shielding layer outside the to-be-detected swing wire bundle and at a gap between the to-be-detected swing wire bundle and the small hole, and reserving a wiring terminal of each to-be-detected swing wire 4 in the to-be-detected swing wire bundle;
s1.4, connecting the shielded three-way test cable 2 processed in the step S1.3 between the signal transmission cable 1 outside the case 3 and a case matching cable socket for switching;
s2, differential Voltage Probe Shielding
S2.1, connecting a differential voltage probe with the bandwidth of more than or equal to 1GHz with an oscilloscope 9;
s2.2, connecting the testing end of the differential voltage probe with the lead terminal corresponding to the wiring terminal of each swing wire 4 to be tested in the swing wire bundle to be tested respectively;
s2.3, sequentially wrapping a purple copper net and a purple copper foil at the joint of the differential voltage probe and the swing wire harness to be tested from inside to outside, so that the shielding three-way test cable 2 is shielded from the differential voltage probe;
s3, connecting the grounding wire in series with a shielding current indicating resistor
S3.1, placing two red copper plates 6 in parallel on the same plane, and reserving a gap of less than or equal to 30mm between the two red copper plates 6;
s3.2, uniformly arranging n resistance values along the gap and marking as R0The non-inductive metal film resistor 8, wherein n is an integer greater than or equal to 1, two pins of each non-inductive metal film resistor 8 are respectively welded on the two copper plates 6, the n non-inductive metal film resistors 8 are connected in parallel to form a current indicating resistor R, wherein R ═ R0/n，R≤0.1Ω；
S3.3, connecting the whole body formed by the two red copper plates 6 and the current indicating resistor in series to a grounding wire to be tested;
s4, coaxial shielding test cable sampling leading-out
S4.1, taking the coaxial double-layer shielding test cable 7, enabling the core wire, the inner shielding layer and the outer shielding layer at one end of the coaxial double-layer shielding test cable 7 to be mutually insulated, and respectively welding the core wire and the inner shielding layer lead of the coaxial double-layer shielding test cable 7 to the two red copper plates 6 in the step S3;
s4.2, sequentially wrapping an insulating layer and a red copper foil outside the current indicating resistor, the core wire at one end of the coaxial double-layer shielding test cable 7, the lead wire of the inner shielding layer and the two red copper plates 6 from inside to outside;
s4.3, connecting the other end of the coaxial double-layer shielding test cable 7 with the oscilloscope 9;
s5, isolation power supply oscilloscope 9 test
Connecting the oscilloscope 9 with mains supply through a second isolation transformer 11;
s6, testing the conductive interference signal
And measuring a conducted voltage interference signal between a signal wire and the grounding shell in the shielded three-way test cable 2 through the differential voltage probe, or measuring a transient conducted voltage interference signal between any two points on the surface of the grounding shell through the differential voltage probe, or measuring a conducted current interference signal of the grounding wire to be measured through an oscilloscope.
By sequentially adopting the steps S1, S2 and S5, the accurate measurement of the conducted voltage interference signals among the signal lines and between the signal lines and the ground in the circuit system transmission cable under the strong electromagnetic environment can be realized; the step S2 and the step S5 are sequentially adopted, so that the accurate measurement of the transient voltage fluctuation interference signal between any two points on the surface of the machine shell under the strong electromagnetic environment can be realized; by sequentially adopting the steps S3, S4 and S5, the transient conduction current interference signal measurement of the circuit system ground wire under the strong electromagnetic environment can be realized.
A radiation electric field generated in a nearby environment in the operation process of a set of MV-grade pulse drive source system can reach 1kV/m magnitude at most, and radiation interference frequency bands at different stages are located in the range of 10kHz-800 MHz. As shown in fig. 1 and 2, on the platform of the pulse power system, a conducted voltage interference signal test between differential signal lines in the RS422 communication cable, a conducted voltage interference signal test between the differential signal lines and the ground shielding layer, and a conducted voltage interference signal test between any two points on the system ground shell are performed, which specifically includes the following steps:
(1) shielded three-way test cable 2 wire throwing-out
A section of shielding three-way test cable 2 which accords with RS422 communication is adopted to carry out switching between an end face plug of an RS422 communication signal transmission cable 1 and an RS422 cable socket matched with the wall of a power supply cabinet of a pulse drive source system, the total length of the shielding three-way test cable 2 is 100mm, every two signal wires in the shielding three-way test cable are twisted in pairs, the outer surface of the shielding three-way test cable 2 is wrapped and shielded by a double-layer wire mesh shielding sleeve, and the diameter of a wire mesh is 200 meshes; the sockets and plugs at two ends of the shielding three-way test cable 2 are respectively and sequentially matched with the plugs at the end surface of the RS422 communication signal transmission cable 1 and the RS422 cable sockets matched with the wall of the power supply case; the method comprises the following steps that 4 differential signal wires in a shielded three-way test cable 2 are divided into two parts to form respective to-be-tested throwing wires 4, the lengths of the 4 to-be-tested throwing wires 4 are smaller than or equal to 30mm, the 4 to-be-tested throwing wires 4 are wrapped by a purple copper foil with the thickness of 50 mu m, only 4 connecting terminals are exposed, and labels are made according to TX +, TX-, RX and RX in sequence; a small hole is formed in the middle of the shielding three-way test cable 2, 4 wiring terminals of the swing line 4 to be tested all penetrate through the small hole in the middle of the shielding three-way test cable 2 to form a swing line bundle to be tested, then a red copper foil with the thickness of 3 layers being 50 microns is adopted to wrap and shield the swing line bundle to be tested and a small hole gap of an outlet wire in the middle of the shielding three-way test cable 2, no gap is left, only the wiring terminal and the label of the swing line bundle to be tested are exposed, the shielding layer of the red copper foil is in good conductive contact with the outer shielding layer of the shielding three-way test cable 2, and the shielding layer of the red copper foil is reliably insulated from the wiring terminal of the swing line bundle to be tested; after the shielding treatment is finished, one probe of the universal meter is put on the original shielding outer sleeve of the shielding three-way testing cable 2, the other probe of the universal meter is put on the wrapped shielding layer of the purple copper foil, and the short circuit buzzing test of the universal meter is adopted, so that buzzing is performed, and the conductive contact is good;
(2) carrying out double-twisted shielding sampling on a differential voltage probe for power supply isolation;
a differential voltage probe with the bandwidth of 1GHz is adopted as a conducted interference voltage signal sampling probe between a signal wire of an RS422 communication cable and a grounding shell, and the differential voltage probe consists of two test wires, two test clamps, a sampling circuit board, a DC-DC isolation power supply circuit and a sampling signal output coaxial cable;
one end of the DC-DC isolation power supply line is connected with a power supply input port of the differential probe sampling circuit board, and the other end of the DC-DC isolation power supply line is connected with an output end socket of a first isolation transformer 10; the whole DC-DC isolation power supply line is tightly wrapped and shielded by adopting 3 layers of red copper foils with the thickness of 50 mu m, then adopts 3 layers of red copper nets with meshes of 200 meshes to continuously wrap and shield without gaps, and finally adopts 3 layers of red copper foils with the thickness of 50 mu m to tightly wrap and shield outside the red copper nets, wherein the shielding layers of the DC-DC isolation power supply line are in continuous conductive contact and have no obvious breakpoint or gap; the first isolation transformer 10 is used for isolating the input end of a commercial power supply and a DC-DC isolation power supply line, the equivalent distributed capacitance between a primary winding and a secondary winding of the first isolation transformer 10 is not more than 0.5nF under the frequency of 30MHz, the secondary output end of the first isolation transformer 10 floats to the ground, and the distributed capacitance of the secondary output end to the ground under the no-load condition of the first isolation transformer 10 is not more than 0.5nF under the frequency of 30 MHz;
the differential voltage probe sampling signal output coaxial cable is wrapped and shielded by a double-layer metal wire mesh shielding sleeve, the diameter of a wire mesh is 200 meshes, one end of the sampling signal output coaxial cable is connected with the signal output end of a sampling circuit board, and the other end of the sampling signal output coaxial cable is connected with 94 signal input channels 1 of an oscilloscope;
the differential voltage probe sampling circuit board is characterized in that a red copper foil with the thickness of 50 mu m is adopted to tightly wrap a shield, then a red copper net with the mesh of 200 meshes is adopted to seamlessly and continuously wrap the shield by 3 layers, finally the red copper foil with the thickness of 50 mu m is used to tightly wrap the shield outside the red copper net, and the sampling circuit board is insulated from a shielding layer;
two test wires of the differential voltage probe are twisted after being led out by a sampling circuit board, a red copper foil with the thickness of 3 layers being 50 mu m is adopted to tightly wrap the shielding, then a red copper net with the meshes of 200 meshes is adopted to seamlessly and continuously wrap the shielding, finally the red copper foil with the thickness of 3 layers being 50 mu m is used to tightly wrap the shielding outside the red copper net, and only two test clips are exposed at the tail ends of the two twisted shielding test wires;
for the conducted voltage interference signal measurement between the differential signal lines TX +, TX-in the shielded three-way test cable 2: two test clips of the differential voltage probe are respectively connected with a TX + and a TX-swing wire connecting terminal, and then a red copper net with 3 layers of meshes of 200 meshes is integrally and seamlessly wrapped outside all the swing wire harness connecting terminals to be tested and the two test clips, and a red copper foil with the thickness of 50 microns is continuously and seamlessly wrapped outside the red copper net for shielding; finally, a shielding sleeve of the shielding three-way test cable 2, a to-be-tested throwing wire harness shielding layer of the shielding three-way test cable 2, a throwing wire lead terminal, a test clamp outer wrapping shielding layer, two double-twisted test wire shielding layers of a differential voltage probe, a differential voltage probe sampling circuit board shielding layer, a differential voltage probe sampling signal output coaxial cable shielding layer and a combination part between the differential voltage probe DC-DC isolation power supply circuit shielding layers are all connected by adopting a purple copper foil adhesive tape with the thickness of 3 layers being 50 mu m for conducting shielding without gaps, so that the shielding three-way test cable 2 to the differential probe and the input end of a measurement oscilloscope 9 are all shielded, and the shielding layers are connected with a grounding case shell into a conductive whole through an RS422 communication signal cable shielding layer;
for the measurement of the conducted voltage interference signal between the differential signal line TX + the grounded machine shell in the shielded three-way test cable 2: one test clamp of the differential voltage probe is connected with a TX + wire throwing wiring terminal, the other test clamp of the differential voltage probe is directly connected with a conductive shielding layer coated outside a wire throwing bundle to be tested of the shielded three-way test cable 2 nearby, then a red copper net with 200 meshes is integrally and seamlessly coated outside all the wire throwing wiring terminals to be tested and the two test clamps, and a red copper foil with the thickness of 50 mu m is continuously and seamlessly coated outside the red copper net for shielding; the shielding three-way test cable 2 is connected to the differential probe and all shielding layers at the input end of the measurement oscilloscope 9 into a whole in a seamless way, and then is connected with the grounding case shell into a conductive whole through the signal cable shielding layer;
(3) testing by an isolation power supply oscilloscope 9;
the oscilloscope 9 for conducting interference signal data test and waveform display is placed outside a strong electromagnetic environment, and the bandwidth of the oscilloscope 9 is 1 GHz; a second isolation transformer 11 is adopted for isolation between the power supply input end of the oscilloscope 9 and the mains supply, the equivalent distributed capacitance between the primary winding and the secondary winding of the second isolation transformer 11 is less than 0.5nF under the frequency of 30MHz, the secondary output end of the second isolation transformer 11 floats to the ground, and the distributed capacitance of the secondary output end to the ground under the no-load condition of the second isolation transformer 11 is less than 0.5nF under the frequency of 30 MHz; opening an isolation power supply oscilloscope 9, butting the output end of a sampling signal output coaxial cable of an isolation power supply differential voltage probe with a cable input interface channel 1 of the oscilloscope 9, and measuring a conduction interference signal in the running process of a pulse drive source system;
the maximum amplitude of the 80MHz interference voltage signal of the TX + pair TX-measured in the test is 1.5V, and the maximum amplitude of the 80MHz interference signal of the TX + pair grounding shielding layer is 4.5V.
Under the test conditions, only two test clips of the differential voltage probe are clamped together for short circuit, the test clips are not connected with a wire throwing wiring terminal or a shielding layer any more, but the two test clips are still placed at TX + pair TX-test positions and are not changed, in other embodiments of the invention, the shielding mode is kept unchanged, in the running process of a pulse driving source system, under a 1 kV/m-level strong electromagnetic environment, an oscilloscope 9 measures that the maximum amplitude of an inductively coupled 80MHz background interference noise signal after the differential voltage probe is short-circuited is less than or equal to 0.2V, and the test method proves that the RS422 communication signal wire TX + pair TX-interference voltage signal and the TX + pair grounding shielding layer interference voltage signal are accurately measured, and the background interference noise signal of the differential voltage probe does not generate obvious errors on the test result.
Measuring transient conducted voltage interference signals between optional points T1 and T2 on the surface of a grounded enclosure (diameter is 1m, length is 1.8m) of the pulse drive source system, wherein the linear distance between the points T1 and T2 is about 0.8m, and all parts of the pulse drive source system are arranged on the system outer cylinder 5;
(1) power supply isolated differential voltage probe double-twisted shielding sampling
The differential voltage probe is a Tack P5200 type differential voltage probe and is used as a conducted interference voltage signal sampling probe between a RS422 communication cable signal line and a shell, and the differential voltage probe is composed of two test lines, two test clamps, a sampling circuit board, a DC-DC isolation power supply line and a sampling signal output coaxial cable;
one end of the DC-DC isolation power supply line is connected with a power supply input port of the differential probe sampling circuit board, and the other end of the DC-DC isolation power supply line is connected with an output end socket of a first isolation transformer 10; the whole DC-DC isolation power supply line is tightly wrapped and shielded by adopting 3 layers of red copper foils with the thickness of 50 mu m, then adopts 3 layers of red copper nets with meshes of 200 meshes to continuously wrap and shield without gaps, and finally adopts 3 layers of red copper foils with the thickness of 50 mu m to tightly wrap and shield outside the red copper nets, wherein the shielding layers of the DC-DC isolation power supply line are in continuous conductive contact and have no obvious breakpoint or gap; the first isolation transformer 10 is used for isolating the input end of a commercial power supply and a DC-DC isolation power supply line, the equivalent distributed capacitance between a primary winding and a secondary winding of the first isolation transformer 10 is not more than 0.5nF under the frequency of 30MHz, the secondary output end of the first isolation transformer 10 floats to the ground, and the distributed capacitance of the secondary output end to the ground under the no-load condition of the first isolation transformer 10 is not more than 0.5nF under the frequency of 30 MHz;
the differential voltage probe sampling signal output coaxial cable is wrapped and shielded by a double-layer metal wire mesh shielding sleeve, the diameter of a wire mesh is 200 meshes, one end of the sampling signal output coaxial cable is connected with the signal output end of a sampling circuit board, and the other end of the sampling signal output coaxial cable is connected with 94 signal input channels 1 of an oscilloscope;
the differential voltage probe sampling circuit board is characterized in that a red copper foil with the thickness of 50 mu m is adopted to tightly wrap a shield, then a red copper net with the mesh of 200 meshes is adopted to seamlessly and continuously wrap the shield by 3 layers, finally the red copper foil with the thickness of 50 mu m is used to tightly wrap the shield outside the red copper net, and the sampling circuit board is insulated from a shielding layer;
two test wires of the differential voltage probe are twisted after being led out by a sampling circuit board, a red copper foil with the thickness of 3 layers being 50 mu m is adopted to tightly wrap the shielding, then a red copper net with the meshes of 200 meshes is adopted to seamlessly and continuously wrap the shielding, finally the red copper foil with the thickness of 3 layers being 50 mu m is used to tightly wrap the shielding outside the red copper net, and only two test clips are exposed at the tail ends of the two twisted shielding test wires;
directly electrically contacting one test clip of the differential voltage probe with a point to be tested T1 on the surface of the grounded shell, electrically contacting the other test clip of the differential voltage probe with another point to be tested T2 on the surface of the shell, and tightly attaching two test wires of the differential voltage probe between a point T1 and a point T2 to the surface of the shell and straightening the test wires; flattening by adopting a purple copper foil adhesive tape with the thickness of 3 layers being 50 mu m, and tightly wrapping and adhering two straight shielding test lines between a point T2 and a point T1, two test clamps and two test points on the surface of a grounding machine shell, wherein the shielding layer of the purple copper foil adhesive tape is in conductive communication with the grounding machine shell, and the effect is equivalent to that the test points, the test lines and the test clamps are embedded in a closed shielding body formed by the machine shell and the shielding layer of the purple copper foil adhesive tape; connecting the grounding case, the outer shielding layer of the test clamp and all the shielding layers from the differential probe to the input end of the measurement oscilloscope 9 into a conductive shielding whole in a seamless manner;
(2) isolated power supply oscilloscope 9 test
The oscilloscope 9 for conducting interference signal data test and waveform display is placed outside a strong electromagnetic environment, and the bandwidth of the oscilloscope 9 is 1 GHz; a second isolation transformer 11 is adopted for isolation between the power supply input end of the oscilloscope 9 and the mains supply, the equivalent distributed capacitance between the primary winding and the secondary winding of the second isolation transformer 11 is less than 0.5nF under the frequency of 30MHz, the secondary output end of the second isolation transformer 11 floats to the ground, and the distributed capacitance of the secondary output end to the ground under the no-load condition of the second isolation transformer 11 is less than 0.5nF under the frequency of 30 MHz; opening an isolation power supply oscilloscope 9, butting the output end of a sampling signal output coaxial cable of an isolation power supply differential voltage probe with a cable input interface channel of the oscilloscope 9, and measuring a conduction interference signal in the running process of a pulse drive source system;
the maximum amplitude of the T1 to the 80MHz interference voltage signal on the T2 is 2V; under the test condition, the postures of the two test clamps of the differential voltage probe are kept unchanged, the two test clamps are disconnected with T1 and T2, a section of conducting wire with the length of about 0.82m is distributed along the T1 to the T2 in the shielding layer of the purple copper foil, two ends of the conducting wire are respectively connected with the two test clamps, but the test clips and the leads in the red copper foil shielding layer are not in electric contact with the point T1, the point T2 and the surface of the grounding machine shell, which is equivalent to that the two test clips and the leads are insulated and buried in a small closed space formed by the red copper wave shielding layer and the surface of the machine shell, in other embodiments of the invention, the shielding mode is kept unchanged, and the maximum amplitude of the background interference noise signal of the differential voltage probe measured by a test under 80MHz is less than or equal to 0.2V, which proves that the method for testing the transient interference voltage signal between two points on the surface of the grounding shell is accurate, and the background interference noise signal of the differential voltage probe can not generate obvious errors on the test result.
In addition, under the strong electromagnetic environment of 1kV/m level, the conduction current interference signal on the same set of MV level pulse drive source system shell grounding wire is tested:
(1) grounding wire series connection shielding small current indicating resistor
As shown in fig. 3, two copper plates 6 with the thickness of 0.5mm are arranged in parallel, the two copper plates 6 are positioned on the same plane, and the distance between the two copper plates 6 is 30 mm; using 10 nominal resistances R0The noninductive metal film resistors 8 of 1 omega are uniformly distributed along the reserved gaps of the two red copper plates 6, two pins of each noninductive metal film resistor 8 are respectively welded on the two red copper plates 6, and the current indicating resistor R formed by connecting 10 metal film resistors in parallel is 0.1 omega; then the two red copper plates 6 and the welded current indicating resistor are integrally connected in series to a grounding wire of a shell of the pulse drive source system;
(2) sampling and leading out a coaxial shielding test cable;
respectively poking a core wire, an inner shielding layer and an outer shielding layer at one end of a coaxial double-layer shielding test cable 7, insulating the core wire, the inner shielding layer and the outer shielding layer from each other, exposing respective leads, and respectively welding the cable core wire and the inner shielding layer leads to two copper plates at two ends of a current indicating resistor, wherein the lengths of the welding leads are all less than 30 mm; the current indicating resistor, the two red copper plates 6, the cable core wire welding lead and the inner shielding layer lead are all tightly wrapped by an insulating adhesive tape, then at least 3 layers of red copper foils with the thickness of 50 mu m are used for wrapping and shielding outside the insulating adhesive tape, the red copper foil shielding layer is insulated and separated from the current indicating resistor and the copper plates by the insulating adhesive tape, and the outer shielding layer of the coaxial double-layer shielding test cable 7 is seamlessly wrapped and conductively connected with the red copper foil shielding layer; the shielding layer of the purple copper foil is conductively connected with the grounded near end of the current indicating resistor to realize shielding; the other end of the coaxial double-layer shielding test cable 7 is connected to the oscilloscope 9, a signal output by the other end of the coaxial double-layer shielding test cable 7 is a voltage signal U, and a current signal can be converted into a current signal conducted by a grounding wire of the current indicating resistor according to the U/R (U/R) of 10U;
(3) testing by an isolation power supply oscilloscope 9;
the oscilloscope 9 for conducting interference signal data test and waveform display is placed outside a strong electromagnetic environment, and the bandwidth of the oscilloscope 9 is 1 GHz; a second isolation transformer 11 is adopted for isolation between the power supply input end of the oscilloscope 9 and the mains supply, the equivalent distributed capacitance between the primary winding and the secondary winding of the second isolation transformer 11 is less than 0.5nF under the frequency of 30MHz, the secondary output end of the second isolation transformer 11 floats to the ground, and the distributed capacitance of the secondary output end to the ground under the no-load condition of the second isolation transformer 11 is less than 0.5nF under the frequency of 30 MHz; opening an isolation power supply oscilloscope 9, butting the output end of the current indicating resistance coaxial shielding test cable with a cable input interface channel 1 of the oscilloscope 9, and measuring a ground wire conduction current interference signal;
the amplitude of the 1kHz half-wave sine conduction current interference signal measured by the test is 0.5A, the amplitude of the 80MHz conduction current interference signal measured by the test is 3.3A, and the background noise amplitude on the current waveform baseline is less than 0.1A.
The above description is only an embodiment of the present invention, and is not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings, or applied directly or indirectly to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. A method for measuring conducted interference signals in a strong electromagnetic environment is characterized by comprising the following steps:
s1, the shielded three-way test cable (2) is led out and connected by throwing line
S1.1, taking a section of shielded three-way test cable (2) wrapped with a shielding layer outside, and dividing all signal wires to be tested in the shielded three-way test cable into two parts to form corresponding throwing lines (4) to be tested;
s1.2, wrapping a conductive shielding layer on the outer side of the to-be-detected swing line (4), reserving wiring terminals at the end parts, and marking at each wiring terminal;
s1.3, forming a small hole in the middle of the shielding three-way test cable (2), and enabling a wiring terminal of each throwing line (4) to be tested to penetrate out of the small hole to form a throwing line bundle to be tested; a conductive shielding layer is wrapped outside the to-be-detected swing wire bundle and at a gap between the to-be-detected swing wire bundle and the small hole, and a wiring terminal of each to-be-detected swing wire (4) in the to-be-detected swing wire bundle is reserved;
s1.4, connecting the shielded three-way test cable (2) processed in the step S1.3 between a signal transmission cable (1) outside the case and a cable socket matched with the case (3) for switching;
s2, differential Voltage Probe Shielding
S2.1, connecting a differential voltage probe with the bandwidth of more than or equal to 1GHz with an oscilloscope (9);
s2.2, connecting the testing end of the differential voltage probe with the lead terminal corresponding to the wiring terminal of each swing wire (4) to be tested in the swing wire bundle to be tested respectively;
s2.3, sequentially wrapping a purple copper net and a purple copper foil at the joint of the differential voltage probe and the swing wire harness to be tested from inside to outside, so that the shielding three-way test cable (2) is shielded from the differential voltage probe;
s3, connecting the grounding wire in series with a shielding current indicating resistor
S3.1, placing two red copper plates (6) in parallel on the same plane, and reserving a gap which is less than or equal to 30mm between the two red copper plates (6);
s3.2, uniformly arranging n resistance values along the gap and marking as R0The non-inductive metal film resistor (8) is characterized in that n is an integer larger than or equal to 1, two pins of each non-inductive metal film resistor (8) are respectively welded on the two copper plates (6), the n non-inductive metal film resistors (8) are connected in parallel to form a current indicating resistor R, wherein R is R0/n，R≤0.1Ω；
S3.3, connecting the whole body formed by the two red copper plates (6) and the current indicating resistor in series to the grounding wire to be tested;
s4, coaxial shielding test cable sampling leading-out
S4.1, taking the coaxial double-layer shielding test cable (7), enabling the core wire, the inner shielding layer and the outer shielding layer at one end of the coaxial double-layer shielding test cable to be mutually insulated, and respectively welding the core wire and the inner shielding layer lead of the coaxial double-layer shielding test cable (7) to the two red copper plates (6) in the step S3;
s4.2, sequentially wrapping an insulating layer and a red copper foil outside the current indicating resistor, the core wire at one end of the coaxial double-layer shielding test cable (7), the lead wire of the inner shielding layer and the two red copper plates (6) from inside to outside;
s4.3, connecting the other end of the coaxial double-layer shielding test cable (7) with the oscilloscope (9);
s5, isolation power supply oscilloscope (9) test
Connecting the oscilloscope (9) with commercial power through a second isolation transformer (11);
s6, testing the conductive interference signal
And measuring a conducted voltage interference signal between a signal wire and a grounding shell in the shielded three-way test cable (2) through the differential voltage probe, or measuring a transient conducted voltage interference signal between any two points on the surface of the grounding shell through the differential voltage probe, or measuring a conducted current interference signal of a grounding wire to be measured through an oscilloscope.
2. The method for measuring the conducted interference signal in the strong electromagnetic environment according to claim 1, wherein: in the step S1.1, the length of the shielded three-way test cable (2) is less than or equal to 100mm, the shielded cable is wrapped and shielded by a double-layer metal wire mesh shielding sleeve, and the mesh diameter of a metal wire mesh is less than or equal to 200 meshes; every two of the signal wires in the shielded three-way test cable (2) are twisted in pairs.
3. The method according to claim 2, wherein the method comprises the following steps: in the step S1.1, the length of the to-be-tested swing line (4) is less than or equal to 30 mm; in the step S1.2, at least three layers of purple copper foils are adopted as the conductive shielding layer, and the thickness of a single layer of purple copper foil is more than or equal to 50 microns; in step S1.3, at least three layers of red copper foil are used as the conductive shielding layer, and the thickness of a single layer of red copper foil is greater than or equal to 50 μm.
4. The method according to claim 3, wherein the method comprises the following steps: step S1.5 is further included between step S1.4 and step 2, and the conductivity test: and taking the universal meter, respectively putting two meter pins of the universal meter on the purple copper foil wrapped outside the swing wire harness to be tested and the shielding layer outside the shielding three-way testing cable (2), starting buzzing test of the universal meter, if the buzzing sounds, enabling the purple copper foil wrapped outside the swing wire harness to be tested and the shielding layer outside the shielding three-way testing cable (2) to be in conductive contact with each other to meet preset requirements, and if the buzzing sounds do not sound, reprocessing the purple copper foil wrapped outside the swing wire harness to be tested until the buzzing sounds of the universal meter are sounded.
5. The method according to claim 4, wherein the method comprises the following steps: in the step S2.1, the differential voltage probe comprises a sampling circuit board, a DC-DC isolation power supply line and a sampling signal output coaxial cable;
one end of the DC-DC isolation power supply line is connected with a first isolation transformer (10), the other end of the DC-DC isolation power supply line is connected with a power supply input port of the sampling circuit board, and the outside of the DC-DC isolation power supply line is sequentially wrapped with a red copper foil, a red copper net and a red copper foil from inside to outside; the first isolation transformer (10) is connected with a mains supply, an equivalent distributed capacitance between a primary winding and a secondary winding of the first isolation transformer (10) is less than or equal to 0.5nF under the frequency of 30MHz, a secondary output end of the first isolation transformer (10) is floated, and a distributed capacitance of the secondary output end of the first isolation transformer (10) to the ground under the no-load condition is less than or equal to 0.5nF under the frequency of 30 MHz;
the sampling signal output coaxial cable is externally wrapped with a double-layer wire mesh shielding sleeve, and the mesh diameter of the wire mesh is less than or equal to 200 meshes; one end of the sampling signal output coaxial cable is connected with the signal output end of the sampling circuit board, and the other end of the sampling signal output coaxial cable is connected with any one of the signal input channels of the oscilloscope (9);
the sampling circuit board is externally wrapped with a red copper foil, a red copper mesh and a red copper foil from inside to outside in sequence, the sampling circuit board is provided with two twisted-pair shielding test wires, and the tail ends of the two test wires are connected with test clamps.
6. The method according to claim 5, wherein the method comprises the following steps: in step S5, the equivalent distributed capacitance between the primary winding and the secondary winding of the second isolation transformer (11) is less than or equal to 0.5nF at a frequency of 30MHz, the secondary output terminal of the second isolation transformer (11) floats to the ground, and the distributed capacitance of the secondary output terminal to the ground under an idle condition of the second isolation transformer (11) is less than or equal to 0.5nF at a frequency of 30 MHz.
7. The method according to claim 6, wherein the method comprises the following steps: in the step S6, the measurement of the conducted voltage interference signal between the signal line in the shielded three-way test cable (2) and the grounded enclosure through the differential voltage probe is specifically that one test clip of the differential voltage probe is connected to a lead terminal corresponding to a terminal of each to-be-tested swing wire (4) of the to-be-tested swing wire harness of the shielded three-way test cable (2), and the other test clip is connected to a conductive shielding layer outside the to-be-tested swing wire harness of the shielded three-way test cable (2); then sequentially wrapping the connecting terminal of each to-be-tested throwing line (4) of the to-be-tested throwing line bundle and the two test clamps with a red copper net and a red copper foil from inside to outside; and measuring a conducted voltage interference signal between the signal wire in the shielded three-way test cable (2) and the grounding shell by using an oscilloscope (9).
8. The method according to claim 7, wherein the method comprises the following steps: and sequentially wrapping the connecting terminal of each to-be-tested throwing line (4) of the to-be-tested throwing line bundle and the two test clamps from inside to outside by a red copper net and a red copper foil, wherein the connecting terminal of each to-be-tested throwing line (4) of the to-be-tested throwing line bundle and the two test clamps from inside to outside are sequentially wrapped by 3 layers of red copper nets with meshes not larger than 200 meshes, the red copper nets are continuously wrapped by 3 layers of red copper foils from outside to inside, and the thickness of the single layer of red copper foil is larger than or equal to 50 mu m.
9. The method according to claim 6, wherein the method comprises the following steps: in step S6, the step of measuring the transient conducted voltage interference signal between any two points on the surface of the grounded enclosure through the differential voltage probe is specifically that two test clips of the differential voltage probe are respectively in conductive contact with any two points to be measured on the surface of the grounded enclosure, two test wires corresponding to the two test clips are both attached to the surface of the grounded enclosure, a purple copper foil tape is used to attach and encapsulate the test wires to the surface of the grounded enclosure, the test wires are in a flat and straight state, and the transient conducted voltage interference signal between any two points on the surface of the grounded enclosure is measured through an oscilloscope (9).
10. The method according to claim 9, wherein the method comprises the following steps: the method for jointing and packaging the test wire on the surface of the grounding shell by adopting the red copper foil adhesive tape comprises the steps of adopting at least three layers of red copper foils to shield the test wire, wherein the thickness of a single layer of red copper foil is more than or equal to 50 mu m.
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| CN113945746A (en) * | 2021-08-30 | 2022-01-18 | 中国电力科学研究院有限公司 | Converter station field transient interference testing device |
| CN116660671B (en) * | 2023-07-28 | 2023-09-22 | 北京芯可鉴科技有限公司 | Broadband transient interference measurement influence factor verification method and device |
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