CN101478118A - Design method for protecting chamber shielding body - Google Patents
Design method for protecting chamber shielding body Download PDFInfo
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- CN101478118A CN101478118A CNA2009100606519A CN200910060651A CN101478118A CN 101478118 A CN101478118 A CN 101478118A CN A2009100606519 A CNA2009100606519 A CN A2009100606519A CN 200910060651 A CN200910060651 A CN 200910060651A CN 101478118 A CN101478118 A CN 101478118A
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Abstract
The invention relates to a design method for a protective chamber shield body, which comprises the adoption of the mode to combine actual measurement and computation. The design method has the following steps: the characteristics and the strength of the interference source of a transformer substation are procured according to substantive actual measurement on the field; a series of immunity tests are conducted on the equipment partially installed in a protective chamber; finally, the shield effectiveness of the protective chamber is proposed according to the interference strength adopted in the tests and the difference of strength of the interference sources in the transformer substation; and finally, the design method for several key parts of the protective chamber are given, and comprises the steps of the calculation procedure of the shield effectiveness of the shield body, the selection of the materials of the shield body, control of the conduction continuity of the shield body, treatment of perforated cables, and special shielding measures of special positions.
Description
Technical field
The invention belongs to high voltage power transmission and transforming engineering electromagnetic compatibility field, is a kind of method for designing that is applied to high voltage substation protection chamber shielding body specifically.
Background technology
It is the trend that present project of transmitting and converting electricity is built that 500kV transformer station is installed in secondary device in 500kV and the 220kV switch yard in the layer distributed mode.Because complexity, the severity of the electromagnetic environment in 500kV switch place, make people be installed in the problem statement into questions such as fail safe, functional reliability of on-the-spot secondary device to these.The electromagnetic environment of trouble free service is provided for the secondary device of giving on-the-spot operation; adopting the protection cell of shielding to solve protection and transfer the contradiction of The Application of Technology and forceful electric power magnetic environment as jamproof measure, is domestic 500kV transformer substation construction and the existing a kind of mode of operation.
The shielding action, shielding construction, protection cell of protection cell other effects that should contain; and Immunity Performance how to examine protection equipment wherein; remain a problem that does not thoroughly solve up till now; because no unified standard, to such an extent as in the middle of design and the construction, problem is continuous; the passage of big structure, turnover cable to the protection cell; little of concrete technological problems, as the installation of window, filter configuration all hardship take a lot of trouble thing, had a strong impact on design and engineering construction.
Summary of the invention
The purpose of this invention is to provide a kind of method for designing of the protection chamber shielding body of the clean electromagnetic environment of safety being provided for the secondary device reliably working.
To achieve these goals, the method applied in the present invention is:
First step:, obtain the characteristic and the intensity of the interference source of transformer station according to a large amount of field measurements;
Second step: the equipment that part is installed in the protection cell carries out a series of immunity experiment;
Third step: the difference of the intensity of interference source in interference intensity that adopts in the comparative test and the transformer station, if self immunity to interference performance of secondary device can satisfy the condition in transformer station's high-voltage switch gear site safety work, then protect the special shielding measure of cell just can not consider; If self immunity to interference performance of secondary device can not satisfy the condition in transformer station's high-voltage switch gear site safety work, then protect the screening effectiveness of cell to design according to the 4th step;
The 4th step: the several key parts according to the protection cell provides clear and definite method for designing:
Generally except low frequency magnetic field, most of metal material can provide 100dB above screening effectiveness.But in real work, it also is very difficult reaching the above screening effectiveness of 80dB.This is because the screening effectiveness of shield not only depends on the structure of shield.Shield will satisfy the basic principle of electromagnetic shielding.The basic principle of electromagnetic shielding has two:
(1) the conduction continuity of shield: this refers to whole shield must be complete, a continuous electric conductor.This point implement very difficult.Because the shield of a complete closed is without any use value.Have a lot of holes seam on the protection cell of a practicality and cause shielding: ventilating opening, aperture, different piece in conjunction with the slit etc.Because these cause conducting electricity discontinuous factor and exist, if the designer does not consider how to handle, the screening effectiveness of shield is often very low, even does not have screening effectiveness when design.
(2) conductor that directly passes shield can not be arranged: the shield that screening effectiveness is high again, in case there is lead directly to pass shield, its screening effectiveness can lose more than 99.9% (60dB).Have a large amount of cables on the real protection cell and pass (going into), comprising signal cable and power cable, if these cables are not carried out appropriate processing (shielding or filtering), these cables can damage shield greatly.
When the present invention provides self immunity to interference performance when secondary device and can not satisfy condition in transformer station's high-voltage switch gear site safety work, the method for designing of the several key parts of protection cell.Comprising the selection of shield screening effectiveness computational methods, shield material, the successional control of conduction of shield, the processing of perforation cable and the special shielding measure of privileged sites.
Embodiment
The present invention is further detailed explanation below in conjunction with embodiment, but this embodiment should not be construed as limitation of the present invention.
Shield screening effectiveness computational methods:
When electromagnetic wave incided a hole, its effect was equivalent to a dipole antenna, and when the length of hole reached λ/2, its radiation efficiency the highest (irrelevant with the width of hole) that is to say, whole energy emissions that it can the excitation hole be gone out.
For a thickness is hole on 0 material, and in the far-field region, the screening effectiveness that (causes the polarised direction of maximum leakage) under the worst case (screening effectiveness may be bigger under the actual conditions) computing formula is:
SE＝100-20lgL-20lgf+20lg[1+2.3lg(L/H)](dB) (1)
If L 〉=λ/2, SE=0 (dB) (2)
Each amount in the formula: L is the length (mm) in slit, and H is the width (mm) in slit, and f is the frequency (MHz) of incident electromagnetic wave.
In the near-field region, the leakage of hole is also relevant with the characteristic of radiation source.When radiation source was electric field source, the leakage of hole was during than the far field little (screening effectiveness height), and when radiation source is magnetic field sources, and the leakage of hole is during than the far field big (screening effectiveness is low).The near-field region, the electromagnetic shielding computing formula of hole is:
If the impedance Z of radiation source circuit
C7.9f/D,
SE＝48+20lg?Z
C-20lgLf+20lg[1+2.3lg(L/H)] (3)
If Z
C＜7.9f/D,
SE＝20lg[(D/L)+20lg(1+2.3lg(L/H)] (4)
In the formula: the impedance (Ω) of Zc=radiation source circuit, D is the distance (m) of hole to radiation source, and L, H are hole length and width (mm), and f is electromagnetic frequency (MHz).
Be described as follows:
1. in formula (4), it doesn't matter for screening effectiveness and electromagnetic frequency.
2. in most cases, circuit satisfies the condition of formula (3), and screening effectiveness at this moment is greater than the screening effectiveness under formula (4) condition.
3. for magnetic field sources, screening effectiveness and hole are to the distance dependent of radiation source, and distance is near more, then leak big more.
Consider the situation of a plurality of holes: when N measure-alike hole is arranged in together, and during close proximity (distance is less than λ/2), the screening effectiveness that causes drops to 201gN/2.Hole on coplanar not can not increase leakage, because its radiation direction difference, these characteristics can be used for avoiding some radiation strong excessively in design.
Except the size that makes hole much smaller than electromagnetic wavelength, reduce beyond hole leaks away from methods such as holes with radiation source as far as possible, the degree of depth that increases hole also can reduce the leakage of hole, the principle of Here it is cut-off waveguide.
The selection of shield material:
Should note the problem of the following aspects for the selection of protection chamber shielding body material:
(1) conductivity of material and magnetic conductivity are good more, and screening effectiveness is high more, but actual metal material can not be taken into account this two aspects, and for example the conductivity of copper is fine, but magnetic conductivity is very poor; The magnetic conductivity of iron is fine, but conductivity is relatively poor.Should use what material, according to concrete shielding mainly rely on reflection loss, still absorption loss decides and stresses conductivity or magnetic conductivity;
When (2) frequency was lower, absorption loss was very little, and reflection loss is the dominant mechanism of screening effectiveness, improve reflection loss as far as possible;
(3) reflection loss is relevant with the characteristic of radiation source, and for the electric field radiation source, reflection loss is very big; For the magnetic field radiation source, reflection loss is very little.Therefore, mainly rely on the absorption loss of material, should select for use the higher material of magnetic permeability to do shielding material for the shielding in magnetic field radiation source.
(4) reflection loss and shield are to the distance dependent of radiation source, and for the electric field radiation source, distance is near more, and then reflection loss is big more; For the magnetic field radiation source, distance is near more, and then reflection loss is more little; The correct character of judging radiation source determines that it should still away from shield, be an important content of structural design near shield.
When (5) frequency was higher, absorption loss was main shielding mechanism, was that electric field radiation source or magnetic field radiation source relation are little with radiation source at this moment.
(6) electric field wave is the easiest shielding, plane wave secondly, the magnetic field ripple is the most difficult shielding.Especially (1KHz is following) low frequency magnetic field is difficult to shielding.For low frequency magnetic field, adopt high magnetic conductive material, even the material that adopts high conductivity material and high magnetic conductive material to combine.
The successional control of conduction of protection chamber shielding body:
About the successional control of conduction of protection chamber shielding body, should note the problem of the following aspects.
When ventilation, printing opacity, Jia Shui, measurement etc. need, perforate on the protection cell, be to improve the effectiveness of equipment, should adopt the eyelet shielding of woven wire.Relating to parameters such as the size of the screening effectiveness of eyelet and electromagnetic frequency, eyelet and quantity.
For the screening effectiveness that improves eyelet can be taked following measure:
(1) on the heavy caliber eyelet, covers woven wire, silk screen is contacted with shield well;
(2) change macropore into aperture;
(3) adopt cut-off wave guide plate ventilating opening;
(4) be coated with the shield glass of woven wire at the printing opacity mouth;
(5) on the hole that needs water, hermetic seal, fill up the woven wire that contains materials such as rubber.
Provide several woven wire shielding materials commonly used below.
1. all-metal mesh pad
The all-metal mesh pad is a kind of Weaving type metal gasket silk screen bar of flexible, conduction, is used for the seam crossing of casting of electronic device, and effective electromagnetic shielding is provided.During application, casting or mach housing are selected the all-metal mesh pad of square-section for use, and the sheet metal housing is selected the all-metal mesh pad of circular cross-section for use, and decrement is about 25% of a former height.
2. environmental sealing wire mesh pad
The environmental sealing wire mesh pad is by braided metal silk screen and rubber be combined into, and the decapacitation of environmental sealing wire mesh pad provides outside the effective electromagnetic shielding, and effective environmental sealing can also be provided.The fixedly seam crossing or the movement joint place that can be used for casting of electronic device, for example crack between a door and its frame etc.General decrement is about 25% of a former height.
3. woven wire shield glass
The woven wire shield glass is that woven wire is pressed between the layer glass, and effective electromagnetic shielding can not only be provided, and effective printing opacity can also be provided.The watch window that can be used for electronic equipment, for example gauge outfit, numeral or image diplay etc.
4. aluminum honeycomb ventilating board
Aluminum honeycomb ventilating board is to be made of the aluminum honeycomb in the aluminium frame.The honeycomb of waveguide type not only has electromagnet shield effect, and has high air circulation.The ventilation window that can be used for electronic equipment.
If the requirement to screening effectiveness and ventilation quantity is all higher, can use the cut-off waveguide ventilating board.This ventilating board is made of many hexagon cut-off waveguides, because the screening effectiveness of cut-off waveguide is higher, and the wall thickness of each waveguide is very thin, and therefore this ventilating board has good ventilation characteristic and electromagnetic shielding characteristic concurrently.When using the cut-off wave guide plate, to note equally and the cabinet matrix between overlap joint, general welding or the electromagnetic sealing liner of using connects.
The kind of cut-off wave guide plate:
The cut-off waveguide ventilating board has two kinds of aluminium foil and steel plates.Aluminium foil cut-off wave guide plate conducts electricity coating (chemical plating) on the aluminium foil cellular board makes, and does not make it stressed excessive in the use, and causes fracture.Steel plate cut-off wave guide plate is that the sheet metal by moulding is welded, and has higher screening effectiveness and intensity.
Generally speaking, the junction of different piece can not contact fully on the shield, can only be in some some contact, and this has constituted a hole array.The slit is the one of the main reasons that causes shield screening effectiveness degradation.The method that reduces slot leakage has:
1. increase the conduction contact point, reduce the width in slit, for example use the means (as processing contact surface) of machining to increase the evenness of contact-making surface, increase the density of securing member (screw, rivet) with milling machine;
2. strengthen two overlapping areas between the metallic plate;
3. use the electromagnetic sealing liner, the electromagnetic sealing liner is a kind of flexible electric conducting material.If the place installs continuous electromagnetic sealing liner in the slit, so, for electromagnetic wave, just as leak of liquid can not take place after having used the rubber seal liner on the lid of liquid container, electromagnetic leakage can not take place.
The processing of perforation cable:
Must adopt following two kinds of methods to handle for the cable that passes shield, the one, conductor shielding is got up, this is equivalent to shield is extended to wire termination.Another kind of measure is that lead is carried out Filtering Processing, the high frequency composition on the filtering lead.
Shielding processing: it is very strict that the cable shield that prevents radio frequency interference requires the termination of screen, some occasion, and for example the other end not have the occasion of shielding, and shielding does not almost have any effect.The general method of only when filtering can't be implemented, just using shielding.
Filtering Processing: low pass filter is installed, the effectively interference on the filtering cable, the integrality of maintenance shield on cableport.But prerequisite is that the signal frequency of transmitting on the cable differs far away with the interfering frequency that will protect.When adopting the method for filtering, the cut-off frequency of filter is very important, can not influence the transmission of normal signal.The installation method of filter is very big to the influence of effect simultaneously, will discuss specially in the back.
The special shielding measure of privileged sites:
(1) joint treatment:
At the seam crossing of shield, owing to the mating surface injustice, clean, welding quality is bad, have reason such as space between the trip bolt, gaps at seam crossing, causes the shield effectiveness of shield to reduce.Fixing seam is preferably adopted continuous welding.Before the welding, electron opaque material that should face of weld is removed clean.To overlap whole shell discontinuities as far as possible.Should adopt and compress conductive gasket to revocable seam, to improve the electromagnetic sealing effect of seam.Electroconductive gasket material commonly used has metal braid, contains rubber wiry etc.To the seam of activity, on doorframe, adopt the jerk-finger spring to improve the effectiveness of seam.
Modes such as the fixed form of conductive gasket has groove location, paste fixing and fin is fastening:
For the screening effectiveness that improves the slit can be taked following measure:
1) increases plate thickness, can realize by increasing next door length;
2) reduce the faying face gap width, can realize by improving faying face machining accuracy, welding or monoblock cast;
3) install conductive gasket additional, conductive liner commonly used is lined with braided metal net, soft metal, pectination reed, conductive rubber etc.;
4) be coated with electrically-conducting paint at seam crossing, electrically-conducting paint commonly used has conducting resinl, conduction fat etc.;
5) adjust the clench nail spacing, make it less than λ/20 (λ is the wavelength of electromagnetic field);
(2) eyelet shielding:
When ventilation, illumination etc. need,, should adopt the eyelet shielding for improving the effectiveness of equipment.Relating to parameters such as the size of the effect of eyelet shielding and electromagnetic frequency, eyelet and quantity.
(3) braid shielded:
Because of cable needs activity and crooked, the form of braid over braid is adopted in its shielding.The shield effectiveness of braid over braid increases with the increase of count, reduces with the increase of electromagnetic frequency.The non-magnetic metal wire knitted of screen of general cable can realize electric field shielding.Realize magnetic field shielding as need, the screen of cable should adopt the metal wire knitted of magnetic conduction.
(4) honeycomb plates shielding:
When the ventilation of equipment and shielding requirements are higher, adopt the honeycomb plates shielding that effect is preferably arranged.The honeycomb plates shielding is to utilize many hexagon metal tube formations welded together arranged side by side.Wherein each metal tube all plays the waveguide attenuator, and the ventilation pressure loss that ventilates is little.The effectiveness of honeycomb plates depends on the attenuation characteristic of waveguide, and is promptly relevant with the physical dimension of waveguide.
(5) panel hole shielding:
When equipment need be installed gauge outfit, data or graphic alphanumeric display, the reply panel hole was shielded, to guarantee the integrality of shielding.The better method of panel hole shielding is for to be provided with radome at the rear of gauge outfit or display.Radome is connected with metal decking by conductive gasket, and the turnover line by radome is provided with feedthrough capacitor.
(6) electric connector shielding:
The shielded electrical connector of selecting should have enough contact pins, and each screen connects at the electric connector head end in the current supply cable.Be to guarantee the integrality of shielding, be along one week of cable, the outer shielding layer of cable entirely is connected preferably welding with electric connector; The electric connector seat keeps good being electrically connected by the metal shell of conductive gasket and equipment; The electric connector head also should keep good being electrically connected with the electric connector seat.
(7) multilayer screen:
When the effect of single-layer shield does not reach when requiring, can adopt multilayer screen.Particularly to the shielding of frequency band broad, adopt the high different materials of conductivity and magnetic permeability to form multilayer screen respectively, can reach the shielding that high-frequency electric field and low frequency magnetic field is all had better effects.
The content that is not described in detail in this specification belongs to this area professional and technical personnel's known prior art.
Claims (6)
1, a kind of method for designing of protecting chamber shielding body, the method that is adopted is:
First step:, obtain the characteristic and the intensity of the interference source of transformer station according to a large amount of field measurements;
Second step: the equipment that part is installed in the protection cell carries out a series of immunity experiment;
Third step: the difference of the intensity of interference source in interference intensity that adopts in the comparative test and the transformer station, if self immunity to interference performance of secondary device can satisfy the condition in transformer station's high-voltage switch gear site safety work, then protect the special shielding measure of cell just can not consider; If self immunity to interference performance of secondary device can not satisfy the condition in transformer station's high-voltage switch gear site safety work, then protect the screening effectiveness of cell to design according to step 4;
The 4th step: the several key parts according to the protection cell provides clear and definite method for designing: it comprises the selection of shield screening effectiveness computational methods, shield material, the successional control of conduction of shield, the processing of perforation cable and the special shielding measure of privileged sites.
2, the method for designing of protection chamber shielding body as claimed in claim 1 is characterized in that: following rule is followed in the selection of shield material in the 4th step:
(1) conductivity of material and magnetic conductivity are good more, and screening effectiveness is high more, according to concrete shielding mainly rely on reflection loss, still absorption loss decides and stresses conductivity or magnetic conductivity;
When (2) frequency was lower, absorption loss was very little, and reflection loss is the dominant mechanism of screening effectiveness, improve reflection loss as far as possible;
(3) reflection loss is relevant with the characteristic of radiation source, and for the electric field radiation source, reflection loss is very big; For the magnetic field radiation source, reflection loss is very little, therefore, mainly relies on the absorption loss of material for the shielding in magnetic field radiation source, selects for use the higher material of magnetic permeability to do shielding material;
(4) reflection loss and shield are to the distance dependent of radiation source, and for the electric field radiation source, distance is near more, and then reflection loss is big more; For the magnetic field radiation source, distance is near more, and then reflection loss is more little; The correct character of judging radiation source determines that it should still away from shield, be an important content of structural design near shield;
When (5) frequency was higher, absorption loss was main shielding mechanism, was that electric field radiation source or magnetic field radiation source relation are little with radiation source at this moment;
(6) electric field wave is the easiest shielding, plane wave secondly, the magnetic field ripple is the most difficult shielding, especially the following low frequency magnetic field of 1KHz is difficult to shielding, for low frequency magnetic field, adopt high magnetic conductive material, even the material that adopts high conductivity material and high magnetic conductive material to combine.
3, the method for designing of protection chamber shielding body as claimed in claim 1; it is characterized in that: the successional control of the conduction of shield in the 4th step: when ventilation, printing opacity, Jia Shui, measurement etc. need; perforate on the cell will protected; for improving the effectiveness of equipment; adopt the eyelet shielding of woven wire, relating to parameters such as the size of the screening effectiveness of eyelet and electromagnetic frequency, eyelet and quantity.
4, the method for designing of protection chamber shielding body as claimed in claim 3 is characterized in that: eyelet is taked following measure:
(1) on the heavy caliber eyelet, covers woven wire, silk screen is contacted with shield well;
(2) change macropore into aperture;
(3) adopt cut-off wave guide plate ventilating opening;
(4) be coated with the shield glass of woven wire at the printing opacity mouth;
(5) on the hole that needs water, hermetic seal, fill up the woven wire that contains materials such as rubber.
5, the method for designing of protection chamber shielding body as claimed in claim 1, it is characterized in that: the processing of the 4th step middle punch cable: must adopt following two kinds of methods to handle for the cable that passes shield, the one, conductor shielding is got up, this is equivalent to shield is extended to wire termination; Another kind of measure is that lead is carried out Filtering Processing, the high frequency composition on the filtering lead.
6, the method for designing of protection chamber shielding body as claimed in claim 1 is characterized in that: the special shielding measure of privileged sites comprises in the 4th step:
(1) joint treatment;
(2) eyelet shielding;
(3) braid shielded;
(4) honeycomb plates shielding;
(5) panel hole shielding;
(6) electric connector shielding;
(7) multilayer screen.
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| CNA2009100606519A CN101478118A (en) | 2009-01-24 | 2009-01-24 | Design method for protecting chamber shielding body |
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| CN102608401A (en) * | 2012-03-06 | 2012-07-25 | 华北电力大学 | Measurement system and measurement method for disturbance voltage and disturbance current of GIS (gas insulated switchgear) secondary system |
| CN103118523A (en) * | 2013-01-18 | 2013-05-22 | 范茂荣 | Ship electromagnetic shielding cabin through piece |
| CN103453942A (en) * | 2013-09-13 | 2013-12-18 | 国家电网公司 | Method for measuring power frequency electric field intensity and magnetic field intensity which are in contact with operating worker in 500kV transformer substation |
| CN103683438A (en) * | 2014-01-06 | 2014-03-26 | 武汉大学 | Power adjustable wireless charging device applied in implantable cardiac pacemaker |
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| CN102608401A (en) * | 2012-03-06 | 2012-07-25 | 华北电力大学 | Measurement system and measurement method for disturbance voltage and disturbance current of GIS (gas insulated switchgear) secondary system |
| CN103118523A (en) * | 2013-01-18 | 2013-05-22 | 范茂荣 | Ship electromagnetic shielding cabin through piece |
| CN103453942A (en) * | 2013-09-13 | 2013-12-18 | 国家电网公司 | Method for measuring power frequency electric field intensity and magnetic field intensity which are in contact with operating worker in 500kV transformer substation |
| CN103453942B (en) * | 2013-09-13 | 2015-08-05 | 国家电网公司 | Measure the method for 500kV substation operation human contact power frequency electric field, magnetic field intensity |
| CN103683438A (en) * | 2014-01-06 | 2014-03-26 | 武汉大学 | Power adjustable wireless charging device applied in implantable cardiac pacemaker |
| CN103683438B (en) * | 2014-01-06 | 2016-03-30 | 武汉大学 | Be applied to the power adjustable formula wireless charging device of Implanted cardiac pacemaker |
| CN107135636B (en) * | 2017-05-12 | 2019-04-16 | 国网上海市电力公司 | A kind of square section metallic shield slot design method shielding ultra low yield point steel |
| CN107148206A (en) * | 2017-05-12 | 2017-09-08 | 国网上海市电力公司 | A kind of square-section metallic shield groove design method for shielding ultra low yield point steel |
| CN107135636A (en) * | 2017-05-12 | 2017-09-05 | 国网上海市电力公司 | A kind of square section metallic shield groove design method for shielding ultra low yield point steel |
| CN112005623A (en) * | 2018-06-06 | 2020-11-27 | 宝马股份公司 | Method for shielding a component |
| US11596089B2 (en) | 2018-06-06 | 2023-02-28 | Bayerische Motoren Werke Aktiengesellschaft | Method for shielding components |
| CN112005623B (en) * | 2018-06-06 | 2023-09-29 | 宝马股份公司 | Method for producing a vehicle chassis component |
| CN110505799A (en) * | 2019-09-27 | 2019-11-26 | 湖南华盾星通信息科技有限公司 | A kind of display with rotary shaft end Gap electromagnetic sealing structure |
| CN111707875A (en) * | 2020-05-08 | 2020-09-25 | 中石化石油工程技术服务有限公司 | Electric control pry shielding effectiveness testing device and method for gas gathering station field |
| CN113015421A (en) * | 2021-01-25 | 2021-06-22 | 国网浙江省电力有限公司金华供电公司 | Electromagnetic shielding device based on overhead line X-ray detection and verification method |
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| CN114726453B (en) * | 2022-06-09 | 2022-09-02 | 国网山东省电力公司潍坊供电公司 | Anti-interference wireless communication device and box-type substation |
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