WO1990001861A1 - Ameliorations relatives a la reduction de l'intensite de champs electromagnetiques - Google Patents

Ameliorations relatives a la reduction de l'intensite de champs electromagnetiques Download PDF

Info

Publication number
WO1990001861A1
WO1990001861A1 PCT/GB1989/000865 GB8900865W WO9001861A1 WO 1990001861 A1 WO1990001861 A1 WO 1990001861A1 GB 8900865 W GB8900865 W GB 8900865W WO 9001861 A1 WO9001861 A1 WO 9001861A1
Authority
WO
WIPO (PCT)
Prior art keywords
magnetic field
sensors
component
electro
strength
Prior art date
Application number
PCT/GB1989/000865
Other languages
English (en)
Inventor
Stephen John Elliott
Original Assignee
Adaptive Control Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Adaptive Control Limited filed Critical Adaptive Control Limited
Publication of WO1990001861A1 publication Critical patent/WO1990001861A1/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/42—Screening
    • G01R33/421—Screening of main or gradient magnetic field
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K9/00—Screening of apparatus or components against electric or magnetic fields

Definitions

  • This invention relates to reducing the strength of electro-magnetic fields and achieves such strength reduction either by reducing the strength of the magnetic components of the fields, or the electrical components thereof, or both.
  • the invention finds application in reducing alternating electro-magnetic field components in enclosed regions, being electro-magnetic field components created by or arising as a result of power lines in the neighbourhood of the region. It is a matter of fact that electro-magnetic field components cause interference with and are liable to damage certain categories of electronic equipment, and it has been suggested, with some supporting evidence, that such fields may constitute a health hazard.
  • a method of reducing the strength, within a region, of at least one component, (magnetic and/or electrical), of an electro-magnetic field comprises creating a second electro-magnetic field component which interferes with the said one electro-magnetic field component so as to reduce the strength thereof, by employment of second component generating means and a plurality of controlling sensors, the number of sensors being greater than the number of second component generating means.
  • apparatus for reducing the strength, within a region, of at least one component, (magnetic and/or electrical), of an electro-magnetic field component comprises means for creating a second, controlled, electro-magnetic field component which interferes with the said one electro-magnetic field component so as to reduce the strength thereof, characterised in that said means comprise a plurality of second component generating means and a plurality of controlling sensors, the number of sensors being greater than the number of second component generating means.
  • the generating means may comprise inductive winding means.
  • the generating means may comprise capacitor means.
  • Figure 1 is a diagram of a closed region, namely a room of a house, in relation to an electric power cable-carrying pylon,
  • Figure 2 is a representation of, inter alia, one set of inductive windings encompassing the region, so as to create an interfering, controlled, magnetic field component,
  • Figure 3 is a representation similar to that illustrated by Figure 2, with added features, and
  • Figure 4 is a representation similar to that illustrated by Figure 3, but is concerned with apparatus for creating an interfering, controlled, electrical field component.
  • a pylon a carries six power cables b 1 to b 6 respectively, which convey high alternating currents at line frequency.
  • the magnetic fields B 1 to B 6 (B 6 only being illustrated) are circumferentially distributed about their respective current-carrying conductors b 1 to b 6 , falling off inversely in magnitude with distance from the relevant cable.
  • the total magnetic field in a closed region C comprising a room in building 1, which is due to the power cables b 1 to b 6 , is the superposition of the instantaneous electro-magnetic fields due to each cable.
  • the resultant field is an alternating electro-magnetic field at the line frequency whose phase, magnitude and direction depends on the distances from the room C to each cable, and the magnitude and relative phase of the alternating current in each conducting cable.
  • the strength and spatial distribution of the electro-magnetic field in the room C may change with time, as a result of changes in the currents in each of the power lines due to supply demands.
  • the al ternati ng magnetic fi el d strength at thi s observati on poi nt i s given by the expression:
  • apparatus 2 is provided for reducing the strength of the magnetic component of the electromagnetic field within the closed region defined by the room C.
  • the apparatus 2 comprises means 3 for creating a destructive interfering alternating magnetic field component substantially equal and opposite to that created in the room C by the six power-carrying cables b 1 to b 6 , so as to at least reduce the strength of said field component.
  • the apparatus 2 comprises a plurality of inductive winding means and a plurality of magnetic field sensors.
  • the inductive winding means encompass the room C in each of three Cartesian axes X, Y, Z, each winding means being driven by an alternating electric current (provided by alternator 4) at the line frequency of variable amplitude and phase.
  • Figure 2 shows only one set of winding means, in the form of three coils, d 1 , d 2 , d 3 , and one set of magnetic field sensors in the form of "search" coils f 1 , f 2 , f 3 , f 4 .
  • the two sets illustrated by Figure 2 are associated with axis X only of the three Cartesian axes X, Y, Z.
  • the three windings d 1 , d 2 , d 3 are driven by alternating currents I cl , I c2 and I c3 respectively, derived by passing signals at the line frequency through electrical networks N 1 , N 2 and N 3 respectively by which the amplitude and phase of the said currents may be adjusted.
  • the arrangement may be simplified by arranging that the currents through each of the windings are identical, for example, by wiring them in series.
  • the windings d 1 , d 2 , d 3 are substantially equi-spaced from each other. If the spacing between the windings d 1 , d 2 , d 3 is approximately equal to their effective radius, a type of "Helmholtz coils" arrangement is created providing a sensibly constant magnetic field in the region defined by the room C.
  • the field sensors f 1 to f 4 are not disposed in a line as shown in Figure 3, but are well spaced out within the body of the room C in order to get the best effect.
  • Such distribution plus the fact that a greater number of sensors f 1 , f 2 , f 3 , f 4 is used than the number of control windings d 1 , d 2 , d 3 , results in substantially uniform magnetic field component cancellation over substantially the whole of the closed region defined by the room C.
  • the apparatus 2 is provided with an automatic control system which uses the magnetic field detectors f 1 , f 2 , f 3 , f 4 , which are disposed inside the room C, in order to monitor the total magnetic field therein, and to adjust the magnitude and phases of the currents in the windings d 1 , d 2 , d 3 so as to substantially reduce or even to minimise the sum of the squares of the outputs from the field sensors f 1 to f 4 .
  • the automatic control system is illustrated, again for control in the Cartesian axis X only, in Figure 3, which shows the control system 5 using a controller 6 for adjusting the three control winding currents I cl , I c2 and I c3 so as to substantially reduce and minimise, as far as possible, the sum of the squares of the voltage outputs V 1 to V 4, of the four field sensors f 1 to f 4 .
  • the field sensors f 1 , f 2 , f 3 , f 4 must also be oriented in a variety of directions to pick up the total magnetic field. It is straightforward, however, to provide a controller 6 which will account for any interaction between each inductive winding means and its associated field sensor in order to produce a single coupled control system rather than three independent control systems controlling the field in the three axes independently.
  • V I [V 1T V 2T . . . . .. V LT ] T
  • V P [V 1P V 2P . . . . . V Lp ] T
  • I C [ I c l I c 2 . . . . .. I cM ] T and the matrix:
  • V T V p + C I c
  • the control problem is to minimise the sum of the squared moduli of the total output voltages from the search coils f 1 to f 4 by adjusting each I cm .
  • This sum of squared output voltages may be written as V T H V T where H denotes the conjugate transpose of the vector , by adjusting each I cm . It can be shown that the result of the standard complex quadratic minimisation problem is a unique optimum set of control winding currents given by:
  • the control system can determine each of the elements of the matrix C, and with the current to each winding set to zero the elements of the vector V p can be determined.
  • the controller 6 is implemented on a data processor in the form of a microprocessor 7, using analogue to digital converters to link the field sensors f 1 , f 2 , f 3 , f 4 with the microprocessor and to measure each field sensor voltage, V 1 to V 4 and digital to analogue converters to link the microprocessor with the windings d 1 , d 2 , do and control each control winding current, I cm .
  • the microprocessor 7 may readily be programmed to seek to minimise the value of a cost function according to a control algorithm relating to the minimisation of the sum of the squares of the outputs from the magnetic field sensors (f 1 , f 2 , f 3 , f 4 ) and, hence, of the magnetic field component of the electro-magnetic field.
  • a number of methods may be used to make the controller 6 responsive to changes in the external magnetic field component.
  • An adaptive method of control applicable to the present invention is disclosed by PCT Application published as W088/02912.
  • the present invention could adopt the digital control system disclosed by W088/02912, to provide a system 8 whereby the interfering magnetic field component is adaptively adjusted in an automatic manner using adaptive digital filters.
  • a reference signal 9 derived from the mains supply, eg from one of cables b 1 to b 6 is employed by the control system 8, preferably stepped down by a transformer.
  • means may be provided for creating a second, controlled electrical field component which destructively interferes with the electrical component of the electro-magnetic field to that created by the cables b 1 to b 6 of Figure 1.
  • Such means are illustrated by Figure 4, wherein the interfering electrical field component is created by apparatus 20.
  • the apparatus 20 comprises a plurality of capacitor means 21 and a plurality of electrical field sensors ef 1 , ef 2 , ef 3 , ef 4 .
  • the capacitor means 21 comprise insulated capacitor plates 22, 23, shown by the shaded areas of the Figure, oppositely disposed at the end surfaces of the room C, on Cartesian axis X. Identical electrode plates are disposed on the floor and roof surfaces of the room C (on axis Z), and on the opposite side surfaces thereof (on axis Y), to form two further capacitor means 21.
  • the voltage generator means 24 is operable to develop in the capacitor means 21 voltages variable in amplitude and phase
  • the controller 26 is responsive to the outputs of the electrical field sensors ef 1 , ef 2 , ef 3 , ef 4 (by way of V cl ) in order to vary the magnitudes and phases of the voltages developed at the capacitor means 21, so as to substantially reduce (and preferably minimise) the sum of the square of the outputs from the field sensors ef 1 , ef 2 , ef 3 , ef 4 .

Landscapes

  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Epidemiology (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Measuring Magnetic Variables (AREA)

Abstract

Un appareil (2) (voir fig. 3) pour réduire l'intensité, dans un espace C, du composant magnétique d'un champ électromagnétique, comprend un moyen pour créer un second composant de champ magnétique commandé, qui perturbe le premier composant de champ magnétique mentionné, de manière à en réduire l'intensité. Le moyen (2) comprend une pluralité d'enroulements d'induction (d1, d2, d3) ainsi qu'une pluralité de capteurs (f1, f2, f3, f4) de champs magnétiques de commande, le nombre de capteurs (f1, f2, f3, f4) étant supérieur au nombre d'enroulements (d1, d2, d3). Les enroulements (d1, d2, d3) entourent l'espace C autour de trois axes de coordonnées cartésiennes (X, Y, Z). On a prévu un appareil similaire (20) (voir fig. 4) pour réduire l'intensité du composant électrique du champ électromagnétique dans lequel les enroulements (d1, d2, d3) sont notamment remplacés par des plaques à condensateur de grande surface.
PCT/GB1989/000865 1988-07-29 1989-07-28 Ameliorations relatives a la reduction de l'intensite de champs electromagnetiques WO1990001861A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB888818087A GB8818087D0 (en) 1988-07-29 1988-07-29 Improvements in/relating to attenuation of electro-magnetic field components
GB8818087.2 1988-07-29

Publications (1)

Publication Number Publication Date
WO1990001861A1 true WO1990001861A1 (fr) 1990-02-22

Family

ID=10641317

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1989/000865 WO1990001861A1 (fr) 1988-07-29 1989-07-28 Ameliorations relatives a la reduction de l'intensite de champs electromagnetiques

Country Status (4)

Country Link
EP (1) EP0426746A1 (fr)
AU (1) AU4043489A (fr)
GB (1) GB8818087D0 (fr)
WO (1) WO1990001861A1 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0396381A2 (fr) * 1989-05-01 1990-11-07 Conrac Scd, Inc. Méthode et dispositif pour la neutralisation dynamique de champ magnétique
EP0569197A2 (fr) * 1992-05-06 1993-11-10 International Business Machines Corporation Appareil électrique avec émissions réduites de champ électrique
WO1994026084A1 (fr) * 1993-04-28 1994-11-10 Asea Brown Boveri Ab Procede et dispositif servant a amortir activement des champs magnetiques de frequence industrielle
EP0651420A1 (fr) * 1993-10-30 1995-05-03 International Business Machines Corporation Dispositif de réduction de l'émission de champ électrique
WO1997001948A1 (fr) * 1995-06-27 1997-01-16 Ab Volvo Dispositif et procede de reduction des champs magnetiques, et utilisation
FR2757342A1 (fr) * 1996-12-13 1998-06-19 Nec Corp Dispositif de blindage contre des particules chargees
EP0880311A1 (fr) * 1996-10-04 1998-11-25 Matsushita Electric Industrial Co., Ltd. Dispositif de protection contre les champs electromagnetiques
WO2001045481A1 (fr) * 1999-12-13 2001-06-21 Valtion Teknillinen Tutkimuskeskus Procede d'attenuation d'interference dans une chambre a protection magnetique
GB2606589A (en) * 2021-05-14 2022-11-16 Magnetic Shields Ltd A magnetic shield

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2146071A1 (de) * 1971-09-15 1973-03-22 Foerster Inst Dr Friedrich Anordnung zum erzielen eines von magnetischen stoerfeldern freien raumes
EP0164199A1 (fr) * 1984-04-19 1985-12-11 Technicare Corporation Appareil pour la suppression d'un champ rotationnel pour un appareil à résonance magnétique nucléaire
WO1988002912A1 (fr) * 1986-10-07 1988-04-21 Adaptive Control Limited Limitation active des vibrations

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2146071A1 (de) * 1971-09-15 1973-03-22 Foerster Inst Dr Friedrich Anordnung zum erzielen eines von magnetischen stoerfeldern freien raumes
EP0164199A1 (fr) * 1984-04-19 1985-12-11 Technicare Corporation Appareil pour la suppression d'un champ rotationnel pour un appareil à résonance magnétique nucléaire
WO1988002912A1 (fr) * 1986-10-07 1988-04-21 Adaptive Control Limited Limitation active des vibrations

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0396381A3 (fr) * 1989-05-01 1992-11-04 Conrac Scd, Inc. Méthode et dispositif pour la neutralisation dynamique de champ magnétique
EP0396381A2 (fr) * 1989-05-01 1990-11-07 Conrac Scd, Inc. Méthode et dispositif pour la neutralisation dynamique de champ magnétique
EP0569197A2 (fr) * 1992-05-06 1993-11-10 International Business Machines Corporation Appareil électrique avec émissions réduites de champ électrique
EP0569197A3 (fr) * 1992-05-06 1994-01-12 Ibm
US5506455A (en) * 1992-05-06 1996-04-09 International Business Machines Corporation Electrical appliance with reduced electric field emissions
WO1994026084A1 (fr) * 1993-04-28 1994-11-10 Asea Brown Boveri Ab Procede et dispositif servant a amortir activement des champs magnetiques de frequence industrielle
EP0651420A1 (fr) * 1993-10-30 1995-05-03 International Business Machines Corporation Dispositif de réduction de l'émission de champ électrique
US5986355A (en) * 1995-06-27 1999-11-16 Ab Volvo Arrangement and method for reduction of magnetic fields and use thereof
WO1997001948A1 (fr) * 1995-06-27 1997-01-16 Ab Volvo Dispositif et procede de reduction des champs magnetiques, et utilisation
US6249006B1 (en) 1996-10-04 2001-06-19 Matsushita Electric Industrial Co., Ltd. Electromagnetic field shielding device
EP0880311A1 (fr) * 1996-10-04 1998-11-25 Matsushita Electric Industrial Co., Ltd. Dispositif de protection contre les champs electromagnetiques
EP0880311A4 (fr) * 1996-10-04 2000-08-09 Matsushita Electric Ind Co Ltd Dispositif de protection contre les champs electromagnetiques
FR2757342A1 (fr) * 1996-12-13 1998-06-19 Nec Corp Dispositif de blindage contre des particules chargees
WO2001045481A1 (fr) * 1999-12-13 2001-06-21 Valtion Teknillinen Tutkimuskeskus Procede d'attenuation d'interference dans une chambre a protection magnetique
US6734353B2 (en) 1999-12-13 2004-05-11 Valtion Teknillinen Tutkimuskeskus Method for attenuating interference in a magnetically shielded room
GB2606589A (en) * 2021-05-14 2022-11-16 Magnetic Shields Ltd A magnetic shield

Also Published As

Publication number Publication date
AU4043489A (en) 1990-03-05
EP0426746A1 (fr) 1991-05-15
GB8818087D0 (en) 1988-09-01

Similar Documents

Publication Publication Date Title
ES2234794T3 (es) Compensacion de la caida de tension del cable en un sistema de alimentacion de energia electrica.
Dawalibi et al. Integrated analysis software for grounding, EMF, and EMI
US5616969A (en) Power distribution system having substantially zero electromagnetic field radiation
US5536978A (en) Net current control device
SE515388C2 (sv) Anordning för avkänning av elektriska urladdningar i ett provobjekt
US5068543A (en) Low hazard extremely low frequency power transmission line
WO1990001861A1 (fr) Ameliorations relatives a la reduction de l'intensite de champs electromagnetiques
Olsen et al. Development and validation of software for predicting ELF magnetic fields near power lines
Canova et al. A proposal for performance evaluation of low frequency shielding efficiency
Kuznetsov et al. Modeling and active shielding of magnetic field in residential buildings located near group of high voltage power lines
CZ284713B6 (cs) Zařízení pro kompenzaci střídavého napětí objevujícího se mezi prostředím a kovovým potrubím, uloženým v prostředí
Rozov et al. Analytical calculation of magnetic field shielding factor for cable line with two-point bonded shields
CA2021712A1 (fr) Transformateur de courant optique
Yamaguchi et al. Magnetic field and electromagnetic force analysis of 3-phase air-core superconducting power transformer
KR100882293B1 (ko) 수직루프를 이용한 송전선로 전자계 저감 실증시험 시스템
Kuznetsov et al. Overhead power lines magnetic field reducing in multi-story building by active shielding means
Ismail Effect of tower displacement of parallel transmission lines on the magnetic field distribution
Chung et al. Effect of eddy current in the laminations on the magnet field
Kuznetsov et al. Surrogate synthesis of system of active shielding of magnetic field generated by group of overhead power lines
WO1994026084A1 (fr) Procede et dispositif servant a amortir activement des champs magnetiques de frequence industrielle
Kuznetsov et al. Development and investigation of layout of active screening system of the magnetic field generated by group of overhead transmission lines
Kuznetsov et al. Synthes of robust active shielding systems of magnetic field generated by group of high-voltage power lines
Kuznetsov et al. Feed Forward Robust Active Shielding System by Magnetic Field with Single Compensating Coil
Habiballah et al. ELF electric and magnetic fields exposure assessment of live-line workers for 132 kv transmission line of SEC
Kasas-Lazetic et al. Calculation of Electromagnetic Field Produced by Mixed Overhead Power Lines

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AU GB JP US

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE FR GB IT LU NL SE

WWE Wipo information: entry into national phase

Ref document number: 1989909016

Country of ref document: EP

WWP Wipo information: published in national office

Ref document number: 1989909016

Country of ref document: EP

WWW Wipo information: withdrawn in national office

Ref document number: 1989909016

Country of ref document: EP