Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
  • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
  • G01R15/16—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using capacitive devices

Definitions

• the present invention relates to a.capacitive sensor for sensing variations in an electric field.
• the invention also relates to a measuring device including such a sensor for measuring voltage at a distance from high-voltage conductors, and to a method for such measurement.
• the other quantities which are detected by the measuring device are transients and ionic discharge.
• the measuring device is particularly adapted to measure voltage in electric power networks, which may comprise one or more phases, for control of transmission or distribution of electric power, or as a basis for debiting of consumed energy.
• the device comprises essentially an electrode, fixed to ground potential, in the form of a cylindrical box with, for example, six sector- shaped openings on the upper side thereof, and a rotating electrode inside the box but electrically insulated from the same.
• the rotating electrode comprises six identical lobes formed as a Bernoulli lemniseate, arranged uniformly around a circle.
• the device may be used either at the same level as ground-level by placing it in a hole dug in the ground, covered with a metal-protective plate with an opening for the device. The device may also be placed so as to project above the ground.
• the above-mentioned article also shows a device for measurement above ground level of the electric field under a high-voltage conductor.
• the device comprises two metal cylinders, each being divided lengthwise into two halves insulated from each other.
• the cylinders have equal or different radii, but different lengths.
• the cylinders rotate at different speeds and from a mechanical point of view it is desirable that the cylinders rotate in directions opposite to each other.
• One problem with the devices described above is that both are sensitive to disturbing electric fields, which therefore may greatly distort the measurement result. Another problem is that both have a relatively complicated design.
• the apparatus is shown in three different embodiments, its basic design comprising two hemispherical electrodes, between which a device for measuring and generating measured data is enclosed.
• the measuring electrodes are in the form of two circular metal plates, whereby the associated measurement electronics is arranged between the plates and thus at least partly screened thereby.
• the measuring electrodes are in the form of two semi- cylindrical electrodes, insulated from each other, where the electronics, in the same way as above, is located between the electrodes.
• the known device for measuring electric fields in case of a stroke of lightning has a certain directional sensitivity because of its two uniform plates However, it is not capable of screening undesired electric fields and i ⁇ therefore not useful in the application sought, where the electric field generated by only one of several high-voltage parts is to be measured.
• the object of the present invention is to achieve a measuring device, by which may be measured the voltage in a high-voltage part in an electric power system, which high-voltage part is selected from a plurality of such parts and is located at a distance.
• the measuring device shall have a simple design, be flexible and have a low production cost.
• the measuring device shall be capable of screening undesired electric fields and be capable of being directed, in a simple manner, towards a high-voltage part for measuring the magnitude and the frequency spectrum of the voltage therein.
• the measuring device shall also detect the presence of transients or ionic discharge of a high-voltage part.
• a measuring device comprising a sensor which detects changes in a directed part of an electric field and a signal converter, which sensor and measuring device, respectively, exhibit the characteristic features described in the independent claims.
• the invention also relates to a method of measuring the voltage in a high-voltage part, selected from a plurality of such parts and located at a distance, in an electric power system.
• a high-voltage conductor is surrounded by an electric field which carries information about the potential of the conductor, its variation and its frequency contents.
• a capacitive sensor comprising two mirror-symmetrical electrodes which are introduced into this electric field may sense these quantities.
• One problem, however, is that such a capacitive sensor is sensitive to changes in all directions of the electric field. Thus, also other field- generating objects may influence and sometimes completely dominate such a measurement. It is, therefore, not possible to distinguish from the measurement result which change belongs to the component selected for the measurement. Since distribution of electric power is normally carried out in three adjacently extending conductors, it is thus not possible with such a sensor to delimit the field which emanates from one of the conductors .
• the invention relates to a capacitive sensor with two electrodes, adapted for sensing changes in a directed part of an electric field.
• This sensor is also adapted, in such an electric field, to detect transients and ionic discharge from a high-voltage apparatus.
• a directed part of an electric field is sensed by screening the other electrode from undesired electric fields by means of an electrode connected to ground or to some other controllable potential.
• a sensor intended for this purpose is arranged with one electrode predominantly surrounding the other electrode and connected to ground or to some other controllable potential.
• an opening is arranged, through which a directed partial amount of the electric field reaches the surrounded electrode, which hereinafter will be referred to as an inner electrode. All other directed sub-quantities of the electric field are efficiently prevented by the screen electrode .
• the electrodes are insulated from each other by a gaseous dielectric, the capacitance formed by the electrodes thus, becoming insensitive to temperature variations.
• the sensor may be configured and its capacitance be measured in a laboratory and then be used in other environments without needing calibration again.
• the sensor may also be used for a long period of time at varying temperatures, in which case no correction has to be made.
• the inner electrode may be divided into sub- electrodes which are insulated with each other and which may be placed both in the lateral and vertical directions.
• the invention relates to a measuring device, including the sensor described above, for voltage measurement at insulation distance of a high- voltage part in an electric field with a plurality of field-generating components.
• the measuring device is arranged by connecting a signal converter to the sensor, whereby, when the screen electrode is connected to ground, a measuring device is obtained by means of which a directional sub-quantity of an electric field may be measured.
• This measuring device constitutes a simple, inexpensive and reliable device for measuring, in a contactless manner, an alternating voltage at a distance from a high-voltage conductor.
• the device is a broad-band device which, within a large frequency range, permits measurement in a simple manner also of the occurrence and magnitude of harmonic components of the object intended to be measured.
• the signal converter includes members for impedance conversion, amplification, and may also include members for filtering and digital conversion, of the measurement signal.
• the signal converter is placed at a short distance from the actual sensor, and in a preferred embodiment of the invention it is integrated with the sensor.
• the converted, analog or digital, signal may thereafter be transmitted to an analyzer via an electric or optical medium or be transmitted in a contactless manner via a transmitter and a receiver.
• the screen electrode When applying the measuring device to voltage measurement, the screen electrode may be connected to a controllable potential instead of to ground, in which case, by phase- locking to one of the phases, greater dynamics and higher resolution of the measurement may be obtained.
• the inner electrode is instead connected to a phase lock circuit, in which case the contribution from an unwanted field-generating source may be suppressed.
• the signal converter is thus brought to include also a conductor adapted for signals in the opposite direction.
• the signal converter when using filtering of the sensed signal, the signal converter may include a plurality of conductors for transmission of different filtered signals to a multi-channel analyzer.
• the measuring device has a wide field of use, especially in connection with measurement of alternating voltage in high-voltage equipment.
• One such field of use is enclosed or non-enclosed ⁇ witchgear in electric power-related distribution systems.
• the device is placed in an enclosed switchgear unit at insulation distance from each busbar, belonging to the respective phase, for measurement of alternating voltage.
• the measuring devices may be placed at a common point and be individually directed towards a respective busbar in the switchgear.
• the measuring method is sensitive to variations in the distance between a measuring object and the measuring device. However, this is usually no problem since such variations, viewed over a longer period of time, tend to become negligible . It is advantageous to place the measuring device in locations where the position of the measuring object is fixed, for example at points of attachment or suspension where the variation in distance is minimal.
• the accuracy is increased in a simple manner by placing a plurality of measuring devices around the conductor.
• the accuracy of the voltage measurement is increased by placing four measuring devices rotationally- symmetrically around an extended part of the conductor.
• the correct value of the voltage is obtained from the mean value of the four measuring devices .
• the sensitivity to variations in the distance between the measuring object and the measuring device may be utilized for detecting movement of the measuring object.
• By placing at least three measuring devices in fixed positions around a high-voltage conductor it may be detected if the conductor is moved and in which direction this movement takes place.
• a method for obtaining a stable measurement distance to a high-voltage part is achieved by arranging the measuring device and the measuring object at either end of an insulator, which may be hollow. In this way, the length of the insulator is utilized to constitute a non-varying measurement distance.
• the measuring device may be placed both outside and inside the insulator body.
• suspension insulators especially in transmission towers, and support insulators.
• An additional preferred use of the measuring device is measurement . of direct voltage in a high-voltage apparatus. This is made possible by creating, in the incident rectified electric field entering through the opening in the screen electrode, a known variation which may be detected in a simple manner. Such a variation of the incident electric field is achieved by covering the opening in the screen electrode with a stable frequency by a conducting screen connected to ground. This can be performed in the simplest manner by applying a plate or a plurality of plates to a rotating shaft connected to ground. Through this rhythmic screening of the opening of the surrounding electrode, a varying electric field is created, from which the magnitude of a directed part of the direct voltage of a high-voltage part can be measured. Another way of achieving a varying field from which the sought magnitude can be measured is to arrange the inner electrode to oscillate with a known frequency.
• a measuring device is also especially suited, in connection with distribution networks, to allow to control relay protection functionalities, in which case the device, by its low investment cost, may concentrate the measuring points and hence increase the selectivity.
• the measuring device is also especially suited for measuring voltage in a conductor in connection with debiting of energy consumption. For this purpose, the measurement is to be combined with a diffe- rently measured current through the conductor, whereby the electric energy which passes may be determined,
• Figure 1 shows a view, partly in section, of a measuring device including a capacitive sensor and a signal converter for directed voltage measurement according to the invention
• Figure 2 shows a view, partly in section, of an alternative embodiment of the measuring device
• Figure 3 shows a calculated .distribution of an electric field penetrating through the opening of the screen electrode
• Figure 4 shows a view, partly in section, of an insulator with a measuring device according to the invention applied thereto;
• Figure 5 shows an explanatory sketch of an enclosed switchgear unit with three busbars with a measuring device according to the invention associated with each of the busbars;
• Figure 6 shows an explanatory sketch of a transmission tower for transmission of three-phase alternating current, on which a measuring device according to the invention is mounted for voltage measurement;
• Figure 7 shows an explanatory sketch of an enclosed switchgear unit for a phase with a measuring device according to the invention
• Figure 8 shows an explanatory sketch of an enclosed switchgear unit for a phase with four measuring devices according to the invention
• Figure 9 shows a view, partly in section, of a preferred embodiment of a measuring device with the inner electrode divided into sub-electrodes insulated from one another;
• Figure 10 shows a view, partly in section, of a preferred embodiment of the measuring device, which for measurement of direct voltage comprises a rotating wing which rhythmically covers the opening in the screen electrode.
• FIG. 1 shows a measuring device 10 for directed voltage measurement according to the present invention.
• the measuring device 10 is intended to measure alternating voltage at insulation distance from a conductor 22.
• the measuring device 10 comprises a capacitive sensor 11 and a signal converter 13.
• the capacitive sensor has an inner electrode 12 and a screen electrode 14 which surrounds the inner electrode.
• the screen electrode is provided with an opening 16 intended, during measurement, to be directed towards the conductor 22.
• the two electrodes are made from a conducting material.
• the electrodes may be made as bodies of an arbitrary material as long s their limiting surfaces are conducting.
• an electrode may be made of a non-conducting material but with a surrounding conducting layer, for example a body of plastic, on which is applied a conducting coating.
• the screen electrode has the shape of a bucket, that is, it has a bottom from which extends a cylindrical or slightly conical border.
• the inner electrode has a plane extent in a plane parallel to the opening of the screen electrode.
• the inner electrode is insulated from the screen electrode and adjustably fixed thereto such that the distance between the inner electrode 12 and the opening 16 of the screen electrode 14 may be adjusted, as indicated by arrow A in Figure 1. In the example, this is made possible by means of an insulating tube 17 which extends through the screen electrode and to which the inner electrode 12 is fixed.
• the signal converter 13 is placed near the screen electrode 14 and comprises members for impedance conversion as well as amplification.
• the signal converter may comprise also members for filtering and digital conversion of the analog signal from, the sensor 11.
• the signal is adapted to condition the signal from the sensor, which is very disturbance-prone, into an analog signal or a digital pulse train adapted for transmission of the measured information.
• the signal converter is provided with a screen connected to ground or, as in the example, enclosed in a space 21 surrounded by a screen 19.
• the sensor 11 and the signal converter 13 are interconnected by means of a conductor IB, which may be screened, running in the tube 17.
• the signal converter is connected to an analyzer 15, which may be located at a distance from the measuring device 10.
• the transmission of the signal may be arranged both electrically and optically, but also in a contactless manner via a transmitter and a receiver.
• the capacitive sensor 11 is capable of sensing the electric field with a large bandwidth with respect to frequency, usually between zero and several thousand Hertz. It is, therefore, advantageous to arrange a broad-band signal converter 13 to the measuring device.
• the members for impedance conversion and amplification comprised in the signal converter are thus preferably arranged by a so-called video amplifier.
• a plurality of filters with different filter characteristics may also be arranged in the signal converter. Such filters may be bandpass filters or low- or high-pass filters. During measurement, these may each deliver a signal, or be sequentially connected.
• the signal converter 13 may therefore comprise a phase lock circuit (not shown) connected to the screen electrode 14.
• This circuit a so-called PL circuit (Pulse Locked Loop) , makes it possible, for example in a three- phase system, to lock the screen electrode 14 of the measuring device 10 to a potential which varies with the phase intended to be measured. In this way, the effect from the other phases may be suppressed in the output signal from the signal converter 13, which results in increased measurement accuracy.
• the measuring device 10 D uring measurement with the measuring device 10 for measuring alternating voltage at insulation distance from a high-voltage conductor 22, the measuring device 10 is directed towards the conductor 22.
• the desired part of the field must be able to fall through the opening in the screen electrode.
• a conceived axis which passes through the centre of the inner electrode and through the mid-point of the opening is directed towards the measuring object.
• the measuring device 10 is cali- brated in situ. The calibration is carried out by applying a known voltage, whereupon measurement with the measuring device is performed. The measuring device is thus calibrated by adjusting the measured value to correspond to the known voltage. When this has been completed, the actual easure- ent may be started.
• the measuring device 10 need not be brought into galvanic contact, or even in contact with the conduc- tor, the voltage of which is to be measured.
• the measurement may instead be performed at insulation distance from the conductor 22, which means that the measuring device is semi- protected for all those who get into concact therewith. This also implies that no installations need be made in the immediate vicinity of the conductor, and therefore no operational disturbances need be caused by the measuring method.
• the measuring device has an exceedingly simple design and is therefore very inexpensive to manufacture and is also reliable.
• the measuring device may be advantageously arranged to constitute a detector, a so-called PD (Partial Discharge) detector, for transients and ionic discharge, of a measuring object. Because of its reliability, its broad-band design and slight investment cost, the measuring device is exceedingly well suited in connection with energy measurement for debiting of consumed electric energy and when functioning as relay protection.
• PD Partial Discharge
• FIG. 2 shows an alternative embodiment of the measuring device 10 according to the invention.
• the measuring device comprises a sensor 11 and a signal converter 13.
• a screen electrode 14 surrounds an inner electrode 12, only leaving an opening 16 which, during measurement, is directed towards a measuring object.
• the screen electrode is globular whereas the inner electrode is cup-shaped with the concave side facing the opening.
• the screen electrode may, however, have an arbitrary shape and be formed of an arbitrary, dense or perforated, conducting material.
• the inner electrode may have an arbitrary shape. It is preferable, however, to arrange the inner electrode with a plane extent which is substantially parallel to the plane of the opening.
• the sensor 11 is not limited, as indicted in the examples, to exhibit a circular shape.
• FIG. 3 shows a calculation of the distribution of an electric field penetrating through the opening of a ground- connected screen electrode into an inner electrode 12.
• the figure shows only part of such a field in the vicinity of the edge of the inner electrode, which is cup-shaped in the figure.
• the calculation which has been verified by experiments, shows that that part of the electric field which penetrates through the opening initially has a direction parallel to the normal to the opening. Further inside the screen electrode, the field lines diverge out towards the inside of the screen electrode and are finally absorbed by the inner electrode 12.
• the inner electrode 12 has its concave surface directed towards the opening in the screen electrode.
• the advantage of this geometry is that the field distribution inside the screen electrode becomes more uniform.
• the design of the cup-shaped inner electrode 12 as a spherically curved plate causes all the field lines to become incident perpendicularly to the plate. This provides additional advantages with a stronger output signal from the sensor while at the same time its screening properties are maintained.
• FIG. 4 shows an advantageous use of a measuring device 10 according to the invention.
• the measuring device is applied at the end of a hollow insulator 25.
• the insulator comprises an insulant 26 of porcelain or other insulating material, as well a ⁇ a first pole 27 and a second pole 28.
• the first pole is connected to a high- voltage apparatus (not shown) whereas the second pole is connected to ground.
• the measuring device is applied to the second pole 28 with its screen electrode 14 connected to the pole and with its inner electrode 12 insulated and adjustably fixed to the screen electrode 14.
• the two poles may be provided with screens (not shown) in the form of plates of conducting material, extended in the transverse direction of the insulator, which are connected to the respective pole.
• screens in the form of plates of conducting material, extended in the transverse direction of the insulator, which are connected to the respective pole.
• the smaller insulation distance on the inside of the insulator, which is caused by the gas may be utilized such that the measuring device 10 in its entirety is housed inside the insulator.
• An insulator including a device for voltage measurement may thus be manufactured in a simple manner as a finished product.
• FIG. 5 shows an explanatory sketch of a switchear unit with busbars , S, and T for three-phase alternating voltage surrounded by an enclosure 29.
• a measuring device 10,, 10 E , 10, intended for each one of the busbars, for directed voltage measurement according to the invention.
• the three measuring devices have been brought together into a common position to achieve a simple installation and wiring, respectively, and each measuring device is directed towards its respective busbar.
• each measuring device may be placed at insulation distance in an arbitrary position within the switchgear.
• the common location is an advantage since the greatest possible angle between the sensitivity directions of the measuring devices may then be achieved. With this type of use of the measuring device, among other things, mounting time and space in the enclosure are saved.
• the transmission tower comprises a framework beam 31 supported by two framework columns 30 ⁇ , 30 b and three suspension insulators 32 ⁇ , 32 9 , 32 ⁇ , which are arranged in the framework beam and each of which supports a high-voltage conductor 22., 22. , 22 ⁇ .
• An enlarged picture shows, in two side views, how a measuring device 10 ⁇ is applied to the framework beam 31 close to the suspension insulator 32 ⁇ , which supports the high-voltage line 22 grant.
• the positioning of the measuring device at such a suspension point for the line implies that the measurement distance becomes defined and not significantly changed when the line moves caused by wind or any other force.
• the measuring device may advantageously be integrated also with the insulator, as shown in Figure 4.
• the converted signal delivered from the measuring device may be transmitted to an analyzer both electrically, optically and in a wireless manner with the aid of telephony.
• the transmission or distribution may be checked in an advantageous manner.
• FIG. 7 An explanatory sketch of a switchgear unit with only one phase surrounded by an enclosure 29 is shown in Figure 7.
• a measuring device 10 according to the invention for measuring the alternating voltage from one single busbar 33 may here, in the same way as in the example in Figure 5, be arranged at insulation distance in an arbitrary position within the enclosure.
• One advantage with this application is that no other electric fields are generated in the enclosure, which permits the positioning of the measuring device to be con- trolled for other reasons.
• a use of a measuring device according to the invention in enclosed switchgear with one phase only constitutes an exceedingly simple and cost-saving installation.
• a voltage measurement with a measuring device is sensitive to variations in the distance between the measuring device and the measuring object. This fact may be utilized for the purpose of studying a movement of a measuring object.
• a method for measuring voltage from a measuring object moving stochastically around a mid-point may thus be achieved in a simple manner.
• a measurement arrangement which permits, on the one hand, a method for studying the movement of a conductor and, on the other hand, a method for increasing measurement accuracy is shown in Figure 8.
• Figure 8 shows an explanatory sketch of switchgear with one phase only, surrounded by an enclosure 29.
• measuring devices 10a, 10b, 10c, lOd are each arranged in a corner of a cross section of the switchgear.
• the converted signal from each one of the measuring devices is preferably analyzed by a four-channel analyzer (not shown) . To study the movement, the signals are compared, and to increase the measurement accuracy, the average value of the signals are formed.
• the position of the busbar is determined, whereby a measurement of the voltage is corrected for the change in position such that a correct measurement value may be arrived at by calculation.
• the method may also be used for detecting and correcting the measurement for changes in the electric background field, which provides unsymmetrical changes in the measured signals.
• a greater measurement accuracy is obtained by introducing a plurality of measuring devices which carry out measurement on the same object.
• the measuring methods described are not limited to be applied to enclosed switchgear only, but may also be applied to free conductors and to non-enclosed switchgear. In non-enclosed switchgear, it is particularly valuable to be able to correct the measurement value for changes in the background field.
• the sensor 11 comprises a screen electrode 14 which is provided with an opening 16 and which surrounds a first inner sub-electrode 12a and a second inner sub- electrode 12b. which are insulated from each other and which are each adjustably fixed to the screen electrode.
• the opening 16 is limited by a ring 34 of a conducting material, connected to the screen electrode, the task of which is to equalize the electric field so as to prevent corona.
• the inner sub- electrodes are equally large and preferably have the shape of half a round plate, such that the sub-electrodes together exhibit the shape of a full round plate.
• the inner sub- electrodes are each connected to a respective signal converter (not shown) , and, in the same way as in example 1, the measurement signals are each transmitted to a respective analyzer, or to a common multi-channel analyzer.
• the inner electrode By dividing the inner electrode into sub-electrodes, the above-mentioned sensitivity to distance dependence may be further utilized.
• the electrodes are preferably adjusted to exhibit the, same capacitance, whereby, by means of a bridge circuit, a comparison between the converted signals from each one of the sub-electrodes may determine, on the one hand, whether by measuring object is in front of the sensor and, on the other hand, whether the measuring object moves during the measurement.
• An electric field generated from another unwanted object is detected by dividing the inner electrode by comparisons of the measurements in an analyzer and may thus be eliminated from the measurement result.
• the inner electrode is divided into an arbitrary number of sub-electrodes.
• the inner electrode is formed into a plurality of uniform sectors of a circle.
• FIG. 10 An additional alternative embodiment of a measuring device according to the invention is shown in Figure 10.
• a measuring device 10 includes a sensor 11 and a signal converter 13.
• the sensor comprises an inner electrode 12 and a screen electrode 14 surrounding the inner electrode and provided with an opening 16.
• the inner electrode is fixed to an insulating tube 17, which is adjustably fixed to the screen electrode, such that the inner electrode 12 may change in a direction designated A.
• the inner electrode is connected to the signal converter 13 by means of a conductor 18 drawn through the tube 17, the signal converter being arranged in a space 21 surrounded by a screen 19.
• a shaft 36 which is rotated by a drive means (not shown), is rotatably fixed to the measuring device, and on this shaft 36 a disc 35, which is parallel to the opening 16, is fixed.
• the shaft 36 and the disc 35 are connected to the same potential as the screen electrode 14.
• the disc 35 which extends, for example, along a semi-circle, will screen the opening with a known frequency.
• a directed part will in this way, with variation between zero and full field strength, penetrate through the opening in the screen electrode. From this variation, the magnitude of the directed part of the rectified field, which falls through the opening, may be measured.
• the disc 35 which is preferably made of metal, will, during rotation, alternately cover and thus screen the opening and leave the opening unscreened such that a variation of the penetrating stationary field is created.
• the invention is not limited to only comprise a disc but may also include a plurality of discs, preferably evenly divided on an axis. Also, the discs may be formed to completely cover the opening IS, or only a part thereof. The disc or discs may also be arranged, with the same result, to screen the whole sensor or parts thereof .
• the screen electrode may, for example, comprise a plurality of openings and, in certain applications, be designed from net or a perforated material.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)
• Measurement Of Resistance Or Impedance (AREA)
• Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
• Testing Relating To Insulation (AREA)

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Citations (4)

• 1996
  • 1996-07-15 SE SE9602785A patent/SE507933C2/sv not_active IP Right Cessation
• 1997
  • 1997-07-15 AU AU36396/97A patent/AU719566B2/en not_active Ceased
  • 1997-07-15 CN CN 97197676 patent/CN1229474A/zh active Pending
  • 1997-07-15 JP JP10505939A patent/JP2000514191A/ja active Pending
  • 1997-07-15 EP EP97933123A patent/EP0912902A1/en not_active Withdrawn
  • 1997-07-15 WO PCT/SE1997/001289 patent/WO1998005974A1/en not_active Application Discontinuation
  • 1997-07-15 BR BR9710724A patent/BR9710724A/pt not_active Application Discontinuation
  • 1997-07-15 TR TR1999/00074T patent/TR199900074T2/xx unknown
  • 1997-07-15 CA CA 2261191 patent/CA2261191A1/en not_active Abandoned
• 1999
  • 1999-01-14 NO NO990169A patent/NO990169L/no not_active Application Discontinuation

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