Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/42—Circuits specially adapted for the purpose of modifying, or compensating for, electric characteristics of transformers, reactors, or choke coils
  • H01F27/422—Circuits specially adapted for the purpose of modifying, or compensating for, electric characteristics of transformers, reactors, or choke coils for instrument transformers
  • H01F27/427—Circuits specially adapted for the purpose of modifying, or compensating for, electric characteristics of transformers, reactors, or choke coils for instrument transformers for current transformers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/28—Coils; Windings; Conductive connections
  • H01F27/2823—Wires
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/28—Coils; Windings; Conductive connections
  • H01F27/32—Insulating of coils, windings, or parts thereof
  • H01F27/324—Insulation between coil and core, between different winding sections, around the coil; Other insulation structures
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F3/00—Cores, Yokes, or armatures
  • H01F3/06—Cores, Yokes, or armatures made from wires
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
  • H01F38/20—Instruments transformers
  • H01F38/22—Instruments transformers for single phase AC
  • H01F38/28—Current transformers
  • H01F38/30—Constructions
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
  • H01F38/20—Instruments transformers
  • H01F38/22—Instruments transformers for single phase AC
  • H01F38/28—Current transformers
  • H01F38/30—Constructions
  • H01F2038/305—Constructions with toroidal magnetic core

Definitions

• the invention relates to a device for measuring an electric current, and more particularly to a measuring device comprising a current transformer provided with a flexible magnetic opening circuit in the form of a torus and capable of closing on a cable in which the current to be measured.
• a Rogowski torus is an electro-mechanical air-core device for measuring alternating current or high-speed current pulses. As is illustrated in FIG.
• a Rogowski winding 1 conventionally consists of an electric wire 2 comprising a first part 3 wound helically around a sheath 4, and a second part 5 integral with a first end 6 of the first part 3, the second part 5 of the wire 2 passing through the helical winding 3, and thus the sheath 4, along its axis of winding over the entire axial length of the helical winding to a second end 7 of the first part 3 of the wire 2, so that the two electrical terminals 8 and 9 of the electric wire 2 are at the same end of the Rogowski winding 1.
• the Rogowski coil 1 is positioned around the conductor C whose current is to be known.
• the voltage induced in the winding is proportional to the rate of change (derived) of the current in the conductor.
• Rogowski torus over other types of current sensors is its good flexibility mainly due to the absence of a rigid metal core, property that other current sensors have little or no . This flexibility allows it to be wrapped around one or more phase conductors without constraint.
• the flexible opening toro Rogowski type have the desired mechanical properties, they do not, however, the performance compatible with all areas of application including to use this sensor on a neutral type GT (impedant neutral) in which the measurement of differential currents is often at a very low level and at low frequencies.
• GT impedant neutral
• ferromagnetic core devices rather than air core, to overcome this disadvantage.
• These types of torus known generally comprise a magnetic circuit in two rigid parts whose performance corresponds to those of the need for application but have not only the disadvantages related to their size and their rigidity, but also those related to the presence of two airgaps.
• a known solution is proposed in patent EP 0 999 565. It is a current transformer comprising a coil wound around a magnetic circuit consisting of a stack of flat strips free between them and very little maintained and fixed at each end. The magnetic circuit is electrically isolated from the winding, the transformer is configured to connect together the two ends of the magnetic circuit when the current transformer is closed around the electrical conductor on which the current measurement is to be performed.
• the magnetic circuit is not flexible in all major directions identically.
• the absence of the same flexibility in all the main directions does not allow an easy implementation of the measuring device.
• the movement of the bands causes variations in the visible section of the magnetic core that are detrimental to performance.
• the control of the constancy of the section of the magnetic core allows a repeatability of the measurement in any geometric configuration of the sensor.
• the aim of the invention is to overcome the drawbacks mentioned above by proposing a current transformer with a flexible magnetic circuit in all principal directions in an identical manner and while maintaining the measurement performance of very low amplitude electrical currents and of low frequencies and low manufacturing cost.
• an opening current transformer intended to close on an electrical conductor in which circulates an electric current to be measured or on several electrical conductors in which electrical currents are circulated whose vector sum is to be measured.
• the current transformer comprising a magnetic circuit and an electrically conductive winding wound around and electrically isolated from the magnetic circuit, the winding comprising a single winding or a plurality of separate windings coupled in series.
• the magnetic circuit comprises a set of son of magnetic material, the son being assembled together in the form of a strand.
• a flexible magnetic core device allows access to measurement points in particularly confined or narrow areas.
• the assembly of the son in the form of strand provides the magnetic circuit, and by extension to the transformer, a uniform flexibility in all directions, and thus a flexibility identical to that of a wire rope.
• the invention comprises a plurality of separate wires twisted together to form a magnetic cable around which the winding is wound electrically. conductor, the cable having two ends that can be connected together to form a closed annular shape to be traversed by an electrical conductor to be measured.
• the magnetic material of the son can be a high magnetic permeability Fer-Nickel alloy with at least 70% nickel, and preferably between 78 and 81% nickel.
• the son are mechanically isolated from each other by magnesium methoxide, or by powder of alumina (Al2O3) or magnesia (MgO) during their assembly to avoid collages between the son.
• Al2O3 powder of alumina
• MgO magnesia
• the wires are free from each other.
• the device is easily deformable without losing its characteristics.
• each wire comprises a plurality of strands of magnetic material twisted together as a strand.
• Each wire thus forms a strand of strands of magnetic material.
• the wires are then twisted together to form the magnetic circuit cable in the form of a strand of wires.
• the strands of each wire are mechanically isolated from each other by magnesium methoxide, or by powder. of alumina (AI 2 O 3 ) or magnesia (MgO) during their assembly to avoid collages between the strands of the son.
• alumina AI 2 O 3
• MgO magnesia
• the strands are free from each other which improves the flexibility characteristics of the cable.
• each wire strand may have a diameter of between 0.1 mm and 0.5 mm and preferably a diameter of 0.20 mm.
• the transformer may further comprise an electrically insulating flexible tubular inner sheath on which said winding is wound and in which the magnetic circuit is fitted.
• the transformer may further comprise an electrically insulating tubular outer sheath surrounding said winding to protect the winding of the external environment as well from any external electrical contact as possible impact.
• the winding may comprise a plurality of separate windings coupled in series, at least two windings comprising enamelled conductive wire, that is to say covered with an electrically insulating coating, and being radially superimposed to form a stack in a radial direction relative to the winding axis of the winding.
• said at least one winding of the winding may comprise a copper electrical wire having a diameter of between 0.2 mm and 0.8 mm and preferably 0.4 mm.
• the transformer may comprise snap-fastening means or screwing means.
• a device for measuring an electric current comprising an opening current transformer as defined above, and processing means electrically coupled to the winding of the current transformer.
• FIG. 2 shows schematically a partial perspective view partially broken away of a current transformer 10 according to one embodiment of the invention
• FIG. 3 schematically shows a view of the closure means of the current transformer according to one embodiment of the invention
• FIG. 4 schematically shows a device for measuring an electric current comprising a current transformer according to one embodiment of the invention.
• Figure 2 is shown schematically a partial perspective view partially broken away of a current transformer 10 according to one embodiment of the invention.
• the current transformer 10 has an opening toroidal shape intended to close on an electrical conductor in which circulates an electric current, alternating or continuous, to be measured or on several electrical conductors in which electric currents are circulated whose vector sum is to be measured. .
• the current transformer 10 comprises a magnetic circuit 11 inserted into an electrically insulating and flexible tubular inner sheath 12.
• the magnetic circuit 11 is formed of a plurality of son 110 of magnetic material, for example son in an alloy comprising 15% iron, 80% nickel, and 5% molybdenum.
• the magnetic circuit 11 comprises seven wires 110.
• the seven son 110 are assembled together as a strand to form a cable.
• the cable forming the magnetic circuit may comprise two wires or several tens of wires.
• Each wire 110 may be formed of a plurality of strands of magnetic material twisted together. Each wire 110 thus forms a strand of strands of magnetic material, and each strand formed by a wire 110 is assembled with the other wires 110 of the magnetic circuit to form a son strand 110 forming the cable 11.
• the strands from which the yarns 110 are formed are made of a high magnetic permeability ferronickel-molybdenum alloy having 80% nickel.
• the son 110 may have sections of various sizes, for example a section of 4.6 mm 2 .
• 11 may comprise several son 110 each formed of several strands each having a diameter of about 0.2 mm to form a cable having an iron section of about 0.3 cm 2 .
• the number of strands in each wire 110 and the structure of the strand forming the magnetic cable 11, in particular the number of wires 110 constituting the cable of the magnetic circuit 11, are adaptable according to the desired sensitivity and the size envisaged for the cable of the magnetic circuit 11.
• the cable 11 is flexible in all directions due to its strand structure.
• the cable 11 undergoes a high temperature heat treatment under reducing gas, such as hydrogen, so as to restore and optimize the magnetic performance of the material.
• reducing gas such as hydrogen
• Each wire 110 is geometrically and electrically isolated before annealing the heat treatment phase of the cable 11 in order to avoid collages between the wires during the heat treatment.
• This isolation operation is carried out from magnesium methoxide or alumina powder (Al 2 O 3 ) or magnesia (MgO), or from another technology, or by direct application on the wire before the formation of the wire strand 110 forming the cable 11 or by application to the cable 11 after the formation of the son strand 110.
• the isolation operation is performed on the strands either before the formation of the son, or well after the formation of the son 110 but before the formation of the cable 11, or after the formation of the cable 11, the treatment being a chemical treatment that can reach the entire surface of a strand by capillarity even once after the cable has been form.
• the insulation of each strand thus allows a sliding between the strands and thus improve the flexibility characteristics of the cable 11.
• the cable 11 is then cut to the desired length and then has two ends 111 and 112.
• the two ends 111 and 112 of the cable 11 are crimped to maintain the son 110 between them.
• the two end sections 111 and 112 are intended to be facing each other and in contact when the current transformer 10 is closed, as illustrated in FIGS. 3 and 4 in particular, to form a closed magnetic circuit.
• the two sections at the ends 111 and 112 of the cable 11 are polished to optimize the air gap ensuring good roughness, good parallelism and a zone the least disturbed possible from the magnetic point of view.
• the tubular inner sheath 12 forms a sleeve traversed axially, that is to say along the axis of revolution of the sheath 12, by the magnetic circuit 11, that is to say by the cable.
• the inner sheath 12 is a tube of insulating material sufficiently strong to withstand the winding of a copper wire having a diameter in particular between 0.20 and 0.8 mm while having sufficient flexibility to maintain that of the cable 11.
• the inner sheath 12 may be a tube of PVC material, Rylsan® or the like, with an inside diameter of between 10 and 25 mm and a wall thickness of between 1 and 2 mm.
• the current transformer 10 further comprises an electrically conductive winding 13.
• the inner sheath 12 forms a winding support for the winding 13.
• the winding 13 is formed by a copper wire wound around the inner sheath 12 back and forth over the entire length of the magnetic circuit 11.
• the coil 13 is wound a first time from the first end 111 of the cable to the second end 112 of the cable 11 and a second time from the second end 112 of the cable 11 to the first end 111 of the cable 11.
• the enameling of the copper wire of the coil allows to isolate the wire and avoid any short circuit in particular between the superimposed portions.
• the coil 13 may comprise a plurality of copper windings coupled together in series.
• the coil 13 has a first end 131 and a second end 132 opposite the first end 131.
• the coil 13 being wound up and down around the inner sheath 12, the first and second ends 131 and 132 of the coil 13 are located at one end of the cable 11 which is the first end 111 of the cable 11 in the example illustrated in FIG.
• the winding 13 may comprise 1000 turns wound regularly around the inner sheath 12 in return for a length that can be adapted according to the size of the primary conductors and can be between 200 and 2000 mm so as to constitute, after closure of the current transformer 10, loops whose diameter is between 70 and 700 mm.
• the current transformer 10 further comprises an electrically insulating tubular outer sheath 14.
• the outer sheath 14 is fitted over the assembly comprising the cable 11, the inner sheath 12 and the winding 13 so as to envelop the winding 13 and isolate it from the external electrical environment of the current transformer 10.
• Figure 3 schematically shows a view of the closure means 15 of the current transformer 10 according to one embodiment of the invention.
• the current transformer 10 also comprises, in this embodiment, snap-fastening means 15 comprising a male portion 150 mounted on a first end 101 of the current transformer 10 and a female portion 155 complementary to the male portion 150 and mounted on a second end 102 of the current transformer 10 opposite the first end 101 of the current transformer 10.
• the first end 111 of the cable 11 and the first and second ends 131 and 132 of the coil 13 are located on the first end 101 of the current transformer 10 while the second end 112 of the cable 11 is located on the second end 102 of the current transformer 10.
• the female portion 155 comprises a tubular shape and circular grooves 156 formed on the radially inner surface of the tube of the female portion 155.
• the male portion 150 comprises a cylindrical shape configured to be inserted into the tubular shape of the female part 155.
• the male part 150 comprises in or be circular serrations configured to cooperate with the splines 156 of the female portion 155 to close the current transformer 10.
• the current transformer may comprise screw closure means.
• the quality of the assembly is evaluated by measuring the magnetic permeability: with a sufficiently rigid closing device the permeability of the assembled cut circuit can be between 15 000 and 20 000.
• the closure device 15 is such that the sensor is easy to open without special tools.
• FIG. 4 diagrammatically shows a device for measuring an electric current comprising a current transformer 10 in the form of an opening toroid and processing means 16 electrically coupled to both ends 131 and 132 of the coil 13.
• the processing means 16 allow to receive the current induced in the winding 13 of the current transformer 10 and thus to measure the electric current flowing through the electrical conductor around which the current transformer 10 has been closed.
• the invention thus provides a current transformer Rogowski type with a flexible magnetic circuit in all major directions in the same manner, while maintaining the measurement performance of electrical currents of very low amplitude and low frequencies and a low manufacturing cost, and a measuring device provided with such a current transformer.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Transformers For Measuring Instruments (AREA)
• Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)

Applications Claiming Priority (2)

Publications (3)

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ID=62067652

Family Applications (1)

Country Status (6)

Families Citing this family (8)

Family Cites Families (16)

• 2018
  • 2018-01-05 FR FR1850064A patent/FR3076657B1/fr active Active
  • 2018-12-21 EP EP18842807.2A patent/EP3735702B1/de active Active
  • 2018-12-21 KR KR1020207022735A patent/KR102640694B1/ko active Active
  • 2018-12-21 WO PCT/FR2018/053530 patent/WO2019135044A1/fr not_active Ceased
  • 2018-12-21 CN CN201880085569.9A patent/CN111630615A/zh active Pending
  • 2018-12-21 US US16/960,199 patent/US12027305B2/en active Active

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