EP3371817A1 - Capteur de courant - Google Patents

Capteur de courant

Info

Publication number
EP3371817A1
EP3371817A1 EP16804898.1A EP16804898A EP3371817A1 EP 3371817 A1 EP3371817 A1 EP 3371817A1 EP 16804898 A EP16804898 A EP 16804898A EP 3371817 A1 EP3371817 A1 EP 3371817A1
Authority
EP
European Patent Office
Prior art keywords
core
current
power line
current transformer
high voltage
Prior art date
Legal status (The legal status 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 status listed.)
Pending
Application number
EP16804898.1A
Other languages
German (de)
English (en)
Inventor
Bertil Moritz
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
HM Power AB
Original Assignee
HM Power AB
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 HM Power AB filed Critical HM Power AB
Publication of EP3371817A1 publication Critical patent/EP3371817A1/fr
Pending legal-status Critical Current

Links

Classifications

    • 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 present invention concerns measurement of electric current in an electric power line. More precisely the invention concerns an apparatus and a method for measurement of electric current in a high power distribution line. Especially the invention concerns a sensor for current measurement. In particular the invention concerns a current ' transformer for high voltage.
  • high voltage distribution line an air insulated power line for distribution of electric power.
  • power line carries electric power in the range of 10 to 40 kilo Volts (kV).
  • a commonly used apparatus for current measurement of a high voltage electric conductor is a current transformer having a primary winding, a circular magnetisable core and a secondary winding.
  • the alternating current in the primary winding which is the power line to be measured, produces an alternating magnetic field in the core, which then induces an alternating current in the secondary winding.
  • An essential objective of current transformer design is to ensure the primary and secondary circuits are efficiently coupled, so the secondary current is linearly proportional to the primary current.
  • a common current transformer is costly to produce and for installing the conductor line needs to be cut and the system de-enerqized.
  • a current transformer with an openable core such as a crimp ampere meter is commonly used for low voltage applications.
  • the core of such apparatus comprises a pair of openable jaws of a magnetisable material to be encircling the conductor.
  • the conductor needs not to be cut nor de-energized.
  • the crimp ampere meter comprises an opening and a fulcrum, both of which disturbing the magnetic field.
  • the current transformer may be regarded as a three-part system comprising the primary winding, the coil and the secondary winding. For high voltage use there must be sufficient insulation between either the primary winding and the core or between the core and the secondary winding. It is known the use of a crimp ampere meter hung on the high voltage line where the signal from the secondary coil is sent to an instrument on ground potential by an optic fibre or an airborne signal.
  • the core of the crimp ampere meter is isolated from the high voltage conductor. Also the core of the crimp ampere meter comprises an opening and a fulcrum, both of which disturbing the magnetic field.
  • the known solution necessitates the presence of an electronic circuit and an electric power source such as a battery on the high potential level. This is a severe complication since such power source is increasing the production cost. An electronic circuit has limited service life time and increases the risk of malfunction. Besides such a power source needs maintenance and sometimes replacement. From US 7557563 (Gunn et al) a current sensor assembly is previously known. The current sensor comprises a clamp meter with two moveable jaws and a corona structure.
  • the corona structure has an outer boundary surrounding the electronics assembly and the conductor mountable device.
  • the corona structure may shield the electronic assembly and conductor mountable device from a corona producible with the power conductor.
  • the current sensor assembly may be a split- core design that includes multiple transformer cores.
  • the electronic assembly and the conductor mountable device may be powered by a line voltage supply on the power conductor. Data may be wirelessly transmitted and received with the sensor apparatus.
  • the current transformer is able to be mounted with a switching bar on a conductor having a high voltage.
  • the current transformer has a coil surrounding a U-shaped iron yoke.
  • a U-shaped ground iron is swivel-mounted on one leg of the iron yoke and is supported at a break point.
  • Springs are anchored on a housing of the transformer. When the current transformer is mounted, . the conductor moves the ground iron in a closing position and is maintained in such position by the springs.
  • the measurement signal is transferred by an optical fibre.
  • the object of the structure is to provide an openable core without pivotal connections for embracing an alternating current carrying conductor.
  • the magnetic core is formed of a plurality of strips of laminations of oriented silicon steel. After forming the core a secondary winding is applied. In order to avoid corrosion the core is covered with a hardenable plastic neoprene rubber. In an embodiment the core is self closing in butt contact and in yet another embodiment the core contains coupling members.
  • the known core and secondary winding as shown in the figures is only applicable on low voltage connectors.
  • a primary object of the present invention is to seek ways to improve a current transformer capable of sensing a current on a high voltage power line and producing a non-hazardous signal at ground potential level.
  • the current transformer comprises a power line encircling core at high voltage potential.
  • the core comprises an openable homogeneous ring of a magnetisable material.
  • homogeneous ring should be understood a ring comprising the same material and cross section all around. Hence the core contains no fulcrum, joint or other discontinuities.
  • the core material comprises a plurality of stacked metal sheets.
  • high voltage potential should be understood a voltage potential deviating within 10 % of the power line potential.
  • the core is in electric contact with the power line. Thus the core receives the same potential as the power line.
  • the core is embedded in a thin protective coating which would result in a voltage potential somewhat lower than the power line.
  • the core is openable to be hung onto the power line.
  • the core comprises a flexible structure with one opening only.
  • the core comprises openable overlapping ends which when closed offers a large overlapping surface which strengthen the magnetic field in the core.
  • the current transformer comprises high voltage insulation between the core and the secondary winding.
  • the high voltage insulation comprises a tubular insulation body covering part of a ring formed core, and a secondary winding wound on the insulating body.
  • the tubular insulating body comprises an inner conductive layer, an insulating layer and an outer conductive layer.
  • the tubular insulating body comprises at both ends electric field stress reducing means.
  • Such means comprises for instance a field control stress cone or a field control compound, which is. used for high voltage cable terminations.
  • the signal may, be measured at ground level without any risks of hazardous incidences. Hen,ce the current transformer according to the invention is completely passive and needs no extra power to produce a measureable signal at ground level. Analyzing instruments and means for wirelessly transmitting the signal may be easily used and powered on ground level.
  • the core comprises a plurality of iron strips. The plurality of iron strips forms in an embodiment a square cross section of the core.
  • the openable ring core comprises
  • the design is equivalent to the use of a magnetic material with higher permeability.
  • the current transformer according to the invention provides an easy to install current transformer on a live overhead line conductor, which requires the current transformer to open and close the magnetic circuit. Both sufficient insulation of the secondary winding and sufficient magnetic properties of an openable core are fulfilled.
  • the iron core is a magnetic circuit which should have high permeability all 360 degrees around. If the openable section contains insulation required to
  • iron core is positioned at high voltage potential.
  • the iron core receives the same voltage as the overhead line conductor. All non openable iron cores are traditionally at low voltage or ground potential.
  • iron core is understood as synonymous to high magnetic permeability material formed in an enclosing loop.
  • the core comprises a mechanism for keeping the overlapping ends of the core in an open position. This enables an operator to push the core onto the power line with a long insulated rod.
  • the mechanism comprises locking means for pressing the overlapping ends towards each other after the core has been mounted onto the line. The presence of the overlapping ends of the core provides the core to be positioned almost in parallel with the power line. The demand of a current transformer is only that the ring core encircles the power line. By keeping the core in almost parallel position with the power line the distance to adjacent lines may be kept smaller without any risk of flashover.
  • a current transformer for measurement of a high voltage power line comprising an openable magnetisable ring core encircling the power line and a secondary winding for sensing a current in relation to the current of the high voltage power line, wherein the core comprises overlapping ends having an overlapping area, extending the cross section of the core, and that the core receives high voltage potential.
  • the current transformer comprises a tubular insulating body enclosing part of the ring core and the tubular insulating body insulates the secondary winding from the ring core thereby providing a non-hazardous measurable current at ground level.
  • the openable ring core comprises overlapping ends.
  • the overlapping distance is greater than the cross section of the core.
  • the tubular insulating body comprises an inner conductive layer, an insulating layer and an outer conductive layer.
  • the tubular insulator body comprises stress grading means at each end portion.
  • magnetisable core comprises a plurality of iron sheets.
  • the tubular insulating body comprises a weather protection with a plurality of protruding circular sheds for increasing the creeping distance.
  • the object is achieved by a method for current measurement of a high voltage power line comprising an openable magnetisable core encircling the power line and a secondary winding for sensing a current in relation to the current of the high voltage power line, wherein the method contain providing a stack of iron strips having a first and second end portion, welding the first end portions of all strips, threading a prefabricated tubular insulating body onto the stack of strips, bending the stack of strips together with the tubular insulating body to form a ring core with overlapping ends, threading the openable ring core onto the power line, and reading the current at ground level.
  • the method further comprises forming an inner conductive layer around part of the ring core, providing on the inner conductive layer a tubular insulating layer, providing on the tubular insulating layer an outer conductive layer, and providing at each end of the outer conductive layer a stress grading means.
  • Fig 1 is a view of a current transformer according to the
  • Fig 2 is a cross section of a longitudinal cut of a tubular
  • Fig 3 are principal sketches of openable ring cores
  • Fig 4 are two principal sketches of the opening and locking arrangement of the openable core. DESCRIPTION OF PREFERRED EMBODIMENTS
  • the current transformer according to Fig 1 comprises an iron core 13 encircling a high voltage conductor 12, and a tubular insulating body 1 comprising the secondary winding.
  • the tubular insulating body provides high voltage insulation between the core and the secondary winding.
  • the insulating body is covering part of the core leaving a part of the core to be in contact with the conductor.
  • the core receives the same potential as the high voltage conductor.
  • the core is embedded in a thin protective coating and thus receiving a voltage potential somewhat lower than the high voltage conductor.
  • the core comprises an openable homogeneous ring of a magnetisable material. By the expression homogeneous should be understood that the ring comprises the same material and preferably the same cross section all along.
  • the ring may have any geometrical form but is preferably circular.
  • the insulating body 1 comprises a mid section 2 carrying a secondary winding, a first electric field grading end portion 3 and second electric field grading end portion 4.
  • the tubular insulating body comprises a weather protection 10 with a plurality of circular sheds 11 to lengthen the creepage distance.
  • the secondary winding is thus fully insulated from the iron core.
  • the tubular isolating body may be regarded as a short tube insulating an inner conductor, which in this case is the iron core.
  • the tubular insulating body comprises a cable 16 connected to the secondary winding to carry the signal from the secondary winding to an apparatus at ground level.
  • the tubular insulating body 1 comprises an inner conductive layer 6, an insulation layer 8, and an outer conductive layer 7.
  • Conductive in this context means sufficient conductivity to generate an almost equipotential layer, but not such high conductivity that any significant current is induced by the magnetic flux.
  • the secondary winding 9 is wound around the conductive layer 7.
  • the tubular insulating body comprises a stress relief pad 5 in each direction from the secondary winding. The stress relief pad is overlapping the
  • Each stress relief pad is made of a high permittivity stress grading compound and is gradually distributing the electric field along the surface over a distance long enough to avoid partial
  • the iron core 13 comprises overlapping ends 17.
  • the overlap area 14 in the preferred embodiment in Fig 3 is larger than the cross section of the iron core 15. This overlap reduces the magnetic resistance in the core.
  • the magnetic flux is shown, by dotted lines.
  • the overlap also makes it possible to apply a pressing force F between the airgap surfaces.
  • the magnetic flux is gradually .passing from one side to the other in the overlap area.
  • the ring core comprises a plurality of iron sheets.
  • the overlap arrangement as shown in the lower left of Fig 3 makes it possible to orient the ring core almost in parallel with the power line. This is advantageous since the distance between power lines can be kept small.
  • the cross section of the iron core is in the embodiment shown about 12 mm in square. In the embodiment shown the diameter of the core is greater than 200 mm.
  • the core comprises a locking mechanism according to Fig 4.
  • a first spring element 20 and a second spring element 21 are used to install the current transformer. In the left hand embodiment the spring mechanism is charged to an open position. When mounting, the second spring element 21 will be pressed
  • the click on spring device contains means to keeps the iron core almost parallel to the overhead power line and increase thereby the distance to adjacent phase line.
  • the air gap is protected by a foil which is removed by the overhead power line when it enters into the iron ring. This prevents particles from being trapped in the air gap during installation.
  • the airgap surfaces comprises a glue compound which when the core is mounted on a power line fix the overlapping ends for a long time.
  • Measuring electric current of a high power electrical conductor at ground level demands that the secondary winding which produces the measuring signal to a measuring instrument at ground potential exhibit sufficient insulation.
  • an overhead power line comprises a naked metal wire. If a signal from a current transformer should be at ground potential to serve low voltage electronic devices, the insulation has to be such that flashover or raised voltages are prevented.
  • the overhead lines which carry the primary current contain high voltage of 10-40 kilo Volts (kV).
  • the ring formed iron core is preferably made by winding a plurality of layers of an iron strip or lamination of oriented silicon steel to form a ring. When fully winded the ring is cut thus resulting in a stack of strips of different lengths having first and second end portions. The strips are oriented in parallel and all end portions at one side are welded together.
  • the prefabricated tubular insulating body 1 is treaded onto the now flat iron core. The collection of strips is then together with the tubular body bent to form a ring core with overlapping ends 17a, 17b. In this position all end portions of the other side of the core are welded together.
  • the scope of the invention must not be limited by the embodiments presented but contain also embodiments obvious to a person skilled in the art.
  • the ring core must not be circular but may comprise any geometric form encircling the line such for instance an oval shape.

Landscapes

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

Abstract

L'invention concerne un transformateur de courant de mesure d'une ligne électrique haute tension (12) comprenant un noyau d'anneau magnétisable ouvrable (13) comprenant une pluralité de bandes de fer entourant la ligne électrique et un enroulement secondaire (9) destiné à détecter un courant par rapport au courant de la ligne électrique haute tension. Le noyau (13) comprend des extrémités chevauchantes (17a, 17b) ayant une zone de chevauchement (14), et le noyau reçoit un potentiel élevé.
EP16804898.1A 2015-11-05 2016-11-04 Capteur de courant Pending EP3371817A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE1500444 2015-11-05
PCT/IB2016/001583 WO2017077379A1 (fr) 2015-11-05 2016-11-04 Capteur de courant

Publications (1)

Publication Number Publication Date
EP3371817A1 true EP3371817A1 (fr) 2018-09-12

Family

ID=57442749

Family Applications (1)

Application Number Title Priority Date Filing Date
EP16804898.1A Pending EP3371817A1 (fr) 2015-11-05 2016-11-04 Capteur de courant

Country Status (3)

Country Link
EP (1) EP3371817A1 (fr)
CN (1) CN108352249B (fr)
WO (1) WO2017077379A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112837916B (zh) * 2021-01-27 2022-02-01 江阴市星火电子科技有限公司 一种带屏蔽的开合式零序电流互感器

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB549567A (en) * 1940-10-31 1942-11-26 British Thomson Houston Co Ltd Improvements in and relating to electric transformers
GB846208A (en) * 1957-10-18 1960-08-31 Landis & Gyr Ag Improvements in high voltage current transformers
US3725832A (en) * 1971-10-12 1973-04-03 Schwertzer E Mfg Co Inc Magnetic core structure
DE2843608C2 (de) * 1978-10-06 1983-09-29 Friedrich Dr.-Ing. e.h. 8600 Bamberg Raupach Transformator, insbesondere Spannungswandler oder Prüftransformator
DE8806688U1 (de) * 1988-05-19 1988-07-14 Siemens AG, 1000 Berlin und 8000 München Wickelstromwandler
FR2672152B1 (fr) * 1991-01-29 1993-05-07 Bardin Ets Tore de transformateur, et procede de fabrication d'un tel tore.
FR2700395B1 (fr) * 1993-01-08 1995-04-21 Bardin Ets Transformateur, notamment transformateur de mesure, par exemple pour la détection de défauts sur les câbles électriques.
DE4331265C2 (de) 1993-09-15 2001-03-29 Horstmann Gmbh Dipl Ing H Stromwandler für elektrische Leiter
JPH08250351A (ja) * 1995-03-14 1996-09-27 Tohoku Denki Hoan Kyokai 変流器
CN2775813Y (zh) * 2004-12-31 2006-04-26 范晓明 精密钳型电流互感器
ES2435740T3 (es) 2005-01-19 2013-12-23 Power Measurement Ltd Aparato sensor
CN102623153B (zh) * 2012-03-29 2016-02-24 中国电力科学研究院 一种电流互感器绝缘护套

Also Published As

Publication number Publication date
CN108352249B (zh) 2020-10-20
WO2017077379A1 (fr) 2017-05-11
CN108352249A (zh) 2018-07-31

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