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WO2011030359A1 - Capteur pour mesurer des courants variables - Google Patents

Capteur pour mesurer des courants variables Download PDF

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Publication number
WO2011030359A1
WO2011030359A1 PCT/IT2009/000404 IT2009000404W WO2011030359A1 WO 2011030359 A1 WO2011030359 A1 WO 2011030359A1 IT 2009000404 W IT2009000404 W IT 2009000404W WO 2011030359 A1 WO2011030359 A1 WO 2011030359A1
Authority
WO
WIPO (PCT)
Prior art keywords
tube
current
slit
electric
current transducer
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.)
Ceased
Application number
PCT/IT2009/000404
Other languages
English (en)
Inventor
Mario La Rosa
Michela Audone
Antonio Benedetto Francesco Orlandi
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.)
Individual
Original Assignee
Individual
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 Individual filed Critical Individual
Priority to PCT/IT2009/000404 priority Critical patent/WO2011030359A1/fr
Publication of WO2011030359A1 publication Critical patent/WO2011030359A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

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
    • G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
    • G01R15/186—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using current transformers with a core consisting of two or more parts, e.g. clamp-on type
    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16533—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application
    • G01R19/16538—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application in AC or DC supplies
    • G01R19/16547—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application in AC or DC supplies voltage or current in AC supplies

Definitions

  • This invention is concerned with a current transducer for measuring variable currents, particularly A.C. currents.
  • a high-strength current must be converted to a proportional, weaker current, which is compatible with the measuring ammeter.
  • Several types of current transducers are known to be used for such purpose, among which the most usual are shunts, amperometric transformers and Rogowski coils.
  • the shunt is the simplest and cheapest device for proportionally reducing a current. It consists of a small resistance in series with a main circuit, intended to derive a voltage signal proportional to the load current flowing through it.
  • a drawback of the shunt is that its measuring circuit is not insulated from the power circuit: this circumstance makes it unfit for heavy overloads.
  • Other drawbacks are due to the fact that the resistance of the shunt is typically affected by a parasite series inductance and by a parasite parallel capacity. Accordingly, at high frequencies, the parasite inductance will displace the phase of voltage and current, while, at high frequencies, the parasite inductance and capacity together may give rise to resonances. Moreover, high values of the currents will cause large dissipation and consequently heating, which in turn will give rise to variations of the resistance R. This resistance is also affected by the parasite resistances at the connection terminals between cables and shunts, which are unstable and random.
  • amperometric transformers which may be used either for purposes of mere protection or with the purpose of converting the quantity to be measured, although some of them have both functions.
  • the primary and secondary currents are not exactly linked by the nominal transformation ratio: the relationships of the ideal transformer are approximations of the real ones.
  • the differences between the indications that would be delivered by an ideal transformer and the actual indications of the real transfomer are called errors, and may be phase errors as well as value errors.
  • the Rogowski coil typically consists of an air-cored coil which is wound in a toroidal shape around a conductor in which it is desired to measure a current. The measurement is based on Ampere's law and is made by integrating the voltage across the coil in order to obtain as an output a signal that is substantially proportional to the current to be measured.
  • the Rogowski coil is not free from drawbacks, among which is saturation, which may develop when the coil voltage is too high, and slew-rate. Moreover, at high frequencies the self-inductance and the self-capacity of the coil become significant and consequently there may be problems with the phase and the value, and even a resonance.
  • the main object of this invention is now to obviate the above drawbacks, by providing a current transducer that will reduce the reading errors with respect to the prior art.
  • the invention aims at providing a current transducer that is particularly suitable for measuring strong currents, such as the currents flowing in railway overhead wires or train rails.
  • Another object of the invention is to provide a current transducer that does not interfere with the conductor in which the measurement is to be carriedc out, and that does not require modifications to the conductor.
  • a further object of the invention is to dispense with ferromagnetic cores and with the attendant problems due to saturation, to stray currents and to hysteresis loops.
  • Still another object of the invention is to provide a measuring instrument the is compact and lightweight, highly reliable, and easy to implement at competitive costs.
  • a current transducer for measuring the strength of variable electric currents in conductors, particularly unifilar electric lines, characterized in that it comprises a tube of a conductive material, curved to substantially define a torus to be placed coaxially around a conductor where the electric current is to be measured, the tube being provided, substantially along its entire surface, of a slit lying entirely on a circumferential middle plane of the torus, the ends of said tube facing each other so that a gap is defined therebetween, said tube being provided with first electrical terminals on opposite sides of said slit, for connection to a current measuring instrument.
  • a current transducer for measuring the strength of variable electric currents in conductors, particularly in non-unifilar lines such as rails and the like, characterized in that it comprises a pair of tubes of identical shape, made of a conductive material and arranged side by side whereby a space is defined therebetween for a conductor where the electric current is to be measured, each tube comprising a slit extending substantially from one end to the opposite end of the respective tube, and entirely lying in a middle plane of the tube, each tube being provided with first electric terminals on opposite sides of the respective slit, for connection to a current measuring instrument.
  • Fig. l shows the mutual arrangement between a loop and a current conductor
  • Fig. 2 shows an electric circuit equivalent to the arrangement of Fig. l;
  • Fig. 3 shows a current transducer according to a first embodiment of the invention
  • Fig. 4 shows an electric circuit equivalent to the current transducer of Fig. 3, and free from terminals shorted to each other;
  • Fig. 5 shows a circuit corresponding to the circuit of Fig. 4.
  • a conductor 1 carrying an electric current variable in time generates a magnetic field 2 which links with loop 3 and induces an electromotive force therein. If the loop is closed, such electromotive force generates electric currents and an attendant magnetic field whose flux is in opposition to the variation of the magnetic flux linked with loop 3.
  • the electromotive force V induced in loop 3 is equal to the time derivative of the magnetic flux, with changed sign.
  • Fig. 1 is equivalent to the circuit of Fig. 2, comprising a voltage generator corresponding to the electromotive force and a series impe- dance consisting of the resistance and inductance of conductor 1.
  • a solid of revolution or of translation generated by a conductive loop 3 substantially as shown in Fig. ⁇ is used as a current transducer.
  • the current transducer comprises a tube 10 of a conductive material, shaped to define a torus which is to be placed coaxially around conductor n where the electric current is to be measured.
  • the conductors n with which the current transducer of the first embodiment preferably are unifilar lines, i.e. all wirelike, cylindrical or prismatic conductors liable to be surrounded by a torus as in Fig. 3, without having to be disassembled from their site.
  • Tube 10 The perimeter of the torus defined by tube 10, and more specifically its external perimeter, is cut with a slit 12, entirely lying in the circumferential middle plane of the torus.
  • Tube 10 can therefore be seen as a solid of revolution around conductor 11, having a C-shaped loop as a generatrix. The revolution, however, is not complete, as the ends of tube 10 face each other, thereby defining a gap 13 inbetween. Thanks to such a gap, tube 10 can be easily placed in toroidal shape around a wirelike conductor, which can be inserted through gap 13.
  • First electric terminals 16 and 17 are attached close to gap 13, on opposite sides of slit 12 and suitable for connection to a conventional ammeter, without any intermediate electrical parts, such as integrators.
  • Another pair of second electric terminals 14 and 15 are attached to the other end of tube 10, also on opposite sides of slit 12, so that the first and second electric terminals, 14-15 and 16-17, ar e placed on opposite sides of gap 13.
  • Resistor r ; and inductore Li represent the resistance and inductanza of the i-th loop.
  • Inductors li represent the mutual inductances that develop among the loops.
  • Ci-Ri e C2-R2 represent, in an equivalent circuit with lumped parameters, the parasite capacities and resistances of the several loops.
  • capacitors Ci and C2 may be regarded as equal to each other and having the same capacity C.
  • resistors Ri and R2 may also be regarded as equal to each other and having the same resistance R.
  • the equivalent circuit comprises an equivalent generator of electromotive force V-rot, an equivalent impedance Zeq , and a mutual inductor hot which defines, together with inductance I L of conductor 11, a mutual inductance Mrot.
  • the quadratic dependence from frequency can be removed in the foregoing relation, by connecting an inductor 19 across terminals 14-15 or 16-17, the inductor being preferably wound in air or on ferrite.
  • the absolute value of the equivalent impedance Z EQ is much smaller than the product G)L 19 , the foregoing relation becomes
  • a current transducer 20 comprises a pair of tubes 21 and 22 of identical shape, e.g. prismatic or cylindrical, both made of a conducting material at placed side by side so that they define a space therebetween for a conductor 31 in which it is desired to measure the electric current.
  • Conductor 31 is preferably not of the air-wound kind, and is not surroundable by a toroidal tranducer according to Fig. 3. According to an example of a typical application of the invention, conductor 31 would be the rail of a railroad.
  • Tubes 21 and 22 can be regarded as solids of translation, in which the generatrix is a C- shaped loop that is displaced along the axis of the respective tube.
  • Each of tubes 21 and 22 comprises a slit 21a and 22a, longitudinally extending from end of the tube to the opposite end, and completely lying in the middle plane of the tube.
  • each tube 21, 22 is provided, at its upper end, with first electric terminals 23, 24 and 25, 26 on opposite sides of the respective slit 21a, 22a.
  • a pair 23-24 of the first terminals is used for direct connection to a current measuring instrument, while first terminals 25-26 belonging to the other tube are preferably shorted to each other.
  • each tube 21 and 22 comprises second electric terminals 27, 28 and 29, 30, which are arranged on opposite sides of the respective slit 21a and 22a, and substantially at the other end of the tube.
  • Each electric terminal 27 and 28 of first tube 21 is short-circuited with a corresponding electric terminal 30 and 29 of the other tube 22.
  • the connecting cables are preferably braided, in order to improve its behavior at varying frequencies.
  • Tubes 21 and 22 are made fast to each other by means of a support 32 of an insulating material, so that their mutual distance is maintained constant and that the current tranducer 20 may be easily installed.
  • transducer of the invention has been developed particularly for overhead lines and rails carrying heavy currents, it can be used for measuring currents in wirelike conductors more generally, whether cylindrical or prismatic.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)

Abstract

Le capteur de courant de l'invention correspond à un solide de révolution ou de translation, dans lequel la génératrice est une boucle conductrice sensiblement en forme de C. Dans un premier mode de réalisation, le capteur est un tube (10) courbé pour définir un torus à placer coaxialement autour d'un conducteur (11) où le courant électrique doit être mesuré, le tube (10) étant pourvue d'une fente circonférentielle (12) et d'un espace (13) entre les extrémités du tube. Dans un second mode de réalisation, le capteur comprend une paire de tubes en face l'un de l'autre (21, 22), par exemple des tubes prismatiques ou cylindriques, chaque tube (21, 22) comprenant une fente (21a, 22a) se prolongeant partir d'une des extrémités vers l'extrémité opposée. Dans les deux cas, les tubes sont dotés de bornes électriques (13, 14, 16, 17 ; 23, 24 ; 25, 26) se trouvant exclusivement dans un plan médian du tube, chaque tube (21, 22) étant pourvus de premières bornes électriques (23, 24 ; 25, 26) sur les côtés opposés de la fente pour permettre une connexion directe à un ampèremètre, les bornes restantes étant court-circuitées les unes par rapport aux autres ou bien fermées d'une autre manière pour fermer le circuit défini par le tube.
PCT/IT2009/000404 2009-09-09 2009-09-09 Capteur pour mesurer des courants variables Ceased WO2011030359A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/IT2009/000404 WO2011030359A1 (fr) 2009-09-09 2009-09-09 Capteur pour mesurer des courants variables

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/IT2009/000404 WO2011030359A1 (fr) 2009-09-09 2009-09-09 Capteur pour mesurer des courants variables

Publications (1)

Publication Number Publication Date
WO2011030359A1 true WO2011030359A1 (fr) 2011-03-17

Family

ID=42194716

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IT2009/000404 Ceased WO2011030359A1 (fr) 2009-09-09 2009-09-09 Capteur pour mesurer des courants variables

Country Status (1)

Country Link
WO (1) WO2011030359A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111697355A (zh) * 2020-05-21 2020-09-22 国网浙江省电力有限公司嘉兴供电公司 一种不断电电表更换装置监测系统

Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4384289A (en) * 1981-01-23 1983-05-17 General Electric Company Transponder unit for measuring temperature and current on live transmission lines
DE3544508A1 (de) * 1985-12-17 1987-06-19 Ulrich Dipl Ing Adolph Kombinationswandler zur gleichzeitigen messung von strom und spannung an rohrummantelten leitern
DE19505812A1 (de) * 1995-02-09 1996-08-22 Siemens Ag Stromerfassungsspule für einen Stromwandler
WO1999053331A1 (fr) * 1998-04-15 1999-10-21 Square D Company Detecteur pour la detection d'arc utilisant des inducteurs discrets
WO1999063352A1 (fr) * 1998-06-05 1999-12-09 Cooke Chathan M Capteur de type a induction magnetique a enroulements multiples couples de pres
WO2000045183A2 (fr) * 1999-01-29 2000-08-03 Suparules Limited Instrument de mesure de l'energie electrique
DE20101454U1 (de) * 2001-01-27 2001-05-23 Phoenix Contact Gmbh & Co., 32825 Blomberg Stromsensor auf Leiterplattenbasis
US20020011832A1 (en) * 1997-09-12 2002-01-31 Ertugrul Berkcan Primary current conductor configurations for a residential electronic meter
US20040201373A1 (en) * 2003-02-26 2004-10-14 Katsuhisa Kato Current probe
WO2005119274A1 (fr) * 2004-05-29 2005-12-15 Lem Heme Limited Procede et appareil de mesure de courant
US20060232263A1 (en) * 2005-01-06 2006-10-19 Kovanko Thomas E Current sensor arrangement
DE102007046054A1 (de) * 2006-09-29 2008-04-03 GM Global Technology Operations, Inc., Detroit Verbesserter hochgenauer Rogowski-Stromwandler
US20080106254A1 (en) * 2006-11-06 2008-05-08 Cooper Technologies Company Split Rogowski coil current measuring device and methods
WO2009021076A1 (fr) * 2007-08-06 2009-02-12 Yakymyshyn C Transducteur de courant à fente(s) utilisant des capteurs de points de champ magnétique

Patent Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4384289A (en) * 1981-01-23 1983-05-17 General Electric Company Transponder unit for measuring temperature and current on live transmission lines
DE3544508A1 (de) * 1985-12-17 1987-06-19 Ulrich Dipl Ing Adolph Kombinationswandler zur gleichzeitigen messung von strom und spannung an rohrummantelten leitern
DE19505812A1 (de) * 1995-02-09 1996-08-22 Siemens Ag Stromerfassungsspule für einen Stromwandler
US20020011832A1 (en) * 1997-09-12 2002-01-31 Ertugrul Berkcan Primary current conductor configurations for a residential electronic meter
WO1999053331A1 (fr) * 1998-04-15 1999-10-21 Square D Company Detecteur pour la detection d'arc utilisant des inducteurs discrets
WO1999063352A1 (fr) * 1998-06-05 1999-12-09 Cooke Chathan M Capteur de type a induction magnetique a enroulements multiples couples de pres
WO2000045183A2 (fr) * 1999-01-29 2000-08-03 Suparules Limited Instrument de mesure de l'energie electrique
DE20101454U1 (de) * 2001-01-27 2001-05-23 Phoenix Contact Gmbh & Co., 32825 Blomberg Stromsensor auf Leiterplattenbasis
US20040201373A1 (en) * 2003-02-26 2004-10-14 Katsuhisa Kato Current probe
WO2005119274A1 (fr) * 2004-05-29 2005-12-15 Lem Heme Limited Procede et appareil de mesure de courant
US20060232263A1 (en) * 2005-01-06 2006-10-19 Kovanko Thomas E Current sensor arrangement
DE102007046054A1 (de) * 2006-09-29 2008-04-03 GM Global Technology Operations, Inc., Detroit Verbesserter hochgenauer Rogowski-Stromwandler
US20080106254A1 (en) * 2006-11-06 2008-05-08 Cooper Technologies Company Split Rogowski coil current measuring device and methods
WO2009021076A1 (fr) * 2007-08-06 2009-02-12 Yakymyshyn C Transducteur de courant à fente(s) utilisant des capteurs de points de champ magnétique

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111697355A (zh) * 2020-05-21 2020-09-22 国网浙江省电力有限公司嘉兴供电公司 一种不断电电表更换装置监测系统

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