WO1986003883A1 - Process for reducing the transmission error of current transformers, and precision current transformers - Google Patents
Process for reducing the transmission error of current transformers, and precision current transformers Download PDFInfo
- Publication number
- WO1986003883A1 WO1986003883A1 PCT/HU1985/000079 HU8500079W WO8603883A1 WO 1986003883 A1 WO1986003883 A1 WO 1986003883A1 HU 8500079 W HU8500079 W HU 8500079W WO 8603883 A1 WO8603883 A1 WO 8603883A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- magnetic flux
- amplifier
- iron core
- current transformer
- coil system
- Prior art date
Links
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
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R17/00—Measuring arrangements involving comparison with a reference value, e.g. bridge
- G01R17/02—Arrangements in which the value to be measured is automatically compared with a reference value
- G01R17/06—Automatic balancing arrangements
Definitions
- the invention relates to a method for
- the aim of the invention is to develop a method and a current transformer by means of which the error caused by the winding capacitances can be reduced to a significant extent.
- the invention is based on the knowledge that the error caused by the winding capacitances can be compensated if the speed of the magnetic flux change is detected in the iron core of the current transformer and a compensation coil arranged on the iron core is fed with a signal proportional thereto.
- the invention thus consists on the one hand in a method for reducing the transmission error of current transformers which contain a primary coil system and secondary coil system arranged on an iron core, the magnetic flux or the speed of the change in magnetic flux in the iron core of the current transformer being detected and a first proportional to the speed of the change in magnetic flux Electrical signal is generated, with which a compensation coil compensating the excitations resulting from the winding capacitances of the coil systems is fed.
- the error caused by the winding capacitances can be reduced to a significant extent by approximately two orders of magnitude, i.e. practically eliminable.
- the compensation coil is fed with a first voltage proportional to the speed of the change in the magnetic flux via a capacitor connected in series. In this case, the error compensation is almost independent of the frequency.
- the invention further relates to a precision current transformer which is provided with a primary and secondary coil system arranged on an iron core, the current transformer having a signal transmitter for detecting the rate of change of the magnetic flux of the iron core, a compensation coil arranged on the iron core or on an indicator core, and one Output of the signal generator connecting, first amplifier is formed, wherein the output of the first amplifier is connected to the compensation coil.
- the arrangement of the compensation coil on the iron core enables subsequent expansion, while the arrangement on the indicator core does not take into account the inductive feedback.
- second amplifier is connected to the output of the signal transmitter, the output of which is connected to a terminal leading to the load impedance of the secondary coil system. In this case the fault becomes independent of the load impedance.
- the signal transmitter can be designed extremely simply by a detector coil arranged on the iron core, but other solutions are also possible, for example the use of a Hall probe which detects the magnetic flux in the iron core.
- Such a configuration is also advantageous in which the first or second amplifier is designed with an adjustable gain coefficient and a capacitor is connected in series at its output.
- the capacitor connected in series ensures the frequency independence of the error compensation.
- the accuracy can be increased even further if the current transformers are provided with a switching system that adjusts the gain coefficient of the current transformer / the current transformers synchronously with the change in the measuring range. This can be done, for example, by switching the feedback resistance of operational amplifiers.
- the active, two-stage current transformer 1 shown in the figure contains a primary coil system 5 and a secondary coil system 6 arranged on a toroidal iron core, an indicator coil 8 and a compensation coil system 9 located on the inside of the iron core 4 (working core), also arranged on a toroidal indicator core 7, and an indicator amplifier 10.
- the primary coil system 5 and the secondary coils System 6 for realizing the measurement range conversion by one coil each with multiple taps.
- the primary coil system 5 or the secondary coil system can be formed by a single coil with two outputs.
- a generator 2, symbolizing the current I 1 to be measured, is connected to the current transformer 1 via terminals K and L.
- the terminal K is connected to one end of the primary coil system 5, while the terminal L corresponds to the set measuring range with one of the terminals L 1 , L 2 .... L n-1 , L n of the primary coil system 5, in the figure with the terminal L 1 , is connected.
- the primary coil system 5 is between the terminals K and L 1 with a section with a number of turns N 11 , between the terminals L 1 and L 2 with a section with a number of turns N 12 , etc. and between the terminals L n-1 and L n is formed with a section with a number of turns N 1n , the turn capacities of the sections corresponding to C 11 , C 12 ... C ln .
- the current transformer 1 is followed by a load impedance 3 with an impedance Z 2 via the terminals k and 1.
- the earthed terminal k is connected to one end of the secondary coil system 6, while the terminal 1 is connected to one of the measuring ranges
- Terminals 1 1 ,, l 2 ... l m -1 , l m of the secondary coil system 6 in the figure to terminal l 1 - is connected.
- the secondary coil system 6 is between the terminals k and 1 1 with a section with a number of turns N 21 , between the terminals l 1 and l 2 with a section with a number of turns N 22 , etc. and between the terminals l m-1 and l m formed with a section with a number of turns N 2m , these sections having corresponding turn capacities C 21 , C 22 ... C 2m .
- a current I ma is added to the current induced in the secondary coil system 6 in a manner known per se.
- the terminal 1 is connected to one of the terminals l 1 'l 2 ' ... l m-1 ', l m ' of the compensation coil system 9 located on the indicator core 7 - in the present exemplary embodiment with the inhibitor l 1 ' , wherein the terminal l 1 'corresponds to the terminal 1 1 of the secondary coil system 6.
- the terminals l 1 ', l 2 '... l m-1 ', l m '- corresponding to the secondary coil system 6 - there are sections with number of turns N 21 , N 22 ... N 2m .
- the mentioned end of the compensation coil system 9 is led to the output of the indicator amplifier 10, at the inputs of which the connections of the indicator coil 8 located on the indicator core 7 are connected with a number of turns N e .
- the compensation coil 11 with a number of turns N c is arranged on the iron core 4 (working core) according to the invention in the illustrated embodiment, the compensation coil 11 Is fed via an amplifier 14 from a signal generator 13, which generates a signal proportional to the rate of change of the magnetic flux ⁇ occurring in the iron core 4.
- the signal transmitter 13 is formed by a detector coil 12 which is arranged on the iron core 4 and is grounded at one of its terminals and has a number of turns N d .
- the signal generator 13 can also be designed in a different way, for example by means of a differential element connected downstream of a flow detector designed with a Hall probe.
- the other terminal of the detector coil 12 is connected to the input of the amplifier 14, this input being connected via a resistor 17 connected in series with a value R 1 to the
- REPLACEMENT LEAF inverting input of an operational amplifier 16 is guided.
- the non-inverting input of the operational amplifier 16 is grounded, while the output of the operational amplifier 16 is connected to the inverting input of the operational amplifier 16 via a resistor 18 with a variable value R 2 and via a resistor 19 with a value R 3 and capacitor 20 connected in series a capacitance C 1 is led to a terminal of the compensation coil 11.
- the other terminal of the compensation coil 11 is grounded. It is advantageous to arrange the earthed compensation coil 11 and the earthed detector coil 12 in the current converter 1 according to the invention in the vicinity of the sector coil system 6, further away from the primary coil system 5. As a result, no additional insulation is required to achieve the prescribed operating voltage.
- the compensation coil 11 according to the invention can be arranged on the indicator core 7 instead of the iron core 4 or on a smoothing core which is known and which may surround the indicator core 7.
- the amplifier 14 can supply the power according to the figure.
- the detector coil 12 not only connects to the amplifier 14, but also to the input of the amplifier 15.
- the input of the amplifier 15 is connected via a series-connected resistor 22 with a value R 4 to the inverting input of an operational amplifier 21, the non-inverting input of which is grounded, while its output is connected to the one via a resistor 23 with a variable value R 5 inverting input, and on the other hand via a
- the sinusoidal current I 1 of the generator 2 excites the section of the primary coil system 5 formed with a number of turns N 11 , whereupon a current is induced in the section of the secondary coil system 6 formed with a number of turns N 21 .
- a current I ma flows through the load impedance 3 if the effect of the winding capacities C 11 ... C 1n , C 21 ... C 2m is disregarded.
- the current I ma is generated in a known manner by the indicator amplifier 10 in such a way that a zero magnetic flux is set in the indator core 7 with good approximation by means of the current I ma forced into the compensation coil system 9. In this way, the error caused by the magnetizing current can practically be eliminated.
- the parasitic excitations can be compensated for by a current I c fed into the compensation coil 11 with a number of turns N c if the following condition is ensured: It is obvious that the current I c at the in the
- Figure embodiment shown can be approximately determined by the following relationship: ⁇ if the value of the control circuit stabilizing against stand 19 is much smaller than the impedance of the capacitor 20, ie By inserting the relationships / 1 /, / 2 / and / 4 / into the relationship / 3 / the following condition is obtained:
- the parasitic excitations resulting from the winding capacitances can be compensated for independently of the frequency.
- the setting is made by changing the value R 2 of the resistor 18.
- a current I z of corresponding magnitude is also forced into the load impedance 3 in order to ensure an even greater independence of the error of the current transformer 1 from the size of the load impedance 3 .
- the magnitude of the current I z can be changed by changing the value R 5 of the Resistor 23 can be set.
- Accuracy can be further increased. This can be implemented, for example, in such a way that the current transformer is provided with a switching system which, together with the change in the measuring range, inserts resistors 18 or 23 with different values into the circuit.
- the error caused by the winding capacitances can be reduced by approximately two orders of magnitude.
- the invention can be used in both passive and active, single and multi-stage current transformers.
- a particular advantage of the invention is that the error caused by the winding capacitances of the primary coil system or secondary coil system can also be compensated for independently of frequency. Another advantage is that the compensation can also be achieved through subsequent expansion of finished current transformers, ie. can be realized by arranging the compensation coil on the iron core 4.
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Transformers For Measuring Instruments (AREA)
- Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)
- Measurement Of Current Or Voltage (AREA)
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE3590658A DE3590658C1 (de) | 1984-12-21 | 1985-12-20 | Verfahren zur Reduzierung des Übertragungsfehlers von Stromwandlern, sowie Praezisionsstromwandler |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
HU481384A HU192656B (en) | 1984-12-21 | 1984-12-21 | Method for decreasing the error of current transformer and high-accuracy current transformer |
HU4813/84 | 1984-12-21 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1986003883A1 true WO1986003883A1 (en) | 1986-07-03 |
Family
ID=10968935
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/HU1985/000079 WO1986003883A1 (en) | 1984-12-21 | 1985-12-20 | Process for reducing the transmission error of current transformers, and precision current transformers |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP0205538A1 (de) |
AT (1) | AT393756B (de) |
CH (1) | CH667939A5 (de) |
DE (1) | DE3590658C1 (de) |
HU (1) | HU192656B (de) |
WO (1) | WO1986003883A1 (de) |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2812303A1 (de) * | 1978-03-21 | 1979-10-04 | Stepper & Co | Eisenlose stromwandleranordnung |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3497793A (en) * | 1966-07-05 | 1970-02-24 | Ind Elettriche Di Legnano Spa | Error compensation apparatus for instrument transformers |
-
1984
- 1984-12-21 HU HU481384A patent/HU192656B/hu not_active IP Right Cessation
-
1985
- 1985-12-20 EP EP19860900231 patent/EP0205538A1/de not_active Withdrawn
- 1985-12-20 WO PCT/HU1985/000079 patent/WO1986003883A1/de active Application Filing
- 1985-12-20 AT AT904685A patent/AT393756B/de not_active IP Right Cessation
- 1985-12-20 CH CH336586A patent/CH667939A5/de not_active IP Right Cessation
- 1985-12-20 DE DE3590658A patent/DE3590658C1/de not_active Expired - Fee Related
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2812303A1 (de) * | 1978-03-21 | 1979-10-04 | Stepper & Co | Eisenlose stromwandleranordnung |
Also Published As
Publication number | Publication date |
---|---|
DE3590658D2 (en) | 1986-11-20 |
EP0205538A1 (de) | 1986-12-30 |
HU192656B (en) | 1987-06-29 |
DE3590658C1 (de) | 1994-04-14 |
ATA904685A (de) | 1991-05-15 |
CH667939A5 (de) | 1988-11-15 |
AT393756B (de) | 1991-12-10 |
HUT38754A (en) | 1986-06-30 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
DE69833953T2 (de) | Selbstgespeister stromfühler | |
DE3880280T2 (de) | Strommessgeraet mit magnetischer kopplung. | |
DE69207223T2 (de) | Vorrichtung zum Messen von Strömen | |
EP0691544A2 (de) | Stromsensor nach dem Kompensationsprinzip | |
DE2835075A1 (de) | Einrichtung zur nachbildung grosser elektrischer lasten in wechselstromsystemen | |
DE19832854C2 (de) | Einrichtung zum Messen linearer Verschiebungen | |
DE3825975C2 (de) | ||
DE3040316C2 (de) | Verfahren und Vorrichtung zur kontaktlosen Messung von Gleich- und Wechselströmen, insbesondere von Strom-Augenblickswerten | |
DE2812303C2 (de) | Stromwandleranordnung mit elektronischer Fehlerkompensation | |
DE3403855C2 (de) | Meßspannungswandler hoher Genauigkeit | |
AT393756B (de) | Verfahren zur reduzierung des uebertragungsfehlers von stromwandlern, sowie praezisionsstromwandler | |
EP0053581B1 (de) | Fehlerkompensierter Spannungswandler für Hochspannung | |
WO2000017663A2 (de) | Verfahren zur abbildung von gleichströmen und gleichstromwandler zur durchführung des verfahrens | |
EP0029903B1 (de) | Messanordnung für elektrische Ströme | |
DE3435267C2 (de) | Strommeßeinrichtung | |
DE3918100C2 (de) | ||
DE3443460C2 (de) | ||
DE4030797C1 (en) | Heavy current measuring by shunt resistor - passes current over two-region resistor, with identical inductivity, but different resistance per region | |
CH658520A5 (de) | Schaltungsanordnung zur speisung eines messgroessenumformers. | |
DE3822051C2 (de) | ||
DE3149992C2 (de) | ||
DE527676C (de) | Vorrichtung zur Messung elektrischer Groessen und ihrer Summen am fernen Ort mit Hilfe von Wechselstrom | |
DE973734C (de) | Verstaerker fuer einen Fluessigkeitsmesser | |
DE2422436A1 (de) | Schaltung zur erhoehung der impedanz von wicklungen mit 2 kernen aus weichmagnetischem werkstoff | |
DE1264604B (de) | Wechselstromkomparator |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AK | Designated states |
Kind code of ref document: A1 Designated state(s): AT CH DE GB JP US |
|
AL | Designated countries for regional patents |
Kind code of ref document: A1 Designated state(s): AT BE CH DE FR GB IT LU NL SE |
|
ENP | Entry into the national phase in: |
Ref document number: 1985 9046 Country of ref document: AT Date of ref document: 19860703 Kind code of ref document: A |
|
REF | Corresponds to |
Ref document number: 3590658 Country of ref document: DE Date of ref document: 19861120 |
|
WWE | Wipo information: entry into national phase |
Ref document number: 3590658 Country of ref document: DE |