CA2104585A1 - Current transformer - Google Patents
Current transformerInfo
- Publication number
- CA2104585A1 CA2104585A1 CA002104585A CA2104585A CA2104585A1 CA 2104585 A1 CA2104585 A1 CA 2104585A1 CA 002104585 A CA002104585 A CA 002104585A CA 2104585 A CA2104585 A CA 2104585A CA 2104585 A1 CA2104585 A1 CA 2104585A1
- Authority
- CA
- Canada
- Prior art keywords
- secondary winding
- winding
- current transformer
- annular core
- metal casing
- 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.)
- Abandoned
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
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02B—BOARDS, SUBSTATIONS OR SWITCHING ARRANGEMENTS FOR THE SUPPLY OR DISTRIBUTION OF ELECTRIC POWER
- H02B13/00—Arrangement of switchgear in which switches are enclosed in, or structurally associated with, a casing, e.g. cubicle
- H02B13/02—Arrangement of switchgear in which switches are enclosed in, or structurally associated with, a casing, e.g. cubicle with metal casing
- H02B13/035—Gas-insulated switchgear
- H02B13/0356—Mounting of monitoring devices, e.g. current transformers
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Transformers For Measuring Instruments (AREA)
- Regulation Of General Use Transformers (AREA)
- Emergency Protection Circuit Devices (AREA)
- Diaphragms For Electromechanical Transducers (AREA)
- Control Of Eletrric Generators (AREA)
- Amplifiers (AREA)
Abstract
Abstract of the disclosure 1. Current transformer 2.1. The object is to provide a current transformer which can be installed in a grounded metal casing sur-rounding a high voltage conductor, having an annular core and a secondary winding surrounding the annular core in a toroidal configuration, in which the current trans-former is to be protected by means of structurally simple measures against overvoltages at the secondary winding due to switching operations.
2.2. In addition to the secondary winding (5) of the current transformer (2) there is provided a further winding (9), which is conductively connected at one end to ground potential. The secondary winding (5) is screened by the further winding (9). Moreover, as a result of the grounded further winding (9), the total capacitance between the secondary winding (5) and the metal casing (1) is increased. The capacitance conditions of the capacitive voltage divider formed by the high voltage conductor (3), the secondary winding (5) and the metal casing (1) are designed thereby so that the second-ary winding (5) is protected against overvoltages due to switching operations.
2.3. The invention can be used in current transformers for encased switchboard plants.
3. FIG 2
2.2. In addition to the secondary winding (5) of the current transformer (2) there is provided a further winding (9), which is conductively connected at one end to ground potential. The secondary winding (5) is screened by the further winding (9). Moreover, as a result of the grounded further winding (9), the total capacitance between the secondary winding (5) and the metal casing (1) is increased. The capacitance conditions of the capacitive voltage divider formed by the high voltage conductor (3), the secondary winding (5) and the metal casing (1) are designed thereby so that the second-ary winding (5) is protected against overvoltages due to switching operations.
2.3. The invention can be used in current transformers for encased switchboard plants.
3. FIG 2
Description
Siemens Aktiengesellschaft Gr 91P4007 Current transformer The invention relates to a current tran~former which can be installed in a grounded metal casing sur-S rounding a high voltage conductor, having an annular coreand a secondary winding surrounding the annular core in a toroidal configuration.
Such a current transformer is disclosed in EP-0,063,636 Bl. The current transformer described therein is protected by an internal tube electrically conductively connected at one of its ends with the casing and a screening body, which is conductively connected with the casing at tha~ side of the annular core which is remote from the internal tube and overlaps with the ~ube in electrically insulated fashion~ again~t overvoltages at the secondary terminals. Such overvoltages may occur if the high voltage conductor i~ exposed to rapid current changes and voltage changes for example within a switch-ing system in the course of connection and di~connection operations. In the~e circumstance~, transverse electro-magnetic traveling waves pass between the high voltage conductor and the me~al ca~ing in the longitudinal direction of ~he high voltage conductor. Any traveling wave~ which are present can continue to pass virtually unhindered, without reflsctiont via the relatively large capacitance formed between the internal tube and ~he ~creening body on account of ~he overlapping, without generating a substantial increass in the potential of the secondary winding.
The object of the pre~ent in~ention i~ to protect a current tran~former of tha initially mentioned type by means of ~tructurally ~imple measures, again~t overvolt-~ges at the ~econdary winding in consequence of 3witching operation~.
According to the invention, the ob~ect i9 achieved in tha~ on at least a par~ of ~he annular core a furth~r winding is fitted, which i5 conductively ..
:
.
.
,, ~ . -.
3r~
connected to ground potential by one end.
In terms of cicuitry, the electrical capacitance between the secondary winding and the grounded further winding i~ situated in parallel with the stray capaci-tance between the secondary willding and the groundedmetal casing. A~ a result of thi~, the total capacitance of the secondary winding in relation to the metal casing is increa~ed.
In general, the capacitance between the high voltage conductor and the secondary winding of the current transformer represents, togethex with the capaci-tance of the secondary winding in relation to the grounded metal casing, a capacitive voltage divider, the undervoltage capacitor of which is formed by the second-ary winding and ~he metal casing. By means of an increasein the capacitance of thi~ undervoltage capacitor by mean~ of the grounded further winding, according to the invention the secondary winding i~ held at a low voltage level upon the occurrence o~ traveling wave~ at the high voltage conductor. As a result of this, an overvoltage at the secondary windin~ is avoided even in the case of rapid current and voltage changes occurring at the high voltag0 conductor.
The further winding can be dasigned so that it cover~ ~he entire annular core or at least substantial part~ of the annular core. In thi ca~e, however, those parts o~ the further winding which ara furthest distant from the grounded end are connected, with respect to high frequency voltage changes, substantially via the ~elf-inductance of the windi~g itsel~ with ground poten-tial. In the case of high-frequency voltage changes, the component of the capacita~ca of these winding part remots from the ground~d end with respect to -the ~econd-ary winding contributes only in part to the total capacitance.
In this connection, it proves to be advantageouæ
that additional winding~ are fitted on in each instance one part of the annular core and are conductively conn0c~ed to ground po~ential ~y in each instance one end.
.
Such a current transformer is disclosed in EP-0,063,636 Bl. The current transformer described therein is protected by an internal tube electrically conductively connected at one of its ends with the casing and a screening body, which is conductively connected with the casing at tha~ side of the annular core which is remote from the internal tube and overlaps with the ~ube in electrically insulated fashion~ again~t overvoltages at the secondary terminals. Such overvoltages may occur if the high voltage conductor i~ exposed to rapid current changes and voltage changes for example within a switch-ing system in the course of connection and di~connection operations. In the~e circumstance~, transverse electro-magnetic traveling waves pass between the high voltage conductor and the me~al ca~ing in the longitudinal direction of ~he high voltage conductor. Any traveling wave~ which are present can continue to pass virtually unhindered, without reflsctiont via the relatively large capacitance formed between the internal tube and ~he ~creening body on account of ~he overlapping, without generating a substantial increass in the potential of the secondary winding.
The object of the pre~ent in~ention i~ to protect a current tran~former of tha initially mentioned type by means of ~tructurally ~imple measures, again~t overvolt-~ges at the ~econdary winding in consequence of 3witching operation~.
According to the invention, the ob~ect i9 achieved in tha~ on at least a par~ of ~he annular core a furth~r winding is fitted, which i5 conductively ..
:
.
.
,, ~ . -.
3r~
connected to ground potential by one end.
In terms of cicuitry, the electrical capacitance between the secondary winding and the grounded further winding i~ situated in parallel with the stray capaci-tance between the secondary willding and the groundedmetal casing. A~ a result of thi~, the total capacitance of the secondary winding in relation to the metal casing is increa~ed.
In general, the capacitance between the high voltage conductor and the secondary winding of the current transformer represents, togethex with the capaci-tance of the secondary winding in relation to the grounded metal casing, a capacitive voltage divider, the undervoltage capacitor of which is formed by the second-ary winding and ~he metal casing. By means of an increasein the capacitance of thi~ undervoltage capacitor by mean~ of the grounded further winding, according to the invention the secondary winding i~ held at a low voltage level upon the occurrence o~ traveling wave~ at the high voltage conductor. As a result of this, an overvoltage at the secondary windin~ is avoided even in the case of rapid current and voltage changes occurring at the high voltag0 conductor.
The further winding can be dasigned so that it cover~ ~he entire annular core or at least substantial part~ of the annular core. In thi ca~e, however, those parts o~ the further winding which ara furthest distant from the grounded end are connected, with respect to high frequency voltage changes, substantially via the ~elf-inductance of the windi~g itsel~ with ground poten-tial. In the case of high-frequency voltage changes, the component of the capacita~ca of these winding part remots from the ground~d end with respect to -the ~econd-ary winding contributes only in part to the total capacitance.
In this connection, it proves to be advantageouæ
that additional winding~ are fitted on in each instance one part of the annular core and are conductively conn0c~ed to ground po~ential ~y in each instance one end.
.
2 ll ~ ~ ~ 3 ~
As a result of the fact that additional windings are fitted onto the annular core, the capacitance between ~he secondary winding and the grounded metal casing is increased. Thus, the voltage increases occurring in the event of rapid voltage changes on the high voltage conductor are kept low at the secondary winding. The fitting of a plurality of additional windings onto the annular core has the advantage that each one of the additional windings can be conductively connected directly to ground potential; in this case, the direct conductive connection to ground potential exhibits a low self inductance. As a result o this, even at high frequencie~ an effective connection between the additional windings and ground potential is present.
A further advantageou~ refinement of the inven-tion provides that the further windiny and the additional windings ~urround the secondary winding.
As a result of this arrangement of the further winding and the additional winding~, a screening of the secondary winding from the electric field surrounding the high ~oltage conductor is present. As a result of this, the influences of the electric field on the secondary winding can be kept at a particularly low level.
The invention i~ advantageou~ly further refined in that the annular core is conductively connected at one place to ground potential, A8 a result of thi~, the capacitance betw~en the secondary winding and the annular core is connected in parallel, in terms of cicuitry, with the capacitance between the secondary winding and the metal ca~ing. This leads to an increase in the total capacitance between the secondary winding and the metal casing.
In ~he text which follows, ~he in~ention is shown - in a dra~ing with reference to an illustrative embodiment and is then described.
In the drawing:
Figure 1 shows a metal casing with a current transformer and a high vol~age conduc~or, diagr~mma~ically in longitudinal section, ~ .
:
.
: . .. :. . ' ' _ 4 _ 2~
Figure 2 shows a semisection thro~gh the current txans-former with a diagrammatic representation of the seconda~y winding and th further winding, Figure 3 shows the annular core of a current transform0r S accoxding to the invention, with a plurality of additional winding~.
Figure 1 diagrammatically shows the metal cas-ing 1, into which a current transformer 2 is inserted, which transformPr ~urrounds a high volt.age conductor 3.
The current transformer 2 compri~es a plurality of annular cores 4, onto which at least one secondary winding 5 is fitted, which, to mea ure the current flowing in the high voltage conductox 3, îs connectecl to an electronic measuring arrangement (not shown). The secondary winding 5 iB fitted onto the annular cores 4, in an insulated fashion in each instance.
The annular core~ 4 ar~ Ycreened in relation to the high voltage conductor 3 by an electrode 6. The electrode 6 is electrically conductively connected at one end 7 with the metal casing 1. The other end 8 of the electrode 6 must not be conductively connected to th~
metal casing 1, ~ince otherwise a short circuit conduct-ive loop would be creatPd around the ~nnular cores 4, which loop would make the current transformer 2 unusable for the measurement of a current flowing in the high voltage conductor 3.
Rapid voltage and curren~ increases which occur at the high voltage conductor 3 pass along ~he high vol~age conductor 3 between ~he latter and the metal casing 1 a~ electromagnetic tra~eling waves. Such travel-ing wave~ also penetrate the space of the metal casing 1, which space is separated of by the electrode 6 and in which ~pace the annular cores 4 are situated.
In general, such a traveling wave can generate in the secondary winding 5 of the current tran~former 2 an overvoltage a~ a result of which the measuring apparatu~
connected tv the secondary winding 5 can be damayed. To prev~nt the occurrence o~ such overvoltages, according to $he invention there are fitted onto each annular core 4~
.' ' -- ' .
. .
.
- 5 '~
in addition to the secondary winding 5, a further wind-ing 9 and a plurality of additional windin~ 10 for the screening of the secondary winding 5, as shown in Fig-ure 2. The further winding 9 and the additional wind-ing~ 10 are grounded in each instance at one end andinsulated in relation to one another and in relation to the secondary winding 5 by insulating layers 12. Between the secondary winding 5 and the remaining windings 9, 10, there i~ a high electrical capacitance. This capacitance is electrically connected in paralle:L with the stray capacitance between the secondary winding 5 and the metal casing 1~
In addition, the ~nnular cores 4 themselves may also be connected to ground potential in each instance at one place via an electrically conductive connection 11.
A~ a result of this, the capacitance between the second-ary winding 5 and each one of the annular cores 4 is also connec~ed in parallel with the stray capacitance between the secondary winding and the metal casing 1.
Figure 3 shows, in a perspectivQ elevation, an annular core 4 with a further winding 9 and additional win~ings lQ, which are distributed at the periphery of the annular core 4. Each one of the aforementioned windin~g 9~ 10 is connected to greund potential at one end. The other end of the windings remains in each instance unconnected and is additionally insulated to avoid needle discharges. For rea~on~ of ~implicity, the secondary winding i~ not shown in Figure 3.
' . . .
' ~ . ,:
. . .
, ,, , ., - : : : : ' , List of refer~nce symbols ~ ~ 4~ 91P4007 1 = metal casing 2 = current transformer 3 = high voltage conductor 4 = annular core 5 - secondary winding 6 = electrode 7 - one end of the electrode 6 8 = other end of the electrode 6 9 = winding 10 = winding 11 = connection 12 = insulating layex
As a result of the fact that additional windings are fitted onto the annular core, the capacitance between ~he secondary winding and the grounded metal casing is increased. Thus, the voltage increases occurring in the event of rapid voltage changes on the high voltage conductor are kept low at the secondary winding. The fitting of a plurality of additional windings onto the annular core has the advantage that each one of the additional windings can be conductively connected directly to ground potential; in this case, the direct conductive connection to ground potential exhibits a low self inductance. As a result o this, even at high frequencie~ an effective connection between the additional windings and ground potential is present.
A further advantageou~ refinement of the inven-tion provides that the further windiny and the additional windings ~urround the secondary winding.
As a result of this arrangement of the further winding and the additional winding~, a screening of the secondary winding from the electric field surrounding the high ~oltage conductor is present. As a result of this, the influences of the electric field on the secondary winding can be kept at a particularly low level.
The invention i~ advantageou~ly further refined in that the annular core is conductively connected at one place to ground potential, A8 a result of thi~, the capacitance betw~en the secondary winding and the annular core is connected in parallel, in terms of cicuitry, with the capacitance between the secondary winding and the metal ca~ing. This leads to an increase in the total capacitance between the secondary winding and the metal casing.
In ~he text which follows, ~he in~ention is shown - in a dra~ing with reference to an illustrative embodiment and is then described.
In the drawing:
Figure 1 shows a metal casing with a current transformer and a high vol~age conduc~or, diagr~mma~ically in longitudinal section, ~ .
:
.
: . .. :. . ' ' _ 4 _ 2~
Figure 2 shows a semisection thro~gh the current txans-former with a diagrammatic representation of the seconda~y winding and th further winding, Figure 3 shows the annular core of a current transform0r S accoxding to the invention, with a plurality of additional winding~.
Figure 1 diagrammatically shows the metal cas-ing 1, into which a current transformer 2 is inserted, which transformPr ~urrounds a high volt.age conductor 3.
The current transformer 2 compri~es a plurality of annular cores 4, onto which at least one secondary winding 5 is fitted, which, to mea ure the current flowing in the high voltage conductox 3, îs connectecl to an electronic measuring arrangement (not shown). The secondary winding 5 iB fitted onto the annular cores 4, in an insulated fashion in each instance.
The annular core~ 4 ar~ Ycreened in relation to the high voltage conductor 3 by an electrode 6. The electrode 6 is electrically conductively connected at one end 7 with the metal casing 1. The other end 8 of the electrode 6 must not be conductively connected to th~
metal casing 1, ~ince otherwise a short circuit conduct-ive loop would be creatPd around the ~nnular cores 4, which loop would make the current transformer 2 unusable for the measurement of a current flowing in the high voltage conductor 3.
Rapid voltage and curren~ increases which occur at the high voltage conductor 3 pass along ~he high vol~age conductor 3 between ~he latter and the metal casing 1 a~ electromagnetic tra~eling waves. Such travel-ing wave~ also penetrate the space of the metal casing 1, which space is separated of by the electrode 6 and in which ~pace the annular cores 4 are situated.
In general, such a traveling wave can generate in the secondary winding 5 of the current tran~former 2 an overvoltage a~ a result of which the measuring apparatu~
connected tv the secondary winding 5 can be damayed. To prev~nt the occurrence o~ such overvoltages, according to $he invention there are fitted onto each annular core 4~
.' ' -- ' .
. .
.
- 5 '~
in addition to the secondary winding 5, a further wind-ing 9 and a plurality of additional windin~ 10 for the screening of the secondary winding 5, as shown in Fig-ure 2. The further winding 9 and the additional wind-ing~ 10 are grounded in each instance at one end andinsulated in relation to one another and in relation to the secondary winding 5 by insulating layers 12. Between the secondary winding 5 and the remaining windings 9, 10, there i~ a high electrical capacitance. This capacitance is electrically connected in paralle:L with the stray capacitance between the secondary winding 5 and the metal casing 1~
In addition, the ~nnular cores 4 themselves may also be connected to ground potential in each instance at one place via an electrically conductive connection 11.
A~ a result of this, the capacitance between the second-ary winding 5 and each one of the annular cores 4 is also connec~ed in parallel with the stray capacitance between the secondary winding and the metal casing 1.
Figure 3 shows, in a perspectivQ elevation, an annular core 4 with a further winding 9 and additional win~ings lQ, which are distributed at the periphery of the annular core 4. Each one of the aforementioned windin~g 9~ 10 is connected to greund potential at one end. The other end of the windings remains in each instance unconnected and is additionally insulated to avoid needle discharges. For rea~on~ of ~implicity, the secondary winding i~ not shown in Figure 3.
' . . .
' ~ . ,:
. . .
, ,, , ., - : : : : ' , List of refer~nce symbols ~ ~ 4~ 91P4007 1 = metal casing 2 = current transformer 3 = high voltage conductor 4 = annular core 5 - secondary winding 6 = electrode 7 - one end of the electrode 6 8 = other end of the electrode 6 9 = winding 10 = winding 11 = connection 12 = insulating layex
Claims (4)
1. A current transformer which can be installed in a grounded metal casing surrounding a high voltage conductor, having an annular core and a secondary winding surrounding the annular core in a toroidal configuration, characterized in that on at least a part of the annular core (4) a further winding (9) is fitted, which is conductively connected to ground potential by one end.
2. The current transformer as claimed in claim 1, characterized in that additional windings (10) are fitted on in each instance one part of the annular core (4) and are conductively connected to ground potential by in each instance one end.
3. The current transformer as claimed in claim 1 or 2, characterized in that the further winding (9) and the additional windings (10) surround the secondary winding (5).
4. The current transformer as claimed in claim 1 or one of the following claims, characterized in that the annular core (4) is conductively connected at one place to ground potential.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4106034A DE4106034A1 (en) | 1991-02-22 | 1991-02-22 | POWER CONVERTER |
| DEP4106034.2 | 1991-02-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2104585A1 true CA2104585A1 (en) | 1992-08-23 |
Family
ID=6425930
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002104585A Abandoned CA2104585A1 (en) | 1991-02-22 | 1992-01-24 | Current transformer |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0572427B1 (en) |
| JP (1) | JPH06505125A (en) |
| AT (1) | ATE114384T1 (en) |
| CA (1) | CA2104585A1 (en) |
| DE (2) | DE4106034A1 (en) |
| WO (1) | WO1992015104A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4229680A1 (en) * | 1992-09-02 | 1994-03-03 | Siemens Ag | Power converter |
| DE9217807U1 (en) * | 1992-12-24 | 1993-04-08 | Kommanditgesellschaft Ritz Messwandler GmbH & Co, 20251 Hamburg | Toroidal current transformer |
| ATE151195T1 (en) | 1994-02-17 | 1997-04-15 | Gec Alsthom T & D Ag | TORING CORE CURRENT TRANSFORMER FOR INSTALLATION IN A METAL-ENCAPSULED HIGH-VOLTAGE SWITCHGEAR |
| DE102005007334B4 (en) * | 2005-02-17 | 2007-02-08 | Siemens Ag | Summation current transformer for the universal current-sensitive detection of an electrical differential current |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE683018C (en) * | 1936-08-21 | 1939-10-27 | Stalturbine G M B H | Single-wire current transformer with two-part bushing insulator |
| DE2325441C2 (en) * | 1973-05-17 | 1989-07-20 | Siemens AG, 1000 Berlin und 8000 München | Measuring transducer for installation in a metal capsule of a switchgear system |
| ATE9629T1 (en) * | 1981-04-28 | 1984-10-15 | Sprecher + Schuh Ag | TOROIDAL CURRENT TRANSFORMER FOR INSTALLATION IN A METAL ENCLOSED HIGH VOLTAGE SWITCHGEAR. |
-
1991
- 1991-02-22 DE DE4106034A patent/DE4106034A1/en not_active Withdrawn
-
1992
- 1992-01-24 EP EP92903057A patent/EP0572427B1/en not_active Expired - Lifetime
- 1992-01-24 JP JP4503013A patent/JPH06505125A/en active Pending
- 1992-01-24 DE DE59200812T patent/DE59200812D1/en not_active Expired - Fee Related
- 1992-01-24 AT AT92903057T patent/ATE114384T1/en not_active IP Right Cessation
- 1992-01-24 WO PCT/DE1992/000051 patent/WO1992015104A1/en active IP Right Grant
- 1992-01-24 CA CA002104585A patent/CA2104585A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| DE59200812D1 (en) | 1995-01-05 |
| DE4106034A1 (en) | 1992-08-27 |
| JPH06505125A (en) | 1994-06-09 |
| EP0572427A1 (en) | 1993-12-08 |
| WO1992015104A1 (en) | 1992-09-03 |
| ATE114384T1 (en) | 1994-12-15 |
| EP0572427B1 (en) | 1994-11-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |