CA2039550A1 - Protective relay of a medium voltage electrical mains system - Google Patents
Protective relay of a medium voltage electrical mains systemInfo
- Publication number
- CA2039550A1 CA2039550A1 CA 2039550 CA2039550A CA2039550A1 CA 2039550 A1 CA2039550 A1 CA 2039550A1 CA 2039550 CA2039550 CA 2039550 CA 2039550 A CA2039550 A CA 2039550A CA 2039550 A1 CA2039550 A1 CA 2039550A1
- Authority
- CA
- Canada
- Prior art keywords
- transformer
- relay
- relay according
- input
- mains system
- 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
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
Abstract
ABSTRACT
PROTECTIVE RELAY OF A MEDIUM VOLTAGE ELECTRICAL MAINS SYSTEM
The primary windings of input reducer transformers of a protective relay of a medium voltage electrical mains system are shielded by means of a non-magnetic shielding so as to protect the electronic processing unit of the relay against electro-magnetic disturbances.
PROTECTIVE RELAY OF A MEDIUM VOLTAGE ELECTRICAL MAINS SYSTEM
The primary windings of input reducer transformers of a protective relay of a medium voltage electrical mains system are shielded by means of a non-magnetic shielding so as to protect the electronic processing unit of the relay against electro-magnetic disturbances.
Description
PROTECTIVE RELAY OF A MEDIUM VOLTAGE ELECTRICAL MAINS SYSTEM
. ,. _ _ ' BACKGROUND OF_THE INVENTION
The invention relates to a protective relay of a medium voltage electrical mains system, located in a case comprising at least one conducting part, and comprising inputs to which analog input signals representative of electrical parameters of said mains system are applied, an electronic processing unit of the input signals and a reducer transformer, assoclated with each input, comprising a primary winding connected to said input and a secondary winding connected to the electronic processing unit.
The electronic circuitry, and more particularly -the digital electronic circuitry is very sensitive to variations of electro-magnetic fields produced by a medium voltage environment. The introduction of electronic trip devices, notahly microprocessor-based trip devices, for protection of medium voltage electrical mains systems, gives rise to problems due to the influence of electromagnetic disturhances on the electronic circuitry of the trip device.
SWMMARY OF THE INVENTION
_ The object of the invention is to limit these disturbances with simple, inexpensive means occupying little space.
According to the invention this objective is achieved by the fact that the primary winding of a reducer -transformer, formed by a conductor connecting two terminals of the associated input, is shielded by a non-magnetic material, said shielding heing connected at its two ends to a grounded conducting part of the case.
This shielding, formed preferably by a braided strip made of non-magnetic material, constitutes a very inexpensive Faraday cage of small size, limiting the electromagnetic disturbances, by capacitive coupling, and the disturbances due to the low frequency magnetic ~ield liable to affect the electronic processing unit.
According to a preferred embodiment said conducting part, which is for example metallic, is formed by an external wall of the case on which said inputs are arranged.
The primary windings of all the reducer transformers of the relay, whether they be current or voltage transformers, can be shielded. It is however possible to limit the shielding to the primary windings of the current transformers while still obtaining satisfactory results.
BRI~F DESCRIPTION_OF THE DRAWINGS
:
Other advantages and features will bec:ome more clearly apparent from the following description of an lllustrative embodiment of --the invention, given as a non-restrictive example only and represented in the accompanying drawings, in which :
Figure 1 is a schematic representation of a relay according to the invention;
Figures 2 and 3 respectively illustrate a current signal input and a voltage signal input.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In figure 1, a relay designed to protect a medium voltage three-phase electrical mains system, comprising three phase conductors 1, 2 and 3, comprises an electronic trip device ~.
3 ~ } ~
The trip device 4 is located in a case 5 one external conductlng wall 6 of which ls grounded. The wall 6 is a metal wall but can be formed by a wall made of plastic material charged with a conducting material or covered with a metallic paint.
Analog input signals, respectively representing the currents Il, I2, I3 flowing in the conductors and voltages Vl, V2, V3 of the mains system conductors, are applied to inputs of the trip device. An inpllt signal of the current Il, I2, or I3 is obtained conventionally by means of a current transformer 7 whose primary winding is formed by the conductor involved and whose secondary winding is grounded by one end and connected to a first terminal 8 of the associated input by the other end. The second current input terminals 9 are all grounded. Likewise, a voltage input signal Vl, V2, V3 is obtained by means of a voltage transformer 26 whose winding is connected at one end to the conductor involved and is gxounded at the other end. The secondary of the transformer 26 is connected at one end to the terminals 10 for Vl and V3 and to the terminals 11 for V2, the other end of the secondary of the transformer 26 being grounded.
The input terminals 8, 9, 10, 11 are preferably located on the external metal wall 6 of the case.
The inp~t currents and voltages are too high to be processed directly by the electronic processing unit 12 of the trip device. To give a non-restrictive example, the current signals generally have an intensity in the order o~ a few amps, typically 1 to 5A, whereas the voltage signals can be in the order of a hundred volts. A reducer transformer is therefore connected between each input and the electronic processing unit.
Current reducer transformers 13 are associated with the current inputs 8, 9, whereas voltage reducer transformers 14 are associated with the voltage inputs 10, 11.
.. : ~ , : ', , .
The primary winding 15 of a current reducer transformer 13, connected to the terminals 8 and 9 of the associated input, is shielded over its whole length by a shielding 16 made of non-magnetic material, preferably formed by a braided strip, as a non-restrictive example, a tinned copper strip. The two ends of the shielding are connected to the grounded metal wall 6 by any suitable means, for example by means of a self-tapping screw or a nut and bolt system. Figure 2 illustrates in greater detail the shielded conductor 15, 16 passing through the toroidal core 17 of the current transformer. The secondary winding 18 of th transformer 13 is connected to a shaping circuit 19 whose output is connected to an input of the electronic processing unit 12.
In the embodiment represented in figure 2, the primary 15 of the current transformer 13 forms a single turn passing through the toroid 17. Naturally if the input current is lower, the primary 15 can comprise several turns.
Likewise, the primary winding 20 of a voltage reducer transformer 14, connected to the terminals 10 and 11, is shielded by a shielding 21 made of non-magnetic material.
According to a preferred embodiment represented in figure 3, only the part of the primary winding 20 going from the input terminals 10 or 11 to the beginning of the winding on the transformer core is shielded. The turns are not shielded and the shielding 21 is connected, by any suitable means, to both the metal wall 6 and to a grounded insulating electrical shield 22 separating the primary 20 and secondary 23 windings. The relative dimensions of the shielded part of the conductor 20 and of the non-shielded part must be such that the shielding nevertheless forms a Faraday cage. To serve as an example, this type of shielding is sufficient in practice, for a voltage transformer 14 in which the transverse dimension covered by turns is in the order of one centimeter, whereas the length of the conductor going from the input terminals 10 or 11 to the part forming the turns is in the order of ten centimeters.
The secondary winding 23 of the transformer 14 is connected to the electronic processing unit 12 by means of a shaping circuit 24.
The shielding according to the invention is more particularly suitable in the case of a trip device 4 whose electronic processing unit comprises a microprocessor, the analog input signals being multiplexed then transformed into digital signals before being processed by the microprocessor.
The electronic processing unit 12 notably performs protection functions and can transmit tripping and closing orders to a trip relay represented in schematic form by 25 in figure 1.
:
' : ::......... . .
. ,. _ _ ' BACKGROUND OF_THE INVENTION
The invention relates to a protective relay of a medium voltage electrical mains system, located in a case comprising at least one conducting part, and comprising inputs to which analog input signals representative of electrical parameters of said mains system are applied, an electronic processing unit of the input signals and a reducer transformer, assoclated with each input, comprising a primary winding connected to said input and a secondary winding connected to the electronic processing unit.
The electronic circuitry, and more particularly -the digital electronic circuitry is very sensitive to variations of electro-magnetic fields produced by a medium voltage environment. The introduction of electronic trip devices, notahly microprocessor-based trip devices, for protection of medium voltage electrical mains systems, gives rise to problems due to the influence of electromagnetic disturhances on the electronic circuitry of the trip device.
SWMMARY OF THE INVENTION
_ The object of the invention is to limit these disturbances with simple, inexpensive means occupying little space.
According to the invention this objective is achieved by the fact that the primary winding of a reducer -transformer, formed by a conductor connecting two terminals of the associated input, is shielded by a non-magnetic material, said shielding heing connected at its two ends to a grounded conducting part of the case.
This shielding, formed preferably by a braided strip made of non-magnetic material, constitutes a very inexpensive Faraday cage of small size, limiting the electromagnetic disturbances, by capacitive coupling, and the disturbances due to the low frequency magnetic ~ield liable to affect the electronic processing unit.
According to a preferred embodiment said conducting part, which is for example metallic, is formed by an external wall of the case on which said inputs are arranged.
The primary windings of all the reducer transformers of the relay, whether they be current or voltage transformers, can be shielded. It is however possible to limit the shielding to the primary windings of the current transformers while still obtaining satisfactory results.
BRI~F DESCRIPTION_OF THE DRAWINGS
:
Other advantages and features will bec:ome more clearly apparent from the following description of an lllustrative embodiment of --the invention, given as a non-restrictive example only and represented in the accompanying drawings, in which :
Figure 1 is a schematic representation of a relay according to the invention;
Figures 2 and 3 respectively illustrate a current signal input and a voltage signal input.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In figure 1, a relay designed to protect a medium voltage three-phase electrical mains system, comprising three phase conductors 1, 2 and 3, comprises an electronic trip device ~.
3 ~ } ~
The trip device 4 is located in a case 5 one external conductlng wall 6 of which ls grounded. The wall 6 is a metal wall but can be formed by a wall made of plastic material charged with a conducting material or covered with a metallic paint.
Analog input signals, respectively representing the currents Il, I2, I3 flowing in the conductors and voltages Vl, V2, V3 of the mains system conductors, are applied to inputs of the trip device. An inpllt signal of the current Il, I2, or I3 is obtained conventionally by means of a current transformer 7 whose primary winding is formed by the conductor involved and whose secondary winding is grounded by one end and connected to a first terminal 8 of the associated input by the other end. The second current input terminals 9 are all grounded. Likewise, a voltage input signal Vl, V2, V3 is obtained by means of a voltage transformer 26 whose winding is connected at one end to the conductor involved and is gxounded at the other end. The secondary of the transformer 26 is connected at one end to the terminals 10 for Vl and V3 and to the terminals 11 for V2, the other end of the secondary of the transformer 26 being grounded.
The input terminals 8, 9, 10, 11 are preferably located on the external metal wall 6 of the case.
The inp~t currents and voltages are too high to be processed directly by the electronic processing unit 12 of the trip device. To give a non-restrictive example, the current signals generally have an intensity in the order o~ a few amps, typically 1 to 5A, whereas the voltage signals can be in the order of a hundred volts. A reducer transformer is therefore connected between each input and the electronic processing unit.
Current reducer transformers 13 are associated with the current inputs 8, 9, whereas voltage reducer transformers 14 are associated with the voltage inputs 10, 11.
.. : ~ , : ', , .
The primary winding 15 of a current reducer transformer 13, connected to the terminals 8 and 9 of the associated input, is shielded over its whole length by a shielding 16 made of non-magnetic material, preferably formed by a braided strip, as a non-restrictive example, a tinned copper strip. The two ends of the shielding are connected to the grounded metal wall 6 by any suitable means, for example by means of a self-tapping screw or a nut and bolt system. Figure 2 illustrates in greater detail the shielded conductor 15, 16 passing through the toroidal core 17 of the current transformer. The secondary winding 18 of th transformer 13 is connected to a shaping circuit 19 whose output is connected to an input of the electronic processing unit 12.
In the embodiment represented in figure 2, the primary 15 of the current transformer 13 forms a single turn passing through the toroid 17. Naturally if the input current is lower, the primary 15 can comprise several turns.
Likewise, the primary winding 20 of a voltage reducer transformer 14, connected to the terminals 10 and 11, is shielded by a shielding 21 made of non-magnetic material.
According to a preferred embodiment represented in figure 3, only the part of the primary winding 20 going from the input terminals 10 or 11 to the beginning of the winding on the transformer core is shielded. The turns are not shielded and the shielding 21 is connected, by any suitable means, to both the metal wall 6 and to a grounded insulating electrical shield 22 separating the primary 20 and secondary 23 windings. The relative dimensions of the shielded part of the conductor 20 and of the non-shielded part must be such that the shielding nevertheless forms a Faraday cage. To serve as an example, this type of shielding is sufficient in practice, for a voltage transformer 14 in which the transverse dimension covered by turns is in the order of one centimeter, whereas the length of the conductor going from the input terminals 10 or 11 to the part forming the turns is in the order of ten centimeters.
The secondary winding 23 of the transformer 14 is connected to the electronic processing unit 12 by means of a shaping circuit 24.
The shielding according to the invention is more particularly suitable in the case of a trip device 4 whose electronic processing unit comprises a microprocessor, the analog input signals being multiplexed then transformed into digital signals before being processed by the microprocessor.
The electronic processing unit 12 notably performs protection functions and can transmit tripping and closing orders to a trip relay represented in schematic form by 25 in figure 1.
:
' : ::......... . .
Claims (9)
1. A protective relay of a medium voltage electrical mains system, this relay being located in a case comprising at least one conducting part, this relay comprising inputs to which analog input signals representative of electrical parameters of said mains system are applied, an electronic processing unit of the input signals and a reducer transformer, associated with each input, comprising a primary winding connected to said input and a secondary winding connected to the electronic processing unit, the primary winding of at least one reducer transformer being formed by a conductor connecting two terminals of the associated input, and shielded by a non-magnetic material, said shielding being connected at its two ends to a grounded conducting part of the case.
2. The relay according to claim 1, wherein the shielding is formed by a braided strip made of non-magnetic material.
3. The relay according to claim 1, wherein said conducting part is formed by an external wall of the case on which said inputs are arranged.
4. The relay according to claim 1, wherein a first input signal being representative of the current flowing in a conductor of the mains system, the associated reducer transformer is a toroidal core current transformer whose primary winding is shielded.
5. The relay according to claim 4, wherein the current transformer primary forms a single turn.
6. The relay according to claim 1, wherein a second input signal being representative of the voltage of a conductor of the mains system, the associated reducer transformer is a voltage transformer whose primary winding is shielded.
7. The relay according to claim 6, wherein the voltage transformer comprises an insulating electrical shield between its primary and secondary windings, the shielding of the primary winding being connected to the grounded shield.
8. The relay according to claim 1, wherein the electronic processing unit is a microprocessor-based trip device.
9. The relay according to claim 1, wherein said conducting part is a metal wall of the case.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9004915 | 1990-04-11 | ||
| FR9004915A FR2661052B1 (en) | 1990-04-11 | 1990-04-11 | PROTECTION RELAY OF A MEDIUM VOLTAGE ELECTRICAL NETWORK. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2039550A1 true CA2039550A1 (en) | 1991-10-12 |
Family
ID=9395829
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2039550 Abandoned CA2039550A1 (en) | 1990-04-11 | 1991-04-02 | Protective relay of a medium voltage electrical mains system |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0452228A1 (en) |
| CA (1) | CA2039550A1 (en) |
| FR (1) | FR2661052B1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2729473A1 (en) * | 1995-01-16 | 1996-07-19 | Schneider Electric Sa | DEVICE FOR TESTING A PROTECTION RELAY CONNECTED TO NON-MAGNETIC SENSORS |
| EP2365618A1 (en) * | 2010-03-08 | 2011-09-14 | ABB Research Ltd. | Power supply unit for protective devices that reduces medium voltage |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE850488C (en) * | 1951-06-19 | 1952-09-25 | Utina Elektrowerk Gmbh | Electric fence with high frequency interference suppression |
| JPS4920891B1 (en) * | 1962-11-01 | 1974-05-28 | ||
| AT328551B (en) * | 1974-04-12 | 1976-03-25 | Siemens Ag Oesterreich | BROADBAND SHIELDING AGAINST MAGNETIC FLOW |
| DE3800572A1 (en) * | 1987-10-30 | 1989-07-20 | Vdo Schindling | COMBINATION INSTRUMENT FOR MOTOR VEHICLES |
-
1990
- 1990-04-11 FR FR9004915A patent/FR2661052B1/en not_active Expired - Fee Related
-
1991
- 1991-03-26 EP EP91420100A patent/EP0452228A1/en not_active Ceased
- 1991-04-02 CA CA 2039550 patent/CA2039550A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| FR2661052B1 (en) | 1995-04-14 |
| FR2661052A1 (en) | 1991-10-18 |
| EP0452228A1 (en) | 1991-10-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |