• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    Summary A device that can handle electrical earth faults, ie when an unwanted current between a conductor and earth occurs. The device generates an inductive impedance cla an earth current is generated. (Fig. 1)
    公开号:SE1100960A1
    申请号:SE1100960
    申请日:2011-12-28
    公开日:2013-06-29
    发明作者:Agne Faelldin
    申请人:Kkm Ab；
    IPC主号:
    专利说明:

    Technical field The invention relates to a device for handling earth faults. In particular, the invention relates to a device for handling earth faults in a three-phase system.
    Background By earth fault is meant, among other things, that a leader has made contact with earth, i.e. the ground. This can e.g. due to defects in the insulation or that an overhead line has fallen to the ground or even worse that a person has come into contact with live conductors. Sometimes direct contact (short circuit) occurs and sometimes there is a transition resistance to ground. In some contexts, continued operation with existing faults was allowed.
    In an electrical system such as an electrical three-phase system, earth faults occur when a phase conductor comes into contact with earth. Earth faults are an undesirable phenomenon and can not always be prevented. As it can be black to completely prevent earth faults, it is unfortunate that the negative consequences of an earth fault are minimized. An example of a device that minimizes the consequences is so-called earth fault circuit breakers that switch off the voltage on a conductor when staff] between (phase) conductor and earth occurs.
    SUMMARY OF THE INVENTION It is an object of the invention to provide an electrical circuit which reduces the negative consequences of the occurrence of earth faults.
    This object and also others can be achieved by means of a device as defined in the appended claims.
    In one embodiment, a device is provided for connection to an electrical system and intended to reduce earth currents in the electrical system, in particular a three-phase alternating voltage system. The device comprises at least one magnetic core and at least one winding comprising an input terminal and an output terminal wound around the magnetic core, the input terminal and the output terminal being generally connected to a conductor in the electrical system. SarskiIt is arranged at least one winding per phase.
    In an embodiment where the electrical system comprises several conductors, the device has a winding for each conductor, if applicable also for a neutral conductor.
    In one embodiment, the device comprises a winding for a neutral conductor in the electrical system.
    In one embodiment, the magnetic core forms a closed circuit.
    In one embodiment, at least one of the windings is divided into two or more windings. In particular, the windings can be symmetrically divided on each phase.
    In one embodiment, the device comprises more than one cam.
    In one embodiment, the device is designed to generate an adjustable inductive impedance.
    In one embodiment, the device is designed to adjust the inductive impedance by means of N2 change, change of air gap or parallel river flow.
    The electrical system can be a low voltage night (typically up to 1000 Volts), an intermediate voltage / distribution system (typically up to 36 kVolt), a transmission system / high voltage night (typically over 36 kVolt), or an electrical installation (such as a multiphase motor).
    Brief description of the drawings The invention will now be described in more detail and with reference to the accompanying drawings, in which: Figs. 1a - 1c show a device for handling earth faults in a three-phase system in a first embodiment, Fig. 2 shows a device for Fig. 3 shows a device for handling earth faults in a three-phase system in the first embodiment connected in an electrical system, Fig. 4 shows a device for handling earth faults in a three-phase system in the second embodiment connected in an electrical system, and Fig. 5 shows a device for compensating capacitive fault currents.
    Description of embodiments The invention can be realized in different embodiments depending on the application and desired construction. For example, the area needs sasonn: Team voltage system (typically up to 1000 Volts) Medium voltage system / distribution system (typically up to 36 kVolt) Transmission system (typically Over 36 kVolt) Electrical installations (eg marine and offshore installations) a device that can handle electrical earth faults, ie when an unwanted current between a conductor and ground occurs. These different areas all have different needs and a device for limiting earth currents or other unwanted currents must therefore be designed differently depending on the application.
    Law Voltage System The device described herein is intended for the case of a law voltage night to minimize short circuit currents. In the law voltage case, the purpose may thus be to counteract a high-impedance fault from phase to ground for reduced malfunction in an installed earth fault circuit breaker or to reduce the influence of vagabonding earth currents. The example shown below in connection with Fig. 1 shows how a unit with 4 windings can be used in a low voltage system. The function is that in the event of a fault, ie closing between phase and earth, the unit picks up the voltage across the winding that closes to earth and forms an inductance. The inductance in this case acts as a current tester for the current that may flow between phase and neutral conductor, so-called zero sequence. Relative plus / minus sequence (phase / phase supply) is not affected to the nominal extent.
    Fig. 1a shows a device for limiting earth current according to a first embodiment. The device is intended to be connected in a legal voltage system with three phase conductors and one neutral conductor. The device can, for example, be arranged at the input of an electric law voltage night. For example, the device can be placed adjacent to a switchboard for an electrical system on a house or the like.
    The device in Fig. 1a consists of a core arranged to close a magnetic flock. The cam of this shell is preferably formed in a closed circuit, although it is possible to let the circuit contain an air gap. (be Open). Kaman consists, for example, of jam n or transformer plate or of some other material with good conductivity for a magnetic flux.
    Around the karnan there are a number of windings arranged. The windings consist of a material with good electrical wiring such as copper or aluminum. In the case of a three-phase system with a neutral conductor, four windings can be provided. The windings have an input terminal (A1, A3, A5, Neutral IN), and an output terminal (A2, A4, A6, Neutral OUT). Each winding can also consist of several, typically serially, arranged windings to achieve a similar serial resistance. Delta is shown in Fig. 1 b. Fig. 1b shows a substantially rectangular vessel 1 with (at least) two legs. Around each leg, three windings 2 each (one for each phase) are arranged. The windings on each leg are serially connected to form an interconnected winding per phase. In this case, the outer winding on one leg can be connected to the inner winding on the other leg so that the total winding length (and the armed resistance) in total becomes essentially the same for all phases / conductors. This is also shown in Fig. 1c which is a section from above 4 of the device shown in Fig. 1 b. The respective winding 2 has been indicated as winding 2a, 2b and 2c, respectively.
    The device is connected so that the input terminal of the usual winding is connected to the electrical network and the output terminals form output terminals to which different loads can be connected.
    The reason for all the 4 conductors used throughout the unit is that it should be possible in a legal voltage system to install single-phase loads that relate to the system zero, ie the same point as the system earth, but with a parallel! management. The device can also be realized without a winding for the neutral conductor as shown in Fig. 2.
    Fig. 3 shows the device named "zero sequence device" (zero sequence device) connected between a delta (D) - Y connected transformer (transformer) and end user / load (load). The device in Fig. 3 has three windings, one for each phase (L1, L2, L3), where the usual winding is divided into two (sub) windings. Fig. 4 shows the device (zero sequence device) connected in a system without a neutral conductor. The same parts are named in the same way as in Fig. 3. It should be noted, however, that the dimensioning of different parts may differ depending on different application areas (see below). Dimensioning takes place so that the inductive impedances become large in relation to the resistive load through which an generated earth current can be expected. In this way, the earth current is limited or eliminated completely.
    Function in the device is based on the ratio plus sequence, minus sequence and zero sequence as follows: The cam, which is built up of, for example, transformer material, serves with the function of a sum current transformer. That is, when the currents are symmetrical in the system and when no faults to earth occur, the inductance of the device is near the nail. Salunda, no flood in the karnan and armed negligible inductance. During normal operation, only the conductors are in series as an additive in the electrical circuit. In the event of an earth fault (earth fault), however, the unit will react with a shift in the energy ring from Y's phase - phase vectors in the fault case to D's parallel displacement.
    The plus / minus sequence will not see any inductance generated as symmetry continues. The configuration of the night (Delta D) with the secondary side (Y) of the feeding transformer then gives the following. The transformer will see the device as described as a very large inductance at the fault event per the phase shorted and the UO voltage (phase-zero voltage) will fall across the unit corresponding to the size of the earth fault and inductive Ohm numbers. Thus, no active current (active power) will flow through the zero-follower circuit in the event of a fault, this regardless of the resistance of the short-circuited call.
    This solves personal safety issues in the home, office workplaces, industrial buildings, ships and other "off shore" electrical installations. In addition, operational problems connected to earth fault currents in, for example, ships and "off shore" systems can be eliminated.
    Distribution systems In wired systems or in the case of "over headlines", a reactive power is generated which can be defined as a capacitive fault current (ICj). This fault current can be compensated with a device as described herein while a resistive fault current is minimized. This function is obtained by providing the device with an adjustability in the generated inductance which, I 12 change, change of air gap or parallel falflow displacement, for example by direct voltage magnetization of the core part entering the circuit.
    Fig. 5 shows a device designed for this application. The device consists of 4 cores (3a, 3a, 3b, 3b). Each vessel may comprise one or more bones. The device further has 3 windings (3d, 3f, 3g). These windings are arranged in a conventional phase and in order for the serial to be connected to the respective phase as shown above, for example as shown in Fig. 4. In the device the phase windings (3d, 3f, 3g) are divided into two windings, the respective winding enclosing two legs belonging to different nuclei. The divided windings are connected to each other by the respective wires (3h, 3i, 3j). The device further comprises a further winding, a direct current winding (3c) which may be arranged around two legs of different cores as shown in the picture, the direct current winding being arranged to be used with direct voltage to control the magnetization in the circuit whereby the inductive impedance generated by the device can is controlled so that a capacitive fault current can be compensated in the desired manner. In this way, a device is obtained which can both counteract resistive earth currents and is used to compensate for capacitive fault currents.
    Thus, in Fig. 5, 4 rectangularly shaped vessel parts are arranged. Around one leg on a first vessel part and around one leg on a second vessel part, three first windings are arranged. Furthermore, the direct current winding is arranged around a leg on the second core part and around a leg on a third core part. Furthermore, three further windings which are interconnected with three first windings, respectively, are arranged around a leg on the third core part and around a leg on the fourth core part.
    Transmission system Transmission systems are currently directly earthed and reconnected in the event of a ground fault with a Mgt Amperetal in the range 20 -45 kA. With this in mind, there is every reason to try to reduce this short-circuit penalty to a manageable value. This can be achieved by means of the device as described, which in the event of a fault can be designed to generate a high inductive impedance (in accordance with the description above for low voltage systems), which reduces the short-circuit current.
    Electrical installations In the case of, for example, marine and offshore applications, there are electrical installations that can generate earth currents that can negatively affect motors / motor bearings negatively. The device as described could be connected to the electrical system in this case to actuate these earth currents.
    By using the device described herein, resistive ground currents can be reduced because the device in this case produces a high inductive impedance which aims to limit the resistive current between conductor and ground. In addition, the device can be designed to provide an adjustable inductive impedance for distribution systems to counteract / compensate for capacitive currents that may occur there. 8
    权利要求:
    Claims (9)
    [1]
    The device is connected to an electrical system and is intended to reduce earth currents in the electrical system, the device comprising: - at least one magnetic core - at least one winding comprising an input terminal and an output terminal wound around the magnetic core, the input terminal and the output terminal being connected in series to a conductor in the electrical system.
    [2]
    Device according to claim 1, wherein the electrical system comprises several conductors and the device comprises a winding for conventional conductors.
    [3]
    Device according to claim 1 or 2, wherein the device also comprises a winding for a neutral conductor in the electrical system.
    [4]
    Device according to any one of claims 1 - 3, wherein the magnetic core forms a closed circuit.
    [5]
    Device according to any one of claims 1 - 4, wherein at least one of the windings is divided into two or more windings.
    [6]
    A device according to any one of claims 1 to 5, wherein the device comprises more than one cam.
    [7]
    Device according to any one of claims 1 - 6, wherein the device is designed to generate an adjustable inductive impedance.
    [8]
    Device according to claim 7, wherein the device is designed to adjust the inductive impedance by means of N2 change, change of air gap or parallel! fall river displacement. 9
    [9]
    Device according to any one of claims 1 - 8, wherein the electrical system is a three-phase AC voltage system. 1 / Al A3 A4 A A6 Neutral in Neutral out
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    同族专利:
    公开号 | 公开日
    SE537358C2|2015-04-14|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    SE1100960A|SE537358C2|2011-12-28|2011-12-28|Device for earth fault|SE1100960A| SE537358C2|2011-12-28|2011-12-28|Device for earth fault|
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