JP4615721B2 - Electrical switch device and method of interrupting electrical load - Google Patents

Description

[0001]
TECHNICAL FIELD The present invention relates to an electrical switch device having a mechanical high-speed electrical switch. The device is basically intended to cut off a large output current when an overcurrent occurs.
[0002]
The invention also relates to a method for interrupting an electrical load as set out in the preamble of the appended claims relating to the method.
[0003]
More precisely, the device according to the invention relates to the connection and disconnection of objects in a power plant or power network and to electrically connecting or disconnecting a specific part from a power generation facility or a connected object. It is. Here, “object” is used in a very broad sense, and is used as a concept including all devices and equipment included in the power generation facility and the power network, and each part of the power generation facility and / or the power network. .
[0004]
For example, the object is a device having a magnetic circuit such as a generator, a transformer, or a motor. Alternatively, another example of the object is a power transmission line, a switch gear device, or the like. The present invention is intended for use at medium and high voltages. Based on IEC standards, medium voltage refers to 1-72.5 kV, and high voltage refers to a voltage higher than 72.5 kV. Therefore, the voltage levels of power transmission, distribution and distribution are included in this.
[0005]
In power generation facilities, known breakers such as oil breakers or so-called vacuum breakers, for example called SF ₆ breakers, are usually used to connect and disconnect objects. In rare cases, when there is a demand to operate at a very high speed, for example, a semiconductor “breaker” such as a thyristor or IGBT is used.
[0006]
In any of these circuit breakers, when the current flowing between the two metal contacts (arch contacts) is interrupted, the current to be interrupted continues to flow as an arch. Therefore, when the current becomes zero, that is, at the moment when the polarity generated twice every 20 milliseconds changes in the case of a 50 Hz power supply network, the current is made zero. Therefore, this type of breaker can be used for alternating current, but cannot be used for direct current without a moment when the current becomes zero.
[0007]
The circuit breaker having the above-described structure needs to be redesigned so as to be able to cut off not only a moderate current, which is the case in most cases, a so-called operation current, but also a large overcurrent and a fault current.
[0008]
The circuit breaker needs to be designed so as to be able to cut off a large overcurrent energy that flows by forming an arc between the terminals. In order to prevent the arc from regenerating, that is, to guarantee the continuation of the interruption, it is necessary to give a very high insulation to the space between the terminals for a very short time after the interruption of the current.
[0009]
For example, oil breakers such as SF ₆ breakers or so-called vacuum breakers need to withstand large thermal and electrical loads at the same position in a short time, so that the structure becomes relatively complicated and up to shut-off. Time is relatively long.
[0010]
Here, the overcurrent basically means a large current at the time of a short circuit that occurs when the insulation system of the objects connected by the switch is lost. Such loss means that the short circuit current (short current) of the external network / device flows as an arc. As a result, very large damage will occur. The short circuit current (failure current) assumed in the Swedish power network is 63 kV. The short-circuit current (failure current) is actually 40-50A.
[0011]
The problem with the circuit breaker described above is that it takes a long time to shut off. The interruption time (IEC-standard) until the interruption is completely executed is 150 ms. With current equipment, it is very difficult to make this shut-off time shorter than about 90-130 ms. As a result, a very large current flows through the object during the time until the circuit breaker shuts off. The fact that the entire output of the external power network flows for this time is a very heavy load for the connected objects. During this time, the network operation is also hindered, and other devices connected to the same network are severely disturbed and damaged. In order to prevent connected objects from being damaged or catastrophic, the short-circuit current / fault current that flows during the circuit breaker shut-off time should not be damaged as much as described. It is necessary to process these. Designing the connected objects so that the short circuit current / fault current may flow for a significant amount of time results in increased cost and reduced performance. With respect to disturbances experienced by the network and the equipment connected to it, the network is currently not protected, so manufacturers are required to provide “backup” and network stabilization devices for sensitive devices. is there. More sensitive systems based on microprocessors such as communications and computer systems often require large and costly restarts.
[0012]
A semiconductor power device such as a thyristor, a MOSFET, or an IGBT cannot bear the above-mentioned voltage alone, and thus it is necessary to connect a plurality of components in series. In the case of high voltage installations, it is necessary to connect several hundreds of such components in series. For this purpose, in order to operate reliably, for example, complicated control is required so that voltage and power are evenly distributed to the components. Semiconductor components made of silicon are more lossy and require efficient cooling to prevent the components from being damaged by thermal failure. In all systems, including control, regulation and cooling, the system in which the components are connected in series with their own voltage is very complex and the overall cost is very high. That cost far exceeds the cost of circuit breakers, and for this reason, it has not generally been the case for semiconductor components to be used in power generation facilities and grids as described herein.
[0013]
The object of the present invention is to realize better switching, reduce the load applied to the connected object, and reduce the disturbance received by the network and the damage of other equipment connected to the network. An object is to provide a cost-effective apparatus and method.
[0014]
This object according to the invention is achieved by the device described in the preamble of claim 1. A switching element, hereinafter referred to as a shunt element, is connected in the form of a mechanical high-speed electrical switch in parallel with a first electrical switch having electrical contacts. The shunt element is designed to have conductivity when irradiated with light or an electron beam, for example. When cutting or shutting off, the shunt element is irradiated, which causes the shunt element to become conductive and the mechanical switch performs the shut-off without heat or electrical load. Preferably, when the breaker is in an open state, irradiation to the shunt element is stopped and the element is returned to the insulated state.
[0015]
When the object is not irradiated, it is reverse biased, and the object is made a power supply network or the like by using as a switching element a rectifier that generates free electrified carriers by receiving irradiation from a radiation source and flows current. If the switching element is interrupted very quickly within a desired time and the switching element is no longer irradiated, the element returns to reverse bias and immediately loses conductivity. Further, when the rectifying means is irradiated and the device is in a conductive state, the mechanical electric switch can be closed without a transient, which has a great advantage over the conventional one.
[0016]
Therefore, the present invention not only opens and closes a circuit based on mechanical operation, but also uses a conventional electric power semiconductor with high cost and high loss, and has a mechanical electric switch and a shunt element, and a switching device This is based on the principle of controlling the conductivity of the material by irradiation. By releasing the mechanical contacts from electrical and thermal loads, it is possible to perform a very fast interruption.
[0017]
According to a preferred embodiment, the control means is a rectifier diode. Using a reverse-biased diode as the second electrical switch in this device is easy and reliable to control by irradiation if necessary, and effectively blocks the voltage when in an insulated state. preferable. Furthermore, this type of diode is widely available on the market and can be purchased at a low price. According to CH1616-2, 80, 0000-0646 500.75, 1980 IEEE by P. Roggwiler and R. Sittig, the reverse-biased thyristor and anti-parallel diode connected to the reverse-biased diode Has been disclosed to make a thyristor off by making it conductive by generating free minority electrified carriers. If the time for which the diode is conductive is long enough, the thyristor is switched off. However, the present invention provides a new use of such a rectifier diode, i.e., having a mechanical high-speed electrical switch, handles the majority of the current flowing through the switching device, and the electrical switch breaks the circuit. The present invention proposes the use of a switch that can cut off the current flowing through the electrical switch device much faster, particularly when the power is high.
[0018]
The diode includes all possible ones that are controlled by irradiation, and the pn-diode, pin diode, and Schottky diode each correspond to a different embodiment. Such diodes are commercially available from this point of view at a low cost.
[0019]
According to one embodiment of the invention, the rectifying means comprises at least one layer made of SiC and at least one layer made of diamond. Such rectifying means made of SiC or diamond exhibits extremely excellent characteristics as an electrical switch means due to the characteristics of these materials. All of these materials have a very high breakdown voltage, and a remarkably high blocking voltage as compared with a rectifying means using a conventional semiconductor. This means that it is sufficient to use a smaller number of rectifying means in series in the situation where many conventional rectifying means must be used in series. Furthermore, SiC and diamond are stable even at very high temperatures up to 1000K, which is also a great advantage when handling high voltages.
[0020]
According to another preferred embodiment of the invention, the rectifying means is a photoconductive element. This makes it very easy to control the rectifying means.
[0021]
According to another preferred embodiment of the invention, the second electrical switch has a plurality of rectifying means connected in series and operates well even when the voltage is very high.
[0022]
In the case of another preferred embodiment of the present invention, it corresponds to a further improvement of the above-mentioned last configuration, and at least two of the plurality of rectifying means are connected to opposite polarities. One is in the positive direction and the other is in the negative direction. In this embodiment, the plural is two, and the configuration in which the two rectifying means are connected in opposite directions is particularly emphasized. This kind of switching device always has at least one rectifier in the reverse direction, this rectifier being made conductive by irradiation, and if necessary a second electrical switch carrying the majority of the current. It can be used to cut off alternating current very quickly. When using more than one rectifier, all the rectifiers must be reverse-biased in order for the switch element to become conductive, which means that the source is reverse-biased. This is illustrated in yet another embodiment of the present invention which is arranged to irradiate all added rectifying means simultaneously.
[0023]
In another preferred embodiment of the present invention, the apparatus has a plurality of the above-described mechanical high-speed electrical switches in series, and a second electrical switch is connected in parallel with each of them. This type of device is used to handle very large amounts of power, and the mechanical high speed electrical switch is preferably controlled simultaneously as the second electrical switch.
[0024]
According to another preferred embodiment of the invention, the switch element has a number of stacked semiconductors including three of which two of the outermost layers are otherwise doped with a first conductivity n or p. The intermediate layer is doped to the second conductivity to form two pn junctions that form the same number of rectifiers connected in series and having opposite polarities. This type of switch element can be suitably used to cut off alternating current at high speed regardless of the phase state.
[0025]
According to another preferred embodiment of the invention, the switch element comprises an intermediate bulk layer, a p-doped island on one side of the intermediate layer, and the opposite side of the intermediate layer. And an n-doped layer provided so as to substantially cover a position corresponding to the space between the islands, and a continuous alternating current flow path from the n-type layer to another p-type layer And a plurality of pin diodes having two consecutive diodes having opposite polarities. This type of switch element can be suitably used for extremely high voltages, and can switch AC voltage at high speed due to its “bipolar” type structure.
[0026]
According to a further embodiment of the invention, at least one varistor is connected in parallel to the first electrical switch and the switch element. An induced current is generated in the varistor due to the inductive load at the time of interruption, and the energy due to the magnetic field is absorbed by the varistor. Thus, the varistor consumes magnetic field energy that can be stored in the electrical switch.
[0027]
According to another preferred embodiment of the present invention, any of the electrical switch devices described above are connected to or disconnected from a power generation facility to form a power network or connect other devices to the power plant. Do things. This is a preferred application for this type of switch device when it is important to connect and disconnect objects at high speed.
[0028]
The present invention further includes a second electrical switch connected in parallel with the first mechanical electrical switch, a radiation source, a switch element that reacts to radiation, and when the switch element is illuminated by the radiation source, It includes a method of interrupting a particularly high power load by means comprising a mechanical high speed electrical switch that transitions from an insulated state to a conductive state and exhibits excellent electrical conductivity and blocks the first electrical switch. Since this method can perform a very high-speed interruption, it is a preferable method for interrupting an electrical load.
[0029]
Further advantages and preferred properties of the invention will become apparent from the following description and other dependent claims. Preferred embodiments of the present invention are described below with reference to the accompanying drawings.
[0030]
Detailed description of a preferred embodiment of the invention Figure 1 is a very conceptual representation of an electrical switch device 1 according to a first embodiment of the invention. This apparatus is installed in a power plant including an object 2 such as a generator. The object is connected to an external power supply network 4 by a line 3. The electrical switch device is provided to connect and disconnect the object 2 to and from the power network 4. However, it should be emphasized that the object can be similarly switched to any other part of the power generation facility. The interruption of the object 2 from the network is performed for the purpose of protecting the object and the device from the fault current of the network, or to protect the network from the voltage and operation disturbance caused by the large fault current flowing to the object. Is called.
[0031]
The switch device comprises a first electrical switch 5 in the form of a mechanical high-speed switch, which is a disconnector or a breaker with contacts that are separated from each other for connection and contact with each other for connection. The second switch 6 connected in parallel with the first switch comprises a switch element in the form of a photoconductive diode 7 arranged to be reverse biased when the object 2 is connected to the network 4. Network 4 is a DC network in this example. The second electrical switch further includes a radiation source 8 that irradiates the diode 7 with free charge carriers and maintains the diode 7 in a conductive state during irradiation. The switching element is controlled by a source that is electrically separated from the element.
[0032]
Furthermore, the device has a control unit 9 for controlling the source 8 and the mechanical switch 5. The unit is connected to a sensor 10 that detects a parameter indicating an overcurrent on the line 3.
[0033]
A varistor 11 is connected in parallel with the mechanical switch 5 and its function will be described below.
[0034]
This electrical switch is very fast compared to a conventional circuit breaker, meaning that the fault current in line 3 does not reach its maximum value.
[0035]
FIGS. 2 and 3 show what happens when the sensor 10 detects an overcurrent and the control unit 9 causes the switch device to shut off the object 2 from the network / facility 4. At time t ₁ is the detection time of the overcurrent, the mechanical switch receives control to open the contacts, contact spreads the distance between two contact points, as indicated by line x in Fig. At the same time, the light source 8 is controlled to start irradiating the diode 7, and the conductivity of the diode changes as indicated by σ in FIG. This means that while the mechanical switch is activated, the gap when the mechanical switch 5 is controlled is substantially free of electrical or thermal loads. Instead, the current path is interrupted by a diode 7 (shunt element) in which the varistor 11 absorbs the energy of the magnetic field. In this way, the fault current is interrupted at a very high speed. Source 8 gives the radiation to the diode 7 at time t ₂ when the contacts of the mechanical switch 5 is maximized opening, when the irradiation of the diode is completed, the network a mechanical switch 5 is no problem object / Electrically insulate from equipment 4.
[0036]
FIG. 3 shows, within the mechanical switch, whether the current I ₁ falls from t ₁ which is the start point of the shut-off operation, and whether the current I ₂ flowing in the diode 7 falls from t ₁ to t ₂ . FIG.
[0037]
When the object 2 needs to be connected to the network / equipment 4 later, the electrical switch device again irradiates the diode 7 by the source 8 of the control unit 9 and the mechanical switch causes a transient change. Close without closing.
[0038]
The electrical switch device portion of the second preferred embodiment of the present invention is shown very conceptually in FIG. This embodiment is different from the embodiment shown in FIG. 1 in that the switch element includes two diodes 7 and 7 'connected in series in opposite directions. For each diode, a source 8, 8 'is provided. This device is suitable for alternating current switching because one diode is always reverse biased unless irradiated. When an overcurrent is detected and the contact of the mechanical switch 5 is released, the radiation source corresponding to the diode that is reversely biased at that time starts irradiating, and the DC voltage described with reference to FIGS. A similar blocking process is recommended.
[0039]
FIG. 5 shows an AC switch element by a pnp or npn laminated semiconductor layer 12-14 structure. The outermost layers 12 and 14 are of the same conductivity type n or p, and the intermediate layer is doped to the opposite type p or n. Accordingly, pn junctions are formed between the junction surfaces 15 and 16, and a reverse voltage is applied to one of the junction surfaces depending on the direction of the voltage applied to the semiconductor component. Two light sources 8, 8 'are provided in the same manner as the two diodes 7, 7' shown in FIG. For example, when the layer 12 is irradiated with a bias voltage applied to the pn junction 15, minority carriers are generated in the layer 12, and a current flows through the junction surface.
[0040]
FIG. 6 shows a device that can replace the device shown in FIG. 1 in the case of a DC voltage. The figure shows a state in which a rectifier in the form of a diode is connected in series in the mechanical switch 5 as necessary when the voltage is high. Each diode is provided with a varistor 11 so that the energy of the magnetic field is absorbed and the diodes 7 and 7 ′ are equally responsible for the voltage and power when the diodes are cut off. The circuit breaker is provided between the switch element 6 and the network / equipment 4, and after the object 2 is disconnected from the network / equipment, the network / equipment 4 is dioded to remove the voltage from the disconnected diode. Control to be cut off from.
[0041]
Still another embodiment of the present invention shown in FIG. 7 is a combination of the embodiment shown in FIG. 6 and that shown in FIG. In this case, two mechanical switches 5, 5 ′ are connected in series, and diodes 7, 7 ′ opposite to each other are connected in series with each mechanical switch in parallel. The device is suitable for interrupting alternating current, and can handle high-voltage current because mechanical switches are connected in series.
[0042]
FIG. 8 shows a preferred method of producing a plurality of rectifying means for a switch element that can be used in a switch device for switching alternating current. The switch element 6 is composed of cascade-connected pin diodes embedded on the same semiconductor. It is easy to manufacture a cascade with a large number of diodes, eg 10-40, from a single “semi-insulating wafer”. The upper surface is doped with, for example, p-type so as to have the first conductivity or is covered with a similar layer, and the lower surface is doped with the opposite, for example, n-type. For example, layers 18-20 are doped p-type, layers 21-23 are doped n-type, and layer 17 is substantially undoped. The right side of FIG. 8 shows how the diode is configured. If each element (diode) is a 1 kV switch, when 40 diodes are connected in series, 20 kV can be switched as a whole. This structure functions as a conventional photoconductive switch, that is, it is conductive when irradiated and insulating when not irradiated. The switching performance of each diode depends on the material used, the layer thickness 17 and the doping characteristics, and by using SiC or essentially diamond for the layer 17, the diodes have a very high voltage, for example a voltage of 10 kV or higher. Can be prevented.
[0043]
Naturally, the present invention is not limited to the above-described embodiments, and many modifications are possible within the scope of the technical idea of the invention defined by the description of the claims.
[0044]
The number of rectifiers, mechanical switches and other components is of course arbitrary.
[0045]
The radiation source may irradiate visible light, UV light, IR light, electron beam, ion beam, x-ray or the like.
[Brief description of the drawings]
FIG. 1 shows the most basic configuration of an electrical switch device according to a first preferred embodiment of the present invention.
2 shows the distance x between the contacts of the mechanical electrical switch of the electrical switch device shown in FIG. 1 and the electrical conductivity of the photodiode with respect to the passage of time when the electrical switch device interrupts the load. .
3 shows the magnitude of the current I ₁ flowing through the mechanical electrical switch and the magnitude of the current I ₂ flowing through the photoconductive device with respect to the elapsed time from when the load is cut off in the configuration shown in FIG. FIG.
FIG. 4 is a simplified drawing of an electrical switch device according to a second embodiment of the present invention.
FIG. 5 is a sectional view of a switch element of a switch device according to a second embodiment of the present invention.
FIG. 6 is a conceptual diagram illustrating a switch device according to a third embodiment of the present invention.
FIG. 7 is a conceptual diagram showing a switch device according to a fourth embodiment of the present invention.
FIG. 8 is a conceptual diagram showing a switch element of the switch device according to the present invention.

Claims (21)

An electrical switch device comprising a first mechanical high speed electrical switch (5, 5 '),
A second electrical switch (6) is connected in parallel with the first mechanical high-speed electrical switch, electrical switch (6) of said second radiation source and (8,8 '), at least one first Switch elements (7, 7 ')
The at least one switch element (7, 7 ') comprises a plurality of rectifying means (7, 7') connected in series;
The rectifying means (7, 7 ') is sensitive to irradiation, becomes conductive when irradiated from a radiation source, bypasses the first mechanical high-speed electrical switch and does not receive irradiation. in a state has an insulating property, a rectifying means for receiving a reverse bias, by generating free charge carriers when irradiated from the source have a conductivity,
At least two (7, 7 ') of the plurality of rectifying means are connected in the opposite directions, and at least one is connected in the negative bias direction when at least one is connected in the positive bias direction. ,
The plurality of rectifying means (7, 7 ′) include an intrinsic bulk layer (17) as an intermediate layer, and a plurality of p-doped islands (18-20) formed on one surface of the intermediate layer. An n-doped island (21-23) formed so as to substantially cover a portion corresponding to a region between the p-doped islands on the other surface of the intermediate layer, A plurality of pin diodes connected in series to form a current flow path alternately from the p-type layer through the p-type layer, the two diodes being two diodes continuous in opposite directions,
The electrical switch device has a plurality of first mechanical high-speed electrical switches (5, 5 ′) connected in series, and a second electrical switch (6) is connected in parallel to each of the first mechanical high-speed electrical switches (5, 5 ′). Electrical switch device.   2. A device according to claim 1, wherein the rectifying means (7, 7 ') are rectifier diodes.   The apparatus of claim 2, wherein the diode is a pn diode.   The apparatus of claim 2, wherein the diode is a Schottky diode. Apparatus according to any one of claims 1 to 4 wherein the rectifying means and having at least one Si layer. Apparatus according to any one of claims 1 to 4 wherein the rectifying means and having at least one SiC layer. Apparatus according to any one of claims 1 to 4 wherein the rectifying means and having at least one diamond layer. Apparatus according to any one of claims 1 to 7, characterized in that said rectifying means (7, 7 ') is a photoconductive element. Apparatus according to any one of the radiation source (8,8 ') is claims 1, wherein the addition of irradiated simultaneously to all of the rectifier means for receiving a reverse bias 8. The switch element has three stacked semiconductor layers (12-14), two outer layers (12, 14) are doped to have a first conductivity, and an intermediate layer (13) A rectifying means doped with a second conductivity, resulting in two symmetrical pn junctions, forming two rectifying means with opposite bias characteristics connected in series. The apparatus according to any one of 1 to 8 . It said first mechanical high-speed electrical switch (5, 5 ') A device according to any one of claims 1 to 10 is a disconnector. At least one means (11) for absorbing magnetic energy that may occur during device disconnection is the first mechanical high-speed electrical switch (5, 5 ') and switching element (7, 7'). ) and apparatus according to any one of claims 1 to 11, characterized in that it is connected in parallel. Device according to claim 12 , wherein the magnetic energy absorbing means is a varistor (11). Apparatus according to any one of claims 1 to 13, characterized in that the switch element (7, 7 ') and the radiation source (8,8') is not electrically connected to each other. The control unit (9) is connected to the first mechanical high-speed electrical switch and a second electrical switch, the first mechanical high-speed electrical switch and the second electrical switch on the basis of the information to reach the control means apparatus according to any one of claims 1 and controls the functions 14. 16. Device according to claim 15 , characterized in that means (10) for detecting overcurrent is connected to the control unit and supplies information relating to overcurrent thereto. The control unit (9) controls the second electrical switch (6) during disconnection to cause the switch element to form a conductive current flow path by irradiation, and then the first mechanical high speed The device according to claim 15 or 16 , characterized in that an electrical switch is interrupted. The object (2) is connected or disconnected at high speed from the power supply network (4) of the power plant or other equipment included in the power plant, and the first mechanical high-speed electrical switch and the second electrical switch are connected to the object. apparatus according to any one of claims 1, characterized in that connected to the line (3) between the network or equipment 17. Or high voltage in the above 5 kV, in particular 10kV or more voltage, preferably at least 20 kV, more preferably 40 kV, more preferably to any one of claims 1 to 18, characterized in that it is used in the above voltage 72kV The device described. Power plant, the method used to connect and cut off the object from other equipment included in the power network or power plant, an electrical switch device according to any one of the claims 1 to 18. A method for electrically disconnecting a load (2), in particular under high voltage, by means of a plurality of first mechanical high-speed electrical switches (5, 5 ') connected in series,
A second electrical switch (6) connected in parallel with each of the first mechanical high-speed electrical switches, comprising a radiation source (8, 8 ') and a plurality of series connected rectifiers responsive to irradiation (7, 7 '), a switch that becomes electrically conductive when irradiated from a radiation source and changes from an electrically insulated state to a highly electrically conductive state, bypassing the first mechanical high-speed electrical switch In a method of using a second electrical switch having an element and interrupting by a first mechanical high speed electrical switch,
At least two (7, 7 ') of the plurality of rectifying means are connected in the opposite directions, and at least one is connected in the negative bias direction when at least one is connected in the positive bias direction. ,
The plurality of rectifying means (7, 7 ′) include an intrinsic bulk layer (17) as an intermediate layer, and a plurality of p-doped islands (18-20) formed on one surface of the intermediate layer. An n-doped island (21-23) formed so as to substantially cover a portion corresponding to a region between the p-doped islands on the other surface of the intermediate layer, A plurality of pin diodes that are connected in series to form a current flow path alternately from the p-type layer through the p-type layer, and that are two diodes that are continuous in opposite directions A method characterized by that .

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