Auxiliary power supply of the device at a high potential

Abstract

The magnetic structure (60) comprises input and output stages (61, 62) having yokes (61c, 62c) and at least two cores (61a, 62a), and at least one intermediate stage (63) having a core (63a) magnetically coupled to the input and output stages. By providing a gap (64) having a permeability and a high voltage withstand capacity to provide magnetic coupling between the stages, poles (61d, 62d, 63d) for expanding the cross-sectional area of the core, and windings (61b, 62b, 63b) provided on the cores, a transformer having extremely high insulation is provided, and the poles of adjacent stages are provided on opposite surfaces of the gap (64), thereby providing magnetic coupling between both surfaces of the gap (64).

Description

Technical Field

[0001] The present invention relates to an apparatus and method for supplying auxiliary power from a grounded power source to a power consuming device close to or in electrical contact with a high voltage facility. The high voltage system related thereto can be an AC (alternate current) or DC (direct current) power transmission system having a rated operating voltage in the range of 50 kV to 800 kV. The power level for transmitting auxiliary power from ground to high potential can be tens of watts to several kilowatts. The above apparatus is a transformer having a very high level of insulation between a primary winding and a secondary winding operating at a high frequency in the range from 2 to 3 kilohertz to several hundred kilohertz.

Background Art

[0002] Measuring and control devices on high potential generally require low power of 2 to 3 watts or less. These requirements can be met by an auxiliary power source having a limited power supply capacity, for example, a system using optoelectronic power supplied by a fiber.

[0003] On the other hand, switch devices such as current breakers (circuit breakers) and disconnect switches require much larger energy in the range of kilojoules for each switching operation, and generally require mechanical operation by a mechanical actuator on the ground and an insulating mechanical link such as a push rod (pushing rod) or a swing (swinging) arm to be transmitted to the moving contact in the switch. The mass moving in this way is a considerable amount, and the operation time between the opening command (command word) and the contact separation becomes long.

[0004] It has been proposed decades ago to place an actuator at the same potential as the moving contact near the moving contact to shorten the operating time of the circuit breaker. A typical configuration is to establish the accumulation of local energy on a high potential and supply the necessary electrical energy to the local actuator. Such accumulation must be replenished with energy supplied from the ground potential. The present invention relates to an apparatus for this purpose.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention is a magnetic transformer having extremely high insulation between its primary winding and secondary winding. Thus, a magnetic loop structure is provided, which allows magnetic flux to circulate through both the power transmission winding and the power reception winding. This magnetic structure has one or several gaps filled with an insulating material having a high breakdown voltage capacity such as epoxy, polyurethane, silicon, or other polymeric materials. The insulation can be composed of solid insulating disks and / or cast materials. Oil or gas can also be used as the insulating material.

[0006] When the insulation withstands several hundred kilovolts, the required gap length is several centimeters. According to the present invention, such a transformer can: - The total gap length is divided into several smaller gaps along the magnetic path, - The magnetic structure is provided by extended poles facing each other on both sides of the insulating layer within the gap, - Reactive power is provided by capacitors along the magnetic loop, - The transformer operates at some frequency within the range of 1 kHz to 200 kHz can be realized in the case.

[0007] The transformer generally has a very small capacitance in the picofarad range between its primary winding and secondary winding.

[0008] An object of the present invention is to provide a magnetic transformer having extremely high insulation between its primary winding and secondary winding.

Means for Solving the Problems

[0009] According to the present invention, a magnetic structure is provided, which includes: an input stage having an input yoke and at least two input cores; an output stage having an output yoke and at least one core; and at least one intermediate stage having at least two cores. The input stage is magnetically coupled to one of the at least one intermediate stage, and the output stage is magnetically coupled to one of the at least one intermediate stage. This magnetic structure includes a gap having a low magnetic permeability and a high withstand voltage capacity, which provides magnetic coupling between stages, and poles that expand the cross-sectional area of the core by having a larger cross-sectional area than the core. The poles of adjacent stages are provided on opposite surfaces of the gap, thereby providing magnetic coupling between both surfaces of the gap. A winding is provided on the core of the input stage, configured to obtain power from a power source at ground potential and transmit this power to the output stage. A winding is provided on the core of the output stage, configured to receive AC power from the input stage and supply this AC power to a power conditioning device for supplying auxiliary power to a device connected to a high-potential relative ground. A winding is provided on the core of at least one intermediate stage, connected to a capacitor that supplies a distributed magnetization current to the magnetic structure.

[0010] In a preferred example, the low magnetic permeability is a relative magnetic permeability of less than 10, preferably less than 2.

[0011] In a preferred example, the high withstand voltage capacity exceeds 5 kV / mm. This means that the total withstand voltage capacity is generally in the range of 50 to 100 kV.

[0012] In a preferred example, a plurality of intermediate stages are provided, and all of the intermediate stages are magnetically coupled to each other between these intermediate stages.

[0013] In a preferred example, the core, winding, pole, and capacitor are enclosed in a metal container or a container having a conductive surface, i.e., a "Faraday cage" for each stage.

[0014] In a preferred example, the containers of all stages are stacked in a tube filled with an insulating material, a liquid of a cast polymer insulator. The containers of the stages are preferably stacked in a tube filled with an insulating material, a liquid or a cast polymer insulator, and are preferably enclosed in a metal enclosure ("dead tank") connected to the ground potential.

[0015] In a preferred example, two core legs are present in each stage. Alternatively, three core legs are present in each stage.

[0016] In a preferred example, series compensation capacitors are provided in the input stage and the output stage.

[0017] In a preferred example, the input stage is powered from a VSC (voltage source converter), and the VSC obtains power from a DC power source on the ground potential, preferably from a station battery within a switchyard.

[0018] In a preferred example, the output stage powers a passive rectifier or, alternatively, a VSC, and the passive rectifier or the VSC supplies a DC voltage used as an auxiliary power source for a device at a high potential.

[0019] In a preferred example, additional windings are provided in several intermediate stages, and these additional windings power several VSC regulating devices for providing an auxiliary power source to several series-connected modules.

[0020] In a preferred example, the above gap is 1 to 2 millimeters.

[0021] Hereinafter, the present invention will be described by way of example with reference to the accompanying drawings.

Brief Description of the Drawings

[0022]

Figure 1

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Figure 12

Embodiments for Carrying Out the Invention

[0023] Detailed Description of Embodiments The following describes a detailed explanation of the magnetic structure according to the present invention. In this explanation, references to directions such as "up" are those shown in the drawings.

[0024] FIG. 1 shows a conventional gapless two-winding transformer having a magnetic core 1, and the magnetic core 1 passes through each of the primary winding 2 and the secondary winding 3. These windings are insulated from the core and from each other and can withstand a specified voltage stress, which is generally of the same order of magnitude as the intended operating voltage.

[0025] FIG. 2 shows a configuration having a magnetic core 1, and the magnetic core 1 passes through each of the primary winding 2 and the secondary winding 3, and a gap 4 filled with an insulating material is inserted into the magnetic structure to expand the withstand voltage capacity between the input voltage and the output voltage. However, before the magnetization current of the transformer reaches a level, only a small gap, preferably a gap of 1 to 10 millimeters, more preferably 1 to 5 millimeters, and even more preferably 1 to 2 millimeters can be inserted, making the effective power transmission very inefficient. These gaps have a low magnetic permeability and a high withstand voltage capacity, thereby resulting in magnetic coupling between the poles. In a preferred embodiment, the low magnetic permeability is a relative magnetic permeability of less than 40, preferably less than 2. The high withstand voltage capacity is a withstand voltage capacity exceeding 5 kV / mm.

[0026] FIG. 3 shows a configuration in which a soft magnetic pole 5 is inserted to expand the cross-sectional area A of the magnetic core facing the gap 4. e The permeance of the gap is the ratio A of the cross-sectional area of the core to the gap length δ. eIt is given by / δ. Therefore, when the cross-section is enlarged without changing the characteristics of the magnetic structure, the gap length can be increased proportionally. The enlarged gap 4 enables the input winding 2 and the output winding 3 to be separated using a larger amount of insulating material, thereby increasing the withstand voltage capacity between the input winding and the output winding.

[0027] The design described with reference to FIG. 3 enables the gap 4 in the transformer core to be widened by up to one digit compared to what is practical without such pole configurations.

[0028] Many applications in power transmission systems benefit from obtaining an auxiliary power supply to a device at a high potential from the DC battery of a grounded battery-supplied station, which DC battery is available within the switchyard. The insulation between the input winding and the output winding for such devices can be tested at amplitudes up to the megavolt range with "basic lightning impulses" or "basic switching impulses".

[0029] The total gap length required for an insulating material that provides a withstand voltage capacity of several hundred kilovolts can reach several centimeters. Such a gap length cannot be achieved with a conventional ferrite core with a gap rated for 2 - 3 kilowatts.

[0030] FIG. 4 shows a magnetic structure including several gaps 4, which enables an "enlarged" gap using the principle shown in FIG. 3. The magnetic flux is guided by the intermediate core 6 between the gaps. This structure can be designed with a sufficient number of gaps to provide the relevant withstand voltage capacity for power supply to a device at a high potential.

[0031] The capacitance between the output winding 3 and the input winding 2 becomes very small for the configuration according to FIG. 4. This means that a very small transient current is generated by the high-speed surge voltage on the winding connected to the high potential. However, the total gap length in such a configuration within the magnetic structure in FIG. 4 becomes very long, which means that the magnetic coupling between the input winding and the output winding becomes very small. Therefore, in order to pass magnetic flux through the entire core configuration, a large amount of magnetization current must be supplied from the input winding (and optionally the output winding).

[0032] FIG. 5 shows a configuration in which the intermediate core 6 carries the winding 7, and the winding 7 is connected to the capacitor 8. The self-inductance of each winding 7 forms a resonant circuit together with the connected capacitor 8. The resonant frequency can be represented by ω0. When the resonant circuit is excited at a frequency lower than ω0, the induced voltage causes a capacitive current to be supplied into the magnetic structure through the capacitor 8, thereby further magnetizing the winding 7. In this way, the required magnetization current can be supplied by capacitors distributed along the magnetic structure.

[0033] In a preferred embodiment, all the devices between each pair of gaps in FIG. 6 can be arranged inside the container 20, and as shown in FIG. 6, each container is covered by a conductive layer that forms an equipotential shell ("Faraday cage").

[0034] In the preferred embodiment shown in FIG. 6, the container 20 can be arranged inside a tube 22 filled with an insulating material 21. The tube 22 provides external insulation and creepage distance. The insulating material 21 can be a liquid such as oil, or a cast polymer material such as an epoxy or polyurethane or any other polymeric insulating material. The insulating material 21 fills the gap between the containers 20 and forms an insulator between the containers.

[0035] In another preferred embodiment shown in FIG. 7, the magnetic structure shown in FIG. 5 is disposed directly within the tube 20, which is completely filled with an insulating material 21, i.e., a liquid or polymeric material. The insulator within the gap separating the poles is formed by the insulating material 21 as shown in the lower gap in FIG. 7, or can include an insulating disk or plate (flat plate) of solid material as shown in the upper gap in FIG. 7. The tube can have an external skirt 22 to achieve a sufficient creepage distance.

[0036] In another preferred embodiment, as shown in FIG. 8, a stack of containers 20 is disposed within a metal container 23 filled with an insulating material such as oil, or a gas such as SF6, or any solid insulating material 24, and the metal container 23 is connected to ground potential. Accordingly, the high voltage output connection can be taken out from the container through the bushing 25.

[0037] Alternatively, the magnetic structure can be disposed directly within a metal enclosure such as that shown in FIG. 8, i.e., without the container 20.

[0038] Generally, the high potential connected to the relative ground of the voltage output terminals is automatically shared among a plurality of containers 20, but in some cases, specifically when a DC voltage is applied, it may be necessary to support the sharing of the voltage by providing a high resistance resistor or a conductive varnish.

[0039] In a preferred embodiment, auxiliary power in the form of a DC voltage is supplied to the high potential lead at a given level using the transformer configuration described with reference to FIG. 5. In this case, as shown in FIG. 9a, the output terminals can be connected to a rectifier 30, which uses passive diodes to convert the voltage u out into a DC voltage. However, better control of the output DC voltage can be obtained using a more sophisticated type of AC / DC converter, such as VSC (voltage source converter) technology 32. Such an alternative is shown in FIG. 9b.

[0040] In the preferred embodiment shown in FIGS. 9a and 9b, a DC voltage source, for example, the battery-assisted station power supply 33 in the switchyard, is used to supply power to the electronic DC / AC converter 31, and the electronic DC / AC converter 31 supplies an AC voltage u in to the input terminals of the transformer configuration according to FIG. 5. Generally, the DC / AC converter is of the VSC type. Such a converter can operate to supply the input voltage u in from a varying DC voltage with a constant amplitude, which is usually the case for the station auxiliary power supply in the switchyard.

[0041] When using VSC-type converters at both ground level and high potential, the synchronization signal can be transmitted between the VSCs over an optical fiber or wirelessly.

[0042] FIG. 10 shows the device, which consists of several serially connected modules. Each module generally has a "main circuit" that handles high voltages (tens of kilovolts) and a "control and protection" device marked with "C&P (control and protection)". The "control and protection" device has low-power functions for control and other service functions such as actuators for local switchgear (switching devices), cooling devices, etc. C&P requires a local auxiliary power supply. The voltage between the ends of the serially connected modules is limited by a local metal oxide varistor, i.e., MOV (metal oxide varistor) 44.

[0043] In FIG. 10, the device is connected to high potential at 40 and 41.

[0044] If each stage in the transformer has an insulation level corresponding to that defined by the MOV, the structure as shown in FIG. 5 can be used to distribute the auxiliary power to different modules according to the configuration shown in FIG. 10.

[0045] The windings 45 at each level are connected in series and are connected to the capacitor 46, which supplies the magnetizing current to the magnetic structure. Another pair of windings 47 is added on the magnetic core, and these windings are also connected in series. The output of these windings is connected to the small VSC 48 through the series capacitor 49. The DC link in the VSC supplies auxiliary power to the C&P device 43.

[0046] The entire configuration obtains power from the AC voltage u in through the series capacitor 51 and reaches the winding 50. The voltage u in can be supplied from the ground as the output voltage u out from another auxiliary power source according to FIG. 5.

[0047] In other embodiments, a transformer designated as 60 in its entirety comprises an input stage 61, an output stage 62, and an intermediate stage 63. Each of the stages 61, 62, 63 comprises at least two legs, three legs in the embodiment of FIG. 11. In the illustrated embodiment, a single intermediate stage 63 is shown. However, two or more intermediate stages 63 connected in series can exist between the input stage 61 and the output stage 62.

[0048] The input stage 61 comprises an input yoke 61c connected to three cores 61a. Each core 61 is surrounded by an input winding 61b, and each core 61 has a pole 61d facing the gap 64, and the gap 64 separates adjacent stages. The gap 64 is filled with an electrical insulator such as epoxy or any other suitable polymeric material.

[0049] Correspondingly, the output stage 62 comprises an output yoke 62c connected to three cores 62a. Each output core 62 is surrounded by an output winding 62b, and each core 62 has a pole 62d facing the gap 64 as in the input stage 61.

[0050] When there are two or more intermediate sections 63 provided, each intermediate section includes three intermediate cores 63a. Each intermediate core 63a is surrounded by an intermediate winding 63b, and each core 63a has two poles 63d, one at each end of the core. Each pole 63d faces a gap 64. In the illustrated embodiment, the upper gap 64 faces the input section 61, and the lower gap 64 faces the output section 64.

[0051] The electrical connection of the windings in FIG. 11 is shown in FIG. 12, in which the structure in FIG. 11 is included within region 70. This structure can include several intermediate sections. The input winding 61, the output winding 62, and the intermediate section windings 63 can be connected in a three-phase pattern such as the Δ connection or the Y connection shown in FIG. 12. The intermediate section is connected to a capacitor bank 65, and the capacitor bank 65 supplies a distributed magnetizing current to the structure 70.

[0052] The input power to the input winding 61 is supplied from a VSC 71, which converts DC power supplied, for example, from a station auxiliary power source within a switched mode power supply at ground potential, into an AC voltage having an appropriate frequency, and this AC voltage is supplied to the input winding 61. A series capacitor can be inserted within the input connection to the input winding 61 and / or within the output connection from the output winding 62.

[0053] The AC voltage on the output winding can be connected to a VSC 72, which converts this AC voltage into a DC voltage used as an auxiliary power source for a device connected to a high potential.

[0054] Alternatively, the output winding 62 can be connected to a passive rectifier replacing the VSC 72.

Claims

1. An input stage (61) comprising an input yoke (61c) and at least two input cores (61a), An output stage (62) comprising an output yoke (62c) and at least two cores (62a), A magnetic structure (60) comprising at least two cores (63a) and at least one intermediate stage (63), In a magnetic structure in which the input stage (61) is magnetically coupled to one of the at least one intermediate stage (63), and the output stage (62) is coupled to one of the at least one intermediate stage (63), A gap (64) having low magnetic permeability and high withstand voltage, which provides magnetic coupling between the stages (61, 62, 63), Poles (61d, 62d, 63d) that have a larger cross-sectional area than the core (61a, 62a, 63a), thereby increasing the cross-sectional area of ​​the core, wherein the poles of adjacent stages are provided on opposite faces of the gap (64), thereby providing magnetic coupling between the two faces of the gap (64), A winding (61b) is provided on the input core (61a) of the input stage (61) and is configured to acquire AC power from a power source on ground potential and transmit said AC power to the output stage, A winding (62b) is provided on the core (62a) of the output stage (62), and is configured to receive AC power from the input stage (61), supply the AC power to a power adjustment device, and supply it to a power adjustment device for supplying auxiliary power to a device coupled to a high-potential relative ground, The at least one intermediate stage (63) comprises a winding (63b) provided on the core (63a) and connected to a capacitor (65), The capacitor is a magnetic structure that supplies a distributed magnetization current to the magnetic structure (60).

2. The magnetic structure (60) according to claim 1, wherein the low permeability is a relative permeability of less than 10, preferably less than 2.

3. The magnetic structure (60) according to claim 1 or 2, wherein the high withstand voltage capability is a withstand voltage capability exceeding 5 kV / mm.

4. The magnetic structure (60) according to claim 1, comprising a plurality of intermediate stages (63), wherein all of the intermediate stages (63) are magnetically coupled to each other.

5. The magnetic structure (60) according to claim 1 or 4, wherein the cores (61a to 63a), the windings (61b, 62b, 63b), the poles (61d, 62d, 63d), and the capacitor (65) are enclosed in a metal container or a container having a conductive surface for each of the stages.

6. The magnetic structure (60) according to claim 5, wherein all of the containers are stacked inside tubes filled with an insulating material and a liquid cast polymer insulator.

7. The magnetic structure (60) according to claim 6, which is laminated within a tube filled with an insulating material, liquid, or cast polymer insulator.

8. The magnetic structure (60) according to claim 5, wherein the metal container is connected to the ground potential.

9. A magnetic structure (60) according to claim 1 or 4, having two core legs within each of the aforementioned stages (61, 62, 63).

10. A magnetic structure (60) according to claim 1 or 4, having three core legs within each of the aforementioned stages (61, 62, 63).

11. The magnetic structure (60) according to claim 1, wherein a series compensation capacitor is provided in the input stage (61) and the output stage (62).

12. The magnetic structure (60) according to any one of claims 1, 4, or 11, wherein the input stage (61) is powered by a VSC (71), and the VSC obtains power from a DC power source on ground potential, preferably from a station battery in a switchyard.

13. The magnetic structure (60) according to any one of claims 1, 4, or 11, wherein the output stage (62) supplies power to a passive rectifier (30), and the passive rectifier supplies a DC voltage used as an auxiliary power source for a device at a high potential.

14. The magnetic structure (60) according to any one of claims 1, 4, or 11, wherein the output stage supplies power to a VSC (72), and the VSC controls and adjusts a DC voltage used as an auxiliary power supply for a device at a high potential.

15. A magnetic structure (60) according to any one of claims 1, 4, or 11, wherein additional windings are provided on a plurality of intermediate stages (63), and the additional windings supply power to a plurality of VSC adjustment devices for providing auxiliary power to a plurality of modules connected in series.

16. The magnetic structure (60) according to any one of claims 1, 4, or 11, wherein the gap (64) is 1 to 2 millimeters.

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