KR20080074095A - Voltage sensors and voltage sensing methods for gas insulated switchgear - Google Patents

Abstract

A gas insulated electrical switchgear with an optical voltage sensor (46) positioned across from a conductor (10) for sensing a second voltage related to a first voltage. At least one conductive element (40 or 42) encircles the one conductor and is disposed between the optical voltage sensor (46) and the one conductor (10).

Description

VOLTAGE SENSORS AND VOLTAGE SENSING METHODS FOR GAS INSULATED SWITCHGEAR}

The present invention relates to an electrical switchgear, and more particularly, to a sensor and a sensing method suitable for a gas insulated switchgear.

Electrical power transfer / distribution systems typically provide a switch to be interposed between the transformer and the line of the system. This switch (commonly referred to as a "switch") provides a mechanism by which the transformer can be disconnected from the rest of the system, for example in response to a power surge or other type of system occurrence. Recently, the switchgear has been insulated using an insulating gas, for example SF ₆ , since the insulating properties of such gas can significantly reduce the overall size of the switchgear. Initially, a gas insulated switchgear was proposed as a single phase solution, that is, each of the three phases had a separate packaged switch associated with it. More recently, in order to further reduce the size associated with the switchgear, a three-phase, gas insulated switchgear has been proposed, one example of which is disclosed in US Patent Application Publication No. 2003 /, the disclosure of which is incorporated herein by reference. Explained in 0178891. There, three conductors, each associated with a different phase, extend through an enclosure filled with insulating gas and including a switching mechanism.

In an electrical switchgear, it may be useful to measure the current through the switchgear and the voltage between the two potentials at the switchgear, for example, a high voltage potential and ground. Different types of detectors have been used in gas insulated switchgear to accomplish this function. For example, current and voltage transformers or photocurrent and voltage detectors have been placed adjacent to each conductor to monitor current and / or voltage thereon. However, with respect to an optical voltage sensor, either (1) the distance between the conductor and the optical voltage sensor on which the voltage is being measured and (2) the insulating gas pressure introduces errors in the measured voltage. It has been found to do. The former situation can arise as a result of mechanical tolerances associated with the manufacture of GIS devices. The latter situation may arise due to changes in temperature and other factors.

One way to address these errors is to perform field calibration of the processing unit and / or the optical voltage detector to attempt to compensate for these factors. However, such calibration is time consuming and may not completely solve the dynamic fluctuations. Another way to address these errors is to use specific sensors to measure changes in gas pressure, temperature, distance to the conductor, etc., and use those measurements to compensate for the voltage readings in the light detector. However, such a solution adds significant cost to the GIS device.

Accordingly, it would be desirable to provide a voltage detector and sensing method that can automatically and accurately detect voltages in a GIS device and solve some or all of the problems described above.

According to one exemplary embodiment of the invention, a gas insulated switchgear device comprises: an enclosure having two endcaps and at least one conductor extending therethrough and carrying a first voltage; Insulating gas in the enclosure; An optical voltage detector disposed opposite the at least one conductor to sense a second voltage related to the first voltage; And at least one conductive element surrounding the at least one conductor and disposed between the optical voltage sensor and the at least one conductor, wherein the at least one conductive element comprises a capacitive division of the first voltage ( to establish a second voltage based on capacitive division).

According to another exemplary embodiment of the invention, a method for sensing a voltage associated with a conductor in a gas insulated switchgear comprises providing a first voltage associated with the conductor extending through the gas insulated switchgear, capacitive to the first voltage. Splitting to generate a second voltage associated with the conductor, optically sensing the second voltage, and determining the first voltage based on the second voltage.

According to yet another exemplary embodiment of the present invention, a system for sensing a voltage associated with a conductor in a gas insulated switchgear comprises means for providing a first voltage associated with the conductor extending through the gas insulated switchgear, the first voltage. Means for capacitively dividing to generate a second voltage associated with the conductor, means for optically sensing the second voltage, and means for determining the first voltage based on the second voltage.

The accompanying drawings illustrate exemplary embodiments of the invention.

1 shows a single phase, gas insulated switch device.

2 shows a ring comprising an optical voltage detector.

3 shows the ring of FIG. 2 inserted into a position for measuring the voltage of an associated conductor between two portions of a GIS device.

4 illustrates an optical voltage sensor in accordance with an exemplary embodiment of the present invention.

5 is a flow chart illustrating a method of optical voltage sensing in accordance with an exemplary embodiment of the present invention.

6A-6C illustrate an optical voltage sensor in accordance with another exemplary embodiment of the present invention.

DETAILED DESCRIPTION The following detailed description of the invention refers to the accompanying drawings. Like reference numerals in different drawings identify the same or similar components. In addition, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

1 illustrates a single phase, gas insulated switchgear (GIS) device 1 in which an exemplary embodiment of the invention may be implemented. There, the GIS device includes a bus bar 2 for each pole, a disconnect switch 3, a ground switch 4, 5 and a circuit breaker 6. Each of the three enclosures 11 is associated with a single phase of the GIS device 1, filled with an insulating gas, for example SF ₆ gas, and extending therethrough (not shown in FIG. 1) 10). The enclosure also includes the mechanical part of the switch associated with the electrical conductor 10 that conducts current through the switch 1 to the GIS device 1 and its respective phases, for example contacts, drive mechanisms and the like.

One method for optically measuring the voltage associated with electrical conductor 10 involves placing a Pockels cell in an electric field generated by the conductor, passing light through the Pockels cell, and then polarizing the light. To monitor change. One example of this technique is illustrated in FIGS. 2 and 3. There, a ring 13 is inserted between the two portions 14 and 14 'of the outer conductor forming the enclosure 11 in the circuit breaker 6 region. FIG. 3 is a cross section of the ring 13 and the outer conductor of the enclosure 11 taken along section line B-B of FIG. 2. The ring 13 and the outer conductor portions 14 and 14 ′ can be connected together via flanges 12 and bolts 27. The ring 13 comprises a metallic L-shaped portion 15 and a non-metallic inner ring 16 disposed in the hollow of the L-shaped portion 15. . The nonmetal inner ring 16 can be made from a dielectric material, for example a resin. The Pockels cell 25 is mounted in a bore 17 made in the inner ring 16. The optical fiber 24 extends from the control unit 26 through the bore 17 and the Pockels cell 25, which control unit 26 returns an optical source and returned light (not shown). Processing components and circuitry for measuring; It should be noted that this configuration is merely an example of an arrangement for placing an optical voltage sensor adjacent to a conductor in a GIS device, and that the present invention can be used for GIS devices with different configurations.

Pockels cells have a polarization of light based on the intensity of the electric field in which the Pockels cells are placed, as light passes through electro-optic crystals (Pockels cells). It operates on the principle of changing to elliptical polarization. One example of a Pockels cell voltage sensor is found in US Pat. No. 5,029,273, the disclosure of which is incorporated herein by reference. Thus, the light reflected from the Pockels cell 25 is evaluated in the control unit 26 to determine its respective polarization change, from which the magnitude of the electric field associated with the electrical conductor 10 (and the Voltage) can be determined.

However, as mentioned in the background section of this specification, the accuracy of the voltage sensing mechanism and method illustrated in FIGS. 2 and 3 may be affected by several variables. First, the electric field measurement made by Pockels cell 25 depends on the distance between Pockels cell 25 and electrical conductor 10. Thus, if this distance changes, the voltage measurement will also change, which, among other things, depends on the mechanical tolerances of manufacture used to secure the electrical conductor 10 in its respective enclosure 11. Will depend. Second, the electric field measurement made by the Pockels cell 25 also depends on the pressure of the insulating gas (eg SF ₆ ) contained in the containment 11. This pressure may also change due to changes in temperature or the like, which results in another potential inaccuracy for the voltage sensing arrangements shown in FIGS. 2 and 3.

Exemplary embodiments of the invention include (1) the distance between a conductor in a GIS device whose voltage is being measured and an optical voltage sensor and / or (2) an insulating gas in the enclosure of the conductor whose voltage is being measured (eg For example, SF ₆ ) provides a voltage sensing arrangement and method to compensate for changes in pressure. In FIG. 4 an example conceptualized longitudinal cross-sectional view of an enclosure 11 of a GIS device in accordance with an exemplary embodiment of the present invention is illustrated.

There, two wire rings 40 and 42 are embedded in the dielectric material 44, which is also embedded with an optical voltage detector 46 for detecting the voltage Vout associated with the central conductor 10. . Wire rings 40 and 42 may be connected by wire 43 in the region of optical voltage detector 46 and may be disposed on either side of optical voltage detector 46. As shown in FIG. 4, the rings 40 and 42 may maintain the same distance from the optical voltage detector 46, although this symmetry is not required. In FIG. 4, reference numerals 10, 11, 12, 14, 14 ′ and 15 refer to components similar to those described above with respect to FIG. 3 and are not elaborated herein. In addition, some components associated with the complete device, such as the optical fiber, the light source, and the digital processing / control unit associated with the optical voltage detector 46 have been omitted to simplify the figure.

The capacitance associated with the wiring rings 40 and 42 may be determined by either the distance between the photovoltage sensor 46 and the central conductor 10 and the change in insulation gas pressure due to, for example, a temperature change. Used to automatically compensate for differences in both. For example, since two wire rings 40 and 42 surround the center conductor 10, the total capacitance C1 between the center conductor 10 and the two wire rings 40 and 42 is the photovoltage detector 46. Minor changes in the position of the center conductor 10 with respect to will not change significantly. This is because if the central conductor 10 of a particular GIS device is closer to (or farther from) the illustrated side of the rings 40 and 42 adjacent to the outer (ground) conductors 14 and 14 'due to mechanical tolerances. For it will be farther away (or closer) from the other side of the ring (not shown). Capacity C1 will also be affected by the pressure of the insulating gas.

The second dose C2 will be present between each of the rings 40, 42, the L-shaped metal part 15 and the flange / outer conductors 12, 14. This second capacitance C2 will also vary based on the gas pressure of the insulating gas operating as a dielectric between the outer metal surfaces of the capacitor. Moreover, the capacitors C1 and C2 establish a capacitive voltage divider, so that the voltage sensed by the light detector 46 will be a function of the voltage V associated with the capacitors C1, C2 and the center conductor 10. Therefore, the light detector 46 will detect the voltage Vout as shown in Equation 1 below.

Both capacities C1 and C2 are functions of gas pressure (and temperature) and therefore maintain proportional relationship with each other as the gas pressure changes, so that the detection voltage Vout is virtually independent about it, that is to say, exemplary of this invention. Embodiments include the gas pressure and temperature (as well as the distance between the light detector 46 and the center conductor 10 due to surrounding the center conductor 10 with the rings 40, 42, as described above). Automatically compensate.

It will be appreciated that the present invention can be implemented in many different variations of the exemplary embodiments described above. For example, the physical location of the optical voltage detector 46 or the way it is mechanically integrated into the outer conductor of the GIS device may vary. Moreover, the conductive component used to establish the capacitive voltage divider may take any desired form, without having to be formed from two interconnected rings. More generally, a method for optically sensing a voltage associated with a conductor in a GIS device is described in the flowchart of FIG. 5. There, in step 500, the GIS device provides a first voltage associated with the conductor extending through the gas insulated switchgear. In step 502, the first voltage is divided capacitively to generate a second voltage associated with the conductor. This second voltage is then optically sensed at step 504, for example by a Pockels cell. Next, in step 506, for example, by using Equation 1 above, the first voltage delivered by the central conductor may be determined based on the second voltage.

As can be seen from the above description, the voltage sensor according to an exemplary embodiment of the present invention can be generally modeled as shown in FIG. 6A. Therein, the voltage sensing arrangement, generally labeled as reference number 600, consists of two conductors of different electrical potentials (e.g., external ground conductor 602 and positive conductor internal conductor 604) and Two continuous layers 606 and 608 (eg, layer 606) of substantially dielectric material having different real and / or imaginary dielectric constants ε 1, ε 3 sandwiched between two conductors 602 and 604, respectively. Dielectric layer 44 described above, and layer 608 may comprise an insulating gas, for example SF ₆ ). In-border region 610 is a photoelectric field (not shown in this figure) disposed in inner layer 606 having a real and / or imaginary dielectric constant ε2 that may be different from the dielectric constant ε1 of peripheral layer 608. Includes a sensor. Region 610 may comprise a gel surrounding the field detector or may be a simple pocket of air to which the detector is connected as described above. The dimension of the boundary region 610 is such that the electric field change at the detector position caused by the change in real and / or imaginary dielectric constant of the peripheral layer relative to the dielectric constant of the region within the boundary and other layers is minimized. to be.

If the permittivity epsilon 1 of layer 606 changes, the electric field E3 in layer 608 will change through meeting the boundary conditions of the Laplace equation governing layers 606, 608 and 610. More specifically, defining the Laplace equation is based on the theory of electrostatic field, where the tangential field Et across the boundary is continuous, and the normal electric flux across the boundary, Dn = εEn, Has a boundary condition indicating that it is continuous. This means that the field detector disposed in the area 610 may be sensitive to changes in the dielectric constant caused by, for example, temperature changes.

To better understand the relationship between the dimensions of the intra-boundary region 610 and the behavior of E2 for the change in dielectric constant epsilon 1, the voltage sensor can be broken down into two basic building blocks shown in FIGS. 6B and 6C. First, considering FIG. 6B in which the height of the intra-boundary region 610 extends completely across the layer 606 between the outer conductor 602 and the layer 608, as ε 1 increases, E 2 will decrease. . Moreover, reducing the width of region 610 will amplify this effect. Now, considering FIG. 6C in which the width of the intra-boundary region 610 extends to the maximum, as ε1 increases, E2 will increase. Moreover, reducing the height of region 610 will amplify this effect.

The effects discussed above for the cases shown in FIGS. 6B and 6C are contrary. Since the example of the voltage sensor of FIG. 6A is a combination of these two cases, the height and width of the intra-boundary region 610 may have the effect that the above-mentioned effect has on the intra-boundary region 610 for the change in permittivity of the layer 606. It can be chosen to virtually cancel each other out while minimizing the electric field E2 sensitivity. With the dimensions so selected, the field detector (eg, Pockels cell) disposed in the boundary region 610 is a conductor 602 that is substantially insensitive to changes in the dielectric constant of the layer 606 due to, for example, temperature changes. And voltage (potential) measurement between 604.

The illustrative embodiments described above are intended to illustrate rather than limit the invention in all respects. Accordingly, the present invention is capable of many variations in detailed implementation that can be derived by those skilled in the art from the description contained herein. All such changes and modifications are considered to be within the spirit and scope of the invention as defined by the following claims. Components, operations, or instructions used in the descriptions of the present application should not be considered indispensable or essential for the present invention unless explicitly stated as such. Also, the article "any one (a)" is intended to include one or more items.

Claims (20)

A gas insulated switchgear device, An enclosure having at least one conductor extending through said gas insulated switchgear device and carrying a first voltage; Insulating gas in the containment device, An optical voltage detector disposed opposite said at least one conductor for sensing a second voltage related to said first voltage; At least one conductive component surrounding the at least one conductor and disposed between the optical voltage sensor and the at least one conductor Including, And said at least one conductive component is operative to establish said second voltage based on capacitive division of said first voltage. The method of claim 1, And said at least one conductive component comprises two rings each surrounding said at least one conductor. The method of claim 2, A gas insulated switchgear device in which a wire connects the two rings in an area adjacent the optical voltage sensor. The method of claim 1, A first capacitance C1 is established between the at least one conductor and the at least one conductive component, and a second capacitance C2 is established between the at least one conductive component and an outer conductor forming the enclosure, and The second voltage Vout is represented by the following equation: Vout = V * C1 / (C1 + C2) And the gas insulated switchgear device according to the first voltage V. The method of claim 4, wherein And a processing unit connected to the optical voltage detector for determining the first voltage based on the second voltage. The method of claim 5, And said determined first voltage is substantially unaffected by a change in pressure of said insulating gas. A method for sensing a voltage associated with a first conductor in a gas insulated switchgear, Providing a first voltage associated with the first conductor extending through the gas insulated switchgear; Generating a second voltage associated with the first conductor by capacitively dividing the first voltage using a second conductor surrounding the first conductor; Optically sensing the second voltage; Determining the first voltage based on the second voltage Voltage sensing method comprising a. The method of claim 7, wherein Partitioning the capacitively, Providing as the second conductor two rings each of which surrounds the first conductor adjacent a light detector. The method of claim 8, The light detector includes a Pockels cell. The method of claim 8, Electrically connecting the two rings in an area adjacent the optical voltage sensor. The method of claim 7, wherein Establishing a first capacitance C1 between the first conductor and the second conductor, Establishing a second capacitance C2 between the second conductor and the outer conductor More, The second voltage Vout is represented by the following equation: Vout = V * Cl / (Cl + C2) And a voltage sensing method associated with said first voltage V. The method of claim 7, wherein And the determined first voltage is substantially unaffected by a change in pressure of the insulating gas. A system for sensing a voltage associated with a first conductor in a gas insulated switchgear, Means for providing a first voltage associated with the first conductor extending through the gas insulated switchgear; Means for capacitively dividing the first voltage to generate a second voltage associated with the first conductor using a second conductor surrounding the first conductor; Means for optically sensing the second voltage; Means for determining the first voltage based on the second voltage Voltage sensing system comprising a. The method of claim 13, The means for partitioning capacitively, And a two rings each operating as said second conductor surrounding said first conductor adjacent a light detector. The method of claim 14, And the light detector comprises a Pockels cell. The method of claim 14, And means for electrically connecting the two rings in an area adjacent the optical voltage sensor. The method of claim 13, Means for establishing a first capacitance C1 between the first conductor and the second conductor, Means for establishing a second capacitance C2 between the second conductor and the outer conductor More, The second voltage Vout is represented by the following equation: Vout = V * Cl / (C1 + C2) And a voltage sensing system associated with said first voltage V. The method of claim 13, The determined first voltage is substantially unaffected by a change in pressure of the insulating gas. A gas insulated switchgear device, An enclosure having at least one conductor extending through said gas insulated switchgear device and carrying a first voltage; Insulating gas in the containment device, A dielectric component in which a pocket is formed, the pocket comprising an optical voltage detector disposed opposite the at least one conductor to sense an associated voltage Including, Wherein the height and width of the pocket are selected to reduce the sensitivity of the optical voltage sensor to changes in dielectric constant of the dielectric component. The method of claim 19, And said optical voltage detector is an electric field detector.

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