JPH0538855U - Voltage transformer for gas insulated switchgear - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the reliability and ease of maintenance of the voltage transformer used in the gas insulated switchgear for ultra high voltage. A voltage dividing electrode container 5 is connected to a metal container 1 of a gas insulated switchgear via an insulating spacer 2, and a high voltage electrode 16 connected to a main circuit conductor 3 of the gas insulated switchgear is placed in the voltage divider electrode container 5. To place. A cup-shaped voltage dividing electrode 17 concentrically surrounding the high-voltage electrode 16 is provided in the voltage dividing electrode container, and an instrument transformer is installed in a tank 9 connected to the voltage dividing electrode container via an insulating spacer 8 and a connecting conduit 7. The container body 10 is stored. The voltage dividing electrode 17 and the primary terminal of the instrument transformer main body 10 are connected by the connection conductor 15. The same gas as the insulating gas used in the gas-insulated switchgear is enclosed in the tank and the connecting pipeline.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a voltage transformer for a gas insulated switchgear suitable for use in an ultrahigh voltage (500 KV or more) gas insulated switchgear.

[0002]

[Prior Art]

 Conventionally, amplification type capacitor type voltage transformers (CVT) and winding type gas insulated voltage transformers (VT) have been used as voltage transformers for gas insulated switchgear for ultra high voltage.

The amplifying CVT is a voltage dividing electrode provided so as to concentrically surround the main circuit conductor in the conduit of the gas insulated switchgear, and an electrostatic discharge between the voltage dividing electrode and the main circuit conductor. Capacitance and voltage division It is composed of an amplification unit that amplifies the main circuit voltage divided by the electrostatic capacitance between the electrode and the conduit.

Further, in a wound-type gas-insulated voltage transformer, a transformer main body for an instrument in which a primary coil and a secondary coil are wound around an iron core is housed in a container, and the container is filled with an insulating gas. Have a structure.

[0005]

[Problems to be solved by the device]

 The amplification type CVT has many problems in that it uses a lot of electronic parts in the amplification section, and thus has low reliability for long-term use and shortens the maintenance inspection cycle. Moreover, the maintenance and inspection of the amplification section is complicated and time-consuming, so the cost required for the maintenance and inspection was unavoidable. In addition, in an amplification type CVT, it was necessary to install an amplification section and a large-capacity stabilized power supply inside a place other than the installation location of the gas insulated switchgear, so the entire voltage transformer became a very large facility. There was a problem that the equipment cost was high. Further, since a large amount of power is constantly consumed to operate the amplifier, it is inevitable that the running cost will increase. In addition, in a wire-wound gas-insulated voltage transformer, an ultrahigh voltage is directly applied to the primary coil, so the size of the instrument transformer main body becomes large, and the container for accommodating the instrument transformer main body is large. I cannot avoid becoming. Therefore, there is a problem that a large facility and a lot of man-hours are required for the assembling, resulting in a significant increase in cost. An object of the present invention is to provide a voltage transformer for a gas insulated switchgear which solves the above problems.

[0006]

[Means for Solving the Problems]

 In the present invention, the metal voltage dividing electrode container connected to the metal container of the gas insulated switchgear via the insulating spacer and the main circuit conductor of the gas insulated switchgear is arranged inside the voltage divider electrode container. A high-voltage electrode, a cup-shaped voltage-dividing electrode provided so as to concentrically surround the high-voltage electrode in the voltage-dividing electrode container, and a tank connected to the voltage-dividing electrode container via a gas dividing means and a connecting conduit. The main body of the instrument transformer is housed in the tank, and a gas-insulated instrument transformer in which the same insulating gas as the insulating gas used for the gas-insulated switchgear is enclosed is provided in the tank. Was connected between the voltage dividing electrode and the primary terminal of the instrument transformer body by a concentrically extending connecting conductor. The connection conduit may be made of metal, and may have an insulation strength that can withstand the piezoelectric voltage generated between the voltage dividing electrode and the ground. According to the present invention, with the above configuration, the capacitance C1 between the voltage dividing electrode and the high voltage electrode, the capacitance C2 between the voltage dividing electrode and the voltage dividing electrode container, and the connecting conductor A voltage divider circuit that divides the voltage E1 (primary voltage of the entire voltage transformer) of the main circuit conductor (primary high voltage terminal of the voltage transformer) by using the capacitance C3 between the connection line and The voltage E2 = E1 {(C1) / (C1 + C2 + C3)} that is constructed and divided by this voltage dividing circuit is used as the primary voltage of the transformer for gas insulation instrument. The gas dividing means may be any one as long as it divides the gas space in the partial pressure container from the gas space in the connecting pipeline, and the insulating spacer normally used in the gas insulation switchgear is used as the gas dividing means. Can be used as Also, a capacitor bushing can be used as the gas dividing means in order to increase the capacitance C3.

[0007]

[Action]

 With the above configuration, the measuring medium and the gas-insulated switchgear share the same insulating medium, which facilitates maintenance and inspection. Also, with the above configuration, if the insulation distance between the voltage dividing electrode and the main circuit conductor is set appropriately, it is assumed that the voltage dividing electrode and the voltage dividing electrode container or between the connecting conductor and the connecting conduit are temporarily set. Even if an abnormality such as a ground fault occurs between the instrument transformer main body and the tank, the power can be continued through the main circuit conductor, so a power failure can be avoided. Furthermore, in the above configuration, the high-voltage side of the voltage transformer is in the same gas space as the gas-insulated switchgear, and the instrument transformer side is also insulated by the same insulating gas as the gas-insulated switchgear. The reliability can be increased. Therefore, the maintenance inspection cycle can be lengthened. Moreover, unlike the amplification type voltage transformer, it does not require complicated maintenance and inspection work, so the cost required for maintenance and inspection can be reduced. In addition, the voltage-divided voltage is input to the gas-insulated voltage transformer, so the voltage-insulated voltage transformer is used as a standard for gas-insulated switchgear with a low voltage class (for example, 154 KV or less). You can use a small one. Therefore, it is possible to reduce the size of the entire voltage transformer and to reduce the cost, as compared with the case of using a winding-type gas-insulated voltage transformer in which an ultrahigh voltage is directly input to the primary side. In addition, if the connection pipeline is made to have insulation strength that can withstand the partial voltage, it must be connected to the primary high-voltage terminal (any of the terminals provided on the gas-insulated switchgear side and connected to the main circuit conductor). A characteristic test (equivalent circuit test) of the voltage transformer can be performed by connecting the voltage dividing electrode container and applying a test voltage corresponding to the divided voltage between the connection point and ground. If the characteristic test is performed by such a method, the test equipment will be far more extensive than the case where the characteristic test is performed by applying a high voltage equivalent to the main circuit voltage of the gas insulated switchgear between the primary high voltage terminal and ground. Can be easy.

[0008]

Embodiment 1 FIG. 1 shows a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a metal container which constitutes a part of an outer shell container of a gas insulating and opening / closing device. An insulating spacer 2 is attached to the end portion, and the terminal portion 3 of the main circuit conductor of the gas insulated switchgear is connected to the through conductor 4 of the insulating spacer 2. SF ₆ gas G is sealed in the metal container 1 at a predetermined pressure.

Reference numeral 5 denotes a metal partial pressure electrode container, and the partial pressure electrode container includes a main body 501 formed in a cylindrical shape and an end member attached so as to hermetically close an opening at one end of the main body 501. It consists of 502. The end member 502 integrally has a flange portion 502a and a connecting pipe portion 502b, and the flange portion 502a is hermetically connected to the opening of the main body 501. The flange at the end of the connecting pipe portion 502b of the end member 502 is hermetically connected to the insulating spacer 2. A hole 501a is provided at the center of the bottom of the voltage dividing electrode container 5, and a flange provided at one end of the metallic connecting conduit 7 is connected to this hole via an insulating spacer 8. The other end (lower end in this example) of the connecting pipe 7 is connected to an opening provided in the upper portion of a box-shaped or cylindrical tank 9, and the tank main body 10 of the instrument is housed in the tank 9. The transformer main body 10 for an instrument comprises an iron core 11 around which a primary coil 12 and a secondary coil 13 are wound, and a shield 14 provided so as to surround the primary coil 12 has a non-grounded terminal of the primary coil. Is connected, and the shield 14 serves as the primary terminal of the instrument transformer main body. The connecting pipe 7 and the tank 9 have an airtight structure, and the inside of each of them constitutes a common gas space, and SF6 gas G has a predetermined pressure in the gas space and the partial pressure electrode container 5. It is enclosed in.

A lower end of a connecting conductor 15 concentrically arranged in the connecting conduit 7 is connected to the shield (primary terminal) 14 of the instrument transformer main body 10. The upper end of the connection conductor 15 penetrates the insulating spacer 8 and is introduced into the voltage dividing electrode container 5.

A rod-shaped high-voltage electrode 16 is concentrically arranged in the voltage dividing electrode container 5, and a rear end portion of the high-voltage electrode 16 is connected to the penetrating conductor 4 of the insulating spacer 2. The tip portion 16a of the high voltage electrode 16 is formed in a spherical shape.

A cup-shaped voltage dividing electrode 17 concentrically surrounding the high voltage electrode 16 is arranged in the voltage dividing electrode container 3, and the voltage dividing electrode 17 has a bottom portion connected through the insulating spacer 7. The upper end of the conductor 15 is electrically and mechanically connected and supported.

A terminal plate 18 is attached so as to airtightly close an opening provided at an upper portion of a side surface of the tank 9, and terminals 19 and 20 and a ground terminal 21 are provided by hermetically penetrating the terminal plate 18. ing. The terminals 19 and 20 are connected to both ends of the secondary coil 13 via lead wires (not shown). The ground terminal 21 is connected to the ground side terminal of the primary coil via a lead wire (not shown). One end of a resonance reactor L for improving the transformation ratio is connected to the terminal 19, and an output terminal 22 is drawn out from the other end of the resonance reactor L. The iron resonance suppressing load ZD is connected between the terminal 20 and the output terminal 22, and the output terminal 23 is drawn from the terminal 20. The ground terminal 21 is grounded through a ground wire. A secondary terminal box 24 for accommodating a terminal plate 18 and a resonance reactor L connected to the secondary terminals, a load ZD for suppressing iron resonance, and the like is attached to the upper side surface of the tank 9. A gas-insulated voltage transformer VT is constituted by the tank 9 and the voltage-measured transformer main body 10 housed inside the tank 9.

In the above voltage transformer, the capacitance between the high voltage electrode 16 and the voltage dividing electrode 17 is C1, the capacitance between the voltage dividing electrode 17 and the voltage dividing electrode container 5 is C2, and the connecting conductor is If the electrostatic capacity between 15 and the connecting conduit 7 is C3, the equivalent circuit is as shown in FIG. 5, and the voltage divided by the electrostatic capacity C1 and the capacitors C2 and C3 is used for the measuring instrument. It is input to the primary coil 12 of the transformer 10. Here, if the frequency of the voltage to be measured is f, the ground voltage of the high voltage electrode 16 (primary voltage of the voltage transformer) is E1, and the divided voltage (primary input voltage of the instrument transformer 10) is E2, E2 is It is given by E2 = E1 {C1 / (C1 + C2 + C3)}. In this case, the characteristics of the voltage transformer are better as the value of f ² · C 1 · E 1 · E 2 is larger. Therefore, if the frequency cannot be changed, the higher the capacitance C1, the primary voltage E1 and the divided voltage E2, the better the characteristics obtained.

The higher the divided voltage E2 is, the better the characteristics are obtained. However, when the divided voltage E2 is increased, it is necessary to use the instrument transformer main body 10 having a high primary voltage. The cost of the instrument transformer increases as the primary voltage rises. In order to reduce the cost, it is better to use the most commonly used standard gas-insulated instrument transformer, and when constructing a voltage transformer for 1100 KV, gas insulation with a phase-to-phase voltage of 154 KV to 66 KV is required. It is recommended to use the gas-insulated instrument transformer that is normally used in switchgear.

Further, in the above-described embodiment, between the voltage dividing electrode 17 and the voltage dividing electrode container 5, between the connecting conductor 15 and the connecting line 7, or between the instrument transformer main body 10 and the tank 9. The insulation distance between the voltage dividing electrode 17 and the high voltage electrode 16 is set so that the main circuit can be insulated in the gas space inside the voltage dividing electrode 17 even if the space is short-circuited. .. Therefore, even if a ground fault occurs between the voltage dividing electrode 17 and the voltage dividing electrode container 5, between the connecting conductor 15 and the connecting conduit 7, between the instrument transformer main body 10 and the tank 9, and the like, The main circuit can continue to be energized and power failure can be avoided.

FIG. 2 shows another embodiment of the present invention. In this embodiment, a high voltage electrode 16 having a shape in which the tip of a round bar is simply rounded is used. Further, in this embodiment, an expansion joint is used as the connection conduit 7, and a primary terminal (for example, a tulip contact) 30 having a structure in which the lower end of the connection conductor 15 is slidably fitted to the shield 14 of the transformer VT. Is attached, and the lower end of the connecting conductor 15 is slidably connected to the primary terminal 30. Further, in this example, the connecting conductor 15 is divided into a through conductor 15A penetrating the insulating spacer 8 and a connecting pipe inner conductor 15B extending in the connecting pipe 7, and the through conductor 15A is connected via the conductor connecting portion 15C. It is slidably connected to the conductor 15B in the connecting conduit.

According to this structure, when a relative displacement occurs between the tank 9 and the gas-insulated switchgear, and the distance between the primary terminal of the transformer and the insulating spacer 8 changes, the contact is prevented. Since the connecting conductor 15 is relatively displaced with respect to the primary terminal of the transformer, and the connecting conduit 7 expands and contracts to absorb the change in the distance, due to unequal subsidence of the installed base, earthquake, etc. It is possible to prevent the insulating spacer 8 from being damaged due to excessive stress.

When the connecting conduit 7 is configured to be expandable and contractable, the electrostatic capacitance C3 between the connecting conductor 15 and the connecting conduit 7 is adjusted by adjusting the length of the connecting conduit 7. Therefore, the divided voltage (the primary voltage voltage input to the transformer VT) can be finely adjusted. Therefore, when the divided voltage varies due to the mounting tolerances of the divided electrode container 5, the connecting conduit 7, the divided electrode 17, the connecting conductor 15, etc., the divided voltage can be easily adjusted to a desired value. be able to.

In the embodiment shown in FIG. 2, a conductor connecting portion 15C is used so that the conductor 15B in the connecting conduit can be slidably connected. However, the conductor connecting portion 15C does not allow the conductor 15B to slide. You may use. When the conductor connecting portion 15C is one that allows the conductor 15B to slide, the primary terminal 30 may be one that does not allow the conductor 15 to slide.

Further, also in the embodiment of FIG. 1, the connection conductor 15 can be divided into the through conductor 15A and the connection conduit inner conductor 15B.

In the present invention, the shape of the tip of the high voltage electrode 16 may be any shape as long as it does not disturb the electric field distribution, and may be, for example, the shape shown in FIG.

Further, as shown in FIG. 3, in the annular space formed between the connection conductor 15 and the connection conduit 7, a laminated body of a dielectric film and a plurality of electrodes surrounding the connection conductor is formed. It is also possible to arrange the voltage dividing auxiliary capacitor 31. This voltage division auxiliary capacitor has a structure similar to that of a capacitor core provided in the bushing in a commonly used capacitor bushing. As the dielectric film, polyethylene, polypropylene, polystyrene, polyethylene terephthalate, or the like suitable for use in SF ₆ gas can be used. The voltage dividing auxiliary capacitor 31 is formed such that the cross-sectional shape of its half portion is trapezoidal. Further, the capacitor 31 is provided so as not to create a gap between the inner peripheral portion of the capacitor 31 and the connecting conductor 15 and between the outer peripheral portion thereof and the connecting conduit 7. In this case, the outermost electrode of the capacitor 31 may be electrically connected to the connection conduit 7, or may only face the connection conduit 7 via the dielectric layer.

In the embodiment of FIG. 1 or 2, if the divided voltage E2 = E1 {(C1) / (C1 + C2 + C3)} is reduced to use a small transformer VT, the electrostatic capacitance In order to increase the quantity C3, it is necessary to lengthen the length of the connecting line 7 considerably.

On the other hand, as in the embodiment shown in FIG. 3, when the voltage dividing auxiliary capacitor 31 is arranged between the connection conductor 15 and the connection conduit 7, the capacitor separates the connection conductor and the connection conduit. Since the capacitance between them can be increased, the length of the connecting conduit 7 can be shortened.

In the embodiment of FIG. 3, the capacitor 31 is arranged between the connecting conductor 15 and the connecting conduit 7, but the permittivity is higher than that of SF ₆ gas between the connecting conductor 15 and the connecting conduit 7. By arranging a dielectric (having the same contour shape as the capacitor 31 of FIG. 3) made of a laminated body of dielectric films, the electrostatic capacitance C3 between the connecting conductor 15 and the connecting conduit 7 is increased. May be.

Although the capacitor 31 is provided with a plurality of electrodes surrounding the connection conductor 15 in the embodiment of FIG. 3, only one electrode may be provided.

In each of the above-described embodiments, the insulating spacer 8 is used as the gas dividing means for dividing the gas between the partial pressure electrode container 5 and the connection conduit 7, but other means, for example, instead of the insulating spacer, may be used. Bushings can also be used.

It is also possible to use a condensing bushing as a gas dividing means for dividing the gas between the partial pressure electrode container 5 and the connecting conduit 7. A capacitor bushing is a capacitor core in which a large number of electrodes that concentrically surround the center conductor are stacked with a dielectric layer in between, and the grounding terminal is led out from the outermost electrode of the capacitor core. Has been. The ground terminal is electrically connected to the connection line 7. When the capacitor bushing is used as the gas dividing means between the voltage dividing electrode container and the connecting conduit, the central conductor of the bushing can be used as the connecting conductor 15.

As described above, when the capacitor bushing is used as the gas dividing means, the capacitance between the connection conductor 15 and the connection conduit 7 can be increased by the capacitor bushing, and therefore the connection can be made. The pipe line 7 can be shortened. Further, since the means for increasing the electrostatic capacity C3 also serves as a means for separating the gas between the voltage dividing electrode container 5 and the connecting conduit 7, the structure can be simplified.

When performing a characteristic test of the voltage transformer, it is provided between the terminal (corresponding to the primary high-voltage terminal of the voltage transformer) provided on the gas insulated switchgear side and connected to the main circuit conductor 3 and the ground. By applying the test voltage E1 corresponding to the main circuit voltage, the test voltage E1 is applied to both ends of the series circuit of the capacitors C1 and C2 in FIG. 5, whereby the predetermined divided voltage E2 is applied to both ends of the capacitor C2. = E1 {C1 / (C1 + C2)} is generated. In this case, a long bushing is required to apply the test voltage E1 and large-scale test equipment is required.

Therefore, the circuit of FIG. 5 is rewritten as shown in FIG. 6 by Thevenin's theorem, and further rewritten as shown in FIG. 7, and a characteristic test (equivalent circuit test) is performed using the equivalent circuit of FIG. It is considered to carry out an examination. When performing this equivalent circuit test, the primary high-voltage terminal on the gas-insulated switchgear side is connected to the voltage dividing electrode container 5, and a test voltage corresponding to the voltage dividing voltage is applied between the connection point and ground. ..

If the equivalent circuit test as described above can be performed, if a test voltage equal to the divided voltage E2 (for example, 66 / √3 to 154 / √3KV in the case of an ultrahigh pressure gas insulated switchgear) is applied. Since it is good, the characteristic test can be performed with simple test equipment.

However, as in the embodiment shown in FIGS. 1 to 3, when the voltage dividing electrode container 5 is electrically connected to the tank 9 of the instrument transformer through the metal connecting pipe 7. When a test voltage corresponding to the divided voltage is applied between the connection point between the primary high voltage terminal and the voltage dividing electrode container 5 and ground, the potential of the transformer tank 9 rises and the secondary lead terminal Since it exceeds the withstand voltage, etc., a flashover will occur. Therefore, in the embodiment shown in FIGS. 1 to 3, the equivalent circuit test cannot be performed.

FIG. 4 shows an embodiment capable of performing the above-mentioned equivalent circuit test. In this embodiment, the connecting conduit 7 is formed of FRP (fiber reinforced plastic), porcelain or the like. This connecting pipe has sufficient insulation strength to withstand the divided voltage. The other points are the same as in the embodiment of FIG.

As shown in FIG. 4, when the connecting pipe 7 is made to have insulation strength to withstand the divided voltage, the tank 9 is grounded and the connection point between the primary high voltage terminal and the divided electrode container is grounded. An equivalent circuit test can be performed by applying a test voltage to. However, in the embodiment of FIG. 4, the divided voltage is E1 {C1 / (C1 + C2)}, which is higher than the divided voltage applied to the primary side of the transformer VT in the embodiment of FIGS. This makes them equivalent.

[0037]

[Effect of the device]

 As described above, according to the present invention, since the insulating medium of the instrument transformer and the gas insulated switchgear are common, maintenance and inspection can be facilitated.

Further, according to the present invention, by appropriately setting the insulation distance between the voltage dividing electrode and the main circuit conductor, it is possible to temporarily connect the voltage dividing electrode and the voltage dividing electrode container or the connecting conductor. Even if an abnormality such as a ground fault occurs between the pipe and the like, there is an advantage that the main circuit conductor can continue to be energized.

Further, according to the present invention, the high-voltage side is in the same gas space as the gas-insulated switchgear, and the instrument transformer side is also insulated with the same insulating gas as the gas-insulated switchgear. It has the advantages of high reliability and a long maintenance cycle.

Further, according to the present invention, since complicated maintenance and inspection work is not required unlike the amplification type voltage transformer, the cost required for maintenance and inspection can be reduced.

Further, in the present invention, since the divided voltage is input to the gas-insulated voltage transformer, the gas-insulated switchgear is used as a standard for the gas-insulated switchgear having a low voltage class. A small one can be used. Therefore, it is possible to reduce the size of the entire voltage transformer and to reduce the cost as compared with the case of using a winding type gas-insulated voltage transformer in which an ultrahigh voltage is directly input to the primary side.

Further, according to the invention described in claim 2, since the connection conduit is provided with the insulation strength to withstand the divided voltage, the connection is provided between the connection point between the primary high voltage terminal and the divided electrode container and the ground. An equivalent circuit test of the voltage transformer can be performed by applying a test voltage corresponding to the piezo voltage, and there is an advantage that the characteristic test of the voltage transformer can be performed with simple equipment.

[Brief description of drawings]

FIG. 1 is a sectional view showing an essential part of an embodiment of the present invention.

FIG. 2 is a sectional view showing an essential part of another embodiment of the present invention.

FIG. 3 is a sectional view showing a main part of still another embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a main part of still another embodiment of the present invention.

FIG. 5 is a circuit diagram showing an equivalent circuit of an embodiment of the present invention.

6 is a circuit diagram showing an equivalent circuit obtained by rewriting the circuit of FIG. 5 according to Thevenin's theorem.

FIG. 7 is a circuit diagram showing an equivalent circuit obtained by further rewriting the circuit of FIG.

[Explanation of symbols]

1 ... Metal container for gas insulated switchgear, 2 ... Insulation spacer,
3 ... Main circuit conductor, 5 ... Voltage dividing electrode container, 7 ... Connection conduit, 8
... Insulating spacer, 9 ... Tank, 10 ... Instrument transformer main body, 12 ... Primary coil, 13 ... Secondary coil, 15 ... Connection conductor, 16 ... High voltage electrode, 17 ... Voltage dividing electrode.

Claims (2)

[Scope of utility model registration request] 1. A metal voltage dividing electrode container connected to a metal container of a gas insulated switchgear via an insulating spacer; and a voltage dividing electrode container connected to a main circuit conductor of the gas insulated switchgear in the voltage divider electrode container. A high voltage electrode arranged, a cup-shaped voltage dividing electrode provided so as to concentrically surround the high voltage electrode in the voltage dividing electrode container, a gas dividing means and a connecting conduit in the voltage dividing electrode container. A gas-insulated instrument transformer, in which a transformer main body for instruments is housed in a tank connected through the tank, and the same insulating gas as the insulating gas used for the gas-insulated switchgear is enclosed in the tank, A voltage for a gas-insulated switchgear, characterized in that the voltage dividing electrode and the primary terminal of the meter transformer main body are connected by a connecting conductor penetrating through the partitioning means and concentrically extending in the connecting conduit. Transformer. 2. The voltage for a gas insulated switchgear according to claim 1, wherein the connection conduit has an insulation strength capable of withstanding a divided voltage generated between the voltage dividing electrode and the ground. Transformer.