Vacuum interrupter, transformer arrangement and method for monitoring a vacuum interrupter

Abstract

This disclosure relates to a vacuum interrupter (1) for an on-load tap changer (10), the vacuum interrupter (1) comprising a cylindrical housing (12) arranged on an axis (z), the housing comprising a wall (14) enclosing an hermetically sealed internal volume (16), the wall (14) further comprising a ceramic bottom portion (15) extending perpendicular to the axis (z), the wall (14) of the housing (12) comprising a first optical interface (18) between the internal volume (16) and an external environment (20) outside the housing (12), the first optical interface (18) being configured to interact with at least one The optical wavelength is transparent, and the internal volume (16) includes a light guide (22) leading to the environment of the internal volume (16), a switch (34) arranged coaxially with the housing (12) on the axis (z) and located in the internal volume (16) of the housing (12), and the vacuum interrupter (1) also includes a shielding element (40) arranged coaxially with the switch (34), wherein the light guide (22) is recessed relative to the inner surface (32) of the ceramic bottom portion (15) in the wall (14) of the housing (12), and the shielding element (40) is arranged between the switch (34) and the light guide (22).

Description

Technical Field

[0001] This invention relates to a vacuum interrupter, a transformer arrangement including the vacuum interrupter, and a method for monitoring the vacuum interrupter. Specifically, this invention relates to a vacuum interrupter including an optical interface, and a transformer arrangement including a monitoring unit for optically monitoring the vacuum interrupter. Background Technology

[0002] A vacuum interrupter is a switching device that uses electrical contacts in a vacuum. It is used in medium-voltage circuit breakers, generator circuit breakers, and high-voltage circuit breakers. The separation of the electrical contacts generates a metal vapor arc, which is quickly extinguished. Over its lifespan, the occurrence of arcing between the electrical contacts will eventually reduce the making and breaking performance of the vacuum interrupter.

[0003] Furthermore, when selecting the number of turns of the transformer, the vacuum interrupter installed in the on-load tap changer can function as a switch or circuit breaker. The tap changer is typically installed together with the transformer in the transformer tank. The tap changer is at least partially enclosed by the transformer tank. The transformer tank may be filled with an insulating liquid, such as mineral oil. During the service life of the vacuum interrupter, the vacuum state may be disrupted. The bellows section of the vacuum interrupter may be damaged, causing the internal volume of the vacuum interrupter to be filled with oil from the transformer tank it is located in. The breaking and making performance of the vacuum interrupter will thus be severely degraded, potentially shortening the life of the on-load tap changer. In addition, because the distance between different potentials between the electrical contacts in the vacuum interrupter is usually short, the probability of arcing will increase. The arc temperature is very high and will burn part of the oil, causing carbonization and reducing its electrical insulation properties.

[0004] The harsh environment of on-load tap changers, including oil immersion and large potential differences, makes monitoring of the on-load tap changer and its components difficult. Introducing any component into the transformer tank requires consideration of the electromagnetic characteristics of both the introduced component and existing components. Furthermore, the internal space of the transformer tank is limited. Summary of the Invention

[0005] Therefore, one object of this disclosure is to provide an improved vacuum interrupter, an improved transformer arrangement including the vacuum interrupter, and an improved method for monitoring the vacuum interrupter in the transformer arrangement. Specifically, one object is to be able to continuously monitor the status of the vacuum interrupter and / or detect leakage in the vacuum interrupter.

[0006] According to a first aspect of this disclosure, this objective is achieved at least in part by the vacuum interrupter as described in claim 1.

[0007] Therefore, a vacuum interrupter for an on-load tap changer is provided. The vacuum interrupter includes a cylindrical housing arranged on an axis. The housing includes a wall enclosing a hermetically sealed internal volume. The wall further includes a ceramic bottom portion extending perpendicular to the axis. The housing wall includes a first optical interface between the internal volume and the external environment outside the housing. The first optical interface is configured to be transparent to at least one optical wavelength. The internal volume includes a light guide leading to the environment of the internal volume, having a first guide end and a second guide end. At least the first guide end is optically connected to the at least one optical interface. The switch is coaxially arranged with the housing on an axis and within the internal volume of the housing. The switch includes a first electrical contact and a second electrical contact movable relative to each other between an off position and an on position. The vacuum interrupter also includes a shielding element arranged coaxially with the switch. The light guide is recessed relative to the inner surface of the ceramic bottom portion of the housing wall, and the shielding element is arranged between the switch and the light guide.

[0008] The shell of a vacuum interrupter can be cylindrical. The shell of the vacuum interrupter is hermetically sealed to contain the vacuum. "Vacuum" here should be understood as a low-pressure volume, the pressure of which can be maintained at approximately 10... -5 Pa. The housing may include a bellows section, which may be made of stainless steel and may extend along the axial direction. If the vacuum of the housing is broken, the bellows section will typically rupture.

[0009] The external environment of the vacuum interrupter housing depends on the installation location of the vacuum interrupter. In this disclosure, the external environment should be understood as the environment of the on-load tap changer in which the vacuum interrupter is installed. In operation, the part of the on-load tap changer where the vacuum interrupter is installed is inside the transformer tank. In other words, the external environment of the vacuum interrupter housing can be the transformer oil in the transformer tank. The pressure of the oil environment is usually equal to atmospheric pressure. Therefore, leakage in the vacuum interrupter housing will cause the housing to be rapidly filled with oil.

[0010] The term "wall" in the shell should be understood to include different wall sections that together constitute the shell. One wall section could be the bellows section of the shell. Another wall section could be the ceramic bottom section extending perpendicular to the axis. The wall may have different thicknesses in different parts of the shell.

[0011] The housing may have at least one opening, which may be sealed by a first optical interface. The optical interface may be configured as an optical connector for connecting other optical components. The optical interface may be provided with a fixing device for attaching an optical waveguide (such as an optical fiber) to the optical interface. The optical interface allows optical light of at least one wavelength to enter and / or exit the housing.

[0012] To protect the optical properties of the first and / or second optical interfaces and the ends connected to the optical interfaces or to the light guides including reflective elements, the optical waveguides may be recessed. For example, the light guide may include an optical path disposed in a recess or groove on the inner surface of the wall (such as the bottom portion) of the housing. This recessed arrangement prevents the deposition of metal vapor generated by the electric arc in the internal volume of the vacuum interrupter on the optical surface of the light guide.

[0013] The shielding element can be used as a surface on which metal vapor generated by the electric arc is deposited. In other words, the shielding element provides protection for the optical components of the light guide and optical interface from the metal vapor generated by the electric arc between the first and second contacts.

[0014] The optical guide should be understood as an optical path having a first guide end and a second guide end. The first guide end, which is optically connected to the first optical interface, is therefore also optically communicating with the second guide end.

[0015] The light guide leads to the internal volume environment. If the internal volume is filled with oil, the light guide will also be filled with oil.

[0016] Optionally, the second guide end includes a light-reflecting element.

[0017] The second guiding end may include a light reflecting element such that light entering the light guide from the first end (i.e. from the first optical interface) is reflected by the reflecting element and returned to the first optical interface.

[0018] Optionally, the vacuum interrupter also includes a second optical interface between the internal volume and the external environment outside the housing, with the second guide end optically connected to the second optical interface.

[0019] When the second optical interface is connected to the second guide end, light entering the light guide can exit the housing via the first optical interface and / or the second optical interface. Light entering the housing via one optical interface can exit the housing via the other optical interface.

[0020] According to a second aspect of this disclosure, this objective is achieved at least in part by the transformer arrangement described in claim 7.

[0021] Therefore, a transformer arrangement is provided, including a transformer tank, a transformer, a monitoring unit, and an on-load tap changer. The transformer tank includes an insulating medium, the transformer is enclosed within the transformer tank, the monitoring unit is located outside the transformer tank, and the on-load tap changer is at least partially enclosed within the transformer tank. The on-load tap changer includes at least one vacuum interrupter according to any embodiment of the first aspect of this disclosure. At least a first and / or second optical interface of the vacuum interrupter is optically connected to the monitoring unit via at least one optical waveguide.

[0022] The transformer arrangement is configured to monitor the state of the vacuum interrupter by studying the characteristics of light leaving and / or entering the vacuum interrupter housing.

[0023] At least one optical waveguide can be an optical fiber and can be made of an insulating material such as glass, which is unaffected by potential differences and does not interfere with the electromagnetic fields inside the transformer tank. Therefore, the optical waveguide is a useful information carrier between any component being monitored inside the transformer tank and the monitoring unit outside the transformer tank. Here, the outside of the transformer tank should be understood as an oil-free environment at atmospheric pressure, where there are no large potential changes. This environment can be the field monitoring device located near the transformer, or it can be located far from the transformer assembly.

[0024] At least one optical waveguide can be optically connected between the first and / or second optical interfaces and the monitoring unit via a bushing disposed in the wall of the transformer box. Alternatively, at least one optical waveguide can transition between the interior and exterior of the transformer box via a portion of an on-load tap changer protruding from the interior of the transformer box.

[0025] The occurrence of an electric arc will result in intense flashes, which can be detected by a monitoring unit. The monitoring unit may include communication and / or processing devices, and may further include computer storage capacity. Therefore, the occurrence of electric arcs can be detected, recorded, and counted. The condition of the vacuum interrupter can be monitored by studying the number of arcs occurring during its operation. A large number of arcs may indicate a decline in the performance of the vacuum interrupter and may suggest that it should be maintained or replaced before a failure occurs.

[0026] If the housing is filled with oil, the switching performance of the vacuum interrupter will be severely degraded. Filling can be detected by studying the characteristics of light emitted from the monitoring unit and entering the internal volume of the housing, and comparing these characteristics with, for example, the corresponding characteristics of light returning from the internal volume of the housing. This characteristic is selected from the properties of the medium in which the light propagates. This characteristic could be the transmittance of the emitted light. Changes in the transmittance of the emitted light will therefore be detectable and may indicate that the propagation medium in the light guide within the internal volume has changed from near-vacuum to oil.

[0027] Optionally, the monitoring unit includes at least one optical light emitter and at least one optical light detector.

[0028] At least one optical transmitter may be configured to transmit an optical monitoring signal into the internal volume of the vacuum interrupter via at least one optical waveguide and via a first optical interface and / or a second optical interface. The optical monitoring signal may include at least one wavelength, preferably a single wavelength. The optical monitoring signal may be emitted continuously or intermittently at suitable predetermined intervals between emission. The optical transmitter may be selected from any suitable optical transmitter known in the art, such as a laser, a light-emitting diode, etc.

[0029] At least one optical photodetector may be configured to detect the optical wavelength and / or optical properties of light emitted from the internal volume of the vacuum interrupter via a first and / or second optical interface and at least one optical waveguide.

[0030] According to a third aspect of this disclosure, this objective is achieved at least in part by the method of claim 9.

[0031] Therefore, a method is provided for monitoring the health status of a vacuum interrupter according to any embodiment of the first aspect of the present disclosure in a transformer arrangement according to any embodiment of the second aspect of the present disclosure. The method includes:

[0032] - The monitoring unit detects the optical status signal of the internal volume of the vacuum interrupter via a first optical interface or a second optical interface, and via at least one optical waveguide.

[0033] - The characteristics of the optical status signal are determined by the monitoring unit to determine the health status of the vacuum interrupter.

[0034] The optical status signal here should be understood as an optical signal that leaves the internal volume of the vacuum interrupter and is detected by the monitoring unit. In this context, "signal" generally refers to any kind of detectable optical emission. This emission may be generated inside the housing or enter the housing from the outside and be detected as emission (reflection) when it leaves the housing. The optical status signal includes optical characteristics used to indicate the status or health of the vacuum interrupter. The monitoring unit determines the characteristics of this optical status signal. Depending on the different characteristics, the optical status signal can provide various indications about the status or health of the vacuum interrupter. These characteristics, determined by the monitoring unit, can be exemplified as intensity, wavelength, transmittance, polarity, etc.

[0035] Optionally, if the characteristic of the optical state signal is that the intensity of the white light wavelength exceeds a predetermined intensity threshold, the monitoring unit records the occurrence of the optical state signal and counts the occurrences of the optical state signal.

[0036] If the characteristic of the optical status signal is the intensity of white light wavelength, it indicates the occurrence of an electric arc. An electric arc refers to the electrical breakdown of the medium between the first and second electrical contacts of the vacuum interrupter's switch. It may be observed as a strong flash of white light wavelength. The occurrence of the arc is then recorded and counted. White light should be understood as a combination of multiple optical wavelengths, rather than, for example, laser light comprising a single wavelength. This method may require the intensity to exceed a predetermined intensity threshold. However, since the probability of other white light phenomena occurring within the internal volume of the vacuum interrupter is extremely low, this intensity threshold can be set relatively low. Therefore, the number of arcs can indicate the status or health of the vacuum interrupter.

[0037] Alternatively, the optical state signal is characterized by the duration of the optical state signal deviating from a predetermined duration, which is recorded and counted by the monitoring unit.

[0038] If the duration of the optical status signal deviates from a predetermined duration, the optical status signal can be identified as an arc. In active monitoring, this involves transmitting an optical monitoring signal into an internal volume, for example, the duration of the pulse of the optical monitoring signal is known. Therefore, by studying the duration of the optical status signal, the optical monitoring signal can be distinguished from other emissions from the internal volume.

[0039] Optionally, the method further includes transmitting an optical monitoring signal from the monitoring unit to the internal volume of the vacuum interrupter via at least one optical waveguide and through a first optical interface.

[0040] The emitted optical monitoring signal can enter the internal volume via the first optical interface, be reflected by the optical reflective element, and exit the internal volume via the first optical interface. Alternatively, the emitted optical monitoring signal can enter the internal volume via the first optical interface, be transmitted via a light guide, and exit the internal volume via a second optical interface. The optical monitoring signal can be emitted continuously or intermittently.

[0041] Optionally, determining the characteristics of the optical state signal includes determining the characteristics of the monitoring signal returned from the internal volume.

[0042] Therefore, the optical status signal can be a returned optical monitoring signal. The known characteristics of the emitted optical monitoring signal can be compared with the characteristics of the returned optical monitoring signal. Changes in these characteristics can indicate changes in the vacuum interrupter. For example, the vacuum interrupter's casing may be filled with oil due to casing damage. The returned optical monitoring signal will therefore propagate through the oil along the optical guide compared to propagation through the near-vacuum environment of an intact vacuum interrupter.

[0043] Optionally, the method further includes generating an alarm for leakage of the vacuum interrupter housing by the monitoring unit if the characteristics of the returned optical monitoring signal exceed a threshold.

[0044] The alarm could be, for example, an indicator on a display, an audible signal, or a notification sent to a handheld communication device. The threshold can be selected to ensure that changes in characteristics indicate a leak in the vacuum interrupter housing.

[0045] Optionally, the characteristic of the returned optical monitoring signal is the transmission coefficient of the emitted optical monitoring signal.

[0046] The change in the transmission coefficient indicates that the emitted monitoring signal has propagated in a medium different from the near-vacuum of the internal volume of the waveguide or vacuum interrupter housing. Attached Figure Description

[0047] Further objects, advantages, and features of this disclosure will become clear from the following description of one or more embodiments taken in conjunction with the accompanying drawings, wherein:

[0048] Figure 1 An example of an on-load tap changer is shown conceptually.

[0049] Figure 2 It shows Figure 1 A detailed view of the on-load tap changer is shown.

[0050] Figure 3 The basic switching function of the vacuum interrupter is shown.

[0051] Figure 4 This is a perspective view of a vacuum interrupter according to the first aspect of this disclosure.

[0052] Figure 5-6 A cross-sectional view of a vacuum interrupter according to a first aspect of this disclosure is shown.

[0053] Figure 7-8 A partial cross-sectional view of a vacuum interrupter chamber according to a first aspect of this disclosure is shown.

[0054] Figure 9 A transformer arrangement according to the second aspect of this disclosure is shown.

[0055] Figure 10 A flowchart of the method according to the third aspect of this disclosure is shown. Detailed Implementation

[0056] The present disclosure will now be described in more detail with reference to the accompanying drawings, which illustrate examples of various embodiments. This disclosure should not be construed as limiting oneself to the described embodiments. The same reference numerals throughout the document denote the same elements.

[0057] The terminology used in this specification is for the purpose of describing specific aspects of this disclosure only and is not intended to limit the invention. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” as used herein should also include the plural forms. Unless otherwise defined, all terms used herein (including technical and scientific terms) should be understood in the manner commonly understood by one of ordinary skill in the art.

[0058] This disclosure provides a vacuum interrupter 1 for an on-load tap changer (hereinafter referred to as OLTC) 10, a transformer arrangement 2 including the vacuum interrupter 1, and a method 3 for monitoring the state of the vacuum interrupter 1 of the on-load tap changer 10. Figure 1 It shows having Figure 2 An example of a vacuum-type OLTC 10 with a reversing switch 58 is shown in an enlarged view. In this example, the OLTC 10 has a housing 60 with an insulating medium 44, a reversing switch 58, and a tap selector 62. The enlarged view of the reversing switch 58 shows a white square in the center. The white square represents certain parts of the reversing switch 58, which are not shown for the purposes of this disclosure. Vacuum interrupters 1 are shown on either side of the white square. In the example shown, there are three vacuum interrupters 1—each vacuum interrupter corresponding to one phase. The vacuum interrupters 1 are turned off and on via a yoke 64. An example of how all three vacuum interrupters 1 are turned off and on is shown. Other methods may also be used.

[0059] exist Figure 3 The diagram conceptually illustrates an example of a vacuum interrupter 1, which includes a switch 34 with the left side in the ON position and the right side in the OFF position. A first contact 36 and a second contact 38 are adjacent in the ON position and separated in the OFF position.

[0060] Figures 4 to 8 A view of a vacuum interrupter 1 according to a first aspect of this disclosure is shown. The vacuum interrupter 1 includes a housing 12 arranged on axis z, the housing having a wall 14. The housing 12 may include a bellows portion 66, which may be made of stainless steel, and when the switch 34 is moved... Figure 2 When the yoke 64 shown is switched off and on, the bellows portion 66 can extend and retract along the axis z, respectively. The vacuum interrupter 1 may also include a first fixed point 68 and a second fixed point 70 for electrically and mechanically connecting the vacuum interrupter 1 to other components, such as the OLTC 10. Figure 1 In the example shown, the first fixed point is connected to the movable yoke 64.

[0061] Figure 4 It shows Figure 3A cross-sectional view of the vacuum interrupter 1, which also shows the internal volume 16 enclosed by a hermetically sealed wall 14. This internal volume 16 can accommodate a pressure of approximately 10... -5 The near-vacuum state of Pa. The wall 14 of the housing 12 includes a first optical interface 18 between the internal volume 16 and the external environment 20 outside the housing 12. The first optical interface 18 is configured to be transparent to at least one optical wavelength.

[0062] The nature of the environment 20 outside the housing 12 of the vacuum interrupter 1 depends on the installation location of the vacuum interrupter 1. In this disclosure, the environment 20 outside the housing 12 should be understood as the environment of the OLTC 10 in which the vacuum interrupter 1 is installed. In operation, the portion of the OLTC in which the vacuum interrupter 1 is installed is located inside the transformer box 42 (see [link to relevant documentation]). Figure 9 (This will be described in more detail below). In other words, the environment 20 outside the vacuum interrupter housing can be an insulating liquid in the transformer tank 42, such as transformer oil 44 in the transformer tank. The pressure of this environment 20 is on the order of atmospheric pressure. Therefore, leakage of the vacuum interrupter housing 12 will quickly cause the housing 12 to be filled with transformer oil 44.

[0063] The “wall” 14 of the housing 12 should be understood to include different wall portions that together constitute the housing 12. One wall portion may be a bellows portion of the housing. Another wall portion may be a ceramic bottom portion 15 extending perpendicular to the axis z. The wall 14 may have different thicknesses in different parts of the housing.

[0064] The housing 12 may have at least one opening, which may be sealed by a first optical interface 18. The optical interface 18 may be configured as an optical connector for connection to other optical components. The optical interface may be provided with a securing device (explained further below) for attaching an optical waveguide 52 (such as an optical fiber) to the optical interface 18. The optical interface 18 allows optical light of at least one wavelength to enter and / or exit the housing 12.

[0065] like Figures 5 to 8 As shown in the cross-sectional view, the internal volume 16 also includes a light guide 22 that opens to the environment of the internal volume 16, such that if the internal volume 16 is filled with oil 44, the light guide 22 will also be filled with oil 44. The light guide 22 has a first guiding end 24 and a second guiding end 26. The first guiding end 24 is optically connected to a first optical interface 18. The light guide 22 can be provided as an optical path including the first guiding end 24 and the second guiding end 26. Since the first guiding end 24 is optically connected to the first optical interface 18, it also optically communicates with the second guiding end 26.

[0066] The second guide end 26 may include an optical reflective element 30. Figure 8This ensures that light entering the light guide 22 from the first end 24 (i.e., from the first optical interface 18) is reflected by the reflective element 30 and returned to the first optical interface 18, such as... Figure 8 As indicated by the arrow, the light can exit the housing 12 via the first optical interface 18.

[0067] Alternatively, such as Figure 7 As shown, the vacuum interrupter 1 may include a second optical interface 28 located between the internal volume 16 and the external environment 20 outside the housing 12. In this configuration, the second guide end 26 is optically connected to the second optical interface 28. Therefore, when the second optical interface 28 is connected to the second guide end 26, light entering the light guide 22 can exit the housing 12 via the first optical interface 18 and / or the second optical interface 28. Light entering the housing 12 and the light guide 22 via one optical interface 18, 28 can exit the housing 12 via the other optical interface 18, 28.

[0068] Figures 5 to 6 The light guide 22 is shown to be recessed relative to the inner surface 32 of the wall 14 (e.g., bottom portion 15) of the housing 12. This arrangement provides protection for the first and / or second optical interfaces 18, 28 and the first and second light guide ends 24, 26 connected to the first and second optical interfaces 18, 28 or including reflective elements 30. As an example, the light guide 22 may include a light path disposed in a recess or groove in the inner surface 32 of the wall 14 (e.g., bottom portion 15) of the housing 12. This recessed arrangement prevents the deposition of metal vapor on the optical surfaces of optical elements within the internal volume 16, which may be generated by an electric arc in the internal volume 16 of the vacuum interrupter 1.

[0069] like Figures 5 to 6 As illustrated, the vacuum interrupter 1 may also include Figure 3 The switch 34, briefly described herein, is arranged coaxially with the housing 12 on axis z and is located within the internal volume 16 of the housing 12. The switch 34 includes a first electrical contact 36 and a second electrical contact 38 that are movable relative to each other along axis z between an off position and an on position. Figure 5 The ON position of switch 34 is shown. Figure 6 The off position of switch 34 is shown. The vacuum interrupter 1 also includes a shielding element 40 arranged coaxially with switch 34. Shielding element 40 is positioned between switch 34 and light guide 22. Therefore, shielding element 40 serves as a protective surface on which metal vapor generated by the electric arc between the first electrical contact 36 and the second electrical contact 38 is deposited. In other words, shielding element 40 provides further protection for the light guide 22 and the optical components of optical interfaces 18, 28 from the effects of metal vapor generated by such electric arcs.

[0070] exist Figures 5 to 6 In the example shown, the shielding element is tubular and forms a cup-shaped volume together with the inner surface 32 of the wall 14, with the light guide recessed relative to this inner surface 32. The light guide 22 may be formed as a recess or groove on the inner side of the bottom portion 15 of the housing 12. Because the interface between the shielding element 40 and the inner surface 32 is closed, the cup-shaped volume closes downward relative to the axis z (when considered as a vertical axis). The light guide 22 is located radially outside the shielding element 40 relative to the switch 34, which is located radially inside the shielding element 40. The shielding element 40 is open upward so that the switch 34 can be turned on and off along the axis z. Therefore, the light guide 22 is protected from metal vapor, as any metal vapor is forced to diffuse upward first (radially inside the shielding element 40) and then downward (radially outside the shielding element 40) before reaching the light guide 22.

[0071] Figure 9 The transformer arrangement 2 according to the second aspect of this disclosure is schematically shown. Figure 9 The various parts of transformer arrangement 2 are shown symbolically and are not drawn to scale. Transformer arrangement 2 includes a transformer tank 42 containing an insulating medium 44 (such as mineral oil). A transformer 46 is enclosed within the transformer tank 42. A monitoring unit 48 is located outside the transformer tank 42, and an on-load tap changer 10 is at least partially enclosed within the transformer tank 42. The on-load tap changer 10 includes at least one vacuum interrupter 1 according to any embodiment of the first aspect of this disclosure. At least a first and / or second optical interface 18, 28 of the vacuum interrupter 1 is optically connected to the monitoring unit 48 via at least one optical waveguide 52.

[0072] According to the second aspect of this disclosure, the transformer arrangement 2 is configured to monitor the state of the vacuum interrupter 1 by studying the characteristics of light leaving and / or entering the housing 12 of the vacuum interrupter 1.

[0073] At least one optical waveguide 52 may be an optical fiber and may be made of an insulating material such as glass, which is unaffected by potential differences and will not interfere with the electromagnetic field inside the transformer box 42. Therefore, the optical waveguide 52 is a useful information carrier between any monitored component inside the transformer box 42 (e.g., the vacuum interrupter 1) and the monitoring unit 48 outside the transformer box 42.

[0074] At least one optical waveguide 52 may be optically connected to the monitoring unit 48 via a bushing 72 in the wall of the transformer box 42. Alternatively, at least one optical waveguide 52 may be transitioned between the interior and exterior of the transformer box 42 via a portion of the on-load tap changer 10 protruding from the interior of the transformer box 42.

[0075] The occurrence of an electric arc will result in intense flashes, which can be detected by monitoring unit 48. Monitoring unit 48 may include communication device 74 and / or processing device 76, and may further include computer storage capacity (not shown). Therefore, the occurrence of electric arcs can be detected, recorded, and counted. By studying the number of electric arcs occurring during the operation of vacuum interrupter 1, the condition of vacuum interrupter 1 can be monitored. A large number of electric arcs may indicate a decline in the performance of vacuum interrupter 1 and may suggest that it should be maintained or replaced before a failure occurs.

[0076] If the housing 12 is filled with oil, the switching performance of the vacuum interrupter 1 will be severely degraded. For example, filling can be detected by comparing the characteristics of light emitted from the monitoring unit 48 to the internal volume 16 of the housing 12 with the corresponding characteristics of light returning from the internal volume 16 of the housing 12. This characteristic is selected from those depending on the characteristics of the medium in which the light propagates and those affected by the medium in which the light propagates. This characteristic could be the transmittance of the emitted light. Changes in the transmittance of the emitted light are detectable and may indicate that the propagation medium in the light guide 22 of the internal volume 16 has changed from near vacuum to oil.

[0077] The monitoring unit 48 may include at least one optical light emitter 54 and at least one optical light detector 56.

[0078] At least one optical emitter 54 may be configured to transmit an optical monitoring signal to the internal volume 16 of the vacuum interrupter 1 via at least one optical waveguide 52 and via a first optical interface 18 and / or a second optical interface 28. The optical monitoring signal may include at least one wavelength. The optical monitoring signal may be emitted continuously or intermittently at suitable predetermined intervals between emissions. The optical emitter 54 may be selected from any suitable optical emitter known in the art, such as a laser, a light-emitting diode, etc.

[0079] At least one optical photodetector 56 may be configured to detect the optical wavelength and / or optical properties of light exiting from the internal volume 16 of the vacuum interrupter 1 via the first and / or second optical interfaces 18, 28 and at least one optical waveguide 52.

[0080] Figure 10 A flowchart of method 3 according to a third aspect of this disclosure is shown. Dashed boxes indicate optional actions in method 3. Therefore, method 3 is used to monitor the health status of the vacuum interrupter 1 in any embodiment of the first aspect of this disclosure in a transformer arrangement 2 according to any embodiment of the second aspect of this disclosure. Method 3 includes:

[0081] - The monitoring unit 48 detects the optical status signal S1 from the internal volume 16 of the vacuum interrupter 1 via the first optical interface 18 or via the second optical interface 28, and via at least one optical waveguide 52; and

[0082] - The characteristics of the S2 optical status signal are determined by the monitoring unit 48 to determine the health status of the vacuum interrupter 1.

[0083] Therefore, the optical status signal is an optical signal that exits from the internal volume 16 of the vacuum interrupter 1 and is detected by the monitoring unit 48. This optical status signal includes optical characteristics used to indicate the status or health of the vacuum interrupter 1. The monitoring unit 48 determines the characteristics of the optical status signal. Depending on the different characteristics, the optical status signal can provide different indications about the status or health of the vacuum interrupter 1. The characteristics determined by the monitoring unit 48 may include, for example, light intensity, wavelength, transmittance, polarity, etc.

[0084] If the characteristic of the optical state signal is the intensity of the white light wavelength, then method 3 may further include recording and counting the occurrence of the S3 optical state signal by the monitoring unit 48. The white light intensity can indicate the occurrence of an electric arc. Since the number of electric arcs can indicate the state or health of the vacuum interrupter, the occurrence of electric arcs should be recorded and counted. To determine an electric arc, the method may require the intensity to exceed a preset light intensity threshold. However, since the possibility of other white light phenomena occurring in the internal volume 16 of the vacuum interrupter 1 is extremely low, the light intensity threshold can be set relatively low.

[0085] Method 3 may further include transmitting an optical monitoring signal S4 from the monitoring unit 48 to the internal volume 16 of the vacuum interrupter 1 via at least one optical waveguide 52 and via a first optical interface 18. The transmitted optical monitoring signal may enter the internal volume 16 via the first optical interface 18, be reflected by the optical reflecting element 30, and exit the internal volume 16 via the first optical interface 18 (see...). Figure 8 Alternatively, the emitted optical monitoring signal can also enter the internal volume 16 via the first optical interface 18, be transmitted via the light guide 22, and exit the internal volume 16 via the second optical interface 28 (see...). Figure 7 Optical monitoring signals can be transmitted continuously or intermittently.

[0086] The action of determining the characteristics of the S2 optical status signal by the monitoring unit 48 may also include: determining the characteristics of the returned monitoring signal from the internal volume 16. The optical status signal can thus be the returned optical monitoring signal. The known characteristics of the emitted optical monitoring signal can be compared with the corresponding characteristics of the returned optical monitoring signal. Changes in characteristics can indicate changes in the vacuum interrupter 1. For example, the housing 12 of the vacuum interrupter 1 may be filled with oil due to damage. Compared to propagation through the near-vacuum environment of the intact vacuum interrupter 1, the returned optical monitoring signal will therefore propagate along the light guide 22 in the oil.

[0087] Method 3 may further include: if the characteristics of the returned optical monitoring signal match a predetermined value or exceed a threshold, the monitoring unit 48 generates an alarm indicating a leak in the housing 12 of the vacuum interrupter.

[0088] The alarm can be, for example, an indication on a display, the generation of an audible signal, or a notification sent to a handheld communication device. This threshold can be selected to ensure that changes in characteristics indicate a leak in the housing of the vacuum interrupter.

[0089] The characteristic of the returned optical monitoring signal can be the transmission coefficient of the emitted optical monitoring signal. A varying transmission coefficient indicates that the emitted monitoring signal has propagated in a medium different from the near-vacuum of the internal volume of the waveguide or vacuum interrupter housing. The transmission coefficient of the emitted monitoring signal can be known or calculable, i.e., predetermined. If the determined characteristic is the transmission coefficient, and it matches a predetermined value for the oil, then it can be determined that the internal volume 16 has been filled with oil.

[0090] As stated above, and as Figure 10 As shown, method 3 may include monitoring the occurrence of an electric arc in the internal volume 16 and / or monitoring the vacuum of the vacuum interrupter 1 by detecting leaks in the housing 12. The former is a passive monitoring method that monitors the light emission generated by the electric arc by determining the characteristics of the light emitted from the internal volume 16. The latter is a method that includes actively emitting a monitoring signal and determining the characteristics of the returned monitoring signal.

[0091] This invention is not limited to the disclosed embodiments, but can be modified and altered within the scope of the following claims.

Claims

1. A vacuum interrupter (1) for an on-load tap changer (10), the vacuum interrupter (1) comprising: - A cylindrical housing (12) arranged on an axis (z), the housing comprising a wall (14) enclosing an airtight internal volume (16), the wall (14) further comprising a ceramic bottom portion (15) extending perpendicular to the axis (z). - The wall (14) of the housing (12) includes a first optical interface (18) between the internal volume (16) and the external environment (20) outside the housing (12), the first optical interface (18) being configured to be transparent to at least one optical wavelength. - The internal volume (16) includes a light guide (22) that opens to the environment of the internal volume (16) and has a first guide end (24) and a second guide end (26), at least the first guide end (24) being optically connected to the at least one optical interface, wherein the light guide (22) is configured to guide light originating from an electric arc to the at least one optical interface. - A switch (34) is arranged coaxially with the housing (12) on the axis (z) and located within the internal volume (16) of the housing (12), the switch (34) including a first electrical contact (36) and a second electrical contact (38) movable relative to each other between an off position and an on position, the vacuum interrupter (1) further including a shielding element (40) arranged coaxially with the switch (34). The light guide (22) is formed as a recess or groove on the inner side of the bottom portion (15) of the housing (12), and the shielding element (40) is arranged between the switch (34) and the light guide (22) and at least partially overlaps the light guide (22) in the direction of the axis (z).

2. The vacuum interrupter (1) according to claim 1, wherein the second guide end (26) includes an optical reflective element (30).

3. The vacuum interrupter (1) according to claim 2 further includes a second optical interface (28) between the internal volume (16) and the external environment (20) outside the housing (12), wherein the second guide end (26) is optically connected to the second optical interface (28).

4. A transformer arrangement structure (2) includes a transformer box (42), a transformer (46) enclosed in the transformer box (42), a monitoring unit (48) located outside the transformer box (42), and an on-load tap changer (10) at least partially enclosed in the transformer box (42), the on-load tap changer (10) including at least one vacuum interrupter (1) according to any of the preceding claims, and wherein at least a first optical interface (18) of the vacuum interrupter (1) is optically connected to the monitoring unit (48) via at least one optical waveguide (52).

5. The transformer arrangement structure (2) according to claim 4, wherein the monitoring unit (48) includes at least one optical light emitter (54) and at least one optical light detector (56).

6. A method for monitoring the health status of a vacuum interrupter (1) according to any one of claims 1 to 3 in a transformer arrangement (2) according to any one of claims 4 to 5, the method comprising: - The monitoring unit (48) detects (S1) the optical status signal from the internal volume (16) of the vacuum interrupter (1) via the first optical interface (18) or via the second optical interface (28), and via the at least one optical waveguide (52), and - The characteristics of the optical state signal are determined by the monitoring unit (48) to determine (S2) the health status of the vacuum interrupter (1).

7. The method according to claim 6, wherein the characteristic of the optical state signal is that the intensity of the white light wavelength exceeds a predetermined intensity threshold, then the monitoring unit (48) records and counts (S3) the occurrence of the optical state signal.

8. The method according to any one of claims 6 to 7, further comprising transmitting (S4) an optical monitoring signal by the monitoring unit (48) via the at least one optical waveguide (52) and via the first optical interface (18) into the internal volume (16) of the vacuum interrupter (1).

9. The method of claim 8, wherein determining (S2) the characteristics of the optical state signal includes determining the characteristics of the monitoring signal returned from the internal volume (16).

10. The method of claim 8, further comprising: If the characteristics of the returned optical monitoring signal match a predetermined value or exceed a threshold, an alarm is generated by the monitoring unit (48).

11. The method of claim 10, wherein the characteristic of the returned optical monitoring signal is the transmission coefficient of the emitted optical monitoring signal.

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