Apparatus and method for detecting a vacuum condition in a vacuum electrical device

Abstract

A bracket 106 with first and second arms mounted to a vacuum electrical device 104 (e.g. vacuum interrupter) wherein an acoustic transmitter 108 is coupled to the first arm 106a and an acoustic receiver 110 is coupled to the second arm 106b wherein the arms are disposed on opposite sides of the vacuum electrical device to monitor a vacuum. The generated sound 112a waves maybe ultrasound waves. An alert maybe issued in response to a detected low vacuum condition. The apparatus 102 maybe used in a insulated switchgear.

Description

10 Vacuum electrical devices, including vacuum switching devices such as vacuum interrupters, are typically sealed for life and maintenance free components. Proper operation of these devices requires that an internal pressure not exceed a critica! threshold, or in other words that a high enough vacuum is maintained within the device. However, the seals on these evacuated devices can fail overtime, allowing air / 5 or other gases to leak into the device and thereby causing a lower vacuum condition. This can cause issues during norma! operation of the devices, for example when the contacts of vacuum interrupters are opened during a fault condition. The presence of a vacuum can be determined by applying a high AC-voltage over the 20 open contacts of the switching device, but this approach requires that the vacuum switching device is isolated from the electrical network. Other non-destructive testing approaches include portable dielectric or magnetron tests, or ultrasonic testing, in which a transducer is mounted on the electrical device and the attenuation of the ultrasound wave is determined with a receiver probe on the other 25 side of the electrical device. However, these tests also require that the vacuum electrical device is isolated from the electrical network. WO2007 / 040990A1 discloses detection of high-pressure conditions in a vacuum interrupter through the use of sonic transducers, where the amplitude and timing of 30 the reflected sonic response signals are used to determine the gas pressure within the interrupter. The sonic transducers can be used while the interrupter is in operation, and at operating potential, and can be attached to an outer insulation layer of the interrupter. A specific sonic wave guide is required to adapt the generally flat, planar emitting and receiving surfaces of the transducers to the curved, cylindrical outer 35 surface of the interrupter. The sonic wave guide also amplifies the intensity of the sound delivered to the interrupter and provides the necessary electrical isolation between the high voltage surface of the interrupter and the low voltage transducers. It is desirable to provide an apparatus which can be used when the vacuum electrical device is operational, and which can be easily retrofit to existing vacuum electrical devices. Moreover, it is desirable to provide an apparatus for detecting a low vacuum 5 condition of a vacuum electrical device which is less expensive and complex than the arrangement of WO2007 / 040990A1. Summary The matter for protection is set out in the appended independent claims, with optional jo features recited in the dependent claims appended thereto. Disclosed herein is an apparatus for detecting a low vacuum condition within a vacuum electrical device. The apparatus is called herein a vacuum detection and / or monitoring apparatus. The apparatus comprises a bracket configured to be mounted 15 to the vacuum electrical device, the bracket comprising first and second arms disposed on opposite sides of the vacuum electrical device. The apparatus further comprises a transmitter coupled to the first arm of the bracket and configured to transmit a generated sound wave into the vacuum electrical device. The apparatus further comprises a receiver coupled to the second arm of the bracket and configured to 20 receive the transmitted sound wave. The vacuum can be detected or monitored using through transmission of the generated sound wave (i.e. by detecting whether the incident or source wave generated and emitted by the transmitter is transmitted through the device and 25 received at the receiver). By providing a bracket at least partially around the device, such that the transmitter and receiver are arranged on opposite sides of the vacuum electrical device (e.g. the device is at least partly disposed between the first and second arms of the bracket), through-transmission of the generated sound wave can be used without the transmitter and receiver having to be mounted on the device 30 itself. This simplifies the arrangement and avoids the need for specialised, complex components to adapt the generally flat surfaces of the transmitter and receiver to the curved surface of the device. Moreover, the use of a bracket as described herein facilitates easy retrofitting of the apparatus; the apparatus can be installed with little or no change in device design. It is a completely contactless method, and adoptable 35 in all insulating mediums such as air, gas (e.g., SF6 insulation) and oil. In this way, a reliable, convenient, small sized and low-priced vacuum monitoring apparatus can be provided for use with vacuum electrical devices. A tow vacuum condition can be detected based on the transmitted sound wave (e.g. the through wave received at the receiver). In particular, the presence or absence of a transmitted sound wave at the receiver can indicate whether there is a low vacuum condition within the vacuum electrical device. When a medium or high vacuum is 5 present within the vacuum electrical device, the generated sound wave will not be transmitted through the device, and no sound wave will be received at the receiver. Detection of the transmitted sound wave at the receiver (e.g. detection of a through wave) can therefore indicate a low vacuum condition within the device, i.e., an internal pressure above or exceeding a predefined threshold. Moreover, by using this jo binary through-transmission approach, the reflectance at the various surfaces need not be considered; computational resources required for processing the output from the transmitter and the receiver may therefore be reduced as compared to approaches which require analysis of sonic spectra, for example. 15 In some implementations, the bracket is configured such that there is a physical separation between the apparatus and the vacuum electrical device in the region of the first and second arms. In other words, there is a physical separation between the transmitter and first arm of the bracket and the vacuum electrical device, and a physical separation between the receiver and second arm of the bracket and the 20 vacuum electrical device. In this way, neither the transmitter, receiver or the first and second arms of the bracket physically contact the device 104. This physical separation (or gap) can help to electrically isolate the transmitter and receiver from the high voltage surfaces of the vacuum electrical device, without the need for any particular dielectric material to be used. In some examples this physical gap may be 25 filled with air (e.g., there can be an air gap between the transmitter and receiver and the device), but any insulating medium can be used depending on the application or environment for which the apparatus is used. In some examples, the bracket is formed from an insulating material. This can help to 30 further electrically isolate the transmitter and receiver from the high voltage surfaces of the vacuum electrical device. Optionally, the bracket is arranged between the vacuum electrical device and the transmitter and between the vacuum electrical device and the receiver (and there is a physical separation between the first and second arms of the bracket and the vacuum electrical device). This arrangement can 35 further improve the electrical isolation of the transmitter and receiver from the device. In some implementations, the apparatus further comprises processing means configured to detect a low vacuum condition based on the transmitted sound wave (or through wave) which is transmitted through the device and received at the receiver. The processing means can be further configured to monitor a vacuum condition of the vacuum electricai device over a period of time, wherein the monitoring is periodic monitoring or continuous monitoring. This arrangement can help to monitor / detect 5 the loss of vacuum of a device over time, allowing for overall health monitoring of the vacuum electrical device. By providing real-time monitoring, which is not limited to maintenance intervals, failures of devices as a result of a loss of vacuum can be reduced or eliminated. Furthermore, this approach can allow for a more reliable assessment of the vacuum condition of devices and can reduce maintenance / down jo time due to faults or failures. In some examples, the low vacuum condition can be detected based at least in part on an amplitude of the transmitted sound wave. In this arrangement, no amplitude (i.e., no sound wave detected) indicates a high vacuum, a low amplitude can indicate a 15 medium vacuum, and a high amplitude can indicate a low vacuum. Suitable amplitude - vacuum relationships and / or correlations can be predetermined for a specific device. Determining the amplitude can comprise comparing the amplitude of the wave received at the receiver to the amplitude of the wave transmitted by the transmitter. The change in amplitude can be comprise to one or more predetermined amplitude -20 vacuum relationships and / or correlations for a specific device to determine the vacuum condition. Optionally, the processing means are configured to cause outputting of an alert in response to the detection of a low vacuum condition. The alert can be one or more of: 25 a graphical alert, an audible alert, a tactile alert, a haptic alert, or a visual alert. Optionally, a low vacuum condition corresponds to a pressure within the vacuum electrical device of at least 1 mbar. More optionally, a low vacuum condition corresponds to a pressure of at least 10 mbar. In some examples, a low vacuum 30 condition corresponds to an internal pressure between 1 and 103 mbar, optionally between 10 and 103 mbar. At internal pressures below 10 mbar, optionally below 1 mbar, the transmitted sound wave can be detected at the receiver. In some implementations, the generated sound wave is an ultrasound wave. 35 Also disclosed herein is a system comprising the apparatus and a vacuum electrical device. Optionally, the vacuum electrical device is a vacuum interrupter. Also described is an insulating switchgear comprising the system, wherein an insulating medium is disposed between the vacuum electrical device and the apparatus. Optionally, the insulating medium is one of: air, a gas (for example SF6 insulation) or an oil. 5 Disclosed herein is also a method for detecting a low vacuum condition within a vacuum electrical device. The method comprises transmitting, with a transmitter, a generated sound wave into the vacuum electrical device, wherein the transmitter is mounted to a first arm of a bracket. The method further comprises receiving, at a jo receiver, the transmitted sound wave, the receiver mounted to a second arm of the bracket, wherein the bracket is mounted to the vacuum electrical device and wherein the first and second arms are disposed on opposite sides of the vacuum electrical device. The method further comprises detecting a low vacuum condition based on the transmitted sound wave as received at the receiver. 15 It will be understood that any of the features described above with reference to the apparatus, system and switchgear may be provided in any suitable combination. Moreover, features of the apparatus, system and switchgear may be combined with any features of the method, or vice-versa, as appropriate, 20 List of Figures The description is with reference to the following figures: Figure 1A shows a side view of an example system comprising a vacuum electrical device and a vacuum detection and / or monitoring apparatus, and Figure IB 25 shows a top view of the example system of Figure 1A; Figure 2A shows an example signal output from the receiver in the case of a low vacuum (vacuum loss) within the device, and Figure 2B shows an example signal output from the receiver in the case of a high vacuum (no vacuum loss); and Figure 3 is a flowchart illustrating an example method for detecting a low 30 vacuum condition within a vacuum electrical device, Detailed Description With reference to Figures 1A and IB, an apparatus 102 for detecting a low vacuum 35 condition with a sealed vacuum electrical device 104 is described. The apparatus can detect a low vacuum condition by detecting the through transmission of sound waves, as discussed below in more detail with reference to Figures 2A and 2B. The apparatus 102 comprises a bracket 106. The bracket 106 is configured to be mounted to the vacuum electrical device 104. The bracket comprises first 106a and second 106b arms, which are arranged such that they are on opposite sides of the vacuum electrical device 104. In other words, the device 104 is disposed at least 5 partially between the first and second arms 106a, 106b when the bracket 106 is mounted on the device 104. In the arrangement of Figure IB the first and second arms are shown substantially paraliel to one another, but the bracket 106 may be any suitable geometry or configuration such that the first and second arms of the bracket are disposed on opposite sides of the vacuum electrical device 104. JO A transmitter 108 is coupled to the first arm 106a of the bracket 106. The transmitter 108 can be coupled or attached to the bracket in any suitable manner. In some examples, the transmitter is attached to the bracket using a physical coupling and / or an adhesive, for example. Any suitable coupling or attachment can be used, provided 15 that the transmitter is not in contact with the surface of the vacuum electrical device. The transmitter 108 is configured to generate a sound wave 112a and transmit the generated sound wave 112a into the vacuum electrical device 104. The generated sound wave 112a can be any suitable frequency. In some specific examples, the generated sound wave is an ultrasound wave. 20 A receiver 110 is coupled to the second arm 106b of the bracket 106. The receiver 110 can be coupled or attached to the bracket in any suitable manner. In some examples, the receiver is attached to the bracket using a physical coupling and / or an adhesive, for example. Any suitable coupling or attachment can be used, provided 25 that the receiver is not in contact with the surface of the vacuum electrical device. The receiver 110 is configured to receive a transmitted sound wave 112b; the transmitted sound wave 112b is the portion of the generated sound wave 112a emitted by the transmitter 108 that travels through the electrical device 104 and out the opposite side of the device. 30 Based on the transmitted sound wave 112b (also called herein a through wave), properties of the vacuum condition within the vacuum electrical device 104 can be determined. In particular, a low vacuum condition can be detected based on the transmitted sound wave 112b received at the receiver 110, as discussed below with 35 reference to Figures 2A, 2B. The apparatus 102 can further comprise processing means 114 configured to detect a low vacuum condition based on the transmitted sound wave (or through wave) received at the receiver, as shown in Figure 1A. The processing means 114 can be any suitable signal processing means, including e.g,, a comparator, a computer processing unit or a microprocessor. In other implementations, the signal or output from the receiver 110 can be provided to a remote processing means (i.e., a 5 processing means remote from the apparatus 102) and detection of a low vacuum condition may be performed remote from the apparatus. The processing means 114 can be configured to cause an alert to be output in response to the detection of a low vacuum condition. This can allow for timely maintenance or replacement of the device 104, reducing the change of operating faults. JO In some specific implementations, the processing means 114 can be further configured to monitor a vacuum condition of the vacuum electrical device 104 over a period of time. The monitoring can be periodic monitoring (for example, a generated sound wave can be transmitted once a day, once a week, once a month) or continuous 15 monitoring (for example, a generated sound wave is transmitted frequently enough to allow for real time, or near real time, monitoring of the vacuum condition). As shown in Figures 1A, IB, in some implementations there is a physical separation between the apparatus 102 and the device 104 in the region of the first and second 20 arms. In particular, the bracket 106 is configured such that there is a physical separation dl between the first arm 106a and transmitter 108 and the vacuum electrical device 104, and a physical separation d2. between the second arm 106b and receiver 110 and the vacuum electrical device 104 (the separation, or gap, dl and d2 is the distance between the respective dashed lines in Figure 1A). This physical 25 separation (or gap) can be filled with an electrical insulator to help electrically isolate the transmitter 108 and receiver 110 from the vacuum electrical device 104, without the need for any particular dielectric material to be used. Moreover, this physical separation avoids the need for complex shaped transmitters / receivers, since there is no contact with the surface of the device 104. The electrical insulator can be any 30 suitable type, including a gas, an oil and / or a solid insulating material (such as plastic or another electrical insulator). In some examples, the apparatus is physically separated from the device everywhere except where the apparatus is mounted to the device. 35 In the specific example of Figures 1A, IB, the bracket 106 is arranged between the vacuum electrical device 104 and the transmitter 108, and between the vacuum electrical device 104 and the receiver 110. In other words, the bracket is disposed between the transmitter, receiver and the device 104 and there is a physical separation between the first and second arms 106a, 106b of the bracket and the vacuum electrical device (the transmitter and receiver are disposed on an outside of the bracket). The bracket can be formed of an insulating material to help electrically isolate the transmitter 108, receiver 110 from the device 104. In other examples (not 5 shown here) the transmitter and / or the receiver may be disposed on an inside of the bracket, i.e., between the bracket and the device 104. The apparatus 102 and the device 104 together form a system 100. The system can be implemented in any particular manner and using any suitable device 104, In some jo examples, the device 104 is a vacuum interrupter. A new vacuum interrupter can have an internal pressure of about 10~6 mbar at point of sale from the factory (high vacuum). The apparatus described herein can monitor the vacuum condition of such an interrupter and detect when a low vacuum condition is reached (e.g., there is an internal pressure of 1 mbar, optionally of 10 mbar). 15 In some specific examples, the system is implemented as part of an insulating switchgear 200. In such implementations, the physical gaps dl, d2 between the bracket arms 106a, 106b of the apparatus 102 and the device 104 may be filled with air, e.g., if the insulating switch gear is an air insulated switchgear 200 there can be 20 an air gap between the transmitter and receiver and the device. In other examples, the physical gaps dl, d2 between the arms 106a, 106b of the apparatus 102 and the device 104 may be filled with any suitable insulating medium, including, but not. limited to: a gas (such as SF6), a solid insulating material and / or an oil. 25 Detection of a low vacuum condition will now be discussed in more detail with reference to Figures 2A, 2B. Figure 2A shows an example output signal when a sound wave is received by the receiver 110. In particular, it can be seen that the receiver output signal comprises a 30 pulse when a sound wave is detected. When no sound wave is detected, the receiver output signa! is flat, as shown in Figure 2B. The output signal from the receiver 110 can be used to detect a low voltage condition within the vacuum electrical device 104. In particular, when there is a medium or 35 high voltage in the device 104 (an internal pressure of less than 10 mbar, optionally less than 1 mbar), generated sound waves 112a emitted by the transmitter 108 cannot pass through the device 104, Therefore, no through waves are detected at the receiver 110, and the output of the receiver is flat (as shown in Figure 2B). However, as the vacuum within the device 104 begins to leak, the presence of air within the device aiiows sound waves to be transmitted through the device. In other words, as the interna! pressure within the device 104 increases due to a ioss of vacuum, sound waves can begin to be transmitted through the device. 5 With the arrangement described herein, these through waves 112b can be detected at the receiver 110 when the interna! pressure is above a threshold. Interna! pressures above this threshold correspond to a low vacuum condition that can be detected at the receiver. The threshold can be at least 1 mbar, optionally at least 10 mbar. In some jo examples, the presence of a pulse (as in Figure 2A) is sufficient to indicate a low vacuum condition, and an alert can be output based on detection of the low vacuum condition. In this way, a low vacuum condition can be detected based solely on whether or not a through wave is received at the receiver 110, e.g., based on receiving (or detecting) the transmitted sound wave 112b at the receiver 110. By 15 using through waves (or through transmission) in this way, a simple apparatus can be provided which is easy to retrofit and does not require complex components; the apparatus may therefore be cheap and easy to manufacture and install. Moreover, the arrangement is fairly robust and reliable, since it relies only on a detection of a through wave at the receiver and does not require complex analysis or signa! 20 processing (e.g., there is no need to analyse the transmitted sound wave 112b, or through wave, or compare it to the generated sound wave 112a transmitted by the transmitter 108). In some other specific examples, the low vacuum condition can be detected based on 25 an amplitude of the transmitted sound wave 112b (or through wave). In particular, as the internal pressure increases, sound propagation through the device 104 increases; therefore, the resulting transmitted sound wave 112b detected at the receiver 110 can have a higher amplitude (sound intensity increases as the air pressure increases). In this arrangement, no amplitude (i.e., no sound wave detected, as in Figure 2B) 30 indicates a high vacuum, whilst, a low amplitude can indicate a medium vacuum and a high amplitude can indicate a low vacuum. One or more relationships and / or correlations between the amplitude of the initial generated sound wave 112a emitted by the transmitter 108, the amplitude of the transmitted sound wave 112b (or through wave) received at the receiver 110 and the internal pressure (or vacuum condition) 35 can be predetermined for a specific vacuum electrical device 104 and / or a suitable system 100, This arrangement can provide further information about the vacuum condition within the device 104, improving monitoring of the device. With reference to Figure 3, a method 300 for detecting a low vacuum condition within a vacuum electricai device 104 is provided. The method 300 can be performed using an apparatus 102 as described herein. At operation 302, the method comprises transmitting, with the transmitter 108, a generated sound wave 112a into the vacuum 5 electricai device, wherein the transmitter is mounted to the first arm 106a of the bracket 106. At operation 304, the method comprises receiving, at the receiver 110, the transmitted sound wave, the receiver mounted to the second arm 106b of the bracket 106. The bracket is mounted to the vacuum electricai device, and the first and second arms are disposed on opposite sides of the vacuum electrical device. At jo operation 306, the method comprises detecting a low vacuum condition based on the transmitted sound wave 112b (or through wave) received at the receiver. Optionally, detecting a low vacuum condition based on the transmitted sound wave can comprise using the amplitude of the detected through wave 112b to determine a 15 vacuum condition within the device 104 based on one or more predetermined relationships between through wave amplitude and internal pressure within the device. The amplitude of the initial wave 112a transmitted into the device 104 can be compared to the amplitude of the wave 112b transmitted through the device 104 and to the receiver, and the comparison may be used to determine a vacuum condition 20 within the device 104 based on one or more predetermined relationships between through wave amplitude and interna! pressure within the device.

Claims

1. An apparatus (102) for detecting a low vacuum condition within a vacuum electrical device (104), the apparatus comprising:5 a bracket (106) configured to be mounted to the vacuum electrical device, thebracket comprising first and second arms disposed on opposite sides of the vacuum electrical device;a transmitter (108) coupled to the first arm of the bracket and configured to transmit a generated sound wave (112a) into the vacuum electrical device; and jo a receiver (110) coupled to the second arm of the bracket and configured toreceive the. transmitted sound wave (112b).

2. The apparatus of claim 1, wherein the bracket is configured such that there is a physical separation between the first and second arms and the vacuum electricalJ5 device.

3. The apparatus of claim 1 or claim 2, further comprising processing means (114) configured to detect a low vacuum condition based on the transmitted sound wave (112b) received at the receiver.

204. The apparatus of claim 3, wherein the low vacuum condition is detected based on an amplitude of the transmitted sound wave.

5. The apparatus of claim 3 or claim 4, wherein the processing means are further 23 configured to monitor a vacuum condition of the vacuum electrical device over a period of time, wherein the monitoring is periodic monitoring or continuous monitoring.

6. The apparatus of any one of claims 3 to 5, wherein the processing means are 30 configured to cause outputting of an alert in response to the detection of a Sow vacuum condition.

7. The apparatus of any preceding claim, wherein a low vacuum condition corresponds to a pressure within the vacuum electrical device of at least 1 mbar, 35 optionally a pressure of at least 10 mbar.8 The apparatus of any preceding claim, wherein the generated sound wave is an ultrasound wave.

9. The apparatus of any preceding ciaim, wherein the bracket is formed from an instating material.5 10. A system (100) comprising:the apparatus of any preceding ciaim; and a vacuum electrical device.

11. The system of claim 1.0, wherein the vacuum electrical device is a vacuum jo interrupter.

12. The system of claim 10 or claim 11, wherein the bracket is arranged between the vacuum electrical device and the transmitter and between the vacuum electrical device and the receiver, and wherein there is physical separation between the first and 15 second arms of the bracket and the vacuum electrical device.

13. An insulating switchgear (200) comprising the system of any of claims 10 to12, wherein an insulating medium is disposed between the vacuum electrical device and the apparatus.2014. The insulating switchgear of claim 13, wherein the insulating medium is one of: air, a gas or an oil.

15. A method (300) for detecting a low vacuum condition within a vacuum25 electrical device, the method comprising:transmitting (302), with a transmitter, a generated sound wave into the vacuum electrical device, wherein the transmitter is mounted to a first arm of a bracket;receiving (304), at a receiver, the transmitted sound wave, the receiver30 mounted to a second arm of the bracket, wherein the bracket is mounted to the vacuum electrical device and wherein the first and second arms are disposed on opposite sides of the vacuum electrical device; anddetecting (306) a low vacuum condition based on the transmitted sound wave.3513

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