SYSTEM AND METHOD FOR DETERMINING A POSITION OF A MOVABLE ARM OF A HIGH VOLTAGE DISCONNECTING SWITCH

Abstract

The present disclosure relates to a system for determining a position of a movable arm of a high voltage disconnecting switch. The system comprises a high voltage disconnecting switch with a movable arm for opening and closing the high voltage disconnecting switch and a time of flight sensor configured to determine a distance value indicating a distance between the time of flight sensor and the movable arm. The system further comprises a control device configured to determine, based on the distance value, whether the high voltage disconnecting switch is in an open state or in a closed state. Further, a method for determining a position of a movable arm of a high voltage disconnecting switch is provided.

Claims

1. A system (1) for determining a position of a movable arm (3) of a high voltage disconnecting switch (5), the system (1) comprising: a high voltage disconnecting switch (5) with a movable arm (3) for opening and closing the high voltage disconnecting switch (5); a time of flight sensor (7) configured to determine a distance value indicating a distance between the time of flight sensor (7) and the movable arm (3); and a control device (9) configured to determine, based on the distance value, whether the high voltage disconnecting switch (5) is in an open state or in a closed state.

2. The system (1) of claim 1, wherein the movable arm (3) is configured to rotationally move within a plane of the rotational movement and wherein the time of flight sensor (7) is arranged outside the plane and directed towards the plane, such that at least a part of the movable arm (3) is within a field of view of the time of flight sensor (7) during at least a part of a movement of the movable arm (3) from the closed state to the open state.

3. The system (1) of claim 1, wherein the movable arm (3) is configured to rotationally move within a plane of the rotational movement and wherein the time of flight sensor (7) is arranged within the plane and directed towards the movable arm (3), such that at least a part of the movable arm (3) is within a field of view of the time of flight sensor (7) in the closed state.

4. The system (1) of claim 3, wherein the time of flight sensor (7) is arranged such that the movable arm (3) is within the field of view of the time of flight sensor (7) both in the open state and in the closed state.

5. The system (1) of any one of claims 1 to 4, wherein the control device (9) is configured to determine a velocity of the movable arm (3), based on the distance value.

6. The system (1) of any one of claims 1 to 5, wherein the time of flight sensor (7) comprises an image sensor with a plurality of pixels, the image sensor being configured to output a distance value for each one of the plurality of pixels, wherein the control device (9) is configured to determine whether the high voltage disconnecting switch (5) is in the open state or in the closed state based on the plurality of distance values for the plurality of pixels.

7. The system (1) of claim 5, wherein the time of flight sensor (7) comprises an image sensor with a plurality of pixels, the image sensor being configured to output a distance value for each one of the plurality of pixels, wherein the control device (9) is configured to determine the velocity of the movable arm (3) based on the plurality of distance values for the plurality of pixels.

8. The system (1) of any one of claims 1 to 7, wherein the control device (9) is further configured to switch on at least one additional sensor in response to the time of flight sensor (7) detecting a change in the distance value.

9. The system (1) of any one of claims 1 to 8, wherein the control device (9) is further configured to switch off at least one additional sensor in response to the time of flight sensor (7) detecting no change in the distance value for at least a predetermined time.

10. A method for determining a position of a movable arm (3) of a high voltage disconnecting switch (5), the method comprising: moving a movable arm (3) of a high voltage disconnecting switch (5) for opening or closing the high voltage disconnecting switch (5); determining, with a time of flight sensor (7), a distance value indicating a distance between the time of flight sensor (7) and the movable arm (3); and determining, based on the distance value, whether the high voltage disconnecting switch (7) is in an open state or in a closed state.

11. The method of claim 10, further comprising: determining a velocity of the movable arm (3), based on the distance value.

12. The method of claim 10 or 11, wherein the time of flight sensor (7) comprises an image sensor with a plurality of pixels, the image sensor outputting a distance value for each one of the plurality of pixels, wherein the method further comprises: determining whether the high voltage disconnecting switch (5) is in the open state or in the closed state based on the plurality of distance values for the plurality of pixels.

13. The method of claim 11, wherein the time of flight sensor (7) comprises an image sensor with a plurality of pixels, the image sensor outputting a distance value for each one of the plurality of pixels, wherein the method further comprises: determining the velocity of the movable arm (3) based on the plurality of distance values for the plurality of pixels.

14. The method of any one of claims 10 to 13, further comprising: switching on at least one additional sensor in response to the time of flight sensor (7) detecting a change in the distance value.

15. The method of any one of claims 10 to 14, further comprising: switching off at least one additional sensor in response to the time of flight sensor (7) detecting no change in the distance value for at least a predetermined time.

Description

[0057] The present disclosure shall be further explained with reference to the enclosed figures. These figures schematically show:

[0058] FIG. 1 a schematic representation of a system for determining a position of a movable arm of a high voltage disconnecting switch according to the present disclosure;

[0059] FIG. 2 an arrangement of the movable arm and the time of flight sensor according to a first embodiment;

[0060] FIG. 3 an arrangement of the movable arm and the time of flight sensor according to a second embodiment;

[0061] FIG. 4 an arrangement of the movable arm and the time of flight sensor according to a third embodiment;

[0062] FIG. 5 a flow diagram of a method for controlling at least one additional sensor;

[0063] FIG. 6 a long term measurement of a distance value for determining the stability of the sensor;

[0064] FIG. 7 an exemplary measurement of a movement of the movable arm according to the first embodiment; and

[0065] FIG. 8 an exemplary measurement of a movement of the movable arm according to the third embodiment.

[0066] In the following, without restriction, specific details will be provided, for providing a complete understanding of the present disclosure. It shall be appreciated by the person skilled in the art that the present disclosure can be embodied in other embodiments that may differ from the details provided below. For example, in the following, specific configurations of a high voltage disconnecting switch will be described and shown in the figures, which are not to be understood as limiting. Different embodiments and configurations, e.g., of the switch, are possible.

[0067] A core idea of the present disclosure is the use of a time of flight (ToF) sensor for determining an operational state (open state or closed state) of a high voltage disconnecting switch.

[0068] The time of flight technique lead to the development of time of flight sensors with a single pixel or with multiple pixels. In the latter case, the sensor may also be referred to as time of flight camera since a 3-dimenional image (or depth image) may be recorded. Although the present disclosure is described in the context of time of flight sensors having a two-dimensional pixelated image sensor (i.e., sensors with multiple pixels), the present disclosure shall not be limited to such devices and also a one pixel sensor may be used, which is only able to record one distance value at a given time (i.e., only one time-dependent distance value).

[0069] Commercially available devices are allowing free programming of multi pixel ToF circuits to measure distances and angles.

[0070] The sensors of the present disclosure are based on the time of flight (ToF) principle, which is the measurement of the time t taken by a laser pulse to travel a distance through a medium (e.g., air). Depending on the distance of an object, each pixel on the image sensor receives the reflected/scattered pulse with a delay. A microcontroller to evaluate a velocity, a path length D or a surface property uses the information.

t=2*D/c,

[0071] wherein c is the speed of light in the medium.

[0072] The pulse duration T defines the maximum measurable distance Dmax:

Dmax=c*T/2

[0073] A ToF sensor may comprise an image sensor with multiple pixels, a laser diode and a micro controller. The laser and the image sensor are optimized at 850 nm wavelength to minimize an impact from the environment.

[0074] Depending on the divergence a of an optical system of the sensor (comprising, e.g., a lens), the sensor can cover an area A (field of view) of:

A=*tan.sup.2()*D.sup.2,

[0075] wherein D is the distance.

[0076] A general schematic representation of a system 1 for determining a position of a movable arm 3 of a high voltage disconnecting switch 5 is shown in FIG. 1. The system 1 comprises the high voltage disconnecting switch 5 with the movable arm 3 for opening and closing the high voltage disconnecting switch 5 and a time of flight sensor 7 configured to determine a distance value indicating a distance between the time of flight sensor 7 and the movable arm 3. The system 1 further comprises a control device 9 configured to determine, based on the distance value, whether the high voltage disconnecting switch 5 is in an open state or in a closed state.

[0077] The system 1 is integrated in an electrical substation, wherein the switch 5 provides a disconnecting switch function for the substation, according to known principles. Further, the switch 5 may be operated by an electric actuator (such as an electric motor) under the control of a control device of the electrical substation. For example, the control device for the switch 5 may be the same as the control device 9 for the sensor 7.

[0078] As schematically shown in FIG. 1, the arm 3 carries out a swivel movement (or rotational movement) when the switch 5 is opened or closed. During this swivel movement, the arm 3 moves within a plane (in the following: plane of rotational movement).

[0079] In a closed state of the switch 5, a first contact portion 11 provided at one end of the arm 3 is in physical and electrical contact with a second contact portion 13 of the switch, such that current can flow through the switch 5. In an open state of the switch 5, the two contact portions 11, 13 are physically separated from each other by air and no current can flow. For the following considerations, it is of subordinate relevance whether the second contact portion 13 is provided fixed or whether it is itself provided at an end portion of a second movable arm of the switch 5. The following details are applicable to both situations.

[0080] The sensor 7 is positioned such that a distance value measured by the sensor 7 changes when the switch 5 changes its state from the closed state to the open state and vice versa. For this purpose, at least a part of the arm 3 is within a field of view of the sensor 7, at least for part of the movement from the closed state to the open state.

[0081] The control device 9 comprises a processor 15 and a memory 17. In the memory 17, instructions are stored that cause the processor 15 to carry out at least one of the methods described herein. In particular, the control device 9 is configured to determine, based on signals received by the sensor 7, whether the switch 5 is in the open state or in the closed state. At least a part of the control device 9 may be located physically separated from the sensor 7 (e.g., outside the electrical substation) and, e.g., within a server or a cloud. The following figures focus on the structural arrangement of the switch 5 with regard to the sensor 7, wherein the control device 9 is not shown, although it is part of the system 1.

[0082] FIG. 2 shows a first embodiment of an arrangement of the sensor 7 with regard to the movable arm 3. The sensor 7 comprises a microcontroller, a mount, a laser diode, an image sensor, and optics. One method for clearance detection is to place the sensor 7 beneath the movable arm 3, as shown in FIG. 2.

[0083] In the embodiment of FIG. 2, the movable arm 3 is configured to rotationally move within a plane of the rotational movement and the time of flight sensor 7 is arranged outside the plane. In the Cartesian coordinate system defined with regard to FIG. 2, the plane of the rotational movement is parallel to a x-y-plane. The left part of FIG. 2 shows a side view of the system and the right part of FIG. 2 shows a top view of the same system. As shown in FIG. 2, as an example, the arm 3 (and, thus, the plane of the rotational movement) is arranged 2 m above ground level.

[0084] The sensor 7 is directed towards the plane, such that at least a part of the movable arm 3 is within a field of view 19 of the time of flight sensor 7 during at least a part of a movement of the movable arm 3 from the closed state to the open state.

[0085] The left part of FIG. 2 shows the switch 5 in the closed state and the right part of FIG. 2 shows the switch in an open state.

[0086] As shown in FIG. 2, the arm 3 carries out a swivel movement in order to bring the switch from the closed state to the open state and vice versa. In the example shown in FIG. 2, the field of view 19 of the sensor 7 is positioned such that, in the closed state (see left part of FIG. 2), a part of the arm 3 is within the field of view 19.

[0087] In the present embodiment, but also in the other embodiments discussed herein, the sensor 7 may permanently output laser pulses and, therefore, may permanently record distance values that are evaluated by the control device 9. The control device 9 therefore records a time-dependent distance value. In case a plurality of pixels are considered, the control device 9 records a time-dependent distance value for each pixel.

[0088] The control device may therefore determine whether the switch 5 is in the closed state or the open state, as follows.

[0089] In a one-pixel embodiment: When the detected distance value is below a predefined threshold, the control device 9 determines that the switch 5 is in the closed state. At all other times, the control device 9 determines that the switch 5 is in the open state.

[0090] In a multi-pixel embodiment: As shown in the right part of FIG. 2, different sub-areas may be defined in the field of view of the sensor 7, such that each sub-area represents a particular state of the switch 5. The sub-areas correspond to one or more detection areas of one or more pixels of the sensor 7. When a pixel of the respective sub-area detects a distance value below a predefined threshold value, the control device 9 determines that the arm 3 is located in this sub-area. Hence, it can be determined, e.g., whether the arm 3 of the switch 5 is in the closed state, a spark gap area, a safe area, or in the open state. Thereby, between the open state and the closed state, intermediate states may be defined.

[0091] FIG. 3 shows a second embodiment, wherein the sensor 7 is positioned on the same level as the movable arm 3. In other words, the time of flight sensor 7 is arranged within the plane of the rotational movement. The switch 5 and its arm 3 may be the same as the one described with regard to FIG. 2. However, the sensor 7 is positioned 2 m above the ground level, in the plane of the rotational movement of the arm 3. The sensor is directed towards the movable arm 3, such that at least a part of the movable arm 3 is within the field of view 19 of the time of flight sensor 7 in the closed state. In the embodiment of FIG. 3, the viewing direction of the sensor 7 is perpendicular to the arm 3 in the closed state.

[0092] Both the left part and the right part of FIG. 3 are top views of the system 1 (i.e., along a z-direction). The left part of FIG. 3 shows the switch 5 in its closed state and the right part of FIG. 3 shows the switch 5 in an intermediate state. In the open state, the arm 3 would be oriented along the y-direction.

[0093] As shown in FIG. 3, the sensor 7 may monitor the distance to the arm 3 both in the closed state and when the arm 3 leaves the closed state towards the open state.

[0094] The control device 9 may therefore determine whether the switch 5 is in the closed state or the open state, as follows.

[0095] In a one-pixel embodiment: When the detected distance value is below a predefined threshold, the control device 9 determines that the switch 5 is in the closed state.

[0096] When the distance value is above the predefined threshold, the switch is determined to be in an intermediate state and when the distance value is above a second predefined threshold value, the control device 9 determines that the switch 5 is in the open position.

[0097] In a multi-pixel embodiment: More pixels may be evaluated to increase the reliability of the method.

[0098] FIG. 4 shows a third embodiment similar to the second embodiment, wherein the sensor 7 is arranged in the plane of the rotational movement of the arm 3. FIG. 4 shows a top view along the z-axis. A difference of the arrangement of FIG. 4 with regard to FIG. 3 is that a viewing direction of the sensor 7 is 45 with regard to the arm 3 in the closed state. In this arrangement, it is ensured that the arm 3 is in the field of view of the sensor 7 both in the open state and in the closed state (both states are shown in FIG. 4).

[0099] The control device 9 may therefore determine that the switch 5 is in the closed state, when the measured distance is within a predefined range and that the switch 5 is in the open state, when the measured distance is within a different predefined range. Values in between the ranges may be assigned to intermediate states of the switch 5.

[0100] The switch arms 3 are not in operation all the time and therefore there would be many unnecessary data be generated. A ToF sensor 7 can be used in a standby mode, where it only acquires data when there has been movement within a certain time. This can also be used to trigger other sensors.

[0101] FIG. 5 shows a flow diagram of a possible interaction with other sensors. When the algorithm starts, no sensor is generating an output unless the ToF sensor 7 records a movement of the switch arm 3. With the first movement of the switch arm 3 all the connected sensors are started/unpaused until the arm did not move for more than a predefined time in the off position. If so, all sensors will be paused again. As indicated in FIG. 5, the predefined time may be one day (24 h), but it is not limited to that.

[0102] The above method may be regarded as a master/slave behavior. The time of flight sensor 7 is a master sensor, which triggers an on/off state of other sensors of the electrical substation. When the distance value measured by the sensor 7 does change, all of the other sensors (slave sensors) are switched on, such that they record data and generate output. When the distance value measured by the sensor 7 does not change for longer than a predetermined time, the other sensors may be switched off again. This may help to save energy, since the operation of the other sensors may be energy consuming. One example of another sensor is a camera, which may start acquiring images when it is switched on. The operation of FIG. 5 may be controlled by the control device 9. The data of the other sensors 9 may be transmitted to the control device 9.

[0103] The stability of the time of flight measurements is shown in FIG. 6 for a long term measurement. The measurement has been performed on a metal arm 3 of a high voltage disconnecting switch 5 with about 60,000 measurement points. The sensor 7 has been measuring for 40 minutes at a constant distance. From the measured data, a standard deviation of 0.0015 m can be derived. This equals a percentage of 0.68%. The measurement of FIG. 6 shows that available time of flight sensors are sufficiently stable for the purpose described in the present disclosure.

[0104] FIG. 7 shows a measurement of a sensor 7 that was conducted in the configuration as shown in FIG. 2. For this measurement, a time of flight sensor 7 was placed 2 m below a movable metal arm 3. While the ToF sensor 7 was measuring, the arm 3 moved from the left side (here called TX) to the right side (here called RX). In FIG. 7 the signals (i.e., time-dependent distance values) of three different pixels is plotted, namely r(4, 2) 71, r(5, 2) 73, and r(6, 2) 75. Those pixels are positioned next to each other on the sensor 7. Depending on from which side the arm 3 is moving, either pixel r(4, 2) or r(6, 2) is giving a signal first. In FIG. 7, a movement from left to right (TX to RX) and from right to left (RX to TX) can be observed. Based on a delay between the signals of r(4, 2) and r(6, 2), the velocity of the arm 3 can be calculated by the control device 9.

[0105] FIG. 8 shows a measurement of a sensor 7 that was conducted in the configuration as shown in FIG. 4. For this measurement, the sensor 7 was placed on the same level of the metal arm 3 and the distance towards the arm 3 was measured versus time. Similar to FIG. 7, also FIG. 8 shows the curves of three different adjacent pixels of the sensor 7, namely r(3, 2) 81, r(4, 2) 83, and r(5, 2) 85.

[0106] During the first 40 seconds, the arm 3 has been moving away from the sensor 7 and after that, it moved back towards the sensor 7. The three lines 81, 83, 85 represent different pixels, wherein each pixel detects a slightly different part of the arm 3 than the other pixels, since the detection areas of the pixels differ from each other.

[0107] Based on the curves of FIG. 8, a position of the arm 3 can be reliably determined. Further, a velocity may be determined based on a gradient of one of the curves.

[0108] In one or more embodiments of the present disclosure, as soon as the sensor 7 detects a movement of the arm 3, the sensor 7 starts its algorithm. The microcontroller of the sensor 7 then saves the status request and the distance measurement of a certain amount of pixels in a temporary cache. Further, the distance measurement may be directly saved in the memory of the control device 9.

[0109] The distance is translated into the position of the arm 3 in the system 1 and, optionally, its velocity. At defined positions, the control device 9 can start other sensors/algorithms. The data may be depicted on a screen, a display on the sensor 7 or on the control device 9, or it is saved in a file (e.g., a .txt file) on the control device 9 and/or in a cloud.

[0110] An additional lens can be used to increase or decrease the divergence of the sensor 7. The sensor 7 can also be coupled to optical fibers. That way, the distance between the electrical sensor module and the electromagnetic field of the switch 5 can be increased.

[0111] Embodiments described herein provide a reliable technique for determining a state (open state or closed state) of a high voltage disconnecting switch.