This application is based upon and claims the benefit of priority from Japanese Patent Applications No. 2020-186625, filed Nov. 9, 2020, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a system and method.
In an electric facility such as an electric power substation or the like, at the time of an inspection, construction or the like, the supply of electricity is stopped. At this time, for confirmation of safety, work for confirming that the supply of electricity is really cut off is carried out. In the case of a high-voltage facility, a voltage detector or current detector installed at a tip of an insulating rod is made close to a conductor such as an electric wire or the like, whereby confirmation of the electric-power shutdown is carried out.
However, because of the work of making a long rod close to the electric wire, an elongated instrument is required and, the work itself requires safety confirmation and thus has been troublesome work. For this reason, a voltage detecting method and current detecting method requiring no accession to the electric wire have been desired.
Because of such a situation, as a noncontact voltage detecting method requiring no accession to the electric wire, a method or the like which utilizes reflection of a beam of light such as laser light to detect vibration of the electric wire, thereby voltage detection is proposed. However, under the existing circumstances, voltage detection using the insulating rod and voltage detector is carried out in an ongoing manner. As the reason why the device of the voltage detecting method utilizing reflection of a beam of light is not used, cost, difficulty in usage, and the like are conceivable. Regarding the difficulty in usage, that it is necessary to accurately apply laser light to an objective electric wire or wire group, and hence the work of setting the device in a stable state by using a tripod or the like, and adjusting the radiation direction of laser light to the electric wire is required can be pointed out. Accordingly, a lot of troublesomeness hindered the method from becoming an alternative means or auxiliary means of the voltage detection using the insulating rod and voltage detector.
As described above, in the noncontact voltage detection using, for example, laser light, there has been problems in the usability, such as setting of the device, selection of the object of voltage detection, and the like.
Embodiments will be described hereinafter with reference to the accompanying drawings.
In general, according to one embodiment, a system includes a radar and a controller. The radar includes at least one first antenna and at least one second antenna. The at least one first antenna transmits a first transmission wave at a first time and transmits a second transmission wave at a second time different from the first time. The at least one second antenna receives reflected waves of the first transmission wave and the second transmission wave.
In the system 1 of this embodiment, a radar configured to radiate an electric wave toward an object (electric wire 2) to be measured and receive the reflected wave is used. The antenna unit 10 includes a millimeter-wave radar 11. In the antenna unit 10, a plurality of antenna elements 12 (see
The radar obtains a distance by measuring a temporal difference between transmission and reception. The millimeter-wave radar 11 using the 60 GHz band or 76 GHz band can legally use a wide bandwidth of 1 GHz or more, and hence is used as a frequency modulated continuous wave (FMCW) radar. As the frequency-modulated wave, in particular, the chirp in which the frequency monotonically increases (or decreases) is used.
As shown in
The received signal is a signal transmitted the time corresponding to going to and back from the object ago, and hence there is a frequency difference between the frequency of received signal and frequency of the signal currently transmitted, i.e., frequency used for detection. Accordingly, as shown in
Returning to
The control/display unit 20 includes a transmission processor 21, a reception processor 22, a first signal processor 23, Bin accumulator 24, and Bin selector 25. Further, the control/display unit 20 includes a plurality of second signal processors 26, a vibration detecting/determining unit 27, and a display 28. Each of the units (21 to 27) of the control/display unit 20 may be realized by hardware (electrical circuits) or may be realized by the processor (not shown) in the control/display unit 20 by executing programs.
The transmission processor 21 creates a chirp signal the frequency of which monotonically increases (or decreases) by using, for example, a synthesizer, and transmits a transmission wave corresponding to the chirp signal by using the antenna unit 10. The reception processor 22 outputs the signal of the reception wave received by the antenna unit 10 as the reflected wave of the transmission wave transmitted by the antenna unit 10.
The first signal processor 23 mixes the signal of the reception wave output from the reception processor 22 and latest chirp signal (signal of the transmission wave) created by the transmission processor 21 with each other to thereby create IF signals, and separates the IF signals from each other for each frequency. That is, the mixer 231 in
When the transmission wave of the millimeter-wave radar is reflected from a plurality of objects at different distances, by separating the IF signals from each other for each frequency, it is possible to easily obtain received signals separated from each other for each distance. There are various methods for acquiring a signal for each frequency, in the system 1 of this embodiment, signals for the individual frequencies are obtained by using fast Fourier transformation (FFT). This processing is called Range-FFT. Further, the signal for each frequency is called a Range-Bin or Bin. By using a plurality of chirp signals to be transmitted at different transmission times, it is possible to detect the vibration of the electric wire 2 which is the object by a change in the signal of the Bin indicating the frequency corresponding to the distance at which the object exists.
The Bin accumulator 24 accumulates signals for the individual frequencies, i.e., the Bins acquired by the first signal processor 23 to the number corresponding to at least two generations. The expression “the Bins of the number corresponding to two generations” implies, when the chirp signals are created/transmitted at intervals of the time Tc, both the Bin concerning the latest chirp signal, and Bin concerning the chirp signal one signal before, i.e., Bin concerning the chirp signal the time Tc ago.
When parameters concerning detection of the electric wire 2 are input, the Bin selector 25 selects Bins coincident with the parameters from the Bins accumulated in the Bin accumulator 24 and supplies the selected Bins one by one and separately to the individual second signal processors 26. Parameters that can be input to the Bin selector 25 will be described later. When no parameters are input thereto, the Bin selector 25 selects all the Bins and supplies the Bins one by one and separately to the individual second signal processors 26. When the second signal processors 26 fire realized by the program, each of the second signal processors 26 may have a multitasking function.
The second signal processor 26 subjects the signal for each Bin supplied from the Bin selector 25 to FFT to thereby obtain the frequency spectrum and acquire the frequency components of the vibration occurring to the electric wire 2 in the case where the electric wire 2 is in the energized state. This FFT is called Slow-FFT.
The vibration detecting/determining unit 27 determines whether or not the predetermined frequency component (frequency component of vibration occurring to the electric wire 2 in the case where the electric wire 2 is in the energized state) to be acquired by each of the plurality of second signal processors 26 is greater than or equal to a threshold. When the frequency component greater than or equal to the threshold is acquired, the vibration detecting/determining unit 27 determines that an electric wire 2 in the energized state exists at a distance corresponding to the frequency of the Bin to be processed by the second signal processor 26 concerned. The vibration detecting/determining unit 27 displays information indicating presence/absence of detection of the electric wire 2 in the energized state and information and the like indicating the position at which the detected electric wire 2 in the energized state exists on the display 23.
The electric wave propagates from the antenna 12 while spreading cut in a conical shape. Although the angle (directivity) of spreading out in the conical shape can be set by the configuration of the antenna 12, the characteristics that the electric wave propagates while spreading out in the conical shape stay constant. Accordingly, as compared with the laser light which linearly propagates while hardly spreading out, the electric wave can reach a wider range of area and makes it possible to receive reflected waves from objects in the wide range of area. The radar 11 of this embodiment includes a plurality of transmitting antennas 12a or a plurality of receiving antennas 12b in order to set directivity. Each of the antennas 12 may have directivity different from any other antennas 12. Alternatively, by processing signals of a plurality of antennas 12 and using the antennas 12 as the phased array antenna, the radar 11 acquires electrically controllable directivity. Accordingly, by only directing the radar 11 to the direction of the electric wire in a rough way or by only electrically controlling the directivity of the radar 11 in addition to roughly directing the radar 11 to the electric wire, it is possible to select the electric wire existing in that direction as the object of voltage detection and detect vibration of the electric wire in the energized state.
In a first example shown in
In a second example shown in
The control/display unit 20 displays the detection result on the electric wire inside the image or the camera 13 in a superposing manner as shown in, for example,
When a pole, beam, and non-energized electric wire exist around the electric wire in the energized state, reflected waves from them are also received. In order to carry out voltage detection, it is necessary to detect only the vibrating electric wire. For that purpose, it is sufficient if only an object vibrating at a predetermined frequency is selected. In the system 1 of this embodiment, it is possible to extract only the predetermined frequency component from the frequency spectrum of the output of Slow-FFT described previously.
In the system 1 of this embodiment, unless the frequency of vibration is already known, it is not possible to detect the Bin corresponding to the distance at which the electric wire in the energized state exists, and hence the frequency of vibration is set in advance. Alternatively, the frequency of the AC voltage (current) of the object to be measured and frequency of the vibration thereof are correspondent to each other, and hence the frequency of the AC power may also be set. It may be made possible to input the set contents to the second signal processor 26 as a parameter. That is, it may be made possible to change the frequency of vibration of the measuring object.
In the above description, in order to detect the frequency of vibration, the second signal processor 26 uses Slow-FFT, i.e., Fourier transformation to thereby obtain the frequency spectrum. However, the second signal processor 26 need not obtain the frequency spectrum of a wide frequency band and, it is sufficient if the second signal processor 26 detects presence/absence of the predetermined frequency component. When the predetermined frequency component is to be obtained, correlation, band-pass filtering, frequency detection, resonance, and the like can also be used.
Further, when the range of the distance to be measured is specified in advance, it becomes possible to reduce the number of Bins to be determined, reduce the throughput, and improve the detection accuracy. For example, when Bins are set at intervals of 5 cm, in the distance of 10 m, 200 Bins exist. Here, if the distance is roughly set within a range from 5 m to 7 m by visual measurement or the like, it becomes sufficient if only 40 Bins are processed. It is possible to input the set contents to the Bin selector 25 as parameters. The Bin selector 25 selects only Bins coincident with the input parameters from among the Bins accumulated in the Bin accumulator 24. The measurement range may be set by manipulating the frame-like mark b1 indicating the radiation range and displayed on the image of the camera in a superposing manner. The set contents change the electrically-controllable directivity, and make the radiation range to be displayed and directivity of the radar coincident with each other.
Further, in the above description, an example in which the position of the electric wire in the energized state is identified by the directivity of the radar 11 is shown. In place of the above, it is also allowable to carry out Range-FFT and Slow-FFT for each of the antennas 12 to thereby obtain the distance to the electric wire 2 in the energized state for each of the antennas 12. It is possible to carry out position estimations of a plurality of electric wires in the energized state based on the antenna directivity and distance between the antenna and electric wire as shown in
Further, even when there are a plurality of electric wires in the energized state within the measurement range, it is possible to detect these electric wires independent of each other based on the antenna directivity or selection of the Bin or the Range-FFT, i.e., the distance. When there are a plurality of detection results, the existence of the results are simultaneously displayed on the screen on which the measurement result is to be displayed. When the detection results are displayed on the electric wires of the camera image in a superposing manner, each of the detection results is displayed on each of the plurality of electric wires in the energized state in a superposing manner. Even when energization of one of three electric wires of three-phase AC is stopped due to disconnection or the like, it is possible to observe the two electric wires in the energized state.
The system 1 transmits a frequency-modulated wave the frequency of which monotonically increases (or decreases) as a transmission wave (S101). The system 1 receives the reflected wave of the transmission wave transmitted in step S101 as a reception wave (S102). The system 1 mixes the transmission wave and reception wave with each other to thereby create an intermediate frequency (IF) signal (S103). The transmission wave in step S103 is not the bygone transmission wave transmitted in step S101, but is the latest transmission wave transmitted at the time of processing of step S103.
The system 1 subjects the IF signal created in step S103 to first signal processing (Fourier transformation) to thereby acquire a signal (Bin) for each frequency (S104). Based on the setting (parameter) carried out in advance, the system 1 selects Bins to be made the objects of the subsequent processing from among the Bins acquired in step S104 (S105).
The system 1 uses n signals of the same Bin M, i.e., Bin M (t0), Bin M (t1), . . . , and Bin M (tn-1) acquired from the n reception waves which are the reflected waves of the n transmission waves the transmission times of which are t0, t1, . . . , and tn-1, the n signals Bin M (t0), Bin M (t1), . . . , and Bin M (tn-1) being the X signals selected in step S105, i.e., Bin 1, Bin 2, . . . , Bin M, . . . , and Bin X to thereby execute second signal processing (vibration detection) (S106). The second signal processing is executed for each of the X Bins. The system 1 determines with respect to the detection results of step S106 whether or not the predetermined frequency component has been detected (S107). When the predetermined frequency component is detected (S107: Yes), the system 1 displays information indicating detection of the object or information indicating that an object exists at the distance corresponding to the Bin regarding which the predetermined frequency component is detected (S108).
As described above, in the system 1 of this embodiment, the radar 11 configured to transmit, from the antenna 12, an electric wave which propagates while spreading out in a conical shape, and reaches a wide range of area as compared with the laser light that linearly propagates while hardly spreading out is used, and thus it is possible, by only roughly directing the radar 11 to the direction of the electric wire, and electrically controlling the directivity thereof, to select the electric wire existing in the direction as a voltage detection object, and detect the vibration of the electric wire in the energized state. That is, the system 1 of this embodiment realizes noncontact voltage detection in which the device can be used based on unstable setting such as hand-holding, simplified mount or mobile object, e.g., a drone, and the object of voltage detection is automatically selected.
The system 1 of this embodiment can also be configured such that signal processing to be carried out for the purpose of detecting an electric wire in the energized state is executed in a unified manner at a distant place network-connected with the work-site. For example, as shown in
Further, as shown in, for example,
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Number | Date | Country | Kind |
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2020-186625 | Nov 2020 | JP | national |