Condensation risk detection device

Abstract

To provide a dust accumulation detection method and a dust accumulation detection device, each enabling removal of temporary influence due to external environment, and thereby enabling presence of dust accumulation to be accurately detected.SOLUTION: A dust accumulation detection device comprises: a light emission portion irradiating a prescribed portion of electric equipment with light; a light detection portion detecting light reflected from the prescribed portion or passed through the prescribed portion; a measurement terminal generating voltage according to current flowing in the light detection portion while the prescribed portion is irradiated with light from the light emission portion; a measurement portion measuring voltage of the measurement terminal; and a detection portion detecting accumulation of dust on the prescribed portion of the electric equipment. The measurement portion generates time series data by repeating measurement of the voltage for a prescribed period, the detection portion uses a movement center value calculated from the time series data to detect presence of the dust accumulation. Therefore, temporary affection due to external environments of the dust accumulation detection device can be removed, and presence of the dust accumulation can be detected accurately.SELECTED DRAWING: Figure 15

Description

[Technical Field]

[0001] The present invention relates to a dust accumulation detection device, a dust accumulation detection method, and a condensation risk detection device for detecting dust adhering to or accumulating on electrical equipment, electrical facilities, etc. [Background technology]

[0002] When dust flies in from outside and accumulates on electrical equipment or facilities, the risk of malfunction and insulation deterioration increases. To ensure the normal operation of these devices and facilities, it is necessary to take measures such as regular cleaning.

[0003] Techniques for evaluating the degree of dust adhesion are known. For example, in Patent Document 1 listed below, two sets of electrodes are prepared, each with a humidity-sensitive film formed on it that allows current to flow more easily as humidity increases. One set is placed in an environment where salt adhesion occurs, and the other is placed in an environment where salt adhesion is difficult. The level of contamination (salt adhesion) is determined by measuring and comparing the current values ​​flowing between each set of electrodes. In addition, in Patent Document 2 listed below, a light-transmitting plate (dust accumulation plate) is placed inside an air conditioning duct, a light source and a photosensor are placed on either side of it, and dust accumulation is detected as the amount of light transmitted through the dust accumulation plate is measured.

[0004] Patent Document 1 has the problem that it can only detect salt or dust containing salt, and is insufficient for detecting the risk of poor contact or malfunction of equipment caused by the adhesion of general dust. Patent Document 2 does not take into consideration the temperature dependency of the light source and photodetector, and effective detection is only possible in a dark place with constant ventilation, and it is necessary to arrange the light source and photodetector opposite each other, which makes it difficult to reduce the number of parts.

[0005] To solve the above problems, Patent Document 3 (see below) discloses a dust accumulation detection device that can accurately detect dust by eliminating the effects of temperature dependency and deterioration over time, regardless of the type of dust. This dust accumulation detection device includes a light-emitting unit that irradiates a predetermined portion of an electrical device with light, a light-detecting unit that detects light that has passed through the predetermined portion or that has been reflected by the predetermined portion, a control unit that controls the on / off of the light-emitting unit, an evaluation unit that evaluates the level of dust accumulation in the predetermined portion based on the intensity of light detected by the light-detecting unit when the control unit turns on the light-emitting unit and the intensity of light emitted by the light-emitting unit, and a determination unit that determines whether the intensity of light detected by the light-detecting unit when the light-emitting unit is not outputting light is equal to or less than a predetermined threshold. When the determination unit determines that the intensity is equal to or less than the predetermined threshold, the evaluation unit evaluates the level of dust accumulation. This eliminates the effects of temperature dependency and deterioration over time, regardless of the type of dust, allowing for accurate dust detection. The specified portion also has a plurality of reflective surfaces, including a reflective surface with an L-shaped cross section, and the light-emitting unit and the light-detecting unit are arranged so that light output from the light-emitting unit is reflected by the plurality of reflective surfaces and then detected by the light-detecting unit. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5488755 [Patent Document 2] Japanese Patent Application Publication No. 10-170438 [Patent Document 3] Japanese Patent Application Publication No. 2019-124531 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in field tests, in addition to long-term trends in measurements indicating dust accumulation, sudden temporary fluctuations in measurements were observed. Such fluctuations can lead to erroneous judgments. Furthermore, condensation is also a cause of insulation deterioration in electrical equipment, so it would be desirable to be able to evaluate the risk of condensation.

[0008] Therefore, a first object of the present invention is to provide a dust accumulation detection device and a dust accumulation detection method that can eliminate temporary influences from the external environment and accurately detect the presence or absence of dust accumulation.A second object of the present invention is to provide a condensation risk detection device that can evaluate the risk of condensation. [Means for solving the problem]

[0009] A dust accumulation detection device according to a first aspect of the present invention includes a light-emitting unit that irradiates light onto a predetermined portion of an electrical device, a light-detecting unit that detects light that has passed through or been reflected by the predetermined portion, measurement terminals that generate a voltage corresponding to a current flowing through the light-detecting unit when the predetermined portion is irradiated with light from the light-emitting unit, the measurement unit that measures the voltage at the measurement terminals, and a detection unit that detects dust accumulation in the predetermined portion of the electrical device, wherein the measurement unit repeatedly measures the voltage over a predetermined period to generate time-series data, and the detection unit detects the presence or absence of dust accumulation using a moving median calculated from the time-series data. This makes it possible to eliminate temporary effects of the external environment of the dust accumulation detection device and accurately detect the presence or absence of dust accumulation.

[0010] Preferably, the detection unit selects data measured during a period defined by a window from the time series data as target data for calculating the running median, the window being two days, thereby determining an appropriate running median and more accurately detecting the presence or absence of dust accumulation.

[0011] More preferably, the dust accumulation detection device further includes a humidity detection unit that detects the humidity around a predetermined portion of the electrical device, and instead of calculating a running median, the detection unit detects the presence or absence of dust accumulation using new time series data generated by repeatedly measuring voltage over a predetermined period of time, excluding voltage values ​​measured by the measurement unit when the humidity detected by the humidity detection unit is equal to or greater than a predetermined value and voltage values ​​equal to or greater than a predetermined threshold. This makes it possible to eliminate temporary effects of the external environment of the dust accumulation detection device and accurately detect the presence or absence of dust accumulation.

[0012] A condensation risk detection device according to a second aspect of the present invention includes a light-emitting unit that irradiates light onto a predetermined portion of an electrical device, a light-detecting unit that detects light that has passed through or been reflected by the predetermined portion, a measurement terminal that generates a voltage corresponding to a current flowing through the light-detecting unit when the light-emitting unit irradiates the predetermined portion, a measurement unit that measures the voltage at the measurement terminal, a first calculation unit that generates second time-series data of a running median from first time-series data acquired by the measurement unit by repeatedly measuring the voltage over a predetermined period, a second calculation unit that generates third time-series data by dividing the first time-series data by the second time-series data, and an evaluation unit that evaluates the risk of condensation on the predetermined portion of the electrical device. The evaluation unit compares the third time-series data with a predetermined threshold to calculate the frequency of voltage drops measured by the measurement unit and evaluates the risk of condensation based on the frequency. This allows for accurate evaluation of the risk of condensation without being affected by long-term voltage drops due to the progression of dust accumulation.

[0013] A dust accumulation detection method according to a third aspect of the present invention is a method for detecting dust accumulation in a predetermined portion of an electrical device using an apparatus including a light-emitting unit that irradiates light onto the predetermined portion of the device, a light-detecting unit that detects light that has passed through or been reflected by the predetermined portion, and a measurement terminal that generates a voltage corresponding to a current flowing through the light-detecting unit, the method including the steps of measuring the voltage of the measurement terminal while the predetermined portion is irradiated with light from the light-emitting unit, repeating the measurement step over a predetermined period to generate time-series data, and detecting the presence or absence of dust accumulation using a moving median calculated from the time-series data. This makes it possible to eliminate temporary effects due to the external environment of the device and accurately detect the presence or absence of dust accumulation. [Effects of the Invention]

[0014] According to the present invention, it is possible to accurately detect the presence or absence of dust accumulation by eliminating temporary influences from the external environment, and to accurately evaluate the risk of condensation without being affected by long-term voltage drops that accompany the progression of dust accumulation. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a dust accumulation detection device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing the arrangement of an optical detection system for detecting dust accumulation. [Figure 3] FIG. 3 is a circuit diagram showing an optical detection system for detecting dust accumulation. [Figure 4] FIG. 4 is a flowchart showing a dust accumulation amount estimation process performed by the dust accumulation detection device of FIG. [Figure 5] FIG. 5 is a cross-sectional view showing the arrangement of a photodetection system according to a third modified example. [Figure 6] FIG. 6 is a cross-sectional view showing an arrangement of a light detection system different from that shown in FIG. [Figure 7] FIG. 7 is a block diagram showing a schematic configuration of a dust accumulation detection device according to a fourth modified example. [Figure 8] FIG. 8 is a cross-sectional view showing the arrangement of the optical detection system of the dust accumulation detection device shown in FIG. [Figure 9] FIG. 9 is a cross-sectional view showing an arrangement of a photodetection system different from that shown in FIG. [Figure 10] FIG. 10 is a cross-sectional view showing the arrangement of a photodetection system according to a fifth modified example. [Figure 11] FIG. 11 is a circuit diagram showing a light detection system according to the sixth modified example. [Figure 12] FIG. 12 is a graph showing the results of the first example using the Kanto loam layer. [Figure 13] FIG. 13 is a graph showing the results of the second example regarding simulated dust (high reflectance) with different properties. [Figure 14] FIG. 14 is a graph showing the results of the second example regarding simulated dust (low reflectance) with different properties. [Figure 15] FIG. 15 is a block diagram showing a schematic configuration of a dust accumulation detection device according to the first embodiment of the present invention. [Figure 16]FIG. 16 is a flowchart showing a dust accumulation detection process performed by the dust accumulation detection device shown in FIG. [Figure 17] FIG. 17 is a graph showing data (trend data) that indicates long-term trends in the degree of dust accumulation and relative humidity. [Figure 18] FIG. 18 is a graph showing trend data obtained by excluding the measured values ​​at a relative humidity of 70% RH or higher from the trend data of dust accumulation shown in FIG. [Figure 19] FIG. 19 is a graph showing trend data obtained by excluding the measurement values ​​under the influence of external light from the trend data of dust accumulation shown in FIG. [Figure 20] FIG. 20 is a graph showing the change in the daily moving maximum value for trend data obtained by excluding the measured values ​​at a relative humidity of 70% RH or higher from the dust accumulation trend data shown in FIG. [Figure 21] FIG. 21 is a graph showing the change in the moving median value over two days for trend data obtained by excluding the measured values ​​at a relative humidity of 70% RH or higher from the dust accumulation trend data shown in FIG. [Figure 22] FIG. 22 is a block diagram showing a schematic configuration of a condensation risk detection device according to the second embodiment of the present invention. [Figure 23] FIG. 23 is a graph showing the difference in long-term changes (trend data) in the degree of dust accumulation depending on whether forced ventilation is present or absent. [Figure 24] FIG. 24 is a graph showing the change in the moving median value over two days for trend data obtained by excluding the measured values ​​at a relative humidity of 70% RH or higher from the trend data shown in FIG. [Figure 25] FIG. 25 is a graph showing the difference in short-term voltage fluctuation (trend data) depending on whether forced ventilation is performed or not. [Figure 26] FIG. 26 is a graph showing the difference in the duration and frequency of voltage drops depending on whether forced ventilation is performed or not. [Figure 27] FIG. 27 is a graph showing the changes in relative humidity, generated voltage, and creepage sheet resistance in a humidification simulation experiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] In the following embodiments, the same components are denoted by the same reference numerals, and have the same names and functions. Therefore, detailed description thereof will not be repeated.

[0017] (Related Embodiments of the Invention) (Configuration of dust accumulation detection device) Referring to FIG. 1 , a dust accumulation detection device 100 according to an embodiment of the present invention includes a light-emitting unit 102 that emits light, a power supply unit 104 that supplies power to the light-emitting unit 102, a light detection unit 106 that detects light, a control unit 108, a memory unit 110, a timer 112, a temperature detection unit 114, and a light-reflecting member 120. The dust accumulation detection device 100 also includes a power supply (not shown) for operating each unit, and operation devices (not shown) such as a computer keyboard and mouse for inputting instructions to the control unit 108. The light-emitting unit 102, the light detection unit 106, the temperature detection unit 114, and the light-reflecting member 120 are disposed within a device to be monitored for dust generation. The power supply unit 104, the control unit 108, the memory unit 110, and the timer 112 may be disposed in any location, either within the device to be monitored or outside the device.

[0018] Referring to FIG. 2, the light-emitting unit 102 is, for example, a light-emitting diode (hereinafter referred to as an LED). The light-emitting unit 102 is not limited to an LED, and may be any light-emitting element that can stably output light of a predetermined intensity in a predetermined direction for a predetermined period of time (for example, about one to several seconds). The wavelength of the light emitted by the light-emitting unit 102 is arbitrary as long as it can be detected by the light detection unit 106. The light emitted by the light-emitting unit 102 may be, for example, infrared light, visible light, or ultraviolet light. The power supply unit 104 supplies power to the light-emitting unit 102 for turning on the light-emitting unit 102 under the control of the control unit 108.

[0019] The light detection unit 106 is, for example, a phototransistor. The light detection unit 106 is not limited to a phototransistor, but may be any element that can detect light and output an electrical signal (for example, voltage or current) whose magnitude corresponds to the intensity (amount of light). It is preferable that the light detection unit 106 has the central wavelength of the light emitted by the light emission unit 102 near the center of its detection sensitivity.

[0020] The light reflecting member 120 is held by a holding member 122 and reflects light emitted from the light emitter 102 to make it incident on the light detector 106. The light reflecting member 120 has an L-shaped cross section, allowing the optical path from the light emitter 102 to the light detector 106 to be contained in a relatively narrow space. The two orthogonal surfaces on the light emitter 102 side are mirror surfaces that reflect the light from the light emitter 102. The light reflecting member 120 only needs to be arranged so that the two reflective surfaces form an angle of approximately 90°, and can be formed, for example, by bending a metal plate. The light reflecting member 120 may also be formed by joining two planar members with reflective surfaces so that they are approximately orthogonal to each other. The light emitter 102, the light detector 106, and the light reflecting member 120 constitute a light detection system.

[0021] The light emitting unit 102 and the light detecting unit 106 can be realized by, for example, a photoreflector, which is an element that houses an LED and a phototransistor in one package. This reduces the number of parts and allows the light detecting system to be formed compactly.

[0022] The control unit 108 is a CPU (Central Processing Unit) and controls the output of the power supply unit 104 to turn on or off the light-emitting unit 102. For example, when the control unit 108 outputs a high-level (e.g., 5 V) signal to the power supply unit 104, the power supply unit 104 supplies power to the light-emitting unit 102. This turns on the light-emitting unit 102. When the control unit 108 outputs a low-level (e.g., 0 V) ​​signal to the power supply unit 104, the power supply unit 104 stops supplying power to the light-emitting unit 102. This turns off the light-emitting unit 102 that was on.

[0023] Furthermore, the control unit 108 acquires, at a predetermined timing, an output signal from the light detection unit 106. For example, if the light detection unit 106 has an A / D conversion function, the control unit 108 acquires digital data output from the light detection unit 106. If the light detection unit 106 outputs an analog signal, the control unit 108 samples the input analog signal at predetermined time intervals to generate digital data.

[0024] The storage unit 110 is a volatile or non-volatile memory that stores data input from the control unit 108. The timer 112 receives a request from the control unit 108 and outputs the current time.

[0025] The temperature detection unit 114 is, for example, a temperature sensor (such as a thermistor, a resistance temperature detector, or a thermocouple), and is arranged around the light-emitting unit 102 and the light detection unit 106. The detected value (temperature) of the temperature detection unit 114 is input to the control unit 108.

[0026] FIG. 1 shows dust 190 accumulated on the horizontal surfaces of the light-reflecting member 120 and the holding member 122. Light emitted from the light-emitting unit 102 passes through the dust 190, is reflected by the horizontal surface of the light-reflecting member 120, passes through the dust 190 again, is reflected by the vertical surface of the light-reflecting member 120, returns parallel to the optical axis of the light-emitting unit 102, and is detected by the light-detecting unit 106. The amount of light measured by the light-detecting unit 106 varies depending on the amount of dust 190 accumulated on the light-reflecting member 120; the greater the amount of dust 190 accumulated, the smaller the measured value. The accumulation of dust inside the device increases over time after the device is installed. Therefore, by periodically measuring the amount of light detected by the light-detecting unit 106 while the control unit 108 controls the power supply unit 104 to turn on the light-emitting unit 102, the change in the level of dust accumulation can be observed. At this time, it is preferable that the control unit 108 uses the detection value of the temperature detection unit 114 to perform temperature correction of the detection value of the light detection unit 106 as described below.

[0027] An example of a light detection circuit using an LED for the light-emitting unit 102 and a phototransistor for the light-detecting unit 106 is shown in FIG. 3. Referring to FIG. 3, the light-emitting unit 102 includes an LED 130 and a resistor R1 connected in series between terminals 140 and 142. In FIG. 3, the light-reflecting member 120 is shown as a flat plate for convenience. The light-detecting unit 106 includes a phototransistor 132 and resistors R2 and R3 connected in series between terminals 144 and 146. When a DC voltage is applied from the power supply unit 104 between terminals 140 and 142 of the light-emitting unit 102 with terminals 142 and 146 grounded, the LED 130 emits light. When a predetermined DC voltage is applied between terminals 144 and 146 of the light detection unit 106 and light (emission light from the light-emitting unit 102 reflected by the light-reflecting member 120) is incident on the phototransistor 132, the phototransistor 132 turns on and a current flows (current flows between terminals 144 and 146). The control unit 108 measures the voltage generated at the measurement terminal 134 due to the resulting voltage drop. The value of the current flowing through the phototransistor 132 depends on the amount of light incident on the phototransistor 132, so the voltage measured at the measurement terminal 134 represents the amount of light incident on the phototransistor 132. Note that the resistors R1, R2, and R3 may have appropriate resistance values ​​according to the LED 130 and the phototransistor 132.

[0028] (Method for estimating dust accumulation amount) Using the voltage value measured using the circuit shown in Figure 3, the amount of dust accumulation D is calculated using the following formula. D=-(L K) -1 ·log{V / (A·Vcc)} ···(Equation 1)

[0029] In Equation 1, Vcc is the power supply voltage (the voltage between terminals 144 and 146), and V is the voltage value measured at measurement terminal 134 when Vcc is applied. K is a correction coefficient that takes into account the properties of the dust, and L and A are constants that depend on the light emission amount of the light-emitting unit (LED 130) used and the detection sensitivity of the light-detecting unit (phototransistor 132) used, respectively. As will be described later as experimental results, the variation in the estimated value can be reduced by adjusting the correction coefficient K according to the properties (e.g., color) of the dust.

[0030] (Dust accumulation amount estimation operation) The process of estimating the amount of dust accumulation in an electrical device using the dust accumulation detection device 100 of Fig. 1 will be described below with reference to Fig. 4. The process shown in Fig. 4 is performed by the control unit 108 reading and executing a predetermined program previously stored in the storage unit 110. The light emitting unit 102 and the light detecting unit 106 constitute the circuit shown in Fig. 3, and the dust accumulation detection device 100 is assumed to be placed inside (a dark place where no external light enters) the electrical device (such as a distribution board).

[0031] The storage unit 110 stores information for specifying the time to perform the measurement (hereinafter referred to as measurement time information), predetermined thresholds Th1 and Th2, parameters (L, A, Vcc) of Equation 1, and a message. The measurement time information may be any information that is specified depending on the timing of the measurement. For example, when the measurement is performed at a pre-specified time, the measurement time information may be information that directly indicates the time. When the measurement is performed at a fixed time interval, the measurement time information may be the start time and the time interval Δt. The measurement time information is preferably determined depending on the dust accumulation rate, the degree of impact of the dust on the electrical equipment, and the like. For example, the time interval Δt is a value ranging from several minutes to 24 hours. When even a small amount of dust accumulation can have a significant impact on the performance, safety, etc. of the equipment, it is preferable to set a relatively short time.

[0032] The threshold value Th1 is used to determine whether or not to perform a measurement to estimate the amount of dust. The threshold value Th2 is used to determine whether or not cleaning (cleaning, etc.) to remove the dust is necessary based on the dust amount estimation result. The message is used to notify that cleaning is necessary.

[0033] In step 400, the control unit 108 receives an input of the dust properties. Specifically, the control unit 108 receives an input of the correction coefficient K, which reflects the dust properties in Equation 1. For example, a person (such as an administrator) instructs the control unit 108 via an operation device to set a value of the correction coefficient K corresponding to the color of dust accumulated in the equipment in which the dust accumulation detection device 100 is installed. Normally, the correction coefficient K is 1, and for example, K is set as the initial value. In an environment where the reflectance of the main dust is low (blackish), the person changes the correction coefficient K to, for example, 1.3. The correction coefficient K does not need to be changed in detail; two or three types may be set. For example, if the correspondence between colors and correction coefficients is stored in the storage unit 110 in advance, the control unit 108 can present multiple candidate dust colors and identify the correction coefficient K corresponding to the color selected by the person. After the correction coefficient K is determined, control proceeds to step 402.

[0034] In step 402, control unit 108 obtains the current time from timer 112 and determines whether the measurement time has arrived by referring to the measurement time information stored in memory unit 110. If it is determined that the measurement time has arrived, control proceeds to step 404. If not, control proceeds to step 422.

[0035] In step 404, control unit 108 measures voltage V at measurement terminal 134 while light-emitting unit 102 is turned off. The measured voltage V is stored in storage unit 110 as appropriate. Step 404 is repeatedly executed, but it is sufficient that at least the last measured voltage V is stored in storage unit 110. Thereafter, control proceeds to step 406.

[0036] In step 406, the control unit 108 determines whether the voltage V measured in step 404 is equal to or less than the threshold value Th1 (V≦Th1). Steps 404 and 406 are performed to confirm that the dust accumulation detection device 100 is in a state where it can correctly perform the dust accumulation amount estimation process. When the door of the equipment (such as a distribution board) in which the dust accumulation detection device 100 is installed is opened for inspection, the optical detection system (such as the optical detection unit 106) of the dust accumulation detection device 100 is exposed to external light. If a measurement is performed in such a state, the dust accumulation amount cannot be accurately estimated. Since the terminal 146 is grounded, when no external light is input and the light-emitting unit 102 is not lit, the phototransistor 132 is off, and the voltage measured at the measurement terminal 134 is at the ground level (0 V). However, when external light is input, the phototransistor 132 turns on, causing the voltage measured at the measurement terminal 134 to increase. Th1 can be set to, for example, about 3% of the voltage at measurement terminal 134 measured when light-emitting unit 102 is turned on in a dust-free state. If V≦Th1, control proceeds to step 408. Otherwise, control proceeds to step 422.

[0037] In step 408, the control unit 108 turns on the light-emitting unit 102 and measures the voltage V at the measurement terminal 134. To turn on the light-emitting unit 102, the control unit 108 outputs a high-level signal to the power supply unit 104, causing the power supply unit 104 to supply power to the light-emitting unit 102. The measured voltage V is stored in the memory unit 110 as appropriate. Step 408 is executed repeatedly, but it is sufficient that at least the last measured voltage V is stored in the memory unit 110. Thereafter, control proceeds to step 410.

[0038] In step 410, the control unit 108 turns off the light-emitting unit 102. To turn off the light-emitting unit 102, the control unit 108 outputs a low-level signal to the power supply unit 104, causing the power supply unit 104 to stop supplying power to the light-emitting unit 102. Thereafter, control proceeds to step 412.

[0039] In step 412, the control unit 108 measures the temperature T using the temperature detection unit 114. The measured temperature T is stored in the memory unit 110 as appropriate. Note that, although step 412 is repeatedly executed, it is sufficient that at least the last measured temperature is stored in the memory unit 110.

[0040] In step 414, the control unit 108 performs temperature correction for the voltage measured in step 408. If temperature correction is not performed, when the ambient temperature of the light-emitting unit 102 and the light-detecting unit 106 increases, the detected value (voltage) of the light-detecting unit 106 also tends to increase. The amount of increase in the voltage at the measurement terminal 134 due to the ambient temperature varies depending on the degree to which the detected value of the light-detecting unit 106 decreases due to dust accumulation. Therefore, if the installation locations and environments of the light-emitting unit 102 and the light-detecting unit 106 are different, it becomes difficult to make a relative evaluation.

[0041] The amount of change in the detected value due to temperature changes (the slope of the graph) is almost constant regardless of the state of dust accumulation. Therefore, the control unit 108 corrects the voltage V measured in step 408 using the temperature measured in step 412 according to the following equation: V(25)=V(T)×(1-(T-25) / C) (Formula 2)

[0042] Here, T is the temperature measured in step 412, V(T) is the voltage at measurement terminal 134 at temperature T, i.e., the voltage measured in step 408, and V(25) is the voltage at measurement terminal 134 at T = 25 (°C). C is a constant that varies depending on the temperature characteristics of the element used (LED, phototransistor, etc.), but can usually be determined in advance as a value in the range of 50 to 500. Using Equation 2, the voltage V(T) measured in step 408 can be converted to the detected value V(25) at T = 25 (°C). The converted value is a value in which the influence of ambient temperature (temperature dependency of the element used) is suppressed. Control then proceeds to step 416.

[0043] In step 416, control unit 108 estimates the amount of dust accumulation using the above-described formula 1. Specifically, control unit 108 uses voltage V(25) at measurement terminal 134 after correction in step 414 as voltage V in formula 1, and uses the value determined in step 400 as correction coefficient K in formula 1, and calculates dust accumulation amount D using formula 1.

[0044] In step 418, control unit 108 determines whether the amount of dust accumulation has increased to the extent that cleaning of the device is necessary. Specifically, control unit 108 determines whether the amount of dust accumulation D calculated in step 416 is equal to or greater than threshold value Th2 (D≧Th2). If it is determined that D≧Th2, control proceeds to step 420. Otherwise, control proceeds to step 422. Threshold value Th2 may be set to an appropriate value depending on the device and its installation environment.

[0045] In step 420, the control unit 108 reads out a predetermined message from the storage unit 110 and displays it. For example, a message indicating that cleaning is required may be displayed. If the dust accumulation detection device 100 is equipped with an audio output device or an image display device, the message may be displayed as audio or an image. Data representing the message to be displayed may be output from the dust accumulation detection device 100 to an external audio output device or image display device.

[0046] In step 422, the control unit 108 determines whether or not an instruction to end the program has been received. If an instruction to end the program has been received, the program ends. If not, the control returns to step 402, and the above processing is repeated. The instruction to end the program is given, for example, by turning off the power to the dust accumulation detection device 100.

[0047] As described above, the voltage generated at the measurement terminal 134 varies depending on the amount of light that has passed through the dust 190 accumulated on the light reflecting member 120, as detected by the light detector 106. Therefore, the dust accumulation detection device 100 can calculate the dust accumulation amount D using Equation 1 by turning on the light emitter 102 at a predetermined timing and measuring the voltage generated at the measurement terminal 134. Although the amount of decrease in reflectance may vary depending on the characteristics (color, etc.) of the dust, even for the same accumulation amount, the dust accumulation amount D can be calculated accurately by appropriately setting the correction coefficient K according to the characteristics (color) of the dust and temperature-compensating the measured voltage at the measurement terminal 134. Since it is believed that the same amount of dust accumulates around the light reflecting member 120 inside the device, when the dust accumulation amount D becomes equal to or greater than the threshold value Th2, the dust accumulation detection device 100 displays a message recommending cleaning. By setting the threshold value Th2 appropriately, it is possible to prompt the user to remove dust by cleaning before the accumulation of dust causes a deterioration in the performance and safety of the device, thereby enabling the device to be managed appropriately.

[0048] In Equation 2, the reference temperature is set to 25°C, but this is not limiting. If the reference temperature is T1, Equation 2 becomes V(T1) = V(T) × (1-(T-T1) / C). Note that the constant C used here is a different value from the constant C in Equation 2.

[0049] By providing step 404 and step 406, it is possible to avoid performing measurements to calculate the amount of dust accumulation when the dust accumulation detection device 100 is exposed to external light. This is effective in avoiding unnecessary measurements when the dust accumulation detection device 100 is installed in a distribution board or the like. If the dust accumulation detection device 100 is in an environment where it is not affected by external light, step 404 and step 406 may be omitted.

[0050] (First Modification) In the above, the dust accumulation amount D is calculated using Equation 1 each time the voltage at measurement terminal 134 is measured, i.e., using the instantaneous voltage value. However, this is not limiting. Since step 414 is repeatedly executed, the temperature-corrected voltage values ​​may be stored in memory unit 110, and a moving average over a predetermined period may be calculated using the stored series of data (voltage values). The calculated moving average may then be used as V in Equation 1 to calculate the dust accumulation amount D. Instead of the moving average, the maximum value over a predetermined period (moving maximum value) may be used as V in Equation 1. Similar to the moving average, the moving maximum value refers to the maximum value determined by sliding a window for selecting target data from a series of ordered data (e.g., time-series data). For example, if a contaminant temporarily adheres to the optical detection system and blocks the optical path, the generated voltage (voltage at measurement terminal 134) temporarily drops, and the generated voltage returns to its normal value when the contaminant disappears. If the moving average or moving maximum value is used as V in Equation 1, the dust accumulation amount D can be calculated with high accuracy even if a temporary drop in generated voltage occurs.

[0051] (Second Modification) In parallel with the above-described estimation of the dust accumulation amount, the creepage resistance value and humidity may be measured to evaluate the insulation risk due to dust accumulation. Insulation degradation occurs when dust accumulated on an insulator absorbs moisture and forms an electrical conduction path. While dust adhesion is one factor in insulation degradation, whether or not insulation degradation actually occurs is influenced by the moisture absorption characteristics and conductivity of the dust, as well as the humidity of the environment. Therefore, by measuring the creepage resistance value and humidity in parallel with the estimation of the dust accumulation amount, it is possible to make a comprehensive risk assessment using the estimated dust accumulation amount, the creepage resistance value, and the humidity, including whether or not there is actually a tendency for insulation degradation, and the level of humidity that causes insulation degradation.

[0052] (Third Modification) In the above, a case has been described in which the light-emitting unit 102, the light-detecting unit 106, and the light-reflecting member 120 having an L-shaped cross section are arranged as shown in FIG. 2 , but the configuration and arrangement of the light-detecting system are not limited to this. For example, the light-detecting system may be configured as shown in FIG. 5. In FIG. 5, the light-emitting unit 102 is arranged above the light-detecting unit 106. The light-detecting system may also be configured as shown in FIG. 6. In FIG. 6, a flat light-reflecting member 124 is used instead of the L-shaped cross-section light-reflecting member 120. The light-emitting unit 102 and the light-detecting unit 106 are arranged on both sides of the light-reflecting member 124.

[0053] (Fourth Modification) In the above description, dust is deposited on a light-reflecting member, and light that passes through the dust 190 and is reflected by the reflector is detected by the light detector 106. However, the present invention is not limited to this. Dust may be deposited on a light-transmitting member. For example, as shown in FIG. 7, light from the light-emitting unit 102 may pass through the dust 190 and then be detected by the light detector 106. Referring to FIG. 7, the dust deposition detection device 150 has a similar configuration to the dust deposition detection device 100, except for the light detection system. That is, a flat light-transmitting member 200 is disposed between the light-emitting unit 102 and the light detector 106. Specifically, referring to FIG. 8, the light-transmitting member 200 is held at its periphery by a flat plate-shaped holding member 212, and the holding member 212 is supported on a flat portion 216 of an electrical device or the like by, for example, a plurality of columnar support members 214. The arrangement of the light-emitting unit 102 and the light detector 106 may be reversed from that shown in FIG. 8. 9, the vertical positional relationship of the light emitting unit 102 and the light detecting unit 106 with respect to the light transmitting member 200 is changed from that in FIG.

[0054] (Fifth Modification) The light detection system may have a configuration as shown in Fig. 10. After passing through a light transmitting member 230 and dust 190, light emitted from the light emitting unit 102 is reflected by a light reflecting member 232 and detected by the light detecting unit 106. Furthermore, the positions of the light emitting unit 102 and the light detecting unit 106 in Fig. 10 may be interchanged.

[0055] (Sixth Modification) Even if the same type of element (e.g., LED) is used for the light-emitting unit 102, the characteristics vary from element to element. Similarly, even if the same type of element (e.g., phototransistor) is used for the light-detecting unit 106, the characteristics vary from element to element. Therefore, even if the amount of dust accumulation is the same, the detected value will vary. It is preferable to suppress the influence of the variation (variation in characteristics) of the elements used. To this end, in the sixth modified example, referring to FIG. 11, the light-detection system circuit is composed of the light-emitting unit 118 and the light-detecting unit 106. The configuration shown in FIG. 11 is the configuration shown in FIG. 3 to which a variable resistor 300 has been added.

[0056] The variable resistor 300 is an element whose resistance value can be adjusted, such as a three-terminal potentiometer, volume, etc. One end of the variable resistor 300 is connected to resistor R1, and the other end is connected to terminal 142. As a result, if the resistance value of the variable resistor 300 changes while a constant voltage is applied to terminal 140 and terminal 142, the value of the current flowing through the LED 130 changes, and the light emission intensity of the LED 130 changes.

[0057] Therefore, for each dust accumulation detection device, for example, when no dust has accumulated on the light reflecting member 120, the variable resistor 300 is adjusted in advance so that the voltage detected from the measurement terminal 134 becomes a predetermined value when the light emitting unit 118 emits light. This makes it possible to suppress the effects of variations (variations in characteristics) of the elements used as the light emitting unit 118 and the light detecting unit 106.

[0058] To suppress the effects of element variations (variations in characteristics), it is sufficient to provide an adjustment element in at least one of the light-emitting unit and the light-detecting unit; the circuit is not limited to that shown in FIG. 11 . For example, the resistor R3 in the circuit shown in FIG. 3 may be replaced with a variable resistor. In this case, a three-terminal potentiometer may be used as the variable resistor, and its adjustment terminal (the terminal whose contact position with the resistive element changes) may be the measurement terminal 134. This allows the voltage detected by the measurement terminal 134 to be changed even if the amount of light irradiating the phototransistor 132 remains the same. Therefore, by adjusting the resistance value of the variable resistor, the effects of element-to-element variations on the detection value of the light-detecting unit (the voltage at the measurement terminal 134) regarding the LED 130 and the phototransistor 132 can be suppressed.

[0059] 11, the resistor R3 in the circuit shown in FIG. 11 may be replaced with a variable resistor as described above. By adjusting the two variable resistors, it is possible to suppress the influence of element-to-element variations in the LED 130 and the phototransistor 132 on the detection value of the light detection unit (the voltage at the measurement terminal 134).

[0060] Furthermore, the light detection circuit is not limited to the circuits shown in Figures 3 and 11 or circuits similar thereto. That is, the light detection unit is not limited to a configuration in which the phototransistor 132 and two resistors are directly connected (resistors R2 and R3 in Figure 3, and resistor R2 and variable resistor 300 in Figure 11). Any configuration is possible as long as it includes the phototransistor 132 and at least one resistor and can detect changes in the value of the current flowing through the phototransistor 132 as changes in the voltage drop across the resistor. The amount of light received by the phototransistor 132 changes depending on the amount of dust 190 accumulated, and changes in the value of the current flowing through the phototransistor 132 in response to changes in the amount of light can be detected as changes in the voltage drop.

[0061] (First embodiment) As a result of conducting a field test using the above-described dust accumulation detection device 100, in addition to voltage drops indicating long-term dust accumulation, temporary voltage drops and temporary voltage increases were observed. Therefore, as described above, judging the degree of dust accumulation and estimating the accumulation amount by comparing the measured voltage with a predetermined threshold value may result in an erroneous judgment. The first embodiment is intended to address this issue.

[0062] 15, a dust accumulation detecting device 170 according to the first embodiment of the present invention has the same configuration as the dust accumulation detecting device 100 shown in FIG. 1. The dust accumulation detecting device 170 differs from the dust accumulation detecting device 100 only in that it includes a humidity detecting unit 116. The structural configuration of the optical detection system of the dust accumulation detecting device 170 is the same as that shown in FIG. 2, and the circuit configuration thereof is the same as that shown in FIG. 3. Therefore, in the following, reference will also be made to the reference numerals in FIGS. 2 and 3 as appropriate.

[0063] The humidity detection unit 116 detects the humidity of the environment in which the light detection system (light emitting unit 102, light detecting unit 106, and light reflecting member 120) of the dust accumulation detection device 170 is placed. The humidity detection unit 116 is, for example, a humidity sensor. The detected value (humidity) of the humidity detection unit 116 is input to the control unit 108. The control unit 108 stores the input detected value in the memory unit 110.

[0064] Similar to the dust accumulation detection device 100, the dust accumulation detection device 170 measures the voltage at the measurement terminal 134 at predetermined timing, corrects the measured value for temperature, and then compares it with a predetermined threshold value Th3 to determine the level of dust accumulation. Similar to the dust accumulation detection device 100, the dust accumulation detection device 170 may estimate the amount of dust accumulation and compare the result with the threshold value Th2 to determine whether cleaning is required. Unlike the dust accumulation detection device 100, the dust accumulation detection device 170 measures humidity using the humidity detection unit 116 when measuring the voltage at the measurement terminal 134. The dust accumulation detection device 170 (control unit 108) stores the measured humidity and the voltage value at the measurement terminal 134 in chronological order in the memory unit 110.

[0065] Dust accumulation detection device 170 does not determine the accumulation of dust using a single measurement value, but rather stores the measurement values ​​(voltage and humidity) over a predetermined period as time-series data in storage unit 110, and determines the level of dust accumulation using the data after eliminating temporary fluctuations in the measurement values. Specifically, temporary changes in the measurement values ​​are eliminated by the following (1) to (3). In the following, humidity means relative humidity (%RH).

[0066] (1) As will be described later, a phenomenon in which the voltage at the measurement terminal 134 temporarily drops when measured under high humidity conditions has been observed. To address this temporary voltage drop, dust accumulation is determined using time-series data of voltage and humidity measured at the same time, excluding voltage measurements taken under high humidity conditions (e.g., 70% RH or higher). If a voltage drop (e.g., a state in which the measured voltage is below threshold value Th3) continues for a certain period of time (e.g., one day), dust accumulation is determined. If dust accumulation is determined, for example, a message indicating that cleaning is necessary is displayed. Note that the same time does not necessarily mean the same time, and there may be a time difference within a range in which the measurement target (voltage and humidity) is considered to be constant.

[0067] (2) In order to deal with temporary voltage increases, voltage measurements are made at the measurement terminal 134 almost simultaneously when the light-emitting unit 102 is on and when it is off. If the voltage when the light-emitting unit 102 is off is equal to or greater than a certain value, the corresponding measured voltage (the voltage when the light-emitting unit 102 is on) is excluded. For example, by not storing this in the memory unit 110, it is prevented from being included in the time-series data (voltage) used to determine dust accumulation. Using the obtained time-series data (voltage), it is determined that dust accumulation has occurred if a voltage drop continues for a certain period of time, as in (1).

[0068] (3) To deal with both temporary voltage drops and voltage increases, dust accumulation is determined using the moving median of time-series data (voltage) for a certain period in the past (for example, two days). The median is the value located in the middle when time-series data for a certain period are sorted in ascending order of magnitude, and the moving median is the median determined by sliding a window to select target data for an ordered series of data (such as time-series data). If the total number of target data is odd, a single median is determined. If the total number of target data is even, the arithmetic mean of the two middle values ​​is used as the median.

[0069] By implementing any one of (1) to (3) or a combination of them, it is possible to eliminate from the measured voltage values ​​the measurement values ​​(abnormal values) that occur during temporary voltage drops and voltage increases. By using the data obtained after excluding the abnormal values, it is possible to more accurately determine whether or not dust has accumulated. By estimating the amount of dust accumulation using the data obtained after excluding the abnormal values, it is possible to obtain a more accurate estimate.

[0070] The processes (1) to (3) above can be realized, for example, by the process shown in Fig. 16. The flowchart shown in Fig. 16 is obtained by adding steps 500 to 508 to the flowchart in Fig. 4 and replacing steps 416 and 418 with step 510. In Fig. 16, steps having the same reference numerals as in Fig. 4 are the same as those in Fig. 4, and therefore will not be described repeatedly. The process shown in Fig. 16 is performed by control unit 108 shown in Fig. 15 reading out and executing a predetermined program stored in advance in storage unit 110.

[0071] In step 500, the control unit 108 measures the humidity by the humidity detection unit 116 while the light emitting unit 102 remains turned off. In step 502, the control unit 108 determines whether the current environment is of high humidity. Specifically, the control unit 108 determines whether the humidity measured in step 500 is equal to or higher than a predetermined value (for example, 70%RH). If it is determined that the humidity is not high (humidity < 70%RH), the control proceeds to step 504. Otherwise (if the humidity is high), the control proceeds to step 422. As a result, as shown in (1) above, the voltage value measured in the high humidity state (the measured voltage value in step 408) is discarded without being stored in the storage unit 110.

[0072] In step 504, the control unit 108 determines whether the voltage measured in step 404 (the light emitting unit 102 is in the off state) is equal to or higher than the threshold value Th3. If it is determined that the voltage ≥ Th3, the control proceeds to step 422. Otherwise (if the voltage < Th3), the control proceeds to step 412. As a result, as shown in (2) above, the measured voltage value in step 408 is discarded without being stored in the storage unit 110 as an abnormally increased value.

[0073] In steps 412 to 414, the voltage value measured in step 408 is temperature - corrected. Subsequently, in step 506, the control unit 108 stores the temperature - corrected voltage value in the storage unit 110 as time - series data.

[0074] In step 508, the control unit 108 determines whether or not to determine the presence or absence of dust accumulation. If a predetermined time or a predetermined time interval is set in advance, the control unit 108 can obtain the current time from the timer 112 and determine whether or not it is time to determine the presence or absence of dust accumulation, similar to step 402. If it is determined that it is time to determine the presence or absence of dust accumulation, the control proceeds to step 510. Otherwise, the control proceeds to step 422. As a result, time-series data that does not include either a measurement value at high humidity or an abnormally high measurement value among the voltages of the measurement terminal 134 measured when the light-emitting unit 102 is turned on is stored in the storage unit 110.

[0075] In step 510, the control unit 108 reads out the time-series data (which does not include either measurements at high humidity or abnormally high measurements) stored in the storage unit 110 and determines whether or not there is a dust volume. Specifically, the control unit 108 determines whether or not the most recent measurement value is equal to or less than a predetermined threshold value Th4. If it is equal to or less than Th4, it determines that dust has accumulated. If it is determined that dust has accumulated, in step 420, a message indicating that cleaning is necessary is displayed. If it is not determined that dust has accumulated, control proceeds to step 422.

[0076] In step 510, as described in (3) above, the median value for a certain period of time in the past (for example, two days) may be identified, and it may be determined whether or not the median value is equal to or less than a predetermined threshold value Th4. In this case, since measurements (abnormal values) during temporary voltage drops and voltage increases can be excluded, steps 500 to 504 may be omitted.

[0077] Alternatively, instead of or in addition to step 510, the dust accumulation amount may be estimated as in the related embodiments of the invention, and the estimated value may be used to determine whether cleaning is required. In this case, the dust accumulation amount can be estimated more accurately using data that excludes measurements (abnormal values) during temporary voltage drops and voltage increases.

[0078] (Second embodiment) Condensation is known to be a phenomenon that can cause insulation deterioration in electrical equipment. The second embodiment is intended to address this issue. Referring to FIG. 22, a condensation risk detection device 180 according to the second embodiment is the same as the dust accumulation detection device 100 (see FIG. 1) according to the embodiment of the related invention. The structural configuration of the optical detection system of the condensation risk detection device 180 is the same as that shown in FIG. 2, and the circuit configuration is the same as that shown in FIG. 3. Therefore, in the following, reference will also be made to the symbols in FIGS. 2 and 3 as appropriate.

[0079] Condensation risk detection device 180 measures the voltage at measurement terminal 134 at a predetermined timing, corrects the value for temperature, estimates the amount of dust accumulation, and compares the result with threshold value Th2 to determine whether cleaning is necessary. Condensation risk detection device 180 may also measure the voltage at measurement terminal 134, corrects the value for temperature, and compares it with predetermined threshold value Th3 to determine whether dust accumulation exists.

[0080] Typically, to address condensation, risk avoidance is achieved by monitoring relative humidity and environmental improvement measures (such as dehumidifiers and space heaters) are implemented. Field testing using the condensation risk detection device 180 revealed that even at roughly the same relative humidity, differences in the amount of air circulated to electrical equipment can make condensation more likely or less likely. Specifically, in voltage measurements at the measurement terminal 134, in addition to voltage drops indicating long-term dust accumulation, temporary voltage drops due to condensation on the reflector when the relative humidity rose were confirmed. Because condensation can lead to insulation degradation of insulators, it would be desirable to be able to evaluate this voltage drop as an insulation risk.

[0081] In the field tests, two types of distribution boards were installed with identical condensation risk detection devices in nearly identical locations (nearly identical environments). One of the distribution boards was forcedly ventilated, while the other was not. These distribution boards are referred to as the forced-ventilation distribution board and the non-forced-ventilation distribution board. As a result, the forced-ventilation distribution board was observed to have a higher frequency of voltage drops. In other words, while condensation risk is generally assessed based on relative humidity, it was confirmed that the likelihood of condensation varies depending on the degree of introduction of outside air into the distribution board, even in environments with similar relative humidity. Furthermore, it was confirmed that voltage drops occur before significant insulation degradation along the insulation surface becomes apparent.

[0082] Based on the above findings, a method for evaluating the risk of condensation using the voltage value of measurement terminal 134 measured by condensation risk detection device 180 will be described. Condensation risk detection device 180 does not evaluate the risk of condensation using a single measurement value, but rather stores measurements (voltage and humidity) over a predetermined period as time-series data in storage unit 110 and evaluates the risk of condensation by sequentially executing the following first to third processes. The measured time-series data is data (hereinafter also referred to as trend data) that represents the tendency of the degree of dust accumulation (dust accumulation amount).

[0083] First process: From the measured trend data (hereafter referred to as trend data A), trend data (hereafter referred to as trend data B) that shows the long-term trend of the progress of dust accumulation is generated. Specifically, the moving median of the time-series data (voltage) for a certain period in the past (for example, two days) is calculated. In trend data B, measurements during temporary voltage drops and voltage increases (abnormal values) are excluded from the voltage measurements.

[0084] Second process: Trend data A at measurement time t i (i is the number assigned in the order of measurement) is expressed as A(t i ), trend data B measured at time t i The measured value of B(t i ) as the value A(t i) and B(t i ) of the ratio R(A(t i ) / B(t i )) is calculated for all measurement times t i . Note that since the trend data B is a series of moving medians, the number of data points is smaller than that of the trend data A. Therefore, all measurement times t i means all the measurement times t i at which B(t i ) is obtained. Since the ratio R represents the ratio of the trend data A including the measured values (abnormal values) during temporary voltage drops and rises to the trend data B excluding the measured values (abnormal values) during temporary voltage drops and rises, it becomes a value significantly different from the values at other times during temporary voltage drops and rises. Among them, during a temporary voltage drop, the ratio R becomes a small value.

[0085] Third process: Determine the frequency at which the ratio R is less than or equal to the threshold Th5 (R ≤ Th5), and evaluate the dew condensation risk according to the obtained frequency. The threshold Th5 is, for example, 0.9. If the frequency of repeated dew condensation and drying is high, the risk of insulation degradation due to fouling and the occurrence of microdischarges is high, and tracking degradation is likely to occur. Therefore, as an index of the dew condensation risk (an index leading to tracking degradation due to fouling), the ratio (frequency) H (%) of the time during which a voltage drop occurs to the total voltage measurement time is used. If the frequency H ≤ 0.01 (%), it is considered that the number of dew condensation occurrences in a year is 2 to 3 times or less, and the dew condensation risk is judged to be low. Note that the number of dew condensation occurrences means the number of times of continuous dew condensation, not the number of times of R ≤ Th5. Usually, a voltage drop due to dew condensation continues for several hours. Therefore, even if R ≤ Th5 occurs multiple times in a state of continuous dew condensation, they are counted as one time. If the frequency H ≥ 0.1 (%), it is considered that the number of dew condensation occurrences in a year is 10 times or more, and the dew condensation risk is judged to be high.

[0086] Considering the range of 0.01 < H < 0.1, for example, the evaluation criteria can be set as shown in Table 1 below.

[0087]

Table 1

[0088] The evaluation result of the risk of condensation can determine whether or not a dehumidifier is required. If the risk of condensation is determined to be low, it can be determined that there is little possibility of tracking degradation due to condensation occurring, and that there is no need to install a dehumidifier or the like. On the other hand, if the risk of condensation is determined to be high, it can be determined that there is a need to install a dehumidifier or the like. After installing a dehumidifier or the like, the voltage is measured as described above, and the first to third processes are performed on the measurement data, thereby determining whether or not the installed dehumidifier or the like is working effectively.

[0089] The threshold value Th5 is not limited to 0.9, and may be set to a value between 0.8 and 0.95, for example. [Example]

[0090] The following are experimental results relating to embodiments of the related invention. Measurements were conducted using three photodetectors employing the photodetection system with the circuit configuration shown in Figure 11, and simulated dust. The reflector (light-reflecting member) was made of BA stainless steel SUS304 (with a surface finish that is nearly mirror-like), and the light-emitting element was an LED emitting red light (center frequency 630 nm). The same test was conducted three times (a total of nine times) using each of the three photodetectors in a room with an ambient temperature of approximately 20°C. Kanto loam No. 8, a standard powder, was used as the simulated dust to be deposited.

[0091] Before carrying out the measurements, as shown in the sixth modified example, adjustments were made to suppress the effects of variations (variations in characteristics) in the light-emitting units 102 and light-detecting units 106 used in the three photodetectors. Specifically, the variable resistors 300 (see FIG. 11 ) of each of the three photodetectors were adjusted so that the voltage values ​​at the measurement terminals 134 of the light-detecting units in a dust-free state (new condition) were the same for all three photodetectors.

[0092] The experimental results are shown in Figure 12. In Figure 12, the horizontal axis represents the amount of dust (Kanto Loam Layer No. 8) deposited (mg / cm 2 ), and the vertical axis represents the relative value of the voltage (generated voltage) measured at the measurement terminal 134. The measurement values ​​for each combination of photodetector and number of measurements are represented by different figures. Information about the plotted figures (measured values) is shown at the top of Figure 12. In the notation "photodetector Ni_j," Ni (i = 1 to 3) represents each of the three photodetectors, and j (j = 1 to 3) represents the number of measurements.

[0093] The measurement results plotted in Fig. 12 show that, although there is some variability in the measurements because the amount of light reaching the light detection unit decreases as the amount of dust accumulation on the reflector increases, it was confirmed that there is a correlation between the amount of dust accumulation and the voltage (generated voltage) generated at measurement terminal 134 by light reaching the light detection unit. The curve shown in Fig. 12 was obtained by fitting the amount of dust accumulation to a logarithmic function curve (∝logV) of the generated voltage V for all of the measurement results plotted in Fig. 12, and determining parameters so that the difference between the values ​​on this curve and each measured value is minimized. Specifically, the parameters L, A, and Vcc were determined using the following equations. D=-(L) -1 ·log{V / (A·Vcc)} ···(Equation 3) Equation 3 is obtained by setting the correction coefficient K to 1 in Equation 1 above. The curve shown in Fig. 12 reproduces the correlation between the amount of dust accumulation and the generated voltage, and it can be seen that the amount of dust accumulation can be estimated using Equation 3. [Example]

[0094] The experiment was conducted using the same three photodetectors as in the above experiment, but using powders with different properties as simulated dust. In the same test environment as the above experiment, the light intensity was adjusted in the same way as in the above experiment, and the generated voltage was measured. Food coloring (red, green, and dark brown) was used as simulated dust. Using each of the three photodetectors, one test was conducted for each of the three types of powder (a total of nine tests were conducted).

[0095] The experimental results are shown in Figures 13 and 14. In Figures 13 and 14, the horizontal axis represents the amount of dust accumulation (mg / cm2 ), and the vertical axis represents the relative value of the voltage (generated voltage) measured at the measurement terminal 134. Information about the plotted figure (measured value) is shown above each figure. In the label "Photodetector Ni_j," Ni (i = 1 to 3) represents each of the three photodetectors, and j (j = red, green, dark brown) represents the simulated dust. For reference, the average value for each deposition amount was calculated for the measurement results shown in Figure 12 and plotted as "Kanto Loam Layer No. 8."

[0096] It was confirmed from Figure 13 that when red pigment was deposited, the reflectance was equivalent to that of Kanto Loam Layer No. 8. This means that for red dust, the amount of deposition can be estimated using Equation 3 above, whose parameters were determined from the experimental results above. The curve shown in Figure 13 is the same as the curve in Figure 12, and it can be seen that the correlation between the amount of dust deposition and the generated voltage has been reproduced.

[0097] The measured values ​​(generated voltage) for the green and dark brown pigments shown in Figure 14 are smaller than the measured values ​​for the red pigment shown in Figure 13, which were measured under the same deposition conditions. That is, the red pigment has a relatively high reflectance (hereinafter referred to as "high reflectance"), while the green and dark brown pigments have a relatively low reflectance (hereinafter referred to as "low reflectance"). Figure 14 shows that the reflectance when the green pigment is deposited is comparable to the reflectance when the dark brown pigment is deposited. Furthermore, the correlation between the deposition amount of the green pigment and the dark brown pigment and the generated voltage is expected to be similar to the correlation between the deposition amount of the red pigment and the Kanto Loam Layer No. 8 and the generated voltage. However, the reflectance is generally lower than that of the Kanto Loam Layer No. 8. Therefore, even if the deposition amount of low-reflectance green or dark brown dust is estimated using the above Equation 3, whose parameters are determined based on the above experimental results, the accuracy is insufficient (large error occurs).

[0098] As described above, dust can be classified into two groups: those with high reflectivity to the light source (red pigment, Kanto loam layer No. 8) and those with low reflectivity (green pigment, dark brown pigment), and the reflectivity of each group is considered to be equivalent. For the high-reflectivity group, the dust accumulation amount can be estimated using Equation 3. For the low-reflectivity dust, the dust accumulation amount can be estimated by correcting Equation 3. Therefore, for example, by introducing a correction coefficient K and using Equation 1 described above, the dust accumulation amount can be estimated for both the high-reflectivity and low-reflectivity groups. For example, the measurement results shown in Figures 12 to 14 confirmed that when the parameters of Equation 1 for the high-reflectivity group dust are determined as K = 1, the dust accumulation amount for the low-reflectivity group can be estimated using Equation 1 with the same parameters and K = 1.3. The correction coefficient K varies depending on the properties of the dust, and should generally be set within the range of 0.5≦K≦3.

[0099] In the experiments shown in Examples 1 and 2, stainless steel SUS304 was used for the reflector. By using stainless steel, the gloss (i.e., reflectance) of the reflector can be maintained in good condition for a long period of time. Furthermore, the surface finish is not limited to BA, and electrolytic polishing may also be used. This makes it possible to ensure good reflectance at low cost. Furthermore, as described above, by using a light-emitting unit (LED) that emits red light, the stainless steel reflector has good reflectance and also has good response to the decrease in reflectance due to dust accumulation, allowing the decrease in reflectance due to dust accumulation to be quickly detected. These light-reflecting members and light-emitting units are easily available. [Example]

[0100] The following describes experimental results for the first embodiment, demonstrating the effectiveness of the present invention. The dust accumulation detection device 170 shown in Fig. 15 was installed in a distribution board, and the experiment was conducted from November 7, 2018 to August 7, 2019.

[0101] Every 10 minutes, the light-emitting unit 102 was turned on and the voltage at the measurement terminal 134 was measured. The results are shown in Figure 17. The vertical axis of Figure 17(a) is the measured voltage, and the graph in (a) shows the long-term trend of the measured voltage. The vertical axis of Figure 17(b) is humidity, and the graph in (b) shows the humidity trend. The horizontal axis of Figures 17(a) and (b) is time (month and day).

[0102] From the graph in Figure 17(a), we can see that the measured voltage has a long-term downward trend. By observing the dust accumulation in the equipment under test, we confirmed that this long-term downward trend is due to dust accumulation.

[0103] In the graph (a) of Figure 17, in addition to the long-term trend, sudden voltage changes (temporary voltage drops and voltage increases) can be seen. By observing the measurements (a) and (b) taken at the same time, it was confirmed that the timing of the temporary voltage drops and the timing of high humidity (80% RH or higher) almost coincided. The temporary voltage drops are thought to be caused by condensation on the light-reflecting member 120, which caused the light-reflecting member 120 to become cloudy and its reflectance to decrease. The duration of the temporary voltage drops was approximately 5 hours or less, which was confirmed to almost coincide with the duration of the high humidity.

[0104] In order to eliminate temporary voltage drops, data measured when the humidity was 70% RH or higher was excluded from the time-series voltage measurement data shown in Figure 17(a). Hereinafter, this process will be referred to as Calculation 1. The results of Calculation 1 are shown in Figure 18. As can be seen from Figure 18, data on temporary voltage drops has been largely removed from the time-series voltage measurement data. However, temporary voltage drops can be seen in some areas in Figure 18. This is thought to be due to causes other than high humidity, such as floating dust particles temporarily entering the optical path.

[0105] To eliminate temporary voltage increases, the voltage at measurement terminal 134 was measured when light-emitting unit 102 was off and there was no dust accumulation, and data that was 3% or more higher than the measured voltage value was removed from the time-series voltage measurement data shown in FIG. 17(a). This process will be referred to as Calculation 2 hereinafter. The results of Calculation 2 are shown in FIG. 19. It can be seen from FIG. 19 that data on temporary voltage increases has been removed from the time-series voltage measurement data.

[0106] It has been confirmed that temporary voltage drops and voltage increases can be eliminated by the above-described Calculation 1 and Calculation 2. However, performing Calculation 1 and Calculation 2 requires measuring humidity and measuring the voltage at measurement terminal 134 with light-emitting unit 102 turned off, which increases the number of measurement items and complicates the processing.

[0107] From detailed observation of the trend data, we learned that temporary voltage drops caused by high humidity last for about several hours. Based on this knowledge, we calculated the moving maximum value of the data over one day using the data after performing Calculation 2 on the time-series voltage measurement data shown in Figure 17(a). This process will be referred to as Calculation 3 hereafter. The results of Calculation 3 are shown in Figure 20. From Figure 20, we can see that Calculation 3 eliminates the effects of temporary voltage drops and voltage increases from the time-series voltage measurement data, and obtains a graph that shows the long-term trend of voltage drops, indicating the progression of dust accumulation. Calculation 3 also eliminates the need to measure humidity.

[0108] A moving median of the data over two days was calculated for the time-series voltage measurement data shown in (a) of FIG. 17. Hereinafter, this process will be referred to as Calculation 4. The results of Calculation 4 are shown in FIG. 21. From FIG. 21, it can be seen that Calculation 4 eliminates the effects of temporary voltage drops and voltage increases from the time-series voltage measurement data, and a graph can be obtained that shows the long-term trend of voltage drops, indicating the progression of dust accumulation. Calculation 4 eliminates the need to measure humidity or the voltage at measurement terminal 134 with light-emitting unit 102 turned off.

[0109] By calculating the moving maximum or the moving median, there is a delay of about 1 to 2 days from the first measurement to the first evaluation of dust deposition. However, since dust deposition progresses over a long period of time, there is no problem. After the first evaluation of dust deposition, each time the next measurement is made, it becomes possible to evaluate dust deposition.

[0110] In the above, in calculation 3, the case of obtaining the moving maximum of data for one day and in calculation 4, the case of calculating the moving median of data for two days has been described, but it is not limited to this. The window for selecting the target data for obtaining the moving maximum from the time-series data may be 0.5 days or more and 5 days or less. The window for selecting the target data for obtaining the moving median from the time-series data may be 1 day or more and 10 days or less.

[0111] In the above, the case of using the moving maximum or the moving median for the detection of dust deposition has been described, but it is not limited to this. Any value that can be obtained by moving and removing temporary voltage fluctuations from the measured values of the time-series voltage may be used. For example, instead of the moving maximum, the measured value of the nth (n is any integer value from 2 to 10) size when the target data is arranged in descending order may be used to detect the presence or absence of dust deposition. Also, instead of the moving maximum, the average value of the measured values of the nth to mth (n is any integer value from 2 to 10, m is any integer value from 3 to 15, and n < m) size when the target data is arranged in descending order may be used to detect the presence or absence of dust deposition.

[0112] Similarly, instead of the moving median, the measured values near the median may be used to detect the presence or absence of dust deposition. The measured values near the median are, for example, the measured values that are larger or smaller than the median by the nth (taking the 0th as the median, n is any integer value from 1 to 10) when the time-series data for a predetermined period is arranged in ascending order of size. Also, instead of the moving median, the average value of a plurality of measured values near the median may be used to detect the presence or absence of dust deposition. The plurality of measured values near the median are, for example, n measured values (n is any integer value from 2 to 10) including the median and the measured values near the median when the time-series data for a predetermined period is arranged in ascending order of size. [Example]

[0113] The following shows the experimental results of the second embodiment, demonstrating the effectiveness of the present invention. The condensation risk detection device 180 shown in Fig. 22 was installed on a forced ventilation switchboard and a non-forced ventilation switchboard, and the experiment was conducted from November 7, 2018 to August 7, 2019.

[0114] The light-emitting unit 102 was turned on and the voltage at the measurement terminal 134 was measured every 10 minutes. The results are shown in FIG. 23. In both (a) and (b) of FIG. 23, the vertical axis represents the measured voltage, and the horizontal axis represents time (month and day). Graph (a) of FIG. 23 shows the long-term trend of the measured voltage in a forced-ventilation distribution panel. Graph (b) of FIG. 23 shows the long-term trend of the measured voltage in a non-forced-ventilation distribution panel. Graphs (a) and (b) of FIG. 23 show a long-term trend of voltage drop, as well as temporary voltage drops and voltage increases. The long-term trend of voltage drop is caused by the progression of dust accumulation. The temporary voltage drop is caused by condensation on the light-reflecting member 120. The temporary voltage increase is caused by external light entering the panel when the door is opened during maintenance, etc.

[0115] As a first process, the moving median of the two-day data was calculated for each of the time-series voltage measurement data shown in (a) and (b) of Figure 23. The results are shown in Figure 24. The graphs in (a) and (b) of Figure 24 are the results of processing (a) and (b) of Figure 23, respectively. As can be seen from Figure 24, the effects of temporary voltage drops and voltage increases were eliminated from the time-series voltage measurement data, and a graph was obtained that shows the long-term trend of voltage drops, which indicates the progression of dust accumulation.

[0116] Using the time-series data shown in FIGS. 23(a) and 23(b) and the time-series data shown in FIGS. 24(a) and 24(b), the ratio R was calculated as described above in the second process. The results are shown in FIG. 25. The vertical axis of FIG. 25 represents the ratio R. The graph in FIG. 25(a) shows the results using FIGS. 23(a) and 24(a), while the graph in FIG. 25(b) shows the results using FIGS. 23(b) and 24(b). The graph in FIG. 25 shows the temporary voltage increases and decreases (short-term voltage fluctuations) seen in FIG. 23, but does not show the long-term voltage decrease associated with dust accumulation. Therefore, it can be seen that the second process can remove the long-term voltage decrease trend from the time-series voltage measurement data obtained by measuring the voltage at the measurement terminal 134, and derive the short-term voltage fluctuation trend.

[0117] For each of the time-series data shown in Figure 25(a) and (b), the frequency of temporary voltage drops was determined as described above in the third process. Specifically, to detect a temporary voltage drop of 90% or less, the threshold value Th5 was set to 0.9, and if R<0.9, F=1, and if R≥0.9, F=0. The results are shown in Figure 26. The vertical axis in Figure 26 represents F. Figure 26(a) shows the results using Figure 25(a), and Figure 26(b) shows the results using Figure 25(b).

[0118] Figure 26(a) shows that the forced-ventilation panel experienced approximately 20 voltage drops. Figure 26(b) shows that the non-forced-ventilation panel experienced only one voltage drop (on February 4th). Taking into account the duration of each voltage drop, the total time during which voltage drops occurred was calculated to be 1,950 minutes for the forced-ventilation panel, with a frequency H calculated according to the third process described above of approximately 0.5%. Meanwhile, the total time during which voltage drops occurred for the non-forced-ventilation panel was 20 minutes, with a frequency H of approximately 0.005%. This suggests that the forced-ventilation panel is at higher risk of condensation and is more likely to experience repeated condensation and drying of the insulating surface, increasing the risk of insulation degradation due to contamination and microdischarges, leading to tracking degradation. [Example]

[0119] Experiments were conducted to gain insight into insulation degradation, microdischarge occurrence, and tracking degradation due to contamination. Specifically, an ultrasonic humidifier was used to increase the humidity in the environment (distribution board) where the condensation risk detection device 180 was installed, satisfying the condensation conditions, and the humidity, voltage at the measurement terminal 134 of the condensation risk detection device 180, and creepage sheet resistance were measured. A humidity sensor with a maximum measured humidity of 95% RH was used for the humidity detection unit 116. The results are shown in Figure 27. In Figure 27, (a) represents the change in relative humidity, (b) represents the change in generated voltage (voltage at the measurement terminal 134), and (c) represents the change in creepage sheet resistance. The horizontal axis represents the same time axis for all plots. The creepage sheet resistance was measured by applying a voltage to a simulated electrode installed inside the distribution board.

[0120] In Figure 27(a), the humidifier was turned on at measurement start time t1, and humidification began. At time t4, the clear condensation conditions were met. At time t5, the humidifier was stopped. Figures 27(a) and 27(c) show that the creepage sheet resistance began to decrease at time t4, when the relative humidity met the clear condensation conditions. Therefore, measuring the creepage sheet resistance cannot predict the risk of condensation before it occurs.

[0121] 27(a) and (b), it can be seen that the voltage drop began at time t2, before time t4, when the relative humidity clearly meets the condensation condition. Furthermore, the generated voltage dropped to 0.9 at time t3, a little before time t4, when the relative humidity clearly meets the condensation condition. Therefore, the condensation risk detection device 180 (see FIG. 15) can detect the risk of condensation before condensation clearly occurs, allowing the state to be grasped in a fail-safe manner and countermeasures to be implemented.

[0122] Although the present invention has been described above by explaining the embodiments, the above-described embodiments are merely examples, and the present invention is not limited to the above-described embodiments. The scope of the present invention is defined by the claims in the appended claims, taking into consideration the detailed description of the invention, and includes all modifications within the meaning and scope equivalent to the wordings described therein. [Explanation of symbols]

[0123] 100, 150, 170 Dust accumulation detection device 102, 118 Light-emitting part 104 Power supply section 106 Light detection unit 108 Control Unit 110 Storage section 112 Timer 114 Temperature detection unit 116 Humidity detection unit 120, 124, 232 Light reflecting member 122, 212 holding member 130 LED 132 Phototransistor 134 Measurement terminal 140, 142, 144, 146 terminals 180 Condensation risk detection device 190 Dust 200, 230 Light-transmitting member 214 Support member 216 Flat area 300 variable resistor R1, R2, R3 resistance

Claims

[Claim 1] a light emitting means for irradiating a predetermined portion of the electrical device with light; a light detection means for detecting light transmitted through the predetermined portion or light reflected by the predetermined portion; a measurement terminal that generates a voltage corresponding to the current flowing through the light detection means when the light emitting means irradiates the predetermined portion with light; a measuring means for measuring the voltage of the measuring terminal; a first calculation means for generating second time series data of a moving median from first time series data acquired by the measurement means by repeating measurement of the voltage over a predetermined period of time; second calculation means for dividing the first time series data by the second time series data to generate third time series data; evaluation means for evaluating a risk of condensation on the predetermined portion of the electrical device; The evaluation means calculating a frequency at which the voltage measured by the measuring means drops by comparing the third time-series data with a predetermined threshold value; A condensation risk detection device, characterized in that the condensation risk is evaluated according to the frequency.

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