Watthour meter

Abstract

To enable detection of a temperature rise to be predicted to cause a damage of an instrument at an optimal position, and easy optimization of a temperature abnormality determination threshold value when detecting the temperature rise.SOLUTION: A watthour meter includes: a terminal part 31 having a power supply terminal 32 and a load terminal 33; a current circuit 30 having a 1-side switch 38 and a 3-side switch 39 and provided between the power supply terminal 32 and the load terminal 33; a 1-side temperature detectors (A)43A, (B)43B and a 3-side temperature detectors (A)44A, (B)44B that measure terminal temperatures of the power supply terminal 32 and the load terminal 33, respectively: a thermistor 27 that measures an ambient outside air temperature; and a determination circuit 55 that, when at least one of absolute values of the terminal temperatures is equal to or more than a determination value, opens the 1 / 3-side switches 38, 39, and when at least one of temperature differences between the terminal temperatures and the outside air temperature is equal to or more than an abnormality determination threshold value, determines that abnormal heat generation is caused by fastening failure of the terminal part 31.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a watt-hour meter having a temperature abnormality monitoring function. [Background technology]

[0002] In recent years, electronic electricity meters (also called smart meters SM) have become widespread as instruments for measuring the amount of electricity used in ordinary households and other places.

[0003] This type of electricity meter has a terminal portion to which the power supply side distribution line and the load side distribution line are connected, a conductive portion (current circuit) that conducts power between the power supply side terminal to which the power supply side distribution line of the terminal portion is connected and the load side terminal to which the load side distribution line is connected, and various internal circuits.

[0004] In other words, the electricity meter is configured so that the distribution line on the power source side is fastened to the power source side terminal of the terminal portion, and the distribution line on the load side is fastened to the load side terminal of the terminal portion by means of screws or the like, thereby electrically connecting each distribution line to the conductive portion.

[0005] In conventional electricity meters, abnormal heat generation could occur due to improper tightening of the distribution lines fastened by screws or deterioration of the contact resistance of the conductive switch, which could damage the plastic outer casing, etc.

[0006] To solve these problems, a watthour meter has been proposed that is capable of detecting temperature increases in conductive parts and terminals that are predicted to lead to damage to the watthour meter (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2010-19680 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, with conventional electricity meters, it was difficult to detect temperature increases that were predicted to lead to damage to the meter at the optimal position, and it was not easy to optimize the temperature abnormality determination threshold when detecting a temperature increase.

[0009] In other words, because there are many locations where abnormal heat is generated, it was necessary to install a temperature sensor at each location where abnormal heat is generated. In addition, there are various possible factors that can cause temperature increases, such as variations in the characteristics of each meter and changes in environmental temperature (outside air temperature). For this reason, it is difficult to set a standard setting value (temperature abnormality judgment threshold) to accurately detect abnormal heat generation at each location. In particular, in order to isolate the influence of the outside air temperature, it is necessary to devise a way to measure the outside air temperature without compromising the weather resistance of the watt-hour meter.

[0010] In view of the above-mentioned problems, the present invention aims to provide an electricity meter that can detect temperature increases that are predicted to lead to damage to the meter at an optimal position, and that can easily optimize the temperature abnormality judgment threshold when detecting a temperature increase. [Means for solving the problem]

[0011] In order to solve the above problem, claim 1 of the present invention is characterized in comprising a terminal unit having a power terminal to which a power distribution line on a power source side is fastened and a load terminal to which a power distribution line on a load side is fastened, a conductive part having a switch and provided between the power terminal and the load terminal of the terminal part, an internal temperature measurement means for measuring terminal temperatures of the power terminal and the load terminal of the terminal part at respective measurement points, an outside air temperature measurement means for measuring the outside air temperature around an outer casing in which the conductive part and the terminal part are provided, and a judgment unit for opening the switch of the conductive part as a temperature abnormality when at least any of the absolute values ​​of each terminal temperature measured at each measurement point by the internal temperature measurement means is equal to or greater than a predetermined judgment value, and for calculating a temperature difference between each terminal temperature and the outside air temperature when the absolute value of each terminal temperature is less than the judgment value, and for determining that the cause of the abnormal heat generation is poor fastening at the measurement point where the terminal temperature was measured when at least any of the calculated temperature differences is equal to or greater than a predetermined abnormality judgment threshold value.

[0012] The invention of claim 2 is characterized in that the internal temperature measuring means determines the measurement location and the temperature abnormality determination threshold value based on actual measurement data and thermal analysis data obtained by a thermal analysis simulation.

[0013] The invention of claim 3 is characterized in that the judgment unit notifies an abnormal state to the outside via a notification means when at least any of the absolute values ​​of the terminal temperatures is equal to or greater than the judgment value, and when at least any of the temperature differences is equal to or greater than the abnormality judgment threshold.

[0014] The invention of claim 4 is characterized in that, when the absolute value of each terminal temperature is less than the judgment value and at least any of the temperature differences is equal to or greater than the abnormality judgment threshold, if the temperature difference equal to or greater than the abnormality judgment threshold is within a predetermined value above the abnormality judgment threshold, the judgment unit judges that the cause of the abnormal heating is poor contact of the switch, if the temperature difference equal to or greater than the abnormality judgment threshold is equal to or greater than the predetermined value above the abnormality judgment threshold, the judgment unit judges that the cause of the abnormal heating is poor fastening of the terminal portion, and if the temperature difference equal to or greater than the abnormality judgment threshold is equal to or greater than the predetermined value above the abnormality judgment threshold, the judgment unit judges that the cause of the abnormal heating is poor contact of the switch or poor fastening of the terminal portion.

[0015] The invention of claim 5 is characterized in that the outside air temperature measuring means is constituted by a temperature sensor embedded in a sealing metal member provided on the outer box. Effect of the Invention

[0016] According to the present invention, it is possible to provide an electricity meter that can detect a temperature rise that is predicted to lead to damage to the meter at an optimal position and that can easily optimize the temperature abnormality judgment threshold when detecting a temperature rise. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram of an electricity meter according to an embodiment of the present invention. [Diagram 2] 1 is a block diagram showing an example of the configuration of a watt-hour meter according to an embodiment of the present invention; [Diagram 3] 2 is a schematic diagram showing a configuration of a conductive part of the watt-hour meter according to the present embodiment. FIG. [Figure 4] 1 shows an example of a temperature detector used in the electricity meter according to this embodiment, where FIG. 1(a) is a temperature sensor for measuring the outside air temperature, and FIG. 1(b) is a temperature sensor for measuring the internal temperature. [Diagram 5] 4 is a flowchart for explaining the operation of the electricity meter according to the present embodiment. [Figure 6]6 is a flowchart for explaining an operation for identifying a position of a temperature rise (a heat generation location) in the watt-hour meter according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a watt-hour meter according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0019] Embodiment Basic configuration FIG. 1 shows a schematic configuration of an electricity meter 1 with a temperature anomaly monitoring function according to this embodiment, and illustrates the meter in a state in which a cover member (not shown) of a terminal portion 31 is removed.

[0020] Note that the electricity meter 1 will be described as a low-voltage electronic electricity meter (smart meter) with a single-phase three-wire wiring method, but it is not limited to this and may be a single-phase two-wire, three-phase three-wire, or electricity meter with another wiring method.

[0021] That is, this watt-hour meter 1 has a case member 3 forming an outer box and a cover member (not shown), as shown in Fig. 1. The case member 3 and the cover member (not shown) are made of resin, and cover (house) various internal circuits 2 provided in a base member 6 for measuring the amount of power used.

[0022] The case member 3 is provided with a display section 5 and a sealing section 21. The display section 5 is provided with an effective power indicator 5a that displays the measured amount of power usage, and an alarm signal indicator 5b that lights up when the conductive section 30 forming the current circuit experiences a temperature rise (abnormal heat generation).

[0023] The sealing section 21 is the part where a sealing screw (metal member) 26 for performing certification sealing of the instrument is fastened with a cover member (not shown) attached, and has a sealing cap 25 to be placed over the sealing screw 26 after sealing, and a closing member 23.

[0024] In the case of this embodiment, as shown in Fig. 2, for example, a thermistor (temperature sensor serving as an outside air temperature detection means) 27 is disposed inside the sealing screw 26 of the sealing part 21. As shown in Fig. 4(a), for example, the thermistor 27 is for detecting the temperature around the instrument (outside air temperature), and resin 28 is embedded around it.

[0025] In FIG. 1, the base member 6 has various internal circuits 2, such as a communication circuit 10 and a terminal portion 31 connected via a cable 11, arranged thereon, and is covered with a cover member (not shown) that can be connected to the case member 3 before sealing.

[0026] 2, the terminal section 31 is provided with power supply terminals 32 (32a, 32b, 32c) to which a power supply side distribution line (connection line) is fastened, and load terminals 33 (33a, 33b, 33c) to which a load side distribution line to which a household electric appliance is connected is fastened. The power supply terminals 32 and the load terminals 33 are each provided with screws (1S to 3S screws, 1L to 3L screws) for fastening the power supply side distribution line.

[0027] FIG. 2 is a block diagram showing an example of the configuration of the watt-hour meter 1 according to the embodiment of the present invention.

[0028] 2, in the watt-hour meter 1 according to this embodiment, the power supply terminal (1S) 32a and the load terminal (1L) 33a are connected via a 1S, 1L metal conductor 35 serving as a current conductor constituting the conductive section 30. Similarly, the power supply terminal (2S) 32b and the load terminal (2L) 33b are connected via a 2S, 2L metal conductor 36 serving as a current conductor constituting the conductive section 30, and the power supply terminal (3S) 32c and the load terminal (3L) 33c are connected via a 3S, 3L metal conductor 37 serving as a current conductor constituting the conductive section 30.

[0029] As a result, in the conductive portion 30, the AC voltage from the distribution line connected to the power supply terminals 32 (32a, 32b, 32c) is supplied to the load terminals 33 (33a, 33b, 33c) via the 1S, 1L metal conductors 35, the 2S, 2L metal conductors 36, and the 3S, 3L metal conductors 37.

[0030] That is, a current corresponding to the consumption of the electric device connected between the load terminal (1L) 33a and the load terminal (2L) 33b flows through the 1S, 1L metal conductor 35 and the 2S, 2L metal conductor 36. Similarly, a current corresponding to the consumption of the electric device connected between the load terminal (3L) 33c and the load terminal (2L) 33b flows through the 3S, 3L metal conductor 37 and the 2S, 2L metal conductor 36.

[0031] 2, the 1S, 1L metal conductor 35 is provided with a 1-side current detector 41, a 1-side temperature detector (A) 43A, a 1-side switch 38, and a 1-side temperature detector (B) 43B in this order from the power supply terminal (1S) 32a side toward the load terminal (1L) 33a side. More specifically, the 1-side temperature detector (A) 43A is disposed in a portion 35a of the 1S, 1L metal conductor 35 on the power supply terminal (1S) 32a side of the 1-side switch 38. The 1-side temperature detector (B) 43B is disposed in a portion 35b of the 1S, 1L metal conductor 35 on the load terminal (1L) 33a side of the 1-side switch 38, as shown in FIG. 3.

[0032] Similarly, in Fig. 2, the 3S, 3L metal conductor 37 is provided with a 3-side current detector 42, a 3-side temperature detector (A) 44A, a 3-side switch 39, and a 3-side temperature detector (B) 44B in this order from the power supply terminal (3S) 32c side toward the load terminal (3L) 33c side. More specifically, the 3-side temperature detector (A) 44A is disposed in a portion 37a of the 3S, 3L metal conductor 37 on the power supply terminal (3S) 32c side of the 3-side switch 39, as shown in Fig. 3, for example. The 3-side temperature detector (B) 44B is disposed in a portion 37b of the 3S, 3L metal conductor 37 on the load terminal (3L) 33c side of the 3-side switch 39, as shown in Fig. 3, for example.

[0033] The 1-side temperature detector 43 ((A) 43A, (B) 43B) and the 3-side temperature detector 44 ((A) 44A, (B) 44B) are both configured with a temperature sensor as an internal temperature detection means such as a thermistor, as shown in Fig. 4(b). The 1-side temperature detector 43 and the 3-side temperature detector 44 are both directly attached to the 1S, 1L metal conductors 35 and the 3S, 3L metal conductors 37 via screws or the like (not shown).

[0034] Here, the electricity meter 1 of this embodiment is equipped with a temperature abnormality monitoring function that detects abnormalities in the internal temperature depending on the outside air temperature of the meter. Details will be described later, but the installation positions (temperature measurement points) of the first-side temperature detector (A) 43A, (B) 43B and the third-side temperature detector (A) 44A, (B) 44B are determined after comparing the accuracy of actual measurement data with thermal analysis data.

[0035] In FIG. 2, a 1-side voltage detector 46 is connected between the 1S, 1L metal conductor 35 and the 2S, 2L metal conductor 36, and a 3-side voltage detector 47 is connected between the 3S, 3L metal conductor 37 and the 2S, 2L metal conductor 36.

[0036] An output terminal of the 1-side voltage detector 46 is connected to one input terminal of the 1-side multiplication circuit 51. An output terminal of the 1-side current detector 41 is connected to the other input terminal of the 1-side multiplication circuit 51, and in this 1-side multiplication circuit 51, the 1-side power is calculated from the transformed output (detected voltage) of the 1-side voltage detector 46 and the transformed output (detected current) of the 1-side current detector 41.

[0037] The output terminal of the three-side voltage detector 47 is connected to one input terminal of the three-side multiplication circuit 52. The output terminal of the three-side current detector 42 is connected to the other input terminal of the three-side multiplication circuit 52, and in this three-side multiplication circuit 52, three-side power is calculated from the transformed output (detected voltage) of the three-side voltage detector 47 and the transformed output (detected current) of the three-side current detector 42.

[0038] An integrating circuit 54 is connected to the 1-side multiplier circuit 51 and the 3-side multiplier circuit 52. In the integrating circuit 54, the 1-side power calculated by the 1-side multiplier circuit 51 and the 3-side power calculated by the 3-side multiplier circuit 52 are used to integrate the amount of power on the load side.

[0039] The integrating circuit 54 is connected to the active power display 5a of the display unit 5, and is configured to display the power amount calculated by the integrating circuit 54.

[0040] On the other hand, the 1-side temperature detectors (A) 43A, (B) 43B and the 3-side temperature detectors (A) 44A, (B) 44B are connected to an A / D conversion circuit 53. In this A / D conversion circuit 53, the detected temperatures of the 1S, 1L metal conductors 35 detected by the 1-side temperature detectors (A) 43A, (B) 43B and the detected temperatures of the 3S, 3L metal conductors 37 detected by the 3-side temperature detectors (A) 44A, (B) 44B are converted into digital values.

[0041] The A / D conversion circuit 53 is connected to a judgment circuit 55 as a judgment section. The judgment circuit 55 is connected to the first-side switch 38 and the third-side switch 39, and is also connected to the thermistor 27 provided inside the sealing screw 26 of the sealing section 21 via the A / D conversion circuit 48.

[0042] The determination circuit 55 compares the temperature of the 1S, 1L metal conductor 35 detected by the 1-side temperature detectors (A) 43A, (B) 43B, the temperature of the 3S, 3L metal conductor 37 detected by the 3-side temperature detectors (A) 44A, (B) 44B, and the outside air temperature detected by the thermistor 27. If either the temperature difference between the temperature detected by the 1S, 1L metal conductor 35 or the temperature detected by the 3S, 3L metal conductor 37 and the outside air temperature exceeds a temperature threshold (temperature abnormality determination threshold) described later, the determination circuit 55 is configured to output an alarm signal (notification of an abnormal state).

[0043] The alarm signal is sent to the alarm signal display 5b of the display unit 5 and to the communication circuit 10 via the cable 11, and is used for display on the alarm signal display 5b and for communication with the outside.

[0044] In addition, in the judgment circuit 55, when the absolute value of the detected temperature of the 1S, 1L metal conductor 35 or the detected temperature of the 3S, 3L metal conductor 37 exceeds the judgment value and is about to reach an abnormal temperature that may lead to damage to the instrument, an open signal for opening operation is output to the 1-side switch 38 and the 3-side switch 39.

[0045] That is, when the absolute value of the detected temperature exceeds, for example, 120°C which is the deflection temperature under load of the resin material constituting the internal circuit 2 or the case member 3 or the cover member (not shown), an abnormal condition is notified to the outside, and the first-side switch 38 or the third-side switch 39 is opened before the instrument is deformed.

[0046] Although details will be described later, in this embodiment, the judgment value is a value obtained by converting half the power loss of the current circuit (for example, 1.5 W), which is the standard (rated value) of the watt-hour meter 1, into a heat generation temperature. As a result, when the absolute value of the detected temperature exceeds the judgment value, the current circuit is cut off, making it possible to suppress a rise in temperature due to abnormal heat generation, and as a result, deformation of the meter can be prevented in advance.

[0047] Furthermore, even if the absolute value of the detected temperature does not exceed 120° C., if the difference (temperature difference) between any of the detected temperatures and the outside air temperature exceeds a temperature abnormality determination threshold (temperature threshold) based on the outside air temperature, which will be described later, the determination circuit 55 will similarly notify of an abnormal state. However, at this stage, it is determined that the detected temperature has not yet risen to a temperature that would cause deformation, and only a notification of an abnormal state is issued.

[0048] If either the difference between the detected temperature and the outside air temperature is higher than the temperature threshold value, for example, by 5° C. or more, a location (heat generating location) where the temperature is estimated to have increased due to abnormal heat generation is identified.

[0049] The various internal circuits 2 of the electricity meter 1 in this embodiment are configured by the 1-side current detector 41, the 3-side current detector 42, the 1-side temperature detectors (A) 43A, (B) 43B, the 3-side temperature detectors (A) 44A, (B) 44B, the 1-side voltage detector 46, the 3-side voltage detector 47, the 1-side multiplication circuit 51, the 3-side multiplication circuit 52, the A / D conversion circuits 48, 53, the integrator circuit 54, the judgment circuit 55, the communication circuit 10, and the conductive section (current circuit) 30.

[0050] In this embodiment, heat generation in the watt-hour meter 1 is actually reproduced (actually measured) in advance, and for those that cannot be reproduced, a thermal analysis simulation is performed to estimate locations where abnormal heat generation is likely to occur (particularly the contact parts of the 1-side switch 38 and the 3-side switch 39, and the screw fastening parts of the power supply terminal 32 and the load terminal 33). Then, based on the results of the estimation, the actual temperature threshold of the determination circuit 55, the mounting positions of the 1-side temperature detectors (A) 43A and (B) 43B relative to the 1S, 1L metal conductor 35, and the mounting positions of the 3-side temperature detectors (A) 44A and (B) 44B relative to the 3S, 3L metal conductor 37 are determined.

[0051] Here, in order to convert the power loss into heat generation temperature, a geometric model of the watt-hour meter 1 is created, and even if there are multiple locations where abnormal heat generation occurs, a judgment is made as to whether or not each heat generation exceeds an abnormal temperature, based on 1.5 W (judgment value). This makes it easy to estimate the location of abnormal heat generation in the watt-hour meter 1 before the meter is damaged.

[0052] In addition, by arranging temperature sensors in optimal locations, the number of sensors can be reduced and heat generation locations can be easily identified (estimated). This means that only the defective parts can be addressed, eliminating the need to replace the entire instrument, resulting in improved maintainability and operating costs.

[0053] The heat value and resistance value of the heat generating portion related to anomaly detection will be explained below.

[0054] In this embodiment, as shown in FIG. 3, for example, portions 35a, 35b, 37a, 37b of the 1S, 1L metal conductor 35 and the 3S, 3L metal conductor 37 are assumed to be heat generating points, and 1-side temperature detectors (A) 43A, (B) 43B and 3-side temperature detectors (A) 44A, (B) 44B are arranged at the respective portions 35a, 35b, 37a, 37b.

[0055] In other words, if we assume that each of the portions 35a, 35b, 37a, and 37b of the 1S, 1L metal conductor 35 and the 3S, 3L metal conductor 37 is a heat generating point, the resistance value [mΩ] and the amount of heat generated [W] under certain conditions (for example, the worst conditions under which the temperature rises the most under normal conditions) are expressed as shown in Table 1 below.

[0056] [Table 1]

[0057] In Table 1, the heat generation amounts of the 1-side and 3-side terminals 32a, 33a, 32c, and 33c are calculated from the actual measured resistance values ​​of the 1-side and 3-side terminals 32a, 33a, 32c, and 33c.

[0058] As an example of abnormal heat generation, when the contact resistance value of the 1-side switch 38 is 1.27 mΩ and the contact resistance value of the 3-side switch 39 is 1.37 mΩ as shown in Table 1, the total resistance value of both sides 1 and 3 is 1.67 mΩ. Since the total heat generation amount of both sides 1 and 3 is 1.5 W, it is necessary to judge that an abnormality has been detected under this worst-case condition.

[0059] In this way, by allocating resistance values ​​to each heat generation point and setting them so that the total heat generation amounts of sides 1 and 3 are both 1.5 W (determination value) or more in the event of abnormal heat generation, it is possible to determine whether or not abnormality can be detected under various envisioned conditions.

[0060] Next, the method of detecting anomalies will be described in more detail.

[0061] Table 2 below shows the heat generation [W] · resistance value [mΩ] · temperature [℃] of each heat generation point under the worst-case conditions when the temperature rises the most under normal conditions, and Table 3 below shows the temperature threshold [℃] of each heat generation point (denoted as temperature measurement points 1S, 1L, 3S, 3L) under the worst-case conditions when the temperature rises the most under normal conditions.

[0062] [Table 2]

[0063] In Table 2, the resistance value of each contact of the 1-side and 3-side switches 38 and 39 is 0.45 mΩ, and the resistance value of each part 35a, 35b, 37a, and 37b (denoted as 1S screw, 3S screw, 1L screw, and 3L screw) is 0 Ω. The reason for this is that, for example, the upper limit of the switch manufacturer's factory specifications is 0.45 mΩ, and the contact resistance value when fastened with the minimum specified torque value (1.84 N) for fastening the electric wire, which is the specification for the watt-hour meter, is approximately 0 Ω.

[0064] [Table 3]

[0065] In Table 3, the temperature thresholds for each temperature measurement point 1S, 1L, 3S, 3L are the temperature differences between the temperatures of each part 35a, 35b, 37a, 37b (shown in Table 2 as 1S screw, 1L screw, 3S screw, 3L screw) when the outside air temperature is 23.0°C under the worst-case conditions in which the temperature rises the most under normal conditions.

[0066] That is, the 1S, 1L metal conductor 35 and the 3S, 3L metal conductor 37 are assumed to be heat generating points 35a, 35b, 37a, 37b, and the 1S, 1L metal conductor 35 and the 3S, 3L metal conductor 37 are respectively arranged at the temperature measurement points 1S, 1L, 3S, 3L with 1-side temperature detectors (A) 43A, (B) 43B and 3-side temperature detectors (A) 44A, (B) 44B.

[0067] In addition, the temperature difference between the temperatures at the temperature measurement points 1S, 1L, 3S, and 3L detected by the 1-side temperature detector (A) 43A, (B) 43B and the 3-side temperature detector (A) 44A, (B) 44B and the outside air temperature detected by the thermistor 27 is calculated.

[0068] If any one of the obtained temperature differences exceeds the temperature threshold, it is determined that there is an abnormality, and if not, it is determined that there is a normality.

[0069] Here, the temperature difference from the temperature threshold value under each condition will be described with reference to Table 4 shown later.

[0070] [Table 4]

[0071] In Table 4, condition 1 is the highest temperature condition, which is set to detect abnormal temperature (temperature rise) due to improper screw tightening at the load terminals (1L) 33a, (3L) 33c, and is set so that the temperature of the 1S, 1L metal conductor 35 (14.8°C) and the temperature of the 3S, 3L metal conductor 37 (15.3°C) show an increase of 10°C or more with respect to the temperature threshold. This makes it possible to detect abnormal heat generation due to improper screw tightening at the load terminals (1L) 33a, (3L) 33c. It is also possible to identify the location of heat generation from the increase.

[0072] Condition 2 is the condition where the temperature becomes the highest, which is set to detect temperature abnormalities caused by improper screw tightening at the power supply terminals (1S) 32a, (3S) 32c, and is set, for example, so that the temperature of the 1S, 1L metal conductor 35 (17.9°C) and the temperature of the 3S, 3L metal conductor 37 (15.6°C) show an increase of 10°C or more with respect to the temperature threshold. This makes it possible to detect abnormal heat generation caused by improper screw tightening at the power supply terminals (1S) 32a, (3S) 32c. It is also possible to identify the location of heat generation from the increase in temperature.

[0073] Condition 3 is a condition set for detecting temperature abnormalities caused by defective contact resistance of the 1-side and 3-side switches 38, 39, and is set, for example, so that the temperatures of the 1S, 1L metal conductors 35 (11.1°C, 7.3°C) and the 3S, 3L metal conductors 37 (13.6°C, 13.5°C) rise almost evenly with respect to the temperature threshold, and the sum of the temperatures is high. This makes it possible to detect abnormal heat generation caused by defective contact resistance of the 1-side and 3-side switches 38, 39.

[0074] Condition 4 is a condition where heat is generated at a plurality of locations, which is set to detect temperature abnormalities due to improper screw fastening at the power supply terminals (1S) 32a, (3S) 32c and the load terminals (1L) 33a, (3L) 33c, and temperature abnormalities due to improper contact resistance of the 1-side and 3-side switches 38, 39, and is set, for example, so that the temperatures of the 1S, 1L metal conductors 35 (8.9°C, 6.9°C) and the 3S, 3L metal conductors 37 (11.6°C, 10.6°C) rise almost evenly relative to the temperature threshold. This makes it possible to detect abnormal heat generation due to improper screw fastening at the power supply terminals (1S) 32a, (3S) 32c and the load terminals (1L) 33a, (3L) 33c, and abnormal heat generation due to improper contact resistance of the 1-side and 3-side switches 38, 39.

[0075] Condition 5 is a condition where heat is generated almost uniformly at multiple locations, which is set to detect temperature abnormalities due to improper screw tightening at the power terminals (1S) 32a, (3S) 32c and the load terminals (1L) 33a, (3L) 33c, and temperature abnormalities due to defective contact resistance of the 1-side and 3-side switches 38, 39, and is set, for example, so that the temperature (15.3°C) of the 1S, 1L metal conductor 35 and the temperature (15.2°C) of the 3S, 3L metal conductor 37 show an increase of 10°C or more with respect to the temperature threshold. This makes it possible to detect abnormal heat generation due to improper screw tightening at the load terminals (1L) 33a, (3L) 33c, and abnormal heat generation due to defective contact resistance of the 1-side and 3-side switches 38, 39.

[0076] In this way, by repeatedly performing thermal analysis simulation under five different conditions 1 to 5, the optimal temperature measurement points 1S, 1L, 3S, 3L and temperature threshold values ​​can be obtained from the temperature distribution under each of conditions 1 to 5.

[0077] Operation explanation With reference to FIG. 5, a process flow for an anomaly detection operation in the watt-hour meter 1 according to this embodiment will be briefly described.

[0078] 5, first, the 1-side temperature detectors (A) 43A, (B) 43B detect the temperatures of the portions 35a, 35b (referred to as the 1S screw and the 1L screw) of the 1S, 1L metal conductor 35, and the 3-side temperature detectors (A) 44A, (B) 44B detect the temperatures of the portions 37a, 37b (referred to as the 3S screw and the 3L screw) of the 3S, 3L metal conductor 37. In addition, the thermistor 27 provided inside the sealing screw 26 of the sealing part 21 detects the outside air temperature at that time (the above is step S01).

[0079] Then, in the judgment circuit 55, it is judged whether the absolute values ​​of the detected temperatures of each of the parts 35a, 35b, 37a, 37b detected by the 1-side temperature detector (A) 43A, (B) 43B and the 3-side temperature detector (A) 44A, (B) 44B, respectively, are 120°C or higher (step S02).

[0080] If any one of the absolute values ​​of the detected temperatures of the parts 35a, 35b, 37a, and 37b is determined to be 120°C or higher (YES in step S02), the judgment circuit 55, for example, lights up the alarm signal indicator 5b of the display unit 5 to notify of an abnormal condition (step S03).

[0081] Furthermore, an open signal is output from the determination circuit 55 to the first-side switch 38 and the third-side switch 39, so that the first-side switch 38 and the third-side switch 39 are opened before the meter is deformed (step S04).

[0082] On the other hand, if the absolute value of the detected temperature of each of the parts 35a, 35b, 37a, 37b is less than 120° C. (NO in step S02), the temperature difference between the detected temperature of each of the parts 35a, 35b, 37a, 3 and the outside air temperature is calculated (step S05).

[0083] If it is determined that any one of the calculated temperature differences exceeds the temperature threshold (temperature abnormality determination threshold) (YES in step S05), the determination circuit 55 notifies the abnormality by, for example, turning on the alarm signal indicator 5b of the display unit 5. The determination circuit 55 also identifies the abnormal location (heat generating location) (step S06).

[0084] If it is determined that none of the obtained temperature differences exceed the temperature threshold value (NO in step S05), the judgment circuit 55 determines that there are no abnormal locations where the temperature has risen due to heat generation (normal), and the series of processes is terminated.

[0085] Here, as shown in FIG. 6, when one of the obtained temperature differences (any of the 1S screw, 1L screw, 3S screw, or 3L screw) is higher than the temperature threshold value by, for example, a predetermined value of 5° C. or more (YES in step S61), the judgment circuit 55 judges that the screw at the exceeding point is not properly tightened (step S62).

[0086] On the other hand, if the temperature difference between the 1S screw and the 1L screw is, for example, within 5°C of the temperature threshold value (NO in step S61, YES in step S63), the judgment circuit 55 judges that the resistance value of the contacts of the 1-side switch 38 is defective based on the temperature difference between the 1S screw and the 1L screw (step S64).

[0087] Furthermore, if the temperature difference between the 3S screw and the 3L screw is, for example, within 5°C of the temperature threshold value (NO in step S61, YES in step S63), the judgment circuit 55 judges that the resistance value of the contacts of the three-side switch 39 is defective based on the temperature difference between the 3S screw and the 3L screw (step S64).

[0088] Furthermore, if the temperature difference between the 1S screw and the 1L screw, or the temperature difference between the 3S screw and the 3L screw is not within 5°C of the temperature threshold value (NO in step S61, NO in step S63), the judgment circuit 55 judges that either a tightening defect in the 1S screw, the 1L screw, the 3S screw, or the 3L screw and a defect in the resistance value of the contacts of the 1-side and 3-side switches 38, 39 have occurred simultaneously (step S65).

[0089] In the present embodiment, it is assumed that the probability of abnormal heat generation occurring simultaneously at multiple locations is extremely low when the temperature changes approximately uniformly due to improper tightening of the 1S screw, 1L screw, 3S screw, and 3L screw and / or improper resistance of the contacts of the 1-side and 3-side switches 38, 39.

[0090] In this way, by setting the judgment criteria as, for example, whether the temperature is 5°C higher or lower than the temperature threshold, it becomes possible to more reliably predict abnormal heat generation due to improper tightening of the 1S screw, 1L screw, 3S screw, and 3L screw and / or poor resistance of the contacts of the 1-side and 3-side switches 38, 39.

[0091] As described above, according to the electricity meter 1 of this embodiment, a temperature rise that is predicted to lead to damage to the meter can be detected (predicted) at a more optimal location, and the temperature abnormality judgment threshold value when detecting a temperature rise can be easily optimized.

[0092] That is, in the electricity meter 1 equipped with a temperature abnormality monitoring function, the change in temperature rise of the current circuit is judged based on the outside air temperature and the magnitude of the load current, and half the specified value for the power loss of the current circuit is converted into a temperature and used as the threshold for determining an abnormality, making it easy to identify the threshold temperature for abnormal heat generation.

[0093] Moreover, the power losses during normal and abnormal conditions are set as a thermal analysis model, and based on the simulation results (thermal analysis data), the optimal temperature threshold value of the conductor temperature at which an abnormality can be determined and the installation positions of the temperature detectors 43, 44 are determined.

[0094] This allows the temperature detectors 43, 44 to be effectively positioned at optimal heat generating locations, thereby reducing the number of temperature detectors, enabling heat generating locations to be identified, and eliminating the need to replace the entire instrument, resulting in improved maintainability and operating costs. [Explanation of symbols]

[0095] 1 Energy meter 5 Display section 5b Alarm signal indicator 21 Sealing Section 26 Sealing screw 27 Thermistor (Means for detecting outside air temperature / Temperature sensor) 30 Conductive part (current circuit) 31 Terminal section 32 Power terminal 32a Power terminal (1S) 32b Power supply terminal (2S) 32c power supply terminal (3S) 33 Load terminal 33a Load terminal (1L) 33b Load terminal (2L) 33c Load terminal (3L) 35 1S, 1L Metal Conductors (Current Conductors) 35a part 35b part 36 2S, 2L Metal Conductors (Current Conductors) 37 3S, 3L Metallic Conductors (Current Conductors) 37a part 37b part 38 1 side switch 39 3-side switch 43 1-side temperature detector (internal temperature detection means) 43A 1 side temperature detector (A) 43B 1 side temperature detector (B) 44 3-side temperature detector (internal temperature detection means) 44A 3-side temperature detector (A) 44B 3-side temperature detector (B) 48,53 A / D conversion circuit 55 Judgment circuit (judgment section)

Claims

1. a terminal unit having a power supply terminal to which a power supply side distribution line is fastened and a load terminal to which a load side distribution line is fastened; a conductive portion having a switch and provided between the power supply terminal and the load terminal of the terminal portion; an internal temperature measuring means for measuring the terminal temperatures of the power supply terminal and the load terminal at respective measurement points of the terminal portion; an outside air temperature measuring means for measuring an outside air temperature around an outer casing in which the conductive portion and the terminal portion are provided; a determination unit which, when at least any of the absolute values ​​of the terminal temperatures measured at the respective measurement points by the internal temperature measuring means is equal to or greater than a predetermined determination value, determines that a temperature is abnormal and opens the switch of the conductive unit, and, when the absolute value of each terminal temperature is less than the determination value, determines a temperature difference between each terminal temperature and the outside air temperature, and, when at least any of the determined temperature differences is equal to or greater than a predetermined abnormality determination threshold value, determines that the cause of the abnormal heat generation is a fastening defect at the measurement point where the terminal temperature was measured; A watt-hour meter comprising:

2. 2. The watt-hour meter according to claim 1, wherein the internal temperature measuring means determines the measurement location and the temperature abnormality determination threshold value based on actual measurement data and thermal analysis data obtained by a thermal analysis simulation.

3. The electricity meter according to claim 1, characterized in that the judgment unit notifies an abnormal state to the outside via a notification means when at least any of the absolute values ​​of the terminal temperatures is equal to or greater than the judgment value and when at least any of the temperature differences is equal to or greater than the abnormality judgment threshold.

4. When the absolute value of each of the terminal temperatures is less than the determination value and at least one of the temperature differences is equal to or greater than the abnormality determination threshold, If the temperature difference equal to or greater than the abnormality determination threshold is within a predetermined value from the abnormality determination threshold, it is determined that the cause of the abnormal heat generation is a contact failure of the switch; If the temperature difference equal to or greater than the abnormality determination threshold is equal to or greater than a predetermined value greater than the abnormality determination threshold, it is determined that the abnormal heat is caused by a fastening defect of the terminal portion; If the temperature difference equal to or greater than the abnormality determination threshold is equal to or greater than the abnormality determination threshold by a predetermined value, it is determined that the cause of the abnormal heat generation is a contact failure of the switch or a fastening failure of the terminal portion.

2. The watt-hour meter according to claim 1 .

5. 2. The watt-hour meter according to claim 1, wherein the outside air temperature measuring means is configured by a temperature sensor embedded in a sealing metal member provided on the outer casing.

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