JP2012008139A - Tracking current detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tracking current detector capable of precisely detecting occurrence of a tracking phenomenon in a different viewpoint from the conventional art.SOLUTION: A tracking current detector includes: a current detection unit 3 for detecting a load current flowing commercial electric circuits 1 and 1'; an A/D conversion unit 5 for converting a current waveform detected by the current detection unit into digital values; a first register 6 storing the digital values of a prescribed period output from the A/D conversion unit 5; a calculation unit 7 for calculating a form factor from the digital values of the prescribed period stored in the first register by a prescribed calculation; a second register 8 retaining the calculation results for every prescribed period acquired by the calculation unit 7; and a determination unit 9 determining whether the tracking current is generated or not by comparing the calculation result retained in the second register 8 with prescribed conditions.

Description

The present invention relates to a device for preventing the occurrence of a fire by detecting the occurrence of a tracking phenomenon in which a carbonized conductive path is formed in an organic electrical insulator and a current flows through the carbonized conductive path.

Conventionally, when a carbonized conductive path is formed in the insulator (resin) between the electrodes (blades) of the plugs of an electric machine instrument inserted into an outlet, a current due to the voltage between the electrodes flows through the carbonized conductive path, It is known that a so-called tracking fire occurs, in which the resin insulation of the plug is ignited by Joule heat due to current and resistance, resulting in a fire.

The tracking fire is not limited to the plug described above, and it is known that a tracking fire occurs between terminals of a wiring device or an electric machine device having a terminal on a resin insulator such as a circuit breaker.

In such a tracking fire, the magnitude of the flowing current is often smaller than the current consumed by other electric machinery and equipment at each stage from the very initial stage where the carbonized conductive path is formed to the ignition. This is one of the phenomena that is difficult to detect or protect with general overcurrent protection devices such as circuit breakers and fuses.

For this reason, technologies have been developed that detect the occurrence of a phenomenon based on the presence or absence of high-frequency components in the current, changes in the peak value of the current, rises in the current, and changes in the phase of the peak.

JP-A-57-193924 JP-A-9-5379 JP-A-10-14086 JP 2000-324676 A JP 2001-103657 A JP 2001-289900 A JP 2001-289903 A JP 2001-324529 A JP 2001-324533 A Japanese Patent Application Laid-Open No. 2004-20496 JP 2004-22172 A JP 2004-22462 A JP 2004-279205 A JP 2004-153877 A

However, recent electromechanical appliances have a power source that directly rectifies commercial alternating current without using a transformer and smoothes it with a capacitor, and intentionally current control such as frequency control and SCR firing angle control as seen in inverters. Many of them have controlled waveforms, and the current waveform is not a simple sine wave. Therefore, it is difficult to accurately distinguish between the current caused by the tracking phenomenon and the current caused by the use of a general electromechanical device. Yes.

Therefore, the present invention is intended to provide a means that can more accurately detect the occurrence of the tracking phenomenon from a viewpoint different from the prior art.

According to a first aspect of the present invention, there is provided a tracking current detecting device for detecting a tracking current generated in a commercial electric circuit, a current detecting unit provided in the commercial electric circuit for detecting a load current flowing through the commercial electric circuit, and the current detecting unit An A / D converter that converts the current waveform into a digital value, a first register that stores a digital value for a predetermined period output from the A / D converter, and a first register that stores the digital value A calculation unit for calculating a waveform rate by a predetermined calculation from the digital value for the predetermined period, a second register for holding a calculation result for each predetermined period obtained by the calculation unit, And a determination unit that determines whether or not a tracking current is generated by comparing with a predetermined condition based on a calculation result held in the second register, in the commercial electric circuit Is obtained by providing a tracking current detecting device is characterized in that it comprises the form factor to determine the elements of the detection of a tracking current flowing between electrode load current flows.

According to a second aspect of the present invention, there is provided a tracking current detecting device for detecting a tracking current generated in a commercial electric circuit, a current detecting unit provided in the commercial electric circuit for detecting a load current flowing in the commercial electric circuit, and the current detecting unit An A / D converter that converts the current waveform into a digital value, a first register that stores a digital value for a predetermined period output from the A / D converter, and a first register that stores the digital value A waveform difference detector for calculating a difference for each period from the digital value for the predetermined period, a second register for storing data of the difference for each period obtained by the calculation of the waveform difference detector; A calculation unit that calculates a waveform rate by a predetermined calculation from the difference data for each cycle stored in the second register, and a calculation unit that holds the calculation result for each predetermined cycle obtained by the calculation unit. Three registers, A determination unit that determines whether or not a tracking current is generated by comparing with a predetermined condition based on an operation result held in the third register, and comprising a load current in the commercial circuit A tracking current detection device is provided in which the waveform rate is included in a determination element for detecting a tracking current flowing between poles.

According to the first aspect of the present invention, the waveform factor of the current is included in the detection determination element, so that it is possible to provide an apparatus capable of more accurately detecting the occurrence of the tracking phenomenon.

According to the second aspect of the present invention, the data of the difference of the detection current for each cycle is obtained, and the current waveform rate is included in the detection judgment element, so that the influence of the steady current can be canceled and the tracking phenomenon It is possible to provide a means capable of more accurately detecting the occurrence of.

Waveform example of inrush current of vacuum cleaner Example of current waveform during air compressor operation Example of current waveform during operation of microwave oven Example of current waveform during fan rotation Example of current waveform when using a personal computer Current waveform example 1 of tracking phenomenon (during scintillation) Current waveform example 2 of tracking phenomenon (during scintillation) Example of current waveform of tracking phenomenon (early ignition) Example of current waveform of tracking phenomenon (late firing) The figure which piled up the crest factor and the waveform rate which were calculated for every cycle on the waveform of the inrush current of the cleaner shown in FIG. The figure which piled up the crest factor and the waveform rate which were calculated for every period on the current waveform at the time of the operation of the air compressor which is shown in FIG. The figure which piled up the crest factor and the waveform rate which were calculated for every period on the current waveform at the time of operation of the microwave oven shown in FIG. The figure which piled up the crest factor and the waveform rate which were calculated for every period on the current waveform at the time of rotation of the electric fan shown in FIG. Fig. 5 shows the current waveform when using a personal computer shown in Fig. 5, with the crest factor and waveform factor calculated for each cycle superimposed. A figure in which the crest factor and the waveform rate calculated for each period are superimposed on the current waveform of the tracking phenomenon (during scintillation) shown in FIG. A figure in which the crest factor and waveform rate calculated for each period are superimposed on the current waveform of the tracking phenomenon (during scintillation) shown in FIG. Fig. 8 is a graph in which the crest factor and waveform rate calculated for each cycle are superimposed on the current waveform of the tracking phenomenon (early firing) shown in Fig. 8 A figure in which the wave height rate and the waveform rate calculated for each cycle are superimposed on the current waveform of the tracking phenomenon (late firing) shown in FIG. The figure of the graph which plotted the crest rate and the waveform rate of the waveform of the inrush current of the vacuum cleaner shown in FIG. The figure of the graph which plotted the crest factor of the current waveform at the time of operation of the air compressor shown in FIG. The figure of the graph which plotted the crest factor of the current waveform at the time of operation of the microwave oven shown in FIG. The figure of the graph which plotted the crest factor of the current waveform at the time of rotation of the electric fan shown in FIG. The figure of the graph which plotted the crest factor of the current waveform at the time of use of the personal computer shown in FIG. FIG. 15 is a graph in which the crest factor and the waveform rate of the current waveform of the tracking phenomenon shown in FIG. 15 are plotted with coordinates. FIG. 16 is a graph in which the crest factor and the waveform factor of the current waveform of the tracking phenomenon shown in FIG. 16 are plotted on coordinates. The figure of the graph which plotted the crest factor and the waveform rate of the current waveform of the tracking phenomenon shown in FIG. The figure of the graph which plotted the crest factor and the waveform rate of the current waveform of the tracking phenomenon shown in FIG. Diagram of one embodiment of the present invention Diagram of one embodiment of the present invention FIG. 12 is a diagram of a current waveform obtained by synthesizing the current waveform during operation of the microwave oven shown in FIG. 12 and the current waveform due to the tracking phenomenon shown in FIG. A figure in which the crest factor and the waveform factor calculated for each cycle are superimposed on the current waveform of FIG. FIG. 30 shows a current waveform obtained by taking a difference from the waveform of the immediately preceding cycle for each cycle in the current waveform of FIG. A figure in which the crest factor and the waveform factor calculated for each period are superimposed on the current waveform of FIG. 31 is a graph in which the crest factor and the waveform factor of the current waveform in FIG. 31 are plotted with coordinates. FIG. 33 is a graph in which the crest factor and the waveform factor of the current waveform in FIG. 33 are plotted in coordinates. Diagram of an embodiment of an apparatus using the present invention and a conventional invention in combination

The inventor of this case closely observed and investigated various electric appliances and current waveforms caused by the tracking phenomenon. 1 to 5 are current waveforms due to the use of typical home appliances, FIG. 1 is a waveform of the inrush current of the vacuum cleaner, FIG. 2 is a current waveform during operation of the air compressor, and FIG. 3 is during operation of the microwave oven. 4 is a current waveform when the fan is rotating, and FIG. 5 is a current waveform when a personal computer (switching power supply) is used.

On the other hand, FIGS. 6 to 9 show current waveforms at the time of plug tracking phenomenon, and FIGS. 6 and 7 are stages in which current flows through the carbonized conductive path and is partially red hot at the initial stage of tracking called scintillation. FIG. 8 is a stage at the time when the flame has started to appear after the scintillation stage, and FIG. 9 is a current waveform when the flame is large at a stage called tracking short circuit.

When comparing the current waveform of the home appliance shown in FIGS. 1 to 5 with the current waveform due to tracking shown in FIGS. 6 to 9, the current due to the tracking phenomenon has a small current value except in the tracking short-circuit state of FIG. , Because the waveform changes in a complex manner, it may contain high-frequency components, the change in the current value is large for each half-wave waveform, the current waveform is not sinusoidal, and the current is only in a certain phase range. It turns out that it resembles the waveform of the microwave oven of FIG. 3 and the personal computer (switching power supply) of FIG. These are features on the current waveform that have already been adopted as a detection element of the tracking phenomenon in the prior art.

Here, the inventor of the present invention, as a characteristic of the current waveform due to the tracking phenomenon of FIGS. 6 to 9, is not only that the change in the current value every half cycle is irregular and large, but also the change in the waveform appearance itself. Focused on the fact that is large. In other words, we focused on the fact that the width and height of each half cycle of the waveform changed irregularly.

In general, the crest factor and the waveform rate are known as indices representing the aspect of the AC waveform. The crest factor is obtained by the maximum value / effective value, and the waveform width is narrower and sharper at a portion where a large amount of current flows for a half cycle or one cycle, and the higher the peak value, the larger the value. Further, the waveform rate is obtained as an effective value / average value, and indicates a smaller value as the width of the waveform where a large amount of current flows in a half cycle or one cycle is wider.

Therefore, the inventor of the present case calculates the crest factor and the waveform rate for each period with respect to the waveforms of FIGS. 1 to 9 described above, and superimposes the results on each waveform as shown in FIGS. As shown in FIGS. 19 to 27, the vertical axis represents the wave height rate and the horizontal axis represents the waveform rate.

As a result, the following was found. One of them is that the crest factor of the current due to the tracking phenomenon is irregular and changes compared to the crest factor of the current of home appliances. The tracking phenomenon of FIGS. 15 to 18 is compared to the case where the crest factor of the current of the device of FIGS. 10 to 14 is approximately in the range of 1.4 to 2.7, and the aspect of change is only constant or gradual change. The crest factor of the current due to is in the range of 1.8 to 3.8, the appearance is irregular, and the value changes greatly.

Therefore, for example, when a threshold value is simply provided for the crest factor and a crest factor of a certain value or more is detected, it can be determined that the tracking phenomenon may occur. For example, in the current waveforms of FIGS. 1 to 9, that is, FIGS. 10 to 18, the crest factor shows a value of 3 or more in the cases of FIGS. 15, 17 and 18, all of which are currents during the tracking phenomenon. It is a waveform. It is also possible to provide an appropriate determination section and determine from the value of the crest factor and the waveform ratio in that section. For example, the determination condition may be the crest rate or the number of changes in the waveform rate within the determination interval. That is, based on the determination condition that the number of times the change width from the previous crest factor is 0.5 or more on the + side or the − side in a given crest factor of 0.2 seconds is 2 or more in total. When the waveforms of FIGS. 10 to 18 are selected, the cases of FIGS. 15, 17 and 18 correspond to current waveforms at the time of tracking phenomenon. In that case, it is possible to add a condition such that the changing direction of the crest factor before the value is changed by 0.5 or more is not the same as the direction in which the value is changed by 0.5 or more. The waveform rate is the same. Furthermore, it is also possible to determine by combining conditions such that the crest factor is equal to or greater than the threshold value and the crest factor or the waveform rate has changed more than a certain width is two or more.

Next, in FIG. 19 to FIG. 27, when the aspects of the graphs are compared, in the case of the general household appliances of FIG. 19 to FIG. 23, the tracking phenomenon of FIG. It can be seen that the thing shows the aspect as a group with bulges. That is, in the general household electrical appliances of FIGS. 19 to 23, each value of the crest factor and the waveform rate shows a fixed point or an aspect as a linear function with little variation that changes proportionally, whereas FIG. 27, which is random, includes a change in which the waveform rate decreases even if the crest factor increases in an extreme case, and shows an aspect as a linear function having variations.

Therefore, it is possible to determine whether or not there is a possibility of tracking phenomenon by observing changes in the crest factor and waveform rate within a certain section.

Even if a tracking phenomenon occurs in a part of the electrical circuit, if an electrical machine such as a general household appliance is operating simultaneously in the same electrical circuit, the current waveform due to the tracking phenomenon is the same as the current waveform of the electrical machine. Overlap, in general, the electric machine appliance current is larger, so the above-mentioned crest factor and waveform rate roughly depend on the electric machine appliance current, so the occurrence of the tracking phenomenon cannot be detected. The equipment is not always operated all day, and one tracking phenomenon occurs as long as voltage is applied. Therefore, there is always a time zone in which only the current of the tracking phenomenon flows, and at that time, Detection by such a determination is possible.

The above-described determination based on the crest factor and waveform rate may be combined with other conventional methods such as detection by high frequency, detection by change in peak value of current, detection by rise of current or change in phase of peak value, etc. It can be used.

Next, an embodiment using the present invention will be described in detail with reference to the drawings. FIG. 28 shows an example of a specific detection apparatus. In FIG. 28, 1, 1 'is an electric circuit, and in this example is an example of a single-phase two-wire system. Reference numeral 2 denotes a timing detection unit that detects a commercial AC voltage cycle for each zero cross. 3 is a current detection current transformer, 4 is a burden resistance of the current transformer 3, and the current waveform of one electric circuit is output as a voltage across the burden resistance 4.

An A / D converter 5 converts the voltage appearing at both ends of the burden resistor 4 into a digital value every appropriate sampling time. Reference numeral 6 denotes a first register which stores a digital value for each sampling time corresponding to a half cycle or one cycle as a set of data. Reference numeral 7 denotes an arithmetic unit that calculates either the half-cycle or one-cycle crest factor or the waveform rate, or both the crest factor and the waveform rate, from half-cycle or one-cycle data in the first register 6.

Reference numeral 8 denotes a second register, which holds the calculation results of the seven calculation units in a half cycle or one cycle for an appropriate determination period. Reference numeral 9 denotes a determination unit that determines whether tracking has occurred based on the calculation result held in the second register 8. If it is determined that tracking has occurred, the SCR of 10 is triggered and 11 The relay coil is driven to turn on the 12 alarm contacts to drive an alarm device (not shown) linked to the contacts. The alarm contact 12 may directly cut off the main circuit when tracking is detected as a main circuit contact placed on the electric circuit.

Here, the determination by the determination unit 9 can be performed every half cycle or every cycle. In this case, for the data in the second register, the oldest data among the data for the judgment period is discarded every half cycle or one cycle, and the latest data is newly retained to form a set of data. . The determination may be performed every determination period. In that case, the determination unit 9 makes a determination when the data for the determination period has been prepared, and after the determination, the data in the second register is collectively reset and data for the determination period is newly saved. Can be.

As described above, when a threshold value is simply provided for the crest factor and it is determined whether or not the crest factor value exceeds the threshold value, the second register in FIG. The determination unit 9 can make a determination by directly comparing the result with the threshold value.

When making a judgment based on the crest factor or waveform ratio value within the judgment period, in addition to the method of counting the number of times that the specific change has occurred, count the number of times the crest factor has exceeded the threshold. There is also a method. In addition, as described above, from both the crest factor and the waveform rate, even if the crest factor increases for every half cycle or one cycle within the judgment period, the waveform rate decreases, or conversely, the crest factor decreases. However, if the waveform rate is changing so as to increase, the variation of the crest factor and the waveform rate within the judgment period with respect to the primary regression line is calculated, and the variation exceeds the threshold value. It is possible to set the determination condition as such.

Also, use a method that uses a high-frequency cut-off filter in front of the AD converter, a method in which a threshold is set for the current, and the crest factor and waveform rate are not evaluated for currents below the threshold. Thus, variation in the waveform rate and crest factor due to power supply noise can be suppressed, and the tracking phenomenon can be judged effectively.

When an electrical machine such as a general household appliance is in operation and the current due to the tracking phenomenon is hidden in the current, the explanation was made that it was difficult to detect the tracking phenomenon. There is a method of capturing the waveform of the tracking phenomenon that changes by taking the difference between the previous waveform and the current waveform.

FIG. 29 shows an example of the method. In FIG. 29, 1 and 1 'are electric circuits, 2 is a detection part of the periodic timing of a power supply voltage, 3 is a current transformer, 4 is a burden resistance of the current transformer 3, and the current waveform of the electric circuit 1 is a burden resistance 4 as a voltage. Appears at both ends of. Reference numeral 5 denotes an A / D converter, which converts the voltage across the load resistor 4 into a digital value every appropriate sampling time and stores two cycles in the first register 6. When the data for the next cycle is imported, the older one cycle of the two cycles of data is discarded and the newer one cycle of data is moved to the older one. The latest data for one cycle is taken into the new data storage unit.

Reference numeral 13 denotes a waveform difference detection unit which calculates the difference between the data for the new one cycle and the data for the old one in the first register, and outputs the second difference as data for the new cycle. Store in register 8. 7 is an operation unit, 14 is a third register, 15 is a determination unit, 10 is an SCR, 11 is a relay coil, 12 is an alarm contact, and these functions are the operation unit 7 and the second register 8 in FIG. Since the functions of the unit 9, the SCR 10, the relay coil 11, and the alarm contact 12 are the same, the description thereof is omitted.

Thus, if the difference between the current waveform of the latest one cycle and the current waveform of the previous cycle is taken, even if an electric machine is used, if the current is a steady current, the steady current Since the difference per cycle can be made almost zero, the influence can be canceled. On the other hand, the current due to the tracking phenomenon is not constant because the waveform and the magnitude thereof are constantly changed, and therefore, when the difference is taken every cycle, it can be grasped as a changing waveform. By processing the changing waveform with one or both of the crest factor and the waveform rate, it is possible to obtain a device that can detect the occurrence of the tracking phenomenon even if an electromechanical instrument is used.

The state will be described with reference to FIGS. FIG. 30 is a current waveform simulating the above-described conditions, which is a combination of the current waveform during operation of the microwave oven shown in FIG. 3 and the current waveform at the beginning of tracking firing shown in FIG. FIG. 31 shows a calculation of the crest factor and the waveform rate for each cycle from the current waveform of FIG. 30, and the values are superimposed on the base current waveform. The current value at the beginning of tracking firing is the value when the microwave oven is used. 30 is almost indistinguishable from the waveform shown in FIG. 3 because it is much smaller than the current value. Therefore, in this method, the calculation results of the crest factor and the waveform factor are almost the same as in FIG. 12, and the occurrence of the tracking phenomenon cannot be detected by the apparatus according to the present invention. FIG. 34 is a diagram in which the crest factor based on the calculation result of FIG. 31 is plotted on the vertical axis and the waveform rate is plotted on the horizontal axis.

32 is a current waveform when the difference between the current waveform of FIG. 30 and the current waveform of the previous cycle is taken for each cycle, and FIG. 33 is a diagram in which the calculation results of the crest factor and the waveform rate are superimposed. 35 is a diagram in which the crest factor is plotted on the ordinate and the waveform rate is plotted on the abscissa. The current waveform, the crest factor, and the aspect of the waveform factor in FIGS. 32, 33, and 35 are substantially similar to those in FIGS. Therefore, according to this method, most of the steady current of the electric machine apparatus can be canceled and the tracking current waveform can be captured, so that the occurrence of the tracking phenomenon can be detected by the present invention.

The waveform shown in FIG. 32 does not completely match the tracking current waveform shown in FIG. 8 because the tracking current is also a difference from the waveform one cycle before, and even if it is a steady current assuming cancellation, This is because the waveform is slightly different from the previous cycle. The waveform difference between the steady currents and the previous period becomes noise with respect to the tracking current waveform, and in extreme cases, the crest factor of the waveform difference between the steady currents may be as large as the tracking current. Therefore, instead of taking the difference from the current waveform one cycle before the current in FIG. 30, it is also possible to take a difference from the average waveform for an appropriate period. Further, as in the above-described method, it is possible to take measures such as setting a threshold value for the difference current to eliminate noise and not evaluating the crest factor and the waveform rate for currents below the threshold value.

The device according to the present invention can be used in combination with a conventional device. The technology based on the past published patent publications described in the prior art attempts to detect the occurrence of tracking phenomena that are difficult to detect from the characteristics of the current waveform. It cannot be said that the technology is useful, but it cannot be said that it is not useful at all.

The embodiment shown in FIG. 36 is an embodiment in which the apparatus according to the present invention is used in combination with a conventional apparatus. In the figure, 1, 1 ', 2, 3, 4, 10, 11, and 12 are the same as those in FIGS. Reference numeral 17 denotes the apparatus shown in FIGS. 28 and 29 according to the present invention, which excludes the timing detector, current transformer, burden resistance, SCR, and relay. Reference numeral 16 denotes an apparatus based on the technology of the past published patent publication described in the prior art.

16 and 17 share the current transformer 3 and the burden resistor 4 to detect the occurrence of the tracking phenomenon from the current waveform of the electric circuit by the respective methods, and the final determination unit 18 receives both detection signals to detect the tracking phenomenon. The occurrence is detected more accurately and the SCR 10 is triggered to operate the relay 11.

The final determination unit 18 enters a standby state for an appropriate period when either one of the detection devices 16 or 17 temporarily generates a detection output. When detection output is generated from the remaining devices during the standby period, the final determination unit 18 triggers the SCR 10 to drive the relay 11.

There are a method of calculating the crest factor and the waveform rate every half cycle in the seven arithmetic units of the device of FIG. 28 and the seven arithmetic units of the device of FIG. 29, and a method of performing every cycle. In an alternating current that repeats the same waveform alternately with +-, the value is the same when calculated every half cycle and when calculated every cycle. The steady current due to the use of electromechanical devices is close to such a current.

However, since the current waveform due to the tracking phenomenon is a waveform that changes every half cycle as shown in FIGS. 6 to 9, for example, even if a current flows in a half cycle, a current does not flow in the next half cycle. sell. In addition, in an electrical machine apparatus having a power supply circuit that directly rectifies commercial alternating current by half-wave, only one of the currents of + and − flows.

In such a case, waveforms with and without current appear alternately every half-wave, but the denominator and numerator are zero or very close to zero in the calculation of the crest factor and waveform rate, which is very difficult to calculate. Inconvenient. In this case, there are methods such as substituting the value of the previous half cycle as the calculation result as the calculation result of the half cycle, or calculating in a half cycle skip.

When calculating every cycle, not only such inconvenience does not occur, but also the effective value and average value for each cycle become small, and as a result, the crest factor and the waveform rate become a large value and a normal electric machine This is convenient because it can be easily distinguished from the steady current of the instrument.

The present invention can be used for a device that detects and alerts the occurrence of tracking in the electric circuit after the detection device is installed, and protects the electric circuit by interrupting the electric circuit. In particular, in recent years, there are many aging electrical equipment, and there is a fear that such equipment may cause fire accidents such as tracking due to poor insulation between the electrodes. Renewing the equipment will eliminate the anxiety, but it will be very expensive. Therefore, by providing a detection device such as the present invention in the electric circuit, it becomes possible to eliminate anxiety at a lower cost. Moreover, the device according to the present invention detects not only the tracking phenomenon but also an accident such as an arc discharge short circuit between different poles of a circuit having a similar waveform aspect or an energization accompanied by an arc discharge due to a half-break of the same pole. Available to:

DESCRIPTION OF SYMBOLS 1,1 '... Electric circuit 2 ... Timing detection part 3 ... Current transformer 4 ... Burden resistance 5 ... A / D converter 6 ... First register 7 ... Calculation Part 8 ... Second register 9 ... Determination part 10 ... SCR
DESCRIPTION OF SYMBOLS 11 ... Relay coil 12 ... Alarm contact 13 ... Waveform difference detection part 14 ... Third register 15 ... Determination part 16 ... Conventional detection apparatus 17 ... of this invention Detection device 18 ... Final determination unit

Claims (2)

A tracking current detection device for detecting a tracking current generated in a commercial circuit,
A current detection unit provided in the commercial power circuit for detecting a load current flowing in the commercial power circuit;
An A / D converter that converts the current waveform detected by the current detector into a digital value;
A first register for storing a digital value for a predetermined period output from the A / D converter;
A calculation unit for calculating a waveform rate by a predetermined calculation from the digital value for the predetermined period stored in the first register;
A second register for holding a calculation result for each predetermined period obtained by the calculation unit;
A determination unit that determines whether or not a tracking current is generated by comparing with a predetermined condition based on an operation result held in the second register;
Composed of
A tracking current detection apparatus comprising the waveform rate as a determination element for detecting a tracking current flowing between poles through which a load current flows in the commercial electric circuit.
A tracking current detection device for detecting a tracking current generated in a commercial circuit,
A current detection unit provided in the commercial power circuit for detecting a load current flowing in the commercial power circuit;
An A / D converter that converts the current waveform detected by the current detector into a digital value;
A first register for storing a digital value for a predetermined period output from the A / D converter;
A waveform difference detector that calculates a difference for each period from the digital value for the predetermined period stored in the first register;
A second register for storing difference data for each period obtained by the calculation of the waveform difference detector;
A calculation unit for calculating a waveform rate by a predetermined calculation from the difference data for each period stored in the second register;
A third register for holding a calculation result for each predetermined period obtained by the calculation unit;
A determination unit for determining whether a tracking current is generated by comparing with a predetermined condition based on an operation result held in the third register;
Composed of
A tracking current detection apparatus comprising the waveform rate as a determination element for detecting a tracking current flowing between poles through which a load current flows in the commercial electric circuit.

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