KR20030068524A - Apparatus For Grounding A Power And Apparatus For Alerting An Electric Leakage - Google Patents

Abstract

PURPOSE: A power grounding device and an electric leakage alarming device are provided to correctly judge a ground potential and consume no standby power according to circuit power unit. CONSTITUTION: A power grounding device includes a power line potential attenuator(1) for reducing potential of each of two power lines, a power potential applying unit(2) for applying power potential, obtained by offsetting the reduced potentials of the two power lines each other, to a circuit and, simultaneously, applying the power potential to an object to be grounded, and an earth potential applying unit(3) for applying earth potential to the circuit. The power grounding device further includes a drive signal(5) generator for receiving a detected ground potential judgement signal to generate a drive signal, a display(6) for displaying the ground potential using the signal output from the drive signal generator or the detected ground potential judgement signal, and a circuit power supply(7) for rectifying AC voltage to supply DC voltage required for each of the components.

Description

Power Grounding Device and Earth Leakage Alarm System {Apparatus For Grounding A Power And Apparatus For Alerting An Electric Leakage}

The present invention obtains a ground potential point (ground point) directly from a power supply and realizes grounding such as an electric device, and a predetermined or more leakage from an electrical device grounded at the ground potential point (ground point) obtained by the power grounding device. The present invention relates to a ground fault alarm device that detects an alarm when a current (leakage) occurs.

In other words, the present invention relates to a power grounding device and a ground fault alarm device capable of alarming a ground fault state in the power grounding device. Hereinafter, a conventional technology related to a power grounding device and a ground fault alarm device will be described.

First, as a related art or similar technology related to a power grounding device, a power supply grounding circuit and this grounding circuit registered and registered by the applicant of the present invention [Patent No. 2001-0016185] and the applicant of the present invention. Outlet] (Registration No. 10-0279359-0000), but these are means for acquiring the ground potential point from the power source. Both power lines are connected to both ends of the fixed resistor of the variable resistor, and the neon tube is connected to the sliding terminal. One terminal of the neon tube is connected, and the other terminal of the neon tube is connected to the other terminal of the neon tube while slowly turning the slide to find the point where the neon tube is extinguished as the ground potential point. The ground is formed by applying a ground to a potential body).

However, the above techniques cannot realize sufficient brightness due to the limitation of the amount of current that can flow through the human body through the human body, and it is difficult to discriminate whether the ground potential is bright in a bright place, and in particular, the start voltage of the neon tube is several tens of volts (about 60 volts). Since there is a problem that it is virtually impossible to discriminate whether or not the ground potential is exactly when the magnitude of the potential point acquired through the variable resistor is within the above.

In addition, Figure 5 is a circuit diagram of one embodiment of a conventional grounding device, showing an embodiment of the circuit diagram of the "electronic device grounding device" disclosed in Patent No. 10-0266704. That is, in Patent No. 10-0266704 [Electronic device grounding device], as a ground potential discriminating means, a predetermined comparison circuit (COMP1, COMP2) is configured to reduce and rectify the power supply potential to be discriminated to the input point of the comparison circuit, and to contact the human body to the circuit ground point (power supply terminal) so that any reference reference potential already set in the comparison circuit is established. And a potential comparison with the potential applied through the switching switch and the human body, and when the applied power potential is smaller than the reference potential, the ground potential is determined, and when the applied power potential is large, the non-ground potential is determined. .

However, the above technique has a problem in that an unspecified power potential (ripple) induced through a transformer in the process of transforming an AC power to make a circuit power affects the reference voltage of the comparison circuit, causing a malfunction in comparing potentials. In order to solve the above problem, Patent No. 10-0266704 has a double insulation of a transformer (trans) of the circuit power supply unit, but the problem is caused by the magnetic induction characteristics of the transformer, not the problem of insulation. Therefore, in the above technique, a problem of malfunction still remains, and since a certain amount of standby power is always consumed through the circuit power supply unit, there is a problem in that it is difficult to be practically applied in terms of economy.

In addition, Utility Model Registration No. 0122820 [Electromagnetic Shielding Device], in discriminating whether or not the ground potential of the power supply potential, simply depressurizes the power supply potential and then sequentially switches the power supply potential to be discriminated by using a switching switch. While applying to the (body), a separate portable ground discriminator (field detector) is placed close to the body of the electric device to measure the electric field to discriminate the ground potential.

However, the above technique does not provide a means for discriminating the ground potential on the circuit, and therefore, since a separate ground discriminator (field detector) must be purchased and used at the time of use, a high cost is actually incurred. There is a problem in that it is difficult to use because there is an inconvenience to use to carry a ground discriminator (electric field detector) separately.

In addition, Utility Model Registration No. 20-0205467 [Electromagnetic Blocking Outlet] allows a power line consisting of a ground potential to be discriminated from two power lines without touching the human body to one side of the circuit part. In the contents, a predetermined amplification circuit is formed, and then the collector and emitter are supplied with a circuit power obtained by reducing and rectifying AC power, and an external ground terminal is applied to the base such as a ground wire connected to a building ground terminal or a faucet. By using this as a reference potential, it is possible to compare and discriminate the ground potential. If the power source is not equipped with an external ground terminal (ungrounded power supply without a building ground point), the load residual electromagnetic wave applied from the home appliance is grounded. It is a circuit that is applied to the base of the discriminating amplification element and malfunctions, and is not practical. can do. That is, the above technique is an indefinite mechanism for acquiring a ground potential point (grounding point) in a groundless power source, which is an original purpose of the technique, and also has a problem that the standby power consumption is always generated due to the circuit power supply unit. .

On the other hand, Patent No. 10-0291894 [Automatic Grounding Circuit], Utility Registration No. 20-0205238 [Monitoring Device Automatic Grounding Circuit], Utility Registration No. 1997-0004257 [Electric Device Grounding Device], Patent Registration Prior arts such as No. 0144322 (electromagnetic wave shielding device using automatic grounding circuit) and Patent No. 0120022 (harmful wave blocking device by grounding line detection) also have a clear mechanism of action of the ground potential discriminating means as in the above-described example. It is not presented and it is only the technology which has a problem in practical use.

That is, as is well known, in order to compare and discriminate whether or not the power potential is a ground potential, a comparison reference potential is necessary and the comparison reference potential must be a ground potential, that is, an earth potential (ground potential). As such, they do not have a potential comparison means having the earth potential (earth potential) as a reference potential, or have a low voltage circuit power supply which is lower than an AC power supply voltage even if a potential comparison means is provided, thereby providing a circuit part for discriminating potential. By driving the non-specific power potential from the AC power supply that is relatively higher than the circuit power supply voltage, it is applied to the circuit part for potential discrimination and cancels or mixes with the power potential to be discriminated to prevent the complete potential comparison. There is a problem that occurs.

In addition, the prior art as described above has a problem that the standby power consumption is always generated due to the power consumption inevitably generated in the process of converting and rectifying the AC power source to a low voltage.

Next, the related art related to the ground fault alarm device is Patent No. 10-0241163 [Leakage current alarm device using a reverse phase transformer], but it uses the transformer or the current limiting device to reduce the AC power to a predetermined value or less. There is a problem that a malfunction occurs due to a circuit power supply unit by constructing a circuit power supply by decompressing and rectifying the circuit power supply. In the present invention, the circuit power supply transformer is double insulated to solve the malfunction problem. As such, this is not a complete solution, and in the above technique, the earth leakage detecting means has to be used as a photocoupler as an insulating switching means, and thus there is a problem that the circuit is complicated and the manufacturing cost is high.

In addition, the conventional technology related to the ground fault alarm device in addition to the above-described technology, there is practical registration No. 033418 [Electromagnetically-blocking earth leakage breaker using ground potential], but this is just the same technology of the same person, the same problem still occurs. There is a problem.

The present invention is to solve the above problems, there is no malfunction in the ground potential discrimination, it is possible to detect the potential difference within a few volts more accurate ground potential discrimination, there is no need to convert the AC power source to a low voltage There is no standby power consumption due to the power supply unit, and there is a purpose to provide a power grounding device with less probability of failure and occupied space.

Another object of the present invention, there is no error in the ground potential discrimination, it is possible to discriminate the ground potential more accurately by detecting the potential difference within several volts, and do not need to convert the AC power source to a low voltage at all times to the circuit power supply It is composed by combining with the power grounding device which does not consume any standby power, and by using it as the reference potential by accurately finding the ground potential point in the non-grounded power supply, there is no error in the earth leakage detection, less occupied space, and standby power consumption. The present invention provides a ground fault alarm device.

1 is a circuit diagram of an embodiment of a power grounding apparatus according to the present invention.

2A to 2D are circuit diagrams of a modification of the power supply grounding apparatus according to the present invention.

3 is a circuit diagram of an embodiment of an earth leakage alarm device according to the present invention;

Figure 4 is a circuit diagram of another embodiment of the earth leakage alarm device according to the present invention.

Figure 5 is a circuit diagram of one embodiment of a conventional grounding device.

Power supply grounding apparatus according to the present invention for achieving the above object, in the power supply grounding device, the power supply potential reduction means (1; 3-1) for reducing the potential of the two power supply lines to each predetermined value or less; A power supply potential applying means for applying a power supply potential formed by canceling the potential of each of the two power supply lines applied through the power supply line potential reducing means or the potentials of the two power supply lines to the circuit, and at the same time, applying the same to the grounded object (2) 3-2); A ground potential applying means (3; 3-3) for applying a ground potential (earth potential) to the circuit through a human body touch; Drive signal means (5; 3-8) for receiving the detected ground potential discrimination signal to produce an output drive signal; Display means (6; 3-5, 3-9) for audibly or visually displaying whether or not the ground potential is detected by using the signal output from the driving signal means or the detected ground potential discrimination signal; And circuit power supply means (7; 3-10) for rectifying the AC power to supply the DC power required for the respective means.

In addition, the ground fault alarm device according to the present invention, if there is a leakage current (leakage) of a predetermined value or more from the grounded ground (potential body that needs ground) at the ground potential point obtained by the means of the power grounding device. A ground fault detecting means 3-6 for sensing and detecting a signal; And a ground fault time display means 3-7 for visually displaying a ground fault by a signal applied from the ground fault detection means, wherein the driving signal means 3-8 includes the applied ground potential. The output drive signal is generated not only by the discrimination signal but also by the ground fault detection signal.

Hereinafter, first, the power grounding device according to the present invention will be described with reference to FIGS. 1 and 2A to 2D, and the earth leakage warning device according to the present invention will be described with reference to FIGS. 3 and 4.

1 is a circuit diagram of an embodiment of a power grounding device according to the present invention, Figures 2a to 2d is a circuit diagram of a modification of the power grounding device according to the present invention, the power grounding device shown in Figure 1 modified in various forms The circuit diagram shown is shown.

As shown in FIG. 1, the power supply grounding device according to the present invention includes a power supply potential reducing means (1) for reducing the potentials of two power supply lines to a predetermined value or less, respectively, in order to improve safety in case of circuit short circuit or human body electric shock. Power supply potential applying means (2) for applying to the circuit a power supply potential formed by canceling the potential of each of the two power supply lines applied through the power supply potential reducing means or the potential of the two power supply lines to the circuit, and at the same time Earth potential applying means (3, human body touch plate) for applying the earth potential (earth potential) to the circuit through the human body touch, the earth potential (earth potential) applied through the earth potential applying means (3) A ground potential for discriminating whether or not the ground potential of the power potential is discriminated by comparing the power potential applied through the power potential applying means 2 and detecting the potential difference using the reference potential as the reference potential. Acoustic and visual indication of the ground potential by means of the discrimination means 4, the drive signal means 5 for amplifying a signal applied from the ground potential discrimination means to make a drive signal, and the signal output from the drive signal means And a circuit power supply means (7) for rectifying the display means (6) and the alternating current power supply as they are, to supply the DC power required for the respective means.

The above means will be described in detail as follows.

First, the power line potential reducing means 1 connects predetermined resistors R1 and R2 and capacitors C1 and C2 to the respective power lines in parallel with each other and in series to the power lines A and B. It consists of

In addition, the power potential applying means (2) is composed of a switching switch (S / W) having a two-circuit three-stage switching function, the one-circuit first stage input point and two-stage input point and the two-circuit first stage input point Integrally connected to one end of the resistor R1 and the capacitor C1 of the power line potential damping means 1, and the one-circuit three-stage input point and the two-circuit two-stage input point and the two-circuit three-stage input point A ground potential discrimination means (4) which is integrated and connected to the ends of the other side resistor (R2) and the capacitor (C2) of the power supply potential reduction means (1) and whose one and two circuits have a common point (output point). It is configured by connecting to an emitter (EMITTER) of the amplifying element TR1. On the other hand, the power potential applying means (2) may be composed of a predetermined variable resistor (VR2), in this case, the resistance (R1, R2) and the ends of the capacitors C1 and C2 are respectively connected, and the sliding member is connected to the emitter of the amplifying element TR1 of the ground potential discriminating means 4 described later.

In addition, the ground potential applying means (3) is a ground potential discrimination means amplifying element (TR1) to be described later through the conducting wire and the electric shock prevention resistor (R3) of a conductive plate (PT) of a predetermined size for applying the earth potential by touching the human body It is configured by connecting to BASE.

The ground potential discriminating means 4 is composed of a predetermined amplification element TR1, and the emitter EMITTER has a common point (output point) of the switching switch S / W of the power potential applying means 2. The base BASE is connected to the end of the electric shock prevention resistor R3 of the ground potential applying means 3. On the other hand, when the power potential applying means 2 is constituted by a predetermined variable resistor VR2, the emitter EMITTER of the amplifying element TR1 of the ground potential discriminating means 4 is the power potential applying means ( It is connected to the slider of the variable resistor VR2 of 2), and the base BASE is connected to the edge part of the electric shock prevention resistance R3 of the said earth potential applying means 3. As shown in FIG.

In addition, the driving signal means 5 is composed of a predetermined thyristor (SCR) or triac (TRIAC), the gate (GATE), the collector (COLLECTOR) of the ground potential discrimination means (4) amplification element (TR1) To the cathode (CATHOD, T1), and the negative terminal (-) of the circuit power supply means 7 to be described later, and the variable resistor VR1 for adjusting the sensitivity (amplitude) between the cathode and the gate. ) Is connected.

Further, the display means 6 is provided between the anodes ANODE and T2 of the drive elements SCR and TRIAC of the drive signal means 5 and the anode power terminal + of the circuit power supply means 7 described later. A predetermined buzzer (BZ) and a light emitting device (LED, neon tube, lamp, etc.) are connected through the current limiting resistors R5 and R6, and the buzzer and the light emitting device (LED, neon tube, lamp, etc.) are connected in parallel. Zener diodes ZD1 and ZD2 for protecting the device from overvoltage and electrolytic capacitors C3 and C4 for smoothing the signal applied to the device are connected to each other. That is, in the power grounding device according to the present invention, since the AC power supply voltage is rectified as a voltage size and used as a circuit power supply, a zener diode that protects the device from overvoltage must be provided. As a result, a smoothing capacitor must also be provided for the full operation of the buzzer.

In addition, the circuit power supply means 7 uses a predetermined diode or a predetermined bridge diode BD to full-wave rectify (bridge rectify) the AC power as the voltage size, and the negative terminal (-) of the DC power output terminals. Is connected to the cathode (T1) of the drive signal (SCR, TRIAC) of the drive signal means 5, the anode terminal (+) is connected to the buzzer and the light emitting element connected to the anode (T2) of the drive element have.

On the other hand, the amplifying element TR1, the thyristor SCR, the triac, or the diode (bridge diode) used in the above-described circuit has a breakdown voltage (350 volts or more) higher than the AC power supply voltage. Do it.

In addition, the present invention may be configured by modifying the power supply potential applying means 2 to a variable resistor VR2, as shown in FIG. 2A without departing from the technical spirit thereof.

In addition, the present invention does not depart from the spirit of the present invention, as shown in FIG. 2B, the amplifying element TR1 of the ground potential discriminating means 4 and the driving elements SCR and TRIAC of the driving signal means 5. It can be configured by adding one-stage or multi-stage amplification elements or integrated elements (IC, TR2) having the same function.

In addition, the present invention is not limited to the technical spirit, as shown in Fig. 2c, the drive element of the ground potential discriminating means 4 and the drive signal means 5 can be configured using only the amplification element TR. Can be.

In addition, the present invention does not depart from the technical idea, and as shown in FIG. 2D, the amplification element TR1 of the ground potential discriminating means 4 is eliminated and only high sensitivity driving elements (thyristors and triacs) are used. Can be configured.

On the other hand, reference numeral TNR, which is not described in the above drawings, is an element (varistor) for absorbing a surge voltage, and M is a grounded body.

Hereinafter, the operation method and operation of the power grounding device according to the present invention described above will be described in detail.

First, it will be described on the assumption that one of the two power lines is made of a ground potential and the other one is made of a high potential (high potential).

That is, when AC power is applied to the power input terminals A and B of the circuit diagram shown in the drawing, the power is attenuated by the power line potential attenuation elements R1, R2, C1, and C2 of the power line potential attenuation means 1. The potential is applied to the input point of the switching switch S / W of the power source potential applying means 2, respectively.

At this time, assuming that the switching switch (S / W) is located at the first stage input point and the power potential applied to the input point is a high potential (high potential) instead of the ground potential, the high potential applied to the input point. (High potential) is applied to the emitter of the amplifying element TR1 of the ground potential discrimination means 4 through the output point. At this time, since the base of the device TR1 is open, the bias VIAS is not formed, and thus the device is turned off.

In this case, when the human body comes into contact with the touch plate PT, that is, the base of the amplifying element TR1, the high potential (high potential) applied to the emitter and the potential of the earth applied through the human body (term definition: The term "earth potential" or "earth potential" or "earth potential" is used to facilitate understanding, but a bias is formed by a potential difference between the earth potential or the earth potential. The drive element (thyristor (SCR) or triac (TRIAC)) of the drive, which is not the ground potential by starting the buzzer (BZ) and the light emitting element (LED) of the display means 6 connected to the anode (ANODE). You will be informed. At this time, since the circuit power in which the AC power voltage is full-wave rectified is applied to the cathode and the anode of the driving device SCR or TRIAC by the bridge diode BD of the circuit power supply means 7, the driving device is started as such. The buzzer is activated by the amplified signal, and the amplification element TR1 of the ground potential discrimination means 4 is activated.

At this time, since the zener diode ZD connected in parallel to the buzzer BZ and the light emitting device LED is matched to the voltage of the devices (buzzer, light emitting device), a voltage higher than the voltage of the devices is bypassed and high. It protects devices from direct voltage.

On the other hand, when the selector switch (S / W) is moved to the three-stage input point, the power potential applied to the input point becomes the ground potential (because one of the two power lines is the ground potential). The ground potential discriminating means 4 is applied to the emitter of the amplifying element TR1, but the base of the element TR1 is in an open state so that no bias is formed and the element remains off.

At this time, when the human body comes into contact with the touch plate PT, that is, the base of the amplifying element TR1, the ground potential applied to the emitter EMITTER and the potential of the earth applied through the human body (earth potential) are applied. Since there is no potential difference or very low (the ground potential is the ground potential), no bias is formed so that the amplification element TR1 is still off so that no current flows in the collector COLLECTOR, and thus the driving element SCR and the buzzer connected thereto are connected. (BZ) and the light emitting element (LED) also do not start, indicating the ground potential.

On the other hand, when the switch switch (S / W) is moved to the second stage input point, since the first stage input point and the second stage input point of one circuit are summed up, the same power source as the first stage input point is also applied to the second stage input point. Since the potential is applied, and the two-circuit two-stage input point and the one-circuit three-stage input point are summed together, the power supply potential applied to the one-circuit three-stage input point is also applied to the two-circuit two-stage input point. Since the output points of the one and two circuits (common point) are summed up, the potentials of the two power lines eventually cause the short circuit (offset) to be caused by loads of the elements R1, R2, C1, C2 of the power line potential reducing means 1 as a load. Thus, a potential obtained by dividing the potential between the power lines A and B, that is, a high potential (high potential) instead of the ground potential, is output to the output point, which is an emitter of the amplification element TR1 of the ground potential discrimination means 4. In this case, since the base of the device TR1 is open, the bias VIAS is applied. Do not castle wherein the device maintains the OFF state.

At this time, when the human body comes in contact with the touch plate PT, that is, the base of the amplifying element TR1, the high potential applied to the emitter (high potential) and the potential of the earth applied through the human body (earth potential) The amplification element TR1 is turned on by the potential difference between the amplification element TR1, which activates the driving signal means 5, the driving element SCR, which activates the buzzer BZ and the light emitting element LED connected to the anode. So that it knows that it is not a ground potential.

Therefore, in the case of the power supply, by placing the switching switch S / W in three stages, the ground potential point can be obtained to realize power grounding.

Next, a description will be given in detail of the adjustment method and operation in the power supply (single-phase three-wire power supply) in which both power lines are made of the non-grounding potential.

First, in a single-phase three-wire power supply system in which both power lines are made of ungrounded potential, that is, high potential (hot line), when the switching switch (S / W) is placed in one or three stages, the power applied to the input point. Since the potentials all become high potentials (high potentials), the same as in the case of the high potentials in the single-phase two-wire power supply described above, the description thereof will be omitted, and only the operation in the case where it is placed in the second stage will be described.

That is, when the switching switch (S / W) of the power supply potential applying means (2) is located at the two-stage input point, the one-stage first stage input point and the second-stage input point are summed, so that the second switch input 1 The same power source potential is applied to the stage input point, and the two-circuit two-stage input point and the one-circuit three-stage input point are combined so that the power applied to the two-circuit two-stage input point is also applied to the one-circuit three-stage input point. Since the potential is applied, and the output points of the one and two circuits (common point) are summed up, the potentials of the two power lines eventually reach the elements (resistances R1 and R2 and the capacitor C1 of the power line potential reducing means 1). , C2)) as a load to short-circuit (offset) to output the neutral potential, that is, the ground potential to the output point, which is applied to the emitter of the ground potential discriminating means (4) amplification element TR1, but the base of the element Is open, so no bias is formed and the device is turned off. Keep it.

At this time, when the human body contacts the touch plate PT, that is, the base BASS of the amplifying element TR1, the neutral potential applied to the emitter EMITTER and the ground applied through the human body Since the bias VIAS is not formed because there is no or very low potential difference from the potential (earth potential) of the amplifier, the amplification element TR1 is still off so that no current flows in the collector COLLECTOR, and thus the driving element SCR connected thereto. Also, the buzzer BZ and the light emitting device LED are not activated, indicating that the ground potential is lower.

That is, in the single-phase three-wire power supply, when the switching switch S / W is positioned at the second stage input point, the ground potential point is obtained.

As described above, through the present invention, the ground potential point in the commercial power source (single-phase two-wire power supply and single-phase three-wire power supply) of single-phase AC can be easily obtained using visual and auditory hearing.

In addition, as can be seen from all the above action, in the present invention, the moment when the human body touches the base of the amplification element TR1 of the ground potential discrimination means 4 to discriminate whether or not the ground potential, and the Only when the power supply potential applied to the emitter of the amplifying element TR1 is a high potential other than the ground potential, a bias is formed in the circuit portion, so that a predetermined starting current flows, and no current flows in the circuit portion during standby.

Meanwhile, the configuration of various types of power grounding devices has been described above. Hereinafter, a ground fault alarm device capable of detecting and alarming a ground fault state in the power grounding device mentioned above will be described.

3 is a circuit diagram of an embodiment of the ground fault alarm device according to the present invention. 4 is a circuit diagram of yet another embodiment of the ground fault alarm device according to the present invention, wherein the power supply potential applying means of the ground fault alarm device shown in FIG. 3 is reconfigured using the variable resistor VR2.

That is, as shown in FIG. 3, the ground fault alarm device according to the present invention promotes safety at the time of a circuit short circuit or a human electric shock and mutually cancels the potentials of the two power lines in a power source having no power line consisting of a ground potential among the two power lines. Power supply potential attenuation means 3-1 for reducing the potential of the two power lines below a predetermined value to artificially form a ground potential point, respectively, and each of the two power line applied through the power line potential attenuation means. Is a power supply potential for selectively applying any power supply potential formed by canceling the potential or the potentials of the two power supply lines to a circuit (grounding potential discrimination means) and simultaneously applying it to a grounded body (potential requiring grounding) Means 3-2, earth potential applying means (human touch plate) 3-3, for applying the potential (earth potential) of the earth to the circuit (earth potential discrimination means) through the human body touch; Using the potential of the earth applied through the ground potential applying means as the reference potential, the power potential applied through the power potential applying means is compared, the potential difference is detected, and the ground potential of the power potential is discriminated. Ground potential discrimination means (3-4), ground potential visual indication means (3-5) for visually indicating whether or not the ground potential is in response to a signal applied from the ground potential discrimination means, and obtained by the means An earth leakage detecting means (3-6) for detecting a signal by detecting a leakage current (leakage) of a predetermined level or more from a grounded object (a potential body requiring grounding) as the ground potential point, and applying it from the earth leakage detecting means. From a ground fault time display means (3-7), a ground potential display means or a ground fault time display means for visually displaying whether or not a ground fault is caused by a signal to be made; Drive signal means (3-8) for amplifying the applied signal to produce a drive signal, auditory signal display means (3-9) for generating an audio signal by a signal output from the drive signal means, and AC power It is configured to include a circuit power supply means (3-10) for supplying direct current power directly to the circuit portion by rectifying the voltage as it is.

That is, in the ground fault alarm device according to the present invention shown in FIG. 3, the ground fault detection means 3-6 and the ground fault time display means 3-7 are connected to the power grounding apparatus shown in FIGS. 1 and 2A to 2D. It can be seen that the additional configuration. In addition, in FIG. 3, the same member number is attached | subjected to the element which performs the same function as the power supply grounding apparatus of FIG. 1, and the description is abbreviate | omitted in some cases.

In addition, the structure of each said means is demonstrated in detail as follows.

First, the power line potential reducing means 3-1 is formed by connecting a predetermined resistor and capacitors C1, R1; C2, R2 to each power line in parallel with each other and in series with the power line.

In addition, the power supply potential applying means (3-2) is composed of a switching switch (S / W) having a two-circuit three-stage switching function, the one-circuit first stage input point and two-stage input point and the two-circuit first stage input The points are integrated and connected to one side of the power line potential reducing means and the ends of the capacitors C1 and R1, and the one circuit three stage input point, the two circuit two stage input point and the two circuit three stage input point are integrated. Ground potential discrimination means (3-), which is connected to the other side of the power supply potential reduction means 3-1 and the ends of the capacitors C2 and R2, and whose one and two circuits have in common (output points) are incorporated later. 4) It is comprised by connecting to the emitter of the amplifying element TR1. On the other hand, the power potential applying means (3-2) may be composed of a predetermined variable resistor (VR2) as shown in Figs. 2a and 4, wherein the power line potential attenuation at both ends of the fixed resistor (input point) The resistance of the means and the end of the capacitor are respectively connected, and the sliding member is connected to the emitter of the amplifying element of the ground potential discrimination means described later.

In addition, the ground potential applying means (3-3) is a ground potential discriminating means amplifying element (TR1) to be described later through the conducting wire and the electric shock prevention resistance of the conductive plate (PT) of a predetermined size for applying the earth potential by touching the human body It is configured to connect to the base of.

Further, the ground potential discriminating means 3-4 is constituted by a predetermined amplification element TR1, and the emitter EMITTER of the switching switch S / W of the power potential applying means 3-2. It is connected to a common point (output point), the base BASE is connected to the end of the electric shock prevention resistor R3 of the ground potential applying means 3-3, and a resistance for sensitivity adjustment between the emitter and the base. (R4) or a variable resistor is connected. On the other hand, when the power potential applying means 3-2 is constituted by a predetermined variable resistor VR2 as shown in Fig. 2A or Fig. 4, the amplification element TR1 of the ground potential discriminating means 3-4 is used. The emitter EMITTER is connected to the sliding member of the variable resistor VR2 of the power supply potential applying means 3-2, and its base is the electric shock prevention resistance of the ground potential application means 3-3. It is connected to the end of R3). At this time, between the amplifying element TR1 of the ground potential discriminating means 3-4 and the power supply potential applying means 3-2, a high potential is directly applied to the amplifying element TR1 from the ground to be grounded when a short circuit occurs. The leakage potential reduction resistor R13 for preventing the connection is connected.

The ground potential display means 3-5 connects the light emitting element LED1 to the collector of the amplifying element TR1 of the ground potential discrimination means through a current limiting resistor R12, and ends of the element. Is configured by connecting a reverse voltage preventing diode D1 in the forward direction.

Further, the ground fault detecting means 3-6 is a ground wire which is drawn out from the output point (common terminal) of the power potential applying means switching switch S / W or variable resistor VR2 (of FIG. 2A or FIG. 4). Insert a signal voltage detection resistor (R10) for detecting a predetermined signal voltage by the leakage current into the furnace, and connect the emitter of the predetermined amplification element (TR3) to one side of the connection point of the resistance, and the other The base of the amplifying element is connected via a current limiting resistor R7 and a rectifying diode D2, and between the emitter and the base of the amplifying element TR3 is a resistor R8 for adjusting sensitivity (amplitude) or The variable resistor is connected. At this time, the emitter of the amplifying element TR3 of the ground fault detecting means is connected to the outside of the connection point (ground member M).

Further, the ground fault timing display means 3-7 connects a predetermined light emitting element LED2 to the collector of the ground fault detection means amplification element TR3 through a current limiting resistor R9, and at the end thereof a reverse voltage. The diode D3 for preventing the damage is connected.

In addition, the driving signal means (3-8) is composed of a predetermined thyristor (SCR) or triac or amplification element, the gate (base) of the reverse voltage preventing diode (D1) of the ground potential display means and the short circuit The end of the reverse voltage preventing diode D2 of the time display means is commonly connected, and the cathode (emitter) is connected to the negative power terminal of the circuit power supply means 3-10 described later, and the cathode (emitter) A resistor or variable resistor VR1 for preventing leakage current and adjusting sensitivity (amplitude) is inserted between the gate and the base.

In addition, the auditory signal display means 3-9 is provided between a resistor R5 connected to the anode (collector) of the drive element SCR of the drive signal means, and the anode power terminal of the circuit power supply means described later. A predetermined buzzer BZ is connected, and a zener diode ZD1 for protecting the device from overvoltage in parallel with the buzzer and an electrolytic capacitor C3 for smoothing a signal applied to the device are configured.

In addition, the circuit power supply means 3-10 uses a predetermined bridge diode BD to full-wave rectify AC power as it is, and the negative terminal of the DC power output terminals is the drive signal means driving element (SCR). The anode terminal is connected to the buzzer connected to the collector (anode) of the drive element SCR through the current limiting resistor R11.

On the other hand, in the above configuration, the current flowing through the circuit at the time of ground potential detection and the current flowing through the circuit at the time of leakage current detection are combined with each other to prevent ground potential discrimination error or short circuit detection error. The emitter of the amplifying element TR1 of the ground potential discriminating means 3-4 is located inside the connection point of the signal voltage detecting resistor R10 of the ground fault detecting means 3-6 (switch switch SW1 output terminal, variable resistor ( VR2), and the emitter of the amplifying element TR3 of the ground fault detecting means 3-6 is connected to its outer side (ground member M).

Further, the amplifier, thyristor, or triac used in the circuit section also has a breakdown voltage (350 volts or more) which is sufficiently higher than the AC power supply voltage.

In addition, the earth leakage alarm device according to the present invention as shown in FIG. 3 does not depart from its technical concept, and as shown through FIG. 4, the power supply potential applying means 3-2 includes a variable resistor VR2. It can also be configured to transform.

Although not illustrated in the drawings, the ground fault detecting means 3-6 and the ground fault timing display means 3-7 are also included in the power grounding apparatus shown in FIGS. 2B and 2C by using the above-described principle. can do.

That is, as illustrated in FIG. 2B, one or more stages of amplification elements between the amplifying element TR1 of the ground potential discriminating means 4 and the driving elements SCR and TRIAC of the driving signal means 5 or the like. The ground fault alarm device can be configured by adding the ground fault detection means 3-6 and the ground fault time display means 3-7 to a power supply grounding device configured by adding integrated devices IC and TR2 having a function equivalent to. have.

In addition, as shown in Fig. 2C, the grounding current discriminating means 4 and the driving device of the driving signal means 5 are connected to the power grounding device configured using only the amplifying elements TR1 and TR2. 3-6) and a ground fault time display means 3-7 can be added to configure a ground fault alarm device.

On the other hand, TNR denotes an element (varistor) for absorbing surge voltage, and M denotes an earth to be grounded (grounding unit (body) of the appliance, grounding terminal of the outlet).

Hereinafter, the ground potential point display action among the actions of the earth leakage alarm device according to the present invention shown in FIGS. 3 and 4 will be described next.

First, the ground potential point display operation will be described. First, it is assumed that the power source is a single-phase two-wire power supply in which one of the two power lines is the ground potential and the other is the high potential (high potential). do.

That is, when AC power is applied to the power input terminals A and B of the circuit diagrams shown in Figs. 3 and 4, the power potential attenuated through the power line potential reducing means 3-1 is applied to the power potential applying means (3- It is applied to the input point of the changeover switch of 2).

At this time, assuming that the switching switch is located at the first stage input point and the applied power potential is a high potential (high potential) rather than a ground potential, the high potential (high potential) applied to the input point is grounded through the output point. The potential discriminating means 3-4 is applied to the emitter of the amplifying element. At this time, since the base of the device is in an open state, no bias is formed, and thus the device remains off.

At this time, when the human body comes into contact with the touch point of the amplification element, that is, the base, the amplification is performed by the potential difference between the high potential (high potential) applied to the emitter and the earth potential (earth potential) applied through the human body. The device is turned on, and the light emitting device connected to the collector is turned on to indicate that it is not the ground potential. The signal also activates the driving element (SCR or TRIAC) of the driving signal means 3-8 through a current limiting resistor and a reverse voltage preventing diode, which is connected to the anode (collector) of the driving element (SCR). It will make a sound to indicate that it is not a ground potential. At this time, the cathode (emitter) and the anode (collector) of the driving element are supplied via a buzzer, which is a direct current power supply of full-wave rectified AC power voltage by the bridge diode of the circuit power supply means (3-10). As described above, the buzzer is started with the amplified signal, and the amplification device of the ground potential discriminating means 3-4 is started.

On the other hand, in the above operation, the thyristor or the triac is more advantageous than the amplifying device in the driving device, and the amplifying device determines the output potential in proportion to the input potential so that the buzzer and the light emitting device are used whenever the input potential is 110 or 220 volts. The thyristor or triac, once the conduction is started, flows the current until it is saturated regardless of the magnitude of the input potential, so the input potential is 110 volts or 220 volts. It is because the characteristic which drives a is expressed.

At this time, the zener diode is adapted to the voltage of the buzzer to protect the buzzer from a high DC voltage.

On the other hand, if the switch is positioned at the three-stage input point by moving the switch, the ground potential is applied to the input point (since one of the two power lines consists of the ground potential), and the ground potential is grounded through the output point. The discriminating means (3-4) is applied to the emitter of the amplifying device, and since the base of the device is open, no bias is formed so that the device remains off.

At this time, when the human body is in contact with the touch point, that is, the base of the amplifying element, the potential difference between the ground potential applied to the emitter and the earth potential (low potential) applied through the human body is low or low (earth potential and earth The potentials are different for the sake of easy understanding, but they are actually the same potential.) Since no bias is formed, the amplification element is still off and does not flow current to the collector, so that the light emitting element connected thereto is turned off to indicate that it is the ground potential. Done. In addition, the driving device and the buzzer do not start below to indicate the ground potential.

On the other hand, when the changeover switch is positioned at the second stage input point, since the first stage first stage input point and the second stage input point are summed, the same power potential is applied to the second stage input point, and the two circuits 2 Since the single input point and the three-stage input point of one circuit are added together, the potential applied to the three-stage input point is also applied to the two-circuit and two-stage input points, and the one- and two-circuit output points (common point) are combined. Eventually, the potentials of the two power lines are short-circuited (offset) with the power potential reducing means 3-1 element as a load, and output a potential, that is, a high potential (high potential), which is equalized by dividing the potential between the power lines to the output point. The potential discriminating means 4 is applied to the emitter of the amplifying element, wherein the base of the element is open and no bias is formed so that the element is kept off.

At this time, when the human body is in contact with the touch point, that is, the base of the amplification element, the potential difference between the high potential (high potential) applied to the emitter and the earth potential (earth potential = ground potential) applied through the human body. The amplification element is turned on to light the light emitting element connected to the collector to indicate that it is not the ground potential. In addition, the signal activates the driving element of the driving signal means 3-8 through the current limiting resistor and the reverse voltage preventing diode, which activates the buzzer connected to the collector and makes a sound to indicate that it is not the ground potential. .

Therefore, in the case of the power supply, by placing the switching switch in three stages, the ground potential point can be obtained to realize power grounding.

On the other hand, in the following, it will be described the adjustment method and operation of the power supply (single-phase three-wire power supply) in which both power lines are composed of a non-grounding potential (high potential).

In single-phase three-wire power supply where both power lines are non-grounded, that is, high potential, when the switching switch is placed in one or three stages, the power potential applied to the input point is all high-potential. Since it is the same as the case of the high potential of, the description thereof will be omitted and the operation of the case where it is placed in the second stage will be described.

That is, when the switching switch of the power supply potential applying means 3-2 is placed in the second stage, the potentials of the two power supply lines are short-circuited (offset) by using the resistor and the capacitor of the power supply power reduction means 3-1 as the load. A potential point is generated, which is applied to the emitter of the ground potential discriminating means 3-4. At this time, since the base of the device is open, no bias is formed and the device remains off.

At this time, when the human body is in contact with the touch point, that is, the base of the amplifying element, the potential difference between the ground potential applied to the emitter and the earth potential (low potential) applied through the human body is low or low (earth potential and earth The potentials are different for the sake of easy understanding, but they are actually the same potential.) Since no bias is formed, the amplification element is still off and does not flow current to the collector, so that the light emitting element connected thereto is turned off to indicate that it is the ground potential. Done. In addition, the driving device and the buzzer do not start below to indicate the ground potential.

That is, in the single-phase three-wire power supply, when the switching switch of the power potential applying means 3-2 is positioned at the second stage input point, the ground potential point is obtained.

Next, during the operation of the ground fault alarm device according to the present invention will be described for the ground fault alarm action.

That is, when there is a potential leakage (leakage) of high potential on the grounded object, current flows from the grounded ground to the ground potential point due to the potential difference, which generates a voltage drop voltage to the ground fault detection resistor R10, which is a ground fault detection unit. It acts as a bias voltage of the amplifying element TR3 to start the element, which turns on the light emitting element LED2 connected to the collector to indicate a short circuit. Further, the signal is applied to the drive element SCR of the drive signal means 3-8 through the reverse voltage prevention diode D3 to start the drive element, and the buzzer BZ connected to the anode is also started to sound. It causes a short circuit.

That is, the ground potential point in the commercial power supply of single-phase AC through the ground fault alarm device according to the present invention can be easily obtained by using visual and auditory, and when a ground fault occurs to the ground potential point, it is visually and audibly It can be easily recognized.

In addition, as can be seen from all the above actions, the earth leakage alarm device according to the present invention is applied to the emitter of the amplifier and the moment when the human body is touched to the base of the amplifier of the ground potential discrimination means to discriminate the ground potential. Only when the power supply potential is a high potential other than the ground potential and when a short circuit is detected, a bias is formed in the circuit part, so that a predetermined current flows, and no current flows in the circuit part during standby.

In addition, in the ground fault alarm device according to the present invention, since the phases of the current flowing through the circuit when the ground potential is detected and the current flowing through the circuit when the leakage current is sensed are mutually opposite, the two currents are combined with each other to generate a ground potential discrimination error. It does not cause a short circuit detection error.

The present invention is not limited to the embodiments described above, and various modifications and changes can be made by those skilled in the art, which are included in the spirit and scope of the present invention as defined in the appended claims.

Power supply grounding device according to the present invention as described above, there is no error in ground potential discrimination, it is possible to find the ground potential point more accurately by discriminating the potential difference within a few volts, there is no power consumption at all times due to the circuit part Excellent effect.

In addition, the power supply grounding apparatus according to the present invention has an excellent effect that the circuit is simple, the manufacturing cost is low, the failure is small and the occupied space is small.

In addition, as an indirect effect of the power supply grounding apparatus according to the present invention, when the present invention is incorporated into an outlet, an electric mat, a home appliance, or the like, since the ground potential point can be obtained even in a 2-pole non-grounding power supply, the grounding is the same as that of the earth ground. In addition, by grounding (absorbing) the electric field (ripple potential) radiated from home appliances, etc., a stable operation of the circuit part is ensured, and the life of the electric device can be extended and electromagnetic waves (electric field) can be removed.

In addition, the ground fault alarm device according to the present invention is configured to share a portion other than the ground fault detection means and the ground fault time display means, that is, a buzzer, etc. having a relatively high unit cost, with the power grounding device, thereby simplifying the circuit and manufacturing cost. It is extremely inexpensive and has an excellent effect of superior competitiveness.

In addition, the ground fault alarm device according to the present invention has an indirect effect of preventing an electric shock by generating an alarm so that a user can recognize the ground fault.

Claims (17)

In the power grounding device, Power supply potential reduction means (1; 3-1) for reducing the potential of the two power supply lines to a predetermined value or less, respectively; A power supply potential applying means for applying a power supply potential formed by canceling the potential of each of the two power supply lines applied through the power supply line potential reducing means or the potentials of the two power supply lines to the circuit, and at the same time, applying the same to the grounded object (2) 3-2); A ground potential applying means (3; 3-3) for applying a ground potential (earth potential) to the circuit through a human body touch; Drive signal means (5; 3-8) for receiving the detected ground potential discrimination signal to produce an output drive signal; Display means (6; 3-5, 3-9) for audibly or visually displaying whether or not the ground potential is detected by using the signal output from the driving signal means or the detected ground potential discrimination signal; And Circuit power supply means (7; 3-10) for rectifying AC power to supply DC power required for each of the means Power grounding device comprising a. The method of claim 1, Using the potential of the earth applied through the earth potential applying means (earth potential) as a reference potential, the power potential applied through the power potential applying means 2 is compared, the potential difference is detected, and the ground potential of the power potential is applied. Ground potential discrimination means (4; 3-4) for discriminating whether or not, And the drive signal means (5; 3-8) receives a ground potential discrimination signal from the ground potential discrimination means (4; 3-4). The method of claim 2, The ground potential discriminating means (4; 3-4) is composed of one stage of amplifying element (TR1), the power source applying means (2; 3-2) is connected to the emitter of the amplifying element (TR1) The ground potential applying means (3; 3-3) is connected to the base, and the sensitivity adjusting resistor (R4) is connected between the emitter and the base, and the drive signal means (5) or the display is connected to the collector. A power grounding device, characterized in that the means (3-5) are connected. The method of claim 2, The ground potential discriminating means (4; 3-4) is composed of a plurality of stages of amplification elements (TR1, TR2) and the second amplification element (TR2), the collector and drive signal means of the first amplification element (TR1) ( 5) or between the first amplifying element TR1 and the display means (3-5). The method of claim 1, The driving signal means (5; 3-8) is composed of a thyristor (SCR) or triac (TRIAC), the detected ground potential discrimination signal is applied to the gate (GATE) of the device, the cathode (CATHOD) The negative terminal (-) of the circuit power supply means (7; 3-10) is connected, and the variable resistor (VR1) for adjusting the sensitivity (amplitude) is connected between the cathode and the gate, and the anode (ANODE) is connected. ) Is connected to the display means (6; 3-9). The method of claim 1, The driving signal means (5; 3-8) is composed of an amplifying element (TR2), the detected ground potential discrimination signal is applied to the base of the amplifying element (TR2), the circuit power supply means to the emitter A negative terminal (-) of (7; 3-10) is connected, and a variable resistor VR1 for adjusting sensitivity (amplification degree) is connected between the base and the emitter, and the display means 6 is connected to the collector; Power supply grounding device, characterized in that 3-9) is connected. The method of claim 1, The power supply potential applying means (2; 3-2) is composed of a switching switch (S / W) having a two-circuit three-stage switching function, and one circuit first stage input point and two of the switching switch (S / W). The single input point and the two-circuit one-stage input point are integrally connected to one end of the power line potential reducing means (1; 3-1) and the end of the resistor (R1) and the condenser (C1), and the switching switch (S / W). 1 circuit 3-stage input point and 2-circuit 2-stage input point and 2-circuit 3-stage input point are integrated and connected to the ends of the other side resistor R2 and the capacitor C2 of the power line potential reducing means 1. And a common point (output point) of the one circuit and the two circuits are integrally connected to the driving signal means. The method of claim 2, The power supply potential applying means (2; 3-2) is composed of a switching switch (S / W) having a two-circuit three-stage switching function, and one circuit first stage input point and two of the switching switch (S / W). The single input point and the two-circuit one-stage input point are integrally connected to one end of the power line potential reducing means (1; 3-1) and the end of the resistor (R1) and the condenser (C1), and the changeover switch (S / W). 1 circuit 3-stage input point and 2-circuit 2-stage input point and 2-circuit 3-stage input point are integrated and connected to the ends of the other side resistor R2 and the capacitor C2 of the power line potential reducing means 1. And a common point (output point) of the one circuit and the two circuits are integrally connected to an emitter of the amplifying element TR1 of the ground potential discriminating means (4; 3-4). The method of claim 1, The power supply potential applying means (2; 3-2) is constituted by a predetermined variable resistor (VR2), the resistance (R1) of the power supply potential reduction means (1; 3-1) at both ends of the resistor (input point); And R2) and ends of the condenser (C1, C2), respectively, and the sliding member is connected to the drive signal means. The method of claim 2, The power supply potential applying means (2; 3-2) is constituted by a predetermined variable resistor (VR2), the resistance (R1) of the power supply potential reduction means (1; 3-1) at both ends of the resistor (input point); , R2 and the ends of the capacitors C1 and C2 are connected, respectively, and the sliding means is connected to the emitter of the amplifying element T1 of the ground potential discriminating means 4 and 3-4. Device. The method of claim 1, The display means 6, A predetermined buzzer BZ and a light emitting element are connected through the current limiting resistors R5 and R6, and the buzzer and the light emitting element are applied to the circuit power supply by rectifying the AC power supply voltage as the voltage size. And a zener diode (ZD1, ZD2) and a smoothing electrolytic capacitor (C3, C4) for protecting the device from overvoltages in parallel. An earth leakage warning device comprising the power supply grounding device of any one of claims 1 to 11, A ground fault detecting means for detecting a signal by detecting a leakage current (leakage) of a predetermined value or more from a grounded object (potential that needs grounding) as a ground potential point obtained by means of the power grounding device ( 3-6); And It further comprises a ground fault time display means (3-7) for visually displaying whether or not the ground fault by the signal applied from the ground fault detection means, And the drive signal means (3-8) generates a drive signal for output not only by the applied ground potential discrimination signal but also by the ground fault detection signal. The method of claim 12, The display means is divided into a ground potential time display means (3-5) and an auditory signal display means (3-9), The ground potential display means (3-5) is connected to the light emitting device through the current limiting resistor (R12) to which the detected ground potential discrimination signal is applied, and for preventing reverse voltage in the forward direction to the end of the resistor (R12) Earth leakage alarm device characterized in that the diode is connected. The method of claim 12, The earth leakage detecting means 3-6, A signal voltage detection resistor R10 for detecting a predetermined signal voltage by a leakage current is inserted into the ground line drawn out from the output point (common terminal) of the power supply potential applying means 2; An emitter of a predetermined amplification element TR3 is connected to one side of the connection point of the resistor, and a base of the amplifying element TR3 is connected to the other side connection point through a current limiting resistor and a rectifying diode. A resistor (R8) or a variable resistor for adjusting sensitivity (amplitude) is connected between the emitter and the base, and the emitter of the amplifying element TR3 is connected to the outside of the connection point (ground) (M). An earth leakage alarm device characterized in that. The method of claim 14, The current which flows in the circuit at the time of the ground potential discrimination by the ground potential discriminating means 3-4 and the current flowing in the circuit at the time of detecting the leakage current by the ground fault detecting means 3-6 are combined with each other and the ground potential To prevent discrimination or short circuit detection errors, The emitter of the amplifying element TR1 constituting the ground potential discriminating means 3-4 is inside the connection point of the signal voltage detecting resistor R10 of the ground fault detecting means 3-6 (changeover switch output terminal, variable resistor). And a base of the amplifying element TR1 are connected to a ground potential applying means 3-3, and a collector of the amplifying element TR1 is connected to the ground potential time display means 3-5. Connected, The emitter of the amplifying element TR3 constituting the earth leakage detecting means 3-6 is connected to the outside of the connection point (grounding object M) of the signal voltage detecting resistor R10, and is connected to the amplifying element TR3. The inside of the connection point of the base (switch switch SW output terminal, variable resistor VR2 sliding) is connected to the ground potential discriminating means 3-4, and the collector of the amplifying element TR3 is the earth leakage time display means. A ground fault alarm device connected to (3-7). The method of claim 12, The earth leakage time display means 3-7, A predetermined light emitting element LED2 is connected to the collector of the amplifying element TR3 of the ground fault detecting means 3-6 through a current limiting resistor R9, and a diode for preventing a reverse voltage at the end of the resistor ( D3) is connected to the earth leakage alarm device. The method of claim 12, The ground potential discriminating means (3-4), It consists of a predetermined amplification element TR1, and between the amplification element TR1 of the ground potential discriminating means 3-4 and the power supply potential applying means 3-2, the high potential is amplified from the ground to be grounded when the earth leakage occurs. A ground fault alarm device, characterized in that a ground potential reduction resistor (R13) for preventing direct application to the element (TR1) is connected.