JP6062976B2 - Ground connection failure detection device and ground connection failure detection method - Google Patents

Description

  In the present invention, the device under test (DUT) and the ground of the measuring device that performs various measurements of the device under test are commonly grounded, and whether the device under test and / or the device side is properly grounded. The present invention relates to a ground connection failure detection device and a ground connection failure detection method.

  In Patent Document 1 below, in order to prevent an unexpected situation from occurring due to poor grounding, the grounding state of the electrical equipment is always monitored, and when the grounding fault is recognized, the load on the electrical equipment is automatically applied. A grounding failure detection circuit that stops power feeding is disclosed. To explain further, the ground failure detection circuit of Patent Document 1 connects two power lines of commercial AC power supply wired in an electrical device to the ground terminal for grounding wire connection of the electrical device through a small capacitor, respectively. , A current sensor that detects the leakage current flowing from the power line to the ground terminal, an amplifier that amplifies the signal of the current sensor, and a normally closed relay contact that cuts off the power supply to the load is provided on the power line. The normally closed relay contact is opened in the following cases.

Japanese Patent Laid-Open No. 08-163776

  However, the above-described ground failure detection circuit of Patent Document 1 is provided in an electric device using a commercial power source and controls power supply to a load depending on whether the ground terminal of the ground failure circuit itself is grounded. However, it does not correspond to the detection of poor ground connection in a configuration in which the object to be measured is connected to the measuring instrument and the ground is commonly grounded, and various measurements of the object to be measured are performed by the measuring instrument. The ground failure detection circuit of Patent Document 1 needs to intentionally flow a leakage current, and when the ground terminal is not grounded, power supply to the load is cut off. For this reason, there was a time loss such as waiting time for restarting the load and waiting for stabilization time. Moreover, in the ground failure detection circuit of Patent Document 1, if the software is operating when the power supply to the load is cut off, there is a risk of data loss or data corruption.

  By the way, the leakage current value is regulated by a safety standard such as IEC standard or PSE (Electrical Appliance and Material Safety Law). For example, an object 2 to be measured is used for indoor use or outdoor use, large equipment or small equipment. For example, it is set to about several mA according to the environment or category used. In addition, when the measuring instrument and the object to be measured are connected in a state where the AC power supply ground is defective, there is a case where a large potential difference occurs between the two and the possibility that the measuring instrument and the object to be measured are damaged by ESD increases. In recent years, the ESD (Electro-Static-Discharge) resistance of semiconductors has decreased with the progress of semiconductor processes, and ground connection between a measuring instrument and a device under test has become an important issue. In addition, the number of cases in which the power source is not connected to the ground by a two-pole AC adapter or the like is increasing. For this reason, when performing various measurements of the measurement object with the measuring instrument, when the measurement object and the measurement instrument ground are connected to a common ground, a configuration that can reliably detect a ground connection failure on the measurement object side or the measurement instrument side, A method was desired.

  Therefore, the present invention has been made in view of the above-described problems, and a ground connection failure detection device and a ground connection that can reliably detect a ground connection failure without flowing an intentional leak current as in the prior art. The object is to provide a defect detection method.

In order to achieve the above object, a ground connection failure detection device according to claim 1 of the present invention comprises a device under test 2 and a measuring instrument 3 for performing various measurements of the device under test. In the ground connection failure detection device 1 for detecting whether or not the object to be measured and / or the measuring instrument side is properly grounded by connecting a ground between the object and the measuring instrument ,
The object to be measured is
A power supply device 4 with a built-in or external noise filter 4a;
A two-pole or three-pole AC inlet 5 connected to a power supply device included in the object to be measured ;
The measuring instrument is
A power supply device 6 with a built-in or external noise filter 6a;
A three-pole AC inlet 7 connected to a power supply device included in the measuring instrument ;
A current transformer 8 connected to the ground connection line 3a which is housing ground and connects between the G terminal of the AC inlet to the instrument power supply device provided with the instrument comprises,
A leakage current detector 9 for detecting an AC leakage current flowing in the ground connection line ;
A signal determination processing unit that determines whether or not the leakage current detected by the leakage current detection unit is within a normal range, and outputs an abnormal signal when the leakage current deviates from the normal range; It is characterized by that.

The ground connection failure detection device according to claim 2 is the ground connection failure detection device according to claim 1,
When the signal discrimination processing unit 10 outputs the abnormal signal, the signal discrimination processing unit 10 is provided with an output unit 12 that outputs that fact by display or voice.

The ground connection failure detection device according to claim 3 is the ground connection failure detection device according to claim 1 or 2,
The storage unit 11 stores at least a log when the leakage current deviates from the normal range.

According to a fourth aspect of the present invention, there is provided a ground connection failure detection method using a ground connection failure detection apparatus 1 comprising a device under test 2 and a measuring instrument 3 for performing various measurements of the device under test. It includes a noise filter 4a is built in or externally connected power supply 4, wherein possess an AC inlet 5 of two-pole or three-pole connected to a power supply device DUT comprises said measuring instrument, noise filter 6a and the power supply device 6 that is internal or external is, the the AC inlet 7 of the connected 3-pole power supply instrument comprising, G terminal of the AC inlet to the instrument power supply device provided with the instrument comprises connects between the possess a current transformer 8 connected to the ground connection line 3a which is a housing ground, ground is common ground and connects between the said measuring device 3 and the object to be measured, The measured object side and / Or the ground connection failure detection method the measuring instrument side to detect whether it is properly grounded connection,
Detecting an AC leakage current flowing in the ground connection line ;
Determining whether or not the leakage current is within a normal range, and outputting an abnormal signal when the leakage current deviates from the normal range.

The ground connection failure detection method according to claim 5 is the ground connection failure detection method according to claim 4,
When outputting the abnormal signal, it includes a step of outputting the fact by display or sound.

The ground connection failure detection method according to claim 6 is the ground connection failure detection method according to claim 4 or 5,
The storage unit 11 includes a step of storing at least a log when the leakage current deviates from the normal range.

  According to the present invention, the ground is commonly connected by connecting the object to be measured and the measuring instrument, and the leakage current flowing in the current transformer connected between the power supply device in the measuring instrument and the AC inlet is detected. It is determined whether or not the detected leakage current is within the normal range, and an abnormal signal is output when the leakage current deviates from the normal range. A connection failure can be reliably detected.

  In addition, when the leakage current deviates from the normal range, the fact that the leakage current is abnormal is output by display or sound, so that the user can be surely notified by display or sound that a ground connection failure has occurred. it can.

  Furthermore, since a series of logs from when the leakage current is detected to when it is determined whether or not the leakage current is within the normal range is stored, the analysis result of the log can be used for improvement proposals related to poor ground connection.

1 is a schematic configuration diagram of a ground connection failure detection device according to the present invention. It is a figure which shows an example of the noise filter incorporated in or attached to each power supply device of a measuring device and a to-be-measured object in the earth connection failure detection apparatus which concerns on this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to FIGS. 1 and 2 of the accompanying drawings.

  As shown in FIG. 1, the ground connection failure detection device 1 includes a device under test 2 and a measuring instrument 3 that performs various measurements of the device under test 2. For example, the object to be measured 2 and the measuring instrument 3 are grounded in common by connecting the casings to each other with the outer surface of the coaxial cable as the measurement earth E. The ground connection failure detection device 1 in this example has a function of detecting whether or not the device under test 2 side and / or the measuring device 3 side is correctly grounded. Hereinafter, the configurations of the DUT 2 and the measuring instrument 3 will be described.

  The device under test 2 is a measurement object on which various measurements are performed by the measuring instrument 3, and includes a power supply device 4 and an AC inlet 5.

  The power supply device 4 is a switching power supply that supplies power necessary for driving the DUT 2, and includes a noise filter 4a. The noise filter 4 a is configured by a generally known single-phase one-stage filter, and prevents conduction noise that enters and flows out of the power supply device 4. As shown in FIG. 2, in the noise filter 4a used in this example, terminals (lines) 4a1 and 4a2 and terminals (loads) 4a3 and 4a4 are connected via a choke coil L1. A resistor R1 and a capacitor C1 are connected in parallel between the terminals 4a1 and 4a2 and the choke coil L1. Further, a series circuit of capacitors C3 and C4 having the same capacity as the capacitor C2 and the resistor R2 is connected in parallel between the choke coil L1 and the terminals 4a3 and 4a4. The midpoint between the capacitors C3 and C4 is connected to the ground via the housing of the noise filter 4a.

  The AC inlet 5 is connected to the power supply device 4 through a ground connection line 2a and a signal line 2b, and a two-pole type inlet or a three-pole type inlet is used. The two-pole type inlet has an L (live) terminal and an N (neutral) terminal as AC input terminals. In addition to the L terminal and the N terminal, the three-pole type inlet includes a G (ground) terminal. In the AC inlet 5, the ground connection line 2a is grounded to the housing of the DUT 2, the L terminal is connected to the non-ground side of the commercial power supply, and the N terminal is connected to the ground side. When the AC inlet 5 is a three-pole type inlet, the G terminal of the power source is connected to the ground to prevent electric shock and noise.

  The measuring instrument 3 includes a power supply device 6, a three-pole AC inlet 7, a current transformer (CT) 8, a leakage current detection unit 9, a signal discrimination processing unit 10, a storage unit 11, and an output unit 12.

  The power supply device 6 is a switching power supply that supplies power necessary for driving each unit of the measuring instrument 3, and includes a noise filter 6a. Similar to the noise filter 4 a of the DUT 2, the noise filter 6 a is composed of a single-phase single-stage filter having the circuit configuration shown in FIG. 2, and prevents conduction noise that enters and flows out of the power supply device 6.

  The AC inlet 7 is connected to the power supply device 6 through a ground connection line 3a and a signal line 3b, and has three poles including an L (live) terminal, an N (neutral) terminal, and a G (ground) terminal as AC input terminals of the power supply. Consists of type inlets. In the AC inlet 7, the ground connection line 3 a is grounded to the housing of the measuring instrument 3, and the L terminal is connected to the non-ground side of the commercial power source, like the three-pole type AC inlet 5 of the DUT 2. The terminal is connected to the ground side, and the G terminal is connected to ground.

  The current transformer 8 is connected between the G terminal of the AC inlet 7 and the power supply device 6 and connected to the ground connection line 3a that is grounded in the housing, and the leakage current detection unit detects the AC leakage current flowing through the ground connection line 3a. Output to 9. Here, the current transformer 8 is used to ensure compliance with the resistance value regulation of the protective ground terminal and high voltage insulation performance.

  The leakage current detection unit 9 includes a current detection unit 9a, an IV conversion amplification unit 9b, and a rectifier circuit 9c in order to detect an AC leakage current flowing through the ground connection line 3a.

  The current detector 9 a detects an AC leakage current flowing through the ground connection line 3 a via the current transformer 8.

  The IV conversion amplification unit 9b converts and amplifies the AC leakage current detected by the current detection unit 9a into a voltage value.

  The rectifier circuit 9c rectifies the voltage value of the leakage current converted and amplified by the IV conversion amplification unit 9b, and outputs the rectified voltage value to the signal discrimination processing unit 10 as a DC leakage voltage signal.

  The signal discrimination processing unit 10 includes a voltage comparator 10a and a control unit 10b in order to process a DC leakage voltage signal input from the rectifier circuit 9c of the leakage current detection unit 9.

  The voltage comparator 10a is composed of, for example, a window comparator, and an upper limit threshold voltage and a lower limit threshold voltage are set in advance in consideration of errors due to ground resistance, noise, and the like. In this example, the range between the upper limit threshold voltage and the lower limit threshold voltage is set as a specified (steady) normal range (expected value). If the voltage value of the DC leakage voltage signal from the rectifier circuit 9c is within the normal range, the voltage comparator 10a outputs a leakage current normal detection signal indicating that the leakage current is normal. In addition, if the voltage value of the DC leakage voltage signal from the rectifier circuit 9c deviates from the normal range, the voltage comparator 10a outputs a leakage current abnormality detection signal indicating that the leakage current is abnormal. The voltage comparator 10a may output a leakage current abnormality detection signal when the voltage value of the leakage voltage signal continuously deviates from the normal range for a set time (for example, around 1 second). Thereby, the abnormality detection of leakage current can be performed reliably.

  When the leakage current normal detection signal is input from the voltage comparator 10a, the control unit 10b determines that the leakage current is normal and is properly grounded. Further, when the leakage current abnormality detection signal is input from the voltage comparator 10a, the control unit 10b determines that the leakage current is abnormal and the earth connection is incomplete (earth connection failure), and this is indicated. The output unit 12 is controlled to notify the user. Furthermore, the control unit 10b stores a series of logs in the storage unit 11 from when the leakage current detection unit 9 detects the leakage current until it is determined whether the voltage value of the leakage current is within the normal range.

  Under the control of the control unit 10b, the storage unit 11 stores a series of logs from when the leakage current detection unit 9 detects the leakage current until it is determined whether or not the voltage value of the leakage current is within the normal range.

  The output unit 12 gives a warning to the user that the leakage current is abnormal and the ground connection is incomplete. For example, the output unit 12 outputs a sound such as a display unit such as a liquid crystal display or a display lamp or a speaker. It consists of parts. The display unit as the output unit 12 displays a message indicating that the ground connection is incomplete on the screen of the liquid crystal display or indicates that the ground connection is incomplete under the control of the control unit 10b. Turn on the indicator lamp. Moreover, the audio | voice output part as the output part 12 outputs an audio | voice or an alarm sound from a speaker that the earth connection is incomplete by control of the control part 10b.

  In this example, the noise filters 4a and 6a of FIG. 2 are built in the power supply apparatuses 4 and 6, but the noise filters 4a and 6a may be externally attached to the power supply apparatuses 4 and 6. The noise filters 4a and 6a are not limited to the circuit configuration shown in FIG.

  Next, a ground connection failure detection method using the ground connection failure detection apparatus 1 configured as described above will be described. Here, a three-pole type inlet is used as the AC inlet 5 of the DUT 2. When a two-pole type inlet is used as the AC inlet 5 of the device under test 2, the device under test 2 has a poor ground connection.

  First, when the ground terminal of the AC inlet 5 of the DUT 2 and the ground terminal of the AC inlet 7 of the measuring instrument 3 are correctly grounded, a certain amount (several mA) of leakage current i1 due to the noise filter 6a. Flows from the power supply 6a. This leakage current i1 flows from the power supply device 6a toward the AC inlet 7 through the ground connection line 3a and passes through the current transformer 8 connected to the ground connection line 3a, as shown by the path of arrow A in FIG. And detected by the current detector 9a. The leakage current i1 detected by the current detection unit 9a is converted to a voltage value by the IV conversion amplification unit 9b, rectified by the rectifier circuit 9c, and output as a DC leakage voltage signal. Since the voltage value of the DC leakage voltage signal from the rectifier circuit 9c based on the fixed amount of leakage current i1 is within the normal range, the voltage comparator 10a generates a leakage current normal detection signal indicating that the leakage current is normal. Output. When the leakage current normal detection signal is input from the voltage comparator 10a, the controller 10b has a normal leakage current and is properly grounded, and the ground of the DUT 2 and the measuring instrument 3 is common. It is determined that the ground is kept safe and a series of logs are stored in the storage unit 11.

  On the other hand, when the ground terminal of the AC inlet 7 of the measuring instrument 3 is not properly connected to the ground, the ground terminal of the AC inlet 5 of the object to be measured 2 and the ground terminal of the AC inlet 7 of the measuring instrument 3 are correctly grounded. When both the measured object 2 side and the measuring instrument 3 side are not connected to each other and the ground connection is poor, leakage current hardly flows to the current transformer 8. Further, when the ground terminal of the AC inlet 5 of the device under test 2 is not properly grounded and the device under test 2 has a poor ground connection, as shown by the path of arrow B in FIG. A leakage current i2 flows from the power supply device 4 to the ground connection line 3a through the measurement ground E, and a leakage current i2 larger than usual is detected by the current detection unit 9a via the current transformer 8. In these cases, since the voltage value of the DC leakage voltage signal from the rectifier circuit 9c is not within the normal range, the voltage comparator 10a confirms that the leakage current is abnormal and the ground connection is incomplete. A leakage current abnormality detection signal is output. At this time, the voltage comparator 10a can also output a leakage current abnormality detection signal when the voltage value of the leakage voltage signal from the rectifier circuit 9c continues out of the normal range for a set time.

  That is, when the leakage current detected by the current transformer 8 is smaller or larger than the expected value, and the leakage current deviates from the normal range or deviates from the normal range for a set time. The leakage current abnormality detection signal is output from the voltage comparator 10a. Then, when the leakage current abnormality detection signal is input from the voltage comparator 10a, the control unit 10b determines that the leakage current is abnormal and the ground connection is incomplete, and this is indicated via the output unit 12. And a series of logs are stored in the storage unit 11.

  Even if the connection between the measuring instrument 3 and the DUT 2 is only the measurement ground E, the same detection result is obtained. That is, according to this example, whether the AC power supply is grounded or not can be detected based on whether or not the leakage current is within a normal range.

  Thus, in the ground connection failure detection device and the ground connection failure detection method of this example, the measurement ground E connects between the housing of the device under test 2 and the housing of the measuring instrument 3, and the ground is commonly grounded. At the same time, the current transformer 8 is connected to the ground connection line 3 a between the power supply device 6 and the AC inlet 7 in the measuring instrument 3. Then, the current output of the current transformer 8 is voltage-amplified by the IV conversion amplifier 9b, and converted to a DC voltage value (leakage voltage signal) through the rectifier circuit 9c. Then, the voltage comparator 10a compares whether or not the DC voltage value is within a predetermined normal (steady) normal range, and the DC voltage value deviates from the normal range or continues for a set time. In the case of deviating from the normal range, a leakage current abnormality detection signal is output. Based on this leakage current abnormality detection signal, the control unit 10b notifies the user of a ground connection failure via the output unit 12 (display unit or audio output unit). Issue a warning. As a result, it is possible to reliably detect a ground connection failure without flowing an intentional leak current as in the prior art. In addition, the user can be surely notified by display or sound that a ground connection failure has occurred.

  In this example, a series of logs from when the leakage current detection unit 9 detects the leakage current to when it is determined whether or not the leakage current is within the normal range are stored in the storage unit 11. Thereby, the log memorize | stored in the memory | storage part 11 can be analyzed, and the analysis result of this log can be used for the improvement proposal regarding a ground connection defect. The storage unit 11 may store at least a log when the leakage current deviates from the normal range. Thereby, the minimum necessary log when abnormality occurs in the leakage current can be stored in the storage unit 11.

  By the way, in the above-described embodiment, as shown in FIG. 1, the signal discrimination processing unit 10 is configured by the voltage comparator 10a and the control unit 10b. However, for example, an A / D converter and an arithmetic processing unit (CPU) are replaced. The signal discrimination processing unit 10 can also be configured. In this case, the A / D converter converts the analog value of the leakage current from the rectifier circuit 9c into a digital value. The arithmetic processing unit determines whether or not the digital value converted by the A / D converter is within a preset normal range, and if the digital value deviates from the normal range or a set time A leakage current abnormality detection signal is output when the current value continuously deviates from the normal range, and the fact that the leakage current is abnormal and the ground connection is incomplete is indicated by a message display or lamp lighting via the output unit 12. Warn the user. Further, a series of logs from when the leakage current detection unit 9 detects the leakage current to when it is determined whether or not the leakage current is within the normal range is stored in the storage unit 11.

  Although the best mode of the ground connection failure detection device and method according to the present invention has been described above, the present invention is not limited by the description and drawings according to this mode. That is, it is a matter of course that all other forms, examples, operation techniques, and the like made by those skilled in the art based on this form are included in the scope of the present invention.

1 Ground connection failure detection device 2 Device under test (DUT)
2a Ground connection line 3 Measuring instrument 3a Ground connection line 4 Power supply device 4a Noise filter 4a1, 4a2 Terminal (line)
4a3, 4a4 terminals (load)
5 AC inlet 6 Power supply 6a Noise filter 7 AC inlet 8 Current transformer (CT)
DESCRIPTION OF SYMBOLS 9 Leakage current detection part 9a Current detection part 9b IV conversion amplification part 9c Rectifier circuit 10 Signal processing part 10a Voltage comparator 10b Control part 11 Storage part 12 Output part E Measurement earth i1, i2 Leakage current R1, R2 Resistance C1, C2, C3, C4 capacitor L1 choke coil

Claims (6)

The device comprises a device under test (2) and a measuring device (3) that performs various measurements of the device under test. The device is connected between the device under test and the measuring device, and a ground is connected in common. In the ground connection failure detection device (1) for detecting whether the measured object side and / or the measuring instrument side is properly grounded,
The object to be measured is
A power supply (4) with a built-in or external noise filter (4a);
A two-pole or three-pole AC inlet (5) connected to a power supply device included in the device to be measured ;
The measuring instrument is
A power supply (6) with a built-in or external noise filter (6a);
A three-pole AC inlet (7) connected to a power supply provided in the measuring instrument ;
A current transformer (8) connected to a ground connection line (3a) grounded by connecting between a power supply device provided in the measuring instrument and a G terminal of an AC inlet provided in the measuring instrument ;
A leakage current detector (9) for detecting an AC leakage current flowing in the ground connection line ;
A signal determination processing unit (10) for determining whether or not the leakage current detected by the leakage current detection unit is within a normal range, and outputting an abnormal signal when the leakage current deviates from the normal range; A ground connection failure detecting device comprising: The ground connection failure detection device according to claim 1, further comprising: an output unit (12) for outputting, when the signal discrimination processing unit (10) outputs the abnormal signal, a display or a voice to that effect. . The ground connection failure detection device according to claim 1 or 2, further comprising a storage unit (11) for storing at least a log when the leakage current deviates from the normal range. Using a ground connection failure detection device (1) comprising a device under test (2) and a measuring device (3) that performs various measurements of the device under test, the device under test has a noise filter (4a). internal or external to the power device (4), wherein possess a two-pole or three-pole AC inlet connected to a power supply device DUT comprises (5), the measuring instrument, noise filter (6a ) and is internal or external to the power device (6), wherein the instrument is connected to a power supply device provided in the 3-pole AC inlet (7), AC of the provided measurement instrument comprises a power supply device and the measuring instrument possess a current transformer (8) between which is connected to the connection to the housing grounded ground connection line (3a) and the inlet of the G terminal, wherein between the object to be measured and the measuring instrument (3) To connect the ground to a common ground, and In the ground connection failure detection method beauty / or the measuring instrument side to detect whether it is properly grounded connection,
Detecting an AC leakage current flowing in the ground connection line ;
Determining whether or not the leakage current is within a normal range, and outputting an abnormal signal when the leakage current deviates from the normal range. 5. The ground connection failure detection method according to claim 4, further comprising a step of outputting a message to that effect when the abnormal signal is output. According to claim 4 or 5 Ground connection failure detection method according to, characterized in that a log of when the leakage current deviates the normal range storage unit (11) comprises the step of storing at least.

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