KR20070027481A - On-line low-voltage cable fault locating system - Google Patents

Abstract

A system for detecting a leakage point of an on-line low-voltage cable is provided to remove leakage causes by accurately judging a leakage section and to supply exact information to an operator. In a system for detecting a leakage point of an on-line low-voltage cable(4), a remote control device reads a leakage current value or an insulation resistance value according to the number of measuring devices, judges the difference between the leakage current values of devices(20a) installed at the adjacent sections according to the order of all devices installed from a transformer(1) or the difference between the leakage current values of the devices mounted at the adjacent sections according to the order of all devices installed from a load(5), and then displays n-th and (n+1)th sections as leakage sections or outputs an alarm if the leakage current value of the n-th section from the transformer is over a leakage warning set value with exceeding the leakage current value of the (n+1)th section or an insulation resistance value of the n-th section is below a leakage warning set value without exceeding the insulation resistance value of the (n+1)th section. In addition, the remote control device displays the n-th and (n+1)th sections as leakage sections or outputs an alarm if the leakage current value of the n-th section from the load is smaller than a leakage warning set value without exceeding the leakage current value of the (n+1)th section or an insulation resistance value of the n-th section is over a leakage warning set value with exceeding the insulation resistance value of the (n+1)th section. And, the remote control device displays the n-th and load sections as leakage sections or outputs an alarm if the leakage current of the measuring device closest to the load is over a leakage warning set value or an insulation resistance value is below a leakage warning set value.

Description

On-Line Low-Voltage Cable Fault Locating System}

1 is a measuring device installation example 1 according to the present invention

Figure 2 is a first embodiment showing a block configuration inside the measuring apparatus according to the present invention

Figure 3 is a second embodiment of the measuring device installation according to the present invention

Figure 4 is a second embodiment showing a block configuration inside the measuring apparatus according to the present invention

5 is a measuring device installation example 3 according to the present invention

Figure 6 is a third embodiment showing a block configuration inside the measuring apparatus according to the present invention

7 is a fourth embodiment of the measuring device installation according to the present invention

Figure 8 is a fourth embodiment showing a block configuration inside the measuring apparatus according to the present invention

9 is a flow chart of the embodiment 1 of the main control flow in the measuring device according to the present invention.

Figure 10 is a second control flow example 2 in the measuring apparatus according to the present invention

11 is a communication line connection configuration embodiment 1 with a monitoring room according to the present invention

12 is a configuration example 2 of a communication line connection with a monitoring room according to the present invention

13 is an embodiment of the main control control flow of the control device of the monitoring room for determining the earth leakage section according to the present invention

14 is a diagram illustrating a method of determining a short circuit section according to the present invention.

15 is a ground fault monitoring control flow of the conventional method

16 is a table for explaining a method for determining a short circuit section of a conventional method;

17 shows another embodiment of the control unit in the measuring device according to the present invention.

18 is another embodiment of a low frequency overlapping method according to the present invention

* Description of the symbols for the main parts of the drawings *

1: high voltage / low voltage transformer 2: 2 ground wires of low voltage transformer

3: Class 2 Ground 4: Low Voltage Line

5: load 6: Class 3 ground or earth

7: cavity or manhole 8: low-frequency overlapping signal device

9: low frequency superposition transformer 10: current transformer for leakage current measurement

12: voltage / current converter 13: amplifier

14a: Band pass filter for commercial frequency 14b, 14c: Band pass filter for low frequency

15a: Commercial frequency amplifier 15b, 15c: Low frequency amplifier

16a: analog / digital converter for commercial frequency

16b, 16c: analog / digital converter for low frequency

20a: Example of Detection Unit for Measuring Commercial Frequency Leakage Current

20b: Example of Detection Unit for Low Frequency Leakage Current Measurement

20c: embodiment of a commercial frequency / low frequency combined leakage current detector

20d: Low-frequency (f1) / low-frequency (f2) Z Combined Leakage Current Detector Example

40: internal control of the measuring device 41: CPU

42: ROM 43: RAM

44: I / O (input / output unit) 45: display unit

47: Data setting part 48: Alarm output part

49: remote communication unit 50: KEY input unit

50a ~ 50e: Explanation of control flow of conventional earth leakage monitoring method

60: control unit of the monitoring room

61: CPU 62: ROM

63: RAM 64: display unit

65: alarm output unit 66: setting input unit

67: remote communication unit 68: power communication modem

69: communication line

70a to 70d: Explanation of the control flow of Example 1 in the measuring device

80a to 80f: Description of the control flow of Example 2 in the measuring device

90a to 90n: Control flow diagram of the embodiment in the control unit of the monitoring room

The present invention relates to an apparatus for detecting and detecting an electric leak position or an electric leak section of a low voltage line in a live state without power failure, and using the following four leakage current detection methods to detect an electric leak The present invention relates to a system for detecting and detecting a position or an earth leakage section.

1) In order to eliminate the malfunction of the ground fault circuit breaker and the ground fault detector such as the ground fault alarm which detects the leakage current caused by various frequencies generated by various loads, the leakage current other than the common frequency is removed and the leakage current of only the common frequency component A system for detecting and detecting an earth leakage position or an earth leakage section using the leakage current,

2) In order to eliminate the reactive leakage current component caused by the capacitance existing at the cable line and the load input terminal, a separate low frequency signal (for example, 20 Hz or less) is superimposed on the cable line to detect only the leakage current generated by the low frequency signal voltage. A system which searches for and detects an earth leakage position or an earth leakage section using the leakage current,

3) In order to eliminate the leakage current component of the capacitance component existing in the cable line and the load input terminal, a separate low frequency signal (for example, 20 Hz or less) is superimposed on the cable line, and the leakage current and the commercial frequency component generated by this full frequency signal voltage are superimposed. A system that detects leakage current of the bay and calculates the effective leakage current related to the leakage current from the leakage currents of these two components, and searches for and detects the leakage position or the leakage section.

4) Two kinds of low frequency signal (e.g. 20Hz or less) are superimposed on the line to eliminate reactive leakage current caused by the capacitance existing at the line and the load input. A system that detects leakage current and calculates an effective leakage current related to leakage from these two low-frequency leakage currents to search for and detect leakage locations or leakage sections.

The present invention relates to a system for detecting and identifying an electric leak location or an electric leak section using a method of detecting an electric leak using the above four leakage current detection methods.

In consideration of urban aesthetics and human safety accidents, low-voltage lines are installed underground in large cities, and low-voltage lines are connected at regular intervals using joints or manholes. In addition, short-term deterioration due to skin damage that occurs during construction is causing a short circuit. In addition, in electrical facilities such as street lamps, a short circuit breaker is used for each section to prevent a short circuit safety accident.

However, the earth leakage breaker or earth leakage alarm, which is used in many electric facilities, has the capacitance distributed between the cable line and the ground in the long-distance cable line, and the capacity component of the noise filter in the input terminal of the load when the electronic equipment is used as the load. There are many cases in which a ground fault breaker or ground fault alarm is malfunctioning even if a ground fault does not occur. Even though the ground fault breaker or ground fault alarm generates a ground fault alarm signal, it takes much time and manpower to investigate where the ground fault occurs. It's happening.

Conventionally, in order to search for an earth leakage point or an earth leakage section, the low voltage line is blacked out, the connection point is separated by an insulation resistance meter, and the insulation resistance is checked and the earth leakage section is checked by checking the insulation resistance, or the leakage current is measured along the wire path. The leakage current after passing through the leakage point is greatly reduced. In this case, the method of searching the earth leakage area or the earth leakage section with the insulation resistance meter is effective, but it requires the power failure and the insulation resistance between the conductor and the ground should be checked by cutting the wires in the middle, which requires a lot of time and expense to repair. There is a problem, and the method of searching the leakage current position with the leakage current meter is possible in the live state, but it is necessary to check the cavity or manhole so that it takes a lot of time, and the AC current frequency flows to the ground due to the capacitance component. There has been a problem of the possibility of not finding it or making a mistake. There are other conventional methods such as Patent 10-0463450 and Patent 10-0503713, but this method relates to a pin pointing method for finding the exact leakage position of underground cables. The exact earth leakage position can be found by finding the change of earth potential difference due to the pulsed current flowing from earth leakage position to earth ground by overlapping the high voltage pulse between cable conductor and earth. It takes a lot of time to find the location of the earth leakage in a condition that is not limited to a certain degree, and the change in the earth potential difference occurs because the pulsed voltage is alleviated at the place of the capacitance or the insulation degradation on the long distance line. If you have trouble finding a location and there are multiple ground fault locations, After the paper insulation to the reinforcement, it is required to apply the method of short circuit re-detecting the other position. This method can be said to be an earth leakage position detection method that is suitable for the purpose of finding and strengthening the insulation position. In addition, Patent Publication No. 10-2005-0002945 describes a method for quickly searching for an earth leakage section in a street light. Although this conventional method is convenient because there are various functions, the earth leakage section is identified by the algorithms shown in Figs. In this conventional technique, there is a problem in that a position or section close to the load side is regarded as a short circuit position or a short circuit section when the ground fault point has a plurality of leak points. Even if there is a problem that is identified as a short circuit. This problem is compared with the result of the earth leakage section determination of the present invention in FIG.

Therefore, even in a long distance cable, it is possible to reduce the earth leakage fault due to the capacitance, and to prevent the earth leakage position or the earth leakage section from being misunderstood even when there are a plurality of earth leakage positions or earth leakage sections, or an initial deterioration such as an unknown failure over the entire section. There has been a demand for a device capable of quickly and promptly identifying a short circuit location or a short circuit section.

The present invention devises a system relating to a method for detecting leakage currents related to the following four ground faults in order to satisfy the above conventional requirements.

The first aspect of the present invention is that the capacitance of the low voltage line between the ground and the load input terminal in the measuring device shown in Figs. 2 and 9 (or Fig. 10) is applied to the frequency of various components (particularly higher than the commercial frequency). Even if the insulation condition is good due to the leakage current leaked to the ground, it can be detected as an insulation failure such as a short circuit due to the leakage current of the capacitive component. Therefore, the component of pure commercial frequency (60Hz or 50Hz) If only the leakage current is detected, and if the detected leakage current component detects a leakage current exceeding the earth leakage alarm set value, the measuring device transmits it to the monitoring room by various communication methods (RS-232, RS-485, wireless communication, power line communication, etc.). In FIG. 13, a system for detecting an accurate earth leakage position or an earth leakage section by an algorithm of a control flow as shown in FIG.

The second point of the present invention is that the measurement device composed of Figs. 3, 4, 9 (or 10) is more effective than the conventional frequency in order to more actively eliminate the influence of the leakage current of the capacitance component by the AC voltage of the commercial frequency. When the low frequency below 20Hz is superimposed on the cable line and detects only the leakage current flowing to the ground by this low frequency component, and if the detected leakage current component detects a leakage current higher than the earth leakage alarm set value, various communication methods (RS-232, RS-485, wireless communication, power line communication, etc.) to the monitoring room and the monitoring room detects the exact leakage location or leakage section by the control flow algorithm as shown in FIG.

The third aspect of the present invention is the leakage current and the commercial frequency by the low frequency component flowing between the cable line and the ground by overlapping the low frequency of 20 Hz or less in the cable line in the measuring device composed of FIGS. 5, 6, and 9 (or 10). From the leakage current of the component, the effective leakage current is detected by the resistance component. If the detected leakage current component detects a leakage current exceeding the earth leakage alarm set value, the measuring device uses various communication methods (RS-232, RS-485, wireless communication, System to detect the exact ground fault location or ground fault section by the control flow algorithm as shown in FIG.

In the fourth aspect of the present invention, two types of low frequencies of 20 Hz or less are superimposed on an electric wire in a measuring device composed of FIGS. 7, 8, and 9 (or 10), and the respective low frequencies are generated by these two types of low frequency components. By detecting the leakage current for the current and calculating the effective leakage current by the resistance component from the detected two kinds of low-frequency leakage currents, if the leakage current component detects a leakage current higher than the earth leakage alarm set value, the communication device System (RS-232, RS-485, wireless communication, power line communication, etc.) to the monitoring room by transmitting to the monitoring room in the monitoring room algorithm of the control flow as shown in FIG.

It is an object of the present invention to provide four respective systems for detecting a short circuit section of a low voltage converter in the live state.

Hereinafter, an apparatus for searching and detecting an electric leak position or an electric leak section of a low voltage converter in an active state of the present invention will be described in detail with reference to four embodiments and drawings of the present invention.

1, 2, 9 (or 10) corresponding to the measuring device of the first embodiment, and a control flow of the control device 60 of the monitoring room for detecting and detecting a ground fault position or a ground fault section remotely. 13 and FIG. 14 and FIG. 11 or FIG. 12 relating to a system for transmitting and receiving various data of the measuring apparatus with the control unit of the monitoring room will be described.

In Figure 1 (special) high-voltage / low-voltage transformer (1) is connected to the ground type (2) of the neutral point (or one-point ground of the delta connection) of the low-voltage side wire connection is connected to the ground type (2), low-voltage wire ( In the general electric power system in which power is supplied to the load 5 through 4), when the low voltage line 4 is a long distance line, there are most cases where there are several manholes 7 or cavity holes. The state of manhole 2, manhole 3, and manhole n is shown, and between each manhole 7 there is an insulation resistance R (R1, R2, ..., Rn) which is directly related to a short circuit between the earths. In parallel with the resistor R, the floating capacitance C (C1, C2 ,,,,, Cn) of the wire path 4 exists. This capacitance C is a component that is not directly related to a short circuit. However, when the capacitance is small, a short circuit state can be known by measuring a leakage current flowing to the ground. Each manhole 7 has a measuring device M1 20a and a video current transformer ZCT 10 for detecting a leakage current. The measuring device M1 20a is described in detail in FIG. 2 is an internal block detail view of the measuring device M1 20a. In FIG. 1, when the cable line 4 is in a live state, the leakage current of the commercial frequency component with respect to the AC phase voltage of the commercial frequency (50/60 Hz) from the cable line 4 and the load 5 to the earth ground according to the earth-to-earth insulation state. Leakage currents in other frequency bands may also flow under the influence of the load, load, and low-voltage system, which are detected by the image transformer ZCT 10 and the measuring device M1 installed in each manhole 7. . Depending on the insulation state of each manhole (7) section, the leakage current value detected by the measuring device M1-device 1, device 2, and device n will vary, but the class 2 ground wire (2) of the transformer or transformer (1) will vary. The leakage current value detected by the device 1 installed closest to the low pressure side of the circuit will be the largest. The leakage current detected by the image current transformer ZCT 10 converts the leakage current into a voltage component in the current / voltage conversion unit 12 of FIG. 2, amplifies the converted value in the amplifier 13, and converts the amplified value into a commercial component. The bandpass filter 14a for frequency (50 Hz or 60 Hz) extracts only the value corresponding to the commercial frequency component, and amplifies the value corresponding to the leakage current of the extracted commercial frequency component in the commercial frequency amplifier 15a. The value is converted into a digital value by the commercial frequency analog / digital converter 16a and then read by the CPU 41. When this value is calculated for the AC phase voltage between the amplification degree and the commercial frequency according to the control flow of the measuring apparatus of FIG. 9 or 10, it corresponds to the leakage current value corresponding to the commercial frequency component related to the insulation state. It can also be calculated from the insulation resistance against the AC-to-phase AC voltage. The calculated leakage current value or insulation resistance value may be displayed on the display unit of the measuring device, and as shown in the other embodiment of FIG. 17, a function of generating an alarm output may be used when a leakage current equal to or greater than the ground fault alarm value is measured. FIG. 17 is another embodiment of the internal control unit 40 of the measuring device of FIG. 2 (or FIG. 4 or 6 or 8). The key input unit 50 allows the user to set various setting data necessary for device operation using a keypad. ) And an alarm output unit 48 capable of outputting or displaying an alarm to the outside in case of a short circuit occurrence or an error, and configured to perform more various functions. 9 and 10 illustrating the control flow of the measuring apparatus in the following order, the following description will be added.

9 will be described first. Using the same method as the switch or keypad, the control flow of various data settings 70a for setting the data necessary for the operation of various devices such as address setting, earth leakage alarm set value, communication method, etc. of the device is executed and analog / digital conversion is performed. Leakage current calculation that performs the control flow of the leakage current measurement 70b that reads the digital value corresponding to the converted leakage current of the unit 16a and calculates the leakage current or insulation resistance value for the AC phase voltage between the amplification and the commercial frequency. The control unit 60 of the remote monitoring room by executing the control flow of (70c) and sending various calculated data (device address, leakage current value or insulation resistance value, etc.) to the monitoring room according to various communication methods. The control flow of various data transmissions 70d for communicating with each other is executed.

10, another embodiment of the main control flow in the measuring device will be described. Control flow of various data setting (80a) to set the data necessary for device operation such as address setting, earth leakage alarm set value, alarm output use, communication method, etc. And a control flow of the leakage current measurement 80b that reads the digital value corresponding to the converted leakage current of the analog / digital converter 16a, and calculates a leakage current for the AC phase voltage between the amplification degree and the commercial frequency. If the leakage current is larger than the earth leakage alarm set value by executing the control flow of the current calculation 80c and executing the control flow of the earth leakage alarm set value or higher (80d) to determine whether the calculated leakage current value is greater than the earth leakage alarm set value. Control flow of Alarm output 80e which outputs and communicate various data (device address, leakage current value, insulation resistance value, etc.) to monitoring room according to various communication methods. The monitoring thread executing a control flow of the various DATA transmission (80f). Even if the leakage current value is smaller than the earth leakage alarm setting value, the monitoring room communicates various data (device address, leakage current value, insulation resistance value, etc.) to the monitoring room according to the communication method, so that the monitoring room can identify the accurate leakage location or the earth leakage section. The control flow of the transmission 80f is executed. After the control flow of the various data transmissions 80f is executed in the monitoring room, the control flow returns to the control flow of the leakage current measurement 80b again.

By the control flow of the various data transmissions 70d to the remote monitoring room of FIG. 9 or the control flow of the various data transmissions 80f to the monitoring room of FIG. 10, various data in the measuring device are RS-232 or RS-485 communication method. Although not shown in FIG. 11 or FIG. 12, which is an embodiment of the power line communication method, according to the wireless communication method or the like, the CPU 61 may communicate with the communication unit 67 of the control device 60 of a remote monitoring room. In the case of transmission, the ground fault position or the ground fault section is determined and determined according to the control flow as shown in FIG. 13. FIG. 14 illustrates an embodiment of the result of the earth leakage section determination result of the present invention according to the earth leakage position of the result of executing the control flow of FIG. 13. After FIG. 13 is described in detail, FIG. 14 will be described in detail.

FIG. 13 illustrates the control flow of the control device 60 of the remote monitoring room in detail. The measuring device M1 20a corresponding to the device 1, device 2, and device n installed in each manhole 7 is described. In order to read the various data transmitted from the device, the control flow of n = 1 (90a) is set to set the first device number, and each device reads the various data and leakage current value or insulation resistance value transmitted from the devices 1, 2, and n. Control flow of various data and leakage current reading (90b) for each data, i_data (n) = control flow of leakage current (90c) of device n for storing various data read in this flow, The control flow of n = n + 1 (90e) is executed to increase the device number if the data is not read until the last device by executing the flow of n = n (last device) (90d) for judging whether the data has been read. Return to the control flow of reading various data and leakage current (90b) for each device to read various data of n + 1 device If the data is read repeatedly from the last device, the i_data (n) = device n leakage current 90c is used to determine in which device section a short circuit occurs from the first device number to the last device number. In order to read the leakage current value of each device number stored in the control flow, the control flow of n = 1 (90f) is executed to set the device number as the first device number, and the leakage current of device 1 is the leakage current + leakage of device 2. The control flow of i_data (n) -i_data (n + 1), which judges whether it is greater than the alarm set value (example 30mA) or more than the leakage alarm set value (90g), is performed so that the leakage current of device 1 is the leakage current of device 2 + leakage. If it is greater than the alarm setting value, n indicates that the device 1 and device 2 sections have a short circuit or n displays the alarm and the control flow of the (n + 1) section has a short circuit occurrence (90h), and n increases the device number by 1 (+1). = n + 1 (90i), go to the control flow, and before the leakage of device 1 If the current is not greater than the leakage current + leakage alarm set value of the device 2, the flow moves to a control flow of n = n + 1 (90i) which increases the device number by one (+1). Next, a control flow of n = n (last device) (90j) for judging whether or not the last device number is executed is executed, and if it is not the last device number, the short circuit section of the last device (n) and the last electric device (n-1) is performed. To judge, go back to the control flow of i_data (n) -i_data (n + 1) is more than the leakage alarm set value (90g), and if the last device number is the last device number (n) or the short circuit occurs in any section If i_data (n) is higher than the earth leakage alarm set value (90k), the control flow of i_data (n) is higher than the earth leakage alarm set value (90k). If there is a leakage section to check whether there is a short circuit from the device 1 to the device n when the last device is not larger than the earth leakage alarm set value, 90m), and if there is no earth leakage section, a control flow of no earth leakage occurs (90n) displaying a message that a short circuit has not occurred in all sections. As a result of determining the earth leakage section according to the leakage current value measured by the measuring devices installed in the respective manholes 7, a result of the earth leakage was described in detail with reference to FIG. 14.

14 will be described in detail. In FIG. 14, six types of leakage currents have been described. The leakage current setting value is 30 mA, the device is an example of five manholes or four manholes, and the measurement device is installed at a two-ground ground wire (low pressure output side of the transformer). Device 2 installed in the manhole 1, device 2 installed in the manhole 2, device 4 installed in the manhole 3, and device 5 installed in the manhole 4. An example of the electrical leak occurrence will be described. The leakage current of the commercial frequency component measured in the device 1 is 50 mA, the leakage current of the commercial frequency component measured in the device 2 is 20 mA, the leakage current of the commercial frequency component measured in the device 3 is 10 mA, and calculated in the device 4. The leakage current of the commercial frequency component measured is 6 mA, and the leakage current of the commercial frequency component calculated by the device 5 is 2 mA. As a result of the control flow in FIG. 13, i_data (n) -i_data (n + 1) = i_data (1) -i_data (2) = 50mA-20mA = 30mA, so the earth leakage section is set as the earth leakage section. It is a section. This is the same as the result of the earth leakage judgment of the conventional method. The earth leakage generation example 2 and the earth leakage generation example 3 are similar to those of the earth leakage generation example 1, but are not described in detail here, but are the same as those of the earth leakage determination result of the present invention and those of the conventional method. Next, a short circuit occurrence example 4 will be described. i_data (1) -i_data (2) = 30mA, i_data (2) -i_data (3) = 30mA, i_data (3) -i_data (4) = 4mA, i_data (4) -iata (5) = 4mA, i_data ( n) = i_data (5) = 2mA and the interval of the earth leakage alarm set value (eg 30mA) is the device 1 and device 2 sections and the device 2 and device 3 sections. In the present invention, it was determined that a short circuit occurred in two sections, and in the conventional method, a short circuit occurred in the device 2 and device 3 sections. Actually, the short circuit occurs in two sections, but it can be seen that the conventional method makes a misjudge that a short circuit occurs only in a section close to the load side. An electrical leak occurrence example 5 is an electrical leak occurrence example similar to the electrical leak occurrence example 4, but has made the misjudgment that an electrical leak occurs only in one section close to a load side like an electrical leak occurrence example 4 even if an electrical leak occurs in two sections. In the following example, no leakage occurs: i_data (1) -i_data (2) = 15mA, i_data (2) -i_data (3) = 15mA, i_data (3) -i_data (4) = 15mA, i_data (4 ) -iata (5) = 15mA, i_data (n) = i_data (5) = 10mA There is no section above the earth leakage alarm set value (example 30mA). There is a misjudgment that a short circuit occurs in devices 3 and 4. In the case where there are a plurality of short circuits, the present invention can accurately determine a short circuit occurrence or a short circuit occurs even if there is no short circuit. Information can be provided.

Next, a second embodiment will be described in detail.

3, 4, and 9 (or FIG. 10) corresponding to the measuring device, which is the second embodiment, and a control flow of the control device 60 of the monitoring room for detecting and detecting a ground fault position or a ground fault section remotely. 13 and 14 and FIG. 11 or 12 corresponding to the control apparatus of the monitoring room will be described.

In Figure 3 (special) high-voltage / low-voltage transformer (1) is connected to the ground type (2) of the neutral point (or one-point ground of the delta connection wire) of the low-voltage side wire connection is connected to the ground type (2), low-voltage wire ( In a general electric power system in which power is supplied to the load 5 through 4), when the low voltage line 4 is a long distance line, there are most cases where there are several manholes 7 or cavity holes. The state of manhole 2, manhole 3, and manhole n is shown, and between each manhole 7 there is an insulation resistance R (R1, R2, ..., Rn) which is directly related to a short circuit between the earths. In parallel with the resistor R, the floating capacitance C (C1, C2 ,,,,, Cn) of the wire path 4 exists. This capacitance C is a component that is not directly related to a short circuit. The measuring device M2 (20b) and the image current transformer ZCT (10) are installed in each manhole (7), and the two-type ground wire connecting the neutral point (or one-point ground of the delta connection) and the earth ground (3) of the transformer 1 ( In order to exclude the influence of leakage current of components of commercial frequency (50Hz or 60Hz) in the middle of 2), for example, an overlapping transformer provided separately to superimpose a low frequency of 20 Hz or less f1 Hz on the low voltage line 4 (9) or another embodiment, the superimposition resistance 9a and the low frequency overlapping apparatus 8 of FIG. 18 are provided, and this measuring apparatus M2 20b is shown in detail in FIG. 4 is a detailed internal block diagram of the measuring device M2 20b. In FIG. 3, when the wire path 4 is in a live state, the commercial frequency f0 component for an AC phase voltage of a commercial frequency (50 Hz or 60 Hz) is grounded according to the earth-to-earth insulation state in the wire path 4 and the load 5. F1 Hz superimposed on the low voltage line 4 by using the transformer 9 for superposition of the leakage current if0 and the type 2 ground wire 2 or the superposition resistance 9a and the low frequency superposition device 8 The leakage current if1 of the f1 Hz component due to the low frequency signal voltage also flows. The leakage currents of if0 + if1 are detected by the image current transformer ZCT 10 and the measuring device M2 provided for each manhole 7. The leakage current value detected by the measuring device M2-device 1, device 2, and device n will vary according to the insulation state of each manhole 7 section, but the leakage current value detected by the device 1 will be the largest. The leakage current if0 + if1 detected by the image current transformer ZCT 10 converts the leakage current into a voltage component in the current / voltage conversion unit 12 of FIG. 4, and amplifies the converted value in the amplifier 13. The amplified value is extracted from the band pass filter 14b for f1 Hz, and only the value corresponding to the f1 Hz frequency component is amplified, and the value corresponding to the leakage current of the extracted f1 Hz low frequency component is amplified by the f1 Hz low frequency amplifier 15b. The amplified value if1a is converted into a digital value by the f1 Hz low frequency analog / digital converter 16b and then read by the CPU 41. When this value is calculated for the amplification degree and the inter-phase AC phase voltage or f1 Hz low frequency superimposition signal voltage of the amplification degree and the commercial frequency according to the control flow of the measuring apparatus of FIG. 9 or 10, the commercial AC voltage or the f1 Hz low frequency signal related to the insulation state It corresponds to the leakage current value corresponding to the voltage, and the leakage current value can be calculated as an insulation resistance value for an AC-to-ground AC phase voltage or a f1 Hz low frequency signal voltage. The calculated leakage current value or insulation resistance value may be displayed on the display unit of the measuring device, and as shown in the other embodiment of FIG. 17, a function of generating an alarm output may be used when a leakage current equal to or greater than the ground fault alarm value is measured. FIG. 17 illustrates another embodiment of the internal control unit 40 of the measuring apparatus of FIG. 4 (or FIG. 2 or FIG. 6 or FIG. 8). The key input unit 50 allows various setting data necessary for device operation to be set using a keypad. And it is configured to perform a variety of functions by having an alarm output unit 48 to function to output or display the alarm to the outside when a short circuit or error occurs. 9 and 10 illustrating the control flow of the measuring apparatus in the following order, the following description will be added.

9 will be described first. Using the same method as the switch or keypad, the control flow of various data settings 70a for setting the data necessary for the operation of various devices such as address setting, earth leakage alarm set value, communication method, etc. of the device is executed and analog / digital conversion is performed. The control flow of the leakage current measurement 70b, which reads the digital value corresponding to the converted leakage current of the unit 16b, is executed, and the leakage current is calculated for the AC phase voltage between the amplification degree and the commercial frequency, or the f1 Hz low frequency overlapping signal voltage. The control flow of the leakage current calculation 70c is executed. Here, it may be converted into a leakage current or an insulation resistance value for a signal voltage of a low frequency component of f1 Hz, or may be converted into a leakage current or an insulation resistance value for an AC phase voltage of a commercial frequency (50 Hz or 60 Hz). The calculated leakage current value or insulation resistance value is transmitted to the monitoring room in order to communicate various data (device address, leakage current value, insulation resistance value, etc.) to the monitoring room to execute control flow of various data transmissions 70d.

10, another embodiment of the main control flow in the measuring device will be described. Control flow of various data setting (80a) to set the data necessary for device operation such as address setting, earth leakage alarm set value, alarm output use, communication method, etc. The control flow of the leakage current measurement (80b), which reads the digital value corresponding to the converted leakage current of the analog / digital conversion section (16b), to the AC phase voltage between the amplification degree and the commercial frequency, or to the f1 Hz low frequency overlapping signal voltage. A control flow of the leakage current calculation 80c that calculates the leakage current is executed, where it can be converted into a leakage current or insulation resistance value for a signal voltage of a low frequency component of f1 Hz, or a commercial frequency (50 Hz or 60 Hz). It can be converted into leakage current with respect to AC phase voltage or converted into insulation resistance value. Is the calculated leakage current value larger than the earth leakage alarm setting value or the insulation resistance value is the earth leakage alarm setting value? If the leakage current is greater than the earth leakage alarm set value by executing the control flow of the earth leakage alarm set value or higher (80d) to judge whether it is small, perform the control flow of the alarm output (80e) that performs the alarm output and remotely according to the communication method. To the monitoring room to communicate various data (device address, leakage current value, insulation resistance value, etc.) to the control flow of various data transmissions (80f). Even if the leakage current value is smaller than the earth leakage alarm setting value, the monitoring room communicates various data (device address, leakage current value, insulation resistance value, etc.) to the monitoring room according to the communication method, so that the monitoring room can identify the accurate leakage location or the earth leakage section. The control flow of the transmission 80f is executed. After the control flow of the various data transmissions 80f is executed in the monitoring room, the control flow returns to the control flow of the leakage current measurement 80b again.

이므로, 주파수에 밀접하게 관계되어 주파수가 무효누설전류가 커진게 된다. 이 무효누설전류의 영향을 줄이기 위해 상용주파수(50Hz 또는 60Hz)보다 낮은 f1 Hz의 저주파수의 신호전압을 전선로(4)에 중첩하여 이 저주파수의 신호전압에 의해 누설되는 f1 Hz성분만의 저주파수 누설전류(if1 또는 if1a)만 또는 절연저항치를 검출하는 것이다.누전에 직접관계하는 절연저항R에 의한 유효누설전류를 검출하는 데 있어 제 2실시예가 제 1실시예에 비해 정확도가 높다.By the control flow of various data transmissions 70d to the monitoring room of FIG. 9 or the control flow of various data transmissions 80f to the monitoring room of FIG. When the transmission to the CPU 61 through the communication unit 67 of the control device 60 of the remote monitoring room in accordance with the communication method as shown in FIG. The location or the short circuit section is determined and determined. FIG. 14 illustrates an embodiment of the earth leakage section determination result of the present invention according to the earth leakage position of the result of executing the control flow of FIG. 13 and 14, which will be described next, have been described in detail in the above-described first embodiment, which will not be described in this embodiment. In the second embodiment, the difference from the first embodiment is to detect the leakage current of the commercial frequency component in the first embodiment, and flows to the capacitance C by the AC phase voltage of the commercial frequency (50 Hz or 60 Hz) in the second embodiment. Reactive leakage current independent of leakage

Therefore, the reactive leakage current increases in frequency closely related to the frequency. In order to reduce the effect of this reactive leakage current, the low frequency leakage of only the f1 Hz component leaked by the low voltage signal voltage is superimposed on the cable line 4 with a low frequency signal voltage of f1 Hz lower than the commercial frequency (50 Hz or 60 Hz). Only the current if1 or if1a or the insulation resistance value is detected. The second embodiment has a higher accuracy than the first embodiment in detecting an effective leakage current by the insulation resistance R directly related to the leakage current.

Next, the third embodiment will be described in detail.

5, 6, and 9 (or 10) corresponding to the measuring device, which is the third embodiment, and a control flow of the control device 60 of the monitoring room for detecting and detecting a ground fault position or a ground fault section remotely. 13 and 14 and FIG. 11 or 12 corresponding to the control apparatus of the monitoring room will be described.

In Figure 5 (special) high voltage / low voltage transformer (1) is connected to the ground type (2) of the neutral point (or one-point ground of the delta connection) of the low-pressure side wire connection is connected to the grounding type (2), low-voltage wire ( In a general electric power system in which power is supplied to the load 5 through 4), when the low voltage line 4 is a long distance line, there are most cases where there are several manholes 7 or cavity holes. The state of manhole 2, manhole 3, and manhole n is shown, and between each manhole 7 there is an insulation resistance R (R1, R2, ..., Rn) which is directly related to a short circuit between the earths. In parallel with the resistor R, the floating capacitance C (C1, C2 ,,,,, Cn) of the wire path 4 exists. This capacitance C is a component that is not directly related to a short circuit. The measuring device M3 (20c) and the image current transformer ZCT (10) for detecting the leakage current are provided in each manhole (7), and the neutral point (or one-point ground of the delta connection) and the earth ground (3) of the transformer (1) are connected. In order to eliminate the influence of leakage current of components of commercial frequency (50 Hz or 60 Hz) in the middle of the connected type 2 ground wires (2), for example, to superimpose a low frequency of 20 Hz or less f1 Hz on the low voltage line (4). The overlapping transformer 9 or the overlapping resistor 9a and the low frequency overlapping apparatus 8 of FIG. 18 provided separately were provided, and this measuring apparatus M3 (20c) was demonstrated in detail in FIG. 6 is a detailed internal block diagram of the measuring device M3 20c. In FIG. 5, if the cable line 4 is in a live state, the leakage current of the commercial frequency component with respect to the AC phase voltage of the commercial frequency (50 Hz or 60 Hz) is grounded according to the earth-to-earth insulation state in the cable line 4 and the load 5. Leakage currents in other frequency bands may also flow under the influence of the load 5 and the low-voltage system, and the superimposed transformer 9 or superimposed resistor 9a and the low frequency superimposing device 8 Leakage current of the f1 Hz component due to the low frequency signal voltage of f1 Hz superimposed on the low voltage line 4 is also flown. The leakage currents of if0 + if1 are provided for each manhole 7. It is detected by the ZCT 10 and the measuring device M3. Depending on the insulation state of each manhole 7 section, the leakage current values detected by the measuring devices M3- device 1, device 2, and device n will vary, but the leakage current value detected by the device 1 will be the largest. The leakage current if0 + if1 detected by the image current transformer ZCT 10 converts the leakage current into a voltage component in the current / voltage conversion unit 12 of FIG. 6, and amplifies the converted value in the amplifier 13. The amplified value is extracted only from the band pass filter 14a for commercial frequency (f0, 50 / 60Hz) corresponding to the fo Hz frequency component, and amplified by the amplifier 15a for commercial frequency (f0). The value corresponding to the leakage current component of if0a is converted into a digital signal through the analog / digital converter 16a for commercial frequency f0. On the other hand, the leakage current amplified by the amplifier 13 extracts only the value corresponding to the f1 Hz frequency component from the low frequency band pass filter 14b of f1 Hz, and converts the value corresponding to the leakage current of the extracted f1 Hz low frequency component to f1 Hz. The low frequency amplifier 15b is amplified and the amplified value if1a is converted into a digital value by the f1 Hz low frequency analog / digital converter 16b. After conversion to this digital value, the digital values of these two components are read by the CPU 41. According to the control flow of the measuring apparatus of FIG. 9 or FIG. 10, the leakage current of the two components is read and the insulation resistance R without the influence of the capacitance component C can be calculated by the following equation.

Where E0 is the voltage across the earth at the commercial frequency. F0 is the commercial frequency and f1 is the low frequency.

E1: low frequency signal voltage, a: amplification degree corresponding to commercial frequency, b: amplification degree corresponding to low frequency, if0a: final amplified leakage current value corresponding to commercial frequency component

if1a: final amplified leakage current for low frequency component)

With the insulation resistance R value calculated above, the leakage current value for the commercial frequency AC voltage and the leakage current value for the low frequency signal voltage can be calculated as follows.

For commercial AC voltage

Or for low frequency signal voltage

The calculated leakage current value or insulation resistance value may be displayed on the display unit of the measuring device, and as shown in the other embodiment of FIG. 17, a function of generating an alarm output may be used when a leakage current equal to or greater than the ground fault alarm value is measured. FIG. 17 illustrates another example of the internal control unit 40 of the measuring apparatus of FIG. 6 (or FIG. 2 or FIG. 4 or FIG. 8). The key input unit 50 allows various setting data required for device operation to be set using a keypad. And it is configured to perform a variety of functions by having an alarm output unit 48 to function to output or display the alarm to the outside when a short circuit or error occurs. 9 and 10 illustrating the control flow of the measuring apparatus in the following order, the following description will be added.

9 will be described first. Using the same method as the switch or keypad, the control flow of the various data settings 70a for setting the data necessary for the operation of various devices such as address setting, earth leakage alarm set value, and communication method of the device is executed. Implement the control flow of the leakage current measurement 70b that reads the digital value corresponding to the converted leakage current of the digital converters 16a, 16b and superimposes the AC phase voltage or f1 Hz low frequency overlap between the amplification and commercial frequencies as described above. The control flow of the leakage current calculation 70c for calculating the leakage current with respect to the signal voltage is executed. Here, it may be converted into a leakage current or an insulation resistance value for a signal voltage of a low frequency component of f1 Hz, or may be converted into a leakage current or an insulation resistance value for an AC phase voltage of a commercial frequency (50 Hz or 60 Hz). The calculated leakage current value or insulation resistance value is transmitted to the monitoring room in order to communicate various data (device address, leakage current value, insulation resistance value, etc.) to the monitoring room to execute control flow of various data transmissions 70d.

10, another embodiment of the main control flow in the measuring device will be described. Control flow of various data setting (80a) to set the data necessary for device operation such as address setting, earth leakage alarm set value, alarm output use, communication method, etc. Then, the control flow of the leakage current measurement 80b that reads the digital value corresponding to the converted leakage current of the two analog / digital converters 16a and 16b is executed. Alternatively, the control flow of the leakage current calculation 80c, which calculates the leakage current with respect to the f1 Hz low frequency overlapping signal voltage, may be converted into a leakage current or an insulation resistance value for the signal voltage of the low frequency component of f1 Hz. In addition, it can be converted into leakage current for AC phase voltage of commercial frequency (50Hz or 60Hz) or converted into insulation resistance value. If the leakage current is greater than the earth leakage alarm set value, the control flow of the alarm output 80e is executed if the leakage current is larger than the earth leakage alarm set value. The control flow of the various data transmissions 80f is executed to the monitoring room that communicates various data (device address, leakage current value, insulation resistance value, etc.) to the monitoring room according to the communication method. Even if the leakage current value is smaller than the earth leakage alarm setting value, the monitoring room communicates various data (device address, leakage current value, insulation resistance value, etc.) to the monitoring room according to the communication method, so that the monitoring room can identify the accurate leakage location or the earth leakage section. The control flow of the transmission 80f is executed. After the control flow of the various data transmissions 80f is executed in the monitoring room, the control flow returns to the control flow of the leakage current measurement 80b again.

By the control flow of the various data transmissions 70d to the monitoring room of FIG. 9 or the control flow of the various data transmissions 80f to the monitoring room of FIG. 10, the various data in the measuring device are an embodiment of the RS-232 or RS-485 communication method. When the transmission to the CPU 61 through the communication unit 67 of the control device 60 of the remote monitoring room in accordance with the communication method as shown in FIG. The location or the short circuit section is determined and determined. FIG. 14 illustrates an embodiment of the earth leakage section determination result of the present invention according to the earth leakage position of the result of executing the control flow of FIG. 13 and 14, which will be described next, have been described in detail in the above-described first embodiment, which will not be described in this embodiment. In the third embodiment, the difference from the second embodiment is related to the leakage current flowing in the capacitance C caused by the AC phase voltage at the commercial frequency (50/60 Hz) by amplifying, detecting, and calculating only the leakage current of the low frequency component in the second embodiment. In the third embodiment, the leakage current of the commercial frequency (50 Hz or 60 Hz) component and the leakage current of the low frequency component are amplified and detected to calculate the influence of the capacitance C. Removed it. The third embodiment has higher accuracy than the second embodiment in detecting an effective leakage current due to the insulation resistance R directly related to the leakage current.

Next, the fourth embodiment will be described in detail.

7, 8, and 9 (or 10) corresponding to the measuring device of the fourth embodiment, and a control flow of the control device 60 of the monitoring room for detecting and detecting a ground fault position or a ground fault section remotely. 13 and 14 and FIG. 11 or 12 corresponding to the control apparatus of the monitoring room will be described.

In Figure 7 (special) high-voltage / low-voltage transformer (1) is connected to the ground type (2) of the neutral point (or one-point ground of the delta connection) and ground ground (3) of the low-voltage side wire connection, low-voltage wire ( In the general electric power system in which power is supplied to the load 5 through 4), when the low voltage line 4 is a long distance line, there are most cases where there are several manholes 7 or cavity holes. The state of manhole 2, manhole 3, and manhole n is shown, and between each manhole 7 there is an insulation resistance R (R1, R2, ..., Rn) which is directly related to a short circuit between the earths. In parallel with the resistor R, the floating capacitance C (C1, C2 ,,,,, Cn) of the wire path 4 exists. This capacitance C is a component that is not directly related to a short circuit. Each manhole 7 is provided with a measuring device M4 (20d) and a video current transformer ZCT (10) for detecting a leakage current. The neutral point (or one-point ground of the delta connection) and the earth ground (3) of the transformer (1) are provided. In order to exclude the influence of leakage currents of commercial frequency (50 Hz or 60 Hz) components in the middle of the connected type 2 ground lines (2), for example, two kinds of low frequencies of 20 Hz or less, f1 Hz and f2 Hz, A superimposed transformer 9 or a superimposed resistor 9a and a low frequency superposition device 8a shown in FIG. 18 are provided separately to superimpose on 4). This measuring device M4 (20d) is described in detail. 8 is shown. 8 is an internal block detail view of the measuring device M4 20d. In FIG. 7, when the cable line 4 is in the live state, the leakage current of the commercial frequency component with respect to the AC phase voltage of the commercial frequency (50 Hz or 60 Hz) is grounded according to the earth-to-earth insulation state in the cable line 4 and the load 5. And leakage currents in other frequency bands may also flow under the influence of the load 5 and the low-voltage system, and the superimposed transformer 9 or superimposed resistor 9a and the low frequency superimposition device 8a of the second type ground wire 2 may flow. Leakage current of f1 Hz and f2 Hz by two kinds of low frequency signal voltages of f1 Hz and f2 Hz superimposed on low voltage line 4 is also flowed. The currents are detected by the image current transformer ZCT 10 and the measuring device M4 provided in each manhole 7. Depending on the insulation state of each manhole 7 section, the leakage current value detected by the measuring device M4-device 1, device 2, and device n will vary, but the leakage current value detected by the device 1 will be the largest. The leakage current if0 + if1 + if2 detected by the image current transformer ZCT 10 converts the leakage current into a voltage component in the current / voltage converter 12 of FIG. 8, and amplifies the converted value in the amplifier 13. Then, the amplified value is extracted from the low pass band pass filter 14b for f1 Hz, and only the value corresponding to the frequency component of f1 Hz is amplified by the amplifier 15b for f1 Hz, which corresponds to the leakage current component of the amplified if1a. The value is converted into a digital signal through the analog-to-digital converter 16b for f1 Hz. On the other hand, the leakage current amplified by the amplifier 13 extracts only the value corresponding to the f2 Hz frequency component from the low frequency band pass filter 14c of f2 Hz, and converts the value corresponding to the leakage current of the extracted f2 Hz low frequency component into f2 Hz. The low frequency amplifier 15c is amplified and the amplified value if2a is converted into a digital value by the f2 Hz low frequency analog / digital converter 16c. After conversion to this digital value, the digital values of these two components are read by the CPU 41. According to the control flow of the measuring apparatus of FIG. 9 or FIG. 10, the leakage current of the two components is read and the insulation resistance R without the influence of the capacitance component C can be calculated by the following equation.

(E0: phase voltage of commercial AC, E1: f1 low frequency signal voltage, f1: low frequency (f1 Hz), f2: low frequency (f2 Hz), E2: f2 low frequency signal voltage, a: low frequency corresponding to f1) Amplification degree, amplification degree corresponding to b: f2 low frequency, if1a: final amplified leakage current value corresponding to f1 low frequency component, if2a: final amplified leakage current value corresponding to f2 low frequency component)

For commercial AC voltage

Or for low frequency signal voltage

The calculated leakage current value or insulation resistance value may be displayed on the display unit of the measuring device, and as shown in the other embodiment of FIG. 17, a function of generating an alarm output may be used when a leakage current equal to or greater than the ground fault alarm value is measured. FIG. 17 illustrates another example of the internal control unit 40 of the measuring apparatus of FIG. 8 (or FIG. 2 or FIG. 4 or FIG. 6). The key input unit 50 allows the user to set various setting data necessary for device operation using a keypad. ) And an alarm output unit 48 capable of outputting or displaying an alarm to the outside in case of a short circuit occurrence or an error, and configured to perform more various functions. 9 and 10 illustrating the control flow of the measuring apparatus in the following order, the following description will be added.

9 will be described first. Using the same method as the switch or keypad, the control flow of the various data settings 70a for setting the data necessary for the operation of various devices such as address setting, earth leakage alarm set value, and communication method of the device is executed. The control flow of the leakage current measurement 70b, which reads the digital value corresponding to the converted leakage current of the digital converters 16b and 16c, executes the control flow, and the amplification degree for f1 Hz and f2 Hz, the magnitude of the low frequency signal voltage as described above. Alternatively, the control flow of the leakage current calculation 70c for calculating the leakage current for the inter-phase AC phase voltage of the commercial frequency is executed. Here, it may be converted into a leakage current or insulation resistance value with respect to the signal voltage of the low frequency component of f1 Hz, and may be converted into a leakage current or insulation resistance value with respect to the signal voltage of the low frequency component of f2 Hz, It can be converted into leakage current with respect to AC phase voltage of 50Hz or 60Hz or converted into insulation resistance value. The calculated leakage current value or insulation resistance value is transmitted to the monitoring room in order to communicate various data (device address, leakage current value, insulation resistance value, etc.) to the monitoring room to execute control flow of various data transmissions 70d.

10, another embodiment of the main control flow in the measuring device will be described. Control flow of various data setting (80a) that sets the data necessary for device operation such as address setting, earth leakage alarm setting value, alarm output use, communication method, etc. using the same method as switch or keyboard. And performing a control flow of the leakage current measurement 80b that reads the digital value corresponding to the converted leakage current of the two analog / digital converters 16b and 16c, and the amplification degree for f1 Hz and f2 Hz as described above, The control flow of the leakage current calculation 70c for calculating the leakage current for the magnitude of the low frequency signal voltage or the inter-phase AC phase voltage of the commercial frequency is executed. Here, it may be converted into a leakage current or insulation resistance value with respect to the signal voltage of the low frequency component of f1 Hz, and may be converted into a leakage current or insulation resistance value with respect to the signal voltage of the low frequency component of f2 Hz, It can be converted into leakage current for AC phase voltage (50Hz or 60Hz) or converted into insulation resistance value.Earth Leakage Alarm Setting Value that judges whether the calculated leakage current value is larger than the earth leakage alarm setting value or the insulation resistance value is smaller than the earth leakage alarm setting value. If the leakage current is greater than the earth leakage alarm set value by executing the control flow of abnormality (80d), the control flow of the alarm output (80e) that performs the alarm output is executed and various data (device address, leakage) to the monitoring room according to the communication method. The control flow of various data transmissions 80f is executed to the monitoring room for communicating current value or insulation resistance value). Even if the leakage current value is smaller than the earth leakage alarm setting value, the monitoring room communicates various data (device address, leakage current value, insulation resistance value, etc.) to the monitoring room according to the communication method, so that the monitoring room can identify the accurate leakage location or the earth leakage section. The control flow of the transmission 80f is executed. After the control flow of the various data transmissions 80f is executed in the monitoring room, the control flow returns to the control flow of the leakage current measurement 80b again.

By the control flow of the various data transmissions 70d to the monitoring room of FIG. 9 or the control flow of the various data transmissions 80f to the monitoring room of FIG. 10, the various data in the measuring device are an embodiment of the RS-232 or RS-485 communication method. When the transmission to the CPU 61 through the communication unit 67 of the control device 60 of the remote monitoring room in accordance with the communication method as shown in FIG. The location or the short circuit section is determined and determined. FIG. 14 illustrates an embodiment of the earth leakage section determination result of the present invention according to the earth leakage position of the result of executing the control flow of FIG. 13 and 14, which will be described next, have been described in detail in the above-described third embodiment and will not be described in this embodiment. The third embodiment differs from the third embodiment in that the third embodiment detects the leakage current of the low frequency component and the leakage current of the commercial frequency line and calculates the effect of the reactive leakage current independent of the leakage current flowing through the capacitance C. Although the magnitude of the AC phase voltage and the frequency change of the commercial frequency vary depending on the site conditions, there is some error in the effective leakage current or the value of the insulation resistance R. In this case, the effects of capacitance C are removed by calculation by amplifying and detecting both kinds of low-frequency leakage currents (known) of frequency magnitude and signal voltage magnitude. The fourth embodiment has higher accuracy than the third embodiment in detecting an effective leakage current due to the insulation resistance R which is directly related to the leakage current.

Although the technical spirit of the present invention has been described above with reference to the accompanying drawings, it is intended to illustrate the most preferred embodiment of the present invention by way of example and not to limit the present invention. In addition, anyone of ordinary skill in the art, such as a current / voltage conversion unit, an amplifier, a band pass filter, an analog / digital conversion unit in the leakage current detection unit without departing from the technical scope of the present invention It is obvious that various modifications and imitations are possible and by various methods such as increase, decrease, change of position, mutual combination and flow of control unit of measuring device and control device of monitoring room.

Therefore, as described above, in a device for detecting and detecting a short circuit position or a short circuit section of a low voltage cable in a live state without interrupting the low voltage cable line, when there are a plurality of short circuits, the occurrence of a short circuit may be judged even if there is no short circuit. Compared to the conventional method in which a short circuit is occurring, the present invention provides an accurate information to an administrator so that it is possible to accurately determine a short circuit section to promptly remove a short circuit power supply, thereby decisively contributing to the prevention of a safety accident due to a short circuit.

Claims (4)

A low frequency superposition device that overlaps a signal voltage of a low frequency component provided between a neutral point of a low voltage side of a transformer or a one-point ground line and an earth ground in a live state in a live state;  In the measuring device installed in each section of the place such as manhole or cavity, the leakage current flowing to the ground by the commercial frequency AC voltage and the low-frequency signal voltage superimposed by the low frequency superposition device are detected. Calculate leakage current or insulation resistance value of insulation resistance component directly related to leakage current through conversion and amplification of leakage current of component into voltage component, commercial frequency and low frequency filtering, and analog / digital conversion process.  This leakage current or insulation resistance value is transmitted and received to the control unit of the remote monitoring room through various communication methods, In the remote control device, the leakage current or insulation resistance value is read by the number of measuring devices, and the difference of leakage current value (or insulation resistance value) between the devices adjacent to the installation site or the order of all devices installed from the load side in the order of all devices installed from the transformer side. As a result, when the installation location determines the difference in leakage current value (or insulation resistance value) between adjacent devices, when the leakage current value of n places is greater than the leakage current value of n + 1 place from the transformer side, or n When the insulation resistance value of the place is less than the n + 1 insulation resistance value, the n and n + 1 sections are displayed as an earth leakage section or an alarm output is generated or the leakage current value of n places from the load side is n + 1 place. When the leakage current is smaller than the leakage current setting value, or the insulation resistance at n places is less than the insulation resistance at n + 1. If the value is above the set value, the n and n + 1 sections are displayed as a short circuit section or generate an alarm output.If the leakage current of the measuring device closest to the load side is more than the earth leakage alarm set value or the insulation resistance value is below the earth leakage alarm set value, An earth leakage position detecting system for a low voltage cable line in a live state, wherein a section is displayed as an earth leakage section or generates an alarm output. A low frequency superposition device that overlaps a signal voltage of a low frequency component provided between a neutral point of a low voltage side of a transformer or a one-point ground line and an earth ground in a live state in a live state;  A measuring device installed at each section of a place such as a manhole or a hollow sphere detects a leakage current flowing to the earth by a signal voltage of a low frequency component superimposed by the low frequency overlapping device, and converts and amplifies the leakage current of the low frequency component into a voltage component. And leakage frequency or insulation resistance value through low frequency band pass filter and analog / digital conversion process.  This leakage current or insulation resistance value is transmitted and received to the control unit of the remote monitoring room through various communication methods, In the remote control device, the leakage current or insulation resistance value is read by the number of measuring devices, and the difference of leakage current value (or insulation resistance value) between the devices adjacent to the installation site or the order of all devices installed from the load side in the order of all devices installed from the transformer side. When the installation location determines the difference in leakage current value (or insulation resistance value) between adjacent devices, the leakage current value of n places from the transformer side is greater than the leakage current value of n + 1 places, or When the insulation resistance value of n place is less than the n + 1 insulation resistance value, the n and n + 1 sections are displayed as an earth leakage section or an alarm output is generated, or the leakage current value of n places from the load side is n + 1. When the leakage current alarm value is smaller than the leakage current value at the place or the insulation resistance value at n places is less than the insulation resistance value at n + 1 places If the value is above the set value, the n and n + 1 sections are displayed as a short circuit section or generate an alarm output.If the leakage current of the measuring device closest to the load side is more than the earth leakage alarm set value or the insulation resistance value is below the earth leakage alarm set value, An earth leakage position detecting system for a low voltage cable line in a live state, wherein a section is displayed as an earth leakage section or generates an alarm output. In a live system of low voltage lines in a live state, a measuring device installed at each section of a place such as a manhole or a hollow hole detects only a leakage current flowing by an AC voltage of a commercial frequency, and converts and amplifies the leakage current of the commercial frequency component into a voltage component. And leakage frequency or insulation resistance through commercial band pass filter and analog / digital conversion process.  This leakage current or insulation resistance value is transmitted and received to the control unit of the remote monitoring room through various communication methods, In the remote control device, the leakage current or insulation resistance value is read by the number of measuring devices, and the difference of leakage current value (or insulation resistance value) between the devices adjacent to the installation site or the order of all devices installed from the load side in the order of all devices installed from the transformer side. As a result, when the installation location determines the difference in leakage current value (or insulation resistance value) between adjacent devices, when the leakage current value of n places is greater than the leakage current value of n + 1 place from the transformer side, or n When the insulation resistance value of the place is less than the n + 1 insulation resistance value, the n and n + 1 sections are displayed as an earth leakage section or an alarm output is generated or the leakage current value of n places from the load side is n + 1 place. If the leakage current is smaller than the leakage current value of the leakage current value or the insulation resistance of n places is less than the insulation resistance of n + 1 places If the value is above the set value, the n and n + 1 sections are displayed as a short circuit section or generate an alarm output.If the leakage current of the measuring device closest to the load side is more than the earth leakage alarm set value or the insulation resistance value is less than the earth leakage alarm set value, n and the load An earth leakage position detecting system for a low voltage cable line in a live state, wherein a section is displayed as an earth leakage section or generates an alarm output. A low frequency superposition device that overlaps the signal voltages of two kinds of low frequency components (f1 Hz, f2 Hz) which are installed on the low voltage line of the transformer between the neutral point or the one-point ground line and the ground ground in the live state;  The measuring device installed in each section of a place such as a manhole or a hollow sphere detects leakage current flowing to the ground by the superimposed signal voltage of the low frequency of f1 Hz and leakage current flowing to the ground by the superimposed signal voltage of the low frequency of f2 Hz. Leakage current or insulation resistance value of insulation resistance component directly related to leakage current by converting and amplifying the leakage current of low frequency component of these two components into voltage component, f1 Hz and f2 Hz low frequency band filtering and analog / digital conversion process And calculate  This leakage current or insulation resistance value is transmitted and received to the control unit of the remote monitoring room through various communication methods, In the remote control device, the leakage current or insulation resistance value is read by the number of measuring devices, and the difference of leakage current value (or insulation resistance value) between the devices adjacent to the installation site or the order of all devices installed from the load side in the order of all devices installed from the transformer side. As a result, when the installation location determines the difference in leakage current value (or insulation resistance value) between adjacent devices, when the leakage current value of n places is greater than the leakage current value of n + 1 place from the transformer side, or n When the insulation resistance value of the place is less than the n + 1 insulation resistance value, the n and n + 1 sections are displayed as an earth leakage section or an alarm output is generated or the leakage current value of n places from the load side is n + 1 place. If the leakage current is smaller than the leakage current value of the leakage current value or the insulation resistance of n places is less than the insulation resistance of n + 1 places If it is over the set value, n or n + 1 section is displayed as a short circuit section or an alarm output is generated.If the leakage current of the measuring device closest to the load side is more than the earth leakage alarm set value or the insulation resistance value is below the earth leakage alarm set value, n and the load section An earth leakage position detection system for a low voltage cable line in a live state, characterized by generating an alarm or an alarm output in a short circuit section.

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