KR100697947B1 - On-Line Pinpointing Method of Electric Leakage for Low Voltage Power Cable - Google Patents

Abstract

 The present invention relates to a method for accurately detecting a ground fault position in a live state of an underground low-voltage power line, and the probe power is applied to both ends of the ground fault section by overlapping a specific frequency power source other than the commercial frequency, and the ground fault section is centered on the ground fault point. The galvanometer is divided into two micro-resistance elements, two resistances divided by a standard variable resistor as known resistance elements, and a Wheatstone bridge circuit for connecting a galvanometer to a grounded earth circuit. Underground live voltage short circuit of the low voltage power line characterized in that it is possible to calculate the split ratio by the ground fault point of the ground fault section based on the divided resistance ratio of the variable resistor at the position where the variable resistor is adjusted so that the guideline is "0". Location exploration method.

 Low voltage power line, leakage point, variable resistor, galvanometer, voltage amplifier, diode, filter

Description

 On-line Pinpointing Method of Electric Leakage for Low Voltage Power Cable}

 FIG. 1 shows the ground fault point 111 when a ground current occurs with a ground resistance value of RG at a point A and B of AC 220 [V] 60 [Hz] low voltage power lines 101, 102 and 103. One exemplary embodiment for measuring the position

 FIG. 2 shows the exemplary diagram of FIG. 1 as a simple equivalent circuit.

 3 is an exemplary view schematically showing the configuration of the electronic circuit of the probe.

  Considering the safety of urban aesthetics, facilities, and human resources, power line neutralization is underway in many areas, and is expanding. In the underground area, low-voltage electric power lines are laid underground, but until now, management has been neglected compared to special high-voltage electric power lines. In addition, streetlight cables in urban areas are buried underground, so they should be managed like ordinary power lines. In this way, if a short circuit occurs in a city road that is easily accessible to citizens, there is a high risk of a safety accident if a short circuit occurs. Therefore, a ground fault point 111 is immediately found when a short circuit is prevented or a short circuit is confirmed. And repair it.

 There is always a risk of ground stress due to tension stress on ground subsidence and damage caused by excavation work that occurs frequently, and a short circuit due to poor construction and deterioration due to long-term use.

 Conventionally, in order to search for an earth leakage point or an earth leakage section, the low voltage power line is blacked out to isolate the connection point for each section with an insulation resistance meter and to check the insulation resistance by checking the insulation resistance, or to check the magnitude of the leakage current by following the wire path with a leakage ammeter. As a result, a method of determining a short circuit section has been used. However, these methods are effective in detecting the leakage section, but they cannot pinpoint the location of the leakage. Therefore, in the event of a short circuit of the underground cable, the location of the short circuit could not be pinpointed due to the invisibility and the lack of suitable equipment. Therefore, it was necessary to replace the cable that suspected a short circuit or to excavate and repair the location of the short circuit. .

  Therefore, countermeasures against electric shock accidents caused by leakage of underground low-voltage power lines are essential. In order to recover the leakage of underground lines, it is necessary to reduce the construction cost and prevent civil complaints by minimizing excavation by checking the exact leakage position. The probes developed so far can be used in a power outage, but if the exploration time takes several hours, the inconvenience of customers and the sales of electricity are reduced.

 In the patent information search, three patent registrations and one utility model application were searched for a ground fault location device. Most of them were invented or devised for the purpose of exploring the leakage point of street lamp line, especially two cases (Publication No. 10-2005-0002945, Method of checking the street lamp line using power line communication and its device, Publication No. 20-0401899, Live wire In the state, the earth leakage position detection system of the low voltage line was detected to detect an earth leakage section or an earth leakage circuit. However, two registered patents (overlapping pulse signal generator and detection signal output device for detecting a short circuit position by 10-0463450 street light cable, earth leakage point detection device and method) are applied to the power line. The detection of the voltage drop between the probes caused by the return current of the pulse current using a detection frame or probe. These two registered patents can be said to be similar to the object of the present invention.

 However, the two registered patents are very low in feasibility. That is, the principle of the ground fault detection of the two patents is to detect the potential difference (staged voltage) between the probes due to the voltage drop occurring in the feedback circuit of the ground current to the power supply side. , How much will flow to the surface of the concrete).

 The present invention was devised to solve the above-mentioned problems, and the exploration power is applied to both ends of the earth leakage section by overlapping a specific frequency power source other than the commercial frequency, and divides the earth leakage section around the earth leakage point to provide two minute values. By setting up a resistance element, using two resistances divided by a standard variable resistor as a known resistance element, and configuring a Wheatstone bridge circuit connecting a galvanometer to a grounded earth circuit, It is a technical object of the present invention to be able to calculate the split ratio by the short-circuit point of the earth leakage section by the resistance ratio divided by the variable resistor at the position where the variable resistor is adjusted to be ”.

 Live state leakage point detection method of the underground low-voltage power line of the present invention, the detection power is applied to both ends of the earth leakage section by overlapping a specific frequency power source other than the commercial frequency, the earth leakage point 111 Is divided into two micro-resistance elements, and two resistances divided by standard variable resistors are known resistance elements, and a Wheatstone bridge circuit connects a galvanometer to a grounded earth circuit. Thus, the split ratio by the ground fault point 111 of the ground fault section can be calculated by the divided resistance ratio of the variable resistor at the position where the variable resistor is adjusted so that the guide of the galvanometer becomes "0". 1 to 3 will be described in detail below.

 FIG. 1 shows the ground fault point 111 when a ground current occurs with a ground resistance value of RG at a point A and B of AC 220 [V] 60 [Hz] low voltage power lines 101, 102 and 103. One exemplary embodiment for measuring the position. The non-commercial frequency oscillator is connected to the A and B sections, and other frequencies other than the commercial frequency are superimposed and input to the A and B sections of the low-voltage power line, and the input non-commercial frequency power passes through the ground fault ground point 106 and the ground electrode ( 107), but the circuit is connected to the regression circuit, and the galvanometer 108 and the variable resistor 109 are connected to each other, and then the indication of the galvanometer 108 becomes "0" through adjustment of the variable resistor 109. By adjusting, the ratio of the RL1 102 and RL2 103 can be known according to the divided ratio of the variable resistor 109. In order to make accurate measurements, when measuring at the terminal of point A, the length of the lead wire 104 from the probe to the point A and the length of the lead wire 105 from the probe to the point B are the same so that an error occurs due to the difference in the length of the lead wire. Eliminate

 FIG. 2 shows a simple equivalent circuit of the exemplary diagram of FIG. 1, which is a typical Wheatstone bridge circuit. In the circuit, if "R1 + R2 = constant value" and known resistance where the value of R1 and R2 can be known at the variable position, RL1 and RL2 are unknown resistance, but the indication of galvanometer is "0". In this case, since "RL1 x R2 = RL2 x R1" is established, the ratio between the values of RL1 and RL2 can be calculated. And the diode inserted in the galvanometer circuit is to rectify the alternating current.

 3 is an exemplary view schematically showing the configuration of the electronic circuit of the probe.

   AC 220 [V] 60 [Hz] Low voltage power line 201 Connects a specific non-commercial frequency oscillator 205 to the earth leakage section and applies it to the low voltage power line leakage section by overlapping a specific frequency other than the commercial frequency. It passes through the sensing resistor 207 in the probe through the power supply circuit, the ground contact point 203 and the ground contact point 204 of the probe from the ground fault point 202, and is connected to the variable resistor 206 for earth leakage position discrimination. A sensing circuit for acquiring a sensing value of the resistor 207 and a sensed value appear between the A and B terminals. The sensing value is minute and is amplified by the voltage amplifier 209 and displayed on the LCD display 217. It is an exemplary view composed of a logic circuit up to the process.

 The signal amplified by the voltage amplifier 209 passes through a filtering unit 210 for filtering and inputting only a specific frequency signal, that is, a specific frequency signal oscillated from the oscillator 205, and the filtered voltage is diode 211. The rectified voltage is converted into a digital value by the analog / digital converter 212, and the converted digital value is input to the I / O port of the central processing unit 215 for processing.

  Sensing value of the sensing resistor 207 → voltage amplifier 209 → filtering unit 210 → diode 211 → Analog / Digital Converter 212 → CPU 215 ) Is processed and stored in accordance with the arithmetic function of) and the pre-programmed logic expression.

   AC servo motor or DC servo motor may be used to precisely control the mechanical movement amount of the variable resistor 206. However, in the present task, it is advantageous to control the angle cheaply and precisely, in particular, digitally controlled by pulse. A stepping motor 208 that can be used is applied. The stepping motor 208 is configured to operate in accordance with the command of the CPU 215. When the stepping motor 208 receives a command of 1 pulse from the CPU 215, it rotates about 0.6 degrees.

 The central processing unit (CPU) 215 controls a whole system of the ground fault position detecting device, and has a built-in program that tracks the position of the ground fault point 111 to indicate an accurate position. In addition, the ROM 218 has a function of storing an operating program of the CPU 215 nonvolatile so that the analysis program is not erased even when the system power is turned off. It is a kind of communication port where you can enter or start command of device.

 One embodiment of the program: At the site to find the earth leakage position, connect the probe to both ends of the earth leakage section and the ground terminal with lead wires, enter the distance between the earth leakage sections, and press the start button of the probe. ) Will perform all operations of the probe itself. That is, the stepping motor 208 is commanded to scan each position of the variable resistor 206 one by one, storing and comparing the input values by the sensing values of the sensing resistor 207, and comparing the above three times. As the repetition is repeated, the position of the earth leakage point 111 analyzed for each repetition number is compared to display the final judgment.

 The exclusion of DC power as the power source for detecting the leakage position is caused by malfunction because the DC power is used in anti-static facilities installed in other infrastructures. Therefore, in this problem, it is assumed that a specific non-commercial frequency oscillator 205 is used.

As described above, the live-circuit earth leakage point detection method of the underground low-voltage power line of the present invention, compared to the conventional method of replacing the cable when the earth leakage occurs in the underground voltage power line, economical repair to find the exact earth leakage position and repair only the corresponding earth leakage portion By providing a method, material and time losses can be greatly reduced. In addition, the utility has the effect of reducing the outage time for repairing a short circuit, thereby improving customer service and reducing power sales.

Claims (1)

  In the method of accurately searching the earth leakage position in the live state of the underground low voltage power line, the detection power supply 110 is applied to both ends of the earth leakage section AB by overlapping a specific frequency power source other than the commercial frequency, and the earth leakage section AB is applied. The resistance is divided into two micro-resistive elements RL1 and RL2 by dividing the leakage point 111 as a center, and the two resistances divided by the variable resistor 109 are converted into known resistance elements R1 and R2. And the galvanometer 108 of the Wheatstone bridge is connected to a circuit which is shorted at the ground fault point 111 and returned to the power supply through the ground circuits 106 and 107, and the two micro-resistance elements RL1 and RL2 described above. And RL1 and R2 and RL2 and R1 symmetrically connected to each other in the Wheatstone bridge circuit among the above known resistance elements R1 and R2, and the guide of the galvanometer 108 is " 0 " Divided resistance ratio of the variable resistor at the position where the variable resistor 109 is adjusted so that Hot-line state leakage location sensing method by the low pressure underground power line, characterized in that to calculate the dividing ratio by the short-circuit point 111 by the ratio of R1 and R2 shorted period (AB), to be able to determine the short-circuit position.

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