Method for measuring fault characteristics when AC induced voltage is generated in a power transmission line, and its use.

Abstract

This invention provides a method for measuring fault patterns when AC induced voltage is generated in a power transmission line, and its use. [Solution] A DC voltage is applied to a power transmission line where AC induced voltage is generated, and the applied DC voltage and current are measured. Based on the resistance value of the power transmission line calculated from these values, the fault pattern of the power transmission line is determined.

Description

[Technical Field]

[0001] This invention relates to a method for measuring fault characteristics when an AC induced voltage is generated in a power transmission line, and to its use. [Background technology]

[0002] Underground power transmission lines utilize three-phase AC underground transmission cables, a standard method used in general power systems, with three independent cables laid as a set. The cables are insulated to protect the power system from external environmental factors and ground faults. However, damage to this insulation or deterioration over time can cause ground faults, leading to power outages. Additionally, induced currents from other cables (live lines) can interfere with fault measurements and the operation of measuring equipment. When a fault occurs in an underground power transmission line, unlike overhead equipment, the fault cannot be visually inspected because it is buried underground, making it difficult to pinpoint the location of the fault. However, due to the difficulty in identifying the fault location, replacing the entire transmission line including the faulty section would be prohibitively expensive and time-consuming. Therefore, there is a need for technology that can electrically identify the fault location instead of visually inspecting it, and replace only the minimum necessary section.

[0003] Various techniques are used to measure fault locations in underground power transmission lines, depending on the type of fault. These include the Murray loop method, pulse reflection method, acoustic method, and high-voltage test method. The appropriate method must be selected based on the type of fault (such as open circuit, ground fault, or short circuit) and the environment in which the power lines are installed. In underground power transmission lines, ground faults are often caused by insulation breakdown due to deterioration or damage to the cable's insulation. In such cases, the Murray loop method is often used to pinpoint the fault location by forming a loop between the faulty phase and the healthy phase cables and measuring the voltage and current distribution. The Murray loop method involves constructing a loop circuit with a faulty phase cable of a three-phase AC system and a healthy single-phase cable (healthy phase cable) that is not experiencing a ground fault. A DC voltage is then applied to the loop circuit to measure the location of the ground fault in the faulty phase cable. The Murray loop method exhibits high accuracy when the conductor resistance of the cables is uniform and break resistance can be ignored.

[0004] However, if the fault in an underground power transmission line is an open circuit, attempting to measure the fault point using the Murray loop method carries the risk that the measured value will deviate significantly from the actual distance if the resistance to the open circuit is very high. For example, 77kV 80mm 2 It has been shown that when measuring the fault point of a high-voltage underground power transmission line cable with a conductor resistance of 0.233 Ω / km and a break resistance of 100 MΩ, the Murray loop method results in a large error in the measurement (Figure 5). Further details will be provided.

[0005] In the Murray loop method, the distance X to the fault point is calculated using the following formula. X = 2 × Vb / (Va + Vb) × L • X: Distance to the point of failure • L: Total length of the cable (one-way length in the case of a reciprocating loop) Vb: Voltage drop in healthy phase, Va: Voltage drop in faulty phase The voltage drop V follows Ohm's law. V=I×R I: Current flowing through the loop • R: Resistance in the loop Therefore, when a break in the circuit is added, the loop resistance increases, which in turn changes the voltage drop ratio and causes a large error in the distance calculation.

[0006] Let's look at the details below. Assuming the wire break resistance is 100MΩ, Resistance of healthy phase: Rb = 0.233 × 4 = 0.932Ω Fault phase resistance: Ra = 0.233 × 2 = 0.466Ω Total loop resistance (including open circuit resistance): R = Ra + Rb + Disconnection Resistance = 0.466 + 0.932 + 100M ≈ 100MΩ

[0007] Effect of voltage drop ratio The Murray loop method calculates the distance to the fault point based on the voltage drop ratio Vb / (Vb+Va) within the loop. However, this ratio can change drastically due to the influence of open circuit resistance. • Voltage drop in a healthy phase (Vb) Because the resistance of the healthy phase is 0.932Ω, the voltage drop is: Vb = I × Rb • Voltage drop (Va) across the faulty phase Since the resistance of the faulty phase is 0.466Ω + 100MΩ ≈ 100MΩ, the voltage drop is: Va = I × Ra • Voltage drop ratio Vb / (Vb+Va)=0.932 / (0.932+100M)≒0

[0008] If the total loop length L is 4 km one way, the distance X to the point of failure is as follows: X=2×Vb / (Vb+Va)×L=2×0×4=0km As a result, the location of the fault may be calculated to be much shorter than the actual distance (2 km), or in extreme cases, the fault may be considered to be extremely far away.

[0009] Therefore, in order to determine the fault location measurement method when an underground power transmission line fails, understanding the fault pattern is extremely important. To understand the fault pattern, the resistance value of the transmission line is measured using a tester, and from that resistance value, the presence or absence of a break in the wire is checked to determine a fault location measurement method suitable for the fault pattern, such as the Murray loop method. However, if an AC induced voltage is generated from an operating circuit running alongside the underground power transmission line, the tester's measurement value becomes unstable, making it impossible to read the resistance value of the transmission line. For this reason, when an AC induced voltage is present in the underground power transmission line, it is difficult to understand the fault pattern, such as the presence or absence of a break in the wire (Figure 1).

[0010] The invention of Patent Document 1 is a power supply device for energizing a cable fault point measuring instrument equipped with an AC / DC converter that applies a DC voltage to a cable to be measured for a fault point. It has a power protection circuit that prevents alternating current induced current from a live cable other than the cable to be measured for a fault point from flowing backward into the AC / DC converter, and a load resistance circuit that consumes the induced current blocked by the power protection circuit. A voltage limiter circuit limits the abnormal rise of the output DC voltage of the AC / DC converter due to the influence of the induced voltage, protecting the fault point measuring instrument and stabilizing the fault point measurement operation, and discloses a power supply device for energizing a cable fault point measuring instrument.

[0011] However, when measuring the fault point of a cable using the Murray loop method, the invention of Patent Document 1 aims to suppress the influence of the alternating current induced voltage and measure the fault point by applying a low DC voltage of 6V even when an alternating current induced voltage is generated in the cable. Moreover, since the applied DC voltage is as low as 6V, it is easily affected by the induced voltage. To reduce this influence, a power protection circuit, a load resistance circuit that consumes the induced current, etc. are provided to protect the fault point measuring instrument and stabilize the fault point measurement operation. The invention of Patent Document 1 did not apply a DC voltage for selecting a fault point measurement method. Therefore, when applied to an open circuit fault that cannot be measured by the Murray loop method, there is a possibility of a large error in the measurement result of the fault point.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0013] The present invention has as its problem a method for measuring a fault condition such as an open circuit when an alternating current induced voltage is generated in a transmission line and its use.

Means for Solving the Problems

[0014] The inventors discovered that applying a DC voltage within a predetermined range to the cable is a means of eliminating the influence of AC induced voltage, which interferes with the measurement of fault characteristics. In other words, the present invention was made to solve the above-mentioned problems, and the inventors have found that by applying a DC voltage within a predetermined range to the circuit under measurement in an underground power transmission line where AC induced voltage is generated, it is possible to determine whether or not there is a break in the wire based on the resistance value measured without being affected by the AC induced voltage, and have completed the present invention. Embodiments of the present invention may include the following configurations. [1] A method for measuring the fault pattern of a transmission line, comprising the following steps, for determining the fault pattern of a pair of three-phase AC transmission lines where the fault pattern is unknown and an AC induced voltage is generated, by applying a DC voltage to the fault pattern of the transmission line; (1) Connecting one end of each of the pair of three-phase AC transmission lines, and applying a DC voltage within a predetermined range to the other end of the pair of transmission lines, (2) A step of measuring the DC voltage generated in the power transmission line to which the voltage is applied. (3) A step of measuring the DC current flowing through the power transmission line to which the current has been applied. (4) A step of calculating the resistance value of the pair of transmission lines based on the DC voltage generated in the pair of transmission lines obtained from step (2) and the DC current flowing through the pair of transmission lines obtained from step (3), (5) A step of generating a determination result of the fault pattern of the pair of transmission lines from the resistance values ​​of the pair of transmission lines. [2] The method for measuring fault patterns of a power transmission line according to claim 1, characterized in that the DC voltage in the predetermined range is a DC voltage in the range of 10V to 1000V. [3] The method for measuring the fault pattern of a power transmission line according to [1], wherein if the fault pattern determination result generated in step (5) is determined to be a fault pattern to which Murray loop measurement can be applied for measuring the distance to the fault point, and the length of the pair of power transmission lines is unknown, the method further includes the step of measuring the length of the power transmission lines by Murray loop measurement using two phases of the pair of power transmission lines: a healthy power transmission line and another healthy power transmission line corresponding to the healthy power transmission line. [4] The method for measuring the fault pattern of a power transmission line as described in [1], wherein if the fault pattern determination result generated in step (5) is determined to be a fault pattern to which Murray loop measurement can be applied for measuring the distance to the fault point, and a power supply ground wire for preventing relay malfunction of the power receiving equipment is used for measuring the distance to the fault point, the method further includes the step of measuring the length of the power supply ground wire by Murray loop measurement. [5] A transmission line fault phase measuring device for performing the fault phase measuring method for transmission lines described in [1] or [2], comprising: a voltage supply unit for connecting one end of each of the pair of three-phase AC transmission lines that are generating AC induced voltages and for applying a DC voltage within a predetermined range to the other end of the pair of transmission lines; a voltage measuring unit for measuring the DC voltage generated in the pair of transmission lines; a current measuring unit for measuring the DC current flowing through the pair of transmission lines; a calculation unit for calculating the resistance value of the pair of transmission lines based on the DC voltage generated in the pair of transmission lines obtained from the voltage measuring unit and the DC current flowing through the pair of transmission lines obtained from the current measuring unit; and a determination unit for generating a fault phase determination result of the transmission line from the resistance value of the pair of transmission lines calculated by the calculation unit. [6] A fault phase measuring device for performing the fault phase measuring method described in [1] or [2], characterized in that the voltage supply unit applies the DC voltage variably in the range of 10V to 1000V, as described in claim 5. [Effects of the Invention]

[0015] According to the present invention, even when induced voltage is generated in the power transmission line, the fault pattern can be accurately grasped, and a fault location measurement method suitable for the fault pattern can be selected, thereby enabling rapid and accurate measurement of the fault location. [Brief explanation of the drawing]

[0016] [Figure 1] Block diagram showing the failure mode determination flow. [Figure 2] Block diagram showing the method for measuring failure patterns. [Figure 3] Circuit diagram showing the method for measuring the failure pattern of Embodiment 1 [Figure 4] Circuit diagram illustrating the demonstration method for measuring the failure pattern of Embodiment 1. [Figure 5] Conceptual diagram showing the failure pattern in Embodiment 1 when the wire is disconnected. [Figure 6] Conceptual diagram showing the measurement method for failure patterns and failure locations in Embodiment 2 [Figure 7] Conceptual diagram showing the measurement method for failure patterns and failure locations in Embodiment 3 [Modes for carrying out the invention]

[0017] Preferred embodiments of the present invention will be described in detail below. <First Embodiment>

[0018] When measuring the fault location in underground power transmission lines, the Murray loop method has a large margin of error when the fault is a break in the wire, making it difficult to accurately pinpoint the fault location. Therefore, before measuring the fault location, it is necessary to first understand the nature of the fault, such as whether or not there is a break in the wire. However, various live wires may be buried underground along with the power transmission lines, and ultra-high voltage power transmission lines may be suspended overhead. In such cases, AC induced voltage is generated in the power transmission line being measured, making it difficult to measure the fault characteristics. Therefore, it is necessary to apply a DC voltage to the power transmission line to eliminate the influence of AC induced voltage and accurately measure the fault characteristics.

[0019] This invention has been made in view of the above circumstances, and its purpose is to provide a method and apparatus for measuring fault characteristics, such as the presence or absence of a break in a wire, using a simple method, even when an AC induced voltage is generated in an underground power transmission line. Hereinafter, embodiments of the present invention will be described based on the drawings.

[0020] <Fault pattern measurement device 1> Figure 3 shows the circuit configuration of the failure pattern measuring device 1 according to the present invention. The fault phase measurement device 1 includes a DC power supply DC applied to a pair of fault phase cables 2a and healthy phase cables 2b of the circuit L under measurement, a voltmeter V1 for measuring the voltage of the DC power supply DC, a voltmeter V0 for measuring the DC voltage applied to the circuit L under measurement, an ammeter A0 for measuring the DC current flowing through the circuit L under measurement, and a fixed resistor R for protecting the circuit of the fault phase measurement device 1. All of these components can be commercially available.

[0021] As shown in Figure 3, the fault phase measurement device 1 forms a loop circuit by connecting the far ends of a pair of cables consisting of the fault phase 2a and healthy phase 2b of the circuit to be measured L, and a DC voltage within a predetermined range is applied from the measurement terminal of the circuit to be measured L where the AC induced voltage ε is generated, by the DC power supply DC of the fault phase measurement device 1.

[0022] <Method for measuring the presence or absence of a break in underground power transmission lines when AC induced voltage is present> Figures 2 and 3 show a method for measuring the fault pattern when an induced voltage ε is generated in an underground power transmission line, which is a first embodiment of the present invention.

[0023] In step (hereinafter referred to as "S") 101, the far ends of a pair of cables consisting of the faulty phase 2a and the healthy phase 2b of a three-phase AC transmission line are connected to form a loop circuit, and a DC voltage within a predetermined range is applied from the measurement terminal of the circuit L under measurement where the AC induced voltage ε is generated by the DC power supply DC of the fault phase measurement device 1.

[0024] The DC voltage applied by the DC power supply DC of the fault phase measurement device 1 is measured by the voltmeter V1 of the fault phase measurement device 1. In addition, the voltage of the DC current flowing through the circuit under measurement L is measured by the voltmeter V0, and the current is measured by the ammeter A0. (Note that in this specification, the voltage measured by voltmeter V1 may be denoted as V1V, and the voltage measured by voltmeter V0 may be denoted as V0V.) If the DC voltage V0V applied to the circuit under measurement L is greater than the AC induced voltage ε of the circuit under measurement L, the measured DC voltage V1V is not affected by the induced voltage ε. The DC voltage V1V is not limited as long as it is greater than the induced voltage ε. Specifically, it is preferably between 10V and 1000V, and more preferably between 10V and 600V.

[0025] Next, the DC voltage V0V generated in the circuit L under measurement by applying the DC voltage V1V is measured (S102).

[0026] Furthermore, by applying a DC voltage V1V, the DC current IA flowing through the circuit L under measurement is measured (S103).

[0027] Unlike AC voltage, DC voltage does not fluctuate in value. Therefore, the voltage V0V and DC current IA of the DC current flowing through the circuit L under measurement can be determined using an instrument connected to the fault phase measurement device 1. From the measurement results, the resistance value Rx of the circuit L under measurement can be determined using Ohm's law. In other words, based on the voltage V0V of the DC current flowing through the circuit L to be measured and the value of the DC current IA flowing through the circuit L to be measured obtained in S103, the resistance value Rx of the circuit L to be measured can be calculated using formula (1) (S104).

[0028] Rx = V0V / IA ... (1)

[0029] Next, a determination result for the fault pattern of the circuit L is generated from the resistance value Rx of the circuit L obtained in S104 (S105). The generated determination result can be exemplified in Table 2, but is not limited to this.

[0030] <Verification Results> To verify the effectiveness of the measurement method of the present invention, the following experiment was conducted. Experiments confirmed that the resistance value Rx of the circuit L under measurement can be determined by equation (1), as shown in Figures 2 and 3. The circuit L under measurement is a 77kV 80mm cable commonly used in underground power transmission cables. 2 This was used, but is not limited to this. For power transmission cables, 50mm 2 ~400mm 2 That's fine too. In the experiment, as shown in Figure 4, a variable resistor Rf was attached to the circuit L under measurement as a simulated fault point, and measurements were performed using the fault pattern measurement device 1. This confirmed that the measurement method of the present invention is applicable under various conditions. The outline and results of the experiment are shown below.

[0031] The fault phase measurement device 1 consists of a DC power supply DC, a voltmeter V1 that measures the DC voltage supplied from the DC power supply DC, a voltmeter V0 that measures the voltage of the DC current flowing through the circuit L under measurement, and an ammeter A0 that measures the DC current flowing through the circuit L under measurement, and further includes a fixed resistor R. Including the fixed resistor R (for example, 100Ω) is preferable because it protects the circuit L under measurement and sets a basic measurement reference point. The fixed resistor R is for protecting the circuit of the fault phase measurement device 1, and its value can be changed as appropriate. The fixed resistor R can be a commercially available one.

[0032] The circuit L under measurement is formed by connecting the far ends of a pair of cables consisting of a faulty phase 2a and a healthy phase 2b to create a loop circuit, and a variable resistor Rf is installed in the loop to simulate a fault point within the circuit L. The fault phase measurement device 1 can reproduce a simulated fault point in the circuit L by adjusting the value of the variable resistor Rf in the circuit L under measurement. This makes it possible to experimentally perform measurements under various conditions.

[0033] To reproduce the point of failure, the actual measurement conditions were simulated by adjusting the resistance value of the variable resistor Rf.

[0034] The applied DC voltage was measured using voltmeter V1. The resistance value RxΩ of the circuit L under test could be calculated from the voltage V0V measured by voltmeter V0 and the current IA measured by ammeter A0 using formula (1). Experiments were conducted by applying DC voltages of 10V, 50V, and 100V to the circuit L under test. The induced AC voltage at this time was 2.6V.

[0035] The simulation results are shown in Table 1. [Table 1]

[0036] Despite the presence of AC induced voltage, it was confirmed that the variable resistance value Rf and the line resistance value Rx of the circuit L being measured in the transmission line were equivalent. Conventionally, when AC induced voltage was generated in the transmission line, the value shown by the tester was unstable due to the influence of the AC induced voltage, making it impossible to determine the resistance value Rx of the circuit L being measured in the transmission line, and thus it took time to identify the fault pattern of the transmission line. However, by using the measurement method and fault pattern measuring device 1 of the present invention, fault patterns such as wire breaks can be measured quickly, and the method for measuring the fault point according to the fault pattern can be rapidly determined.

[0037] The fault pattern can be determined from the resistance value Rx of the circuit L measured by the method according to the present invention, and the fault patterns shown in Table 2 can be determined. By accurately understanding the fault pattern, a measurement method suitable for the fault location can be selected. The resistance value Rx of the circuit L and the fault patterns shown in Table 2 are examples and are not limited thereto. [Table 2] <Second Embodiment>

[0038] <In the present invention, when the fault pattern is determined to be one that can be measured by Murray loop measurement, and the length of the circuit to be measured is unknown, the fault pattern measurement method includes the step of measuring the length of the circuit to be measured from two healthy phases.> This section describes a method for identifying the fault location using the Murray loop method when the fault pattern is determined to be one that can be measured by Murray loop measurement using the fault pattern measurement method of the first embodiment of the present invention, and the fault location is within the boundaries of the power company's customer, that is, when the power company does not know the length of the transmission line.

[0039] (Structure and Method) The overall configuration of the fault pattern measurement method according to this embodiment is the same as that shown in Figure 3, so no further explanation is provided. This embodiment differs from the first embodiment in that the underground power transmission line is an underground power transmission line managed by a customer of the power company, and includes a step to determine the length of the underground power transmission line managed by the customer when its length is unknown. Otherwise, it is identical to the first embodiment. Even if the configuration and method shown in Figure 3 allow for measurement of the fault pattern of an underground power transmission line within a customer's premises using the Murray loop method, if the length of the underground power transmission line within the premises is unknown, the location of the fault cannot be determined using the Murray loop method. According to this embodiment, as shown in Figure 6, the length of the customer's premises cable L can be measured using a Murray loop measuring instrument and a temporary wire a whose length is known. First, as shown in Step 1 of Figure 6, a loop circuit is constructed by connecting the healthy phases of the customer's premises cable L, whose length is unknown, with a temporary wire a whose length is known, and a temporary fault point is established. Then, a Murray loop measurement is performed. Since the length of the connected temporary wire a is known, the length of the customer's premises cable L, whose length is unknown, can be calculated from the measurement results. Next, as shown in Step 2 of Figure 6, the distance to the actual fault point can be determined using the length of the customer's premises cable L obtained in this way.

[0040] <Verification Results> To verify the effectiveness of the measurement method of the present invention, the following experiment was conducted. As shown in Fig. 6, in the experiment, a temporary wire a of known length was looped around a customer premises cable L of unknown length (xm), and a temporary fault point was set at the connection point between the temporary wire a and the customer premises cable L. It was confirmed that the length of the customer premises cable L could be calculated by the Murray loop method. The temporary wire a used for the customer premises cable L was 2.0 mm 2 to 22.0 mm 2 commonly used for underground power transmission cables, but it is not limited to this. It is the IV line and can withstand a measurement voltage of 10 kV In the experiment, by using a temporary wire a of 2.0 mm 2 to 22.0 mm 2 and a length of 0.5 m to 2.5 m, a simulated fault point was set between the customer premises cable L and the temporary wire a, and measurements were taken by the Murray loop method. It was demonstrated that even if the length of the customer premises cable L was unknown, the fault point could be identified. The outline and results of the experiment are shown below

Table 3

[0041] ​<In the present invention, when the fault pattern is determined to be a fault pattern that can be measured by Murray loop measurement, and a power supply ground wire is used to prevent relay malfunction, the fault phase measurement method includes the step of measuring the length of the power supply ground wire from two healthy phases.> To ensure a safe and stable power supply to high-rise buildings and commercial facilities in urban areas, high-voltage switchgear, such as gas-insulated switchgear (hereinafter also referred to as "GIS"), is installed in substation facilities. As shown in Figure 7, a power supply ground wire X is provided in the GIS to ensure the stability of the power supply system from overvoltage and ground faults. To avoid the risk of a complete power outage at the facility, the measurement of fault locations in the GIS must be performed via the power supply ground wire X. However, the length of the power supply ground wire X is often unknown, making it difficult to measure fault locations in the transmission lines of the GIS. This section describes a method for identifying the fault location using the Murray loop method when the fault pattern is determined to be one that can be measured by Murray loop measurement using the fault pattern measurement method of the first embodiment of the present invention, and when the length of the power supply ground wire X is unknown when measuring the fault point in the GIS.

[0042] (Structure and Method) The overall configuration of the fault phase measurement method according to this embodiment is the same as that shown in Figure 3, so no further explanation is provided. This embodiment differs from the first embodiment in that the underground power transmission line is an underground power transmission line managed by a customer of the power company, and includes a step to determine the length of the power supply ground wire X managed by the customer when the length of the X is unknown. Otherwise, it is identical to the first embodiment. Even if the configuration and method shown in Figure 3 allow for measurement of the fault pattern of an underground power transmission line within a customer's premises using the Murray loop method, if the length of the power supply ground wire X within the premises is unknown, the location of the fault cannot be determined using the Murray loop method. According to this embodiment, the length of the cable L, including the power supply ground wire X, can be measured using a Murray loop measuring instrument and a temporary wire a whose length is known.

[0043] According to this embodiment, the length of the power supply ground wire X, whose length is unknown, can be measured using a Murray loop measuring instrument and a temporary wire a whose length is known. First, as shown in Step 1 of Figure 7, a loop circuit is constructed by connecting the healthy phases of the power supply ground wire X (of unknown length) and cable L (of known length) with a temporary wire a (of known length), and a temporary fault point is set between one end of the power supply ground wire X and temporary wire a. Then, a Murray loop measurement is performed. Since the lengths of the connected cable L and temporary wire a are known, the length of the power supply ground wire X (of unknown length) can be calculated from the measurement results. Next, as shown in Step 2 of Figure 7, the distance to the actual fault point can be determined using the length of the power supply ground wire X obtained in this way.

[0044] <Verification Results> To verify the effectiveness of the measurement method of the present invention, the following experiment was conducted. As shown in Figure 7, the experiment involved connecting a temporary wire a of known length to a customer premises cable L, whose length is known, in a loop shape using a power supply ground wire X of unknown length. By creating a temporary fault point at the connection point between the power supply ground wire X and the temporary wire a, it was confirmed that the length of the power supply ground wire X could be calculated using the Murray loop method. The power supply ground wire X was a 22mm IV wire, which is commonly used as a power supply ground. 2 While this was used, it is not limited to this. Any IV wire capable of withstanding a measurement voltage of 10kV will suffice. In the experiment, the size was 0.3 mm. 2 ~2.0mm 2 By using a temporary wire a with a length of 0.5m to 10.0m to create a simulated fault point between the power supply ground wire X and the temporary wire a, and performing measurements using the Murray loop method, it was demonstrated that the fault point can be identified even if the length of the power supply ground wire X is unknown. The outline and results of the experiment are shown below. [Table 4] Size: 0.3mm 2 ~2.0mm 2When a temporary wire a with a length of 0.5m to 10.0m was connected and measured using the Murray loop method, the measurement error compared to the actual measurement of the power supply ground wire X was within 0.48m to 1.80m, and the size was 2.0mm. 2 Within the length range of 0.5m to 10.0m, the measurement error with the actual measurement of the power supply ground wire X was within 0.48m to 1.29m, confirming its effectiveness in identifying fault points in lines of unknown length, including the power supply ground wire X.

[0045] It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. [Explanation of symbols]

[0046] 1. Failure pattern measuring device V1...A voltmeter for measuring the voltage of a DC power supply. V0... A voltmeter that measures the applied DC voltage. A0... An ammeter that measures the direct current flowing through the circuit being measured. I... The current flowing through the circuit under measurement due to the application of a DC voltage. L... Circuit and cable to be measured. F...Failure location ε···Induced voltage Rf... Variable resistance value Rx... Resistance value a... Temporary power lines X...Power supply ground wire

Claims

1. A method for measuring the fault pattern of a transmission line, characterized by including the following steps, which involves applying a DC voltage to a pair of three-phase AC transmission lines where the fault pattern is unknown and an AC induced voltage is generated, in order to determine the fault pattern of the transmission line; (1) Connecting one end of each of the pair of three-phase AC transmission lines, and applying a DC voltage within a predetermined range to the other end of the pair of transmission lines, (2) A step of measuring the DC voltage generated in the power transmission line to which the voltage has been applied. (3) A step of measuring the DC current flowing through the power transmission line to which the current has been applied. (4) A step of calculating the resistance value of the pair of transmission lines based on the DC voltage generated in the pair of transmission lines obtained from step (2) and the DC current flowing through the pair of transmission lines obtained from step (3), (5) A step of generating a determination result of the fault pattern of the power transmission line from the resistance values ​​of the pair of power transmission lines.

2. The method for measuring fault patterns in a power transmission line according to claim 1, characterized in that the DC voltage in the predetermined range is a DC voltage in the range of 10V to 1000V.

3. A method for measuring the fault pattern of a power transmission line according to claim 1, wherein if the fault pattern determination result generated in step (5) is determined to be a fault pattern to which Murray loop measurement can be applied for measuring the distance to the fault point, and the length of the pair of power transmission lines is unknown, the method further includes the step of measuring the length of the power transmission lines by Murray loop measurement using two phases of the pair of power transmission lines: a healthy power transmission line and another healthy power transmission line corresponding to the healthy power transmission line.

4. A method for measuring the fault pattern of a power transmission line according to claim 1, wherein, when the fault pattern determination result generated in step (5) is determined to be a fault pattern to which Murray loop measurement can be applied for measuring the distance to the fault point, if a power supply ground wire for preventing relay malfunction of the power receiving equipment is used to measure the distance to the fault point, the method further includes a step of measuring the length of the power supply ground wire by Murray loop measurement.

5. A power transmission line fault phase measuring device for performing the power transmission line fault phase measuring method described in claim 1 or 2, A voltage supply unit for connecting one end of each of the pair of three-phase AC transmission lines that generate AC induced voltages, and for applying a DC voltage within a predetermined range to the other end of the pair of transmission lines, A voltage measuring unit for measuring the DC voltage generated in the pair of power transmission lines, A current measuring unit for measuring the DC current flowing through the pair of power transmission lines, A calculation unit calculates the resistance value of the pair of transmission lines based on the DC voltage generated in the pair of transmission lines obtained from the voltage measurement unit and the DC current flowing through the pair of transmission lines obtained from the current measurement unit, A determination unit that generates a determination result of the fault pattern of the transmission line from the resistance values ​​of the pair of transmission lines calculated by the calculation unit, A device for measuring the fault pattern of a power transmission line, characterized by including [a specific feature].

6. A failure pattern measuring device for performing the failure pattern measuring method described in claim 1 or 2, The power transmission line fault phase measuring device according to claim 5, characterized in that the voltage supply unit variably applies the DC voltage in the range of 10V to 1000V.

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