Monitoring method of power line for distribution automation system

Abstract

The distribution line monitoring method of the present invention may include: a step of acquiring voltage and current measurement values ​​on a distribution line; a step of determining whether the distribution line is disconnected based on the voltage and current measurement values ​​on the distribution line and taking action; a step of provisionally determining a defect in a voltage measuring device based on the voltage and current measurement values ​​on the distribution line; a step of finally determining a defect in a voltage measuring device if the voltage and current measurement values ​​serving as the basis for the provisional determination of the defect in the voltage measuring device are maintained for a predetermined set time; a step of resetting if the voltage and current measurement values ​​serving as the basis are not maintained for a predetermined set time; and a step of transmitting the determination result of whether the voltage measuring device is defective to an upper server that controls protection devices provided on the distribution line.

Description

Technology Field

[0001] The present invention relates to a distribution line monitoring method for a distribution automation system that detects open circuits / phase loss on a distribution line, wherein the method is capable of distinguishing between a detection signal caused by a malfunction of a voltage measuring device detecting voltage and a detection signal caused by an open circuit as a basis for detecting open circuits / phase loss. Background Technology

[0003] Generally, substations convert transmission voltage transmitted through transmission lines into distribution voltage and supply the converted distribution voltage to consumers through distribution lines. For example, transmission voltages such as 154kV or 345kV transmitted through transmission lines are converted to a distribution voltage of 22.9kV at the substation and distributed to consumers through distribution lines.

[0004] Meanwhile, the Distribution Automation System (DAS) monitors the operational status of the distribution system in real time by acquiring field information on distribution facilities and lines from Distribution Automation Terminal Units (FRTUs) developed by incorporating advanced IT technology, and providing this information to the main unit via wired or wireless communication. In particular, the Distribution Automation System has the advantage of rapidly identifying fault sections in the distribution network, while simultaneously shortening power outage times and reducing the fault area through remote control, thereby ensuring a stable power supply.

[0005] In distribution automation systems utilizing multi-grounding, if a high-resistance ground fault caused by a broken wire is not detected, rapid situation detection and shutdown are not performed, posing a risk of electric shock or cascading accidents. To prevent such risks in advance, sensors measuring voltage and current are installed on the distribution lines, and an algorithm is executed to determine the break or phase failure on the distribution lines based on the signals measured by these sensors.

[0006] FIG. 1 is a conceptual diagram illustrating an algorithm for detecting open circuits / losses in power distribution lines according to the prior art.

[0007] FIG. 2 is a conceptual diagram illustrating an algorithm for detecting open circuits / losses in power distribution lines according to improved conventional technology.

[0008] The algorithm shown in Figure 1 utilizes only low-precision voltage measurements, which increases the likelihood of errors in detecting open circuits or phase failures and lacks sufficient reliability. Consequently, it is difficult to apply it for automation systems such as DAS operation.

[0009] In the case of the algorithm of Fig. 2, which solves the problem of low reliability of the algorithm of Fig. 1, by applying additional high-precision current values, the possibility of error in detecting open circuits / phase failures is close to 'ZERO', resulting in improved reliability. Therefore, it can provide a stable foundation for DAS operation.

[0010] When the improved algorithm of Fig. 2 is applied, open circuit / phase loss error information can be eliminated, but it becomes impossible to identify defects in the automation equipment itself, particularly voltage measurement failures caused by voltage measuring devices (e.g., PT), and this may have an adverse effect on the automation system, such as the failure to generate FI. Prior art literature

[0012] Republic of Korea Registered Publication No. 10-1287627, Registered, Distribution Line Break Detection System The problem to be solved

[0013] The present invention aims to provide a distribution line monitoring method for a distribution automation system capable of distinguishing between a detection signal caused by a voltage measuring device failure and a detection signal caused by a disconnection in a system for detecting disconnections / phase loss on a distribution line to establish a stable foundation for DAS operation. means of solving the problem

[0015] A method for monitoring a power distribution line according to one aspect of the present invention may include: acquiring voltage and current measurements on a power distribution line; determining whether the power distribution line is disconnected based on the voltage and current measurements on the power distribution line and taking action; provisionally determining a defect in a voltage measuring device based on the voltage and current measurements on the power distribution line; finally determining a defect in a voltage measuring device if the voltage and current measurements serving as the basis for the provisional determination of the defect in the voltage measuring device are maintained for a predetermined set time; resetting if the voltage and current measurements serving as the basis are not maintained for a predetermined set time; and transmitting the determination result of whether the voltage measuring device is defective to an upper server that controls protection devices provided on the power distribution line.

[0016] Here, the method may further include a step of controlling the opening and closing of protective devices provided in the distribution line according to the result of determining whether the line is disconnected.

[0017] Here, the method may further include a step of notifying the person in charge of the voltage measuring device based on the result of determining whether the voltage measuring device is defective.

[0019] A distribution automation system according to another aspect of the present invention may include: a switch body having mechanical components and analog signal processing components for performing switching operations to protect a distribution system; a switch control device having components as a protection and signal receiving circuit and a digital operation device for the switch body; a DAS server that finally acquires various measurement information of a distribution system including a voltage measuring device and directs the operation of protection devices of the distribution system according to the result of analyzing the information; and an FRTU that collects measurement information regarding the switch body and transmits it to the DAS server, and transmits a control signal from the DAS server to the switch control device, and checks whether the voltage measuring device is defective based on the voltage and current measurement values ​​on the distribution line of the distribution system and the maintenance time of each measurement value.

[0020] Here, the FRTU can determine whether there is a disconnection from the voltage and current measurements on the distribution line and transmit the result of determining whether there is a disconnection and the result of determining whether the voltage measuring device is defective to the DAS server.

[0021] Here, the voltage measuring device may be a CVD (Condenser Voltage Detector) device.

[0022] A power distribution line monitoring device according to another aspect of the present invention may include: a power distribution line measurement value acquisition unit for acquiring voltage and current measurement values ​​on a power distribution line; a disconnection determination unit for determining whether a line is disconnected from the voltage and current measurement values ​​on the power distribution line; a measuring device determination unit for determining whether a voltage measuring device is defective from the voltage and current measurement values ​​on the power distribution line and the maintenance time of each measurement value; and a communication unit for transmitting the result of determining whether a line is disconnected and the result of determining whether a voltage measuring device is defective to an upper server that controls protection devices provided on the power distribution line.

[0023] Here, a display unit may be further included to display the result of determining whether the voltage measuring device is defective to the outside.

[0024] Here, a distribution line control unit that controls protective devices provided in the distribution line may be further included.

[0025] Here, the power distribution line control unit can control the switch of the power distribution line according to the control signal of the upper server received through the communication unit, or control the switch according to the open circuit determination of the open circuit determination unit.

[0026] Here, a storage unit may be further included for temporarily storing data to be transmitted to the upper server and for temporarily storing data received from the upper server.

[0027] Here, the measuring instrument determination unit may perform a method for monitoring a distribution line measuring instrument, comprising: a step of provisionally determining a defect in the voltage measuring instrument from voltage and current measurement values ​​on the distribution line; a step of finally determining a defect in the voltage measuring instrument if the voltage and current measurement values ​​serving as the basis for the provisional determination of the defect in the voltage measuring instrument are maintained for a predetermined set time; and a step of resetting if the voltage and current measurement values ​​serving as the basis are not maintained for a predetermined set time. Effects of the invention

[0029] By implementing a distribution line monitoring method for a distribution automation system according to the concept of the present invention with the above-described configuration, in a system for detecting open circuits / phase loss on a distribution line, it is possible to distinguish between a detection signal caused by a failure of a voltage measuring device and a detection signal caused by an open circuit, thereby providing the advantage of establishing a stable foundation for DAS operation.

[0030] The distribution line monitoring method for the distribution automation system of the present invention has the advantage of improving the reliability, maintenance, and efficiency of the distribution automation system.

[0031] Specifically, the distribution line monitoring method for the distribution automation system of the present invention can improve the reliability of the improved algorithm by separately processing open circuit / phase loss and voltage measurement failure alarms, and can improve maintenance efficiency by enabling the detection of voltage measurement failures caused by automation failures themselves. Brief explanation of the drawing

[0033] FIG. 1 is a conceptual diagram illustrating an algorithm for detecting open circuits / phase loss in power distribution lines according to the prior art. FIG. 2 is a conceptual diagram illustrating an algorithm for detecting open circuits / phase loss in power distribution lines according to improved conventional technology. FIG. 3 is a block diagram illustrating a data transmission structure from a general switchgear to a DAS server in which a power distribution line monitoring method according to the concept of the present invention can be performed. FIG. 4 is a flowchart illustrating an embodiment of a power distribution line monitoring device in which a power distribution line monitoring algorithm according to the concept of the present invention is performed. FIG. 5 is a conceptual diagram illustrating an algorithm for determining whether a voltage measuring device is defective according to the concept of the present invention, which can be performed together with the detection of open circuit / phase loss in a power distribution line. FIG. 6 is a flowchart illustrating an embodiment of a distribution line monitoring method that performs an algorithm for determining whether a voltage measuring device is defective according to the concept of the present invention described above. FIG. 7 is a flowchart showing the process of detecting a power distribution line disconnection (abnormality) by the disconnection determination unit of the present invention. Specific details for implementing the invention

[0034] In describing the present invention, terms such as "first," "second," etc., may be used to describe various components, but the components may not be limited by these terms. The terms are intended solely to distinguish one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component.

[0035] When it is mentioned that a component is connected to or coupled with another component, it can be understood that it may be directly connected to or coupled with that other component, or that there may be other components in between.

[0036] The terms used in this specification are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions may include plural expressions unless the context clearly indicates otherwise.

[0037] In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0038] In addition, the shapes and sizes of elements in the drawings may be exaggerated for clearer explanation.

[0040] FIG. 3 is a block diagram illustrating a data transmission structure from a general switchgear to a DAS server in which a power distribution line monitoring method according to the concept of the present invention can be performed.

[0041] Figure 3 shows a self-fault notification switch configured according to the concept of the present invention in accordance with the installation structure of a ground switch, and can be seen as illustrating the operation of a distribution automation (intelligence) system.

[0042] The distribution line monitoring method / device according to the concept of the present invention can be easily applied by adding an algorithm (i.e., software) that performs a distribution line monitoring method to an existing automation system.

[0043] The opening / closing confirmation unit (26) of the main body (20) of the switch (20) performs the function of confirming the closing or opening state of the switch (20). To elaborate, the switch (20) is in a combined form with a switching means. When a movable contact (not shown) moves by the switching means and comes into contact with a fixed contact (not shown), the same electrode terminals are electrically connected as a closing operation by the operating unit (28). Conversely, when the movable contact is separated from the fixed contact, the electrical connection between the same electrode terminals is released as an opening operation. The switching means may be a thermal relay, a solenoid, etc.

[0044] If the illustrated switchgear body (20) defines the mechanical components and analog signal processing components in the switchgear, the illustrated switchgear control device (40) defines the components as various protection circuits and digital operation devices in the switchgear.

[0045] The intelligent terminal device (60) in the city performs a function as a gateway, such as collecting various sensing / measurement information from the switch and transmitting it to the intelligent system (DAS) (80), and transmitting control signals from the intelligent system (DAS) (80) to the switch.

[0046] The above intelligent terminal device (60) is advantageously implemented in the form of a FRTU (Feeder Remote Terminal Unit: distribution automation terminal device), but is not limited thereto, and in other implementations, it may be implemented in the form of an AMI (Advanced metering Infrastructure) device.

[0047] The DAS server (80) in the city manages the distribution automation system and ultimately acquires various sensing / measurement information of the distribution system. Since it is equipped with sufficient hardware to process information in various ways, theoretically, almost all methods of processing sensing / measurement information of the distribution system can be performed.

[0048] However, while the intelligent terminal device (60) is installed at a site where a switch is installed, the DAS server (80) is installed at a remote location for management, and due to the communication interval, delay time, and transmission error handling between the intelligent terminal device (60) and the DAS server (80), the immediacy of processing sensing / measurement information of the power distribution system is reduced.

[0050] FIG. 4 is a flowchart illustrating an embodiment of a power distribution line monitoring device in which a power distribution line monitoring algorithm according to the concept of the present invention is performed.

[0051] A power distribution line monitoring device (600) may include: a power distribution line measurement value acquisition unit (610) for acquiring voltage and current measurement values ​​on a power distribution line; a disconnection determination unit (630) for determining whether a disconnection has occurred from the voltage and current measurement values ​​on the power distribution line; a measuring device determination unit (620) for determining whether a voltage measuring device (e.g., PT) is defective from the voltage and current measurement values ​​on the power distribution line and the maintenance time of each measurement value; and a communication unit (680) for transmitting the voltage and current measurement values ​​on the power distribution line, which are accumulated and collected over a predetermined period or a predetermined number of times, to an upper server that controls protection devices equipped on the power distribution line, and transmitting the result of determining whether a disconnection has occurred and the result of determining whether the voltage measuring device is defective to the upper server.

[0052] Depending on the implementation, the power distribution line monitoring device (600) may further include a display unit (670) that displays the result of determining whether the voltage measuring device is defective to the outside; and / or a power distribution line control unit (640) that controls protection devices provided in the power distribution line.

[0054] The above distribution line measurement value acquisition unit (610) can be implemented by dividing it into the voltage measurement unit (61) and the current measurement unit (62) of FIG. 3, and is connected to the corresponding receiving / protection circuits (41, 42) of the switchgear control device (40) to collect voltage (v) and current (i) as measurement values ​​of the PT (21) and CT (22) mounted on the switchgear body (20). Depending on the implementation, the above distribution line measurement value acquisition unit (610) may be composed of IC (Integrated Circuit) chips, etc. to collect signals. It may further be equipped with components for analog-to-digital signal conversion / processing, such as a DSP (Digital Signal Processor) and memory.

[0055] The above-mentioned open circuit detection unit (630) performs the function of detecting an abnormality in the power distribution line using a digital value signal and generating it as alarm information. To this end, the above-mentioned open circuit detection unit (630) may be composed of a microprocessor, memory, etc.

[0056] The above-mentioned open circuit determination unit (630) can determine open circuits / phase failures of the wiring line according to various algorithms including known technologies. Specific methods for determining open circuits / phase failures will be exemplified later.

[0058] The communication unit (680) transmits measurement (measurement) data, alarm information, status check information confirming the open / closed status of the switch (20), etc., to the DAS server (130). To this end, the communication unit (680) may be configured to include a modem, circuit elements, etc., and wired / wireless connection to the modem is also possible.

[0060] Depending on the implementation, the display unit (670) may output only whether the voltage measuring device is defective, or may also output the result of the wire breakage determination unit (630).

[0061] In the latter case, the display unit (670) performs the function of displaying alarm information, and for this purpose, it may be composed of a display, a warning light, a sound system, etc. Accordingly, the alarm information can be a combination of graphics, text, and voice.

[0062] In the case of the former, it can be composed of at least three LEDs for three phases so as to indicate only the failure of the voltage measuring device for each phase of the switch in charge.

[0064] Although not shown, the storage unit may further include a storage unit for temporarily storing data to be transmitted to the DAS server (80) and for temporarily storing data received from the DAS server (80). For example, the storage unit may store measurement (measurement) data, alarm information, and status check information of the switch (20). Depending on the implementation, the storage unit may also store configuration information for an administrator to operate the switch or the intelligent terminal device (FRTU, 60).

[0066] The urban power distribution line control unit (640) can control the switch of the power distribution line according to the control signal of the upper server (80) received through the communication unit (680), or control the switch according to the disconnection determination of the disconnection determination unit (630).

[0067] The method by which the above-mentioned power distribution line control unit (640) controls the switch can be applied by directly sending an on / off signal to the switch or by transmitting a control instruction to a driving means such as a switch control device (40).

[0068] The power distribution line monitoring device (600) of FIG. 4 may be implemented in the form of internal HW and / or SW blocks of an intelligent terminal device (60) (i.e., FRTU) in the power distribution automation system structure shown in FIG. 3, or as components distributed between the intelligent terminal device (60) and the switchgear control device (40). The former case is advantageous in terms of management responsibility and convenience of maintenance.

[0070] Next, we will examine the function and operation of the above-mentioned measuring instrument judgment unit (620).

[0071] FIG. 5 is a conceptual diagram illustrating an algorithm for determining whether a voltage measuring device is defective according to the concept of the present invention, which can be performed together with the detection of open circuits / losses in power distribution lines.

[0072] The algorithm described above is intended for detecting voltage measurement failures caused by defects in automated devices or voltage measuring instruments themselves, and can be used to generate a self-diagnosis abnormality alarm when a voltage measuring instrument fails.

[0073] As described above, the voltage measuring instrument defect is determined by applying the current value level, the voltage value level, and the time for which a specific condition is maintained as an AND condition.

[0074] A fault determination method based on an AND condition of the current level, voltage level, and the time a specific condition is maintained is particularly useful for CVD (Condenser Voltage Detector) type PTs. This is because although CVD offers excellent sensing performance relative to cost, there is a high probability of errors occurring due to rapid temperature increases that may occur in power distribution systems.

[0075] For example, as described above, if a condition is detected where the current ON LEVEL is 4A or higher and the voltage OFF LEVEL is 6,600V or lower, and this condition is maintained for 10 seconds or longer as a predetermined set time, the described algorithm may output a self-diagnosis abnormality alarm. In this case, the details of the self-diagnosis abnormality alarm are voltage measurement failure.

[0076] To elaborate on each of the exemplified conditions, for the current, 4A was applied as the current ON LEVEL threshold value specified for the distribution output terminal of the relevant distribution site in the construction document, etc., and for the voltage, 6,600V was applied as the voltage OFF LEVEL threshold value, which is half the normal voltage (13,200V) of the distribution output terminal of the relevant distribution site specified in the construction document, etc. The setting time for the above holding time can be determined according to the type of PT as a voltage measuring device and / or the characteristics of the relevant distribution site, and in the case of a CVD type PT, it is advantageous to set it between 8 sec and 12 sec, but in the illustrated example, it was determined to be 10 sec.

[0078] FIG. 6 is a flowchart illustrating an embodiment of a distribution line monitoring method that performs an algorithm to determine whether a voltage measuring device is defective according to the concept of the present invention described above.

[0079] A method for monitoring a distribution line described above may include: a step of acquiring voltage and current measurements on a distribution line (S110); a step of determining whether the distribution line is disconnected based on the voltage and current measurements on the distribution line and taking action (S200); a step of provisionally determining a defect in a voltage measuring device based on the voltage and current measurements on the distribution line (S140); a step of finally determining a defect in a voltage measuring device if the voltage and current measurements serving as the basis for the provisional determination of the defect in the voltage measuring device are maintained for a predetermined set time (S160); a step of resetting if the voltage and current measurements serving as the basis are not maintained for a predetermined set time; and a step of transmitting the result of determining whether the line is disconnected and / or the result of determining whether the voltage measuring device is defective to an upper server that controls protection devices provided on the distribution line (S300).

[0080] Depending on the device in which the urban power distribution line monitoring method is performed, the opening and closing of protective devices (switches) equipped on the power distribution line can be controlled according to the result of determining whether the line is disconnected in step S200.

[0081] Depending on the implementation, the method may further include a step of notifying the person in charge of the voltage measuring device or displaying the result of determining whether the voltage measuring device is defective in step S160 to the outside of the device where the illustrated power distribution line monitoring method is performed.

[0083] Among the steps constituting the method for monitoring a distribution line, the step of acquiring voltage and current measurements on the distribution line (S110) is performed by the distribution line measurement acquisition unit (610) of FIG. 4, and the step of determining whether the distribution line is disconnected and taking action (S200) can be performed by the disconnection determination unit (630).

[0084] The measuring instrument judgment unit (620) of FIG. 4 may perform a step (S140) of provisionally determining a defect in the voltage measuring instrument from the voltage and current measurements on the distribution line of FIG. 6; a step (S160) of finally determining a defect in the voltage measuring instrument if the voltage and current measurements that serve as the basis for the provisional determination of the defect in the voltage measuring instrument are maintained for a predetermined set time; and a step of resetting if the voltage and current measurements that serve as the basis are not maintained for a predetermined set time, and these processes can be defined as a method for monitoring a distribution line measuring instrument.

[0086] Next, I will exemplify one of the algorithms for implementing the step (S200) of determining whether the distribution line of FIG. 6 is disconnected and taking action, which is performed by the disconnection determination unit (630) of FIG. 4.

[0087] FIG. 7 is a flowchart showing the process of detecting a power distribution line disconnection (anomaly) by the disconnection determination unit of the present invention. Referring to FIG. 7, current (i) and voltage (v) are measured simultaneously through the measurement unit (S210-1, S210-2).

[0088] Afterwards, check whether the respective detected values ​​(I, V) of the current (i) and voltage (v) are zero (0) (S220-1, S220-2).

[0089] Upon verification, if each detected value is not zero, it is checked whether the detected value is less than or equal to a preset reference value (S230-1, S230-2). To elaborate, the current detected value (I) is compared with a preset reference value 1 (i phase off level), and if the current detected value (I) is less than or equal to the reference value 1 (i off level), the process proceeds to step S230-2 (S230-1).

[0090] The voltage detection value (V) is compared with a preset reference value 2 (v phase off level). If the voltage detection value (V) is less than or equal to the reference value 2, the detection holding time (off time) is compared with a preset setting value (S230-2, S250). To elaborate, the detection time refers to the time during which the state of the detection value is maintained. The setting value can be approximately 3 seconds. For the voltage and current to satisfy the criteria and for an alarm to be triggered, the detection holding time must be 4 seconds.

[0091] In step S250, if the detection holding time (off time) is smaller than a preset value, proceed to the 'open circuit / phase loss' release step (S271). An open circuit indicates a state where the lines are not connected to each other. A phase loss is a case where the circuit of one of the three phases is open, indicating a state where no voltage is produced in one of the three phases.

[0092] In contrast, if the detection holding time (off time) in step S250 is greater than the set value, the three-phase voltage (V 3-PHASE) is compared with a preset reference value 3 (S230). To elaborate, the three-phase voltage (V 3-PHASE ) can be expressed as in the following mathematical formula 1.

[0093]

[0094] Here, V: voltage detection value representing the magnitude of the measured voltage transmitted from the switch.

[0095] I: Current detection value representing the magnitude of the measured current transmitted from the switch

[0096] v phase off level: Voltage reference value set to determine voltage loss (less than 50% of the distribution system phase voltage of 13,200V)

[0097] i off level: Current reference value set to determine current loss (0) (current less than 4A based on the dead line reference current in the power distribution automation system)

[0098] Off time: The time required to maintain state detection so that voltage and current satisfy reference conditions and generate alarm information (approx. 4 seconds)

[0099] + : AND condition

[0100] Therefore, in step S260, the three-phase voltage (V 3-PHASE If ) is greater than the preset threshold value 3, alarm information is generated as 'open circuit / phase loss' has occurred (S272).

[0101] Meanwhile, in steps S220-1 and S220-2, if the detection value (V,I) is 0, the 'open circuit / loss' alarm information is released (S271).

[0102] Additionally, after a 'short circuit / phase loss' alarm occurs, the alarm information is released when one or more of the following conditions are met (S240-1, S240-2).

[0103] ① V > v phase off level

[0104] ② I > i off level

[0105] To elaborate, the determination of a 'short circuit / phase loss' alarm is satisfied when the phase voltage V is below the Phase Off Level, the phase current is below 4A, and the set time is exceeded.

[0106] Meanwhile, the decision to clear the 'open circuit / loss of phase' alarm is to satisfy the condition that the phase voltage V exceeds the Phase On Level or the phase current exceeds 5A.

[0108] Those skilled in the art to which the present invention pertains should understand that the present invention may be implemented in other specific forms without altering its technical concept or essential features, and therefore the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims set forth below rather than by the detailed description, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention. Explanation of the symbols

[0110] 600: Distribution line monitoring device 610: Distribution line measurement value acquisition unit 620: Measuring instrument judgment unit 630: Open circuit judgment unit 640: Distribution line control unit 670: Display unit 680 : Communications Department

Claims

Claim 1 A step of acquiring voltage and current measurements on a power distribution line; a step of determining whether the power distribution line is disconnected based on the voltage and current measurements on the power distribution line and taking action; a step of provisionally determining a defect in a voltage measuring device based on the voltage and current measurements on the power distribution line; a step of finally determining a defect in a voltage measuring device if the voltage and current measurements serving as the basis for the provisional determination of the defect in the voltage measuring device are maintained for a predetermined set time; a step of resetting if the voltage and current measurements serving as the basis are not maintained for a predetermined set time. A method for monitoring a power distribution line, comprising the step of transmitting a determination result of whether the voltage measuring device is defective to an upper server that controls protective devices provided in the power distribution line, wherein in the step of determining whether the power distribution line is disconnected and taking action, the current measurement value (I) is compared with a preset reference value 1 (i phase off level) and if the current measurement value (I) is less than or equal to the reference value 1 (i off level), the voltage measurement value (V) is compared with a preset reference value 2 (v phase off level) and if the voltage measurement value (V) is less than or equal to the reference value 2, the detection holding time (off time) is compared with a preset setting value and if the detection holding time (off time) is greater than the setting value, the three-phase voltage (V3-PHASE) is compared with a preset reference value 3 and if the three-phase voltage (V3-PHASE) is greater than the preset reference value 3, alarm information is generated indicating that 'disconnection / phase loss' has occurred. Claim 2 A distribution line monitoring method according to claim 1, further comprising the step of controlling the opening and closing of protective devices provided in the distribution line according to the result of determining whether the line is disconnected. Claim 3 A distribution line monitoring method according to claim 1, further comprising the step of notifying the person in charge of the voltage measuring device based on the result of determining whether the voltage measuring device is defective.

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