KR20210143551A - Apparatus and method for detecting fault point location in transmission line - Google Patents

Abstract

An embodiment of the present invention relates to a device for detecting a location of a fault point in a transmission line, and a method thereof. The device for detecting a location of a fault point includes: a plurality of fault waveform acquisition units for acquiring bus voltage waveforms and line current waveforms measured at both ends of a fault line in which a fault occurs among the parallel lines, and a line current measured in a sound line in which the fault does not occur among the parallel lines as fault waveforms; a synchronization unit for synchronizing the fault waveforms; a fundamental wave component acquisition unit for acquiring fundamental wave components from the fault waveforms synchronized by the synchronizing unit; and a fault point determination unit for determining a location of a fault point of the fault line based on the fundamental wave components. Accordingly, the present invention can improve accuracy of detecting the location of the fault point in a power transmission line including parallel lines.

Description

Fault point location detection device and method in power transmission line

An embodiment of the present invention relates to an apparatus and method for detecting a location of a fault point in a power transmission line, and more particularly, to an apparatus and method for detecting a location of a fault point in a power transmission line including parallel lines.

In general, transmission line failure is mainly caused by natural disasters such as lightning strikes and strong winds. Estimating the exact location of the failure, that is, the failure point, when a failure occurs in the transmission line is very important for the person in charge of the transmission operation to identify the cause of the failure and perform a prompt repair work accordingly.

Protection relays located in substations at both ends of the transmission line detect the fault point and type of fault in the event of a line failure, and open the circuit breaker of the corresponding line, thereby quickly separating the faulty line from the system. As a method of searching for a fault point in a power transmission line, a method using voltage and current information obtained from at least one substation among both ends of the fault line may be used. In this method, the fault point in the transmission line is detected by calculating the impedance using the voltage and current obtained from the substation, and estimating the distance to the fault point by applying the calculated impedance to a predetermined function.

In a transmission line composed of parallel lines, electromagnetic inductive coupling exists between the parallel lines. For this reason, in a transmission line in which two lines are parallel, when a ground fault occurs in one line, an induced voltage is generated in the faulty line due to the current in the other line that is healthy. In this way, the induced voltage generated in the faulty line is combined with a voltage drop due to the line impedance of the faulty line to reduce the accuracy of voltage and current measured at substations at both ends of the faulty line, and as a result, the fault point detection accuracy act as a cause of dropping

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus and method for detecting a point of failure in which the accuracy of detecting a location of a point of failure in a power transmission line including parallel lines is improved.

According to an aspect of the present invention for solving the above problems, there is provided an apparatus for detecting a location of a failure point in a power transmission line. The fault point position detection device includes bus voltage waveforms and line current waveforms measured at both ends of the faulty line among the parallel lines included in the power transmission line, and the line current waveforms in which the fault does not occur among the parallel lines. A plurality of fault waveform acquisition units for acquiring a line current measured in a sound line as fault waveforms, a synchronization unit for synchronizing the fault waveforms, and a fundamental wave for acquiring fundamental wave components from the fault waveforms synchronized by the synchronization unit It may include a component acquisition unit, and a failure point determination unit for determining the location of the failure point of the failure line based on the fundamental wave components.

In addition, the fault point determination unit of the fault point position detection device may include: among the line currents measured at both ends of the fault line and the fundamental wave components corresponding to the line current of the healthy line, the fault line The location of the failure point may be determined using fundamental wave components corresponding to the failure phase.

In addition, the failure point determination unit of the failure point location detection device may determine the failure point location m through Equation 4 below.

[Equation 4]

In Equation 4, I _x and I _y are fundamental wave components corresponding to line currents flowing from both ends of the faulty line to the faulty point through the faulty conductor, and I _w is the fault of the healthy line. It is the fundamental wave component corresponding to the line current of the phase.

In addition, the fault point determination unit of the fault point position detection device includes bus voltages and line currents corresponding to both ends of the fault line, and among the fundamental wave components corresponding to the line current of the healthy line, The fault resistance of the fault line may be determined using fundamental wave components corresponding to the fault phase of the fault line.

In addition, the failure point determination unit of the failure point location detection device may determine the failure resistance R _F through Equation 6 below.

[Equation 6]

In Equation 6, I _x and I _y are fundamental wave components corresponding to line currents flowing from both ends of the faulty line to the faulty point through the faulty conductor, and V _x and _Vy are the faulty Corresponding to the bus voltages measured at both ends of the line, the I _w is a fundamental wave component corresponding to the faulty line current of the healthy line.

In addition, the fault point determination unit of the fault point location detection device may determine the mutual impedance Z _m between the parallel lines through Equation 5 below.

[Equation 5]

이고, 상기 Z₀는 상기 병행 선로들의 양단 변전소들에서 측정되는 선로 전류들의 대칭좌표에서의 영상분 임피던스를 나타내며, 상기 Z₁은 상기 대칭좌표에서의 정상분 임피던스를 나타내고, 상기 Z₂는 상기 대칭좌표에서의 역상분 임피던스(계산치 또는 실측치)를 나타낸다. In Equation 5, the magnetic impedance of one of the parallel lines is

, wherein Z ₀ represents a zero impedance in symmetric coordinates of line currents measured at substations at both ends of the parallel lines, Z ₁ represents a positive impedance in the symmetric coordinate, and Z ₂ is the symmetrical Represents the negative-sequence impedance (calculated value or measured value) in coordinates.

In addition, the plurality of fault waveform acquisition units of the fault point position detection device include a plurality of first protection relays located at both ends of the fault line, and a plurality of second protection relays located at both ends of the sound line. may include.

In addition, the plurality of first protection relays of the fault point position detection device may communicate with the plurality of second protection relays to trigger recording of the fault waveform when a fault occurrence is detected from the fault line.

In addition, at least one of the plurality of second protection relays of the fault point position detection device may determine that a fault has occurred in the fault line when the bus voltage at the corresponding substation is lowered to a predetermined value or less.

In addition, the plurality of failure waveform acquisition units of the failure point position detection device are located at the first end of the power transmission line, and corresponding bus voltages and line currents at the first ends of the failure line and the healthy line a plurality of protection relays acquiring fault waveforms corresponding to It may include a fault waveform recorder for acquiring waveforms.

In addition, the plurality of failure waveform acquisition units of the failure point position detection device are located at the first end of the power transmission line, and corresponding bus voltages and line currents at the first ends of the failure line and the healthy line a first fault waveform recording device for acquiring fault waveforms corresponding to and a second failure waveform recording device for acquiring failure waveforms.

In addition, according to another aspect of the present invention, there is provided a substation system including a fault point location detection device in a power transmission line. The fault point location detection device of the substation system includes bus voltage waveforms and line current waveforms measured at both ends of a faulty line among parallel lines included in the transmission line, and line current waveforms, and a fault among the parallel lines. A plurality of fault waveform acquisition units for acquiring the line current measured in the non-occurring sound line as fault waveforms, a synchronization unit for synchronizing the fault waveforms, and a fundamental wave component from the fault waveforms synchronized by the synchronization unit It may include a fundamental wave component obtaining unit to acquire, and a failure point determining unit for determining a location of the failure point of the fault line based on the fundamental wave components.

In addition, the failure point determination unit of the substation system, among the line currents measured at both ends of the fault line, and the fundamental wave components corresponding to the line current of the sound line, is on the failure of the fault line. The location of the failure point may be determined using the corresponding fundamental wave components.

In addition, the failure point determining unit of the substation system may determine the failure point location (m) through Equation 4 below.

[Equation 4]

In Equation 4, I _x and I _y are fundamental wave components corresponding to line currents flowing from both ends of the faulty line to the faulty point through the faulty conductor, and I _w is the fault of the healthy line. It is the fundamental wave component corresponding to the line current of the phase.

In addition, the fault point determination unit of the substation system includes bus voltages and line currents corresponding to both ends of the fault line, and among the fundamental wave components corresponding to the line current of the healthy line, the fault line The fault resistance of the fault line may be determined using fundamental wave components corresponding to the fault phase of .

In addition, the fault point determination unit of the substation system may determine the fault resistance R _F through Equation 6 below.

[Equation 6]

In Equation 6, I _x and I _y are fundamental wave components corresponding to line currents flowing from both ends of the faulty line to the faulty point through the faulty conductor, and V _x and _Vy are the faulty Corresponding to the bus voltages measured at both ends of the line, the I _w is a fundamental wave component corresponding to the faulty line current of the healthy line.

In addition, the fault point determination unit of the fault point location detection device may determine the mutual impedance Z _m between the parallel lines through Equation 5 below.

[Equation 5]

이고, 상기 Z₀는 상기 병행 선로들의 양단 변전소들에서 측정되는 선로 전류들의 대칭 좌표에서의 영상 분 임피던스를 나타내며, 상기 Z₁은 상기 대칭 좌표에서의 정상 분 임피던스를 나타내고, 상기 Z₂는 상기 대칭 좌표에서의 역상 분 임피던스(계산치 또는 실측치)를 나타낸다. In Equation 5, the magnetic impedance of one of the parallel lines is

, wherein Z ₀ represents the zero partial impedance in symmetric coordinates of line currents measured at substations at both ends of the parallel lines, Z ₁ represents the normal partial impedance in the symmetric coordinate, and Z ₂ is the symmetrical Reverse phase partial impedance (calculated or measured) in coordinates.

In addition, the plurality of fault waveform acquisition units of the substation system may include a plurality of first protection relays located at both ends of the fault line, and a plurality of second protection relays located at both ends of the sound line. can

In addition, the plurality of first protection relays of the substation system may communicate with the plurality of second protection relays to trigger recording of the fault waveform when a fault occurrence is detected from the fault line.

In addition, at least one of the plurality of second protection relays of the substation system may determine that a fault has occurred in the fault line when the bus voltage at the corresponding substation is lowered to a predetermined value or less.

In addition, the plurality of fault waveform acquisition units of the substation system are located at the first end of the power transmission line and correspond to the corresponding bus voltage and line current at the first end of the fault line and the healthy line. a plurality of protection relays for acquiring fault waveforms, and located at the second end of the power transmission line, to obtain fault waveforms corresponding to a corresponding bus voltage and a line current at the second end of the fault line and the healthy line It may also include a fault waveform recorder.

In addition, the plurality of fault waveform acquisition units of the substation system are located at the first end of the power transmission line and correspond to the corresponding bus voltage and line current at the first end of the fault line and the healthy line. a first fault waveform recording device for acquiring fault waveforms, and located at the second end of the power transmission line, a fault waveform corresponding to a corresponding bus voltage and a line current at the second end of the fault line and the healthy line It may include a second fault waveform recorder for acquiring

In addition, according to another aspect of the present invention, there is provided a method for detecting a location of a fault point in a power transmission line. The fault point location detection method includes: detecting occurrence of a fault in the power transmission line; bus voltage waveforms and line current waveforms measured at both ends of a faulty line among parallel lines included in the power transmission line , and acquiring a line current measured in a sound line in which a fault does not occur among the parallel lines as fault waveforms, synchronizing the fault waveforms, and obtaining fundamental wave components from the synchronized fault waveforms , and determining a location of a fault point of the fault line based on the fundamental wave components.

The determining may include using fundamental wave components corresponding to the faulty phase of the faulty line among the line currents measured at both ends of the faulty line and the fundamental wave components corresponding to the line current of the healthy line. to determine the location of the failure point.

The determining of the failure point location using the fundamental wave components corresponding to the failure phase of the failure line may include determining the failure point location (m) through Equation (4).

The determining may include: bus voltages and line currents corresponding to both ends of the fault line, and a fundamental corresponding to the fault phase of the fault line among the fundamental wave components corresponding to the line current of the healthy line It may include determining the fault resistance of the fault line using the wave components.

In the step of determining the fault resistance of the fault line using fundamental wave components corresponding to the fault phase of the fault line, the fault resistance R _F may be determined through Equation 6 above.

The determining may include determining the _{mutual impedance (Z m} ) between the parallel lines through Equation (5).

Acquiring the fault waveforms includes: acquiring bus voltage waveforms and line current waveforms measured at both ends of the fault line through a plurality of first protection relays located at both ends of the fault line as the fault waveform and acquiring a line current waveform measured in the sound line as the fault waveform through a plurality of second protection relays located at both ends of the sound line.

Acquiring the fault waveforms may further include, by the plurality of first protection relays, transmitting a notification signal triggering recording of the fault waveforms to the plurality of second protection relays.

The step of acquiring the fault waveforms further includes the step of determining, by at least one of the plurality of second protection relays, that a fault has occurred in the fault line when the bus voltage in the corresponding substation is lowered to a predetermined value or less can do.

According to an embodiment of the present invention, it is possible to improve the performance of detecting a fault point in a power transmission line including a parallel line.

1 schematically illustrates an apparatus for detecting a location of a fault point in a power transmission line according to an embodiment of the present invention.
2 illustrates an example in which the failure waveform acquisition units of the failure point position detection apparatus according to an embodiment of the present invention are implemented through protection relays.
3 is a diagram illustrating another example in which the failure waveform acquisition units of the failure point position detection apparatus according to an embodiment of the present invention are implemented through protective relays.
4 shows an example in which the fault waveform acquisition units of the fault point position detection apparatus according to an embodiment of the present invention are implemented through protection relays and a fault recording device.
5 is a diagram illustrating an example in which the failure waveform acquisition units of the failure point location detection apparatus according to an embodiment of the present invention are implemented through the failure recording apparatus.
6 is an equivalent circuit illustrating mutual inductive coupling occurring between lines when a ground fault occurs in any one of two parallel lines.
7 is an equivalent circuit showing an induced voltage generated by mutual inductive coupling between lines when a ground fault occurs in any one of two parallel lines.
8 illustrates a method for detecting a location of a fault point in a power transmission line according to an embodiment of the present invention.
9 to 12 are views for explaining the effect according to an embodiment of the present invention.
13 is a diagram for explaining a correlation between a failure resistance and a failure point position error rate.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification and claims, when a part "includes" a certain element, it means that other elements may be further included, rather than excluding other elements, unless otherwise stated.

Hereinafter, an apparatus and method for detecting a fault point in a power transmission line according to an embodiment of the present invention will be described in detail with reference to the necessary drawings.

FIG. 1 schematically shows an apparatus for detecting a location of a failure point in a power transmission line according to an embodiment of the present invention, and shows an apparatus for detecting a location of a failure point in a power transmission line including parallel lines.

Referring to FIG. 1 , the failure point position detection apparatus 10 according to an embodiment of the present invention includes failure waveform acquisition units 11 , 12 , 13 , 14 , a failure waveform database 15 , and a synchronization unit 16 . , a fundamental wave component acquisition unit 17 , and a failure point determination unit 18 may be included. The components shown in FIG. 1 are not essential, so the fault point location detection apparatus 10 according to an embodiment of the present invention may include more or fewer components.

The first fault waveform acquisition unit 11 is disposed at a first end among both ends of the power transmission line, and when a fault is detected in the first line among the two lines constituting the power transmission line, the fault waveforms are acquired for the first line, This may be stored in the failure waveform database 15 . In this document, the failure waveform stored in the failure waveform database 15 represents time-series data obtained by discretely sampling and analog-to-digital conversion of a corresponding analog current signal or voltage signal.

The fault waveform acquired by the first fault waveform acquiring unit 11 includes the current waveform recorded at the first end of the first line, and the bus voltage waveforms measured at the substation corresponding to the first end of the first line can do. That is, the first fault waveform acquisition unit 11 may acquire the current waveform of the first line recorded through a current transformer (CT) located at the first end of the first line as the fault waveform. In addition, the first fault waveform acquisition unit 110 may acquire the voltage waveforms of the bus bar measured through a potential transformer (PT) at the substation at the first end of the first line as the fault waveform.

When acquiring the failure waveform, the first failure waveform acquisition unit 11 may acquire a current waveform and a previous voltage waveform as a failure waveform as well as after the failure detection time point. That is, the first failure waveform acquisition unit 11 fails from the time (start time) before a predetermined time based on the time when the failure is detected in the first line from the instrument current transformer (CT) and the instrument transformer (PT). Bus voltage and rotation current waveforms from the detection time to a point (end time) after a predetermined time may be acquired and stored as a fault waveform.

The second fault waveform acquisition unit 12 is disposed at a first end among both ends of the power transmission line, and when a fault is detected in the second line among the two lines constituting the power transmission line, it acquires fault waveforms for the second line and This may be stored in the failure waveform database 15 . Here, the failure waveform acquired by the second failure waveform acquisition unit 12 may include a current waveform recorded at the first end of the second line, and a voltage waveform measured at a substation at the first end of the second line. can That is, the second fault waveform acquisition unit 12 may acquire the current waveform of the second line recorded through the instrument current transformer CT located at the first end of the second line as the fault waveform. In addition, the second fault waveform acquisition unit 12 may acquire the voltage waveform of the bus bar measured through the instrument transformer PT at the substation at the first end of the second line as the fault waveform.

When the failure waveform is acquired, the second failure waveform acquisition unit 12 may acquire not only after the failure detection time but also previous current waveforms and voltage waveforms as failure waveforms. That is, the second failure waveform acquisition unit 12 fails from the time (start time) before a predetermined time based on the time when the failure is detected in the second line from the instrument current transformer (CT) and the instrument transformer (PT). Bus voltage and rotation current waveforms from the detection time to a point (end time) after a predetermined time may be acquired and stored as a fault waveform.

The first and second failure waveform acquisition units 11 and 12 may communicate with each other. For example, when a failure is detected in the corresponding line, the first and second failure waveform acquisition units 11 and 12 not only store the failure waveform as described above, but also notify the occurrence of a failure in its own line and notify the failure waveform. A notification signal for triggering storage may be transmitted to a fault waveform acquisition unit of another line. For example, when a failure in the first line is detected by the first failure waveform obtaining unit 11, the first failure waveform obtaining unit 11 not only acquires and stores the failure waveform in the first line, but also A notification signal for notifying the occurrence of a failure in the first line may be transmitted to the second failure waveform acquisition unit 12 to trigger the second failure waveform acquisition unit 12 to acquire and store the failure waveform in the second line. . The second fault waveform acquisition unit 12 that has received the notification signal from the first fault waveform acquisition unit 11, even if the second line is a healthy line, the current of the second line for a predetermined period based on the time at which the notification signal is received. A waveform may be acquired as a failure waveform, and the acquired failure waveform may be stored in the failure waveform database 15 . In this case, the failure waveform obtained from the second line, which is a sound line, is the first time from the time point (start time) before a predetermined time from the reception time of the notification signal to the time point (end time) after a predetermined time from the time of reception of the notification signal (end time) It may include a current waveform of two lines.

The first fault waveform acquisition unit 11 or the second fault waveform acquisition unit 12 monitors the bus voltage corresponding to the first end of the first and second lines through the instrument transformer PT, and the corresponding bus When the voltage falls below a predetermined value, it is also possible to automatically acquire and store a fault waveform. In this case, the fault waveform is the line current from the point in time (start time) before the predetermined time from the time when the bus voltage falls below the predetermined value to the time (end time) after the predetermined time from the time when the bus voltage falls below the predetermined value It may include waveforms.

Meanwhile, in an embodiment of the present invention, in order to increase the estimation accuracy when estimating the failure point, failure waveforms from both ends of the power transmission line may be used instead of either one. To this end, the failure point position detection apparatus 10 may further include a third failure waveform obtaining unit 13 and a fourth failure waveform obtaining unit 14 .

The third fault waveform acquisition unit 13 and the fourth fault waveform acquisition unit 14 are disposed at the second end of the power transmission line, and the first fault waveform acquisition unit 13 and the second fault waveform acquisition unit 14 described above ), each of the fault waveforms from the first and second lines may be acquired and stored in the fault waveform database 15 .

Meanwhile, the above-described fault waveform acquisition units 11 to 14 may be performed by a protection relay or a fault waveform recording device implemented separately from the protection relay.

Hereinafter, examples in which the failure waveform acquisition units 11 to 14 of the failure point position detection apparatus 10 record failure waveforms will be described with reference to FIGS. 2 to 5 .

2 illustrates an example in which the failure waveform acquisition units of the failure point position detection apparatus 10 according to an embodiment of the present invention are implemented through protection relays.

Referring to FIG. 2 , as a failure occurs in the first line L1 , the protection relays 21 and 23 at both ends of the first line L1 detect the failure. The protection relays 21 and 23 are, as the occurrence of a failure in the first line L1 is detected, the instrument transformers PT1 and PT2 located in substations at both ends of the first line L1 and, Bus voltage waveforms and line current waveforms measured for a predetermined period through the instrument current transformers CT11 and CT12 disposed at both ends of the first line L1 are acquired as a failure waveform of the first line L1.

In addition, the protection relays 21 and 23 of the first line L1 notify the occurrence of a failure to the protection relays 22 and 24 of the second line L2 through communication to instruct fault waveform recording. Signals S21 and S22 are transmitted, respectively. That is, the protection relay 21 located at the first end of the first line L1 transmits the notification signal S21 to the protection relay 22 located at the first end of the second line L2, The protection relay 23 located at the second end of the first line (L1) transmits the notification signal (S22) to the protection relay 24 located at the second end of the second line (L2). The protection relays 23 and 24 of the second line L2 that have received this are measured for a predetermined period through the instrument current transformers CT21 and CT22 disposed at both ends of the second line L2. The line current waveforms of the line L2 are acquired as the fault waveforms of the second line L2.

In the example of FIG. 2 described above, the protection relays 21 and 22 positioned at the first ends of the first line L1 and the second line L2 are the first and second fault waveform acquisition units 11, respectively. , 12) perform the function of recording the fault waveform, and the protection relays 23 and 24 located at the second ends of the first line L1 and the second line L2 are the third and fourth faults, respectively, as described above. The fault waveform recording function of the waveform acquisition units 13 and 14 is performed.

3 illustrates another example in which the failure waveform acquisition units of the failure point position detection apparatus 10 according to an embodiment of the present invention are implemented through protection relays.

Referring to FIG. 3 , as a failure occurs in the first line L1 , the protection relays 21 and 23 at both ends of the first line L1 detect the failure. The protection relays 21 and 23 are, as the occurrence of a failure in the first line L1 is detected, the instrument transformers PT1 and PT2 located in substations at both ends of the first line L1 and, The voltage waveforms of the busbars and the line current waveforms of the first line L1 measured for a predetermined period through the instrument current transformers CT11 and CT12 disposed at both ends of the first line L1 are displayed on the first line L1. is obtained as a failure waveform of

In addition, the protection relay 23 located at the second end of the first line (L1), the protection relay 24 located at the second end of the second line (L2) through communication instructing the fault waveform recording A notification signal S22 is transmitted. The protection relay 24 of the second line L2 that has received this is the second line L2 measured for a predetermined period through the instrument current transformer CT22 disposed at the second end of the second line L2. A line current waveform is acquired as a fault waveform of the second line L2.

On the other hand, the protection relay 22 located in the second line (L2) is the first line (L1) through continuous bus voltage monitoring even if a notification signal is not received from the protection relay of the first line (L1) where the failure occurs. It is also possible to detect the occurrence of a failure and record the failure waveform accordingly. That is, even if the protection relay 22 located at the first end of the second line L2 does not receive a notification signal from the protection relay 21 located at the first end of the first line L1, the transmission line When the bus voltage of the first end is monitored and the bus voltage is lowered to a predetermined value or less, a fault occurrence in the first line L1 may be detected. And when a fault occurrence condition in the first line L1 is detected through this, the measurement is performed through the instrument current transformer CT located at the first end of the second line L2 for a predetermined period based on the failure occurrence detection time. The obtained current waveform is acquired as a fault waveform of the second line L2.

In the example of FIG. 3 described above, the protection relays 21 and 22 located at the first ends of the first line L1 and the second line L2 are the first and second fault waveform acquisition units 11, respectively. , 12) perform the function of recording the fault waveform, and the protection relays 23 and 24 located at the second ends of the first line L1 and the second line L2 are the third and fourth faults, respectively, as described above. The fault waveform recording function of the waveform acquisition units 13 and 14 is performed.

4 shows an example in which the failure waveform acquisition units of the failure point position detection apparatus 10 according to an embodiment of the present invention are implemented through protection relays and a failure recording device.

Referring to FIG. 4 , as a failure occurs in the first line L1 , the protection relays corresponding to the first line L1 detect the occurrence of a failure in the first line L1 . The protection relay 33 that has detected the occurrence of a failure in the first line L1 performs a function of acquiring and storing a failure waveform at the second end of the first line L1, and through communication with the second line L2 ) transmits a notification signal (S31) instructing the recording of the fault waveform to the protection relay 34 located at the second end. The protection relay 34 of the second line L2, which has received this, converts the current waveform of the second line L2 measured for a predetermined period through the instrument current transformer CT22 of the second line L2 into a fault waveform. acquire

Meanwhile, in FIG. 4 , a fault waveform is obtained through the protection relays 33 and 34 only for the second ends of the first line L1 and the second line L2, and the first line L1 and the second line For the second end of (L2), a fault waveform is acquired through a separate fault recording device 31 . A protection relay (not shown) that detects the occurrence of a failure of the first line L1 at the first end of the first line L1 is a failure that notifies the failure of the first line L1 to the failure recording device 31 . A detection signal S32 is transmitted. The fault recorder 31 receiving this receives the bus voltage waveform and the line current waveform measured for a predetermined period through the instrument transformer PT1 and the instrument current transformer CT11 for the first end of the first line L1. Acquire as a fault waveform. In addition, a current waveform measured for a predetermined period through the instrument current transformer CT21 for the first end of the second line L1 is acquired as a fault waveform.

In the above-described embodiment of FIG. 4 , the failure recording device 31 performs the failure waveform recording function of the first and second failure waveform acquisition units 11 and 12 described above, and the protection relays 33 and 34 are respectively The failure waveform recording function of the above-described third and fourth failure waveform acquisition units 13 and 14 is performed.

5 illustrates an example in which the failure waveform acquisition units of the failure point location detection apparatus 10 according to an embodiment of the present invention are implemented through the failure recording apparatus.

5, as a failure occurs in the first line (L1), the protection relays (not shown) corresponding to the first line (L1) detect the occurrence of a failure in the first line (L1), The failure detection signals S41 and S42 are transmitted to the failure recording devices 41 and 43 located at both ends of the power transmission line.

The failure recorders 41 and 43 that have received this measure both ends of the first line L1 through the instrument transformers PT1 and PT2 and the instrument current transformers CT11 and CT12 for a predetermined period of time. The acquired bus voltage waveform and line current waveform are acquired as fault waveforms, respectively. Also, for both ends of the second line L1, current waveforms measured for a predetermined period through the instrument current transformers CT21 and C22 are respectively acquired as fault waveforms.

In the above-described embodiment of FIG. 5 , the failure recording device 41 performs the failure waveform recording function of the first and second failure waveform acquisition units 11 and 12 described above, and the failure recording device 43 performs the above-described first and second failure waveform recording functions. The fault waveform recording function of the third and fourth fault waveform acquisition units 13 and 14 is performed.

Again, referring to FIG. 1 , the synchronization unit 16 may read the failure waveforms from the failure waveform database 15 and output the read failure waveforms in synchronization with the time axis.

The fundamental wave component obtaining unit 17 receives a fundamental component (or fundamental wave RMS) from the fault waveforms synchronized and output by the synchronizer 16 through Digital Fourier Transformation (DFT), wavelet transform, or the like. can be obtained

When the fundamental wave components are obtained as described above, the failure point determination unit 18 may estimate the location of the failure point based on them.

Hereinafter, a method of estimating a failure point from fundamental wave components of failure waveforms in the failure point determination unit 18 will be described in detail with reference to FIGS. 6 and 7 .

6 is an equivalent circuit illustrating mutual inductive coupling occurring between the lines when a ground fault occurs in any one of the two parallel lines, and FIG. 7 is any one of the two parallel lines. It is an equivalent circuit representing the induced voltage generated by mutual inductive coupling between lines when a ground fault occurs in the

In general, since the fault current is very large compared to the normal load current, hereinafter, among the plurality of phase conductors constituting each line, the remaining sound except for the phase in which the line fault occurs (hereinafter referred to as 'failure phase'). The phase conductors and the load current flowing through them are neglected.

In the description below, X and Y represent fault phase nodes of the substation bus at both ends of the transmission line, respectively, and m and R _F represent the fault point location and fault resistance, respectively. In addition, V _X and V _Y are the fault-phase voltages at the X and Y nodes of the substation bus, I _x and I _y are the currents supplied to the fault point through fault-phase conductors in the substation at both ends of the transmission line, and I _w is the fault The fault phase line current of the healthy line that has not occurred, that is, the line current flowing through the conductor of the same phase as the fault phase of the fault line in the healthy line, respectively, indicates the corresponding voltage waveform or fundamental wave component of the current waveform. However, the magnetic impedance of two parallel lines is the _{same as Z s} , and Z _m represents the mutual impedance between the lines.

Referring to FIG. 7, when a fault occurs, the current flowing through the faulty-phase conductor of the faulty line (I _x , I _y ), induced voltages of _{V e1} and V _e2 are induced in the faulty phase conductors of the healthy line parallel to the faulty line, respectively. In addition, the voltages of _{V e3} and V _e4 are induced on both sides of the fault point of the faulty line by the fault-phase current I _{w of the healthy line, respectively.} These induced voltages (V _e1 , V _e2 , V _e3 , V _{e4 ) are the mutual impedance (Z m} ) between the lines parallel to each other as shown in Equation 1 below, the fault location (m), and the line current (I _{x )} , I _y , I _w ) can be expressed as a function of

[Equation 1]

Based on Equation 1, if the Kirchhoff voltage law is applied to the equivalent circuit of FIG. 7 showing a case in which a ground fault occurs in any one of two parallel lines, V _x and V _y are expressed as Equation 2 below. can indicate

[Equation 2]

If the above Equation 2 is _{summarized with respect to the line currents (I x} , I _y , I _w ) in the fault phase of each line, it can be expressed as the following Equation 3 .

[Equation 3]

Referring to Equation 3 above, each line current (I _x , I _y , I _w ) is the bus voltage (V _x , V _y ), the magnetic and mutual impedance of the line (Z _s , Z _m ), and the point of failure It is expressed as a function of position (m) and fault resistance (R _{F ).} Therefore, when the bus voltage and line current are measured at the substation at both ends of the transmission line, the failure point (Equation 4), the mutual impedance between the lines (Equation 5) and the failure resistance ( Equation 6) can be inversely calculated.

[Equation 4]

[Equation 5]

,

,

step,

[Equation 6]

In Equation 5 above, Z _s is the magnetic impedance of one of the parallel lines, and Z ₀ , Z ₁ , and Z ₂ are the symmetrical coordinates of the line currents measured at substations at both ends of the parallel line (image, normal, reverse phase). min), Z ₀ represents the zero impedance (calculated or measured value) _{of the line, Z 1} represents the line's positive impedance (calculated or measured), and Z ₂ is the line's negative-sequence impedance ( calculated or measured values).

Referring to Equation 4 above, in the embodiment, it is possible to determine the location of the fault point only with fundamental wave components of line currents measured from parallel lines.

On the other hand, in the _{conventional fault point determination method that does not consider the mutual impedance (Z m ) between parallel lines, the induced voltages (V e1} , V _e2 , V _{e3 )} of the lines by inductive coupling as in Equation 2 above. , V _e4 ) are all ignored, and the fault point location (m) is determined as shown in Equation 7 below, so that the accuracy is relatively low.

[Equation 7]

In the failure point position detection apparatus 10 having the above structure, the failure waveform acquisition units 11 , 12 , 13 , 14 , the failure waveform database 15 , the synchronization unit 16 , the fundamental wave component acquisition unit 17 , and The failure point determination unit 18 may be performed by one or more central processing units (CPUs) or a processor implemented by other chipsets, microprocessors, or the like.

In addition, the components of the above-described fault point location detection device 10 may be implemented to be included in a substation system that operates substations at both ends of a power transmission line.

8 illustrates a method for detecting a location of a fault point in a power transmission line according to an embodiment of the present invention. The method of FIG. 8 may be performed by the failure point position detection apparatus 10 described above with reference to FIGS. 1 to 7 .

Referring to FIG. 8 , the fault point location detection device 10 detects the occurrence of a failure in the power transmission line composed of parallel lines, through protective relays located at substations at both ends of the power transmission line, parallel lines constituting the power transmission line. Continuously monitor (S100). And, when the occurrence of a failure is detected from any one of the parallel lines (S110), a failure waveform is acquired from the lines through the failure waveform acquisition units 11 to 14 (S120).

In the step S120, the fault waveform acquisition units 11 to 14 are the bus voltage waveforms measured at substations at both ends of the fault line among the parallel lines, the line current waveforms measured at both ends of the fault line, and the fault line Line current waveforms measured at both ends of the remaining line in parallel with , may be acquired as a fault waveform. Considering that multi-phase AC is transmitted through each line, the failure waveforms obtained through the step S120 may be those obtained for each of a plurality of phases.

Next, the failure point position detection apparatus 10 synchronizes the failure waveforms obtained through the step S120 on the time axis (S130), and extracts fundamental wave components, that is, fundamental wave RMS values from the synchronized failure waveforms (S140). ).

When the fundamental wave components are obtained through the step S140, the fault point position detecting device 10 includes the fundamental wave components corresponding to the fault phase line current measured at both ends of the fault line among the acquired fundamental wave components and the bus line. A fault point location, a fault resistance, and a mutual impedance between the lines are determined using the fundamental wave components corresponding to the voltage and the fundamental wave components corresponding to the fault phase line current of the healthy line (S150).

In the step S150, the fault point position detection device 10 calculates the fundamental wave components of the faulty line current measured at both ends of the faulty line and the fundamental wave components of the faulty line current of the healthy line in Equation 4 above. It can be applied to determine the location of the fault point.

In step S150, the fault point position detection device 10 detects the fundamental wave components of the faulty line current measured at both ends of the faulty line and the fundamental wave components of the faulty phase bus voltage, and the faulty line current of the healthy line. The fault resistance can be determined by applying the fundamental wave components of Equation 6 above.

In the step S150, the fault point position detection device 10 calculates the fundamental wave components of the fault-phase line current of the healthy line, the fundamental wave components of the fault-phase bus voltage at both ends of the line, and the magnetic impedance of each line using the above equation 5 can be applied to determine the mutual impedance between lines.

As described above, in the embodiment of the present invention _{, not only the fault-phase currents I X} , I _{Y of the faulty line but also the line current I W} of the healthy line in parallel with the faulty line are used to determine the fault point, By determining the location of the fault point in consideration of the influence of the inductive coupling (Z _M ) and fault resistance (R _F ) between parallel lines, the fault point detection accuracy can be increased.

Hereinafter, the effect of the fault point position detection apparatus 10 and the method according to an embodiment of the present invention will be described with reference to FIGS. 9 to 12 .

9 to 12 are diagrams for explaining the effects of an apparatus and method for detecting a point of failure location according to an embodiment of the present invention. The results of simulating the A-phase ground fault of one line in the Seodaegu-Namgumi and Gwaneum-Guam lines, which are 154kV parallel lines in the KEPCO system using E (Power System Simulator for Engineering), are shown. In the simulation process, _{it was assumed that the fault resistance (R F} ) fluctuates within the range of 1~15Ω and the location of the fault point within the range of 0.1~0.9pu.

9 shows the results of calculating the bus voltage and line current characteristics at both ends in the case of simulating the A-phase ground fault of line #1 while varying the fault point location and fault resistance in the 154kV Seodaegu-Namgumi 2-line line. In addition, FIG. 10 shows a case in which the failure point position detection method according to the prior art (see Equation 7 above) and the failure point location detection method according to the embodiment (see Equation 4 above) are applied to the simulation result of FIG. 9 , respectively. This is a comparison of the error rate at the point of failure.

9 and 10 , it can be seen that, when the method for detecting the location of a failure point according to the embodiment is applied, the error rate is less than 0.3% regardless of the failure resistance, which is very low compared to the prior art.

11 shows both ends of the case of simulating the A-phase ground fault of line #1 while varying the fault point location and fault resistance in the 154kV Gwaneum-Guam section 2-track line, which has different fault characteristics from the Seodaegu-Namgumi line of FIG. The results of calculating the bus voltage and line current characteristics are shown. In addition, FIG. 12 is a case in which the failure point position detection method according to the prior art (see Equation 7 above) and the failure point position detection method according to the embodiment (see Equation 4 above) are applied to the simulation result of FIG. 11 , respectively. This is a comparison of the error rate at the point of failure.

11 and 12 , it can be seen that, when the method for detecting the location of a failure point according to the embodiment is applied, the error rate is less than 0.2% regardless of the failure resistance, which is very low compared to the prior art.

13 illustrates a correlation between the failure resistance and the failure point position error rate with reference to Equation 6 above.

Referring to FIG. 13 , it can be seen that the error rate of estimating the fault point location is relatively large as the fault resistance value is small, and when the fault resistance value is large, the error rate of the fault point location estimation is reduced to less than 10% in the case of a high resistance ground fault. . Accordingly, in an embodiment of the present invention, the failure resistance value estimated with reference to Equation 6 above may be used to analyze the cause of the failure. For example, the fault resistance value estimated through the embodiment of the present invention, such as whether the fault resistance is relatively large, whether it is a ground fault caused by contact with a tree, or a ground fault caused by a contact of a crane having a relatively small fault resistance value, is It can be used as useful information to estimate the cause.

The embodiment of the present invention is not implemented only through the apparatus and/or method described above, and a computer program stored in a computer readable recording medium, or the program is recorded in order to realize a function corresponding to the configuration of the embodiment of the present invention. It can also be implemented through a computer-readable recording medium, and such an implementation can be easily implemented by an expert in the technical field to which the present invention pertains from the description of the above-described embodiment.

The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of the computer-readable recording device include ROM, RAM, CD-ROM, DVD_ROM, DVD_RAM, magnetic tape, floppy disk, hard disk, and optical data storage device. In addition, the computer-readable recording medium may be distributed in network-connected computer devices to store and execute computer-readable codes in a distributed manner.

Although the embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the right.

10: fault point position detection device
11, 12, 13, 14: Fault waveform acquisition unit
15: Fault Waveform Database
16: synchronization unit
17: Fundamental wave component acquisition unit
18: failure point determination unit

Claims (31)

In the device for detecting a fault point in a power transmission line,
Bus voltage waveforms and line current waveforms measured at both ends of the faulty line in which the fault has occurred among the parallel lines included in the transmission line, and the line current measured in the healthy line in which the fault does not occur among the parallel lines A plurality of failure waveform acquisition units to acquire the failure waveforms,
a synchronizer for synchronizing the failure waveforms;
a fundamental wave component obtaining unit for obtaining fundamental wave components from the fault waveforms synchronized by the synchronizing unit; and
A fault point determination unit for determining a fault point location of the fault line based on the fundamental wave components
A fault point location detection device comprising a. According to claim 1,
The failure point determination unit,
The fault point location is determined by using the fundamental wave components corresponding to the fault phase of the fault line among the line currents measured at both ends of the fault line and the fundamental wave components corresponding to the line current of the healthy line. Determining, fault point location detection device. 3. The method of claim 2,
The failure point determination unit determines the failure point location (m) through the following Equation (4).
[Equation 4]

(In Equation 4, I _x and I _y are fundamental wave components corresponding to line currents flowing from both ends of the faulty line to the faulty point through the faulty conductor, and _Iw is the It is a fundamental wave component corresponding to the faulty line current.) According to claim 1,
The failure point determination unit,
Bus voltages and line currents corresponding to both ends of the fault line, and fundamental wave components corresponding to the fault phase of the fault line among the fundamental wave components corresponding to the line current of the healthy line, A fault point position detection device that determines the fault resistance of the fault line. 5. The method of claim 4,
The fault point determination unit determines the fault resistance (R _F ) through Equation 6 below, the fault point location detection device.
[Equation 6]

(In Equation 6, I _x and I _y are fundamental wave components corresponding to line currents flowing from both ends of the fault line through the faulty conductor to the fault point, and V _x and V _y are the Corresponding to the bus voltages measured at both ends of the faulty line, the I _w is a fundamental wave component corresponding to the faulty line current of the healthy line) According to claim 1,
The fault point determination unit determines the mutual impedance (Z _m ) between the parallel lines through Equation 5 below, the fault point location detection device.
[Equation 5]

(In Equation 5, the magnetic impedance of one of the parallel lines is

, wherein Z ₀ represents zero impedance in symmetric coordinates of line currents measured at substations at both ends of the parallel lines, Z ₁ represents positive impedance in the symmetric coordinate, and Z ₂ represents the symmetrical Represents the negative-sequence impedance (calculated or measured) in coordinates) According to claim 1,
The plurality of failure waveform acquisition units,
A plurality of first protection relays located at both ends of the fault line, and
A plurality of second protection relays located at both ends of the sound line
Including, a fault point location detection device. 8. The method of claim 7,
The plurality of first protection relays communicate with the plurality of second protection relays to trigger recording of the fault waveform when a fault occurrence is detected from the fault line. 8. The method of claim 7,
At least one of the plurality of second protection relays determines that a failure has occurred in the failure line when the bus voltage in the corresponding substation is lowered to a predetermined value or less. According to claim 1,
The plurality of failure waveform acquisition units,
a plurality of protection relays located at the first end of the power transmission line to obtain fault waveforms corresponding to a corresponding bus voltage and line currents at the first end of the fault line and the healthy line, and
a fault waveform recording device located at the second end of the power transmission line to obtain fault waveforms corresponding to the corresponding bus voltage and line current at the second end of the fault line and the healthy line;
Including, a fault point location detection device. According to claim 1,
The plurality of failure waveform acquisition units,
a first fault waveform recording device located at the first end of the power transmission line to acquire fault waveforms corresponding to a corresponding bus voltage and a line current at the first end of the fault line and the healthy line, and
A second fault waveform recording device located at the second end of the power transmission line to acquire fault waveforms corresponding to a corresponding bus voltage and line current at the second end of the fault line and the healthy line
Including, a fault point location detection device. A substation system comprising a fault point location detection device in a power transmission line,
The fault point location detection device in the power transmission line,
Bus voltage waveforms and line current waveforms measured at both ends of the faulty line in which the fault has occurred among the parallel lines included in the transmission line, and the line current measured in the healthy line in which the fault does not occur among the parallel lines A plurality of failure waveform acquisition units to acquire the failure waveforms,
a synchronizer for synchronizing the failure waveforms;
a fundamental wave component obtaining unit for obtaining fundamental wave components from the fault waveforms synchronized by the synchronizing unit; and
A fault point determination unit for determining a fault point location of the fault line based on the fundamental wave components
Including, a substation system. 13. The method of claim 12,
The failure point determination unit,
The fault point location is determined by using the fundamental wave components corresponding to the fault phase of the fault line among the line currents measured at both ends of the fault line and the fundamental wave components corresponding to the line current of the healthy line. Determining, substation system. 14. The method of claim 13,
The failure point determination unit, the substation system to determine the failure point location (m) through the following Equation (4).
[Equation 4]

(In Equation 4, I _x and I _y are fundamental wave components corresponding to line currents flowing from both ends of the faulty line to the faulty point through the faulty conductor, and _Iw is the It is a fundamental wave component corresponding to the faulty line current.) 13. The method of claim 12,
The failure point determination unit,
Bus voltages and line currents corresponding to both ends of the fault line, and fundamental wave components corresponding to the fault phase of the fault line among the fundamental wave components corresponding to the line current of the healthy line, A substation system that determines the fault resistance of a fault line. 16. The method of claim 15,
The failure point determination unit, the substation system to determine _{the failure resistance (R F ) through the following Equation (6).}
[Equation 6]

(In Equation 6, I _x and I _y are fundamental wave components corresponding to line currents flowing from both ends of the fault line through the faulty conductor to the fault point, and V _x and V _y are the Corresponding to the bus voltages measured at both ends of the faulty line, the I _w is a fundamental wave component corresponding to the faulty line current of the healthy line) 13. The method of claim 12,
The fault point determination unit determines the mutual impedance (Z _m ) between the parallel lines through Equation 5 below, a substation system.
[Equation 5]

(In Equation 5, the magnetic impedance of one of the parallel lines is

, wherein Z ₀ represents zero impedance in symmetric coordinates of line currents measured at substations at both ends of the parallel lines, Z ₁ represents positive impedance in the symmetric coordinate, and Z ₂ represents the symmetrical Represents the negative-sequence impedance (calculated or measured) in coordinates) 13. The method of claim 12,
The plurality of failure waveform acquisition units,
A plurality of first protection relays located at both ends of the fault line, and
A plurality of second protection relays located at both ends of the sound line
Including, a substation system. 19. The method of claim 18,
The plurality of first protection relays, when a failure occurrence is detected from the failure line, communicates with the plurality of second protection relays to trigger recording of the failure waveform. 20. The method of claim 19,
At least one of the plurality of second protection relays determines that a failure has occurred in the faulty line when the bus voltage in the corresponding substation is lower than a predetermined value or less. 13. The method of claim 12,
The plurality of failure waveform acquisition units,
a plurality of protection relays located at the first end of the power transmission line to obtain fault waveforms corresponding to a corresponding bus voltage and line currents at the first end of the fault line and the healthy line, and
a fault waveform recording device located at the second end of the power transmission line to obtain fault waveforms corresponding to the corresponding bus voltage and line current at the second end of the fault line and the healthy line;
including, a substation system. 13. The method of claim 12,
The plurality of failure waveform acquisition units,
a first fault waveform recording device located at the first end of the power transmission line to acquire fault waveforms corresponding to a corresponding bus voltage and a line current at the first end of the fault line and the healthy line, and
A second fault waveform recording device located at the second end of the power transmission line to acquire fault waveforms corresponding to a corresponding bus voltage and line current at the second end of the fault line and the healthy line
including, a substation system. A method for detecting a fault point in a power transmission line, the method comprising:
detecting the occurrence of a failure in the power transmission line;
Bus voltage waveforms and line current waveforms measured at both ends of the faulty line in which the fault has occurred among the parallel lines included in the transmission line, and the line current measured in the healthy line in which the fault does not occur among the parallel lines acquiring fault waveforms,
synchronizing the fault waveforms;
obtaining fundamental components from the synchronized fault waveforms; and
Determining a fault point location of the fault line based on the fundamental wave components
A fault point location detection method comprising a. 24. The method of claim 23,
The determining step is
The fault point location is determined by using the fundamental wave components corresponding to the fault phase of the fault line among the line currents measured at both ends of the fault line and the fundamental wave components corresponding to the line current of the healthy line. step to decide
Including, a fault point location detection method. 25. The method of claim 24,
The step of determining the location of the failure point by using the fundamental wave components corresponding to the failure phase of the failure line includes: determining the location of the failure point (m) through Equation 4 below
A fault point location detection method comprising a.
[Equation 4]

(In Equation 4, I _x and I _y are fundamental wave components corresponding to line currents flowing from both ends of the faulty line to the faulty point through the faulty conductor, and _Iw is the It is a fundamental wave component corresponding to the faulty line current) 24. The method of claim 23,
The determining step is
Bus voltages and line currents corresponding to both ends of the fault line, and fundamental wave components corresponding to the fault phase of the fault line among the fundamental wave components corresponding to the line current of the healthy line, Determining the fault resistance of the fault line
Including, a fault point location detection method. 27. The method of claim 26,
The step of determining the fault resistance of the fault line by using the fundamental wave components corresponding to the fault phase of the fault line is a step of determining the fault resistance (R _F ) through Equation 6 below, the fault point location detection method.
[Equation 6]

(In Equation 6, I _x and I _y are fundamental wave components corresponding to line currents flowing from both ends of the fault line through the faulty conductor to the fault point, and V _x and V _y are the Corresponding to the bus voltages measured at both ends of the faulty line, the I _w is a fundamental wave component corresponding to the faulty line current of the healthy line) 24. The method of claim 23,
The determining may include determining the mutual impedance (Z _m ) between the parallel lines through Equation 5 below.
Including, a fault point location detection method.
[Equation 5]

(In Equation 5, the magnetic impedance of one of the parallel lines is

, wherein Z ₀ represents zero impedance in symmetric coordinates of line currents measured at substations at both ends of the parallel lines, Z ₁ represents positive impedance in the symmetric coordinate, and Z ₂ represents the symmetrical Represents the negative-sequence impedance (calculated or measured) in coordinates) 24. The method of claim 23,
Acquiring the fault waveforms comprises:
Acquiring bus voltage waveforms and line current waveforms measured at both ends of the fault line through a plurality of first protection relays located at both ends of the fault line as the fault waveform, and
Acquiring the line current waveform measured in the sound line through a plurality of second protection relays located at both ends of the sound line as the fault waveform
Including, a fault point location detection method. 30. The method of claim 29,
Acquiring the fault waveforms comprises:
transmitting, by the plurality of first protection relays, a notification signal triggering the recording of the fault waveform to the plurality of second protection relays;
Further comprising, a fault point location detection method. 31. The method of claim 30,
Acquiring the fault waveforms comprises:
determining, by at least one of the plurality of second protection relays, that a failure has occurred in the fault line when the bus voltage at the corresponding substation is lower than a predetermined value
Further comprising, a fault point location detection method.

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