Parameter-independent traveling-wave-based fault location using asynchronous measurements

Abstract

An example of fault location in a transmission line connecting a first terminal and a second terminal is described. In the example, arrival times of a first peak, a second peak, and a third peak of a traveling wave detected in measurements taken at the first terminal and the second terminal are detected. A rise time associated with the first peak of the traveling wave is calculated. Based on a comparison of the rise times, one of a first half and a second half of the transmission line is identified as having a fault. One of a first section, a second section, a third section, and a fourth section of the transmission line is identified as having a fault. The length of the transmission line is evaluated. The fault location is evaluated based on the identification that one of the first section, the second section, the third section, and the fourth section has a fault.

Description

Technical Field

[0001] The present invention relates generally to fault location in power transmission lines. In particular, the present invention relates to travelling wave based fault location that is independent of line parameters and uses non-synchronous measurements. Background Art

[0002] The power transmission system is a large and complex network of transmission and distribution lines and numerous electrical components such as generators, transformers, relays, intelligent electronic devices (IEDs), etc. Transmission lines are often subject to faults caused by storms, lightning, snow, freezing rain, insulation breakdown, and short circuit faults caused by birds, branches and other external objects. In general, a fault is defined as an abnormal condition in the electrical system that causes the normal flow of current to be interrupted. This deviated current flow can cause changes in voltage and / or current flow, thereby interrupting power transmission.

[0003] Restoring power after a fault can only be done after the maintenance team has completed repairing the damage caused by the fault. Therefore, accurate fault location in the transmission line is very important so that maintenance personnel can reach the fault location and perform repairs to restore power transmission. Rapid identification of the fault location improves power supply reliability, restoration capabilities, and reduces revenue losses for utilities. Summary of the invention

[0004] The present disclosure relates to a method for locating a fault in a power transmission line connecting a first terminal and a second terminal, the method comprising: obtaining arrival times of a first peak, a second peak, and a third peak of a traveling wave detected in measurements taken at each of the first terminal and the second terminal; calculating a rise time associated with the first peak of the traveling wave detected in measurements taken at the first terminal and the second terminal; identifying one of a front half and a rear half of the power transmission line as having a fault based on a comparison of rise times evaluated for the first peak of the traveling wave at the first terminal and the second terminal; locating the power transmission line as having a fault based on the identification of the presence of a fault in one of the front half and the rear half of the power transmission line and the comparison of arrival times of the first peak, the second peak, and the third peak of the traveling wave at the first terminal and the second terminal. One of the first, second, third and fourth sections of the line is identified as having a fault; the length of the transmission line is evaluated based on the identification that one of the first, second, third and fourth sections has a fault, and a comparison of the arrival times of the first peak, the second peak and the third peak of the traveling wave, the arrival time of the first peak of the traveling wave reflected from the second terminal detected in the measurement performed at the first terminal, and the arrival time of the first peak of the traveling wave reflected from the first terminal detected in the measurement performed at the second terminal; and the fault location is evaluated based on the identification that one of the first, second, third and fourth sections has a fault, the arrival times of the first peak, the second peak and the third peak of the traveling wave detected in the measurements performed at the first terminal and the second terminal, and the evaluated length of the transmission line.

[0005] The present disclosure also relates to a device for locating a fault in a transmission line connecting a first terminal and a second terminal, the device comprising a traveling wave detector, a fault locating module and a fault locating module, wherein the traveling wave detector is used to: detect a first peak, a second peak and a third peak of a traveling wave detected in measurements taken from the first terminal and the second terminal; obtain the arrival time of the first peak, the second peak and the third peak of the traveling wave detected in measurements taken from the first terminal and the second terminal; and calculate a rise time associated with the first peak of the traveling wave detected in measurements taken from the first terminal and the second terminal; the fault locating module is configured to: identify one of the front half and the rear half of the transmission line as having a fault based on a comparison of the calculated rise time associated with the first peak of the traveling wave; and identify one of the front half and the rear half of the transmission line as having a fault based on the identification of the presence of a fault in one of the front half and the rear half, and the first peak, the second peak and the third peak of the traveling wave. A fault location module is coupled to the processor and is used to: evaluate the length of the transmission line based on the identification of the presence of a fault in one of the first, second, third and fourth sections, and a comparison of the arrival times of the first peak, the second peak and the third peak of the traveling wave, the arrival time of the first peak of the traveling wave reflected from the second terminal detected in the measurement from the first terminal, and the arrival time of the first peak of the traveling wave reflected from the first terminal detected in the measurement from the second terminal; and evaluate the fault location based on the identification of the presence of a fault in one of the first, second, third and fourth sections, the arrival times of the first peak, the second peak and the third peak of the traveling wave detected in the measurement from the first terminal and the second terminal, and the estimated length of the transmission line. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The following detailed description refers to the accompanying drawings, in which:

[0007] Figure 1 A block diagram of a dual-source equivalent power grid for fault location according to an example is shown;

[0008] Figure 2a , 2b , 2c and 2d show Bewley lattice diagrams of faults in the first section, the second section, the third section and the fourth section of the transmission line according to an example;

[0009] Figure 3a and 3b A method for fault location in a power transmission line according to an example is shown;

[0010] Figure 4a and 4bshows a tabular comparison of the conventional two-terminal method for fault location and the present invention for various synchronization errors according to examples; and

[0011] Figure 5a and 5b A tabular comparison of the conventional two-terminal method for fault location and the method of the present invention for various wave speed (parameter) errors according to examples is shown. DETAILED DESCRIPTION

[0012] Based on the signals used, fault location techniques can be classified into two different categories: techniques that rely on the basic phasors of voltage and current and techniques that rely on traveling waves generated by the fault. Techniques that rely on the basic phasors of voltage and current are generally referred to as impedance-based fault location methods. In impedance-based fault location methods, the fault locator uses the basic phasor components of current and voltage signals to calculate the impedance of the faulted line. The calculated impedance is an approximate measure of the fault location. Impedance-based methods are widely adopted by power companies due to their ease of use, low sampling data, and low hardware cost.

[0013] However, the accuracy of impedance-based fault location techniques is adversely affected by the fault type, arc resistance, angles of line and source impedances, phasor evaluation techniques, measurement transformer inaccuracies, current transformer (CT) saturation, power flow direction, and source-to-line impedance ratio (SIR). In addition, impedance-based fault location techniques require accurate evaluation of the fundamental phasors of voltage and current, which requires a data set of 3 to 5 cycles after the fault and a reliable phasor evaluation technique.

[0014] In addition, impedance-based fault location methods rely on mutual coupling, non-uniformity of line and source impedances, source-to-line impedance ratio, fault resistance, and fault loop information. With recent advances in data acquisition and signal processing technology, traveling wave fault locators are becoming more popular where higher accuracy is required. Traveling wave-based methods require only 2 to 3 milliseconds (ms) of data to locate the fault point and are not dependent on the above factors. Fault location using traveling waves can be evaluated by multiplying the difference between the arrival times of the incident and reflected waves by the line wave velocity.

[0015] Nowadays, the addition of renewable energy to the main grid is expected to reduce the overall inertia, especially when solar photovoltaic generation is highly integrated with the grid. This reduces the inertia constant and transient stability margin of the system, thereby reducing the critical clearing time of the relay to maintain stable operation of the grid. Therefore, faster transmission line protection methods such as time domain or traveling wave (TW) based methods are used for fault location.

[0016] However, the fault location accuracy of the double-ended (two terminal) TW-based method depends on data synchronization, intelligent electronic device (IED) hardware, software processing delays, and substation cable delays. The accuracy of the TW-based fault location method also depends on the accuracy of the wave speed (line parameters). The wave speed and line length are imprecise and are affected by many practical conditions such as weather, conductor age, temperature, and sag. Therefore, the fault location accuracy of the traditional TW-based technology may be imprecise.

[0017] The accuracy of the two-terminal TW based approach is reported as the distance between the two towers (approximately 280 to 330 meters). For data synchronization in the two-terminal TW based approach, a synchronization system based on the Global Positioning System (GPS) uses atomic clocks for time distribution and provides high-precision synchronization. However, there are several problems, such as errors caused by the atomic clocks in the GPS or offsets that lead to erroneous timing signals and erroneous synchronization. The GPS system is affected by the dynamics of the environment and external interference (such as geomagnetic storms, radio interference, electromagnetic interference from other devices, solar radio bursts, etc.), which causes temporary or permanent failures in function, resulting in poor data synchronization in the two-terminal TW based fault location technology. Therefore, there may be limited inaccuracies in the synchronization between the two ends of the IED, which may reach the order of tens of microseconds (μs), thereby reducing the accuracy of fault location.

[0018] Furthermore, the copper substation cables laid for transmitting the voltage and / or current signals from the measuring devices to the IED panels are different for each IED, these cables have different characteristics and lengths. Therefore, the characteristics of one substation cable differ from those of another, which results in different transmission speeds. This may introduce a limited time offset of about 3-5 μs in the measurements made at the two terminals of the transmission line, thereby introducing an error component in the fault location using two-terminal TW-based techniques.

[0019] Therefore, the total inaccuracy of data synchronization of the entire fault location (IED) system may be on the order of 30-50 μs, which may result in a 3km to 5km error in fault location of a 200km transmission line using a two-terminal TW-based approach. Sometimes, such delays can be calibrated and compensated by algorithms derived from experiments. However, this approach is cumbersome and costly because multiple field experiments need to be performed manually to achieve reasonably correct parameter calibration, and calibration needs to be performed regularly as physical conditions change over time. Therefore, calibration and compensation of these errors in two-terminal TW-based fault location techniques are expensive, time-consuming and impractical.

[0020] In addition, the fault location accuracy of TW-based methods depends largely on the wave velocity (inductance and capacitance of the transmission line per unit length). Wave velocity and line length are imprecise and are affected by many practical conditions such as weather, conductor age, temperature and sag. Wave velocity adjustment can be performed by creating faults at known distances. However, this requires experiments to adjust the wave velocity, which is a time-consuming and expensive process. In some setup-free fault location methods, both air and ground mode signals are required. Ground mode signals are severely attenuated and unreliable, and are only applicable to ground faults. Therefore, this setup-free fault location method can only be used for ground faults.

[0021] The present invention relates to fault location that is independent of line parameters and data synchronization. Therefore, fault location based on the method of the present invention eliminates synchronization errors and errors caused by changes in wave speed and line length due to changes in actual conditions such as weather, conductor age, temperature, sag, etc. In addition, the system and method of the present invention do not require experiments to calibrate the wave speed for deploying the fault location solution.

[0022] According to an example of the present invention, a fault location in a transmission line connecting a first terminal and a second terminal can be detected. An electrical fault (or interference) may exist at a specific location in the transmission line. Faults can be identified by evaluating measurements based on the first terminal and the second terminal. These measurements include current / voltage measurements made using measurement equipment. For example, the measurement equipment may include a current transformer, a voltage transformer, a sensor-based measurement equipment (e.g., a Rogowski coil, a non-traditional instrument transformer, etc.), etc., which provides a signal corresponding to a current, voltage, or other information sensed from the transmission line.

[0023] Traveling waves are generated when there is a fault in a transmission line. Traveling waves are temporary waves that create disturbances and move along the transmission line at a constant speed. Such waves have a short duration (a few microseconds) but can cause disturbances to the line.

[0024] According to an example of the present invention, multiple parameters related to the traveling wave detected from the measurements made at the first terminal and the second terminal can be obtained. The traveling wave and its parameters (e.g., arrival time, peak width, rise time, etc.) can be detected from the measurements made at the terminals (e.g., one or more signals received from the measurement equipment). For example, the current signal can be digitized and processed to detect the traveling wave.

[0025] A traveling wave is generated due to a fault and can be detected from measurements at the first terminal and the second terminal. A plurality of parameters related to the traveling wave detected from the measurements at the first terminal are obtained, and a plurality of parameters related to the traveling wave detected from the measurements at the second terminal are obtained. In an example, the measurements at the first terminal and the second terminal may not be synchronized. For example, if two IEDs obtain measurement values, the two IEDs (and / or corresponding measurement equipment) are not synchronized in time.

[0026] For a traveling wave detected from a measurement made at the first terminal, an arrival time of a first peak, an arrival time of a second peak, and an arrival time of a third peak are obtained. In an example, the first peak, the second peak, and the third peak correspond to the first, second, and third peaks of a current signal, which is digitized and processed to detect a traveling wave at the first terminal. Similarly, for a traveling wave detected from a measurement made at the second terminal, an arrival time of a first peak, an arrival time of a second peak, and an arrival time of a third peak are obtained. In an example, the first peak, the second peak, and the third peak correspond to the first, second, and third peaks of a current signal, which is digitized and processed to detect a traveling wave at the second terminal.

[0027] Furthermore, a rise time associated with a first peak of the traveling wave detected in the measurement from the first terminal is evaluated. Similarly, a rise time associated with a first peak of the traveling wave detected in the measurement from the second terminal is evaluated. Based on a comparison of the evaluated rise times of the first peak of the traveling wave, one of the first half and the second half of the transmission line is identified as having a fault. Thus, the faulty half of the transmission line is identified.

[0028] After the faulty half is identified, one of the first, second, third, and fourth sections of the transmission line is identified as having a fault based on identifying one of the first and second half sections as having a fault and comparing the arrival times of the first, second, and third peaks of the traveling wave. In addition, the length of the transmission line is evaluated based on identifying one of the first, second, third, and fourth sections as having a fault and comparing the arrival times of the first, second, and third peaks of the traveling wave, the arrival time of the first peak of the traveling wave reflected from the second terminal detected in the measurement from the first terminal, and the arrival time of the first peak of the traveling wave reflected from the first terminal detected in the measurement from the second terminal. The present invention includes evaluating the fault location based on identifying one of the first, second, third, and fourth sections as having a fault, the arrival times of the first, second, and third peaks of the traveling wave detected in the measurement from the first terminal and the second terminal, and the estimated length of the transmission line.

[0029] Therefore, the present invention is able to implement accurate fault location using asynchronous measurements of transmission lines. In addition, based on the technology of the present invention, line parameters such as wave speed are not required to determine the fault location. At the same time, the fault location accuracy is independent of processing (hardware and software) delays. In addition, GPS is not required for synchronization, which reduces system complexity, delay and cost. In addition, the technology of the present invention consumes less communication bandwidth than traditional technologies because the technology of the present invention only needs to transmit data on the arrival time of the three peaks of the traveling wave, thereby eliminating the need for a complete interference recorder. In addition, no experimental data / results are used to correct substation cable delays, software / hardware processing delays and wave speed errors. By dynamically evaluating the length of the transmission line based on the arrival time associated with the first three peaks of the traveling wave, the dependence on data synchronization between the two terminals and the dependence on line parameters can be eliminated in the fault location technology of the present invention.

[0030] The following detailed description refers to the accompanying drawings. Where possible, the same reference numerals are used in the drawings and the following description to refer to the same or similar parts. Although several examples are described in the specification, there may be modifications, adjustments and other implementations. Therefore, the following detailed description does not limit the disclosed examples. On the contrary, the appropriate scope of the disclosed examples can be defined by the appended claims.

[0031] Figure 1 A block diagram of a dual-source equivalent grid 100 for fault location according to an example is shown. Grid 100 includes a single transmission line 102 and two power sources, namely power sources 104 and 106. Grid 100 can transmit power at high voltages (such as in the kilovolt range) and over long distances (such as tens or hundreds of kilometers).

[0032] like Figure 1 As shown, the transmission line 102 is connected between two buses (bus A and bus B). The technology of the present invention can be implemented with one or more devices related to the transmission line. The device may include power system equipment (such as relays, intelligent electronic devices (IEDs) or fault locators) and / or servers connected to the power system equipment. Figure 1 As shown, IED 108 is associated with bus A (also referred to as the first terminal) and IED 110 is associated with bus B (also referred to as the second terminal). IEDs 108 and 110 may be in electrical communication with transmission line 102 directly or through other connection means. Figure 1As shown, IED 108 is located at bus A (first terminal) and detects traveling waves and acquires or evaluates required parameters / receives parameters for fault location from other power system devices (such as IED 110). IED 110 is located at bus B (second terminal) and detects traveling waves and acquires or evaluates required parameters / receives parameters for fault location from other power system devices (such as IED 108). During operation, IEDs 108 and 110 can receive data from one or more sensors and current transformers (CTs) installed within power grid 100.

[0033] For example, the IED 108 at the first terminal can obtain the traveling wave related parameters from the measurement at the first terminal and receive the traveling wave related measurement values ​​at the second terminal from the IED 110. In this example, the IED 108 can receive a signal from a measurement device such as a current transformer (CT) at the first terminal and obtain the measurement value therefrom, or the measurement device publishes the measurement value through a bus (e.g., a process bus) and the IED (e.g., configured to receive data from the bus) receives the measurement value through the bus. The traveling wave detection can be alternately performed on another power system device, and the obtained measurement value (or parameter) can be transmitted to the IED 108 or 110, or to a server implementing the method.

[0034] In an example, the steps of the method of the present invention may be performed by one or more modules. These modules may be implemented as instructions executable by one or more processors. For example, in an example where an IED (such as IEDs 108 and 110) performs the method, the modules are implemented using the processors of the IEDs 108 and 110. In other examples where a server performs the method, the modules may be implemented using the processors of the server. In the case where the method is partially implemented by an IED and partially implemented by a server, the modules (depending on the steps) will be distributed in the IED and the server accordingly.

[0035] IEDs 108 and 110 include traveling wave detectors 112 and 114, respectively. Traveling wave detectors 112 and 114 may be implemented as software installed within IEDs 108 and 110, or hardware in the form of electronic circuits. In an example, traveling wave detectors 112 and 114 may be coupled to (multiple) processors of IEDs 108 and 110. In another example, the traveling wave detectors may be stand-alone devices (connected to measurement equipment such as CTs at bus A or CTs at bus B).

[0036] In addition, the IEDs 108 and 110 include fault location modules 116 and 118 and fault location modules 120 and 122, respectively. The fault location modules 116 and 118 and the fault location modules 120 and 122 may be implemented as instructions executable by processors of the IEDs 108 and 110, or hardware in the form of electronic circuits. In addition, the IEDs 108 and 110 include communication interfaces 124 and 126. The communication interfaces 124 and 126 enable traveling wave related data to be exchanged between the IEDs 108 and 110 for fault location.

[0037] In operation, the traveling wave detector 112 of the IED 108 detects a first peak, a second peak, and a third peak of a traveling wave detected in a measurement made from the first terminal (bus A). Similarly, the traveling wave detector 114 of the IED 110 detects a first peak, a second peak, and a third peak of a traveling wave detected in a measurement made from the second terminal (bus B). The traveling wave detectors 112 and 114 obtain the arrival times of the first peak, the second peak, and the third peak of the traveling wave detected in the measurement made from the first terminal and the second terminal, respectively. In addition, the traveling wave detectors 112 and 114 calculate the rise time associated with the first peak of the traveling wave detected in the measurement made from the first terminal and the second terminal.

[0038] Consider T ART is the rise time of the first peak of the traveling wave detected from the measurement at the first terminal, T BRT is the rise time of the first peak of the traveling wave detected from the measurement at the second terminal. Figure 2a and 2b Specifically, if T ART Less than T BRT , the fault will be identified as occurring in the first half of the transmission line. Figure 2c and 2d Specifically, if T ART Greater than T BRT , the fault will be identified as occurring in the second half of the transmission line.

[0039] If T ART <T BRT →The fault is located in the first half of the line (1)

[0040] If T ART >T BRT →The fault is located in the second half of the line (2)

[0041] Thus, one of the first and second halves of the power transmission line is identified as having a fault based on a comparison of the rise times evaluated for the first peak of the traveling wave detected in the measurements taken at the first and second terminals.

[0042] In the following description, the modules and resources of IED 108 have been referred to as implementing the fault location function, however, the modules and other resources of IED 110 may be used to implement the fault location function with necessary modifications. In response to identifying the first half of the transmission line as being faulty, the fault location module 116 determines a first difference between the arrival times of the peaks of the traveling waves detected in the measurements taken at the first terminal (bus A). The first difference (t 1diff ) is the absolute difference between the arrival times of two consecutive peaks among the first peak, the second peak and the third peak of the traveling wave.

[0043] Therefore, t 1diff = abs((t A2 -t A1 )-(t A3 -t A2 )) (3)

[0044] Among them, t A1 represents the arrival time associated with the first peak of the travelling wave detected in the measurement made at the first terminal (bus A);

[0045] t A2 represents the arrival time associated with the second peak of the travelling wave detected in the measurement made at the first terminal (bus A);

[0046] and t A3 represents the arrival time associated with the third peak of the travelling wave detected in the measurement made at the first terminal (bus A).

[0047] When the first difference is almost equal to zero, the fault location module 116 identifies the first section as having a fault. The first section is within the range of one third of the length of the transmission line from the first terminal (bus A). When the first difference is greater than a predetermined threshold, the fault location module 116 identifies the second section as having a fault. The second section is within the range of one third of the length of the transmission line to one half of the length of the transmission line. Therefore,

[0048] t 1diff ~0→The fault is between the first terminal and one third of the line (first section) (4)

[0049] t 1diff >€→The fault is between one third and half of the line (second section) (5)

[0050] Where € is a predetermined threshold, which can be set to 2μs for a 1MHz sampling frequency.

[0051] In response to identifying the second half of the transmission line as faulty, the fault location module 116 determines a second difference between the arrival times of the peaks of the traveling waves detected in the measurements taken at the second terminal (bus B). In an example, the fault location module 116 may obtain the arrival times of the peaks of the traveling waves detected in the measurements taken at the second terminal from the IED 110 via the communication interface 126. The second difference (t 2diff ) is the absolute difference between the arrival times of two consecutive peaks of the first peak, the second peak and the third peak of the traveling wave detected from the measurement made at the second terminal.

[0052] Therefore, t 2diff = abs((t B2 -t B1 )-(t B3 -t B2 )) (6)

[0053] Among them, t B1 represents the arrival time associated with the first peak of the travelling wave detected in the measurement made at the second terminal (bus B);

[0054] t B2 represents the arrival time associated with the second peak of the travelling wave detected in the measurement made at the second terminal (bus B);

[0055] and t B3 represents the arrival time associated with the third peak of the travelling wave detected in the measurement made at the second terminal (bus B).

[0056] When the second difference is greater than a predetermined threshold, the fault location module 116 identifies the third section as having a fault. The third section is within a range from half the length of the transmission line to two-thirds the length of the transmission line. When the second difference is almost equal to zero, the fault location module 116 identifies the fourth section as having a fault. The fourth section is within a range from two-thirds the length of the transmission line to the second terminal (bus B). Therefore,

[0057] t 2diff >€→The fault is between half and two-thirds of the line (third section) (7)

[0058] t 2diff ~0→The fault is between two-thirds of the line and the second terminal (the fourth section) (8)

[0059] Where € is a predetermined threshold, which can be set to 2μs for a 1MHz sampling frequency.

[0060] Figure 2aThe Bewley dot diagram shows the case when the fault occurs in the first section of the transmission line (i.e., between the first terminal (bus A side) to one-third of the length of the transmission line). In this case, at the first terminal (bus A side), for the traveling wave generated from the fault point, the first peak, the second peak, and the third peak arrive from the fault point (i.e., not a reflection from the bus B side). As shown in the figure, on the bus B side, for the traveling wave generated from the fault point, the first peak arrives from the fault point, while the second peak arrives from the far-end bus (i.e., bus A side) due to the reflected wave. Similarly, on the bus A side, for the traveling wave generated from the fault point, at time The first reflected wave is received. The fault location can be calculated as follows. Figure 2a The Bewley dot diagram, we can write:

[0061]

[0062] Among them, t A0 represents the fault start time at the first terminal (bus A side), d1 represents the fault distance from the fault in the first section to the first terminal (bus A side), and v represents the wave speed.

[0063] The first two traveling wave arrival times in equation (9) can be used to calculate the fault location according to the following equation (10):

[0064]

[0065] In this case, equation (1) cannot be used to estimate the line length because there is no remote reflection or no wave traverses the entire length of the transmission line. To overcome this, the arrival time of the first remote reflection from remote terminal B at the first terminal (bus A side) can be recorded. Therefore, the first peak of the traveling wave reflected from the second terminal (bus B side) detected from the measurement made at the first terminal (bus A side) is expressed as

[0066] therefore,

[0067] in, represents the actual length of the transmission line; and

[0068] According to equations (9) and (11), the first evaluation length of the transmission line is It can be expressed as follows.

[0069]

[0070] in, A first evaluation length of the transmission line identified as a fault located in the first section is represented.

[0071] In response to identifying the first section as having a fault, the fault location module 120 calculates a first estimated length of the transmission line based on equation (12). As can be seen from equation (12), the first estimated length is proportional to the sum of the difference between the arrival times of the first and second peaks of the traveling wave detected in the measurement made at the first terminal (bus A side) and the difference between the arrival times of the first peak of the traveling wave reflected from the second terminal (bus B side) and the second peak of the traveling wave detected in the measurement made at the first terminal (bus A side).

[0072] Based on equations (10) and (12), for a fault identified as being located in the first section of the transmission line, the fault location per unit (d 1_pu ). Fault location (d 1_pu ) is the fault location per unit length.

[0073]

[0074] Therefore, as shown in equation (13), the fault location module 120 evaluates the fault location in the first section of the transmission line based on the ratio of the difference between the arrival times of the second and first peaks of the traveling wave detected from the measurement made at the first terminal (bus A side) to the first evaluation length.

[0075] Figure 2b The Bewley dot diagram shows the situation when the fault occurs in the second section of the transmission line (i.e., between one third and one half of the length of the transmission line). The fault location can be calculated as follows. According to Figure 2b The Bewley dot diagram, we can write:

[0076]

[0077] Among them, t A0 represents the fault start time at the first terminal (bus A side), d2 represents the fault distance from the first terminal (bus A side) to the fault in the second segment, represents the actual length of the transmission line, and v represents the wave speed.

[0078] The first two traveling wave arrival times of equation (14) can be used to calculate the fault location according to equation (15) below.

[0079]

[0080] According to equations (14) and (15), the second evaluation length of the transmission line is It can be expressed as follows in equation (16).

[0081]

[0082] in, A second evaluated length of the transmission line representing the fault identified as being located in the second section.

[0083] In response to identifying the second section as having a fault, the fault location module 120 estimates a second estimated length of the transmission line based on equation (16). As can be seen from equation (16), the second estimated length is proportional to the sum of the arrival times of the second and third peaks of the traveling wave detected from the measurement made at the first terminal (bus A side) and the difference between two times the arrival time of the first peak detected from the measurement made at the first terminal (bus A side).

[0084] Based on equations (15) and (16), for a fault identified as being located in the second section of the transmission line, the fault location (d 2_pu ). Fault location (d 2_pu ) is the fault location per unit length.

[0085]

[0086] Therefore, as shown in equation (17), the fault location module 120 evaluates the fault location in the second section of the transmission line based on the ratio of the difference between the arrival times of the second and first peaks of the traveling wave detected from the measurement made at the first terminal (bus A side) to the second evaluation length.

[0087] Figure 2c The Bewley dot diagram shows the situation when the fault occurs in the third section of the transmission line (i.e., between half and two-thirds of the length of the transmission line). The fault location can be calculated as follows. According to Figure 2c The Bewley dot diagram, we can write:

[0088]

[0089] Among them, t A0 represents the fault start time at the first terminal (bus A side), d3 represents the fault distance from the third segment to the first terminal (bus A side), represents the real length of the transmission line, and v represents the wave speed. The fault location can be calculated according to the following equation (19) using the first two traveling wave arrival times in equation (18).

[0090]

[0091] In response to identifying the third section as having a fault, the fault location module 120 estimates a second estimated length of the transmission line based on equation (16). As can be seen from equation (16), the second estimated length is proportional to the sum of the arrival times of the second and third peaks of the traveling wave detected from the measurement made at the first terminal (bus A side) and the difference between two times the arrival time of the first peak detected from the measurement made at the first terminal (bus A side).

[0092] Based on equations (19) and (16), for a fault identified as being located in the third section of the transmission line, the fault location (d 3_pu ). Fault location (d 3_pu ) is expressed as fault location per unit length.

[0093]

[0094] Therefore, as shown in equation (20), the fault location module 120 evaluates the fault location in the second section of the transmission line based on the ratio of the difference between the arrival times of the third and first peaks of the traveling wave detected from the measurement made at the first terminal (bus A side) to the second evaluation length.

[0095] Figure 2d The Bewley dot diagram shows the situation when a fault occurs in the fourth section of the transmission line, ie, between two-thirds of the length of the transmission line to the second terminal (bus B side).

[0096] The fault location can be calculated as follows. Figure 2d The Bewley dot diagram of , we can write in terms of the first terminal:

[0097]

[0098] Among them, t A0 represents the fault start time at the first terminal (bus A side), d4 represents the fault distance from the first terminal (bus A side) to the fault in the fourth segment, represents the actual length of the transmission line, and v represents the wave speed.

[0099] according to Figure 2d The Bewley dot diagram of , we can write in terms of the second terminal:

[0100]

[0101] Among them, t B0 Indicates the fault start time at the second terminal (bus B side).

[0102] The first two traveling wave arrival times in equation (21) can be used to calculate the fault location according to the following equation (22),

[0103] In this case, equation (21) cannot be used to estimate the line length because there is no remote reflection from the first terminal (bus A side) of the transmission line. To overcome this, the arrival time of the first remote reflection from the remote first terminal (bus A side) at the second terminal (bus B side) can be recorded. Therefore, the first peak of the traveling wave reflected from the first terminal (bus A side) detected in the measurement made at the second terminal (bus B side) is expressed as therefore,

[0104] According to equations (22) and (23), the third evaluation length of the transmission line is It can be expressed as follows.

[0105]

[0106] in, A third evaluation length of the transmission line identified as a fault located in the fourth section is represented.

[0107] In response to identifying the fourth section as having a fault, the fault location module 120 estimates a third evaluation length of the transmission line based on equation (25). As can be seen from equation (25), the third evaluation length is proportional to the sum of the difference between the arrival times of the first and second peaks of the traveling wave detected in the measurement made at the second terminal (bus B side) and the difference between the arrival times of the first peak of the traveling wave reflected from the first terminal (bus A side) and the second peak of the traveling wave detected in the measurement made at the second terminal (bus B side).

[0108] Based on equations (23) and (24), for a fault identified as being located in the fourth section of the transmission line, the fault location (d 4_pu ). Fault location (d 4_pu ) is the fault location per unit length.

[0109]

[0110] Therefore, as shown in equation (26), the fault location module 120 evaluates the fault location in the fourth section of the transmission line based on the ratio of the sum of the difference between the arrival times of the first and second peaks of the traveling wave detected in the measurement made from the second terminal (bus B side) and the difference between the arrival times of the first peak of the traveling wave reflected from the first terminal and the second peak of the traveling wave detected in the measurement made from the second terminal (bus B side) to the third evaluation length.

[0111] Figure 3a and 3b A method 300 for fault location in a transmission line according to an example is shown. The method 300 may be performed by a device such as an IED 108 or 110. The method 300 may be implemented by (multiple) processing resources or an electrical control system through any suitable hardware, programmable instructions, or a combination thereof. In an example, (multiple) steps of the method 300 may be performed by hardware or programming modules, such as a traveling wave detector 112 or 114, a fault location module 116 or 118, and a fault location module 120 or 122. In addition, although the method 300 is described in the context of the aforementioned IEDs 108 and 110, a server or other suitable system may be used to perform the method 300. It is understood that the processes involved in the method 300 may be performed based on instructions stored in a non-transitory computer-readable medium. The non-transitory computer-readable medium may include, for example, a digital memory, a magnetic storage medium (such as a disk and a tape), a hard drive, or an optically readable digital data storage medium.

[0112] Referring to FIG. 3A , measurements related to traveling waves at each terminal (bus A side and bus B side) of a power transmission line are received. In an example, a terminal may be a bus (such as Figure 1 A or B), and the transmission line can be Figure 1 Transmission line 102 is shown with an IED, such as IED 108 or 110, coupled thereto. At block 302, a first peak, a second peak, and a third peak of a traveling wave detected from measurements taken at a first terminal and a second terminal are detected.

[0113] At block 304, the arrival times of the first peak, the second peak, and the third peak of the traveling wave detected from the measurements made at the first terminal and the second terminal are obtained. In an example, the arrival times may be measured at the first terminal and the second terminal by measurement equipment (such as CT or PT, etc.) and may be transmitted to the IEDs 108 and 110. In an example, reference is made to Figure 1, the IED 108 can receive the measured values ​​of the arrival times of the first peak, the second peak, and the third peak of the traveling wave detected from the measurement made at the second terminal (bus B side) through the communication link between the IEDs 108 and 110, and vice versa. Therefore, each intelligent electronic device (such as IED 108 or 110) associated with one of the first terminal and the second terminal receives the measurement made at each of the first terminal and the second terminal from at least one of the communication interface and the measurement equipment associated with each of the first terminal and the second terminal.

[0114] At block 306, a rise time (T) associated with a first peak of a traveling wave detected in a measurement from a first terminal is calculated. ART Similarly, at block 308, a rise time (T ) associated with a first peak of the traveling wave detected in the measurement from the second terminal is calculated. BRT ). ART represents the rise time of the first peak of the traveling wave detected in the measurement from the first terminal (bus A side), and T BRT is the rise time of the first peak of the traveling wave detected from the measurement at the second terminal (bus B side).

[0115] At block 310, T ART and T BRT At block 312, if T ART Less than T BRT ("Yes" branch from block 310), the fault is identified as being located in the first half of the transmission line. At block 314, if T ART Greater than T BRT ("No" branch from block 310), the fault is identified as being located in the second half of the transmission line.

[0116] At block 316, in response to identifying the first half of the transmission line as faulty, a first difference between the arrival times of the peaks of the traveling waves detected from the measurements taken at the first terminal (bus A side) is determined. As shown in equation (3), the first difference (t 1diff ) is the absolute difference between the arrival times of two consecutive peaks among the first peak, the second peak and the third peak of the traveling wave.

[0117] At block 318, the first difference (t 1diff) is almost equal to zero. At box 320, when the first difference is almost equal to zero (the "yes" branch from box 310), the first section is identified as having a fault. The first section is within a range of one-third of the length of the transmission line from the first terminal (bus A). At box 324, when the first difference is greater than a predetermined threshold, the second section is identified as having a fault. The second section is within a range of from one-third of the length of the transmission line to one-half of the length of the transmission line. The first and second sections are identified based on equations (4) and (5).

[0118] At block 326, in response to identifying the second half of the transmission line as faulty, a second difference between the arrival times of the peaks of the traveling waves detected from the measurements taken at the second terminal (bus B) is detected. As shown in equation (6), the second difference (t 2diff ) is the absolute difference between the arrival times of two consecutive peaks of the first peak, the second peak and the third peak of the traveling wave detected from the measurement made at the second terminal.

[0119] At box 328, it is checked whether the second difference is almost equal to zero. At box 330, when the second difference is almost equal to zero, the third section is identified as having a fault. The third section is in the range from half of the length of the transmission line to two-thirds of the length of the transmission line. At box 332, when the second difference is greater than a predetermined threshold, the fourth section is identified as having a fault. The fourth section is in the range from two-thirds of the length of the transmission line to the second terminal (bus B). The third and fourth sections are identified based on equations (7) and (8).

[0120] At block 334, in response to identifying the first section as having a fault, a first estimated length of the transmission line is calculated based on equation (12). As can be seen from equation (12), the first estimated length is proportional to the sum of the difference between the arrival times of the first and second peaks of the traveling wave detected in the measurement made at the first terminal (bus A side), and the difference between the arrival times of the first peak of the traveling wave reflected from the second terminal (bus B side) and the second peak of the traveling wave detected in the measurement made at the first terminal (bus A side).

[0121] Based on equations (10) and (12), for a fault identified as being located in the first section of the transmission line, the fault location (d 1_pu ). Fault location (d 1_pu ) is expressed as the fault location per unit length. Therefore, at block 336, as shown in equation (13), the fault location in the first section of the transmission line is estimated based on the ratio of the difference between the arrival times of the second and first peaks of the traveling wave detected from the measurement at the first terminal (bus A side) to the first evaluation length.

[0122] In response to identifying the second section or the third section as having a fault at blocks 324 and 330, at block 338, a second estimated length of the transmission line is calculated based on equation (16). As can be seen from equation (16), the second estimated length is proportional to the sum of the arrival times of the second and third peaks of the traveling wave detected from the measurement made at the first terminal (bus A side) and the difference between two times the arrival time of the first peak detected from the measurement made at the first terminal (bus A side).

[0123] Based on equations (15) and (16), for a fault identified as being located in the second section of the transmission line, the fault location (d 2_pu ). Fault location (d 2_pu ) is expressed as the fault location per unit length. Therefore, at block 340, as shown in equation (17), the fault location in the second section of the transmission line is estimated based on the ratio of the difference between the arrival times of the second and first peaks of the traveling wave detected from the measurement at the first terminal (bus A side) to the second evaluation length.

[0124] Based on equations (19) and (16), for a fault identified as being located in the third section of the transmission line, the fault location (d 3_pu ). Fault location (d 3_pu ) is expressed as a fault location per unit length. Therefore, at block 342, as shown in equation (20), the fault location in the third section of the transmission line can be evaluated based on the ratio of the difference between the arrival times of the third and first peaks of the traveling wave detected from the measurement at the first terminal (bus A side) to the second evaluation length.

[0125] At block 344, in response to identifying the fourth section as having a fault, a third estimated length of the transmission line is calculated based on equation (24). As can be seen from equation (24), the third estimated length is proportional to the sum of the difference between the arrival times of the first and second peaks of the traveling wave detected in the measurement made at the second terminal (bus B side) and the difference between the arrival times of the first peak of the traveling wave reflected from the first terminal (bus A side) and the second peak of the traveling wave detected in the measurement made at the second terminal (bus B side).

[0126] Based on equations (24) and (25), for a fault identified as being located in the fourth section of the transmission line, the fault location (d 4_pu ). Fault location (d 4_pu) is expressed as the fault location per unit length. Therefore, at block 346, as shown in equation (25), the fault location in the fourth section of the transmission line is evaluated based on the ratio of the sum of the difference between the arrival times of the first and second peaks of the traveling wave detected in the measurement made at the second terminal (bus B side) and the difference between the arrival times of the first peak of the traveling wave reflected from the first terminal and the second peak of the traveling wave detected in the measurement made at the second terminal (bus B side) to the third evaluation length.

[0127] The proposed method and apparatus of the invention are tested to determine the technical feasibility. In an example, simulation results of a system consisting of a 200km transmission line are discussed below to determine the technology of the present invention. In this example, four examples covering all sections (first section, second section, third section and fourth section) of the transmission line are considered to test the accuracy of the present invention.

[0128] Example Fault location (km) The faulty section of the transmission line 1 50 Paragraph 1 2 90 Paragraph 2 3 110 Paragraph 3 4 150 Paragraph 4

[0129] The test examples include different fault locations at 50, 90, 110 and 150 km from the first terminal (bus A side), and with data synchronization and beam speed errors. Figure 4a and 4b As shown in Table I, it is observed that even with a small error in time synchronization (eg, 1 μs), the accuracy of conventional fault location techniques is significantly affected. However, the method and apparatus of the present invention maintains its accuracy even with higher synchronization errors.

[0130] The method of the present invention was also tested for wave velocity variations in the range of 0.5% to 10%. It can be observed that for faults in the first and fourth segments, the error increases significantly using the conventional method, while the accuracy is not affected using the method of the present invention. The results are shown in Figure 5a and 5b As shown in Table II.

[0131] Based on the above results, it can be concluded that the present invention involving parameter-independent traveling wave-based fault location using asynchronous measurements is more accurate than traditional fault location techniques. The method of the present invention has also been verified for different synchronization and wave velocity errors. For the traditional two-terminal method, the fault location error will increase due to higher synchronization and wave velocity errors, while the accuracy of the method of the present invention is consistent and independent of data synchronization and wave velocity errors. The test results of fault location show that the method of the present invention is not affected by fault location, fault type, arc resistance, fault start angle, measurement noise and nonlinear high impedance faults. According to simulation results, a fault location accuracy of ±150m can be achieved for a test system using a 200km line. Although the derivation and simulation are performed on AC transmission lines, the concept can also be extended to DC transmission lines. In the example, the present invention can be implemented in an IED, which does not require GPS-based synchronization or field experiments to adjust different components and wave velocity (line parameter) errors, thereby saving costs during actual deployment.

[0132] Although the embodiments of the present subject matter have been described using language specific to structural features and / or methods, it should be noted that the present subject matter is not necessarily limited to the specific features or methods described. Rather, specific features and methods are disclosed and explained in the context of some embodiments of the present subject matter.

Claims

1. A method for locating a fault in a power transmission line connecting a first terminal and a second terminal, the method comprising: Obtaining arrival times of a first peak, a second peak, and a third peak of a traveling wave detected in measurements taken at each of the first terminal and the second terminal; calculating a rise time associated with a first peak of a traveling wave detected in measurements taken from the first terminal and the second terminal; identifying one of a first half and a second half of the transmission line as having a fault based on a comparison of rise times of first peak estimates of the traveling wave at the first terminal and the second terminal; Based on the identification of a fault in one of the first half and the second half and the comparison of the arrival times of the first peak, the second peak and the third peak of the traveling wave at the first terminal and the second terminal, identifying one of the first section, the second section, the third section and the fourth section of the transmission line as having a fault; assessing the length of the transmission line based on identifying the presence of a fault in one of the first, second, third and fourth segments and comparing the arrival times of the first, second and third peaks of the traveling wave, the arrival time of the first peak of the traveling wave reflected from the second terminal detected in measurements made at the first terminal, and the arrival time of the first peak of the traveling wave reflected from the first terminal detected in measurements made at the second terminal; as well as The fault location is assessed based on the identification of a fault in one of the first, second, third and fourth sections, the arrival times of the first, second and third peaks of the traveling wave detected from the measurements taken at the first terminal and the second terminal, and the assessed length of the transmission line.

2. The method of claim 1, wherein: If T ART Less than T BRT , the fault is identified as being located in the first half of the transmission line if T ART Greater than T BRT , then the fault is identified as being located in the second half of the transmission line, where T ART is the rise time of the first peak of the traveling wave detected from the measurement at the first terminal, T BRT is the rise time of the first peak of the travelling wave detected in the measurement taken at the second terminal.

3. The method according to claim 1 or 2, wherein: Identifying one of the first section, the second section, the third section, and the fourth section of the transmission line as having a fault includes: In response to identifying the first half of the transmission line as being faulty: determining a first difference between the arrival times, wherein the first difference is an absolute difference between arrival times of two consecutive peaks of a first peak, a second peak, and a third peak of the traveling wave detected from the measurement performed at the second terminal; When the first difference is almost equal to zero, identifying the first section as having a fault, wherein the first section is within a range of one third of the length from the first terminal to the transmission line; and When the first difference is greater than a predetermined threshold, identifying the second section as having a fault, wherein the second section is within a range of one third of the length of the transmission line to one half of the length of the transmission line; and In response to identifying the second half of the transmission line as faulty: determining a second difference between the arrival times, wherein the second difference is an absolute difference between arrival times of two consecutive peaks among a first peak, a second peak, and a third peak of the traveling wave detected from the measurement made at the second terminal; When the second difference is greater than the predetermined threshold, identifying the third section as having a fault, wherein the third section is within a range of one half of the length of the transmission line to two thirds of the length of the transmission line; and When the second difference is almost equal to zero, the fourth section is identified as having a fault, wherein the fourth section is within a range from two-thirds of the length of the transmission line to the second terminal.

4. The method of claim 3, wherein: Estimating the length of the transmission line includes: In response to identifying the first section as being faulty, calculating a first estimated length of the transmission line, the first estimated length being proportional to the sum of a difference between arrival times of a first peak and a second peak of a traveling wave detected in measurements taken from the first terminal, and a difference between arrival times of a first peak of a traveling wave reflected from the second terminal and arrival times of a second peak of the traveling wave detected in measurements taken from the first terminal; In response to identifying one of the second section and the third section as having a fault, calculating a second estimated length of the transmission line, the second estimated length being proportional to a difference between a sum of arrival times of a second peak and a third peak of the traveling wave detected in measurements from the first terminal and two times an arrival time of a first peak detected in measurements from the first terminal; and In response to identifying the fourth section as having a fault, a third evaluation length of the transmission line is calculated, the third evaluation length being proportional to the sum of the difference between the arrival times of the first peak and the second peak of the traveling wave detected in the measurement from the second terminal, and the difference between the arrival time of the first peak of the traveling wave reflected from the first terminal and the arrival time of the second peak of the traveling wave detected in the measurement from the second terminal.

5. The method of claim 4, wherein: The fault location in the first section of the transmission line is evaluated based on the ratio of the difference between the arrival times of the second peak and the first peak of the traveling wave detected in the measurement made from the first terminal to the first evaluation length, and the fault location in the first section is expressed as a fault location per unit length.

6. The method of claim 4, wherein: The fault position in the second section of the transmission line is evaluated based on the ratio of the difference between the arrival time of the second peak and the first peak of the traveling wave detected in the measurement made from the first terminal to the second evaluation length, and the fault position in the second section is expressed as a fault position per unit length.

7. The method of claim 5, wherein: The fault position in the second section of the transmission line is evaluated based on the ratio of the difference between the arrival time of the second peak and the first peak of the traveling wave detected in the measurement made from the first terminal to the second evaluation length, and the fault position in the second section is expressed as a fault position per unit length.

8. The method according to any one of claims 4 to 7, wherein: Based on the ratio of the difference between the arrival time of the third peak and the first peak of the traveling wave detected in the measurement made from the first terminal to the second evaluation length, the fault position in the third section of the transmission line is evaluated, and the fault position in the third section is expressed as a fault position per unit length.

9. The method according to any one of claims 4 to 7, wherein: The fault location in the fourth section of the transmission line is evaluated based on the ratio of the sum of the difference between the arrival times of the first peak and the second peak of the traveling wave detected in the measurement made from the second terminal, and the difference between the arrival times of the first peak of the traveling wave reflected from the first terminal and the second peak of the traveling wave detected in the measurement made from the second terminal, to the third evaluation length, and the fault location in the fourth section is expressed as a fault location per unit length.

10. The method of claim 8, wherein: The fault location in the fourth section of the transmission line is evaluated based on the ratio of the sum of the difference between the arrival times of the first peak and the second peak of the traveling wave detected in the measurement made from the second terminal, and the difference between the arrival times of the first peak of the traveling wave reflected from the first terminal and the second peak of the traveling wave detected in the measurement made from the second terminal, to the third evaluation length, and the fault location in the fourth section is expressed as a fault location per unit length.

11. A device for locating a fault in a power transmission line connecting a first terminal and a second terminal, the device comprising: Travelling wave detectors for: detecting a first peak, a second peak, and a third peak of a traveling wave detected from measurements taken at the first terminal and the second terminal; Obtaining arrival times of a first peak, a second peak, and a third peak of a traveling wave detected in measurements taken at the first terminal and the second terminal; as well as calculating a rise time associated with a first peak of a traveling wave detected in measurements taken from the first terminal and the second terminal; The fault location module is configured as follows: identifying one of a first half and a second half of the transmission line as having a fault based on a comparison of the calculated rise time associated with a first peak of the traveling wave; Based on the identification of a fault in one of the first half and the second half of the transmission line and the comparison of the arrival times of the first peak, the second peak and the third peak of the traveling wave, identifying one of the first section, the second section, the third section and the fourth section of the transmission line as having a fault; A fault location module, coupled to the processor, is configured to: assessing the length of the transmission line based on identifying the presence of a fault in one of the first, second, third and fourth segments and comparing the arrival times of the first, second and third peaks of the traveling wave, the arrival time of the first peak of the traveling wave reflected from the second terminal detected in measurements made at the first terminal, and the arrival time of the first peak of the traveling wave reflected from the first terminal detected in measurements made at the second terminal; as well as The fault location is assessed based on the identification of a fault in one of the first, second, third and fourth sections, the arrival times of the first, second and third peaks of the traveling wave detected from the measurements taken at the first terminal and the second terminal, and the assessed length of the transmission line.

12. The device of claim 11, wherein: The device is an intelligent electronic device associated with one of the first terminal and the second terminal, wherein the device receives measurements made at each of the first terminal and the second terminal from at least one of a communication interface and a measurement equipment associated with each of the first terminal and the second terminal.

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