Distance protection of power transmission lines

Abstract

The present disclosure relates to a method for distance protection of an electric power line carrying multiple phases, the method including obtaining a first impedance of a first electrical loop formed by a first phase and ground potential carried on the electric power line based on a zero sequence current, obtaining a second impedance of a second electrical loop formed by a second phase and ground potential carried on the electric power line based on the zero sequence current, calculating an apparent impedance of the electric power line seen at a first terminal based on the first impedance and the second impedance, and performing distance protection based on the apparent impedance. The present disclosure also relates to respective apparatus, computer readable media, and systems.

Description

[Technical Field]

[0001] This disclosure relates to methods, apparatus, computer-readable media, and systems for performing distance protection of power transmission lines connecting generators. [Background technology]

[0002] Electric grids, particularly those with generators connected to transmission lines, especially distributed generators, require stringent fault ride-through conditions to prevent further propagation of faults through the grid network, thereby ensuring a reliable power supply even in the presence of grid faults. Many systems implement relays along the transmission lines and, in the event of fault detection, control the relays to achieve electrical isolation of the faulty line. In particular, the distance protection principle determines the fault location relative to the relay's position by calculating its electrical characteristics, especially the apparent impedance seen from the relay. Relays within the grid are controlled based on the calculated fault location.

[0003] Conventional synchronous generators exhibit different electrical characteristics compared to distributed energy resources (DERs), particularly asynchronous generators. The frequency of the generated electricity differs from the grid's operating frequency and therefore must be synchronized via an inverter. Thus, such generators are also called inverter-based resources (IBRs), including photovoltaic generators and wind turbine generators. Existing line protection, especially distance protection, calculates fault locations based on the electrical characteristics of synchronous generators, leading to significant errors when considering asynchronous generators. [Overview of the project] [Means for solving the problem]

[0004] Below, we present systems with two synchronous generators and systems with one synchronous generator and one asynchronous generator. Furthermore, we present the apparent impedance calculation method and their performance, along with the attached diagrams.

[0005] Figures 1a) and 1b) show schematic diagrams of a two-terminal transmission line system connected to a generator. Figure 1a) shows a schematic diagram of a two-terminal transmission line system connecting two synchronous generators. The two-terminal transmission line system 100, operating at 220kV and 50Hz, comprises a first synchronous generator 101 connected to a second synchronous generator 102 via a transmission line 110. The transmission line 110 is terminated on one side by BUS N (equivalently terminal N or remote terminal) 111 toward the first synchronous generator 101 and on the other side by BUS M (equivalently terminal M or local terminal) 112 toward the second synchronous generator 102. The distance between terminal N111 and terminal M112 is 100km in this example. Terminal M112 comprises a distance relay controlled by a relay, in particular a distance protection control method. A voltmeter 122 monitors the voltage at terminal M112 and supplies the measurement to an intelligent electronic device (IED) 121. An ammeter 123 measures the current at terminal M112 and supplies the measurement to the IED 121. The IED 121 is configured to perform any calculations necessary for the distance protection method. The fault 131 is located at any point on the transmission line 110 between the distance covered by terminals M112 and N111.

[0006] Figure 1b) shows a schematic diagram of a two-terminal transmission line system connecting one synchronous generator and one asynchronous generator via delta-y, Δ-Y, transformers and y-delta, Y-Δ, transformers. The Δ-Y transformer can distribute a single-phase load to a neutral point among three phases, while the Y-Δ transformer does the opposite. The two-terminal transmission line system 150, operating at 220kV and 50Hz, includes a first synchronous generator 151 connected to a second asynchronous generator (multiple wind turbines) 154 via a Y-Δ transformer 153 and a Δ-Y transformer 152 using a transmission line 160. In this example, each wind turbine has a rated active power of 2MW, and 100 wind turbines are considered. The transmission line 160 is terminated on one side by BUS N (equivalently terminal N or remote terminal) 161 toward a first synchronous generator 151 and on the other side by BUS M (equivalently terminal M or local terminal) 162 toward a second asynchronous generator 162. The distance between terminal N251 and terminal M152 is, exemplary, 100 km. Terminal M152 is equipped with a distance relay controlled by a relay, in particular a distance protection control method. A voltmeter 172 monitors the voltage at terminal M162 and supplies the measurement to an IED 171. An ammeter 173 measures the current at terminal M162 and supplies the measurement to an IED 171. The IED 171 is configured to perform any calculations required by the distance protection method of the present disclosure. A fault 181 is located at any point on the transmission line 160 between the distance covered by terminal M162 and terminal N161.

[0007] Figure 2 is an equivalent circuit diagram of a phase B-phase C-ground (BC-g) fault in a power transmission line system, particularly the system disclosed in Figures 1a) and 1b). The power transmission line comprises a first line 210 carrying a first phase (phase A), a second line 220 carrying a second phase (phase B), and a third line 230 carrying a third phase (phase C). The voltage phasors corresponding to phases A, B, and C, measured at terminals M112 and 162, are V, respectively. AM , V BM , and V CM It is shown as follows. Similarly, the voltage phasors corresponding to phases A, B, and C measured at terminals N111 and 161 are, respectively, V AN, V BN and V CN are shown as. The current phasors corresponding to phases B and C measured at terminals M112 and 162 are respectively I BM and I CM as shown. Similarly, the current phasors corresponding to phases B and C measured at terminals N111 and 161 are respectively I BN and I CN as shown. The line impedance from terminal M to the fault points F131, 181 is Z F as shown. The obstacle resistance components between phases and phase to ground are respectively R pp and R pg as shown. The electrical loop formed by the faults in phases B and C is Z F , R pp , and R pg and is called a phase - phase - ground loop.

[0008] The apparent impedance calculation method includes the following steps. Applying Kirchhoff's voltage law (KVL) to the first phase - to - ground (phase B - to - ground) loop, the first voltage equation is obtained as follows.

[0009]

Equation

[0010] Similarly, applying KVL to the second phase - to - ground (phase C - to - ground) loop, the second voltage equation is obtained as follows.

[0011]

Equation

[0012] R pp =R pg, Assuming, calculating the voltage difference between Equation (1) and Equation (2) gives the following.

[0013]

Equation

[0014] Here, R F was obstacle resistance Show, R pp =R pg This is equivalent to the current difference I. BM- I CM Dividing by this gives the conventional apparent impedance.

[0015]

number

[0016] Here, N and D are terms ((I in equation (4) BM -I CM +I BN -I CN ) / (I BM -I CM The numerator and denominator of ((I)) are shown. N and D are complex current terms, and therefore, as the phase angle between N and D converges to 0, the term ((I BM -I CM +I BN -I CN ) / (I BM -I CM The term ((I BM -I CM +I BN -I CN ) / (I BM -I CM The imaginary part of ((I BM -I CM +I BN -I CN ) / (I BM -I CMThis makes the (I BM -I CM +I BN -I CN ) / (I BM -I CM Make sure that )) includes a significant imaginary part. As is clear from equation (4), the calculated apparent impedance Z in equation (4) app The imaginary part of is R F and term ((I BM -I CM +I BN -I CN ) / (I BM -I CM It changes linearly with the imaginary part of ). Therefore, the height R F A heterogeneous system having the calculated apparent impedance Z in equation (4) app This causes a significant shift in the reactance. The calculated apparent impedance Z in equation (4) app The effect of the large reactance shift is shown in the following explanation with reference to the attached diagram. Here, calculating the apparent impedance according to equation (4) is called the first method for calculating the apparent impedance. Thus, the first apparent impedance refers to the apparent impedance calculated according to the first method.

[0017] Figure 3 shows that 0 ohms obstacle resistance (Equivalently, R F The apparent impedance performance calculated according to the first method is shown for the homogeneous and heterogeneous systems in Figure 1a), taking into account (=0Ω).

[0018] Angle plots 351 and 352 show the terms ((I) in equation (4) over the measurement period for homogeneous and heterogeneous systems. BM -I CM +I BN -I CN ) / (I BM -I CMThe simulation results of the phase angle difference between the numerator (N)301 and the denominator (D)302 of the equation are shown. The y-axis of angle plots 351 and 352 is the angle in degrees, and its x-axis is time. A 60% phase-phase-ground fault is assumed, and as a result, the apparent impedance Z of the actual fault is shown. true = 2.14 + 30.46j, where j represents an imaginary number, and the fault onset is 0.1s. Trajectory plots 353 and 354 show the simulation results of the trajectories for each apparent impedance 311 and zone 1 impedance boundary 312. Each trajectory of apparent impedance 311 in trajectory plots 353 and 354 follows the first apparent impedance over time within the time frame shown in angle plots 351 and 352. The y-axis of trajectory plots 353 and 354 is a virtual value, and the x-axis is a real value. Apparent impedance calculations 355 and 356 calculate the apparent impedance of the phase-phase-ground fault using equation (4) and represent the settling apparent impedance that each trajectory of apparent impedance 311 ultimately reaches within the time frame shown in angle plots 351 and 352.

[0019] In a homogeneous system, the phase angle difference between the numerator 301 and the denominator 302 measured after the onset of a failure is approximately 12°. The apparent impedance calculation 355 is R F For a system having = 0Ω, term ((I BM -I CM +I BN -I CN ) / (I BM -I CM This shows that )) does not cause any reactance shift to the calculated apparent impedance. Therefore, the first apparent impedance calculated in apparent impedance calculation 355 is equal to the actual fault impedance.

[0020] In a heterogeneous system, the phase angle difference between the numerator 301 and the denominator 302 measured after the onset of failure is approximately 36°. The apparent impedance calculation 356 is R F For a system having = 0Ω, term ((I BM -I CM+I BN -I CN ) / (I BM -I CM ) shows that, despite the significant phase angle difference, the apparent impedance calculated by the apparent impedance calculation 356 does not cause any reactance shift in the apparent impedance. Therefore, the apparent impedance calculated by the apparent impedance calculation 356 is equal to the actual fault impedance.

[0021] Figure 4 shows the performance of the apparent impedance calculated according to the first method in the homogeneous and heterogeneous systems shown in Figure 1a), considering a 20 ohm fault obstacle resistance (equivalently, R F = 20 Ω).

[0022] Angle plots 451 and 452 show the simulation results of the phase angle difference between the numerator (N) 401 and the denominator (D) 402 of the term ((I BM -I CM +I BN -I CN ) / (I BM -I CM )) in Equation (4) over the measurement period for the homogeneous and heterogeneous systems respectively. The y-axis of angle plots 451 and 452 is the angle in degrees and the x-axis is time. A 60% phase-phase-ground fault is assumed, and as a result, the actual fault apparent impedance Z trueIt becomes 2.14 + 30.46j, where j represents an imaginary number, and the fault starts at 0.1 s. Trajectory plots 453 and 454 show the simulation results of the trajectories of the respective apparent impedances 411 and the zone 1 impedance boundary 412. Each trajectory of the apparent impedance 411 in trajectory plots 453 and 454 follows the first apparent impedance over time within the time frames shown in angle plots 451 and 452. The y-axis of trajectory plots 453 and 454 is a virtual value, and the x-axis is a real value. Apparent impedance calculations 455 and 456 calculate the apparent impedance of the phase-phase-ground fault using Equation (4) and represent the setting apparent impedance at which each trajectory of apparent impedance 411 finally reaches within the time frames shown in angle plots 451, 452.

[0023] In a homogeneous system, the phase angle difference between the numerator 401 and the denominator 402 measured after the fault starts is approximately 8°. Apparent impedance calculation 455 is for a system with R F = 20 Ω, and the term ((I BM - I CM + I BN - I CN ) / (I BM - I CM )) causes a shift in both the real and imaginary components of the apparent impedance. Nevertheless, the calculated apparent impedance still lies within the boundary of zone 1. In other words, it is determined that the fault occurred within the distance covered by the two terminals of BUS M112 and BUS N111.

[0024] In a heterogeneous system, the phase angle difference between the numerator 401 and the denominator 402 measured after the fault starts is approximately 30°. Apparent impedance calculation 456 is for a system with R F = 20 Ω, and the term ((I BM - I CM + I BN - I CN ) / (I BM - I CMThis shows that )) causes a shift in both the real and imaginary components of the apparent impedance. As a result, the apparent impedance is not stable at a point within the boundary of Zone 1. In other words, it is determined that no fault has occurred within the distance covered by the two terminals of BUS M112 and BUS N111.

[0025] Figure 5 shows the values ​​for 0 ohms and 20 ohms. obstacle resistance The apparent impedance performance calculated according to the first method, taking into consideration, is shown, particularly in heterogeneous systems as shown in Figure 1b).

[0026] Angle plots 551 and 552 are for 0 ohms and 20 ohms respectively. obstacle resistance In a heterogeneous system that takes this into consideration, over the measurement period, the term ((I in equation (4)) BM -I CM +I BN -I CN ) / (I BM -I CM The simulation results of the phase angle difference between the numerator (N)501 and the denominator (D)502 of the equation are shown. The y-axis of angle plots 551 and 552 is the angle in degrees, and its x-axis is time. A 60% phase-phase-ground fault is assumed, and as a result, the apparent impedance Z of the actual fault is shown. true =2.14+30.46j, where j represents an imaginary number, and the fault onset is 0.6s. Trajectory plots 553 and 554 show the simulation results of the trajectories for each apparent impedance 511 and zone 1 impedance boundary 512. Each trajectory of apparent impedance 511 in trajectory plots 553 and 554 follows the apparent impedance calculation over time within the time frame shown in angle plots 551 and 552. The y-axis of trajectory plots 553 and 554 is a virtual value, and the x-axis is a real value. Apparent impedance calculations 555 and 556 calculate the apparent impedance of the phase-phase-ground fault using equation (4) and represent the settling apparent impedance that each trajectory of apparent impedance 511 ultimately reaches within the time frame shown in angle plots 551 and 552.

[0027] In a heterogeneous system, the phase angle difference between the numerator 501 and the denominator 502 measured after the onset of failure is approximately 70°. The apparent impedance calculation 555 is R F For a system having = 0Ω, this term ((I BM -I CM +I BN -I CN ) / (I BM -I CM This shows that despite a significant phase angle difference, it does not cause any reactance shift in the calculated apparent impedance. Therefore, the apparent impedance calculated in Apparent Impedance Calculation 555 is equal to the actual fault impedance.

[0028] In a heterogeneous system, the phase angle difference between the numerator 501 and the denominator 502 measured after the onset of failure is approximately 79°. The apparent impedance calculation 556 is R F In a system with =20Ω, the term ((I BM -I CM +I BN -I CN ) / (I BM -I CM This shows that )) causes a shift in both the real and imaginary components of the apparent impedance. As a result, the apparent impedance is not stable at a point within the boundary 512 of Zone 1. In other words, it is determined that no fault has occurred within the distance covered by the two terminals of BUS M162 and BUS N161.

[0029] As is evident from the above example, the performance of apparent impedance calculated according to the first method deteriorates when applied to non-homogeneous transmission line systems, especially systems including asynchronous generators. In particular, in the case of phase-phase-ground faults, the phase angle difference between the local current and the remote current and the fault obstacle resistance The combined effect of these factors significantly overreachs the calculated apparent impedance reactance, causing the impedance trajectory to settle at a point outside the boundary of Zone 1. As a result, it is determined that no fault has occurred within the distance covered by the two terminals.

[0030] Therefore, there is a need to improve the calculation method used to calculate the apparent impedance of a transmission line in the case of a phase-phase-ground fault for distance protection implemented in heterogeneous transmission systems with synchronous generators and / or DERs, particularly asynchronous generators. As described above, conventional methods calculate the apparent impedance, but their reactance portion is significantly overreaching, to the point that the impedance trajectory falls into the fourth quadrant of the quadrilateral characteristic. Such problems are favorably solved by the present disclosure by including a zero-sequence component in the calculation of the apparent impedance. In particular, in the case of IBR connecting lines, the zero-sequence current is supplied by the transformer and is therefore not limited by the converter control system. Furthermore, the magnitude of the zero-sequence current is greater than the positive-sequence current in these systems.

[0031] This disclosure relates to a method for distance of a transmission line carrying multiple phases, the method comprising: obtaining a first impedance of a first electrical loop formed by a first phase carried by the transmission line and the ground potential based on a zero-sequence current; obtaining a second impedance of a second electrical loop formed by a second phase carried by the transmission line and the ground potential based on a zero-sequence current; calculating the apparent impedance of the transmission line as seen at a first terminal based on the first and second impedances; and performing distance protection based on the apparent impedance.

[0032] The disclosure also relates to a method for distance protection of a transmission line carrying multiple phases for a phase-phase-ground fault, wherein the first phase is distinct from the second phase, and the method includes: obtaining a first impedance of a first electrical loop formed by the first phase carried on the transmission line and the ground potential based on zero sequence current; obtaining a second impedance of a second electrical loop formed by the second phase carried on the transmission line and the ground potential based on zero sequence current; calculating the apparent impedance of the transmission line as seen at a first terminal based on the first and second impedances; and performing distance protection based on the apparent impedance.

[0033] Various embodiments can preferably implement the following features: According to one embodiment, the plurality of phases are a first phase, a second phase, and a third phase, or include them. The plurality of phases may include at least one further phase, for example, a fourth, fifth, sixth, and so on.

[0034] According to one embodiment, the first phase among the multiple phases is the first faulted phase of a phase-phase-ground fault.

[0035] According to one embodiment, the second phase among the multiple phases is the second fault phase of a phase-phase-ground fault.

[0036] According to one embodiment, the first impedance is the apparent impedance observed at the first terminal of the first phase. According to one embodiment, the first impedance is determined based on the voltage of the first phase and the current of the first phase measured at the first terminal. According to one embodiment, the first impedance is determined based on the currents of all the respective multiple phases, in particular the zero sequence calculated therefrom.

[0037] According to one embodiment, the second impedance is the apparent impedance observed at the first terminal of the second phase. According to one embodiment, the second impedance is determined based on the voltage of the second phase measured at the first terminal and the current of the first phase measured at the first terminal. According to one embodiment, the second impedance is determined based on the currents of all the respective multiple phases, in particular the zero sequence calculated therefrom.

[0038] According to one embodiment, calculating the apparent impedance of a transmission line involves or includes combining a first impedance and a second impedance, in particular by linear combination, more specifically by averaging them. According to one embodiment, the calculated apparent impedance of a transmission line is the apparent impedance seen at a first terminal, in particular, looking at the direction of the phase-phase-ground fault on the transmission line when a phase-phase-ground fault occurs. According to one embodiment, the calculated apparent impedance is calculated based on the current and voltage measured at the first terminal when a phase-phase-ground fault occurs. Thus, the calculated apparent impedance of a transmission line may be the equivalent impedance of the first and second phases in the transmission line where the fault in the phase-phase-ground phase occurs. The voltage measured at the first terminal that serves as the basis for calculating the apparent impedance is the voltage of the first and second phases measured at the first terminal. The current measured at the first terminal that serves as the basis for calculating the apparent impedance is the current of all each of the multiple phases, in particular the zero sequence calculated therefrom.

[0039] According to one embodiment, the method includes calculating a first impedance of a first electrical loop formed by a first phase and ground potential carried in a transmission line based on a zero-sequence current, and calculating a second impedance of a second electrical loop formed by a second phase and ground potential carried in a transmission line based on a zero-sequence current. In other words, according to one embodiment, the first impedance and / or second impedance are calculated instead of obtaining the first impedance and / or second impedance, or in addition to obtaining them.

[0040] According to one embodiment, the apparent impedance of a power transmission line includes zero-sequence currents.

[0041] According to one embodiment, performing distance protection includes controlling a distance protection relay.

[0042] According to one embodiment, the method includes identifying a phase-phase-ground fault point based on the calculated apparent impedance.

[0043] According to one embodiment, the method includes determining whether the identified phase-phase-ground fault point lies within the distance between a first terminal and a second terminal.

[0044] According to one embodiment, calculating the apparent impedance includes calculating the average of a first impedance and a second impedance.

[0045] According to one embodiment, obtaining the first and second impedances, and / or calculating the apparent impedance of the transmission line relays, is performed by at least one of the relays, controllers, servers, or cloud.

[0046] According to one embodiment, the power transmission line is one of the following: a parallel line, a coaxial cable, a planar power transmission line, or a radial line.

[0047] According to one embodiment, the first terminal is coupled to the first generator and / or terminates the power line.

[0048] According to one embodiment, the power transmission line is further terminated by a second terminal, and / or a second generator is coupled to the second terminal.

[0049] According to one embodiment, the first generator and / or the second generator comprises a synchronous generator or an asynchronous generator, in particular a renewable power plant, more specifically an inverter-based resource IBR, and / or a synchronous generator or an asynchronous generator, in particular a renewable power plant, more specifically an inverter-based resource IBR. According to one embodiment, the zero-sequence current is the phasor sum of the phase currents.

[0050] According to one embodiment, the zero-sequence current is supplied by the generator's transformer and is therefore not limited by the converter control system in transmission lines, particularly IBR connecting lines.

[0051] According to one embodiment, the magnitude of the zero-sequence current is greater than the positive-sequence current.

[0052] According to one embodiment, any combination of phases can cause a phase-phase-ground fault.

[0053] The disclosure also relates to a device for protecting a transmission line carrying multiple phases, the device comprising a processor which is configured to obtain a first impedance of a first electrical loop formed by a first phase carried in the transmission line and the ground potential based on zero-sequence current, obtain a second impedance of a second electrical loop formed by a second phase carried in the transmission line and the ground potential based on zero-sequence current, calculate the apparent impedance of the transmission line as seen at a first terminal coupled to a first generator based on the first and second impedances, and perform distance protection based on the apparent impedance.

[0054] The disclosure further relates to a device for distance protection of a transmission line carrying multiple phases for a phase-phase-ground fault, wherein the first phase is distinct from the second phase, and the device comprises a processor which is configured to obtain a first impedance of a first electrical loop formed by the first phase carried in the transmission line and the ground potential based on zero-sequence current, obtain a second impedance of a second electrical loop formed by the second phase carried in the transmission line and the ground potential based on zero-sequence current, calculate the apparent impedance of the transmission line as seen at a first terminal coupled to a first generator based on the first and second impedances, and perform distance protection based on the apparent impedance.

[0055] According to one embodiment, the plurality of phases are a first phase, a second phase, and a third phase, or include them. The plurality of phases may include at least one further phase, for example, a fourth, fifth, sixth, and so on.

[0056] According to one embodiment, the first phase among the multiple phases is the first faulted phase of a phase-phase-ground fault.

[0057] According to one embodiment, the second phase among the multiple phases is the second fault phase of a phase-phase-ground fault.

[0058] According to one embodiment, the first impedance is the apparent impedance observed at the first terminal of the first phase. According to one embodiment, the first impedance is determined based on the voltage of the first phase and the current of the first phase measured at the first terminal. According to one embodiment, the first impedance is determined based on the currents of all the respective multiple phases, in particular the zero sequence calculated therefrom.

[0059] According to one embodiment, the second impedance is the apparent impedance observed at the first terminal of the second phase. According to one embodiment, the second impedance is determined based on the voltage of the second phase measured at the first terminal and the current of the first phase measured at the first terminal. According to one embodiment, the second impedance is determined based on the currents of all the respective multiple phases, in particular the zero sequence calculated therefrom.

[0060] According to one embodiment, the processor is configured to calculate the apparent impedance of a transmission line by coupling a first impedance and a second impedance, in particular by linear coupling, and more specifically by averaging them. According to one embodiment, the calculated apparent impedance of the transmission line is the apparent impedance seen at a first terminal, in particular, looking at the direction of the phase-phase-ground fault on the transmission line when a phase-phase-ground fault occurs. According to one embodiment, the calculated apparent impedance is calculated based on the current and voltage measured at the first terminal when the phase-phase-ground fault occurs. Thus, the calculated apparent impedance of the transmission line may be the equivalent impedance of the first and second phases where the fault in the phase-phase-ground phase of the transmission line occurs. The voltage measured at the first terminal that serves as the basis for calculating the apparent impedance is the voltage of the first and second phases measured at the first terminal. The current measured at the first terminal that serves as the basis for calculating the apparent impedance is the current of all each of the multiple phases, in particular the zero sequence calculated therefrom.

[0061] According to one embodiment, the apparent impedance of a power transmission line includes zero-sequence currents.

[0062] According to one embodiment, the processor is configured to perform distance protection by including control of distance protection relays.

[0063] According to one embodiment, the processor is configured to further perform the task of identifying phase-phase-ground fault points based on the calculated apparent impedance.

[0064] According to one embodiment, the processor is configured to further perform a determination of whether the identified phase-phase-ground fault point lies within the distance between a first terminal and a second terminal.

[0065] According to one embodiment, the processor is configured to calculate the apparent impedance by including calculating the average of a first impedance and a second impedance.

[0066] According to one embodiment, the processor is configured to use at least one of relays, controllers, servers, or clouds to obtain a first impedance and a second impedance, and / or calculate the apparent impedance of the power line relay.

[0067] According to one embodiment, the power transmission line is one of the following: a parallel line, a coaxial cable, a planar power transmission line, or a radial line.

[0068] According to one embodiment, the first terminal is coupled to the first generator and / or terminates the power line.

[0069] According to one embodiment, the power transmission line is further terminated by a second terminal, and / or a second generator is coupled to the second terminal.

[0070] According to one embodiment, the first generator and / or the second generator comprises a synchronous generator or an asynchronous generator, in particular a renewable power plant, more specifically an inverter-based resource IBR, and / or a synchronous generator or an asynchronous generator, in particular a renewable power plant, more specifically an inverter-based resource IBR.

[0071] According to one embodiment, the zero-sequence current is the phasor sum of the phase currents. According to one embodiment, the zero-sequence current is supplied by the generator's transformer and is therefore not limited by the converter control system in transmission lines, particularly IBR connecting lines.

[0072] According to one embodiment, the magnitude of the zero-sequence current is greater than the positive-sequence current.

[0073] According to one embodiment, any combination of phases can cause a phase-phase-ground fault.

[0074] The disclosure further relates to a system for distance protection of a transmission line carrying multiple phases, comprising a transmission line and a device according to any one of the device embodiments described above, wherein the device comprises a processor configured to perform any one of the method embodiments described above.

[0075] Various exemplary embodiments of this disclosure are intended to provide features that will be readily apparent by referring to the following description in conjunction with the accompanying drawings. Exemplary systems, methods, and devices are disclosed herein by various embodiments. However, it should be understood that these embodiments are presented as examples and not as limitations, and it will be apparent to those skilled in the art who have read this disclosure that various modifications to the disclosed embodiments can be made while remaining within the scope of this disclosure.

[0076] Therefore, this disclosure is not limited to the exemplary embodiments and uses described and illustrated herein. Furthermore, the particular order and / or hierarchy of things in the methods disclosed herein are merely illustrative techniques. Based on design preferences, the particular order or hierarchy of things in the disclosed methods or processes can be rearranged while remaining within the scope of this disclosure. Accordingly, those skilled in the art will understand that the methods and techniques disclosed herein present various steps or operations in a sample order, and that this disclosure is not limited to the specific order or hierarchy presented unless otherwise specified.

[0077] The following describes exemplary embodiments of this disclosure. Note that some aspects of any one of the embodiments described may also be found in several other embodiments unless otherwise specified or evident. However, for the sake of clarity, each aspect is described in detail only when first mentioned, and repeated descriptions of the same aspect are omitted.

[0078] The above and other aspects and embodiments thereof will be described in more detail in the drawings, description and claims. [Brief explanation of the drawing]

[0079] [Figure 1a] Figures 1a) and 1b) show schematic diagrams of a two-terminal power transmission line system connected to a generator according to one embodiment of the present disclosure. [Figure 1b] Figures 1a) and 1b) show schematic diagrams of a two-terminal power transmission line system connected to a generator according to one embodiment of the present disclosure. [Figure 2] Figure 2 is an equivalent circuit diagram of a phase B-phase C-installation (BC-g) fault in a power transmission line system according to one embodiment of the present disclosure. [Figure 3]Figure 3 shows the apparent impedance performance calculated according to the first method for homogeneous and heterogeneous systems shown in Figure 1a). [Figure 4] Figure 4 shows the apparent impedance performance calculated according to the first method for homogeneous and heterogeneous systems shown in Figures 1a) and 1b), respectively. [Figure 5] Figure 5 shows the apparent impedance performance calculated according to the first method in the heterogeneous system shown in Figure 1b). [Figure 6] Figure 6 shows a flowchart of a method according to one embodiment of the present disclosure. [Figure 7a] Figures 7a) and 7b) show the apparent impedance performance calculated according to the first and second methods in the heterogeneous system shown in Figure 1b). [Figure 7b] Figures 7a) and 7b) show the apparent impedance performance calculated according to the first and second methods in the heterogeneous system shown in Figure 1b). [Figure 8a] Figures 8a) and 8b) show the apparent impedance performance calculated according to the first and second methods in the heterogeneous system shown in Figure 1b). [Figure 8b] Figures 8a) and 8b) show the apparent impedance performance calculated according to the first and second methods in the heterogeneous system shown in Figure 1b). [Figure 9] Figure 9 shows the apparent impedance performance calculated according to the first and second methods in the heterogeneous system shown in Figure 1b). [Figure 10] Figure 10 shows the apparent impedance performance calculated according to the first and second methods in the heterogeneous system shown in Figure 1b). [Figure 11a] Figures 11a) and 11b) show the apparatus and the system comprising the apparatus and power transmission lines. [Figure 11b] Figures 11a) and 11b) show the apparatus and the system comprising the apparatus and power transmission lines. [Modes for carrying out the invention]

[0080] Figure 6 shows a flowchart of a method according to one embodiment of the present disclosure. According to one embodiment, the flowchart shown in Figure 6 is a method for distance protection of a transmission line carrying multiple phases, in particular a method for a phase-phase-ground fault, wherein the first phase is different from the second phase, and the first phase is different from the second phase. Step S601 is to obtain a first impedance of a first electrical loop formed by the first phase carried in the transmission line and the ground potential based on zero sequence current. Successively, step S602 is to obtain a second impedance of a second electrical loop formed by the second phase carried in the transmission line and the ground potential based on zero sequence current. Next, step S603 is to calculate the apparent impedance of the transmission line as seen at the first terminal based on the first and second impedances. Next, in step 604, distance protection is performed based on the apparent impedance.

[0081] Alternatively, the calculation of the apparent impedance observed at the first terminal can be interpreted as the calculation of the apparent impedance observed at any other equivalent, using an equivalent. It will be understood by those skilled in the art that the apparent impedance is defined as the ratio of voltage to current at the injection point, which is the first terminal in this disclosure.

[0082] According to one embodiment, the plurality of phases are a first phase, a second phase, and a third phase, or include them. The plurality of phases may include at least one further phase, for example, a fourth, fifth, sixth, and so on.

[0083] According to one embodiment, the apparent impedance of a power transmission line includes zero-sequence currents.

[0084] According to one embodiment, performing distance protection includes controlling a distance protection relay.

[0085] According to one embodiment, the method includes identifying a phase-phase-ground fault point based on apparent impedance.

[0086] According to one embodiment, the method includes determining whether the identified phase-phase-ground fault point lies within the distance between a first terminal and a second terminal.

[0087] According to one embodiment, calculating the apparent impedance includes calculating the average of a first impedance and a second impedance.

[0088] According to one embodiment, obtaining the first and second impedances, and / or calculating the apparent impedance of the transmission line relays, is performed by at least one of the relays, controllers, servers, or cloud.

[0089] According to one embodiment, the power transmission line is one of the following: a parallel line, a coaxial cable, a planar power transmission line, or a radial line.

[0090] According to one embodiment, the first terminal is coupled to the first generator and / or terminates the power line.

[0091] According to one embodiment, the power transmission line is further terminated by a second terminal, and / or a second generator is coupled to the second terminal.

[0092] According to one embodiment, the first generator and / or the second generator comprises a synchronous generator or an asynchronous generator, in particular a renewable power plant, more specifically an inverter-based resource IBR, and / or a synchronous generator or an asynchronous generator, in particular a renewable power plant, more specifically an inverter-based resource IBR. According to one embodiment, the zero-sequence current is the phasor sum of the phase currents.

[0093] According to one embodiment, the zero-sequence current is supplied by the generator's transformer and is therefore not limited by the converter control system in transmission lines, particularly IBR connecting lines.

[0094] According to one embodiment, the magnitude of the zero-sequence current is greater than the positive-sequence current.

[0095] According to one embodiment, any combination of phases can cause a phase-phase-ground fault.

[0096] According to one embodiment, the first voltage equation is obtained by applying Kirchhoff's voltage law (KVL) to the first phase-ground (phase B-ground) loop in Figure 2, as follows.

[0097]

number

[0098] Similarly, the second voltage equation can be obtained by applying Kirchhoff's voltage law (KVL) to the second phase-ground (phase C-ground) loop in Figure 2, as shown below.

[0099]

number

[0100] Here, I 0M ∫ represents the zero-sequence current at terminal M, K0 represents the compensation coefficient defined by (Z0-Z1) / Z1, and Z0 and Z1 represent the zero-sequence and positive-sequence line impedances, respectively.

[0101] The first impedance of the first phase-ground loop is obtained based on equation (5) as follows:

[0102]

number

[0103] Similarly, the second impedance of the second phase-ground loop is obtained based on equation (6) as follows:

[0104]

number

[0105] Adding the first impedance in equation (7) and the second impedance in equation (8) gives the following:

[0106]

number

[0107] Here,

[0108]

number

[0109]

number

[0110]

number

[0111]

number

[0112] The apparent impedance of a phase-phase-ground loop is calculated by dividing equation (9) by 2.

[0113]

number

[0114] Here, Z' = ((PS + QR) / 2QS). The phase angle of term Z' is minimal, and in particular, about 0.1°. The calculated apparent impedance Z in equation (8) BC-g In this context, the effect of the minimum phase angle of the term Z' that causes the smallest reactance shift will be explained below using the attached figure.

[0115] According to one embodiment, the first phase among the multiple phases (phase B in the above embodiment) is the first faulted phase of a phase-phase-ground fault (phase B-phase C-ground fault in the above embodiment).

[0116] According to one embodiment, the second phase among the multiple phases (phase C in the above embodiment) is the second faulted phase of a phase-phase-ground fault (phase B-phase C-ground fault in the above embodiment).

[0117] According to one embodiment, the first impedance (the impedance calculated according to equation (7) in the above embodiment) is the apparent impedance observed at the first terminal of the first phase (phase B in the above embodiment). According to one embodiment, the first impedance is determined based on the voltage of the first phase and the current of the first phase measured at the first terminal. According to one embodiment, the first impedance is determined based on the currents of all the respective multiple phases, in particular the zero sequence calculated therefrom.

[0118] According to one embodiment, the second impedance (in the above embodiment, the formula is ( 10 The impedance calculated according to ) is the apparent impedance observed at the first terminal of the second phase (phase C in the above embodiment). According to one embodiment, the second impedance is determined based on the voltage of the second phase measured at the first terminal and the current of the first phase measured at the first terminal. According to one embodiment, the second impedance is determined based on the currents of all each of the multiple phases, in particular the zero sequence calculated therefrom.

[0119] According to one embodiment, calculating the apparent impedance of a transmission line involves or includes combining a first impedance and a second impedance, in particular by linear combination, more specifically by averaging them (e.g., equation (10)). According to one embodiment, the calculated apparent impedance of a transmission line (the impedance calculated according to equation (10) in the above embodiment) is the apparent impedance seen at a first terminal, in particular, looking at the direction of the phase-phase-ground fault on the transmission line when a phase-phase-ground fault occurs. According to one embodiment, the calculated apparent impedance is calculated based on the current and voltage measured at the first terminal when the phase-phase-ground fault occurs. Thus, the calculated apparent impedance of a transmission line may be the equivalent impedance of the first and second phases in the transmission line where the fault in the phase-phase-ground phase occurs. The voltage measured at the first terminal that serves as the basis for calculating the apparent impedance is the voltage of the first and second phases measured at the first terminal. The current measured at the first terminal, which serves as the basis for calculating the apparent impedance, is the current of each of the multiple phases, and in particular the zero sequence calculated from it.

[0120] Here, calculating the apparent impedance according to equation (10) is called the second method for calculating the apparent impedance. Therefore, the second apparent impedance refers to the apparent impedance calculated according to the second method.

[0121] Figures 7a) and 7b) show the values ​​for 0 ohms, 10 ohms, and 20 ohms. obstacle resistance The apparent impedance performance calculated according to the first and second methods in the heterogeneous system presented in Figure 1b) is shown, taking this into consideration.

[0122] The table shown in Figure 7a) shows the values ​​for 0 ohms, 10 ohms, and 20 ohms. obstacle resistanceThis summarizes the calculated first apparent impedance 711, calculated by the first method, and the calculated second apparent impedance 712, calculated by the second method, for the heterogeneous system shown in Figure 1b), taking these factors into consideration.

[0123] Figure 7b) shows trajectory plots 710, 720, and 730 illustrating the simulation results of the trajectories for the first apparent impedance 711 and the second apparent impedance 712, as well as the Zone 1 impedance boundary 713. The y-axis of trajectory plots 710, 720, and 730 represents virtual values, and the x-axis represents real values. The calculated apparent impedances are summarized in Figure 7a), representing the settling apparent impedance that each trajectory of the first apparent impedance 711 and the second apparent impedance 712 ultimately reaches. A 60% phase-phase-ground fault is assumed, resulting in the actual fault apparent impedance Z true = 2.14 + 30.46j, where j represents an imaginary number. Alternatively, i represents an imaginary number as shown in the table in Figure 7a).

[0124] The first orbital plot 710 is R F The first apparent impedance trajectory 711 and the second apparent impedance trajectory 712 are shown considering =0Ω, and the second trajectory plot 720 is R F The first apparent impedance trajectory 711 and the second apparent impedance trajectory 712 are shown, taking into account =10Ω. As is evident from the first two trajectory plots 710 and 720, the first apparent impedance 711 and the second apparent impedance 712 stabilize at a point within the boundary 713 of zone 1, thereby accurately identifying faults within the distance covered by the two terminals BUS M162 and BUS N161.

[0125] The third orbital plot 730 is R FThe first apparent impedance trajectory 711 and the second apparent impedance trajectory 712 are shown, considering a impedance of 20Ω. The first apparent impedance 711 cannot stabilize at a point within the boundary 713 of Zone 1, resulting in a false fault determination. In contrast, the second apparent impedance 712 stabilizes at a point within the boundary 713 of Zone 1, thereby accurately identifying faults within the distance covered by the two terminals BUS M162 and BUS N161.

[0126] Figures 8a) and 8b) show the apparent impedance performance calculated according to the first and second methods in the heterogeneous system presented in Figure 1b), considering various pre-fault load currents.

[0127] The table shown in Figure 8a) shows the pre-fault load currents (I) for 50A, 370A, 750A, and 1500A. PF This summarizes the calculated first apparent impedance 811 and second apparent impedance 812 of the heterogeneous system presented in Figure 1b), taking into account the above.

[0128] Figure 8b) shows orbital plots 810, 820, 830, and 840 illustrating the simulation results of the trajectories for the first apparent impedance 811 and the second apparent impedance 812, as well as the Zone 1 impedance boundary 813. The y-axis of orbital plots 810, 820, 830, and 840 represents virtual values, and the x-axis represents real values. The calculated first and second apparent impedances summarized in Figure 8a) represent the settling apparent impedances that each trajectory for the first apparent impedance 811 and the second apparent impedance 812 ultimately reaches. F A phase-phase-ground fault is assumed in 50% of the lines where the impedance is 20Ω, and as a result, the apparent impedance of the fault is Z true = 1.78 + 25.39j, where j represents an imaginary number. Alternatively, i represents an imaginary number, as shown in the table in Figure 8a).

[0129] The first orbital plot 810 is IPF The first apparent impedance trajectory 811 and the second apparent impedance trajectory 812 considering =50A are shown, and the second trajectory plot 820 is I PF The first apparent impedance trajectory 811 and the second apparent impedance trajectory 812 considering =370A are shown, and the third trajectory plot 830 is I PF The first apparent impedance trajectory 811 and the second apparent impedance trajectory 812 are shown considering =750A. As is evident from the first three trajectory plots 810, 820, and 830, the trajectory of the first apparent impedance 811 fails to stabilize at a point within the boundary 813 of zone 1, resulting in a false fault determination. In contrast, the second apparent impedance 812 reaches a point within the boundary 813 of zone 1, thereby accurately identifying a fault within the distance covered by the two terminals BUS M162 and BUS N161.

[0130] The fourth orbital plot 840 is I PF The apparent impedance trajectories considering =1500A are shown. The trajectories of the first apparent impedance 811 and the second apparent impedance 812 stabilize at a point within the boundary 813 of zone 1, thereby accurately identifying faults within the distance covered by the two terminals BUS M162 and BUS N161.

[0131] Figure 9 shows R F = 0Ω and R F The apparent impedance performance calculated according to the first and second methods is shown for the heterogeneous system presented in Figure 1b), considering the radial lines of a transmission line having an impedance of 20Ω.

[0132] Figure 9 shows orbital plots 910 and 920 illustrating the simulation results of the orbits for the first apparent impedance 911 and the second apparent impedance 912, as well as the Zone 1 impedance boundary 913. The y-axis of orbital plots 910 and 920 represents virtual values, and the x-axis represents real values. F = 0Ω and R FA phase-phase-ground fault is assumed in 50% of the radial line, where the impedance is 20Ω. As is evident from trajectory plots 910 and 920, the trajectories of the first apparent impedance 911 and the second apparent impedance 912 stabilize at a point within the boundary 913 of zone 1, thereby accurately identifying the fault within the distance covered by the two terminals BUS M162 and BUS N161.

[0133] Figure 10 shows the apparent impedance performance calculated according to the first and second methods for the heterogeneous system presented in Figure 1b), considering various power-to-line impedance ratios (SIRs): SIR=0.3, SIR=1, and SIR=2.

[0134] Figure 10 shows orbital plots 1010, 1020, and 1030 illustrating the simulation results of the orbits for the first apparent impedance 1001, the second apparent impedance 1002, and the zone 1 impedance boundary 1003. The y-axis of orbital plots 1010, 1020, and 1030 represents virtual values, and the x-axis represents real values. F A phase-phase-ground fault is assumed in 50% of the radial lines, which have an impedance of 20Ω.

[0135] The first trajectory plot 1010 shows the apparent impedance trajectory at remote terminal 161 with SIR=0.3. As is evident from the first trajectory plot 1010, the trajectory of the first apparent impedance 1001 fails to reach the boundary 1003 of zone 1, resulting in a false fault determination. In contrast, the trajectory of the second apparent impedance 1002 reaches the point within the boundary 1003 of zone 1, thereby accurately identifying a fault within the distance covered by the two terminals BUS M162 and BUS N161.

[0136] The second trajectory plot 1020 and the third trajectory plot 1030, considering SIR=1 and SIR=2 respectively, show that the trajectories of the first apparent impedance 1001 and the second apparent impedance 1002 reach their respective points within the boundary 1003 of Zone 1. As a result, the fault location is correctly identified as being within the distance covered by the two terminals of BUS M162 and BUS N161.

[0137] Figures 11a) and b) show the apparatus 1110 and the system 1100 comprising the apparatus 1110 and a power transmission line 1120. The power transmission line 1120 may be any of the exemplary power transmission lines shown in Figure 1. The apparatus 1110 includes a processor configured to perform the process illustrated in Figure 6.

[0138] According to one embodiment, the device 1110 is for distance protection of a transmission line carrying multiple phases. According to one embodiment, the device 1110 is for distance protection of a transmission line carrying multiple phases against a phase-phase-ground fault, wherein the first phase and the second phase of the multiple phases are included as fault phases in a phase-phase-ground fault, and the first phase is different from the second phase.

[0139] According to one embodiment, the plurality of phases are a first phase, a second phase, and a third phase, or include them. The plurality of phases may include at least one further phase, for example, a fourth, fifth, sixth, and so on.

[0140] According to one embodiment, the first phase among the multiple phases is the first faulted phase of a phase-phase-ground fault.

[0141] According to one embodiment, the second phase among the multiple phases is the second fault phase of a phase-phase-ground fault.

[0142] According to one embodiment, the first impedance is the apparent impedance observed at the first terminal of the first phase. According to one embodiment, the first impedance is determined based on the voltage of the first phase and the current of the first phase measured at the first terminal. According to one embodiment, the first impedance is determined based on the currents of all the respective multiple phases, in particular the zero sequence calculated therefrom.

[0143] According to one embodiment, the second impedance is the apparent impedance observed at the first terminal of the second phase. According to one embodiment, the second impedance is determined based on the voltage of the second phase measured at the first terminal and the current of the first phase measured at the first terminal. According to one embodiment, the second impedance is determined based on the currents of all the respective multiple phases, in particular the zero sequence calculated therefrom.

[0144] According to one embodiment, the processor is configured to calculate the apparent impedance of a transmission line by coupling a first impedance and a second impedance, in particular by linear coupling, and more specifically by averaging them. According to one embodiment, the calculated apparent impedance of the transmission line is the apparent impedance seen at a first terminal, in particular, looking at the direction of the phase-phase-ground fault on the transmission line when a phase-phase-ground fault occurs. According to one embodiment, the calculated apparent impedance is calculated based on the current and voltage measured at the first terminal when the phase-phase-ground fault occurs. Thus, the calculated apparent impedance of the transmission line may be the equivalent impedance of the first and second phases where the fault in the phase-phase-ground phase of the transmission line occurs. The voltage measured at the first terminal that serves as the basis for calculating the apparent impedance is the voltage of the first and second phases measured at the first terminal. The current measured at the first terminal that serves as the basis for calculating the apparent impedance is the current of all each of the multiple phases, in particular the zero sequence calculated therefrom.

[0145] According to one embodiment, the apparent impedance of a power transmission line includes zero-sequence currents.

[0146] According to one embodiment, the processor is configured to perform distance protection by including control of distance protection relays.

[0147] According to one embodiment, the processor is configured to further perform the task of identifying phase-phase-ground fault points based on the calculated apparent impedance.

[0148] According to one embodiment, the processor is configured to further perform a determination of whether the identified phase-phase-ground fault point lies within the distance between a first terminal and a second terminal.

[0149] According to one embodiment, the processor is configured to calculate the apparent impedance by including calculating the average of a first impedance and a second impedance.

[0150] According to one embodiment, the processor is configured to use at least one of relays, controllers, servers, or clouds to obtain a first impedance and a second impedance, and / or calculate the apparent impedance of the power line relay.

[0151] According to one embodiment, the power transmission line is one of the following: a parallel line, a coaxial cable, a planar power transmission line, or a radial line.

[0152] According to one embodiment, the first terminal is coupled to the first generator and / or terminates the power line.

[0153] According to one embodiment, the power transmission line is further terminated by a second terminal, and / or a second generator is coupled to the second terminal.

[0154] According to one embodiment, the first generator and / or the second generator comprises a synchronous generator or an asynchronous generator, in particular a renewable power plant, more specifically an inverter-based resource IBR, and / or a synchronous generator or an asynchronous generator, in particular a renewable power plant, more specifically an inverter-based resource IBR.

[0155] According to one embodiment, the zero-sequence current is the phasor sum of the phase currents. According to one embodiment, the zero-sequence current is supplied by the generator's transformer and is therefore not limited by the converter control system in transmission lines, particularly IBR connecting lines.

[0156] According to one embodiment, the magnitude of the zero-sequence current is greater than the positive-sequence current.

[0157] According to one embodiment, any combination of phases can cause a phase-phase-ground fault.

[0158] The disclosure further relates to a system for distance protection of a transmission line carrying multiple phases, comprising a transmission line and a device according to any one of the device embodiments described above, wherein the device comprises a processor configured to perform any one of the method embodiments described above.

[0159] While various embodiments of this disclosure have been described above, it should be understood that they are presented only as examples and not as limitations. Similarly, various figures may illustrate exemplary architectures or configurations provided to enable those skilled in the art to understand the exemplary features and functions of this disclosure. However, such those skilled in the art will understand that this disclosure is not limited to the illustrated exemplary architectures or configurations and can be implemented using various alternative architectures and configurations. Furthermore, as will be understood by those skilled in the art, one or more features of one embodiment can be combined with one or more features of another embodiment described herein. Therefore, the breadth and scope of this disclosure should not be limited by any of the exemplary embodiments described above.

[0160] Furthermore, it should be understood that any reference to elements in this specification using designations such as “first,” “second,” etc., does not generally limit the quantity or order of those elements. Rather, these names can be used in this specification as a convenient means of distinguishing two or more elements or examples of elements. Thus, references to first and second elements do not mean that only two elements can be used, or that the first element must in some way precede the second element.

[0161] Furthermore, those skilled in the art will understand that information and signals can be represented using any of the various different techniques and methods. For example, data, instructions, commands, information, signals, bits, and symbols that can be mentioned throughout the above description can be represented by voltage, electric current, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0162] Those skilled in the art will further understand that any of the various exemplary logic blocks, units, processors, means, circuits, methods, and functions described in relation to the embodiments disclosed herein can be implemented by electronic hardware (e.g., digital implementations, analog implementations, or a combination of both), firmware, various forms of programs or design code incorporating instructions (which may be referred to herein as “software” or “software units” for convenience), or any combination of these technologies.

[0163] To clearly demonstrate this compatibility with hardware, firmware, and software, various exemplary components, blocks, units, circuits, and processes are generally described above with respect to their functions. Whether such functions are implemented as hardware, firmware, software, or a combination of these technologies depends on the specific application and the design constraints imposed on the overall system. A person skilled in the art may implement the described functions in various ways for each specific application, but such implementation decisions should not be construed as departing from the scope of this disclosure. According to various embodiments, processors, devices, components, circuits, structures, machines, units, etc., can be configured to perform one or more of the functions described herein. The terms “configured for” or “configured to” as used herein with respect to a specified operation or function refer to processors, devices, components, circuits, structures, machines, units, etc., that are physically constructed, programmed and / or positioned to perform the specified operation or function.

[0164] Furthermore, those skilled in the art will understand that the various exemplary methods, logic blocks, units, devices, components, and circuits described herein can be implemented in, or performed by, an integrated circuit (IC) which may include a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic device, or any combination thereof. The logic blocks, units, and circuits may further include antennas and / or transceivers for communicating with various components within a network or device. While a general-purpose processor may be a microprocessor, in alternative examples, the processor may be any conventional processor, controller, or state machine. The processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors working with a DSP core, or any other suitable configuration for performing the functions described herein. When implemented in software, the functions may be stored as one or more instructions or codes on a computer-readable medium. Thus, the steps of the methods or algorithms disclosed herein may be performed as software stored on a computer-readable medium.

[0165] Computer-readable media include both computer storage media and communication media, which include any media that can enable the transfer of computer programs or code from one location to another. Storage media can be any available media that can be accessed by a computer. Such computer-readable media, but not limited to, include RAM, ROM, EEPROM, CD-ROM or other optical disk storage devices, magnetic disk storage devices or other magnetic storage devices, or any other media that can be used to store desired program code in the form of instructions or data structures and can be accessed by a computer.

[0166] Furthermore, embodiments of this disclosure may utilize memory or other storage devices, as well as communication components. For clarity, it will be understood that the above description has illustrated embodiments of this disclosure with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units, processing logic elements, or domains can be used without prejudice to this disclosure. For example, a function shown to be performed by a separate processing logic element or controller may be performed by the same processing logic element or controller. Thus, references to specific functional units are not intended to indicate a strict logical or physical structure or organization, but merely to refer to suitable means for providing the described functionality.

[0167] Various modifications to the embodiments described herein will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the embodiments shown herein, but should be given the broadest scope consistent with the novel features and principles disclosed herein, as set forth in the following claims.

Claims

1. A computer-based method for controlling distance protection relays in a transmission line that carries a plurality of phases in a phase-phase-ground fault, wherein the first phase is different from the second phase, and the method is: The first impedance of the first electrical loop formed by the first phase and ground potential carried by the power transmission line is obtained based on the zero-sequence current, The second impedance of the second electrical loop formed by the second phase carried by the power transmission line and the ground potential is obtained based on the zero sequence current, The apparent impedance of the transmission line observed at the first terminal is calculated based on the first impedance and the second impedance, Identifying the phase-phase-ground fault point based on the calculated apparent impedance, A method comprising controlling the distance protection relay based on the identified phase-phase-ground fault point.

2. The method according to claim 1, further comprising determining whether the identified phase-phase-ground fault point lies within a distance between the first terminal and a second terminal terminating the transmission line.

3. The method according to claim 1, wherein calculating the apparent impedance includes calculating the average of the first impedance and the second impedance.

4. The method according to claim 1, wherein the transmission line is one of a parallel line, a coaxial cable, a planar transmission line, or a radial line.

5. The method according to claim 1, wherein the first terminal is coupled to a first generator and / or terminates the power transmission line.

6. The method according to claim 5, wherein the transmission line is further terminated by a second terminal, and / or a second generator is coupled to the second terminal.

7. The method according to claim 6, wherein the first generator and / or the second generator is a synchronous generator or an asynchronous generator.

8. A device comprising a computer for controlling distance protection relays of a transmission line that carries a plurality of phases in a phase-phase-ground fault, wherein the first phase is different from the second phase, and the computer controls the first phase from the second phase. The first impedance of the first electrical loop formed by the first phase and ground potential carried by the power transmission line is obtained based on the zero-sequence current. The second impedance of the second electrical loop formed by the second phase carried by the power transmission line and the ground potential is obtained based on the zero sequence current. The apparent impedance of the transmission line observed at the first terminal connected to the first generator is calculated based on the first impedance and the second impedance. Based on the calculated apparent impedance, the phase-phase-ground fault point is identified. A device configured to control the distance protection relay based on the identified phase-phase-ground fault point.

9. A computer program for controlling a distance protection relay on a power line, which, when executed by a computer, performs the method according to claim 1.

10. A system for controlling distance protection relays for a power transmission line that carries multiple phases, comprising a power transmission line and the device described in claim 8.

11. The method according to claim 6, wherein the first generator or the second generator is a renewable energy power plant or an inverter-based resource (IBR).

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