Method for line differential protection on power transmission lines, computer readable medium

Abstract

The present disclosure relates to a method for line differential protection on a power transmission line. The method comprises obtaining voltage measurements and current measurements from a local end and a remote end of the power transmission line; obtaining voltage phasors and current phasors of the local end and the remote end using the voltage measurements and the current measurements; determining a synchronization angle δ based on the obtained voltage phasors and current phasors, wherein the synchronization angle δ is determined based on a load correction constant µ; and performing line differential protection on the power transmission line by synchronizing the unsynchronized voltage phasors and current phasors based on the synchronization angle δ.

Description

Technical Field

[0001] This disclosure relates to a method and a computer-readable medium for line differential protection on power transmission lines. Background Technology

[0002] With numerous advancements in technology and communication, time-synchronized IEDs are playing a major role in power systems. In particular, protection and monitoring algorithms for transmission lines require that voltage and current measurements from line terminals be time-synchronized (see...). Figure 1 (As described below). This is a critical requirement, and loss of synchronization can lead to erroneous outputs from algorithms such as line parameter estimation, fault location, differential protection, and model-based protection. Loss of time synchronization is often caused by problems in the associated hardware, software, and communication networks (distributed synchronization signals). Typically, time synchronization data in a substation system can contain information about the quality of time synchronization. Notably, when poor time synchronization quality is detected, critical protection functions (such as line differential protection) are blocked until the source of the error is detected and repaired. While blocking avoids possible false / erroneous relay actions, any faults during the blocking period remain undetected. Therefore, a method is needed to synchronize (dissynchronized) data that would allow protection and monitoring applications to run seamlessly without any modifications.

[0003] The problem of estimating data synchronization errors has been explored in various ways in existing literature. Generally, the loss of time synchronization between two data streams (e.g., x(t) and y(t)) can be considered as a transmission delay in one of them. For example, if we assume that x(t) is properly synchronized (synchronized to a clock source), then the signal y(t) can be expressed as... ,in This is the appropriate synchronization form for the signal y(t). When the time-domain signal is transformed to the phasor domain, this can be achieved by using operators. To express the delayed phasor signal, i.e. The angle δ in the phasor domain corresponds to the time lag in the time domain. For example, when sampling at a rate of 1 kHz, a 50 Hz current signal generates 20 samples per fundamental cycle (i.e., 360°). This means that a lag of one sample (or a delay of 1 ms) is equivalent to a phase angle lag of 18° in the corresponding phasor. Therefore, in the remainder of this disclosure, the terms "synchronization error angle δ" or "synchronization operator" are used. "They should be used interchangeably."

[0004] In [1], the method for calculating the synchronization operator has been discussed. Various methods are given. One method is given using both local terminal voltage and current and remote terminal voltage and current, another method is given using two terminal voltages and one terminal current, and yet another method is given using two terminal currents and one terminal voltage. Although the first two methods use fewer measurements, all three methods given by the authors require line parameters as input. The authors in [2] have proposed a method using symmetrical components at both ends during a fault. However, this method requires solving a nonlinear set of equations, which is done using the Newton-Raphson technique. The convergence of the solution depends on the initial guess. To eliminate the need for such iterations, the authors in [3] have proposed a method based on a lumped model of the transmission line. In addition, a method based on a distributed model is given, but it is solved using the Newton-Raphson method, with the initial guess being considered by solving the lumped model. A method using a distributed model and considering a combination of symmetrical and superimposed components with respect to the fault type is given in [4]. All methods [2], [3], and [4] have two common aspects. First, they use measurements obtained during a fault, which may be useless for calculating the synchronization angle during normal conditions. Secondly, all methods require knowledge of the line parameters. [5] proposes a method using measurements of voltage and current at both ends during normal system conditions and based on a lumped model of the transmission line. To alleviate all the limitations of previous methods, the authors in [6] propose a closed-form solution based on an equivalent π model of a distributed (long) line. A key aspect of the methods in [5] and [6] is that they are formulated in a method without line parameters. However, in doing so, certain assumptions are made about the parameters, which introduce errors in the estimation of the synchronization angle. The method in [6] is the closest prior art to the invention disclosed herein. It will be shown later how highly the performance of the method depends on the line load due to the assumptions involved.

[0005] Therefore, it would be advantageous to implement a reliable, line parameter-free method for calculating synchronization angles for differential protection on power transmission lines. It would also be advantageous to have a reliable, line parameter-free method for accurately determining data synchronization errors between line terminals for line differential protection on power transmission lines.

[0006] The necessity of this invention stems from the limitations discussed in existing methods in the prior art. No reliable method for calculating data synchronization errors between line terminals has been found in the literature. The proposed invention describes a method that provides a reliable algorithm for calculating synchronization angles used for line differential protection on power transmission lines. Summary of the Invention

[0007] This disclosure corrects the above-mentioned problems and provides a solution for safely and efficiently determining the synchronization angle. In particular, a method for compensating for time synchronization errors is presented, which is helpful for protection and monitoring applications in transmission lines.

[0008] The invention is defined in the independent claims. The dependent claims describe preferred embodiments.

[0009] To better address one or more of the above problems, in a first aspect of the invention, a method for line differential protection on a power transmission line is presented. The method includes: obtaining voltage and current measurements from a local and a remote end of the power transmission line; obtaining voltage and current phasors at the local and remote ends using the voltage and current measurements; determining a synchronization angle δ based on the obtained voltage and current phasors, wherein the synchronization angle δ is determined based on a load correction constant µ; and performing line differential protection on the power transmission line by synchronizing the asynchronous current phasors based on the synchronization angle δ.

[0010] Various embodiments may preferably implement the following features.

[0011] Preferably, the load correction constant µ is independent of line load during different voltage and current measurements.

[0012] Preferably, the synchronization angle δ is determined based on the line operating parameters at the local and remote ends.

[0013] Preferably, the load correction constant µ is determined based on the load angle θ of the transmission line during synchronous voltage and current measurements.

[0014] Preferably, the load correction constant µ is determined by subtraction of the line operating parameters at the local and remote ends.

[0015] Preferably, the load angle θ is determined based on the line operating parameters at the local and remote ends.

[0016] Preferably, the line operating parameters are determined based on the voltage and current phasors at the local and remote ends.

[0017] Preferably, the line operating parameters are determined based on voltage and current measurements obtained from both the local and remote ends.

[0018] In a second aspect, this disclosure relates to a computer-readable medium including instructions that, when executed by a processor, configure the processor to: obtain voltage and current measurements from a local and a remote end of a power transmission line; obtain voltage and current phasors at the local and remote ends using the voltage and current measurements; determine a synchronization angle δ based on the obtained voltage and current phasors, wherein the synchronization angle δ is determined based on a load correction constant µ; and perform line differential protection on the power transmission line by synchronizing the asynchronous current phasors based on the synchronization angle. Attached Figure Description

[0019] This disclosure will be further described with reference to the accompanying drawings, in which the same reference numerals denote the same or similar elements.

[0020] Figure 1 Two terminal systems according to an embodiment are shown.

[0021] Figure 2 An equivalent π network of a two-terminal distributed line model according to an embodiment is shown.

[0022] Figure 3 A flowchart of an embodiment according to this disclosure is shown.

[0023] Figure 4 A flowchart of an embodiment according to this disclosure is shown.

[0024] Figure 5 A flowchart of an embodiment according to this disclosure is shown. Detailed Implementation

[0025] Figure 1 An exemplary two-terminal system is shown, which has a length of l mn The transmission lines connect buses M and N. Intelligent electronic devices (IEDs) are provided at or near each bus. The bus that forms a reference point at the IED is called the local bus, and the other bus is called the remote bus. IEDs can be communicatively connected. For example, IEDs can be synchronized via wired or wireless means. Wireless synchronization can be achieved, for example, through a Global Navigation Satellite System (GNSS) (such as the Global Positioning System (GPS)). IEDs can connect to (cloud) servers or storage media for data acquisition.

[0026] This disclosure relates to a method for synchronizing data on power transmission lines. For example... Figure 3The method shown includes: obtaining voltage and current measurements S1 from the local and remote ends of the power transmission line; obtaining voltage and current phasors S2 for the local and remote ends using the voltage and current measurements; and determining whether the voltage and current measurements S3 have lost synchronization and determining a synchronization angle δ based on the determination of whether the voltage and current measurements have lost synchronization. Further, the method includes: synchronizing the voltage and current measurements S4 using the synchronization angle δ.

[0027] In an embodiment, if it is determined that the voltage measurement and the current measurement have lost synchronization, then a synchronization angle δ is determined.

[0028] In this embodiment, the synchronization angle δ is determined based on the load correction constant µ. In this embodiment, the load correction constant µ is independent of line load during asynchronous voltage and current measurements. Line load refers to the amount of power carried by the line. The synchronization angle δ can be determined based on line operating parameters at both the local and remote ends.

[0029] As used in this paper, the load correction constant can refer to a constant specific to the power line of interest. Its consideration in the derivation of the synchronization angle (the equation for the synchronization angle) makes the equation independent of the actual load on the line (the power flow on the line).

[0030] In this embodiment, the load correction constant µ is determined based on the load angle θ of the transmission line. The load angle can be the angle between voltage phasors at different points on the transmission line (e.g., local bus M and remote bus N). In particular, the load angle can be the angle between voltage phasors at different points on the transmission line (preferably between local bus M and remote bus N) under rated or low load conditions.

[0031] In this embodiment, the load correction constant µ is determined based on a subtraction operation of the line operating parameters at the local and remote ends during synchronized voltage and current measurements. In this embodiment, the load angle θ is determined based on the line operating parameters at the local and remote ends. In this embodiment, the line operating parameters are determined based on the voltage and current phasors at the local and remote ends.

[0032] This disclosure further relates to a corresponding apparatus for synchronizing data on a power transmission line, the apparatus being configured to perform the method described above. Specifically, the apparatus includes at least one processor configured to: obtain voltage and current measurements from a local and a remote end of the power transmission line; obtain voltage and current phasors at the local and remote ends using the voltage and current measurements; determine whether the voltage and current measurements have lost synchronization and determine a synchronization angle δ based on the determination of whether the voltage and current measurements have lost synchronization; and synchronize the voltage and current measurements using the synchronization angle δ.

[0033] In an embodiment, the processor is further configured to determine a synchronization angle δ if it is determined that the voltage measurement and the current measurement have lost synchronization.

[0034] In one embodiment, the processor is further configured to determine the synchronization angle δ based on a load correction constant µ. In this embodiment, the load correction constant µ is independent of line load during asynchronous voltage and current measurements. The processor may be further configured to determine the synchronization angle δ based on line operating parameters at both the local and remote ends.

[0035] In an embodiment, the processor is further configured to determine the load correction constant µ based on the load angle θ of the transmission line.

[0036] In one embodiment, the processor is further configured to determine a load correction constant µ based on a subtraction operation of line operating parameters at the local and remote ends during synchronized voltage and current measurements. In another embodiment, the processor is further configured to determine a load angle θ based on the line operating parameters at the local and remote ends. In yet another embodiment, the processor is further configured to determine line operating parameters based on voltage and current phasors at the local and remote ends.

[0037] The device can be an intelligent electronic device (IED).

[0038] This disclosure further relates to a computer-readable medium including instructions that, when executed by a processor, configure the processor to perform the methods described above.

[0039] The methods presented in this paper will be described in more detail below.

[0040] Line parameters, as used herein, can refer to the electrical parameters of a line, such as its resistance, inductance, and capacitance. The proposed method may not rely on prior information about these line parameters. That is, the method can be performed without prior information about the line parameters (i.e., without prior information about the line parameters). In other words, the method may be performed without prior settings for the line parameters (i.e., without prior settings for the line parameters or without relying on prior settings for the line parameters). Line operating parameters, as used herein, can be determined based on the voltage and current measured at the line's terminals. Line parameters relate to the parameters of power transmission lines.

[0041] refer to Figure 2 ,like Figure 1 The two-terminal system shown can be represented as follows: Figure 2 The equivalent π-network shown is illustrated. Wherein, , , , This indicates the voltage and current of the local and remote terminals in ascending order.

[0042] The distributed line parameter model equations can be given as follows: (1) (2) To determine the synchronization angle δ, the following equation can be considered.

[0043] eliminate , (3) in, (4) in (5) Where γ represents the positive-sequence propagation constant of the line. This represents the positive-sequence surge impedance of the line, and This indicates the length of the transmission line connecting buses M and N.

[0044] F1 and F2 according to equation (4) can be referred to as line operating parameters. That is, line operating parameters can depend on the voltage and current measurements at one terminal (e.g., a local terminal or a remote terminal) and an additional terminal parameter K (e.g., equation (5)). The terminal parameter K can depend on the voltage and current measured at both terminals. For example, the terminal parameter K can be the difference between the product of the voltage measured at the first terminal and the current measured at the second terminal and the product of the voltage measured at the second terminal and the current measured at the first terminal.

[0045] set up, (6) Where, µ( The imaginary part of (µ) is the load correction constant. The value of the load correction constant µ can be independent of the line load, and considering it can help derive an equation for the synchronization angle that is independent of the line load.

[0046] By substituting (3) into (6), the following formula can be determined.

[0047] (7) (8) From (7), we obtain the following equation (9).

[0048] (9) Using the synchronization operator obtained from equation (9) The synchronization angle can be determined. As shown below, the sample size can also be determined, and based on this sample size, the data is not synchronized.

[0049] (10) Where n is the number of samples per base period (e.g., 20 ms for a 50 Hz system).

[0050] function This represents a mathematical operation that provides the nearest integer to the real-valued input x. This means that the N-side measurements need to be adjusted forward. The sample is 1, and vice versa. In equation (10), the angle δ is measured in degrees. If δ is measured in radians, then 360 must be replaced by 2π.

[0051] In order to calculate the synchronization angle using equation (9), the load correction constant µ can be calculated first as follows.

[0052] Using equation (4), the following relationship can be derived: (11) consider (Usually under nominal conditions) The phase angle (for example, () is the total phase angle separation between two terminal voltages, i.e. Where θ is the line loading angle (or phasor if the data is synchronized). and (The angle between them). Under higher loads on the line, when it may not meet the requirements. In this case, the angle θ may represent not only the line load angle, but a more complex function of both the voltage phasor and the current phasor. In this disclosure, it is referred to as the line load or line loading angle.

[0053] The properties of complex numbers show that... (12) When the data is synchronized, that is ,but And therefore, under this condition, θ can be found to be: (13) Dividing (8) by (12) yields the following equation: (14) Considering the synchronized data and rearranging equation (14), we obtain (15) Therefore, the value of the load correction constant µ can be found using (15). The value µ found under a given load condition of the line can be used for any other load condition without needing to be estimated repeatedly. In this embodiment, µ is determined under synchronization conditions. The load correction constant µ helps to provide fast and efficient synchronization, regardless of the actual load conditions.

[0054] By solving equation (9), two sets of synchronization angles were obtained. The correct solution can be selected using the conditions outlined below.

[0055] By rearranging (3) and (2) as follows and using the two sets of synchronization angles obtained by solving equation (9), two sets of line parameters can be found: (16) (17) By using the line parameters obtained from (16) and (17), the following checks can be performed to select a valid solution set: (18) (19) If both solution sets satisfy (18) and (19), then the additional checks performed using (20) can be completed to obtain a valid solution set.

[0056] (20) Where R, X, and Y represent the line resistance, reactance, and admittance, respectively. These can be derived from γ and Z. c Derivation.

[0057] Figure 4This is another flowchart illustrating the method outlined above. In an embodiment, the method includes: obtaining voltage and current measurements from both the local and remote ends of the transmission line (i.e., at the IED / bus) and calculating the voltage and current phasors at both ends. Further, it is determined whether synchronization has been lost. Therefore, the SYNLOSS flag can be set.

[0058] If the measurements / phasors are synchronized (i.e., SYNLOSS = FALSE), F1 and F2 are determined using equation (4), θ is determined using equation (13), and the load correction constant µ (or load compensation constant) is determined using equation (15). As outlined above, the load correction constant µ can be determined under synchronization conditions. That is, µ can be determined when the voltage and / or current measurements (or their respective phasors) are synchronized. The load correction constant can then be reused regardless of the load or synchronization conditions.

[0059] If synchronization has been lost (SYNLOSS = TRUE), F1 and F2 are determined using equation (4), and the synchronization angle δ is determined by solving equation (9). A valid solution is selected using equations (18), (19), and (20). The data is synchronized using the obtained synchronization angle δ.

[0060] Using this synchronized data, various tasks can be performed, such as differential protection, model-based protection, fault location, or determination of line parameters.

[0061] Figure 5 This is a further flowchart according to embodiments of the present disclosure, which is fully compatible with the above description. In particular, Figure 5 The method shown utilizes the above disclosure for differential protection of power transmission lines. As outlined above, this method can also be used for model-based protection, fault location, or determination of line parameters.

[0062] Figure 5 The embodiment is for line differential protection on a power transmission line. The presented method includes: obtaining (T1) voltage and current measurements from the local and remote ends of the power transmission line; obtaining (T2) voltage and current phasors at the local and remote ends using the voltage and current measurements; determining (T3) a synchronization angle δ based on the obtained voltage and current phasors, wherein the synchronization angle δ is determined based on a load correction constant µ; and performing (T4) line differential protection on the power transmission line by synchronizing the asynchronous current phasors based on the synchronization angle δ.

[0063] The load correction constant µ is independent of line load during asynchronous voltage and current measurements. The synchronization angle δ can be determined based on line operating parameters at both the local and remote ends. Furthermore, the load correction constant µ can be determined based on the load angle θ of the transmission line during synchronized voltage and current measurements. The load correction constant µ can also be determined based on a subtraction operation between the local and remote line operating parameters.

[0064] The load angle θ can be determined based on line operating parameters at both the local and remote ends. For example, line operating parameters can be determined based on voltage and current phasors at both the local and remote ends. Furthermore, line operating parameters can be determined based on voltage and current measurements obtained from both the local and remote ends.

[0065] This disclosure also relates to a corresponding computer-readable medium including instructions that, when executed by a processor, configure the processor to: obtain voltage and current measurements from a local and a remote end of a power transmission line; obtain voltage and current phasors at the local and remote ends using the voltage and current measurements; determine a synchronization angle δ based on the obtained voltage and current phasors, wherein the synchronization angle δ is determined based on a load correction constant µ; and perform line differential protection on the power transmission line by synchronizing the asynchronous current phasors based on the synchronization angle.

[0066] The methods, apparatus, and computer-readable storage media described above provide a reliable solution for compensating for time synchronization errors. This solution is independent of line loading, is parameter-free, and makes no assumptions during formulation. The proposed method can be implemented in real-time IEDs because it is non-iterative and computationally simple. This invention is helpful for using all existing protection and monitoring algorithms without any modifications.

[0067] According to this disclosure, a reliable solution for calculating synchronization angles is provided. It is a parameter-free method and makes no related assumptions. Furthermore, existing protection and monitoring algorithms can be used without any modifications. The method performs reliably regardless of load and synchronization angle. The proposed method accurately estimates the data synchronization angle, and its performance is not affected by line load. The proposed method is not affected by prior information on a complete set of line parameters. It only requires a constant related to the line parameters. This constant can be estimated based on a previous set of synchronization measurements (under any random load conditions) or obtained from the line design parameters (if available). The proposed method constitutes a line load-independent approach. This is achieved by first estimating a line load-independent constant (as previously mentioned) and compensating for the line load factor in the closed-loop equation derived for the synchronization angle. The proposed algorithm is non-iterative and computationally simple to implement on a real-time IED CPU.

[0068] While various embodiments of this disclosure have been described above, it should be understood that they are presented by way of example only and not by way of limitation. Similarly, various figures may depict exemplary architectures or configurations, provided to enable those skilled in the art to understand the exemplary features and functionality of this disclosure. However, such persons will understand that this disclosure is not limited to the illustrated exemplary architectures or configurations, but can be implemented using various alternative architectures and configurations. Additionally, as those skilled in the art will understand, one or more features of one embodiment may be combined with one or more features of another embodiment described herein. Therefore, the breadth and scope of this disclosure should not be limited to any of the exemplary embodiments described above.

[0069] It should also be understood that any reference to elements in this document using names such as "first," "second," etc., generally does not restrict the number or order of those elements. Rather, these names may be used herein as a convenient means of distinguishing between two or more elements or instances of elements. Therefore, references to the first element and the second element do not imply that only two elements may be used, or that the first element must somehow precede the second element.

[0070] Additionally, those skilled in the art will understand that information and signals can be represented using any of a variety of different techniques and methods. For example, data, instructions, commands, information, signals, bits, and symbols, as referenced in the above description, can be represented by voltage, current, electromagnetic waves, magnetic fields or particles, light fields or particles, or any combination thereof.

[0071] Those skilled in the art will further understand that any of the various illustrated logic blocks, units, processors, devices, circuits, methods, and functions described in connection with the aspects disclosed herein can be implemented by electronic hardware (e.g., digital implementation, analog implementation, or a combination of both), firmware, various forms of program or design code in conjunction with instructions (which may be referred to herein as “software” or “software unit” for convenience), or any combination of these technologies.

[0072] To clearly illustrate this interchangeability of hardware, firmware, and software, various illustrative components, blocks, units, circuits, and steps have generally been described above in terms of their functionality. Whether such functionality is implemented as hardware, firmware, or software, or a combination of these technologies, depends on the specific application and design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in various ways for each specific application, but such implementation decisions will not depart from the scope of this disclosure. According to various embodiments, processors, devices, components, circuits, structures, machines, units, etc., may be configured to perform one or more of the functions described herein. As used herein with respect to a specified operation or function, the terms "configured to" or "configured for" refer to processors, devices, components, circuits, structures, machines, units, etc., physically constructed, programmed, and / or arranged to perform that specified operation or function.

[0073] Furthermore, those skilled in the art will understand that the various illustrative methods, logic blocks, units, devices, components, and circuits described herein can be implemented within or executed 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 devices, or any combination thereof. Logic blocks, units, and circuits may further include antennas and / or transceivers for communication with various components within a network or device. A general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other suitable configuration to perform the functions described herein. If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium. Therefore, the steps of the methods or algorithms disclosed herein can be implemented as software stored on a computer-readable medium.

[0074] Computer-readable media include both computer storage media and communication media. Communication media includes any media that can be enabled to transfer computer programs or code from one place to another. Storage media can be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage devices, magnetic disk storage devices or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer.

[0075] In this document, as used herein, the term "unit" refers to software, firmware, hardware, and any combination of these elements for performing the associated functions described herein. Additionally, for purposes of discussion, various units are described as discrete units; however, as will be apparent to those skilled in the art, two or more units may be combined to form a single unit that performs associated functions according to embodiments of this disclosure.

[0076] Additionally, memory or other storage devices and communication components may be employed in embodiments of this disclosure. It will be understood that, for clarity, embodiments of this disclosure have been described above with reference to various functional units and processors. However, it will be apparent that any suitable functional distribution may be used among different functional units, processing logic elements, or domains without departing from this disclosure. For example, a function illustrated to be performed by a separate processing logic element or controller may be performed by the same processing logic element or controller. Therefore, references to specific functional units are merely references to appropriate means for providing the described functionality and do not indicate a strict logical or physical structure or organization.

[0077] Various modifications to the embodiments described in this disclosure 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 is to be accorded the widest scope consistent with the novel features and principles disclosed herein, as set forth in the appended claims.

[0078] Citation List [1] M.M. Saha, J. Izykowski and E. Rosolowski, Grid Fault Location, London, UK: Springer, 2010.

[0079] [2] D. Novosel, DG Hart, E. Udren and J. Garitty, “Estimation of fault location at two asynchronous terminals”, IEEE Transactions on Power Transmission, Vol. 11, No. 1, pp. 130-138, January 1996, doi:10.1109 / 61.484009.

[0080] [3] J. Izykowski, R. Molag, E. Rosolowski and MM Saha, “Accurate location of transmission line faults using asynchronous measurements at both ends”, IEEE Transactions on Power Transmission, Vol. 21, No. 2, pp. 627-633, April 2006, doi: 10.1109 / TPWRD.2005.858778.

[0081] [4] J. Izykowski, E. Rosolowski, P. Balcerek, M. Fulczyk and MM Saha, “A precise non-iterative fault location algorithm using asynchronous measurements at both ends”, IEEE Transactions on Power Transmission, Vol. 25, No. 1, pp. 72-80, January 2010, doi: 10.1109 / TPWRD.2009.2035222.

[0082] [5] P. Dawidowski, J. I Ykowski and A. Nayir, “A non-iterative algorithm for simultaneous measurement analysis at both ends of transmission line parameters estimation and fault location,” 7th Conference on Electrical and Electronic Engineering (ELECO), Bursa, 2011, pp. I-76-I-79.

[0083] [6] K. Kalita, S. Anand and SK Parida, “Closed-loop solution for line fault location without parameters under asynchronous measurement”, IEEE Transactions on Power Transmission, Vol. 37, No. 3, pp. 1997-2006, June 2022, doi: 10.1109 / TPWRD.2021.3102181.

Claims

1. A method for line differential protection on power transmission lines, the method comprising: (T1) voltage and current measurements are obtained from the local and remote ends of the power transmission line; The voltage and current measurements are used to obtain (T2) the voltage phasors and current phasors of the local and remote terminals; The synchronization angle δ (T3) is determined based on the obtained voltage phasor and current phasor, wherein the synchronization angle δ is determined based on the load correction constant µ; as well as Line differential protection on the power transmission line (T4) is performed by synchronizing asynchronous current phasors based on the synchronization angle δ.

2. The method according to claim 1, wherein, The load correction constant µ is independent of line load during different voltage and current measurements.

3. The method according to claim 1 or 2, wherein, The synchronization angle δ is determined based on the line operating parameters of the local end and the remote end.

4. The method according to any one of claims 1 to 3, wherein, The load correction constant µ is determined based on the load angle θ of the transmission line during synchronized voltage and current measurements.

5. The method according to any one of claims 1 to 4, wherein, The load correction constant µ is determined by subtraction of the line operating parameters of the local end and the remote end.

6. The method according to claim 4 or 5, wherein, The load angle θ is determined based on the line operating parameters of the local end and the remote end.

7. The method according to any one of claims 3 to 6, wherein, The line operating parameters are determined based on the voltage and current phasors of the local and remote ends.

8. The method according to claim 7, wherein, The line operating parameters are determined based on voltage and current measurements obtained from the local end and the remote end.

9. A computer-readable medium including instructions that, when executed by a processor, configure the processor to: Voltage and current measurements are obtained from the local and remote ends of the power transmission line; The voltage and current measurements are used to obtain the voltage and current phasors at the local and remote ends. The synchronization angle δ is determined based on the obtained current phasors, where... The synchronization angle δ is determined based on the load correction constant µ; as well as Line differential protection on the power transmission line is performed by synchronizing asynchronous voltage and current phasors based on the synchronization angle.

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