Wave equation distance protection method and system

Abstract

The invention discloses a wave equation-based distance protection method and system. The method comprises the following steps of: establishing a lossless line single-ended solution calculation formula considering distribution parameters and transmission delay of a line for a power transmission line; applying the single-ended solution calculation formula to a line set protection range to obtain a line parameter calculation formula; establishing a wave equation for solving opposite-end electrical quantity through single-end electrical quantity; a power transmission line in a protection range is segmented, a wave equation is applied to each segment, finally, a voltage phasor at the tail end of the protection range is obtained, the voltage phasor is compared with a measured voltage phasor at a protection installation position, and distance protection of the power transmission line is carried out when distance protection action conditions are met. According to the method, the influence of distribution parameters and transmission time delay of the line is considered, the calculation precision is high, and under the conditions that the line is grounded through a transition resistor and the line is overloaded, the distance protection cannot generate maloperation, and the method can be expanded to various action conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of power transmission line protection, and relates to a distance protection method and system of a wave equation. Background Art

[0002] Distance protection is one of the basic relay protection configurations for high-voltage transmission lines. Existing distance protection generally uses the following wiring methods to achieve short-circuit impedance measurement:

[0003]

[0004] In the formula, They are the measured voltage and measured current at the protection installation. When a three-phase short circuit, a two-phase short circuit, or a two-phase ground short circuit occurs in the transmission line, Take the voltage difference of the fault phase, Take the current difference of the fault phase, taking the short circuit between phases AB as an example, take When a single-phase ground short circuit occurs in the transmission line, take A ground short circuit as an example. in, is the zero-sequence measurement current of the protection; K = (Z0-Z1) / (3Z1) is the zero-sequence compensation coefficient of the transmission line, Z1 and Z0 are the positive-sequence impedance and zero-sequence impedance of the line, both of which are known parameters. The wiring method of formula (1) can also measure the fault phase impedance of three-phase short circuit and two-phase ground short circuit. Based on the measurement of formula (1), compared with the action characteristics, the discrimination function of the distance protection measurement element is formed.

[0005] However, existing distance protection ignores the influence of wave transmission delay of transmission lines, and also ignores the distributed capacitance between phases and between phases and ground, which will increase the calculation error in the case of long transmission lines and cable lines. Summary of the invention

[0006] In order to solve the deficiencies in the prior art, the present invention provides a distance protection method and system of a wave equation.

[0007] The present invention adopts the following technical solution.

[0008] A first aspect of the present invention provides a distance protection method of a wave equation, comprising the following steps:

[0009] Step 1: Establish a lossless line single-ended solution calculation formula for the transmission line taking into account the distributed parameters and transmission delay of the line;

[0010] Step 2: Apply the single-ended solution calculation formula to the line setting protection range to obtain the line parameter calculation formula;

[0011] Step 3: Establish a wave equation for obtaining the opposite-end electrical quantity through the single-end electrical quantity according to the line parameter calculation formula;

[0012] Step 4: After the transmission line in the protection range is divided into sections, the wave equation is applied to each section to finally obtain the voltage phasor at the end of the protection range, which is compared with the measured voltage phasor at the protection installation location. If the distance protection action conditions are met, the distance protection of the transmission line is performed.

[0013] Preferably, the transmission line is a transmission line for transmitting industrial frequency components, a direct current transmission line, or a transmission line for transmitting other frequency components.

[0014] Preferably, step 1 specifically includes:

[0015] Step 11: For the transmission line MN, establish the basic equation of the lossless distributed parameter conductor when the line MN is fully connected;

[0016] Step 12, solving the basic equation to obtain the relationship between the electrical quantities at both ends of the line and the forward wave and reverse wave voltages;

[0017] Step 13: After comparing and merging the relationship between the electrical quantities at both ends of the line and the forward and reverse wave voltages, a single-ended solution formula for a lossless line is obtained by solving the formula in conjunction with the distributed parameters and transmission delay of the line.

[0018] Preferably, in step 11, the basic equation of the lossless distributed parameter conductor when the line MN is connected completely is:

[0019]

[0020] In the formula, x represents the position, i and u are the line current and voltage;

[0021] L0 and C0 are the inductance and capacitance per unit length of the line respectively.

[0022] Preferably, in step 12, M is the line head end, the position coordinate at the head end is x=0, and the voltage is u M ; N is the end of the line, the position coordinate of the end is x=l, and the voltage is u N , solving the basic equation, the relationship between the electrical quantities at both ends of the line and the forward and reverse wave voltages is as follows:

[0023] M-side N-terminal

[0024] In the formula, τ = l / v, which represents the transmission delay of electromagnetic waves along the entire length of the line;

[0025] l and v are the total length of the line and the transmission speed of electromagnetic waves respectively;

[0026] It represents wave impedance;

[0027] u M (t), i M (t) are the voltage and current at the M terminal at time t;

[0028] u N (t+τ), i N (t+τ) are the voltage and current at the N terminal at time t+τ respectively;

[0029] u N (t-τ), i N (t-τ) are the voltage and current at the N terminal at time t-τ respectively;

[0030] u f (t),u b (t) are the forward wave and reverse wave voltages at time t respectively.

[0031] Preferably, in step 13, compare equation (4) and equation (5), and according to u in the two equations f (t),u b (t) respectively correspond to the same conditions, and we get:

[0032]

[0033] will u M (t), i M (t) is an unknown variable, and u N (t+τ), i N (t+τ),u N (t-τ), i N (t-τ) is used as the available measurement signal, and equations (6) and (7) are solved together to obtain the lossless line single-ended solution calculation formula that uses the N-end electrical quantity to describe the M-end electrical quantity:

[0034]

[0035] According to the reciprocity property of the two ends of the line MN, the lossless line single-end solution expression for using the electrical quantity at the M end to obtain the electrical quantity at the N end is obtained:

[0036]

[0037] Preferably, the line parameter calculation formula obtained in step 2 is:

[0038]

[0039] Where h = K rel R / (4Z C ) is a constant determined by line parameters;

[0040] R is the resistance of the entire length of line MN; Z C is the wave impedance;

[0041] K rel =Z set / Z MN is the reliability coefficient, Z MN is the positive sequence impedance of the entire length of line MN, Z set Set the set impedance of the protection range MY for the line;

[0042] u Y (t) is the voltage at point Y at time t;

[0043] u M (tK rel τ),u M (t),u M (t+K rel τ) are (tK rel τ)、t、(t+K rel τ) The voltage at terminal M at the moment;

[0044] i M (tK rel τ),i M (t), i M (t+K rel τ) are (tK rel τ)、t、(t+K rel τ) The current at terminal M at the moment;

[0045] K rel τ is the transmission delay of electromagnetic waves within the protection range MY set by the line;

[0046] τ represents the transmission delay of electromagnetic waves along the entire length of line MN.

[0047] Preferably, in step 3, when the M terminal is used as the terminal with known electrical quantity and Y terminal is used as the opposite terminal of the voltage to be determined, the wave equation for determining the opposite terminal voltage through the single-terminal electrical quantity is established as follows:

[0048]

[0049] In the formula, E u =-Z C h(1-h 2 ), h=K rel R / (4Z C ) are all constant coefficients related to the line;

[0050] u M (tK relτ),u M (t),u M (t-2K rel τ) are (tK rel τ), t, (t-2K rel τ) The voltage at terminal M at the moment;

[0051] i M (tK rel τ),i M (t), i M (t-2K rel τ) are (tK rel τ), t, (t-2K rel τ) The current at terminal M at the moment;

[0052] K rel τ is the transmission delay of electromagnetic waves within the protection range MY set by the line;

[0053] u Y (tK rel τ) is the opposite end Y of M at (tK rel The voltage at time τ.

[0054] Preferably, in step 4, the distance protection action condition is: the voltage phasor at the end of the protection range is opposite in phase to the measured voltage phasor at the protection installation;

[0055] When the above conditions are met, the distance protection of the transmission line will be activated.

[0056] A second aspect of the present invention provides a wave equation distance protection system, the system comprising:

[0057] The wave equation derivation module is used to establish a lossless line single-end solution calculation formula for the transmission line taking into account the distributed parameters and transmission delay of the line; the single-end solution calculation formula is applied to the line setting protection range to obtain the line parameter calculation formula; according to the line parameter calculation formula, a wave equation is established to obtain the opposite end electrical quantity through the single-end electrical quantity;

[0058] The distance protection module is used to divide the transmission line in the protection range into sections and apply the wave equation to each section to finally obtain the voltage phasor at the end of the protection range, and compare it with the measured voltage phasor at the protection installation location. If the distance protection action conditions are met, the distance protection of the transmission line is performed.

[0059] A terminal comprises a processor and a storage medium; the storage medium is used to store instructions; the processor is used to operate according to the instructions to execute the steps of the method.

[0060] A computer-readable storage medium stores a computer program, which implements the steps of the method when executed by a processor.

[0061] Compared with the prior art, the beneficial effects of the present invention include at least:

[0062] The present invention takes into account the influence of the distributed capacitance and transmission delay of the line, and is a new technology for short-circuit distance measurement. At the same time, when the line is grounded through a transition resistor and the line is overloaded, the distance protection of the present invention will not malfunction.

[0063] The distance protection structured by the present invention can be applied to power transmission lines that transmit industrial frequency quantities; it can also be applied to DC lines, or power transmission lines that transmit other frequency components;

[0064] The present invention decomposes the line protection range MY into more small segments (such as greater than or equal to four segments), and each small segment applies the wave equation solution of the opposite end voltage, which effectively improves the calculation accuracy;

[0065] The present invention applies the single-ended solution of the wave equation to the distance protection of the transmission line. In the process, various methods such as phase voltage, polarization voltage, memory voltage, symmetrical component method, etc. can be used to achieve it, which can be expanded to various action conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a lossless single-conductor Berryron equivalent circuit;

[0067] Figure 2 It is a two-stage lossy single-conductor Berylon equivalent circuit;

[0068] Figure 3 It is a schematic diagram of the relationship between short circuit and phasor;

[0069] Figure 4 The figure is a flowchart of the method of the present invention. DETAILED DESCRIPTION

[0070] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0071] Embodiment 1 of the present invention provides a distance protection method of a wave equation, such as Figure 4 As shown, the method comprises the following steps:

[0072] Step 1: Based on the lossless distributed parameter model of the transmission line, a lossless line single-end solution calculation formula considering the distributed parameters and transmission delay of the line is obtained;

[0073] Further preferably, this step obtains a lossless line single-ended solution calculation formula taking into account the distributed parameters and transmission delay of the line through the Berylon equivalent circuit of the lossless single conductor and its calculation, specifically including:

[0074] Step 11, establish the basic equation of lossless distributed parameter conductor;

[0075] Figure 1 (a) shows a lossless distributed parameter model. The length of line MN is l. The model considers the influence of transmission delay l / v and distributed capacitance C. Assume that the inductance and capacitance per unit length of the line are L0 and C0 respectively; the positive direction of voltage and current is according to Figure 1 (a) is marked. So when the line MN is fully connected, we have:

[0076]

[0077] In the formula, x represents the position.

[0078] Equations (2) and (3) are called the basic equations of lossless distributed parameter conductors, and the corresponding equivalent circuits are as follows: Figure 1 As shown in (b), when dx→0, it is the accurate model of the circuit.

[0079] Step 12: Solve the basic equation to obtain the electrical quantities at both ends of the line and the forward wave voltage u f , reverse traveling wave voltage u b the relationship between;

[0080] If Figure 1 M is the beginning of the line, then the position coordinate of this point is x=0, and the voltage is expressed as u M ; N is the end of the line, the position coordinate is x = l, and the voltage is u N In this way, after solving equations (2) and (3), we can get the electrical quantities at both ends of the line and the forward wave voltage u f , reverse traveling wave voltage u b The relationship between them is as follows:

[0081] M-side

[0082] N-terminal

[0083] In the formula, τ = l / v, which represents the transmission time of the electromagnetic wave along the entire length of the line; Indicates wave impedance.

[0084] Step 13: Compare equations (4) and (5), and according to uf (t),u b (t) If the conditions are equal, we get:

[0085]

[0086] The above derivation process and the expressions of equations (6) and (7) are the basis for the application of the wave equation.

[0087] Based on equations (6) and (7), we can M (t), i M (t) is considered as an unknown variable, and u at different times of the N terminal is N 、i N Assuming that the measured signal can be obtained, then by solving equations (6) and (7) simultaneously, we can achieve: using the electrical quantity at the N end to describe the electrical quantity at the M end. The solution is:

[0088]

[0089] Formula (8) can be called the analytical expression of the basic solution of the lossless line (also called the single-ended solution). The right side of the equation is the electrical quantity of the N end, and τ=l / v is known.

[0090] Similarly, by solving equations (6) and (7) simultaneously, we can also obtain the single-end solution expression of the lossless line using the electrical quantity at the M end to calculate the electrical quantity at the N end:

[0091]

[0092] Equations (8) and (9) satisfy the reciprocity property at both ends of line MN, so only the measurement at end M is taken as an example below.

[0093] Step 2: Apply the single-ended solution calculation formula to the line setting protection range to obtain the line parameter calculation formula;

[0094] The derivation process of the line parameter calculation formula is: the lossless distributed parameter model is processed into a lossy single-conductor Berrylon equivalent circuit, and the line parameter calculation formula of the Berrylon equivalent circuit is obtained by combining the single-ended solution calculation formula. Furthermore, the Berrylon equivalent circuit of the lossy single-conductor and its calculation method are specifically as follows:

[0095] If the phase velocity is directly used Wave impedance If you do the calculation, the process will be quite complicated. The solution is:

[0096] 1) Ignore the small corona loss, usually take G0 = 0;

[0097] 2) Divide the lossless wire l into Q segments, each segment is l / Q long, and connect R / 4 resistors in series at both ends of each segment, where R is the resistance of the entire line and l is the entire length of the line, to obtain the Beryl equivalent circuit of the lossy single wire;

[0098] In this Berrylon equivalent circuit, the lossless conductor is divided into a lumped parameter circuit without time delay and a lossless line;

[0099] For lumped parameter circuits, Ohm's law is directly used to solve the line parameters;

[0100] For lossless lines, the single-ended solution shown in equation (9) can be used to derive the line parameter calculation formula.

[0101] The above Q can be any integer, but in order to facilitate the program's loop iteration, Q is usually taken as an even number. When Q is 2, such as Figure 2 As shown, the lossless wire is divided into two sections, each section is l / 2 in length, and an R / 4 resistor is connected in series at both ends of each section, where R is the resistance of the entire line and l is the entire length of the line. The Berylon equivalent circuit of the lossy single wire is obtained, in which the lossless wire is segmented by node M, R / 4 resistor, node 1, node 2, R / 4 resistor, intermediate node D, R / 4 resistor, node 3, node 4, R / 4 resistor, and node N. Figure 2 In the example, there are still lossless lines between nodes 1 and 2, and between nodes 3 and 4, with lengths of l / 2 (corresponding to a transmission delay of τ / 2). For the sake of clarity, the symbols of the time variables u and i are omitted.

[0102] exist Figure 2 In the example, nodes M-1, 2-3, and 4-N are all lumped parameter circuits without time delay, and can be solved directly using Ohm's law; for lossless lines between nodes 1-2 and 3-4, the result of formula (9) can be applied. In this way, through the Ohm's law of lumped parameter circuits and formula (9) of lossless lines, the corresponding line parameter calculation formula can be obtained through derivation.

[0103]

[0104] In the formula, h = R / (4Z C ) is a constant determined by the line parameters. R is the resistance of the entire length of the line MN; Z C is the wave impedance; the same method can also be used to calculate i N (t ) , this article will not go into details.

[0105] In this embodiment, the single-ended solution calculation formula is applied to the line setting protection range to obtain its line parameter calculation formula. Specifically, the MY line segment is the protection range set for the line, and K is assumed to be rel =Z set / ZMN , where Z MN is the positive sequence impedance of the entire length of the MN line; Z set K is the impedance setting for setting the protection range; rel is a constant that is less than 1 and is called the reliability coefficient. It can be understood that the MY line segment is equivalent to Figure 2 The entire circuit includes the lumped parameter part and the lossless circuit, so the voltage at point Y is also derived according to Ohm's law of the lumped parameter circuit and the lossless circuit. Applying formula (10) to calculate the voltage at point Y, we can get:

[0106]

[0107] According to the same proportional relationship, h in formula (11) changes to h = K rel R / (4Z C ); In the same way, we can also calculate i Y (t), which will not be elaborated in this paper.

[0108] u M (tK rel τ),u M (t),u M (t+K rel τ) are (tK rel τ)、t、(t+K rel τ) The voltage at terminal M at the moment;

[0109] i M (tK rel τ),i M (t), i M (t+K rel τ) are (tK rel τ)、t、(t+K rel τ) The current at terminal M at the moment;

[0110] K rel τ is the transmission delay of electromagnetic waves within the protection range MY set by the line;

[0111] τ represents the transmission delay of electromagnetic waves along the entire length of line MN.

[0112] Step 3: According to the line parameter calculation formula, a wave equation for obtaining the opposite-end voltage through the single-end electrical quantity is established to be used for the terminal electrical quantity calculation method of the three-phase lossy line, which is specifically as follows:

[0113] Formula (11) is applied to the symmetrical component method of three-phase transmission lines to obtain the voltage calculation method of the Berelon model. Taking the calculation of the voltage of the opposite end point Y on the M side as an example, when the end point Y of the protection range is determined, K relThe calculation parameters can be determined, and the time variables on the right side of the equation are adjusted to the sample values ​​that have been obtained. Then, after deduction, we can get:

[0114]

[0115] In the formula, E u =-Z C h(1-h 2 ), h=K rel R / (4Z C ) are all constant coefficients related to the line.

[0116] u M (tK rel τ),u M (t),u M (t-2K rel τ) are (tK rel τ), t, (t-2K rel τ) The voltage at terminal M at the moment;

[0117] i M (tK rel τ),i M (t), i M (t-2K rel τ) are (tK rel τ), t, (t-2K rel τ) The current at terminal M at the moment;

[0118] K rel τ is the transmission delay of electromagnetic waves within the protection range MY set by the line;

[0119] u Y (tK rel τ) is the opposite point Y of M end (tK rel The voltage at time τ.

[0120] The right side of formula (12) is the electrical quantity at the M terminal. This is the expression for obtaining the voltage at the opposite end Y terminal through the electrical quantity at the M terminal. This formula takes into account the influence of the distribution parameters of the transmission line and the transmission delay, and can more accurately reflect the actual relationship of the electrical quantity. Similarly, referring to the above derivation process, the expression for obtaining the voltage at the Y terminal through the electrical quantity at the N terminal can also be listed.

[0121] On the basis of formula (12), the instantaneous value expression of the three-phase voltage can be obtained by applying the symmetrical component method, Clarke transformation, Kalenberg transformation and other methods. At the same time, the voltage phasor can be obtained by the full-cycle Fourier algorithm, which is beneficial to enhance the filtering and anti-interference performance.

[0122] In addition, by further generalizing formula (12), it is easy to apply to the case where Q is an even number such as 4 or 8, and the line is divided into four segments, eight segments, or even more segments, thereby further improving the accuracy of the line model.

[0123] Step 4: After the transmission line within the protection range is segmented, the wave equation is applied to each segment to finally obtain the voltage phasor at the end of the protection range, which is combined with the measured phasor at the protection installation location to form the distance protection action condition (if the two are in phase, it indicates a short circuit outside the setting range; if the two are in opposite phases, it indicates a short circuit within the setting range) to perform distance protection on the transmission line.

[0124] exist Figure 3 When the metallic short circuit is shown in (a), the voltage phasor relationship between point M where the protection is installed and point Y at the end of the setting (set) protection range is plotted as Figure 3 (b), (c), (d), Figure 3 middle They all correspond to the voltage phasors of the wiring method, such as: 1) three-phase short circuit, two-phase short circuit, two-phase ground short circuit, Take the voltage difference of the fault phase, taking the short circuit between phases AB as an example, take 2) When a single-phase ground short circuit occurs, take A ground short circuit as an example,

[0125] Considering Z K =z1l K , Z set =Z Y =z1l Y , where Z set is the set impedance of the line protection range; z1 is the known positive sequence impedance per unit length of the line. Figure 3 (b), (c), and (d) can obtain the following characteristics:

[0126] (1) Z K =Z set Sometimes, there are

[0127] (2) Z K >Z set Sometimes, there are

[0128] (3) Z K <Z set Sometimes, there are

[0129] Among them, Z K , l K are the positive sequence impedance and length between the short-circuit point K and the measuring point M respectively;

[0130] ZY , l Y are the positive sequence impedance and length between the end Y of the protection range and the measurement point M respectively;

[0131] In (1), (2) and (3) above, Z is omitted according to the writing convention of relay protection. K and Z set The absolute value sign of .

[0132] Therefore, after the transmission line within the protection range is segmented, the single-ended solution of equation (12) is applied to each segment of the line, and finally the voltage phasor at point Y can be calculated and then compared with the measured phasor at the protection installation location. By performing phase comparison, a new distance protection method can be constructed. Summarizing the above characteristics (1), (2), and (3), the new distance protection action condition can be determined as:

[0133]

[0134] In the formula, To measure voltage phasors at the protection installation; is the voltage phasor at point Y calculated using the wave equation (12).

[0135] by Figure 3 Take the two-phase segment (e) as an example. In the case of three-phase short circuit, two-phase short circuit and two-phase ground short circuit, and Substitute into equation (12) to calculate the voltage u at point Y: Y1 (t), the current i at point Y can also be calculated using the same method. Y1 (t), and obtain the electrical quantity (u Y1 (t),i Y1 (t)), and then substitute the electrical quantity at point Y1 into equation (12) to calculate the voltage phasor at point Y: Used for comparison in formula (13);

[0136] In case of single-phase grounding, and Substitute into equation (12) to calculate the voltage u at point Y: Y1 (t), the current i at point Y can also be calculated using the same method. Y1 (t), after obtaining the electrical quantity at point Y1, substitute the electrical quantity at point Y1 into equation (12) to calculate the voltage phasor at point Y: Used for comparison in formula (13).

[0137] In the formula, They are the voltage phasor and current phasor of the measuring point at the protection installation respectively;

[0138] is the zero-sequence measurement current of the protection; K is the zero-sequence compensation coefficient of the transmission line.

[0139] When implementing the distance protection action condition shown in formula (13), the sampling value comparison and area integral comparison commonly used in engineering can also be used to achieve fast protection with an action speed of less than 20ms.

[0140] Embodiment 2 of the present invention provides a wave equation distance protection system, including:

[0141] The wave equation derivation module is used to obtain a single-end solution calculation formula for a lossless line taking into account the distributed parameters and transmission delay of the line based on a lossless distributed parameter model of the transmission line; the single-end solution calculation formula is applied to the protection range set for the line to obtain a line parameter calculation formula; and a wave equation for obtaining the opposite-end voltage through a single-end electrical quantity is established according to the line parameter calculation formula;

[0142] The distance protection module is used to divide the transmission line in the protection range into sections and apply the wave equation to each section to finally obtain the voltage phasor at the end of the protection range, and compare it with the measured voltage phasor at the protection installation location. If the distance protection action conditions are met, the distance protection of the transmission line is performed.

[0143] Embodiment 3 of the present invention provides a terminal, including a processor and a storage medium, wherein the storage medium is used to store instructions;

[0144] The processor is configured to operate according to the instructions to execute the steps of the method.

[0145] Embodiment 4 of the present invention provides a computer-readable storage medium having a computer program stored thereon, which implements the steps of the method when executed by a processor.

[0146] Compared with the prior art, the beneficial effects of the present invention include at least:

[0147] The present invention takes into account the influence of the distributed capacitance and transmission delay of the line, and is a new technology for short-circuit distance measurement. At the same time, when the line is grounded through a transition resistor and the line is overloaded, the distance protection of the present invention will not malfunction.

[0148] The distance protection structured by the present invention can be applied to power transmission lines that transmit industrial frequency quantities; it can also be applied to DC lines, or power transmission lines that transmit other frequency components;

[0149] The present invention decomposes the line protection range MY into more small segments (such as greater than or equal to four segments), and each small segment applies the wave equation solution of the opposite end voltage, which effectively improves the calculation accuracy;

[0150] The present invention applies the single-ended solution of the wave equation to the distance protection of the transmission line. In the process, various methods such as phase voltage, polarization voltage, memory voltage, symmetrical component method, etc. can be used to achieve it, which can be expanded to various action conditions.

[0151] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0152] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0153] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0154] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A wave equation distance protection method, characterized in that: The method comprises the following steps: Step 1: Establish a lossless line single-ended solution calculation formula for the transmission line taking into account the distributed parameters and transmission delay of the line; Step 2: Apply the single-ended solution calculation formula to the line setting protection range to obtain the line parameter calculation formula; Step 3: Establish a wave equation for obtaining the opposite-end electrical quantity through the single-end electrical quantity according to the line parameter calculation formula; Step 4: After the transmission line in the protection range is divided into sections, the wave equation is applied to each section to finally obtain the voltage phasor at the end of the protection range, which is compared with the measured voltage phasor at the protection installation location. If the distance protection action conditions are met, the distance protection of the transmission line is performed.

2. The distance protection method of a wave equation according to claim 1, characterized in that: The transmission line is a transmission line for transmitting industrial frequency components, a direct current transmission line, or a transmission line for transmitting other frequency components.

3. The distance protection method of a wave equation according to claim 1, characterized in that: Step 1 specifically includes: Step 11: For the transmission line MN, establish the basic equation of the lossless distributed parameter conductor when the line MN is fully connected; Step 12, solving the basic equation to obtain the relationship between the electrical quantities at both ends of the line and the forward wave and reverse wave voltages; Step 13: After comparing and merging the relationship between the electrical quantities at both ends of the line and the forward and reverse wave voltages, a single-ended solution formula for a lossless line is obtained by solving the formula in conjunction with the distributed parameters and transmission delay of the line.

4. The distance protection method of a wave equation according to claim 3 is characterized in that: In step 11, the basic equation of the lossless distributed parameter conductor when the line MN is connected completely is: In the formula, x represents the position, i and u are the line current and voltage; L0 and C0 are the inductance and capacitance per unit length of the line respectively.

5. The distance protection method of a wave equation according to claim 4 is characterized in that: In step 12, M is the line head end, the position coordinate at the head end is x=0, and the voltage is u M ; N is the end of the line, the position coordinate of the end is x=l, and the voltage is u N , solving the basic equation, the relationship between the electrical quantities at both ends of the line and the forward and reverse wave voltages is as follows: In the formula, τ = l / v, which represents the transmission delay of electromagnetic waves along the entire length of the line; l and v are the total length of the line and the transmission speed of electromagnetic waves respectively; It represents wave impedance; u M (t), i M (t) are the voltage and current at the M terminal at time t; u N (t+τ), i N (t+τ) are the voltage and current at the N terminal at time t+τ respectively; u N (t-τ), i N (t-τ) are the voltage and current at the N terminal at time t-τ respectively; u f (t),u b (t) are the forward wave and reverse wave voltages at time t respectively.

6. A wave equation distance protection method according to claim 5, characterized in that: In step 13, compare equation (4) and equation (5), and according to u in the two equations f (t),u b (t) respectively correspond to the same conditions, and we get: will u M (t), i M (t) is an unknown variable, and u N (t+τ), i N (t+τ),u N (t-τ), i N (t-τ) is used as the available measurement signal, and equations (6) and (7) are solved together to obtain the lossless line single-ended solution calculation formula that uses the N-end electrical quantity to describe the M-end electrical quantity: According to the reciprocity property of the two ends of the line MN, the single-ended solution expression of the lossless line is obtained by using the electrical quantity at the M end to obtain the electrical quantity at the N end:

7. The distance protection method of a wave equation according to claim 1, characterized in that: The line parameter calculation formula obtained in step 2 is: Where h = K rel R / (4Z C ) is a constant determined by line parameters; R is the resistance of the entire length of line MN; Z C is the wave impedance; K rel =Z set / Z MN is the reliability coefficient, Z MN is the positive sequence impedance of the entire length of line MN, Z set Set the set impedance of the protection range MY for the line; u Y (t) is the voltage at point Y at time t; u M (tK rel τ),u M (t),u M (t+K rel τ) are (tK rel τ)、t、(t+K rel τ) The voltage at terminal M at the moment; i M (tK rel τ),i M (t), i M (t+K rel τ) are (tK rel τ)、t、(t+K rel τ) The current at terminal M at the moment; K rel τ is the transmission delay of electromagnetic waves within the protection range MY set by the line; τ represents the transmission delay of electromagnetic waves along the entire length of line MN.

8. The distance protection method of a wave equation according to claim 1, characterized in that: In step 3, when the M terminal is used as the known terminal of the electrical quantity and Y terminal is used as the opposite terminal of the voltage to be determined, the wave equation for obtaining the opposite terminal voltage through the single-terminal electrical quantity is established as follows: In the formula, B u =-h 2 , E u =-Z C h(1-h 2 ), h=K rel R / (4Z C ) are all constant coefficients related to the line; u M (tK rel τ),u M (t),u M (t-2K rel τ) are (tK rel τ), t, (t-2K rel τ) The voltage at terminal M at the moment; i M (tK rel τ),i M (t), i M (t-2K rel τ) are (tK rel τ), t, (t-2K rel τ) The current at terminal M at the moment; K rel τ is the transmission delay of electromagnetic waves within the protection range MY set by the line; u Y (tK rel τ) is the opposite end Y of M at (tK rel The voltage at time τ.

9. The distance protection method of a wave equation according to claim 1, characterized in that: In step 4, the distance protection action condition is: the voltage phasor at the end of the protection range is opposite in phase to the measured voltage phasor at the protection installation; When the above conditions are met, the distance protection of the transmission line will be activated.

10. A wave equation distance protection system, using the method according to any one of claims 1 to 9, characterized in that: The system comprises: The wave equation derivation module is used to establish a lossless line single-end solution calculation formula for the transmission line taking into account the distributed parameters and transmission delay of the line; the single-end solution calculation formula is applied to the line setting protection range to obtain the line parameter calculation formula; according to the line parameter calculation formula, a wave equation is established to obtain the opposite end electrical quantity through the single-end electrical quantity; The distance protection module is used to divide the transmission line in the protection range into sections and apply the wave equation to each section to finally obtain the voltage phasor at the end of the protection range, and compare it with the measured voltage phasor at the protection installation location. If the distance protection action conditions are met, the distance protection of the transmission line is performed.

11. A terminal comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1-9.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 9 are implemented.

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