A new energy station sending line adaptive distance protection method and device

Abstract

The present application relates to a kind of new energy field station sending line adaptive distance protection method and device, belong to the technical field of power system relay protection.The present application is according to the relationship between three-phase voltage, three-phase current, circuit parameter and fault distance, using the three-phase voltage and three-phase current data sample data fitting to obtain fault distance, and remove the sampling data of which fitting error of fault distance is greater than fitting error threshold value, re-fitting to obtain final fault distance, according to final fault distance to judge fault occurrence position, by comparing fitting error and threshold value, remove the sampling data that leads to larger fitting error, wherein, fitting error threshold value is set as the product of reliable coefficient and the average of fitting error square, set reliable coefficient to flexibly select threshold value, to ensure the rationality and accuracy of threshold value setting, make the calculation result of fault distance more accurate, so as to accurately distinguish fault as in-zone fault or out-of-zone fault.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power system relay protection, and particularly relates to a new energy station sending-out line adaptive distance protection method and device. BACKGROUND

[0002] At present, the construction of new energy stations is booming, and with the access of large-scale new energy power sources, the equivalent internal impedance of the new energy power sources will change during system failure. However, large-scale new energy stations are usually connected to the high-voltage alternating current grid through sending-out lines, which greatly affects the applicability of the traditional distance protection of new energy sending-out lines. At the same time, the weak feedback, high harmonic and frequency deviation characteristics of the wind power system and the instability of the system impedance make the distance protection of the new energy sending-out line have adaptability problems.

[0003] Due to the weak feedback, high harmonic and frequency deviation characteristics and the instability of the system impedance of the new energy power source, the equivalent impedance of the new energy power source will change during system failure, which makes the error between the fault distance calculated by the traditional power frequency phasor distance protection algorithm and the actual fault distance be large, and thus the in-zone and out-zone faults cannot be accurately distinguished. SUMMARY

[0004] The purpose of the application is to provide a new energy station sending-out line adaptive distance protection method and device to solve the problem that the in-zone and out-zone faults cannot be accurately distinguished when the new energy power station sending-out line has a near-zone fault.

[0005] To solve the above technical problems, the application provides a new energy station sending-out line adaptive distance protection method, which comprises the following steps:

[0006] 1) According to the relationship between the three-phase voltage, the three-phase current, the circuit parameters and the fault distance, the sampling data of the three-phase voltage and the three-phase current at each time after the fault and the circuit parameters at each time in a time window are combined to fit the fault distance at each time in the window.

[0007] 2) The fitting error of the fault distance at each time in the window is calculated, the sampling data with a fitting error greater than a fitting error threshold value is removed, and the final fault distance is obtained by using the circuit parameters and the remaining sampling data and combining the relationship fitting, wherein the fitting error threshold value is the product of the average value of all fitting error squares and a reliability coefficient, and the reliability coefficient is greater than 0.

[0008] 3) According to the final fault distance at each time in the time window selected for fault discrimination, it is judged whether an in-zone fault or an out-zone fault occurs in the time window for fault discrimination.

[0009] Further, the fitting is realized by a linear fitting algorithm.

[0010] Further, the linear fitting algorithm is least square method.

[0011] Further, the relationship between the three-phase voltage, the three-phase current, the circuit parameter and the fault distance is specifically as follows:

[0012]

[0013] In the formula, t represents the calculation time after the fault, u mj (t) is the j-phase measured voltage at the installation of the protection after the fault, j=a, b, c represents the a-phase, the b-phase and the c-phase, d is the fault distance, l is the line unit length inductance, i mj (t) represents the j-phase measured current at the installation of the protection after the fault, r is the line unit length resistance, R f is the transition resistance, i m0 (t) represents the zero sequence current at the installation of the protection after the fault.

[0014] Further, the fault distance fitting error calculation formula is as follows:

[0015]

[0016] In the formula, t1 is the calculation time in the time window, δ(t1) is the fitting error, u mj (t1) is the j-phase measured voltage at the installation of the protection after the fault, j=a, b, c represents the a-phase, the b-phase and the c-phase, d0(t1) is the fault distance in the time window, l is the line unit length inductance, i mj (t1) represents the j-phase measured current at the installation of the protection after the fault, r is the line unit length resistance, R f is the transition resistance, i m0 (t1) represents the zero sequence current at the installation of the protection after the fault.

[0017] Further, the specific method for judging whether the internal fault or the external fault occurs in the time window selected for judging the fault according to the final fault distance of each time in the time window is as follows: if the final fault distance in the time window selected for judging the fault is greater than 0 and less than the setting value, it is judged that the internal fault occurs, otherwise, the external fault occurs.

[0018] Further, the setting value is less than the full length of the protected line.

[0019] To solve the above technical problems, the application further provides a new energy station sending line adaptive distance protection device, which comprises a memory and a processor, and computer program instructions stored in the memory and running on the processor, and the processor is used for executing the computer program instructions stored in the memory to realize the new energy station sending line adaptive distance protection method.

[0020] The beneficial effects of the above technical solution are: the present application is an improved invention, according to the relationship between three-phase voltage, three-phase current, circuit parameters and fault distance, the actual collected three-phase voltage and three-phase current data sampling data are used to fit the fault distance, and the sampling data with a fitting error greater than the fitting error threshold value is removed, the remaining sampling data is re-fitted to obtain the final fault distance, and the fault occurrence position is judged according to the final fault distance; the sampling data with a large fitting error is removed through the comparison of the fitting error and the fitting threshold value, wherein the fitting error threshold value is set as the product of the average value of the reliable coefficient and the square of the fitting error, the reliable coefficient is set to flexibly select the fitting error threshold value, to ensure the rationality and accuracy of the threshold value setting, so that the calculation result of the fault distance is more accurate, so that the fault can be accurately distinguished as an intra-zone fault or an extra-zone fault. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a structural schematic diagram of the new energy station sending-out line adaptive distance protection method embodiment of the present application;

[0022] Figure 2 is a comparison diagram of intra-zone fault calculation results of the new energy station sending-out line adaptive distance protection method embodiment of the present application;

[0023] Figure 3 is a comparison diagram of extra-zone fault calculation results of the new energy station sending-out line adaptive distance protection method embodiment of the present application. DETAILED DESCRIPTION

[0024] The present application focuses on providing a new energy station sending-out line adaptive distance protection method, comprising the following steps:

[0025] 1) according to the relationship between three-phase voltage, three-phase current, circuit parameters and fault distance, combining the sampling data of three-phase voltage and three-phase current collected at each time after the fault at the protection installation place in a time window and the circuit parameters, fitting out the fault distance at each time in the window;

[0026] 2) calculating the fitting error of the fault distance at each time in the window, removing the sampling data with a fitting error greater than the fitting error threshold value, using the circuit parameters and the remaining sampling data and combining the relationship to fit the final fault distance, wherein the fitting error threshold value is the product of the average value of all fitting error squares and the reliable coefficient, and the reliable coefficient is greater than 0;

[0027] 3) judging whether an intra-zone fault or an extra-zone fault occurs in the time window for judging the fault according to the final fault distance at each time in the selected time window for judging the fault.

[0028] The application utilizes the actual collected three-phase voltage and three-phase current data samples to fit the fault distance, removes the sample data with the fault distance fitting error greater than the fitting error threshold, re-fits the remaining sample data to obtain the final fault distance, and judges the fault occurrence position according to the final fault distance; the sample data with a large fitting error is removed through the comparison of the fitting error and the fitting threshold, wherein the fitting error threshold is set as the product of the reliable coefficient and the average value of the fitting error square, the reliable coefficient is set to flexibly select the fitting error threshold, so as to ensure the rationality and accuracy of the threshold setting, make the calculation result of the fault distance more accurate, and thus accurately distinguish the fault as an intra-zone fault or an extra-zone fault.

[0029] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples.

[0030] Embodiment of the adaptive distance protection method for the outgoing line of the new energy station:

[0031] The outgoing system of the new energy station includes a new energy station, an equivalent power source of an external system, an outgoing line, and a relay protection device on the M side and the N side of the outgoing line. Figure 1

[0032] The adaptive distance protection method for the outgoing line of the new energy station in the embodiment includes the following steps:

[0033] S1: When a fault occurs in the outgoing line of the new energy power station, the three-phase measured voltage and current at the protection installation after the fault are obtained.

[0034] S2: According to the three-phase measured voltage and current at the protection installation after the fault, an equation related to the fault distance is obtained in combination with the line model.

[0035] The specific steps of S2 are as follows: according to the three-phase measured voltage and current at the protection installation after the fault, an equation related to the fault distance is obtained in combination with the line model. mj (t) = d·Δu j (t) + u fj (t), wherein t represents the calculation time after the fault; u mj (t) is the j-phase measured voltage at the protection installation after the fault; Δu j (t) represents the unit length voltage drop between the protection installation on the M side of the line and the fault point, and the calculation formula is Δu j (t) = f(i mj (t), r, l, c), wherein i mj ​(t) represents the measured current at the protection installation after the fault; r, l, c are the line resistance, inductance and capacitance per unit length, respectively; u fj (t) is the fault point voltage, and the calculation formula is u fj (t) = g(i m0 (t), R f ), i m0 (t) represents the zero sequence current at the protection installation after the fault; R f is the transition resistance; j = a, b, c represents phase a, phase b, and phase c; Δu j (t) can be calculated by the following formula: u fj (t) can be calculated by the following formula: u fj (t) = R f ·i m0 (t).

[0036] S3: Select a suitable data window, and fit the fault distance in this time window by the best linear fitting.

[0037] The specific steps of S3 are to select a suitable time window T W1 , and the sampling data of the three-phase voltage and three-phase current of the protection installation after the fault at each sampling time in the time window [t-T W1 , t] can obtain the fault distance equation in step S2, thereby obtaining the fault distance equation group; the fault distance equation group can be solved by linear fitting to obtain the fault distance d0(t) in this time window. t represents the current time after the fault. In this embodiment, T w1 = 10 ms, and the best linear fitting algorithm is the least square algorithm.

[0038] S4: Sort the fitting errors of the fault distance in this time window, discard the sampling data whose fitting error is higher than the threshold value, and bring the remaining sampling data into step 3 again to obtain the corresponding final fault distance d1(t).

[0039] The fault distance fitting error in S4 is calculated by the following formula:

[0040] δ(t1) = u mj (t1) - d0(t1) · Δu j (t1) + u fj (t1)

[0041] Wherein, t1 is any sampling time in the time window, and Δu j (t1) can be calculated by the following formula: u fj (t) can be calculated by the following formula: u fj (t) = R f ·i m0(t), δ(t1) is the fitting error, u mj (t1) is the measured voltage at the protection installation after the fault, d0(t1) is the fault distance within the time window, l is the unit length inductance of the line, i mj (t1) represents the measured current at the protection installation after the fault, r is the unit length resistance of the line, R f is the transition resistance, i m0 (t1) represents the zero sequence current at the protection installation after the fault.

[0042] The fitting error threshold is the average value of the squares of all fitting errors [δ(t1)] 2 within the time window The fitting error threshold is set as the product of the reliability coefficient and the average value of the squares of the fitting errors , wherein the value of the reliability coefficient is greater than 0, and the reliability coefficient K is set to flexibly adjust the fitting error threshold, so as to ensure the rationality and accuracy of the threshold setting. The sampling data whose fault distance fitting error is greater than within the time window [t-T W1 , t] is removed, and the remaining sampling data is brought into step 3 again to obtain the corresponding final fault distance d1(t).

[0043] S5: The fault distance input into the distance protection criterion is brought into the preset criterion to distinguish between internal and external faults.

[0044] The specific steps of S5 are to bring the calculated final fault distance d1(t) into the preset criterion, select a suitable time window T W2 for distinguishing faults, and if d1(t) continuously satisfies 0 < d1(t) < d W2 within the time window [t-T set , t], it is considered that an internal fault occurs; if it does not satisfy, it is considered that an external fault occurs. Wherein d set is the setting value, and the setting value is less than the full length of the protected line. In this embodiment, d set is 0.67 times the full length of the line.

[0045] Compared with the traditional method, the fault calculated in this embodiment improves the accuracy of distinguishing internal and external faults. When an internal fault occurs, the calculation result of this embodiment compared with the calculation result of the traditional algorithm is specifically shown in Table 1, and when an external fault occurs, the calculation result of this embodiment compared with the calculation result of the traditional algorithm is specifically shown in Table 2. Figure 2 Figure 3

[0046] New energy station sending line adaptive distance protection device embodiment:

[0047] ​​The application further provides a new energy station outgoing line adaptive distance protection device, which comprises a memory and a processor, and a computer program stored in the memory and running on the processor, and the processor is used for executing the computer program instructions stored in the memory to realize the new energy station outgoing line adaptive distance protection method. The specific process has been described in detail in the embodiment of the new energy station outgoing line adaptive distance protection method, and will not be repeated here. Among them, the processor can select a microprocessor MCU, a programmable logic device FPGA and the like processing device, and the memory can select a mobile hard disk, a read-only memory (ROM), a random access memory (RAM) and the like storage device.

[0048] The above gives a specific embodiment, but the application is not limited to the described embodiment. The basic idea of the application is the above basic scheme, and according to the teaching of the application, various transformed models, formulas and parameters can be designed without creative labor. Changes, modifications, replacements and variations of the embodiments without departing from the principles and spirits of the application still fall within the protection scope of the application.

Claims

1. A new energy field station sending line adaptive distance protection method, characterized in that, The method comprises the following steps: 1) according to the relationship between three-phase voltage, three-phase current, circuit parameters and fault distance, combining the sampling data of three-phase voltage and three-phase current at each time after the fault and the circuit parameters collected in a time window, fitting the fault distance at each time in the time window; the relationship is: t The calculation time after the fault. u mj ( t (This refers to the installation location for post-fault protection) t The measured voltage of phase j at time t, where j = a, b, and c represent phases a, b, and c, respectively. d The distance to the fault. l Inductance per unit length of the line, i mj ( t (This refers to the installation location for post-fault protection) t The measured current of phase j at time t. r The resistance per unit length of the line. R f For transition resistance, i m0 ( t ) after the fault t Protect the zero-sequence current at the installation location at all times; 2) calculating the fitting error of the fault distance at each time in the time window, removing the sampling data with fitting error greater than the fitting error threshold value, and fitting the final fault distance by using the circuit parameters and the remaining sampling data in combination with the relationship, wherein the fitting error threshold value is the product of the average value of all fitting error squares and the reliability coefficient, and the reliability coefficient is greater than 0; 3) judging whether an internal fault or an external fault occurs in the time window selected for fault discrimination according to the final fault distance at each time in the time window.

2. The method of claim 1, wherein the method further comprises: The fitting is realized by a linear fitting algorithm.

3. The method of claim 2, wherein the method further comprises: The linear fitting algorithm is the least square method.

4. The method of claim 1, wherein the method further comprises: The fault distance fitting error calculation formula is: wherein, t 1 is the calculation time within the time window, δ( t 1) is the t 1 time fitting error, u mj ( t 1) is the j-phase measured voltage at the protection installation at the time t 1, d 0( t 1) is the fault distance within the time window t 1, i mj ( t 1) represents the j-phase measured current at the protection installation at the time t 1, i m0 ( t 1) represents the zero sequence current at the protection installation at the time t 1.

5. The method of claim 1, wherein the method further comprises: The specific method for judging whether an internal fault or an external fault occurs in the time window selected for fault discrimination according to the final fault distance at each time in the time window is: if the final fault distance in the time window selected for fault discrimination is greater than 0 and less than the setting value, it is determined that an internal fault occurs, otherwise, an external fault occurs.

6. The method of claim 5, wherein the method further comprises: The setting value is less than the full length of the protected line.

7. A new energy station sending line adaptive distance protection device, characterized in that, The device comprises a memory and a processor, and computer program instructions stored in the memory and running on the processor, and the processor is used to execute the computer program instructions stored in the memory to realize the new energy station sending line adaptive distance protection method according to any one of claims 1-6.

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