A time-domain distance protection method and system for new energy transmission line

Abstract

The application discloses a time-domain distance protection method and system for new energy sending-out lines, which establishes a metallic grounding fault model according to a pi-type line, establishes a fault position function in a time domain range, accumulates the absolute values of the numerator and denominator of the fault position function of each sampling interval by using a geometric progression theorem to obtain a fault position correction function; when a fault occurs in a power grid, the fault position is calculated through the fault position correction function, and corresponding protection actions are performed; the application is not affected by the denominator zero-crossing point of the fault position function, the numerical value is stable near the denominator zero-crossing point, and the in-zone fault can be accurately identified under different fault positions and different fault types.

Description

TECHNICAL FIELD

[0001] The application relates to a time-domain distance protection method and system, in particular to a time-domain distance protection method and system for a new energy sending-out line. BACKGROUND

[0002] As a large energy demand country, the rapid development of power electronic technology related to renewable energy in China has made the cost of new energy power generation lower year by year. China has rich clean energy reserves and good development conditions, and has a bright market prospect. The new energy industry has developed rapidly, and a high proportion of new energy grid-connected capacity will bring an unavoidable impact on the safe and stable operation of the power grid. At present, the protection methods in the protection system of the transmission line mainly include double-end quantity protection and single-end quantity protection. Since high-voltage transmission lines are basically long-distance transmission, the distribution capacitance causes poor speed, and in addition, the double-end quantity protection requires strict data synchronization, and the communication channel in the protection system can greatly reduce the action reliability of the protection. Therefore, compared with the double-end quantity protection, the single-end quantity protection has higher reliability and economic benefits, and it is of great significance to study and improve the line protection system based on the single-end quantity.

[0003] The conventional time-domain distance protection principle considering the capacitive current accurately considers the influence of the capacitive current in the conventional system, and when a long-distance fault occurs, all electrical quantities are filtered by a band-pass filter with a center frequency of 50Hz, and the 50Hz power frequency electrical quantity is extracted. The differential error is corrected by using the differential correction formula, so that the fault position can be accurately calculated. However, after the new energy is connected to the grid, there is a frequency offset problem, and the electrical quantity after the fault also has a speed frequency component of 35-65Hz, which cannot be filtered out by the band-pass filter, and the differential error cannot be directly corrected by using the fixed frequency differential error formula. The difference in frequency component content will cause the calculation result to jump in the sliding window calculation process of the protection algorithm, which will cause the protection to refuse to act when an internal fault occurs. SUMMARY

[0004] The application aims to provide a time-domain distance protection method for a new energy sending-out line, which is accurate and stable in calculation; and a second object of the application is to provide a time-domain distance protection system for a new energy sending-out line, which is accurate and stable in calculation.

[0005] The technical scheme of the application is as follows: the time-domain distance protection method for a new energy sending-out line comprises the following steps: a metallic grounding fault model is established according to a pi-type line, a fault position function is established in the time domain, and the absolute values of the numerator and the denominator of the fault position function of each sampling interval are accumulated by using the geometric progression theorem to obtain a fault position correction function; when a fault occurs in the power grid, the fault position is calculated by using the fault position correction function, and corresponding protection actions are performed.

[0006] Further, the metal ground fault model is established according to the pi type line, and the fault position function is established in a time domain range, including: a time domain distance protection system model is established by taking into account the capacitive current, after the new energy is connected to the grid, data after the fault is collected by the protection device, the fault position is taken as an unknown variable, a distance measurement mathematical model is established in a time domain range, and an equation about the fault position is obtained; for any fault type, the equation about the fault position is:

[0007]

[0008] Wherein, u and i are the voltage and current at the installation position of the protection device, R, L and C are the resistance, inductance and capacitance per unit length of the line, and p is the distance from the fault point to the installation position of the protection device.

[0009] Further, the fault position function is:

[0010] p=(c k+1 b k -c k b k+1 ) / (a k b k+1 -b k a k+1 )

[0011] Wherein, p is the distance from the fault point to the installation position of the protection device, c k is the voltage at the installation position of the protection device at k moment, a k , b k are time correlation coefficient values at k moment, c k+1 is the voltage at the installation position of the protection device at k+1 moment, a k+1 , b k+1 are time correlation coefficient values at k+1 moment.

[0012] Further, the fault position correction function is:

[0013]

[0014] Wherein, p is the distance from the fault point to the installation position of the protection device, c k is the voltage at the installation position of the protection device at k moment, a k , b k are time correlation coefficient values at k moment, c k+1 is the voltage at the installation position of the protection device at k+1 moment, a k+1 , b k+1 are time correlation coefficient values at k+1 moment, and m is the sampling number.

[0015] Further, the power grid failure includes a single-phase ground fault of a three-phase power grid system, and when the power grid has a single-phase ground fault, the coefficients of the fault location correction function are respectively:

[0016]

[0017]

[0018] c k = u ak+1

[0019] wherein r1, L1 and C1 are positive sequence resistance, positive sequence inductance and positive sequence capacitance respectively, r0, L0 and C0 are zero sequence resistance, zero sequence inductance and zero sequence capacitance respectively; u ak+1 is a phase voltage value at k+1 moment, u 0k+1 is a zero sequence voltage value at k+1 moment; T S is a sampling time; i ak , i ak+1 and i ak+2 are a phase current value at k moment, k+1 moment and k+2 moment respectively, i 0k , i 0k+1 and i 0k+2 are zero sequence current values at k moment, k+1 moment and k+2 moment respectively, K R = (r0-r1) / 3r1, K L = (L0-L1) / 3L1, K C1 = C1 / 2, K C2 = C0 / 2, K C3 = (C0-C1) / 2.

[0020] Further, the power grid failure includes a two-phase inter-phase short circuit fault of a three-phase power grid system, and when the power grid has a bc-phase inter-phase short circuit fault, the coefficients of the fault location correction function are respectively:

[0021]

[0022]

[0023] c k = u ak+1

[0024] wherein u bck-1 , u bck+1 , u bck+2 and u bck+3 are bc-phase inter-phase voltage values at k-1 moment, k+1 moment, k+2 moment and k+3 moment respectively, u ak+1 is a phase voltage value at k+1 moment, i bck , i bck+1and i bck+2 These represent the phase-to-phase current values ​​of bc at times k, k+1, and k+2, respectively. r1, L1, and C1 represent the positive-sequence resistance, positive-sequence inductance, and positive-sequence capacitance, respectively. K C1 =C1 / 2.

[0025] The time-domain distance protection system for new energy transmission lines according to the present invention includes:

[0026] The fault location calculation module is used to establish a metallic grounding fault model based on the π-type line, establish a fault location function in the time domain, and use the proportional theorem to accumulate the absolute values ​​of the numerator and denominator of the fault location function for each sampling interval to obtain the fault location correction function.

[0027] The time-domain distance protection module is used to calculate the fault location through the fault location correction function and perform corresponding protection actions when a fault occurs in the power grid.

[0028] The fault location correction function in the fault location calculation module is:

[0029]

[0030] The electronic device of the present invention includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded into the processor, it implements the time-domain distance protection method for the new energy transmission line.

[0031] The computer-readable storage medium of the present invention stores a computer program, which, when executed by a processor, implements the time-domain distance protection method for the new energy transmission line.

[0032] Beneficial effects: Compared with the prior art, the advantages of the present invention are: The present invention is not affected by the zero crossing of the denominator, the fault location calculated near the zero crossing of the denominator is stable and highly reliable. Under the fault conditions in the zone, under different fault locations and different fault types, it is not affected by frequency offset and line capacitance current, can accurately identify faults in the zone, and protect reliably. It is simple to implement and is suitable for new energy grid-connected systems. Attached Figure Description

[0033] Figure 1 This is a flowchart of the time-domain distance protection method of the present invention. Detailed Implementation

[0034] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0035] like Figure 1 As shown, the time-domain distance protection method for the new energy transmission line includes the following steps:

[0036] Step 1, establish the metallic ground fault model according to the π-type line, collect the post-fault data at a certain sampling rate, take the fault location as an unknown variable, and establish a mathematical model for distance measurement in the time domain, which is applicable to the capacitive current, to obtain a quadratic equation about the fault location.

[0037] The time-domain distance protection principle considering the capacitive current is as follows:

[0038]

[0039] Wherein, u and i are the voltage and current at the protection installation, R, L and C are the resistance, inductance and capacitance per unit length of the line, and p is the distance from the fault point to the protection installation. The fault location equation can be simplified as:

[0040] c(t) = pa(t) + p 2 b(t)

[0041] Wherein, p, p 2 is the fault location parameter to be solved, c(t) is the voltage, a(t), b(t) are the coefficients related to p, p 2 and time t respectively.

[0042] Step 2, discretize the sampling data, and obtain the calculation expression of the fault location in each sampling interval as follows:

[0043]

[0044] Wherein, T S is the sampling interval. Then the calculation expression of p and p 2 can be solved as:

[0045] p = (c k+1 b k - c k b k+1 ) / (a k b k+1 - b k a k+1 )

[0046] p 2 = (c k+1 a k - c k a k+1 ) / (a k b k+1 - b k a k+1 )

[0047] Under the same error condition, p = (c k+1 b k - ck b k+1 ) / (a k b k+1 -b k a k+1 )The fault location calculation is less disturbed, and the fault location is calculated herein.

[0048] Step 3, using the geometric progression theorem, the numerator and denominator of the fault location expression obtained in each sampling interval are accumulated to calculate the absolute value, and the fault location solving equation is corrected to obtain the modified calculation formula of p:

[0049]

[0050] Wherein, p is the fault location variable, c k is the voltage at the protection at time k, a k , b k is the coefficient at time k, and m is the number of acquisitions.

[0051] Specifically, for single-phase ground fault, taking phase a as an example, there are:

[0052]

[0053]

[0054] c k =u ak+1

[0055] Wherein: r1, L1, C1 are positive sequence resistance, positive sequence inductance and positive sequence capacitance respectively, r0, L0, C0 are zero sequence resistance, zero sequence inductance and zero sequence capacitance respectively; u ak+1 is the voltage value of phase a at time k+1, u 0k+1 is the zero sequence voltage value at time k+1; T S is the sampling time. It can be calculated that: K R =(r0-r1) / 3r1, K L =(L0-L1) / 3L1; K C1 =C1 / 2, K C2 =C0 / 2K C3 =(C0-C1) / 2.

[0056] For phase-to-phase short circuit, taking bc phase-to-phase short circuit as an example, there are:

[0057]

[0058]

[0059] c k =u ak+1

[0060] wherein: u bck+1 is the bc phase voltage value at k+1 moment, i bck is the bc phase current value at k+1 moment.

[0061] Step 4, the specific fault location is solved, whether the fault point is located in the protection range, whether the protection action setting value is met, and the protection action is controlled when the fault location is located in the protection range. In the embodiment, the p value (0<p<1) calculated is considered to be located in the protection range if falling on the line.

[0062] In the embodiment, after the specific fault location is solved, the root mean square error (RMSE) and the maximum deviation (MAB) are used to further measure the deviation between the calculation result and the true value, and the result is considered to be correct when the deviation value does not exceed 5%.

[0063] The RMSE calculation formula is as follows:

[0064]

[0065] The MAB calculation formula is as follows:

[0066]

[0067] wherein, n is the number of data points, is the true value, y i is the true fault location.

[0068] The time-domain distance protection system of the new energy sending line provided by the application comprises:

[0069] A fault location calculation module is configured to establish a metallic grounding fault model according to a pi-type line, establish a fault location function in a time domain range, and accumulate the absolute values of the numerator and denominator of the fault location function of each sampling interval by using the geometric progression theorem to obtain a fault location correction function.

[0070] A time-domain distance protection module is configured to calculate the fault location by using the fault location correction function when a fault occurs in the power grid and perform corresponding protection actions.

[0071] The fault location correction function in the fault location calculation module is as follows:

[0072]

[0073] The electronic device provided by the application comprises a memory, a processor, and a computer program stored in the memory and capable of running on the processor, and the computer program realizes the time-domain distance protection method of the new energy sending line when loaded into the processor.

[0074] The computer readable storage medium of the application stores a computer program, and the computer program is executed by a processor to implement the time domain distance protection method of the new energy sending line.

[0075] The computer readable storage medium can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory or any other medium that can be used to store desired program codes in the form of instructions or data structures and can be accessed by a computer.

[0076] The processor is used to execute the computer program stored in the memory to realize each step in the method related to the above-mentioned embodiments.

Claims

1. A time-domain distance protection method for new energy sending-out lines, characterized in that, The method comprises the following steps: establishing a metallic ground fault model according to a π-type line, establishing a fault location function in a time domain range, and accumulating the absolute values of the numerator and denominator of the fault location function of each sampling interval by using the geometric progression theorem to obtain a fault location correction function; when a power grid fault occurs, the fault location is calculated by using the fault location correction function, and corresponding protection actions are performed. The fault location function is: p = (c k+1 b k -c k b k+1 ) / (a k b k+1 -b k a k+1 ) wherein p is the distance from the fault point to the installation of the protection device, c k is the voltage at the installation of the protection device at time k, a k , b k is the time correlation coefficient value at time k, c k+1 is the voltage at the installation of the protection device at time k+1, a k+1 , b k+1 is the time correlation coefficient value at time k+1. The fault location correction function is: wherein p is the distance from the fault point to the installation of the protection device, c k is the voltage at the installation of the protection device at time k, a k , b k is the time correlation coefficient value at time k, c k+1 is the voltage at the installation of the protection device at time k+1, a k+1 , b k+1 is the time correlation coefficient value at time k+1, and m is the sampling number.

2. The time-domain distance protection method for new energy sending-out line according to claim 1, characterized in that, The step of establishing a metallic ground fault model according to a π-type line and establishing a fault location function in a time domain range comprises the following steps: establishing a time domain distance protection system model considering the capacitive current, collecting post-fault data by using a protection device after new energy is connected to the grid, taking the fault location as an unknown variable, establishing a distance measurement mathematical model in a time domain range, and obtaining an equation about the fault location; for any fault type, the equation about the fault location is: Wherein, u and i are the voltage and current at the installation position of the protection device, R, L and C are the resistance, inductance and capacitance per unit length of the line, and p is the distance from the fault point to the installation position of the protection device.

3. The time-domain distance protection method for new energy sending-out line according to claim 1, characterized in that, The power grid fault comprises a single-phase ground fault of a three-phase power grid system, and when the power grid has a single-phase ground fault, the coefficients of the fault location correction function are as follows: c k = u ak+1 Wherein, r1, L1 and C1 are positive sequence resistance, positive sequence inductance and positive sequence capacitance respectively, r0, L0 and C0 are zero sequence resistance, zero sequence inductance and zero sequence capacitance respectively; u ak+1 is a-phase voltage value at k+1 moment, u 0k+1 is zero sequence voltage value at k+1 moment; T S is sampling time; i ak , i ak+1 and i ak+2 are a-phase current values at k moment, k+1 moment and k+2 moment respectively, i 0k , i 0k+1 and i 0k+2 are zero sequence current values at k moment, k+1 moment and k+2 moment respectively, K R =(r0-r1) / 3r1, K L =(L0-L1) / 3L1, K C1 =C1 / 2, K C2 =C0 / 2, K C3 =(C0-C1) / 2.

4. The time-domain distance protection method for new energy sending-out line according to claim 1, characterized in that, The power grid fault comprises a two-phase inter-phase short circuit fault of a three-phase power grid system, and when the power grid has a bc-phase inter-phase short circuit fault, the coefficients of the fault location correction function are as follows: c k = u ak+1 wherein u bck-1 , u bck+1 , u bck+2 and u bck+3 are the bc phase-to-phase voltage values at the k-1, k+1, k+2 and k+3 instants, u ak+1 is the a phase voltage value at the k+1 instant, i bck , i bck+1 and i bck+2 are the bc phase-to-phase current values at the k, k+1 and k+2 instants, r1, L1 and C1 are the positive sequence resistance, inductance and capacitance, respectively, and K C1 =C1 / 2.

5. A time-domain distance protection system for a new energy sending-out line, characterized in that, The method comprises the following steps: The fault location calculation module is configured to establish a metallic ground fault model according to a π-type line, establish a fault location function in a time domain range, and accumulate the absolute values of the numerator and denominator of the fault location function of each sampling interval by using the geometric progression theorem to obtain a fault location correction function. The time domain distance protection module is configured to calculate the fault location by using the fault location correction function when a power grid fault occurs, and perform corresponding protection actions. The fault location function in the fault location calculation module is: p = (c k+1 b k -c k b k+1 ) / (a k b k+1 -b k a k+1 ) wherein p is the distance from the fault point to the installation of the protection device, c k is the voltage at the installation of the protection device at time k, a k , b k is the time correlation coefficient value at time k, c k+1 is the voltage at the installation of the protection device at time k+1, a k+1 , b k+1 is the time correlation coefficient value at time k+1. The fault location correction function in the fault location calculation module is: wherein p is the distance from the fault point to the installation of the protection device, c k is the voltage at the installation of the protection device at time k, a k , b k is the time correlation coefficient value at time k, c k+1 is the voltage at the installation of the protection device at time k+1, a k+1 , b k+1 is the time correlation coefficient value at time k+1, and m is the sampling number.

6. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The computer program is loaded into the processor to implement the time domain distance protection method of the new energy sending-out line according to any one of claims 1-4.

7. A computer-readable storage medium storing a computer program, wherein the computer program comprises the following steps of: receiving a request for a resource from a client; determining whether the client is authorized to access the resource; and if the client is authorized to access the resource, providing the resource to the client. The computer program is executed by the processor to implement the time domain distance protection method of the new energy sending-out line according to any one of claims 1-4.

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