A new energy sending-out line differential protection action method, device and equipment

Abstract

The present application relates to the technical field of power system maintenance, and provides a new energy sending-out line differential protection action method, device and equipment, the method comprising: setting an incremental count value through electromagnetic transient simulation of line fault; setting a sampling point number, setting an integral upper limit value with the incremental count value, the sampling point number and an action time, sampling differential current data at time intervals in the line, adding the integral value in the counter to the incremental count value, the integral value of the current sampling point, and storing the integral value of the current sampling point in the counter, accumulating the integral value in the counter, and when the integral value of the sampling point reaches the integral upper limit value, executing differential protection action, so that the integral value reflects the accumulation of the differential current fluctuation from the start of sampling to the current time satisfying the protection criterion, reflecting the duration of a period of time with the multi-point state accumulation, and improving the reliability of the differential protection.

Description

Technical Field

[0001] This invention relates to the field of power system maintenance technology, and in particular to a method, device and equipment for differential protection of new energy transmission lines. Background Technology

[0002] In the new energy transmission system via flexible DC transmission, such as the Zhangbei wind power and Donghai offshore wind power transmission projects via flexible DC transmission, the fault characteristics are controlled by the control strategies of power electronic equipment such as new energy and flexible DC transmission, which is very different from the traditional AC power grid. In traditional protection strategies, the differential current of the line needs to be greater than the braking current or differential current threshold value for a certain period of time in order to trigger the protection action. However, during the fault period of the transmission line in this type of system, the fault current exhibits time-domain fluctuations and is difficult to remain greater than the braking current or differential current threshold value. This can lead to delayed operation or even failure of differential protection, reducing the reliability of the line differential protection. Summary of the Invention

[0003] This invention provides a differential protection operation method for new energy transmission lines, which solves the problem in the prior art where the current of new energy transmission lines has time-domain fluctuations and the fault circuit is difficult to continuously exceed the braking current or differential current threshold value, resulting in low reliability of differential protection.

[0004] The first aspect of this invention provides a method for differential protection operation of a new energy transmission line, comprising: Electromagnetic transient simulation of line faults is performed to obtain the duration for which the differential current first meets the differential protection criterion, thus obtaining the first duration; the duration for which the differential current first fails to meet the differential protection criterion is obtained, thus obtaining the second duration; an incremental count value is set, which is proportional to the ratio of the first duration to the second duration. Set the number of sampling points, and calculate the upper limit of integration based on the incremental count value, the number of sampling points, and the differential protection action time; The differential current in the sampling circuit is sampled according to the time interval corresponding to the number of sampling points. If the differential current meets the differential protection criterion, the integral value in the counter is added to the incremental count value to obtain the integral value of the current sampling point. If the integral value of the current sampling point is greater than or equal to the upper limit of the integral, the differential protection action is executed and the integral value in the counter is reset; otherwise, the integral value of the current sampling point is stored in the counter, and the differential protection criterion is satisfied for the next sampling point after the time interval.

[0005] Optionally, the calculation model for the incremental count value is as follows: A ≥ ceil [ k×(t2 / t1)max ] In the formula, A is the incremental count value, ceil means rounding up; k is the reliability coefficient, which is determined according to the actual operation requirements; (t2 / t1)max is the maximum value of the ratio of t2 to t1 under different operating conditions.

[0006] Optionally, the calculation model for the upper limit of the integral is as follows: U=A×N×T In the formula, U is the upper limit of integration, A is the incremental count value, N is the number of sampling points, and T is the differential protection action time.

[0007] Optionally, after sampling the differential current in the circuit according to the time interval corresponding to the number of sampling points, the method further includes: if the differential current does not meet the differential protection criterion, subtracting a preset value from the integral value in the counter to obtain the integral value of the current sampling point.

[0008] Optionally, after subtracting the preset value from the integral value in the counter, the method further includes: if the integral value of the current sampling point is less than 0, then resetting the integral value of the current sampling point to 0.

[0009] Optionally, before sampling the differential current in the circuit according to the time interval corresponding to the number of sampling points, the method further includes: determining whether the CT is not disconnected and whether the protection channel is normal; otherwise, blocking the differential protection and issuing an alarm.

[0010] The second aspect of this application provides a differential protection device for a new energy transmission line, comprising: The incremental count value setting module is used to perform electromagnetic transient simulation of line faults, obtain the duration for which the differential current first meets the differential protection criterion, and obtain the first duration; obtain the duration for which the differential current first fails to meet the differential protection criterion, and obtain the second duration; set the incremental count value, which is proportional to the ratio of the first duration to the second duration; The integral upper limit setting module is used to set the number of sampling points and calculate the integral upper limit based on the incremental count value, the number of sampling points, and the differential protection action time. The sampling point integral value calculation module is used to sample the differential current in the circuit according to the time interval corresponding to the number of sampling points. If the differential current meets the differential protection criterion, the integral value in the counter is added to the incremental count value to obtain the integral value of the current sampling point. The differential protection execution module is used to execute differential protection action and reset the integral value in the counter if the integral value of the current sampling point is greater than or equal to the upper limit of the integral value; otherwise, the integral value of the current sampling point is stored in the counter, and the differential protection criterion is satisfied for the next sampling point after the time interval.

[0011] Optionally, in the incremental count value setting module, the calculation model for the incremental count value is specifically as follows: A ≥ ceil [ k×(t2 / t1)max ] In the formula, A is the incremental count value, ceil means rounding up; k is the reliability coefficient, which is determined according to the actual operation requirements; (t2 / t1)max is the maximum value of the ratio of t2 to t1 under different operating conditions.

[0012] Optionally, in the integration upper limit setting module, the calculation model for the integration upper limit is specifically as follows: U=A×N×T In the formula, U is the upper limit of integration, A is the incremental count value, N is the number of sampling points, and T is the differential protection action time.

[0013] A third aspect of this application provides a differential protection device for a new energy transmission line, the device comprising a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the differential protection operation method for new energy transmission lines according to any one of the first aspects of the present invention, based on the instructions in the program code.

[0014] As can be seen from the above technical solutions, the present invention has the following advantages: By simulating the electromagnetic transients of a line fault, the duration for which the differential current first meets the differential protection criterion is obtained, resulting in a first duration; and the duration for which the differential current first fails to meet the differential protection criterion is obtained, resulting in a second duration, and an incremental count value is set. The number of sampling points is set, and the upper limit of integration is set using the incremental count value, the number of sampling points, and the action time. Differential current data is sampled in the line at time intervals corresponding to the number of sampling points. The integral value in the counter is added to the incremental count value to obtain the integral value of the current sampling point where the differential current meets the differential protection condition. By judging whether the differential current at the sampling point meets the differential protection action criterion, the integral value in the counter is accumulated, so that the integral value reflects the accumulation of differential current fluctuations meeting the protection criterion from the start of sampling to the current moment. The cumulative situation at multiple points reflects the duration over a period of time. When the integral value of the sampling point reaches the upper limit of integration, the differential protection action is executed, improving the reliability of the differential protection. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 The first flowchart of the differential protection operation method for new energy transmission lines; Figure 2 The second flowchart for the differential protection operation method of new energy transmission lines; Figure 3 The third flowchart for the differential protection operation method of new energy transmission lines; Figure 4 Diagram of differential protection device for new energy transmission lines. Detailed Implementation

[0017] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0018] This invention provides a differential protection operation method for new energy transmission lines, which solves the problem of low marketing efficiency caused by the difficulty in achieving precise marketing in the prior art.

[0019] Please see Figure 1 , Figure 1 This is the first flowchart of the differential protection operation method for new energy transmission lines provided in an embodiment of the present invention.

[0020] S100, perform electromagnetic transient simulation of line fault, obtain the duration of the first time the differential current meets the differential protection criterion, and obtain the first duration; obtain the duration of the first time the differential current does not meet the differential protection criterion, and obtain the second duration; set an incremental count value, which is proportional to the ratio of the first duration to the second duration; It should be noted that by considering combinations of different transition resistances, different fault types, and different flexible DC connection conditions, electromagnetic transient simulations are conducted on line faults in the new energy transmission line system to obtain the duration of differential current under each operating condition and calculate the duration for which the differential current meets the differential protection criteria. The duration for which the differential current first meets the differential protection criteria is the time between the first time the differential current meets the differential protection criteria and the first time it does not meet the differential protection criteria after meeting the criteria. The duration for which the differential current first does not meet the differential protection criteria is the time between the first time it does not meet the differential protection criteria after meeting the criteria and the second time it meets the differential protection criteria.

[0021] Current differential protection is specifically divided into phase differential protection and zero-sequence differential protection. The criteria for phase differential protection are as follows:

[0022] In the formula, I dif-Φ I represents the differential current of phase Φ, where Φ represents phases A, B, and C; res-Φ Let be the braking current of phase Φ; k is the braking current ratio coefficient; I H This is the differential current threshold value, which is specifically set by the power grid company.

[0023] The criteria for zero-sequence differential protection are as follows:

[0024] In the formula, I dif0 For zero-sequence differential current; I res0 I represents the braking current; k1 and k2 are the ratio coefficients of the zero-sequence braking current and the phase-by-phase braking current, respectively; H0 I is the threshold value for zero-sequence differential current. ’ H This is the phase current threshold value in zero-sequence differential operation, which is specifically set by the power grid company.

[0025] The increment value reflects the duration for which the differential protection criteria are met during fault current fluctuations. A larger increment value indicates a greater need for differential protection during a fluctuation. In line protection, differential current fluctuations have the greatest impact on the reliability of differential protection in the initial stage of meeting the criteria. Therefore, differential current fluctuations with relatively delayed time in electromagnetic transient simulation do not affect the setting of the increment count value.

[0026] S200, set the number of sampling points, and calculate the upper limit of integration based on the incremental count value, the number of sampling points, and the differential protection action time; It should be noted that the number of sampling points is specifically the number of times the line current is sampled per second, i.e., the sampling rate. For example, it can be set to sample 1200 times per second, i.e., the number of sampling points is set to 1200.

[0027] Differential protection is activated when the integral value reaches the upper limit. Therefore, the setting of the upper limit must consider both the speed and reliability of the protection. For the same time period, the more sampling points, the more integrals can be accumulated, resulting in a higher integral value. In practical conditions where the traditional strategy's action time is 1 second and the differential protection criterion duration is greater than 1 second, setting the sampling point count to 1000 and the incremental count to 2 allows for high-speed and high-reliability differential protection activation with an upper limit of 2000. As the number of sampling points or the upper limit increases, the corresponding upper limit also needs to increase. Similarly, as the differential protection action time of the traditional strategy increases, the upper limit also increases accordingly. Therefore, the upper limit is positively correlated with the incremental count, the number of sampling points, and the differential protection action time. In actual implementation, staff can also adjust the upper limit based on the specific needs of the line protection.

[0028] S300, sample the differential current in the circuit according to the time interval corresponding to the number of sampling points. If the differential current meets the differential protection criterion, add the integral value in the counter to the incremental count value to obtain the integral value of the current sampling point. It should be noted that when judging the first sampling point, the integral value in the counter is set to 0 or set to a preset value according to the actual situation of the line.

[0029] The differential current in the sampling circuit is sampled according to the time interval corresponding to the number of sampling points. Specifically, the interval time between each sampling point within the sampling time is calculated according to the number of sampling points. After each interval time, the differential current data in the circuit is sampled once, and the time corresponding to this sampling is a sampling point. When calculating the integral value of the current sampling point, the integral value in the counter is the integral value of the previous sampling point. After storing the integral value of the current sampling point in the counter, the integral value of the previous sampling point in the counter is replaced with the integral value of the current sampling point for calculation of the next sampling point.

[0030] In actual implementation, let the integral value of the previous sampling point t-1 be C(t-1), which is also the integral value in the counter. If the differential current data of the current sampling point t meets the differential protection action criterion, then the integral value of the current sampling point is C(t) = C(t-1) + A, where A is the incremental count value. C(t) is stored in the counter to replace C(t-1). The integral value C(t) in the counter is used to calculate the next sampling point t+1.

[0031] S400, if the integral value of the current sampling point is greater than or equal to the upper limit of the integral, then the differential protection action is executed and the integral value in the counter is reset; otherwise, the integral value of the current sampling point is stored in the counter, and the differential protection criterion is satisfied for the next sampling point after the time interval.

[0032] It should be noted that the integral value of the sampling point at the current moment reflects the accumulation of the differential current fluctuation from the start of sampling to the current moment, indicating whether the protection criteria are met. When the integral value is greater than or equal to the upper limit of the integral, the condition for executing differential protection in this scheme is met, the differential protection action output is reached, the counter does not need to continue storing the integral, and the integral value in the counter is reset to the initial preset value. If the integral value of the current sampling point is less than the upper limit of the integral, the circuit does not need to execute differential protection yet. Therefore, the integral value of the current sampling point is stored in the counter, and the process returns to step S300 to continue judging whether the differential current meets the differential protection criteria and calculating the integral value.

[0033] In this embodiment, through electromagnetic transient simulation of line faults, the duration for which the differential current first meets the differential protection criteria is obtained, resulting in a first duration, and the duration for which the differential current first fails to meet the differential protection criteria is obtained, resulting in a second duration. An incremental count value is set. The number of sampling points is set, and an integration upper limit value is set based on the incremental count value, the number of sampling points, and the action time. Differential current data is sampled in the line at time intervals corresponding to the number of sampling points. The integration value in the counter is added to the incremental count value to obtain the integration value of the current sampling point where the differential current meets the differential protection condition. The integration value of the current sampling point is stored in the counter. By judging whether the differential current at the sampling point meets the differential protection action criteria, the integration value in the counter is accumulated, so that the integration value reflects the accumulation of differential current fluctuations meeting the protection criteria from the start of sampling to the current moment. The accumulation of multiple states reflects the duration of a period of time. When the integration value of the sampling point reaches the integration upper limit value, the differential protection action is executed. This avoids the situation where the fault current fluctuations cause the differential protection criteria to fail to be met continuously, thus improving the reliability of differential protection.

[0034] The above is a detailed description of the first embodiment of the differential protection operation method for a new energy transmission line provided in this application. The following is a detailed description of the second embodiment of the differential protection operation method for a new energy transmission line provided in this application.

[0035] This embodiment further provides a specific implementation of step S100 in the differential protection operation method for new energy transmission lines. Please refer to [link to relevant documentation]. Figure 2 Step S100 specifically includes steps S101-S102, as detailed below: S101, perform electromagnetic transient simulation of line fault, obtain the duration of the first time the differential current meets the differential protection criterion, and obtain the first duration; and obtain the duration of the first time the differential current does not meet the differential protection criterion, and obtain the second duration. It should be noted that, by considering different transition resistances, different fault types, and different flexible DC connection conditions, electromagnetic transient simulations were conducted on line faults in the new energy grid-connected system to obtain the duration t1 of the first differential protection criterion being met, the duration t2 of the first differential protection criterion not being met, and the duration t3 of the second differential protection criterion being met under different operating conditions. In actual implementation, the obtained durations are divided into phase-by-phase differential and zero-sequence differential; please refer to Tables 1 and 2.

[0036]

[0037] Table 1. Duration of satisfaction and non-satisfaction of phase differential protection criteria during fault dynamic process.

[0038] Table 2 Duration of zero-sequence differential protection criteria being met or not met during fault dynamic processes

[0039] S102. Substitute the first duration and the second duration into the incremental count value calculation model, and set the incremental count value; It should be noted that the value of the incremental count A is determined by the characteristics of the line fault. To ensure that the differential protection outputs quickly, i.e., the integral is not zeroed when entering the t3 stage where the criterion is met for the second time, and considering a certain margin, the calculation model for the incremental count value is as follows: A ≥ ceil [ k×(t2 / t1)max ] In the formula, ceil represents rounding up; k is the reliability coefficient, which is determined according to the actual operation requirements; (t2 / t1)max is the maximum value of the ratio of t2 to t1 under each operating condition; it can be understood that, according to the characteristics of line faults, it is necessary to eliminate the impact of continuous failure to meet the differential protection criteria on the differential protection operation, but it cannot be completely eliminated. Therefore, the ratio of the duration of the first differential protection criterion being met to the duration of the first differential protection criterion not being met is used to calculate the incremental count value.

[0040] In this embodiment, for phase-separated differential protection, referring to Table 1, the value of (t2 / t1)max is 6.75, and the reliability k is 2. According to the calculation model of incremental count value, the incremental count value A1 of phase-separated differential protection is ≥14. The specific value can be selected according to actual needs. In this embodiment, A1 is 20. For zero-sequence differential protection, referring to Table 2, the value of (t2 / t1)max is 8, and the reliability k is 2. According to the calculation model of incremental count value, the incremental count value A2 of zero-sequence differential protection is ≥16. The specific value can be selected according to actual needs. In this embodiment, A2 is 20.

[0041] Furthermore, in a more specific embodiment, the aforementioned step S200, calculating the integral upper limit value based on the incremental count value, the number of sampling points, and the differential protection action time, specifically includes: substituting the incremental count value, the number of sampling points, and the differential protection action time into a preset integral upper limit value calculation model to obtain the integral upper limit value. The upper limit value calculation model is specifically as follows: U=A×N×T In the formula, U is the upper limit of integration, A is the incremental count value, N is the number of sampling points, and T is the differential protection action time; In this embodiment, for phase-sequence differential protection, since actual line protection is generally divided into two stages, Stage I and Stage II, Stage I protection has a higher criterion setting value and a shorter operating time, while Stage II protection has a lower setting value and a longer operating time, the upper limit of integration is also set to two. For example, if the number of sampling points is 1200, then N=1200. The calculation of the upper limit of integration for phase-sequence differential protection and zero-sequence differential protection is as follows: The operating time of the phase-separated differential protection stage I is 5ms, i.e., T1=0.005, and the upper limit of the integral value of stage I is U1=A1×N×T=20×1200×0.005=120; the operating time of the phase-separated differential protection stage II is 25ms, i.e., T2=0.005, and the upper limit of the integral value of stage II is U2=A1×N×T2=20×1200×0.025=600. For zero-sequence differential protection, the action time of zero-sequence differential protection is 100ms, i.e., T3=0.1. The upper limit of the integral of zero-sequence differential protection is U3=A2×N×T3=20×1200×0.1=2400.

[0042] In this embodiment, the incremental calculation value is calculated based on the line characteristics under different operating conditions and the duration of the differential protection criterion conditions being met or not. The incremental calculation value can fully reflect the influence of the sampling points of the line fault conditions. The upper limit of integration is calculated using the incremental calculation value, the number of sampling points, and the differential protection action time. This ensures that the upper limit of integration corresponds to the differential protection action time and is adjusted by the incremental calculation value and the number of sampling points. When the differential protection is activated, it can effectively protect the line and improve the reliability of the differential protection.

[0043] The above is a detailed description of the second embodiment of the differential protection operation method for a new energy transmission line provided in this application. The following is a detailed description of the third embodiment of the differential protection operation method for a new energy transmission line provided in this application.

[0044] This embodiment further provides a specific example of step S300 in the differential protection operation method for new energy transmission lines. Please refer to [link to specific example]. Figure 3 Step S300 specifically includes steps S301-S302, as detailed below: S301: Determine if the CT is not disconnected and the protection channel is normal. If not, lock the differential protection and issue an alarm. It should be noted that when the current transformer (CT) is disconnected or an abnormality occurs in the protection channel, the fault cannot be cleared during differential protection. Therefore, it is necessary to first lock out the differential protection and then issue an alarm to notify the personnel for further handling. For phase-by-phase differential protection, the fault is determined by whether a single-phase CT is disconnected, while for zero-sequence differential protection, the fault is determined by whether a three-phase CT is disconnected.

[0045] S302. Based on the time interval corresponding to the number of sampling points, sample the differential current in the circuit. If the differential current meets the differential protection criterion, add the integral value in the counter to the incremental count value; otherwise, subtract the preset value from the integral value in the counter to obtain the integral value of the current sampling point.

[0046] It should be noted that, in order to further reflect the situation of fluctuating fault current, for sampling points where the differential current does not meet the differential protection criteria, the integral value of the counter, i.e. the integral value of the previous sampling point, should be subtracted by a preset value. This preset value is set according to the actual differential protection situation to obtain the integral value of the current sampling point, so that the integral value can reflect the situation where the differential current does not meet the differential protection action criteria during fluctuation. In this embodiment, the preset value is set to 1; that is, if the differential current data of the current sampling point t does not meet the differential protection action criterion, then the integral value of the current sampling point C(t) = C(t-1)-1, where 1 is the preset value; if the differential current does not meet the differential protection criterion, after calculating the integral value of the current sampling point, we can directly return to step S301, because if the differential protection is not performed at the previous sampling point, the integral value of the current sampling point will not be greater than or equal to the upper limit of the integral after subtracting the preset value, so there is no need to enter step S400, thus improving the judgment efficiency; if the integral value of the current sampling point obtained is less than 0 after subtracting the preset value, then the integral value of the current sampling point is reset to 0 and stored in the counter.

[0047] Furthermore, in a more specific embodiment, in step S400, when the integral value is greater than or equal to the upper limit of the integral value, the differential protection exit action is executed. Compared with the traditional timing protection strategy, the differential protection exit can be executed more accurately.

[0048] Referring to Table 3, each sampling point in the phase-separated differential protection is judged according to the criteria of Stage I protection and Stage II protection respectively. Based on the number of sampling points of 1200, A1 and A2 are 20, the upper limit of integration of Stage I protection is U1=120, and the upper limit of integration of Stage II protection is U2=600. For the zero-sequence differential protection with the upper limit of integration U3=2400, taking working condition 2 as an example, if the traditional timing protection strategy is adopted, without considering the communication time at both ends and the power frequency phasor calculation time, Stage I needs at least 4.17+11.66+5=20.83ms to exit. If the criteria of Stage I are not met, the time periods t1 and t3 will not reach the operating time of Stage II, and at least 4.17+11.66+22.15+25=62.98ms is needed to exit, and it may even fail to exit, that is, the protection fails to operate. Under the differential protection operation method of this scheme, after time period t1, the integral value C(t1) = 20 × 1200 × 0.00417 = 100; after time period t2, the integral value C(t2) = 100 - 1 × 1200 × 0.01166 = 87 (the integral value is rounded down); after entering time period t3 where the criterion is met for the second time, it only needs to meet the criterion for another 21.37ms to exit. Without considering the communication time between the two ends and the power frequency phasor calculation time, a total of only 4.17 + 11.66 + 21.37 = 31.2ms is needed to exit, which improves the reliability of differential protection.

[0049]

[0050] Table 3 Comparison of action exit times for phase-separated differential operation using traditional strategy and integral counting.

[0051] Referring to Table 4, taking working condition 2 as an example, in zero-sequence differential protection, if the traditional timing protection strategy is adopted, without considering the communication duration at both ends and the power frequency phasor calculation time, the time periods t1 and t3 will not reach the zero-sequence protection action time. It will take at least 42.48+17.49+72.15+100=232.12ms to exit, and it may even fail to exit, i.e. the protection fails to operate. Under the differential protection operation method of this scheme, after time period t1, the integral value C(t1) = 20 × 1200 × 0.04248 = 1019; after time period t2, the integral value C(t2) = 1019 - 1 × 1200 × 0.01749 = 999 (the integral value is rounded down); after entering time period t3 where the criterion is met for the second time, it only needs to meet the criterion for another 58.35ms to exit. Without considering the communication time between the two ends and the power frequency phasor calculation time, a total of only 42.48 + 17.49 + 58.35 = 118.32ms is needed to exit, which improves the reliability of differential protection.

[0052]

[0053] Table 4 Comparison of action exit times for zero-sequence differential using traditional strategy and integral counting

[0054] In this embodiment, based on the condition that the differential current data at each sampling point meets the criteria, the integral value of the sampling point is incremented by an incremental count when the criteria are met, and subtracted by a preset value when the criteria are not met. This allows the integral value to reflect the cumulative impact of fluctuating differential current data over a period of time, enabling the integral value to more accurately reflect the line condition and increasing the reliability of the differential protection in this scheme.

[0055] The above is a detailed description of the third embodiment of a differential protection operation method for a new energy transmission line provided in this application. The following is a detailed description of a differential protection operation device for a new energy transmission line provided in the second aspect of this application.

[0056] Please see Figure 4 , Figure 4 This is a diagram of a differential protection device for a new energy transmission line. This embodiment provides a differential protection device for a new energy transmission line, including: The incremental count value setting module 10 is used to perform electromagnetic transient simulation of line faults, obtain the duration of the first time the differential current meets the differential protection criterion, and obtain the first duration; obtain the duration of the first time the differential current does not meet the differential protection criterion, and obtain the second duration; set the incremental count value, which is proportional to the ratio of the first duration to the second duration; The integral upper limit setting module 20 is used to set the number of sampling points and calculate the integral upper limit based on the incremental count value, the number of sampling points, and the differential protection action time. The sampling point integral value calculation module 30 is used to sample the differential current in the circuit according to the time interval corresponding to the number of sampling points. If the differential current meets the differential protection criterion, the integral value in the counter is added to the incremental count value to obtain the integral value of the current sampling point. The differential protection execution module 40 is used to execute differential protection action and reset the integral value in the counter if the integral value of the current sampling point is greater than or equal to the upper limit of the integral value; otherwise, it stores the integral value of the current sampling point in the counter and continues to judge the satisfaction of the differential protection criterion for the next sampling point after the time interval.

[0057] A third aspect of this application also provides a differential protection device for new energy transmission lines, including a processor and a memory: wherein the memory is used to store program code and transmit the program code to the processor; the processor is used to execute the differential protection method for new energy transmission lines described in the first aspect according to the instructions in the program code.

[0058] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the above-described apparatus and equipment can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0059] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between apparatuses or units through some interfaces, and may be electrical, mechanical, or other forms.

[0060] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0061] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0062] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0063] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A differential protection operation method for a new energy transmission line, characterized in that, include: Electromagnetic transient simulation of line faults is performed to obtain the duration during which the differential current first meets the differential protection criterion, thus obtaining the first duration. The duration during which the differential current first fails to meet the differential protection criterion is obtained, and the second duration is derived. Set an incremental count value, which is proportional to the ratio of the first duration to the second duration; Set the number of sampling points, and calculate the upper limit of integration based on the incremental count value, the number of sampling points, and the differential protection action time; The differential current in the sampling circuit is sampled according to the time interval corresponding to the number of sampling points. If the differential current meets the differential protection criterion, the integral value in the counter is added to the incremental count value to obtain the integral value of the current sampling point. If the integral value of the current sampling point is greater than or equal to the upper limit of the integral, the differential protection action is executed and the integral value in the counter is reset; otherwise, the integral value of the current sampling point is stored in the counter, and the differential protection criterion is checked again for the next sampling point after the time interval. The specific calculation model for the incremental count value is as follows: A ≥ ceil [ k×(t2 / t1)max ] In the formula, A is the incremental count value, ceil means rounding up; k is the reliability coefficient, which is determined according to the actual operation requirements; (t2 / t1)max is the maximum value of the ratio of t2 to t1 under different working conditions; The specific calculation model for the upper limit of the integral is as follows: U=A×N×T In the formula, U is the upper limit of integration, A is the incremental count value, N is the number of sampling points, and T is the differential protection action time.

2. The differential protection operation method for new energy transmission lines according to claim 1, characterized in that, After sampling the differential current in the circuit according to the time interval corresponding to the number of sampling points, the method further includes: if the differential current does not meet the differential protection criterion, subtracting the preset value from the integral value in the counter to obtain the integral value of the current sampling point.

3. The differential protection operation method for new energy transmission lines according to claim 2, characterized in that, The step of subtracting a preset value from the integral value in the counter further includes: if the integral value of the current sampling point is less than 0, then the integral value of the current sampling point is reset to 0.

4. The differential protection operation method for new energy transmission lines according to claim 1, characterized in that, Before sampling the differential current in the circuit according to the time interval corresponding to the number of sampling points, the process also includes: determining whether the CT is not disconnected and whether the protection channel is normal; otherwise, the differential protection is blocked and an alarm is issued.

5. A differential protection device for a new energy transmission line, characterized in that, include: The incremental count value setting module is used to perform electromagnetic transient simulation of line faults, obtain the duration of the differential current first meeting the differential protection criterion, and obtain the first duration. The duration during which the differential current first fails to meet the differential protection criterion is obtained, and the second duration is derived. Set an incremental count value, which is proportional to the ratio of the first duration to the second duration; The integral upper limit setting module is used to set the number of sampling points and calculate the integral upper limit based on the incremental count value, the number of sampling points, and the differential protection action time. The sampling point integral value calculation module is used to sample the differential current in the circuit according to the time interval corresponding to the number of sampling points. If the differential current meets the differential protection criterion, the integral value in the counter is added to the incremental count value to obtain the integral value of the current sampling point. The differential protection execution module is used to execute differential protection action and reset the integral value in the counter if the integral value of the current sampling point is greater than or equal to the upper limit of the integral value; otherwise, it stores the integral value of the current sampling point in the counter and continues to judge the satisfaction of the differential protection criterion for the next sampling point after the time interval. Specifically, in the incremental count value setting module, the calculation model for the incremental count value is as follows: A ≥ ceil [ k×(t2 / t1)max ] In the formula, A is the incremental count value, ceil means rounding up; k is the reliability coefficient, which is determined according to the actual operation requirements; (t2 / t1)max is the maximum value of the ratio of t2 to t1 under different working conditions; The calculation model for the upper limit of integration in the module is as follows: U=A×N×T In the formula, U is the upper limit of integration, A is the incremental count value, N is the number of sampling points, and T is the differential protection action time.

6. A differential protection device for a new energy transmission line, characterized in that, The device includes a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the differential protection action method for new energy transmission lines according to any one of claims 1-4, based on the instructions in the program code.

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