Distribution network current protection sensitivity analysis method and apparatus

Abstract

A distribution network current protection sensitivity analysis method and apparatus. The method comprises: acquiring, according to distribution network parameters, a first short-circuit current and a system short-circuit capacity when no distributed power supply is connected to a power system (S101); determining a fault short circuit ratio according to a relative relationship between a grid connection position of a distributed power supply in the power system, and a current measurement point position and a fault position (S102); when the distributed power supply uses an optimal positive sequence voltage support policy, calculating the phase of an output current of the distributed power supply according to a phase voltage of the power system, positive and negative sequence short-circuit impedance, line impedance, the magnitude of the output current of the distributed power supply, line impedance between buses, and a line impedance angle (S103); according to the first short-circuit current, the fault short circuit ratio, and the phase of the output current of the distributed power supply, determining a second short-circuit current when the distributed power supply is connected to the power system (S104); and performing evaluation of current protection sensitivity according to a current protection setting value and the second short-circuit current (S105). By means of the distribution network current protection sensitivity analysis method and apparatus, the magnitude of a short-circuit current can be calculated without an iterative calculation using a computer, thereby achieving the evaluation of current protection sensitivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power system relay protection, for example, a distribution network current protection sensitivity analysis method and apparatus. BACKGROUND

[0002] Under the overarching objectives of carbon peaking and carbon neutrality, the power industry must vigorously develop renewable energy sources to establish a new energy-dominated power system. Distributed generators have gained widespread adoption in distribution networks due to their advantages such as abundant resources, flexible site selection and an extensive application range. After a distributed generator is connected to a distribution network, the distribution network is switched from an original single-terminal power supply mode into a multi-terminal power supply mode, thereby changing a power flow direction and short-circuit current distribution and consequently affecting the sensitivity of a current protection apparatus.

[0003] To analyze the current protection sensitivity after the distributed generator is connected to the distribution network, the calculation of the magnitude of the short-circuit current is the critical determinant. Given the nonlinearity of a control strategy of the distributed generator, a numerical iterative solution emerges as the principal approach to the calculation of the short-circuit current in the distribution network including the distributed generator, but the numerical iterative solution requires the assistance of computer software. When a distribution network with a high proportion of a distributed generator fails, a current at the current protection apparatus is related to various factors such as the capacity of the distributed generator, the phase of an output current, a connection position, and a fault position, so it is difficult to quantitatively analyze the current protection sensitivity. 2023387063   21 Jul 2026 SUMMARY

[0004] The present application provides a distribution network current protection sensitivity analysis method and apparatus, which can intuitively acquire the factors affecting the magnitude of a short-circuit current or the current protection sensitivity in a distribution network including a distributed generator and calculate the magnitude of the short-circuit current, thereby achieving the analysis of current protection sensitivity.

[0005] The present application discloses a distribution network current protection sensitivity analysis method. The distribution network current protection sensitivity analysis method includes the following steps. A first short-circuit current and a system short-circuit capacity are acquired according to a distribution network parameter when a distributed generator is not connected to a power system; a fault short-circuit ratio is determined according to a relative position relationship between a grid-connected position of the distributed generator in the power system, a current measurement point position, and a fault position; in a case where the distributed generator adopts an optimal positive sequence voltage support strategy, the phase of an output current of the distributed generator is calculated according to a phase voltage of the power system, positive and negative sequence short-circuit impedance, line impedance, the output current of the distributed generator, line impedance between buses, and a line impedance angle; a second short-circuit current is determined according to the first short-circuit current, the fault short-circuit ratio, and the phase of the output current of the distributed generator when the distributed generator is connected to the power system; and current protection sensitivity analysis is performed according to a current protection setting value and the second short-circuit current.

[0006] The present application discloses a distribution network current protection sensitivity analysis apparatus. The apparatus includes: a current and capacity acquisition unit which is configured to acquire a first short-circuit current and a system short-circuit capacity according to a distribution network parameter when a distributed generator is not connected to a power system; a fault short-circuit ratio determination unit which is configured to determine a fault 2023387063   21 Jul 2026 short-circuit ratio according to a relative position relationship between a grid-connected position of the distributed generator in the power system, a current measurement point position, and a fault position; a phase determination unit which is configured to, in a case where the distributed generator adopts an optimal positive sequence voltage support strategy, calculate a phase of an output current of the distributed generator according to a phase voltage of the power system, positive and negative sequence short-circuit impedance, line impedance, the output current of the distributed generator, line impedance between buses, and a line impedance angle; a short-circuit current determination unit which is configured to determine a second short-circuit current according to the first short-circuit current, the fault short-circuit ratio, and the phase of the output current of the distributed generator when the distributed generator is connected to the power system; and a sensitivity analysis unit which is configured to perform current protection sensitivity analysis according to a current protection setting value and the second short-circuit current.

[0007] The present application discloses a computer device. The computer device includes a memory, a processor, and a computer program stored on the memory and executable on the processor, where when executing the program, the processor performs the method described above.

[0008] The present application discloses a computer-readable medium storing a computer program, where the program, when executed by a processor, causes the processor to perform the method described above. [0008 ] The present application discloses a distribution network current protection sensitivity analysis method, comprising: according to a distribution network parameter, acquiring a first short-circuit current and a system short-circuit capacity in response to a distributed generator being not connected to a power system; determining a fault short-circuit ratio according to a relative position relationship between a grid-connected position of the distributed generator in the power system, a current measurement point position, and a fault position; in response to the distributed generator adopting an optimal positive sequence voltage support 2023387063   21 Jul 2026 strategy, calculating a phase of an output current of the distributed generator according to a phase voltage of the power system, positive and negative sequence short-circuit impedance, line impedance, the output current of the distributed generator, line impedance between buses, and a line impedance angle; according to the first short-circuit current, the fault short-circuit ratio, and the phase of the output current of the distributed generator, determining a second short-circuit current in response to the distributed generator being connected to the power system; and performing current protection sensitivity analysis according to a current protection setting value and the second short-circuit current; wherein performing the current protection sensitivity analysis according to the current protection setting value and the second short-circuit current comprises: determining a sensitivity coefficient according to the second short-circuit current and the current protection setting value; wherein the sensitivity coefficient is a ratio of the second short-circuit current to the current protection setting value; and measuring a current protection sensitivity by using the sensitivity coefficient. [0008 ] The present application discloses a distribution network current protection sensitivity analysis apparatus, comprising: a current and capacity acquisition unit configured to acquire a first short-circuit current and a system short-circuit capacity according to a distribution network parameter in response to a distributed generator being not connected to a power system; a fault short-circuit ratio determination unit configured to determine a fault short-circuit ratio according to a relative position relationship between a grid-connected position of the distributed generator in the power system, a current measurement point position, and a fault position; a phase determination unit configured to, in response to the distributed generator adopting an optimal positive sequence voltage support strategy, calculate a phase of an output current of the distributed generator according to a phase voltage of the power system, positive and negative sequence short-circuit impedance, line impedance, the output current of the distributed generator, line impedance between buses, and a line impedance angle; a short-circuit current determination unit configured to, according to the first short-circuit current, the fault short-circuit ratio, and the phase of the output current of the distributed generator, determine a second short-circuit current in response to the distributed generator being connected to the power system; and a sensitivity analysis unit configured to perform current protection sensitivity analysis according to a current protection setting value and the second short-circuit current; 2023387063   21 Jul 2026 wherein the sensitivity analysis unit is configured to: determine a sensitivity coefficient according to the second short-circuit current and the current protection setting value; wherein the sensitivity coefficient is a ratio of the second short-circuit current to the current protection setting value; and measure a current protection sensitivity by using the sensitivity coefficient. BRIEF DESCRIPTION OF DRAWINGS

[0009] The drawings used in the description of embodiments or the description of the related art are briefly described below. The drawings described hereinafter illustrate part of the embodiments of the present application, and those of ordinary skill in the art may obtain other drawings based on the drawings described hereinafter on the premise that no creative work is done.

[0010] FIG. 1 is a flowchart of a distribution network current protection sensitivity analysis 2023387063  24 Jun 2025 method according to an embodiment of the present application;

[0011] FIG. 2 is a flowchart of a method for acquiring, according to a distribution network parameter, a first short-circuit current and a system short-circuit capacity when a distributed generator is not connected to a power system according to an embodiment of the present application;

[0012] FIG. 3 is a flowchart of a method for calculating a B-phase short-circuit current and a C-phase short-circuit current according to a phase voltage of the power system and short-circuit loop impedance according to an embodiment of the present application;

[0013] FIG. 4 is a schematic diagram of the line of a distribution network including distributed generators according to an embodiment of the present application;

[0014] FIG. 5 is a schematic diagram of a composite sequence network according to an embodiment of the present application;

[0015] FIG. 6 is a structure diagram of a distribution network current protection sensitivity analysis apparatus according to an embodiment of the present application;

[0016] FIG. 7 is a structure diagram of a current and capacity acquisition unit according to an embodiment of the present application;

[0017] FIG. 8 is a structure diagram of a B- and C-phase short-circuit current determination module according to an embodiment of the present application;

[0018] FIG. 9 is a structure diagram of a phase determination unit according to an embodiment of the present application;

[0019] FIG. 10 is a structure diagram of a short-circuit current determination unit according to an embodiment of the present application; and

[0020] FIG. 11 is a structure diagram of a distribution network including distributed generators according to an embodiment of the present application. 2023387063  24 Jun 2025 DETAILED DESCRIPTION

[0021] The solutions in the embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application. The described embodiments are merely part of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without any creative efforts are within the scope of the present application.

[0022] FIG. 1 is a flowchart of a distribution network current protection sensitivity analysis method according to an embodiment of the present application. As shown in FIG. 1, the distribution network current protection sensitivity analysis method includes steps S101 to S105.

[0023] In S101, a first short-circuit current and a system short-circuit capacity are acquired according to a distribution network parameter when a distributed generator (for example, an inverter-interfaced distributed generator (IIDG)) is not connected to a power system.

[0024] It is to be noted that the distribution network parameter may include a phase voltage of the power system and short-circuit loop impedance.

[0025] When the distributed generator is not connected to the power system, the first short-circuit current includes a three-phase short-circuit current, a B-phase short-circuit current, and a C-phase short-circuit current.

[0026] In S102, a fault short-circuit ratio is determined according to a relative position relationship between a grid-connected position of the distributed generator in the power system, a current measurement point position, and a fault position.

[0027] Three fault short-circuit ratios are defined in consideration of the distribution of the current measurement point position, the fault position, and the grid-connected position of the distributed generator, and the calculation methods thereof are given. When the system short-circuit capacity and rated capacities of the distributed generator at corresponding positions are known, the three fault short-circuit ratios may be obtained according to the calculation methods, respectively. 2023387063  24 Jun 2025

[0028] In S103, when the distributed generator adopts an optimal positive sequence voltage support strategy, the phase of an output current of the distributed generator is calculated according to a phase voltage of the power system, positive and negative sequence short-circuit impedance, line impedance, the output current of the distributed generator, line impedance between buses, and a line impedance angle.

[0029] When the distributed generator adopts the optimal voltage support strategy, the phase of the output current of the distributed generator is only related to the line impedance angle and the phase of a grid-connected positive sequence voltage.

[0030] In S104, a second short-circuit current is determined according to the first short-circuit current, the fault short-circuit ratio, and the phase of the output current of the distributed generator when the distributed generator is connected to the power system.

[0031] In S105, current protection sensitivity analysis is performed according to a current protection setting value and the second short-circuit current.

[0032] Through the method shown in FIG. 1, in the present application, the factors affecting the magnitude of a short-circuit current or the current protection sensitivity in a distribution network including a distributed generator can be intuitively acquired. In the present application, the magnitude of the short-circuit current can be calculated by using a short-circuit current calculation method associated with the fault short-circuit ratio when the distributed generator is connected to the power system, instead of using iterative calculation requiring the assistance of a computer, thereby achieving the analysis of current protection sensitivity.In an embodiment, as shown in FIG. 2, the step where the first short-circuit current and the system short-circuit capacity when the distributed generator is not connected to the power system are acquired according to the distribution network parameter includes steps S201 to S203. (3)

[0034] In S201, a three-phase short-circuit current / ^0 is calculated according to a phase voltage of the power system and short-circuit loop impedance. (3)

[0035] The three-phase short-circuit current / ^0 is calculated when the distributed generator 2023387063  24 Jun 2025 is not connected using the following formula: ■ I(3) = 2½                 n) 1 kO     Zl                       (1)

[0036] Es is the system phase voltage, and Zz is the short-circuit loop impedance.In S202, a B-phase short-circuit current and a C-phase short-circuit current are calculated according to the phase voltage of the power system and the short-circuit loop impedance.

[0038] In an embodiment, as shown in FIG. 3, S202 includes steps S301 to S302.

[0039] In S301, a positive sequence current Zk(1)0 is calculated according to the phase voltage of the power system and the short-circuit loop impedance: ■ 1‘^“z^         (2)

[0040] Zr(1) is positive sequence short-circuit impedance, and ZX(2) is negative sequence short-circuit impedance.

[0041] In S302, a first B-phase short-circuit current and a first C-phase short-circuit current are calculated according to the positive sequence current. (2)

[0042] The first B-phase short-circuit current ZkB0 and the first C-phase short-circuit current (2) IkcO are calculated when the distributed generator is not connected using the following formulas respectively: iSo = -j^3iKti)«                (3) IKO = / 734(1)0               (4).

[0043] j is an imaginary unit, and multiplying a complex number by j is equivalent to rotating the complex number 90° counterclockwise.

[0044] In S203, the system short-circuit capacity is calculated according to the three-phase short-circuit current and a normal operating voltage at a short circuit. 2023387063  24 Jun 2025

[0045] The system short-circuit capacity Sac is calculated using the following formula: 5ac =                          (5).

[0046] UN is the normal operating voltage at the short circuit and generally takes a value of an average rated voltage.

[0047] In an embodiment, S102 includes the following step: the fault short-circuit ratio is determined according to the system short-circuit capacity, a rated capacity of the distributed generator corresponding to the relative position relationship, a rated output current of the distributed generator corresponding to the relative position relationship, a first three-phase short-circuit current, and the positive sequence current.

[0048] On the basis of a short-circuit ratio (SCR), three fault short-circuit ratios are defined in consideration of the distribution of the current measurement point position, the fault position, and the grid-connected position of the distributed generator, which are a first fault short-circuit ratio SCR11, a second fault short-circuit ratio SCR12, and a third fault short-circuit ratio SCR2, respectively.

[0049] If the grid-connected position is located before the current measurement point position and the fault position, the fault short-circuit ratio is the first fault short-circuit ratio SCR11: 11 = $ac pN.ll It(3)|          2l / (2) I ffeo |    = zffe(l)o| |jpV.N.ll|    ^PV.N.ld (6).

[0050] PN.n is the rated capacity of the distributed generator corresponding to the first fault short-circuit ratio at the grid-connected position, and fp^.N.n is the rated output current of the distributed generator at the grid-connected position.

[0051] If the grid-connected position is located before the fault position and after the current measurement point position, the fault short-circuit ratio is the second fault short-circuit ratio SCR12: 12 = ^ac PN.l2 I; (3)1          2l / (2) I ffeo | = z|Jfe(l)o| hpV.N.l2|    hpV.N.l2| (7). 2023387063  24 Jun 2025

[0052] Pm.12 is the rated capacity of the distributed generator corresponding to the second fault short-circuit ratio at the grid-connected position, and 7p^.w.12 is the rated output current of the distributed generator at the grid-connected position.

[0053] If the grid connection position is located after the current measurement point position and the fault position, the fault short-circuit ratio is the third fault short-circuit ratio SCR2: 2= $ac PN,2 1 / (3)|        2l / (2) I ffeo | = 2|Jfe(i)o| |tPV.N.2|     hPV.N.2| (8).

[0054] Pn.2 is the rated capacity of the distributed generator corresponding to the third fault short-circuit ratio at the grid-connected position, and 7p^.w.2 is the rated output current of the distributed generator at the grid-connected position.

[0055] In an embodiment, in S103, when the distributed generator adopts the optimal positive sequence voltage support strategy, the phase of the output current of the distributed generator is only related to the line impedance angle and the phase of the grid-connected positive sequence voltage, and the phase of the output current of the distributed generator may be calculated according to the phase of a grid-connected bus voltage of the distributed generator and the line impedance angle: 0 = ^u(i) — Sz                 (9).

[0056] is the phase of the output current of the distributed generator, 0^) is the phase of the grid-connected bus voltage of the distributed generator, and 6Z is the line impedance angle.

[0057] As can be seen from the above analysis, the key to determining the phase of the output current of the distributed generator is to determine the phase of the grid-connected bus voltage (the positive sequence voltage at the grid-connected position) of the distributed generator at the grid-connected position. Assuming there are n grid-connected positions of the distributed generator, equations for the positive sequence voltages of multiple distributed generators at these grid-connected positions in a composite sequence network are formulated. By separating the real and imaginary parts of the equations, 2n equations are obtained. The unknowns are the 2023387063  24 Jun 2025 magnitudes and the phases of the positive sequence voltages at the grid-connected positions, that is, a total of 2n unknowns. The phases of the positive sequence voltages at the grid-connected positions are yielded by solving these equations, and then the phases of the output currents of the distributed generator are obtained.

[0058] FIG. 4 is a schematic diagram of the line of a distribution network including distributed generators, and FIG. 5 is a schematic diagram of a composite sequence network. As shown in FIGS. 4 and 5, taking the fault at f as an example, the equations for the positive sequence voltages of the distributed generators at the grid-connected positions N, T, and P are formulated below. The phases of the positive sequence voltages at the grid-connected positions may be yielded by solving these equations: ■ ■ ^W(l) = {zSs+Zm-1 + ^Pv0 (¾1) + ^-f^ + 4^(^(1) + ZT-f) + 4^3^(1)      (10) ■ ■ ^T(l) = (Z+z^^ + ^1 + ^2) (Z^(1) + ZT-f) + 4^(1) ■ ■ ^(1) = (^^ + ^1 + ^2 + 4v3) ^(1) (11) (12).

[0059] The positive sequence impedance is equal to the negative sequence impedance. / ^(1) represents the positive sequence impedance; / X-Y represents the impedance of the line connecting the bus X and the bus Y, where X and Y represent M, N, T, and P in FIGS. 4 and 5; • * • Zs represents the internal impedance of the generator in the power system; / pv1, / pv2, and / pv3 are the output currents of three distributed generators shown in FIG. 5, respectively.

[0060] The equations for the positive sequence voltages of the grid-connection buses of the distributed generators in the composite sequence network are formulated by using the above method, and the phases of the output currents of the distributed generators may be obtained by solving these equations.

[0061] In an embodiment, the second short-circuit current includes a second three-phase • (3)                                                                 ■ (2) short-circuit current ffc , a second B-phase short-circuit current IkB , and a second C-phase 2023387063  24 Jun 2025 short-circuit current ikc .

[0062] S104 includes steps S104A to S104C. In S104A, the second three-phase short-circuit • (3) current 4 is determined according to the first three-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, and the phase of the output current of the distributed generator. ()

[0063] The expression of the second three-phase short-circuit current 4 is as follows: i . / = ( 1 I i...—. -1-^,,-. ■'■ U3           (13). \        oCnu             jCu^2       / ()

[0064] In S104B, the second B-phase short-circuit current 4B is determined according to the first B-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, the third fault short-circuit ratio, and the phase of the output current of the distributed generator. • (2)

[0065] Specifically, the expression of the second B-phase short-circuit current lkB is as follows: 4(R2) = [(1 + ^-^e7^ — k-*1-¢,7^2) + y-LC*1-^ + -^7¾)]7® KB     LV 11 SCR^          12 scr12 J J 73 \scr12         scr2     j\ kB (14). ()

[0066] In S104C, the second C-phase short-circuit current 4C is determined according to the first C-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, the third fault short-circuit ratio, and the phase of the output current of the distributed generator. ()

[0067] The expression of the second C-phase short-circuit current 4C is as follows: j® = [(1 +k' J^-e-u — / f -^-^12) - / -^(-^e7012 + -^^)1 4|)    (15). *c |A 11 scr11           12 scr12      ) J 73 \sc 12 sc 2     J J kC0 v 7 2023387063  24 Jun 2025

[0068] In the above expressions, K1± = Zs+Z1 p11, k = Zp12 r, 0 is the difference ^^d)               Z^(i) between the phase of the output current of the distributed generator and the phase of a current flowing through the fault line when the distributed generator is not connected if the grid-connected position is located before the fault position and the current measurement point position, 012 is the difference between the phase of the output current of the distributed generator and the phase of the current flowing through the fault line when the distributed generator is not connected if the grid-connected position is located before the fault position and after the current measurement point position, and 02 is the difference between the phase of the output current of the distributed generator and the phase of the current flowing through the fault line when the distributed generator is not connected if the grid connection position is located after the current measurement point position and the fault position; k1 is a per-unit value of the output current of the distributed generator (with the rated current of the distributed generator as a reference); the rotation operator e^e = cos 6 + j sin 6, indicating that multiplying any complex number by e^e is equivalent to rotating the complex number counterclockwise by an angle of 0; j is the imaginary unit, and multiplying a complex number by j is equivalent to rotating the complex number 90° counterclockwise.

[0069] For a line with a line parameter, a fault type, a fault position, and a connected position and capacity of the distributed generator known, the short-circuit current of the distribution network including the distributed generators may be obtained according to the formulas (13), (14), and (15) on the basis of the short-circuit current of the distribution network without the distributed generator determined in S101, the magnitude of the fault short-circuit ratio determined in S102, and the phase of the output current of the distributed generator determined in S103.

[0070] In S105, the current protection sensitivity is measured by the sensitivity coefficient Ksen • The sensitivity coefficient is the ratio of the short-circuit current to the protection setting value when a two-phase short-circuit occurs at the end of the line: 2023387063  24 Jun 2025 sen r (2) lu het (16).

[0071] Seet is the current protection setting value.

[0072] Therefore, the current protection sensitivity may be analyzed according to the conventional current protection setting value and the magnitude of the short-circuit current when the distributed generator is connected to the distribution network.

[0073] The embodiments of the present application further provide a distribution network current protection sensitivity analysis apparatus. The distribution network current protection sensitivity analysis apparatus may be used for performing the method described in the above embodiments, as described in the following embodiments. Since the principle of solving the problem of the distribution network current protection sensitivity analysis apparatus is similar to the principle of the distribution network current protection sensitivity analysis method, for the implementation of the distribution network current protection sensitivity analysis apparatus, reference may be made to the implementation of the distribution network current protection sensitivity analysis method, and the details are not repeated herein. As used below, the term "unit" or "module" may be software, hardware, or a combination thereof capable of implementing predetermined functions. The system described in the following embodiments is implemented by software, but implementation by hardware or by a combination of software and hardware is also feasible and conceived.

[0074] FIG. 6 is a structure diagram of a distribution network current protection sensitivity analysis apparatus according to an embodiment of the present application. As shown in FIG. 6, the distribution network current protection sensitivity analysis apparatus includes a current and capacity acquisition unit 601, a fault short-circuit ratio determination unit 602, a phase determination unit 603, a short-circuit current determination unit 604, and a sensitivity analysis unit 605.

[0075] The current and capacity acquisition unit 601 is configured to acquire, according to a distribution network parameter, a first short-circuit current and a system short-circuit capacity 2023387063  24 Jun 2025 when a distributed generator is not connected to a power system. The fault short-circuit ratio determination unit 602 is configured to determine a fault short-circuit ratio according to a relative position relationship between a grid-connected position of the distributed generator in the power system, a current measurement point position, and a fault position. The phase determination unit 603 is configured to, when the distributed generator adopts an optimal positive sequence voltage support strategy, calculate the phase of an output current of the distributed generator according to a phase voltage of the power system, positive and negative sequence short-circuit impedance, line impedance, the output current of the distributed generator, line impedance between buses, and a line impedance angle. The short-circuit current determination unit 604 is configured to determine, according to the first short-circuit current, the fault short-circuit ratio, and the phase of the output current of the distributed generator, a second short-circuit current when the distributed generator is connected to the power system. The sensitivity analysis unit 605 is configured to perform current protection sensitivity analysis according to a current protection setting value and the second short-circuit current.

[0076] In an embodiment, as shown in FIG. 7, the distribution network parameter includes a phase voltage of the power system and short-circuit loop impedance, and the first short-circuit current includes a first three-phase short-circuit current, a first B-phase short-circuit current, and a first C-phase short-circuit current. The current and capacity acquisition unit 601 includes a first three-phase short-circuit current calculation module 701, a B- and C-phase short-circuit current determination module 702, and a system short-circuit capacity determination module 703. The first three-phase short-circuit current calculation module 701 is configured to calculate the first three-phase short-circuit current according to the phase voltage of the power system and the short-circuit loop impedance. The B- and C-phase short-circuit current determination module 702 is configured to calculate the first B-phase short-circuit current and the first C-phase short-circuit current according to the phase voltage of the power system and the short-circuit loop impedance. The system short-circuit capacity determination module 703 is configured to calculate the system short-circuit capacity according to the first three-phase short-circuit current and a normal operating voltage at a short circuit. 2023387063  24 Jun 2025

[0077] In an embodiment, as shown in FIG. 8, the B- and C-phase short-circuit current determination module 702 includes a positive sequence current determination sub-module 801 and a B- and C-phase short-circuit current calculation module 802. The positive sequence current determination sub-module 801 is configured to calculate a positive sequence current according to the phase voltage of the power system and the short-circuit loop impedance. The B- and C-phase short-circuit current calculation module 802 is configured to calculate the first B-phase short-circuit current and the first C-phase short-circuit current according to the positive sequence current.

[0078] In an embodiment, the fault short-circuit ratio determination unit 602 is configured to determine the fault short-circuit ratio according to the system short-circuit capacity, a rated capacity of the distributed generator corresponding to the relative position relationship, a rated output current of the distributed generator corresponding to the relative position relationship, the first three-phase short-circuit current, and the positive sequence current.

[0079] In an embodiment, the fault short-circuit ratio includes: a first fault short-circuit ratio if the grid-connected position is located before the current measurement point position and the fault position; a second fault short-circuit ratio if the grid-connected position is located before the fault position and after the current measurement point position; and a third fault short-circuit ratio if the grid-connected position is located after the current measurement point position and the fault position.

[0080] In an embodiment, as shown in FIG. 9, the phase determination unit 603 includes a first phase calculation module 901 and a second phase calculation module 902. The first phase calculation module 901 is configured to calculate the phase of a grid-connected bus voltage of the distributed generator according to the phase voltage of the power system, the positive and negative sequence short-circuit impedance, the line impedance, the output current of the distributed generator, and the line impedance between buses. The second phase calculation module 902 is configured to calculate the phase of the output current of the distributed generator according to the phase of the grid-connected bus voltage of the distributed generator 2023387063  24 Jun 2025 and the line impedance angle.

[0081] In an embodiment, as shown in FIG. 10, the short-circuit current determination unit 604 includes a three-phase short-circuit current determination module 1001, a B-phase short-circuit current determination module 1002, and a C-phase short-circuit current determination module 1003. The three-phase short-circuit current determination module 1001 is configured to determine the second three-phase short-circuit current according to the first three-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, and the phase of the output current of the distributed generator. The B-phase short-circuit current determination module 1002 is configured to determine the second B-phase short-circuit current according to the first B-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, the third fault short-circuit ratio, and the phase of the output current of the distributed generator. The C-phase short-circuit current determination module 1003 is configured to determine the second C-phase short-circuit current according to the first C-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, the third fault short-circuit ratio, and the phase of the output current of the distributed generator.

[0082] In an embodiment, the sensitivity analysis unit 605 is configured to determine a sensitivity coefficient according to the second short-circuit current and the current protection setting value.

[0083] The distribution network current protection sensitivity analysis method of the present application is described below through the following embodiments. The voltage level of the distribution network is 10 kV, the internal impedance Zs is equal to j7 Q, and the line parameter is (0.27 + j0.391) Q / km. The length of each section of the line is shown in FIG. 11. The capacities of the distributed generators 1 to 4 are 4 MVA, 2 MVA, 1 MVA, and 2 MVA, respectively. The sensitivity of Protection 2 and Protection 3 is analyzed, and the setting values of instantaneous current quick-break protection and time-limited current quick-break protection of Protection 2 and Protection 3 are shown in Table 1. Table 1 Current protection setting value 2023387063  24 Jun 2025 Protection Type Protection serial number Protection 2 Protection 3 Instantaneous current quick-break protection (Section I) 365 A 295 A Time-limited current quick-break protection (Section II) 197 A 164 A

[0084] When a three-phase short-circuit and a BC two-phase short-circuit occur at the ends of the lines protected by Protection 2 and Protection 3, the currents flowing through the protections are calculated by using the method of the present application, and the sensitivity coefficients of the current protection sections II are also calculated. The results calculated based on the fault short-circuit ratios of the present application are compared with the computer iterative results, as shown in Table 2. With manual calculation errors neglected, the accuracy of the method for analyzing current protection sensitivity based on the fault short-circuit ratio index approaches almost 100%. Table 2 Comparison between manual calculation results obtained based on the fault short-circuit ratio index and iterative calculation results Value to be calculated i (3) / kA / ® / kA Zd 1® / kA i (3) / kA I ®ZkA jd 1® / kA Section II sensitivity coefficient of Protection 2 Section II sensitivity coefficient of Protection 3 Manual calculation result 0.2422 z - 64.519 0.2449 z - 80.839 0.4543 z - 13.596 0.5616 z - 59.104 0.4634 z - 129.42 0.4875 z34.873° 2.306 2.973 Iterative result 0.2421 z - 64.515 0.2427 z - 80.406 0.4555 z - 13.313 0.5612 z - 59.109 0.4625 z - 129.18 0.4873 z35.125° 2.312 2.971 2023387063  24 Jun 2025

[0085] With the inspiration drawn from the good application effect of the short-circuit ratio in power systems and from the perspective of the relative position relationship between the grid-connected position of the distributed generator, the current measurement point position, and the fault position, the present application proposes a method for elevating distribution network current protection sensitivity based on the fault short-circuit ratio index. The factors affecting the magnitude of a short-circuit current or the current protection sensitivity in a distribution network including a distributed generator can be intuitively acquired based on the fault short-circuit ratio index, and the factors affecting the current protection sensitivity include the capacity of the distributed generator, the phase of the short-circuit current, and the relative position relationship between the grid-connected position of the distributed generator, the current measurement point position, and the fault position. The magnitude of the short-circuit current can be calculated by using a short-circuit current calculation method associated with the fault short-circuit ratio when the distributed generator is connected to the power system, instead of using iterative calculation requiring the assistance of a computer, thereby achieving the analysis of current protection sensitivity.

[0086] For ease of description, the above apparatus is described by dividing the apparatus into various units in terms of functions. Of course, the functions of various units may be implemented in the same software and / or hardware or more software and / or hardware during the implementation of the present application. The present application has been described with reference to flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It is to be understood that each flow and / or block in the flowcharts and / or the block diagrams and a combination of the flows and / or blocks in the flowcharts and / or the block diagrams may be implemented by computer program instructions. These computer program instructions may be provided for a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to produce a machine so that the instructions to be executed via the processor of the computer or other programmable data processing devices produce a means for implementing the functions specified in one or 2023387063  24 Jun 2025 more of the flows in the flowcharts and / or one or more of the blocks in the block diagrams.

[0087] These computer program instructions may also be stored in a computer-readable memory which can direct the computer or other programmable data processing devices to operate in a particular manner so that the instructions stored in the computer-readable memory produce a manufactured product including an instructing means. The instructing means implements the functions specified in one or more of the flows in the flowcharts and / or one or more of the blocks in the block diagrams.

[0088] These computer program instructions may also be loaded onto the computer or other programmable data processing devices to cause a series of operational steps to be executed on the computer or other programmable devices to produce computer-implemented processes so that the instructions executed on the computer or other programmable devices provide steps for implementing the functions specified in one or more of the flows in the flowcharts and / or one or more of the blocks in the block diagrams.

[0089] It is to be further noted that the term "comprising", "including" or any other variant thereof is intended to encompass a non-exclusive inclusion so that a process, method, article, or device that includes a series of elements not only includes the expressly listed elements but may also include other elements that are not expressly listed or are inherent to such process, method, article, or device. In the absence of more restrictions, the elements defined by the statement "including a ..." do not exclude the presence of additional identical elements in the process, method, article, or device that includes the elements.

[0090] It is to be understood by those skilled in the art that embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may be embodied in the form of a hardware embodiment, a software embodiment, or a combination of hardware and software embodiments. The present application may be embodied in the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, a compact disc read-only memory (CD-ROM), an optical memory, and the like) which include computer-usable program codes. 2023387063  24 Jun 2025

[0091] The present application may be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, and the like that execute specific tasks or implement specific abstract data types. The present application may also be practiced in distributed computing embodiments in which tasks are executed by remote processing devices connected through a communication network. In the distributed computing environments, the program modules may be located in local and remote computer storage media, including storage devices.

[0092] The various embodiments in the specification are described in a progressive manner. The same or similar parts in the various embodiments are referred to each other. Each embodiment is emphasized on differences from other embodiments. As for the system embodiments, since they are substantially similar to the method embodiments, the description of the device embodiments is relatively simple, and for a related part, reference may be made to the description of the related part in the method embodiments.

Claims

1. A distribution network current protection sensitivity analysis method, comprising:according to a distribution network parameter, acquiring a first short-circuit current and a system short-circuit capacity in response to a distributed generator being not connected to a power system;determining a fault short-circuit ratio according to a relative position relationship between a grid-connected position of the distributed generator in the power system, a current measurement point position, and a fault position;in response to the distributed generator adopting an optimal positive sequence voltage support strategy, calculating a phase of an output current of the distributed generator according to a phase voltage of the power system, positive and negative sequence short-circuit impedance, line impedance, the output current of the distributed generator, line impedance between buses, and a line impedance angle;according to the first short-circuit current, the fault short-circuit ratio, and the phase of the output current of the distributed generator, determining a second short-circuit current in response to the distributed generator being connected to the power system; andperforming current protection sensitivity analysis according to a current protection setting value and the second short-circuit current;wherein performing the current protection sensitivity analysis according to the current protection setting value and the second short-circuit current comprises:determining a sensitivity coefficient according to the second short-circuit current and the current protection setting value; wherein the sensitivity coefficient is a ratio of the second short-circuit current to the current protection setting value; andmeasuring a current protection sensitivity by using the sensitivity coefficient.

2. The method according to claim 1, wherein,the distribution network parameter comprises a phase voltage of the power system and short-circuit loop impedance,the first short-circuit current comprises a first three-phase short-circuit current, a first B-phase short-circuit current, and a first C-phase short-circuit current; andaccording to the distribution network parameter, acquiring the first short-circuit current and the system short-circuit capacity in response to the distributed generator being not connected to the power system comprises:2023387063   21 Jul 2026calculating the first three-phase short-circuit current according to the phase voltage of the power system and the short-circuit loop impedance;calculating the first B-phase short-circuit current and the first C-phase short-circuit current according to the phase voltage of the power system and the short-circuit loop impedance; andcalculating the system short-circuit capacity according to the first three-phase short-circuit current and a normal operating voltage at a short circuit.

3. The method according to claim 2, wherein calculating the first B-phase short-circuit current and the first C-phase short-circuit current according to the phase voltage of the power system and the short-circuit loop impedance comprises:calculating a positive sequence current according to the phase voltage of the power system and the short-circuit loop impedance; andcalculating the first B-phase short-circuit current and the first C-phase short-circuit current according to the positive sequence current.

4. The method according to claim 3, wherein determining the fault short-circuit ratio according to the relative position relationship between the grid-connected position of the distributed generator in the power system, the current measurement point position, and the fault position comprises:determining the fault short-circuit ratio according to the system short-circuit capacity, a rated capacity of the distributed generator corresponding to the relative position relationship, a rated output current of the distributed generator corresponding to the relative position relationship, the first three-phase short-circuit current, and the positive sequence current.

5. The method according to claim 4, wherein the fault short-circuit ratio comprises:a first fault short-circuit ratio in response to the relative position relationship being that the grid-connected position is located before the current measurement point position and the fault position;a second fault short-circuit ratio in response to the relative position relationship being that the grid-connected position is located before the fault position and after the current measurement point position; anda third fault short-circuit ratio in response to the relative position relationship being that the grid-connected position is located after the current measurement point position and the fault position.

6. The method according to claim 4, wherein in response to the distributed generator adopting the optimal positive sequence voltage support strategy, calculating the phase of the output2023387063   21 Jul 2026current of the distributed generator according to the phase voltage of the power system, the positive and negative sequence short-circuit impedance, the line impedance, the output current of the distributed generator, the line impedance between buses, and the line impedance angle comprises:calculating a phase of a grid-connected bus voltage of the distributed generator according to the phase voltage of the power system, the positive and negative sequence short-circuit impedance, the line impedance, the output current of the distributed generator, and the line impedance between buses; andcalculating the phase of the output current of the distributed generator according to the phase of the grid-connected bus voltage of the distributed generator and the line impedance angle.

7. The method according to claim 5, wherein,the second short-circuit current comprises a second three-phase short-circuit current, a second B-phase short-circuit current, and a second C-phase short-circuit current; andaccording to the first short-circuit current, the fault short-circuit ratio, and the phase of the output current of the distributed generator, determining the second short-circuit current in response to the distributed generator being connected to the power system comprises:determining the second three-phase short-circuit current according to the first three-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, and the phase of the output current of the distributed generator;determining the second B-phase short-circuit current according to the first B-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, the third fault short-circuit ratio, and the phase of the output current of the distributed generator; anddetermining the second C-phase short-circuit current according to the first C-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, the third fault short-circuit ratio, and the phase of the output current of the distributed generator.

8. A distribution network current protection sensitivity analysis apparatus, comprising:a current and capacity acquisition unit configured to acquire a first short-circuit current and a system short-circuit capacity according to a distribution network parameter in response to a distributed generator being not connected to a power system;a fault short-circuit ratio determination unit configured to determine a fault short-circuit ratio according to a relative position relationship between a grid-connected position of the distributed generator in the power system, a current measurement point position, and a fault position;a phase determination unit configured to, in response to the distributed generator adopting an2023387063   21 Jul 2026optimal positive sequence voltage support strategy, calculate a phase of an output current of the distributed generator according to a phase voltage of the power system, positive and negative sequence short-circuit impedance, line impedance, the output current of the distributed generator, line impedance between buses, and a line impedance angle;a short-circuit current determination unit configured to, according to the first short-circuit current, the fault short-circuit ratio, and the phase of the output current of the distributed generator, determine a second short-circuit current in response to the distributed generator being connected to the power system; anda sensitivity analysis unit configured to perform current protection sensitivity analysis according to a current protection setting value and the second short-circuit current;wherein the sensitivity analysis unit is configured to:determine a sensitivity coefficient according to the second short-circuit current and the current protection setting value; wherein the sensitivity coefficient is a ratio of the second short-circuit current to the current protection setting value; andmeasure a current protection sensitivity by using the sensitivity coefficient.

9. The apparatus according to claim 8, wherein,the distribution network parameter comprises a phase voltage of the power system and short-circuit loop impedance,the first short-circuit current comprises a first three-phase short-circuit current, a first B-phase short-circuit current, and a first C-phase short-circuit current; andthe current and capacity acquisition unit comprises:a first three-phase short-circuit current calculation module configured to calculate the first three-phase short-circuit current according to the phase voltage of the power system and the short-circuit loop impedance;a B- and C-phase short-circuit current determination module configured to calculate the first B-phase short-circuit current and the first C-phase short-circuit current according to the phase voltage of the power system and the short-circuit loop impedance; anda system short-circuit capacity determination module configured to calculate the system short-circuit capacity according to the first three-phase short-circuit current and a normal operating voltage at a short circuit.

10. The apparatus according to claim 9, wherein the B- and C-phase short-circuit current determination module comprises:2023387063   21 Jul 2026a positive sequence current determination sub-module configured to calculate a positive sequence current according to the phase voltage of the power system and the short-circuit loop impedance; anda B- and C-phase short-circuit current calculation module configured to calculate the first B-phase short-circuit current and the first C-phase short-circuit current according to the positive sequence current.

11. The apparatus according to claim 10, wherein the fault short-circuit ratio determination unit is configured to:determine the fault short-circuit ratio according to the system short-circuit capacity, a rated capacity of the distributed generator corresponding to the relative position relationship, a rated output current of the distributed generator corresponding to the relative position relationship, the first three-phase short-circuit current, and the positive sequence current.

12. The apparatus according to claim 11, wherein the fault short-circuit ratio comprises:a first fault short-circuit ratio in response to the relative position relationship being that the grid-connected position is located before the current measurement point position and the fault position;a second fault short-circuit ratio in response to the relative position relationship being that the grid-connected position is located before the fault position and after the current measurement point position; anda third fault short-circuit ratio in response to the relative position relationship being that the grid-connected position is located after the current measurement point position and the fault position.

13. The apparatus according to claim 11, wherein the phase determination unit comprises:a first phase calculation module configured to calculate a phase of a grid-connected bus voltage of the distributed generator according to the phase voltage of the power system, the positive and negative sequence short-circuit impedance, the line impedance, the output current of the distributed generator, and the line impedance between buses; anda second phase calculation module configured to calculate the phase of the output current of the distributed generator according to the phase of the grid-connected bus voltage of the distributed generator and the line impedance angle.

14. The apparatus according to claim 12, wherein,the second short-circuit current comprises a second three-phase short-circuit current, a second B-phase short-circuit current, and a second C-phase short-circuit current; and2023387063   21 Jul 2026the short-circuit current determination unit comprises:a three-phase short-circuit current determination module configured to determine the second three-phase short-circuit current according to the first three-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, and the phase of the output current of the distributed generator;a B-phase short-circuit current determination module configured to determine the second B-phase short-circuit current according to the first B-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, the third fault short-circuit ratio, and the phase of the output current of the distributed generator; anda C-phase short-circuit current determination module configured to determine the second C-phase short-circuit current according to the first C-phase short-circuit current, the first fault short-circuit ratio, the second fault short-circuit ratio, the third fault short-circuit ratio, and the phase of the output current of the distributed generator.

15. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein when executing the program, the processor performs the method according to any one of claims 1 to 7.

16. A computer-readable medium storing a computer program, whereinthe program, when executed by a processor, causes the processor to perform the method according to any one of claims 1 to 7.

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