Method and system for setting distance protection of overlapping double circuit lines

Abstract

The application provides a kind of distance protection setting method and system for the same-pole double circuit line, the method comprises: first, the electrical coefficient of the same-pole double circuit line and the double circuit line clamping mode information are obtained, then according to the reliability coefficient, the double circuit line setting section is selected, the setting section is the clamping double circuit line where the setting point is located, the single circuit line is positioned, the single circuit line is the double circuit line without the setting point, to calculate the setting impedance of the single circuit line, then according to the setting impedance, the sensitivity is calculated, and the distance protection sensitivity check is carried out, if the sensitivity is greater than or equal to the sensitivity threshold, the setting impedance is output, if the sensitivity is less than the sensitivity threshold, the reliability coefficient is modified, and the setting impedance of the single circuit line is recalculated, to solve the problem that double circuit line clamping mode affects the sensitivity of distance protection.

Description

Technical Field

[0001] This application relates to the field of power, and in particular to a distance protection setting method and system for connecting two parallel lines on the same pole. Background Technology

[0002] With the growth of national economic demand for electricity and the expansion of urban areas, the outgoing corridors of transmission lines are becoming increasingly congested. In order to improve the utilization efficiency of power grid lines, double-circuit lines on the same pole are sometimes erected on the same tower or on the same tower with mixed voltage, or existing parallel double-circuit lines on the same pole are used to form hybrid lines. These hybrid lines include single-circuit lines (which can be represented by S) and parallel double-circuit lines on the same pole (which can be represented by D), that is, there are various forms such as S+D and S+D+S.

[0003] To reduce the unbalanced current in parallel double-circuit lines on the same pole, the parallel double-circuit lines on the same pole are connected by overlapping. That is, several overlapping points are selected in the parallel double-circuit lines on the same pole, and the A, B, and C phases of the first circuit are connected to the A, B, and C phases of the second circuit respectively. The transmission channel is constructed by using the parallel double-circuit lines on the same pole, which has good economic benefits. If the mixed line part is a single circuit, the protection needs to be implemented using the voltage and current of the single circuit.

[0004] Furthermore, with the development of communication technology and synchronous phasor measurement technology, protection functions can also be achieved using information from double-circuit lines. Mutual inductance exists between double-circuit lines on the same pole, leading to complex and diverse fault types. The mutual inductance between double-circuit lines can adversely affect distance protection, phase selection, and distance measurement. Additionally, different splicing schemes can also affect protection performance, especially distance protection, further impacting its sensitivity. Summary of the Invention

[0005] This application provides a distance protection setting method and system for connecting double-circuit lines on the same pole, in order to solve the problem that the connection method of double-circuit lines affects the sensitivity of distance protection.

[0006] In a first aspect, this application provides a distance protection setting method for a double-circuit line with overlapping connections on the same pole, comprising: acquiring the electrical coefficient of the double-circuit line with overlapping connections on the same pole and the overlapping method information of the double-circuit line; selecting a setting section of the double-circuit line according to a reliability coefficient, wherein the setting section is the overlapping double-circuit line where the setting point is located; locating a single-circuit line, wherein the single-circuit line is a double-circuit line without the setting point; calculating the setting impedance of the single-circuit line; calculating the sensitivity based on the setting impedance and performing a distance protection sensitivity check; if the sensitivity is greater than or equal to a sensitivity threshold, outputting the setting impedance; if the sensitivity is less than the sensitivity threshold, modifying the reliability coefficient and recalculating the setting impedance of the single-circuit line.

[0007] Optionally, the electrical coefficients include one or more combinations of double-circuit line length, impedance per unit length, and inter-line mutual inductance.

[0008] Optionally, the double-circuit line splicing information includes setting splicing points on the double-circuit lines strung on the same pole, so that the intervals between the splicing points are equal.

[0009] Optionally, calculating the setting impedance of the single-circuit line may further include: calculating the grounding distance protection measurement impedance and calculating the phase-to-phase distance protection measurement impedance.

[0010] Optionally, calculating the grounding distance protection measurement impedance includes: calculating the zero-sequence compensation coefficient based on the unit zero-sequence impedance of the double-circuit line, the zero-sequence unit mutual impedance between the double-circuit lines, and the positive-sequence impedance of the entire length of the single-circuit line; calculating the amplification coefficient based on the positive-sequence impedance of the entire length of the single-circuit line, the zero-sequence current distribution coefficient on both sides of the protective ground, and the zero-sequence unit mutual impedance between the double-circuit lines; calculating the grounding distance protection measurement impedance based on the zero-sequence compensation coefficient, the amplification coefficient, the voltage at the double-circuit protection installation point, the zero-sequence current value at the double-circuit protection installation point, the current at the double-circuit protection installation point, a first percentage, a second percentage, and a third percentage, wherein the first percentage is the percentage of the electrical distance from the nearest connection point of the fault point to the protection installation point relative to the single-circuit line of the double-circuit line on the same pole; the second percentage is the percentage of the distance from the fault point to the nearest connection point relative to the single-circuit line of the double-circuit line on the same pole; and the third percentage is the percentage of the connection area where the fault point is located relative to the single-circuit line of the double-circuit line on the same pole.

[0011] Optionally, calculating the phase-to-phase distance protection measurement impedance includes: calculating the phase-to-phase distance protection measurement impedance based on the measured voltage and current values ​​at the protection installation location, a first percentage, a second percentage, and a third percentage.

[0012] Optionally, based on the set impedance, the sensitivity is calculated, and the distance protection sensitivity is verified, including: if a ground fault occurs at the connection point, the distance protection is set at 80%; if a phase-to-phase fault occurs at the connection point, the distance protection is set at 85%.

[0013] Optionally, if the distance protection is set at 80%, the sensitivity should be checked using the following formula:

[0014]

[0015] Wherein, α is the proportion of the overlap at the distance protection installation point to the length of a single circuit of a double-circuit line on the same pole, β is the proportion of the overlap at the distance protection installation point to the length of a single circuit of a double-circuit line on the same pole, β1 is the second percentage, which is the percentage of the distance from the fault point to the nearest overlap point to the length of a single circuit of a double-circuit line on the same pole, Z1 is the positive sequence impedance of the entire length of the single circuit, and K′ is the amplification factor.

[0016] Optionally, if a phase-to-phase fault occurs at the overlap point, the sensitivity is checked according to the following formula:

[0017]

[0018] in, This is the current value at the beginning of the line. This is the current value at the other end of the line.

[0019] Secondly, this application also provides a distance protection system for double-circuit lines connected on the same pole, comprising: an acquisition unit, a calculation unit, and a judgment unit, wherein the acquisition unit is used to acquire the electrical coefficient of the double-circuit line connected on the same pole and the connection method information of the double-circuit line; select the setting section of the double-circuit line according to the reliability coefficient, the setting section being the double-circuit line where the setting point is located; locate a single-circuit line, the single-circuit line being a double-circuit line without the setting point; the calculation unit is used to calculate the setting impedance of the single-circuit line; calculate the sensitivity according to the setting impedance, and perform distance protection sensitivity verification; the judgment unit is used to judge the sensitivity, if the sensitivity is greater than or equal to a sensitivity threshold, output the setting impedance; if the sensitivity is less than the sensitivity threshold, modify the reliability coefficient and recalculate the setting impedance of the single-circuit line.

[0020] As can be seen from the above technical solutions, this application provides a distance protection setting method and system for double-circuit lines connected on the same pole. The method includes: first, obtaining the electrical coefficient of the double-circuit line connected on the same pole and the connection method information of the double-circuit line; then, selecting the setting section of the double-circuit line according to the reliability coefficient, wherein the setting section is the double-circuit line where the setting point is located, and locating a single-circuit line, wherein the single-circuit line is the double-circuit line without the setting point, to calculate the setting impedance of the single-circuit line; then, calculating the sensitivity according to the setting impedance, and performing distance protection sensitivity verification; if the sensitivity is greater than or equal to the sensitivity threshold, then outputting the setting impedance; if the sensitivity is less than the sensitivity threshold, then modifying the reliability coefficient and recalculating the setting impedance of the single-circuit line, so as to solve the problem that the connection method of the double-circuit line affects the sensitivity of the distance protection. Attached Figure Description

[0021] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A flowchart of a distance protection setting method for overlapping double-circuit lines on the same pole;

[0023] Figure 2 A schematic diagram of a double-circuit line overlapping on the same pole;

[0024] Figure 3 This is a schematic diagram illustrating the implementation of the tuning method;

[0025] Figure 4 The diagram shows the actual protection range of IA-G at different locations with an overlap pattern of 8km.

[0026] Figure 5 The diagram shows the actual protection range of the IBC at different locations with an overlap pattern of 8km.

[0027] Figure 6 The diagram shows the actual protection range of IBIIC at different locations with an overlap pattern of 8km.

[0028] Figure 7 The diagram shows the actual protection range of IA-G at different locations with an overlap pattern of 20km.

[0029] Figure 8 This diagram illustrates the actual protection range of the IBC at different locations, with an overlap pattern of 20km.

[0030] Figure 9 The diagram shows the actual protection range of IBIIC at different locations with an overlap interval of 20km. Detailed Implementation

[0031] The embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described below do not represent all embodiments consistent with this application. They are merely examples of systems and methods consistent with some aspects of this application as detailed in the claims.

[0032] Compared to single-circuit lines, double-circuit lines on the same pole have several unique characteristics. Besides the possibility of single-circuit faults occurring on either circuit, they also experience cross-line faults caused by lightning strikes or pole collapses. Because the two circuits share a tower and are very close together, mutual inductance exists not only between phases but also between lines. The coupling between the two circuits further complicates fault characteristics, making fault location difficult and affecting the proper operation of relay protection devices. There are as many as 120 types of faults in double-circuit lines on the same pole. Furthermore, with the development of communication and synchronous phasor measurement technologies, information from the double circuits can also be used for protection functions. Due to the mutual inductance coupling between the lines in double-circuit lines on the same pole, the fault types are even more complex and diverse. The mutual inductance between the double circuit lines adversely affects distance protection, phase selection, and distance measurement. Additionally, different splicing schemes can affect the performance of protection actions, especially distance protection, further impacting its sensitivity.

[0033] The six-sequence fault component method is the foundation for decoupling double-circuit transmission lines on the same tower. It solves the mutual inductance problem between the two circuits. In the six-sequence fault component network, the ratio of the effective values ​​of the sequence current fault components on both sides of the line is still only a function of the line impedance, the system impedance at both ends, and the fault distance. The resulting ranging equation is concise, easy to solve, and not limited by fault type or transition resistance, nor does it require data synchronization at both ends. In the ranging equation, the distributed capacitance is allocated as a lumped parameter to both sides of the transmission line from the fault point, thus achieving high ranging accuracy.

[0034] See Figure 1 This application provides a distance protection setting method for overlapping double-circuit lines on the same pole, comprising:

[0035] S100: Obtain the electrical coefficients of double-circuit lines on the same pole and the information on the connection method of the double-circuit lines.

[0036] Since calculating the set impedance requires designing the electrical coefficients at both ends of the double-circuit line, these electrical coefficients can be sampled simultaneously at both ends of the double-circuit line. Firstly, in some embodiments, the electrical coefficients include one or more combinations of the double-circuit line length, impedance per unit length, and inter-line mutual inductance. For example, the electrical coefficients might include a double-circuit line length of dkm and an impedance per unit length of yΩ; another example might include an impedance per unit length of yΩ and an inter-line mutual inductance of zH. It is understood that the electrical coefficients are not limited to those mentioned above.

[0037] In some embodiments, the double-circuit line splicing method information includes setting splice points on the parallel double-circuit lines on the same pole, such that the splice points are spaced equally. The number of splice points is not limited; multiple splice points can be set. See [link to documentation]. Figure 2There is a protection installation point at the beginning of the M-side line and a protection installation point at the beginning of the N-side line. Among them, a, b, c, d, and e are lap joints, and there are five lap joints. The interval between the lap joints is x km. G of the M-side line is the system power supply of the M-side line, and G of the N-side line is the system power supply of the N-side line.

[0038] S200: Select the setting section for the double-circuit line based on the reliability coefficient.

[0039] Among them, the setting section refers to the overlapping double-circuit line where the setting point is located, for example: Figure 2 As shown, if the section where the setting point is located is segment cd, then the setting section is segment cd.

[0040] S300: Positioning single-circuit line.

[0041] Among them, a single-circuit line is a double-circuit line without a setting point. That is, according to the setting section mentioned above as the cd section, the Ma, ab, bc, de, and eN sections can be regarded as single-circuit lines. See [link to relevant documentation]. Figure 3 The CD segment is equivalent to Figure 3 The middle double loop segment, while other segments are equivalent to Figure 3 A single loop segment in MN.

[0042] S400: Calculate the setting impedance of a single-circuit line.

[0043] Distance protection reflects the distance or impedance between the setting point and the protection installation point. Distance protection includes ground distance protection and phase-to-phase distance protection. Ground distance protection can protect against single-phase faults, and phase-to-phase distance protection can protect against phase-to-phase faults. Therefore, in some embodiments, calculating the setting impedance of a single circuit includes calculating the ground distance protection measurement impedance and the phase-to-phase distance protection measurement impedance, and using different impedance values ​​to protect against single-phase faults and phase-to-phase faults.

[0044] In some embodiments, the ground distance protection measurement impedance is first calculated using the following formula:

[0045]

[0046]

[0047]

[0048] in, For the voltage at the installation location of the double-circuit protection, K1 is the current at the installation point of the double-circuit protection, and K1 is the zero-sequence compensation coefficient. Z1 is the zero-sequence current value at the installation point of the double-circuit protection; α is the percentage of the electrical distance from the nearest connection point of the fault to the installation point of the protection relative to the single circuit of the double-circuit line on the same pole; β1 is the percentage of the distance from the fault to the nearest connection point relative to the single circuit of the double-circuit line on the same pole; Z1 is the positive-sequence impedance of the entire length of the single circuit; K′ is the amplification factor; Z0 is the unit zero-sequence impedance of the double-circuit line; Z... m0 The zero-sequence unit mutual impedance between the two circuits, C N0 And C M0 Z1 is the zero-sequence current distribution coefficient on both sides of the protective ground, and Z1 is the positive-sequence unit impedance of a single-circuit line on the same pole.

[0049] In some embodiments, the sum of the zero-sequence currents flowing through the fault point can also be calculated using the following formula:

[0050]

[0051] Then, the grounding distance protection measurement impedance is calculated using the following formula:

[0052]

[0053] in, To protect the measuring voltage at the installation location, To protect the current value at the installation location.

[0054] S500: Calculate the sensitivity based on the set impedance.

[0055] After calculating the phase-to-phase distance protection measurement impedance and the grounding distance protection measurement impedance, i.e., after completing the setting impedance calculation, the distance protection sensitivity is tested based on the setting impedance to solve the problem of the impact of the double-circuit line connection method on the distance protection sensitivity.

[0056] Firstly, the first scenario is a ground fault. In some embodiments, if a ground fault occurs at the connection point, the distance protection is set at 80%, that is, according to... Perform the adjustment;

[0057] Sensitivity can be verified using the following formula:

[0058]

[0059] Wherein, α is the proportion of the overlap at the distance protection installation point to the length of a single circuit of a double-circuit line on the same pole, β is the proportion of the overlap at the distance protection installation point to the length of a single circuit of a double-circuit line on the same pole, β1 is the second percentage, which is the percentage of the distance from the fault point to the nearest overlap point to the length of a single circuit of a double-circuit line on the same pole, Z1 is the positive sequence impedance of the entire length of the single circuit, and K′ is the amplification factor.

[0060] Secondly, the second scenario involves a phase-to-phase fault. In some embodiments, if a phase-to-phase fault occurs at the overlap point, the distance protection is set at 85%, which is based on... Perform the adjustment.

[0061] Sensitivity can be verified using the following formula:

[0062]

[0063] in, This is the current value at the beginning of the line. This is the current value at the other end of the line.

[0064] Understandably, see again Figure 2 , Figure 3 ,in This can be the current value at the beginning of the line on side M. It can be the current value at the beginning of the N-side line.

[0065] The distance protection for ground faults is set at 80%, and the distance protection for phase-to-phase faults is set at 85%. This is based on the errors of the impedance relays, current and voltage transformers, and the errors of the protection devices themselves.

[0066] S600: Compare distance protection sensitivity verification and sensitivity threshold.

[0067] S700: If the sensitivity is less than the sensitivity threshold, modify the reliability coefficient and recalculate the setting impedance of the single-circuit line.

[0068] That is, the setting section of the double-circuit line is reselected, and the grounding distance protection measurement impedance and phase-to-phase distance protection measurement impedance of the single-circuit line are recalculated based on the selected setting section. Then, the sensitivity is verified based on the grounding distance protection measurement impedance and the phase-to-phase distance protection measurement impedance.

[0069] S800: If the sensitivity is greater than or equal to the sensitivity threshold, then output the set impedance.

[0070] Once the output impedance is set, distance protection can be applied to different connection schemes based on the set impedance. For example, distance protection can be applied to double-circuit lines on the same tower using a parallel connection method.

[0071] Based on the six-sequence fault component method, this application derives the expression for the same-vector measured impedance under various fault types of parallel double-circuit lines on the same pole, and then analyzes the changes in the same-vector measured impedance under different connection methods to solve the problem of the impact of double-circuit line connection methods on the sensitivity of distance protection.

[0072] Considering the different fault types, connection methods, and fault locations of parallel double-circuit lines on the same pole, a 330kV parallel double-circuit line model was built using PSCAD / EMTDC simulation software to verify the effectiveness of the distance protection setting method for parallel double-circuit lines on the same pole provided in this embodiment. The electrical parameters are: total line length 40km, simulation step size 250μs, and system parameters: M-side positive sequence impedance Z. MS1 =0.1+j11.103Ω, Z MS0 = 1 + j28.061Ω; N-side system positive sequence impedance Z NS1 =0.1+j8.007Ω, Z NS0 = 1 + j24.021Ω. Line parameters: Positive sequence impedance Z1 = 0.0478 + j0.2826Ω / km; Zero sequence impedance Z0 = 0.1903 + j0.628Ω / km; Line-to-line mutual impedance Z1 = 0.0422 + j0.2282Ω / km; Positive sequence capacitive reactance C1 = 0.2654MΩ*km; Zero sequence capacitive reactance C0 = 0.41306MΩ*km. The phase angle difference between the power supplies at both ends of the line is 10°.

[0073] The verification was conducted using overlapping methods with intervals of 8km and 20km, respectively.

[0074] First, using an 8km overlap method, the simulation results of the measured impedance of IA-G, IBC, and IBCIIIB at different locations are shown in Tables 1, 2, and 3, respectively:

[0075] Table 1 IA-G Faults

[0076]

[0077]

[0078] Table 2 IBC Faults

[0079] 5％ 0.048+0.286i 0.290 15％ 0.0943+1.2254i 1.2290 25％ 0.2054+1.8125i 1.8241 35％ 0.2785+2.3767i 2.3930 45％ 0.455+2.445i 2.487 55％ 0.450+3.237i 3.268 65％ 0.628+4.016i 4.065 75％ 0.724+4.161i 4.223 85％ 0.817+4.976i 5.043 95％ 0.909+5.382i 5.458 100％ 0.9560+5.652i 5.732

[0080] Table 3 IBCIIB Faults

[0081]

[0082]

[0083] For the 8km interval overlap method, the actual protection range of IA-G faults at different locations is as follows: Figure 4 For the actual protection scope of IBC faults, please refer to [reference needed]. Figure 5 For the actual protection scope of IBC1B faults, please refer to [link / reference]. Figure 6 .

[0084] Secondly, using an overlap method with intervals of 20km, the simulation results of the measured impedance of IA-G, IBC, and IBC1IB faults at different locations are shown in Tables 4, 5, and 6, respectively:

[0085] Table 4 IA-G Faults

[0086] 5％ 0.0410+0.5901i 0.5915 15％ 0.1464+1.6061i 1.6127 25％ 0.2735+2.2609i 2.2774 35％ 0.4116+2.8154i 2.8454 45％ 0.5644+2.9431i 2.9968 55％ 0.6316+3.2375i 3.2985 65％ 0.8153+4.6680i 4.7387 75％ 0.9372+5.4918i 5.5712 85％ 1.0901+5.9343i 6.0336 95％ 1.1812+5.6100i 5.733 100％ 0.9560+5.652i 5.732

[0087] Table 5 IBC Faults

[0088]

[0089]

[0090] Table 6 IBCIIB Faults

[0091] 5％ 0.0336+0.5488i 0.5498 15％ 0.4089+1.0527i 1.1294 25％ 0.1727+2.2350i 2.2416 35％ 0.2718+2.6656i 2.6794 45％ 3.2501+1.1677i 3.4535 55％ 0.1655+1.3085i 1.3189 65％ 0.5317+4.7880i 4.8174 75％ 0.5914+5.4042i 5.4364 85％ 0.6693+6.0099i 6.0471 95％ 0.8136+5.6060i 5.6648 100％ 0.9560+5.652i 5.732

[0092] For the overlapping method at 20km intervals, the actual protection range of IA-G faults at different locations is shown in [reference needed]. Figure 7 For the actual protection scope of IBC faults, please refer to [reference needed]. Figure 8 For the actual protection scope of IBIIC faults, please refer to [link / reference]. Figure 9 .

[0093] Based on the test intervals of 8km and 20km, the simulation results of the measured impedance of IA-G, IBC, and IBCIB faults at different locations, as well as the actual protection range of IA-G, IBC, and IBCIB at different locations, show that regardless of whether the test interval is 8km or 20km, the simulation results of the measured impedance of IA-G, IBC, and IBCIB faults at different locations are not significantly different from the actual protection range. This demonstrates that the distance protection setting method for parallel double-circuit lines on the same pole provided in this application can solve the problem of the influence of different connection methods on distance sensitivity.

[0094] Based on the above-mentioned distance protection setting method for double-circuit lines connected to the same pole, some embodiments of this application also provide a distance protection system for double-circuit lines connected to the same pole. The system includes: an acquisition unit, a calculation unit, and a judgment unit. The acquisition unit is used to acquire the electrical coefficients of the double-circuit lines connected to the same pole and the connection method information of the double-circuit lines; select the setting section of the double-circuit line according to the reliability coefficient, the setting section being the double-circuit line where the setting point is located; locate the single-circuit line, the single-circuit line being the double-circuit line without the setting point; the calculation unit is used to calculate the setting impedance of the single-circuit line; calculate the sensitivity based on the setting impedance, and perform distance protection sensitivity verification; the judgment unit is used to judge the sensitivity. If the sensitivity is greater than or equal to the sensitivity threshold, the setting impedance is output; if the sensitivity is less than the sensitivity threshold, the reliability coefficient is modified and the setting impedance of the single-circuit line is recalculated.

[0095] As can be seen from the above technical solutions, this embodiment provides a distance protection setting method and system for double-circuit lines connected on the same pole. The method includes: first, obtaining the electrical coefficients of the double-circuit lines connected on the same pole and the double-circuit connection method information; then, selecting the double-circuit line setting section based on the reliability coefficient, the setting section being the double-circuit line where the setting point is located; locating the single-circuit line, which is a double-circuit line without the setting point, to calculate the setting impedance of the single-circuit line; then, calculating the sensitivity based on the setting impedance and performing distance protection sensitivity verification; if the sensitivity is greater than or equal to the sensitivity threshold, the setting impedance is output; if the sensitivity is less than the sensitivity threshold, the reliability coefficient is modified, and the setting impedance of the single-circuit line is recalculated to solve the problem of the double-circuit connection method affecting the distance protection sensitivity.

[0096] Similar parts between the embodiments provided in this application can be referred to mutually. The specific implementation methods provided above are only a few examples under the overall concept of this application and do not constitute a limitation on the scope of protection of this application. For those skilled in the art, any other implementation methods extended from the solution of this application without creative effort shall fall within the scope of protection of this application.

Claims

1. A method for setting the distance protection of overlapping double-circuit lines on the same pole, characterized in that, include: Obtain the electrical coefficients of the parallel double-circuit lines on the same pole and the information on the connection method of the double-circuit lines; Based on the reliability coefficient, the setting section of the double-circuit line is selected, and the setting section is the overlapping double-circuit line where the setting point is located; The single-circuit line is defined as a double-circuit line that does not include the set point. Calculate the set impedance of the single-circuit line; Based on the set impedance, the sensitivity is calculated, and the distance protection sensitivity is verified. If the sensitivity is less than or equal to the sensitivity threshold, then the tuning impedance is output; If the sensitivity is greater than the sensitivity threshold, then the reliability coefficient is modified and the setting impedance of the single-circuit line is recalculated. The calculation of the setting impedance of the single circuit also includes: calculating the grounding distance protection measurement impedance and calculating the phase-to-phase distance protection measurement impedance; The grounding distance protection measurement impedance is calculated using the following formula: ； ； ； The phase-to-phase distance protection measurement impedance is calculated using the following formula: ； If a grounding fault occurs at the connection point, the sensitivity should be checked according to the following formula: ； If a phase-to-phase fault occurs at the overlap point, the sensitivity should be checked according to the following formula: ； in, To measure impedance for grounding distance protection, For the voltage at the installation location of the double-circuit protection, For zero-order compensation coefficient, The zero-sequence current value at the installation location of the double-circuit protection. The percentage of the electrical distance between the nearest connection point to the fault location and the protection installation location relative to the distance between the two circuits on the same pole and a single circuit. The percentage of the distance from the fault point to the nearest splice point relative to the distance of a single-circuit double-circuit line on the same pole. The percentage of the overlapping area where the fault point is located relative to the single-circuit line of a double-circuit line on the same pole. The positive sequence impedance of the entire length of a single-circuit line. To increase the coefficient, For a double-circuit line, the unit zero-sequence impedance, The zero-sequence unit mutual impedance between the two circuits as well as For the zero-sequence current distribution coefficient on both sides of the protected ground, For the positive sequence unit impedance of a single-circuit line on the same pole, For phase-to-phase distance protection, measuring impedance, To protect the measuring voltage at the installation location, To protect the current value at the installation location, For the current value at the beginning of the line, This represents the current value at the other end of the line.

2. The distance protection setting method for overlapping double-circuit lines on the same pole according to claim 1, characterized in that, The electrical coefficients include one or more combinations of double-circuit line length, impedance per unit length, and mutual inductance between lines.

3. The distance protection setting method for overlapping double-circuit lines on the same pole according to claim 1, characterized in that, The double-circuit line splicing method information includes setting splicing points on the double-circuit lines strung on the same pole, so that the intervals of the splicing points are equal.

4. A distance protection system for overlapping double-circuit lines on the same pole, characterized in that, The distance protection system for overlapping double-circuit lines on the same pole is applied to the distance protection setting method for overlapping double-circuit lines on the same pole as described in any one of claims 1-3; the system includes: an acquisition unit, a calculation unit, and a judgment unit, wherein, The acquisition unit is used to acquire the electrical coefficient of the parallel double-circuit line on the same pole and the splicing method information of the double-circuit line; select the setting section of the double-circuit line according to the reliability coefficient, the setting section being the spliced ​​double-circuit line where the setting point is located; and locate the single-circuit line, the single-circuit line being the double-circuit line that does not contain the setting point. The calculation unit is used to calculate the set impedance of the single-circuit line; and based on the set impedance, calculate the sensitivity and perform distance protection sensitivity verification. The judgment unit is used to judge the sensitivity. If the sensitivity is less than or equal to the sensitivity threshold, the set impedance is output. If the sensitivity is greater than the sensitivity threshold, the reliability coefficient is modified and the set impedance of the single circuit is recalculated.

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