Adaptive distance protection method and system

Abstract

The present invention discloses an adaptive distance protection method and system, comprising: extracting transient time-domain information of electrical quantities at the protection installation; using this transient time-domain information to determine the fault direction characteristics; expanding the range of distance protection operation when the positive direction is determined; and reducing the range of distance protection operation when the negative direction is determined. Advantages: This invention addresses the problem of abnormal distance protection operation at new energy stations or flexible direct current transmission lines by using transient time-domain information of electrical quantities at the protection installation to determine the fault direction and adaptively using distance protection elements with different protection ranges to ensure correct distance protection operation.

Description

Technical Field

[0001] The present invention relates to an adaptive distance protection method and system, belonging to the technical field of power system relay protection. Background Art

[0002] Distance protection is a type of protection that operates by measuring the ratio of the voltage at the starting end of the protected line to the line current. It reflects the size of the impedance (the length of the distance) between the short-circuit point and the protection installation. Distance protection is less affected by the system operation mode and has been widely used in power grids.

[0003] Impedance relays are the core of distance protection. Their operating equations are primarily categorized into two types: amplitude comparison and phase comparison. Among these phase-comparison-based impedance relays, phase-comparison directional impedance relays with memory, which use positive-sequence voltage as the polarization voltage, incorporate the distribution of positive-sequence voltage in the system. This solves the problem of traditional line outlets failing to accurately compare polarization voltages when symmetrical or asymmetrical short-circuit faults occur, and are therefore widely used in distance protection.

[0004] With the increasing number of renewable energy generation devices and various power sources such as flexible direct current transmission (FDC) connected to the grid, the electrical characteristics of traditional power sources are changing. During line faults, the fault current generated by the control strategies of power electronic devices is limited and phase-controlled. As a result, the positive-sequence voltage cannot represent the power supply voltage providing the short-circuit current. Phase-comparison directional impedance relays, which use the positive-sequence voltage as their polarization voltage, lose their directional properties. As a result, the selectivity and reliability of distance protection decrease, and the probability of false or inappropriate operation increases. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide an adaptive distance protection method and system.

[0006] To solve the above technical problems, the present invention provides an adaptive distance protection method, comprising:

[0007] Extract transient time domain information of electrical quantities at protection installation locations;

[0008] The transient time domain information of electrical quantities is used to determine the fault direction characteristics. When the positive direction is determined, the distance protection action range is expanded; when the reverse direction is determined, the distance protection action range is reduced.

[0009] Furthermore, the extraction of transient time domain information of electrical quantities at the protection installation location includes:

[0010] Use formula (1) to calculate the transient time domain information of voltage quantity,

[0011] Δu m(k) =u m(k) -u m(k-N) (1)

[0012] Among them, △u m(k) is the transient time domain information of voltage, u m(k) is the voltage sampling value of the protection device at the current moment, u m(k-N) is the voltage sampling value of the protection device one cycle ago, N is the number of sampling points in one cycle, and m represents phases a, b, and c or between phases ab, bc, and ca;

[0013] Use formula (2) to calculate the transient time domain information of current,

[0014] Δi m(k) =i m(k) -i m(k-N) (2)

[0015] Among them, Δi m(k) is the transient time domain information of the current, i m(k) is the current sampling value of the protection device at the current moment, i m(k-N) It is the current sampling value of the protection device one cycle ago.

[0016] Further,

[0017] The criterion for the positive direction is:

[0018] S m(k) =Δu m(k) Δi m(k) <0

[0019] The criterion for the reverse direction is:

[0020] S m(k) =Δu m(k) Δi m(k) >0

[0021] Among them, S m(k) is the constructed energy direction expression.

[0022] Furthermore, the expansion of the distance protection action range includes:

[0023] The operating range of the mho distance protection based on positive sequence voltage polarization is expanded to the following range:

[0024]

[0025] in, To expand the angle range of phase distance protection action, take 15~20°, polarization voltage Take the positive sequence voltage at the protection installation location Operating voltage To protect the vector of voltage and current at the installation location, Z setIt is the distance protection setting value.

[0026] Furthermore, the narrowing of the distance protection action range includes:

[0027] The operating range of the mho distance protection based on positive sequence voltage polarization is narrowed to the following range:

[0028]

[0029] in, The angle range of the phase distance protection action is narrower than that of the phase distance protection action, taking 15 to 20 degrees, and the polarization voltage Take the positive sequence voltage at the protection installation location Operating voltage To protect the vector of voltage and current at the installation location, Z set It is the distance protection setting value.

[0030] An adaptive distance protection system, comprising:

[0031] Extraction module, used to extract transient time domain information of electrical quantities at the protection installation location;

[0032] The processing module is used to determine the fault direction characteristics by using the transient time domain information of the electrical quantity. When the positive direction is determined, the distance protection action range is expanded; when the reverse direction is determined, the distance protection action range is reduced.

[0033] Furthermore, the extraction module is used to

[0034] Use formula (1) to calculate the transient time domain information of voltage quantity,

[0035] Δu m(k) =u m(k) -u m(k-N) (1)

[0036] Among them, △u m(k) is the transient time domain information of voltage, u m(k) is the voltage sampling value of the protection device at the current moment, u m(k-N) is the voltage sampling value of the protection device one cycle ago, N is the number of sampling points in one cycle, and m represents phases a, b, and c or between phases ab, bc, and ca;

[0037] Use formula (2) to calculate the transient time domain information of current,

[0038] Δi m(k) =i m(k) -i m(k-N) (2)

[0039] Among them, Δi m(k) is the transient time domain information of the current, im(k) is the current sampling value of the protection device at the current moment, i m(k-N) It is the current sampling value of the protection device one cycle ago.

[0040] Furthermore, the processing module,

[0041] Used to determine that the fault direction is the positive direction according to the following criterion;

[0042] S m(k) =Δu m(k) Δi m(k) <0

[0043] Used to determine that the fault direction is the positive direction according to the following criterion;

[0044] S m(k) =Δu m(k) Δi m(k) >0

[0045] Among them, S m(k) is the constructed energy direction expression.

[0046] Furthermore, the processing module is used to expand the action range of the mho distance protection based on positive sequence voltage polarization to the range of the following formula:

[0047]

[0048] in, To expand the angle range of phase distance protection action, take 15~20°, polarization voltage Take the positive sequence voltage at the protection installation location Operating voltage To protect the vector of voltage and current at the installation location, Z set It is the distance protection setting value.

[0049] Furthermore, the processing module is used to narrow the action range of the mho distance protection based on positive sequence voltage polarization to the range of the following formula:

[0050]

[0051] in, The angle range of the phase distance protection action is narrower than that of the phase distance protection action, taking 15 to 20 degrees, and the polarization voltage Take the positive sequence voltage at the protection installation location Operating voltage To protect the vector of voltage and current at the installation location, Z set It is the distance protection setting value.

[0052] A computer-readable storage medium storing one or more programs, the one or more programs comprising instructions that, when executed by a computing device, cause the computing device to perform any of the methods described.

[0053] A computing device comprising:

[0054] One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include instructions for executing any of the methods described.

[0055] The beneficial effects achieved by the present invention are:

[0056] The present invention addresses the problem of abnormal distance protection operation at new energy stations or flexible direct current transmission lines. It uses transient time domain information of electrical quantities at the protection installation location to determine the fault direction and adaptively adopts distance protection elements with different protection ranges to ensure the correct operation of the distance protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a schematic flow diagram of the present invention;

[0058] Figure 2 This is a schematic diagram of additional states for positive direction faults;

[0059] Figure 3 This is a schematic diagram of the additional state of the reverse direction fault;

[0060] Figure 4 It is a distance relay based on positive sequence voltage polarization;

[0061] Figure 5 It is the operating range of the positive direction fault distance protection;

[0062] Figure 6 It is the operating range of the reverse direction fault distance protection;

[0063] Figure 7 is a schematic diagram of the simulation system;

[0064] Figure 8 It is a phase-to-phase fault in the positive direction near the flexible DC side, and the distance protection fails to operate;

[0065] Figure 9 The positive direction is determined based on transient time domain information;

[0066] Figure 10 It is the correct action for distance protection after expanding the range of action;

[0067] Figure 11 It is a busbar phase-to-phase fault on the system side, causing the distance protection to malfunction;

[0068] Figure 12 The reverse direction is determined based on transient time domain information;

[0069] Figure 13 It is to reduce the distance protection of the action range to ensure accurate non-action. DETAILED DESCRIPTION

[0070] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0071] like Figure 1 As shown, an adaptive distance protection method includes the following steps:

[0072] Step 1: Extract the transient time domain information of electrical quantities at the protection installation.

[0073] Obtaining transient time domain information of voltage:

[0074] Δu m(k) =u m(k) -u m(k-N)

[0075] Among them, △u m(k) is the transient time domain information of voltage, u m(k) is the voltage sampling value of the protection device at the current moment, u m(k-N) is the voltage sampling value of the protection device one cycle ago, N is the number of sampling points in one cycle, and m is between phases a, b, and c or between phases a, bc, and ca.

[0076] Similarly, the change in current sampling point is:

[0077] Δi m(k) =i m(k) -i m(k-N)

[0078] Among them, Δi m(k) is the transient time domain information of the current, i m(k) is the current sampling value of the protection device at the current moment, i m(k-N) is the current sampling value of the protection device one cycle ago, N is the number of sampling points in one cycle, and m is between phases a, b, and c or between phases a, bc, and ca.

[0079] Step 2: Use the transient time domain information of electrical quantities to determine the fault direction characteristics.

[0080] for Figure 2 The positive direction fault shown in the fault additional state has:

[0081] Δu m(k) =-Δi m(k) Zs

[0082] so:

[0083] S m(k) =Δu m(k) Δi m(k) =-Δi 2 m(k) Z S <0

[0084] That is, the positive direction criterion:

[0085] S m(k) =Δu m(k) Δi m(k) <0

[0086] for Figure 3 The reverse direction fault shown, in the fault additional state, has:

[0087] Δu m(k) =Δi m(k) Z R >0

[0088] so:

[0089] S m(k) =Δu m(k) Δi m(k) =Δi 2 m(k) Z R >0

[0090] That is, the reverse direction criterion:

[0091] S m(k) =Δu m(k) Δi m(k) >0

[0092] Step 3: When the positive direction is determined, the distance protection action range is expanded, and the action range of the traditional mho distance protection based on positive sequence voltage polarization is expanded to:

[0093]

[0094] Among them, the polarization voltage Take positive sequence voltage Operating voltage To protect the vector of voltage and current at the installation location, Z set It is the distance protection setting value. Generally, it is taken as 15°~20°.

[0095] The distance protection action range corresponding to the above formula is as follows: Figure 5 As shown, Figure 4Compared with the traditional mho distance protection based on positive sequence voltage polarization, the upper and lower boundaries of the action range are increased by Distance relay with apple-shaped characteristics.

[0096] Step 4: When the reverse direction is determined, the distance protection action range is narrowed, and the action range of the traditional mho distance protection based on positive sequence voltage polarization is narrowed to:

[0097]

[0098] Among them, the polarization voltage Take positive sequence voltage Operating voltage To protect the vector of voltage and current at the installation location, Z set It is the distance protection setting value. Generally, it is taken as 15°~20°.

[0099] The distance protection action range corresponding to the above formula is as follows: Figure 6 As shown, Figure 4 Compared with the traditional mho distance protection based on positive sequence voltage polarization, the upper and lower boundaries of the action range are reduced by Distance relay with lens-type characteristics.

[0100] In combination with the above method, the following simulation example is provided for a certain wind power flexible direct current transmission system model:

[0101] like Figure 7 As shown in Figure 1, a 500kV line model of a wind farm transmitting electricity via a flexible direct current (FDC) was constructed in the RTDS. Five internal and external fault points, F1 to F5, were set in the model. System and line parameters on both sides of the line are shown in Table 1. Line protection device A, equipped with conventional mho distance protection based on positive-sequence voltage polarization, and line protection device B, equipped with the improved distance protection proposed in this patent, were connected to both sides of the line.

[0102] Table 1 System impedance and line parameters

[0103]

[0104]

[0105] The above fault points were tested for various fault types, and the distance protection action results were shown in Table 2.

[0106] Table 2 Distance protection action

[0107]

[0108]

[0109] From the distance protection operation status in Table 2, it can be seen that when a phase-to-phase fault occurs at the positive direction outlet of the flexible DC system on the M side, the distance protection of protection device A refuses to operate; when a busbar fault occurs on the N side of the system, the distance protection malfunctions, but the protection device B operates normally.

[0110] Further analysis shows that for single-phase grounding or phase-to-phase grounding faults inside and outside the zone, since the zero-sequence network is relatively independent, the zero-sequence component is not affected by the power supply, and the direction of the zero-sequence current meets the positive direction condition, the distance protection of devices A and B can operate correctly.

[0111] When a phase-to-phase fault occurs at the positive output of the flexible DC system at point F2, the fault current is limited and the phase is controlled due to the control strategy of the flexible DC system, causing the distance relay of device A to fail to operate ( Figure 8 The positive direction criterion of transient time domain information of device B satisfies the condition ( Figure 9 ), the distance protection with expanded action range can operate correctly and remove the fault ( Figure 10 ).

[0112] When a phase-to-phase fault occurs at the back busbar on the system side at point F5, the fault current is still provided by the flexible DC side. However, the fault current is limited and the phase is controlled due to the control strategy of the flexible DC system, which causes the distance relay of device A to malfunction ( Figure 11 ). The reverse direction criterion of transient time domain information of device B satisfies the condition ( Figure 12 ), the distance protection of the narrow action range is accurate and does not act ( Figure 13 ).

[0113] Accordingly, the present invention also provides an adaptive distance protection system, comprising:

[0114] Extraction module, used to extract transient time domain information of electrical quantities at the protection installation location;

[0115] The processing module is used to determine the fault direction characteristics by using the transient time domain information of the electrical quantity. When the positive direction is determined, the distance protection action range is expanded; when the reverse direction is determined, the distance protection action range is reduced.

[0116] The extraction module is used to

[0117] Use formula (1) to calculate the transient time domain information of voltage quantity,

[0118] Δu m(k) =u m(k) -u m(k-N) (1)

[0119] Among them, △u m(k) is the transient time domain information of voltage, u m(k) is the voltage sampling value of the protection device at the current moment, um(k-N) is the voltage sampling value of the protection device one cycle ago, N is the number of sampling points in one cycle, and m represents phases a, b, and c or between phases ab, bc, and ca;

[0120] Use formula (2) to calculate the transient time domain information of current,

[0121] Δi m(k) =i m(k) -i m(k-N) (2)

[0122] Among them, Δi m(k) is the transient time domain information of the current, i m(k) is the current sampling value of the protection device at the current moment, i m(k-N) It is the current sampling value of the protection device one cycle ago.

[0123] The processing module,

[0124] Used to determine that the fault direction is the positive direction according to the following criterion;

[0125] S m(k) =Δu m(k) Δi m(k) <0

[0126] Used to determine that the fault direction is the positive direction according to the following criterion;

[0127] S m(k) =Δu m(k) Δi m(k) >0

[0128] Among them, S m(k) is the constructed energy direction expression.

[0129] The processing module is used to expand the operating range of the mho distance protection based on positive sequence voltage polarization to the range of the following formula:

[0130]

[0131] in, To expand the angle range of phase distance protection action, take 15~20°, polarization voltage Take the positive sequence voltage at the protection installation location Operating voltage To protect the vector of voltage and current at the installation location, Z set It is the distance protection setting value.

[0132] The processing module is used to narrow the action range of the mho distance protection based on positive sequence voltage polarization to the range of the following formula:

[0133]

[0134] in, The angle range of the phase distance protection action is narrower than that of the phase distance protection action, taking 15 to 20 degrees, and the polarization voltage Take the positive sequence voltage at the protection installation location Operating voltage To protect the vector of voltage and current at the installation location, Z set It is the distance protection setting value.

[0135] The present invention also provides a computer-readable storage medium storing one or more programs, wherein the one or more programs include instructions, which, when executed by a computing device, enable the computing device to perform any of the methods described above.

[0136] The present invention also provides a computing device, comprising:

[0137] One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include instructions for executing any of the methods described.

[0138] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0139] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0140] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0141] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0142] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An adaptive distance protection method, characterized in that: include: Extract transient time domain information of electrical quantities at protection installation locations; Use the transient time domain information of electrical quantities to determine the fault direction characteristics. When the positive direction is determined, the distance protection action range is expanded. When the opposite direction is determined, the range of distance protection action is reduced; The extraction of transient time domain information of electrical quantities at the protection installation location includes: Using formula (1) to calculate the transient time domain information of voltage, (1)； in, is the transient time domain information of voltage, is the voltage sampling value of the protection device at the current moment, is the voltage sampling value of the protection device one cycle ago, N is the number of sampling points for one cycle, m Indicates a, b, c phases or ab, bc, ca phases; Use formula (2) to calculate the transient time domain information of current, (2)； in, is the transient time domain information of the current, is the current sampling value of the protection device at the current moment, It is the current sampling value of the protection device one cycle ago; The criterion for the positive direction is: ； The criterion for the reverse direction is: ； in, is the constructed energy direction expression; The expanded distance protection action range includes: The operating range of the mho distance protection based on positive sequence voltage polarization is expanded to the following range: ； The narrowing of the distance protection action range includes: The operating range of the mho distance protection based on positive sequence voltage polarization is narrowed to the following range: ； in, To expand the angle range of phase distance protection action, take 15~20°, polarization voltage Take the positive sequence voltage at the protection installation location ; Working voltage , 、 To protect the voltage and current vectors at the installation location, It is the distance protection setting value.

2. An adaptive distance protection system, characterized in that: include: Extraction module, used to extract transient time domain information of electrical quantities at the protection installation location; The processing module is used to determine the fault direction characteristics by using the transient time domain information of the electrical quantity. When the positive direction is determined, the distance protection action range is expanded; when the reverse direction is determined, the distance protection action range is reduced; The extraction module is used to Using formula (1) to calculate the transient time domain information of voltage, (1)； in, is the transient time domain information of voltage, is the voltage sampling value of the protection device at the current moment, is the voltage sampling value of the protection device one cycle ago, N is the number of sampling points for one cycle, m Indicates a, b, c phases or ab, bc, ca phases; Use formula (2) to calculate the transient time domain information of current, (2)； in, is the transient time domain information of the current, is the current sampling value of the protection device at the current moment, It is the current sampling value of the protection device one cycle ago; The processing module is used to Used to determine that the fault direction is the positive direction according to the following criterion; ； Used to determine that the fault direction is the reverse direction according to the following criterion; ； in, is the constructed energy direction expression; The processing module is used to expand the operating range of the mho distance protection based on positive sequence voltage polarization to the range of the following formula: ； The processing module is used to narrow the action range of the mho distance protection based on positive sequence voltage polarization to the range of the following formula: ； in, To expand the angle range of phase distance protection action, take 15~20°, polarization voltage Take the positive sequence voltage at the protection installation location ; Working voltage , 、 To protect the voltage and current vectors at the installation location, It is the distance protection setting value.

3. A computer-readable storage medium storing one or more programs, characterized in that: The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform the method of claim 1 .

4. A computing device, characterized in that include, One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs comprising instructions for executing the method of claim 1.

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