CN117277232B - Circuit distance protection method and device, electronic equipment and readable storage medium - Google Patents

Circuit distance protection method and device, electronic equipment and readable storage medium Download PDF

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Publication number
CN117277232B
CN117277232B CN202311048520.5A CN202311048520A CN117277232B CN 117277232 B CN117277232 B CN 117277232B CN 202311048520 A CN202311048520 A CN 202311048520A CN 117277232 B CN117277232 B CN 117277232B
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data
determining
vertex
value
angle
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CN117277232A (en
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侯勇
刘虎林
叶海
倪腊琴
韩俊
苏柏松
刘中平
郑晓冬
邰能灵
晁晨栩
张怀宇
谢雅馨
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East China Branch Of State Grid Corp ltd
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East China Branch Of State Grid Corp ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current

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Abstract

The application relates to the technical field of relay protection of power systems and discloses a distance protection method and device of a circuit, electronic equipment and a readable storage medium; the method comprises the following steps: acquiring voltage data and current data of a grid-connected point installation protection place; if the circuit fault type is a two-phase short circuit fault, adjusting the negative sequence component of the current data based on the voltage data, the current data, the inverter current data of the circuit and the opposite system impedance angle so that the difference between the inverter negative sequence impedance angle and the opposite system impedance angle is smaller than or equal to a preset threshold value; determining an additional impedance angle of the measured impedance of the grid-connected point installation protection position according to the inversion power supply current data and the fault point non-fault phase negative sequence current data of the line; adjusting the action area of the circuit according to the additional impedance angle to obtain an adjusted action area; and generating a protection action instruction according to the measured impedance and the adjusted action area. The distance protection method can accurately detect the short-circuit faults of the inner phase and the outer phase of the reaction zone.

Description

Circuit distance protection method and device, electronic equipment and readable storage medium
Technical Field
The disclosure relates to the technical field of relay protection of power systems, and in particular relates to a distance protection method and device for a circuit, electronic equipment and a readable storage medium.
Background
Inverse new energy stations (Inverter-INTERFACED RENEWABLE POWER PLANT, IIRPP) are heavily connected to the grid as an important form of new energy utilization.
The distance protection can reflect the fault distance, is a line protection scheme which reflects the impedance between a fault point and a protection installation place through an impedance relay and compares the impedance with a setting value, and is widely used as main protection and backup protection of a power transmission line. In the traditional scene based on synchronous rotation power supply, the additional impedance angle of the measured impedance is close to 0 degrees, and the quadrilateral characteristic impedance relay in the related technology can effectively avoid distance protection rejection and misoperation caused by transition resistance. However, when a nonmetallic short-circuit fault occurs, the measured impedance contains additional impedance, and because the inverter power supply is different from the synchronous rotating power supply, the fault characteristics are affected by the fault condition and the control strategy, and the amplitude, the phase and the sequence impedance of the short-circuit current are controlled, so that the conventional distance protection method cannot correctly identify the two-phase short-circuit fault, and therefore, the conventional distance protection scheme has great failure risk when applied to IIRPP outgoing lines.
Disclosure of Invention
Aiming at the situation, the embodiment of the application provides a distance protection method, a device, electronic equipment and a readable storage medium of a circuit, aiming at solving the problem that the traditional distance protection scheme cannot correctly identify the two-phase short-circuit fault because the fault characteristic of an inverter is influenced by fault conditions and control strategies when the non-metal two-phase short-circuit fault occurs.
In a first aspect, an embodiment of the present application provides a method for protecting a distance of a line, where the method includes:
Acquiring voltage data and current data of a grid-connected point installation protection place;
If the circuit fault type is a two-phase short circuit fault, adjusting a negative sequence component of the current data based on the voltage data, the current data, the inverter current data of the circuit and the opposite-side system impedance angle so that the difference between the inverter negative sequence impedance angle and the opposite-side system impedance angle is smaller than or equal to a preset threshold value;
Determining an additional impedance angle of the measured impedance of the grid-connected point installation protection position according to the inverter power supply current data and the fault point non-fault phase negative sequence current data of the line;
according to the additional impedance angle, an action area of the circuit is adjusted to obtain an adjusted action area;
and generating a protection action instruction according to the measured impedance and the adjusted action area.
In a second aspect, an embodiment of the present application further provides a distance protection device for a line, where the device includes:
the acquisition module is used for acquiring voltage data and current data of the grid-connected point installation protection place;
The negative sequence impedance stabilizing module is used for adjusting the negative sequence component of the current data based on the voltage data, the current data, the inverter current data of the circuit and the opposite side system impedance angle if the circuit fault type is a two-phase short circuit fault, so that the difference between the inverter negative sequence impedance angle and the opposite side system impedance angle is smaller than or equal to a preset threshold value;
The additional impedance angle determining module is used for determining an additional impedance angle of the measured impedance of the grid-connected point installation protection position according to the inverter power supply current data and the fault point non-fault phase negative sequence current data of the line;
The region adjustment module is used for adjusting the action region of the circuit according to the additional impedance angle to obtain an adjusted action region;
and the protection instruction generation module is used for generating a protection action instruction according to the measured impedance and the adjusted action area.
In a third aspect, an embodiment of the present application further provides an electronic device, including: a processor; and a memory arranged to store computer executable instructions that, when executed, cause the processor to perform the steps of the distance protection method of the line described above.
In a fourth aspect, embodiments of the present application also provide a computer-readable storage medium storing one or more programs that, when executed by an electronic device including a plurality of application programs, cause the electronic device to perform the steps of the distance protection method of a line described above.
The above at least one technical scheme adopted by the embodiment of the application can achieve the following beneficial effects:
according to the distance protection method for the circuit, provided by the embodiment of the application, voltage data and current data of a grid-connected point installation protection place are obtained; judging the circuit fault type as a two-phase short circuit fault, if yes, adjusting the negative sequence component of the current data based on the voltage data, the current data, the inverter current data of the circuit and the opposite system impedance angle, so that the difference between the inverter negative sequence impedance angle and the opposite system impedance angle is smaller than or equal to a preset threshold value; determining an additional impedance angle of the measured impedance of the grid-connected point installation protection position according to the inversion power supply current data and the fault point non-fault phase negative sequence current data of the line; according to the additional impedance angle, the action area of the circuit is adjusted to obtain an adjusted action area; and finally, generating a protection action instruction according to the measured impedance and the adjusted action area.
It can be seen that the application adjusts the detected negative sequence component of the current data, so that the negative sequence impedance angle of the inverter power supply can be kept constant without being influenced by the fault position and the transition resistance during the two-phase short-circuit fault of the circuit, and is approximately equal to the impedance angle of the opposite system, and because the impedance angles at two sides of the fault point are approximately equal, the additional impedance angle can be accurately calculated only by using the local quantity, and the action area of the circuit is adaptively adjusted by using the additional impedance angle, thereby solving the problems of the protection rejection of the distance between the inversion side when the IIRPP outgoing circuit generates the nonmetallic two-phase short-circuit fault and the protection misoperation of the distance between the inversion side when the lower circuit of the outgoing circuit generates the nonmetallic two-phase short-circuit fault in the related technology, and the internal and external two-phase short-circuit faults in the correct reaction area can be accurately set; meanwhile, the protection scheme provided by the embodiment of the application only utilizes local measurement quantity, does not depend on communication, and improves the reaction speed and efficiency of distance protection; in addition, the protection scheme provided by the embodiment of the application only needs to adjust the negative sequence current and does not influence the positive sequence current to carry out reactive power support, so that the protection scheme can adapt to different IIRPP reactive power support strategies, accords with the grid-connected technical specification of a new energy station, and promotes the high-quality absorption of the new energy.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute a limitation on the application. In the drawings:
FIG. 1 is a schematic diagram of an operational area of a quadrilateral characteristic impedance relay provided by an embodiment of the present application;
FIG. 2 is a schematic diagram of an IEEE14 node improvement system in accordance with an embodiment of the present application;
Fig. 3 is a schematic circuit diagram illustrating a two-phase short-circuit fault of a sending line according to an embodiment of the present application;
Fig. 4 is a schematic flow chart of a distance protection method of a circuit according to an embodiment of the present application;
Fig. 5 is a schematic diagram of a negative sequence impedance angle of a stabilized inverter according to an embodiment of the present application;
fig. 6 is a schematic diagram of a composite sequence network when a two-phase short-circuit fault occurs in a line according to an embodiment of the present application;
FIG. 7 is a schematic diagram of a build adjusted action region provided by an embodiment of the present application;
FIG. 8 illustrates a schematic diagram of constructing a final action region provided by an embodiment of the present application;
fig. 9 is a schematic flow chart of a distance protection method of a circuit according to another embodiment of the present application;
Fig. 10 shows a schematic structural diagram of a distance protection device for a circuit according to an embodiment of the present application;
Fig. 11 shows a schematic structural diagram of an electronic device according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be clearly and completely described below with reference to specific embodiments of the present application and corresponding drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The following describes in detail the technical solutions provided by the embodiments of the present application with reference to the accompanying drawings.
IIRPP is largely connected to the grid as an important form of new energy utilization. The distance protection can reflect the fault distance, is a line protection scheme which reflects the impedance between a fault point and a protection installation place through an impedance relay and compares the impedance with a setting value, and is widely used as main protection and backup protection of a power transmission line. In the traditional scene mainly comprising synchronous rotating power supply, the additional impedance angle of the measured impedance is close to 0 degrees, and the quadrilateral characteristic impedance relay can effectively avoid distance protection rejection and misoperation caused by transition resistance. Specifically, the measured impedance of the impedance relay may be written in a complex form, so that the complex plane may be used to analyze the operational characteristics of the relay. Fig. 1 is a schematic diagram showing an operation region of a quadrilateral characteristic impedance relay according to an embodiment of the present application. As shown in fig. 1, the action area of the impedance relay can be regarded as being composited by the action areas of the quasi-reactance relay line AB, the quasi-resistance relay line BC, and the power direction relay broken line AOC with a range of less than 180 °. The three characteristic relays form an AND gate output, and can have the capability of tolerating transition resistance and avoiding load. In the traditional distance protection scheme, when the measured impedance Z m of the impedance relay is positioned in the quadrangle, judging that the fault exists in the area, and protecting the action; when the protection device is positioned outside the quadrangle, the protection device does not act.
However, when a nonmetallic short-circuit fault occurs, the measured impedance of the impedance relay will include additional impedance, and because the inverter power supply is different from the synchronous rotating power supply, the fault characteristics are affected by the fault condition and the control strategy, the amplitude, the phase and the sequence impedance of the short-circuit current are controlled, so that the conventional distance protection method cannot correctly identify the two-phase short-circuit fault, specifically, fig. 2 shows a schematic diagram of the IEEE14 node improvement system provided by the embodiment of the present application, where R 87 is a grid-connected point installation protection place, S1, S2, S3, S6 are rotating power supplies, T56, T49, T47 are transformers, 1,2,3,4, 5, 6,7,8,9, 10, 11, 12, 13, 14 are bus numbers of lines, L79 is a lower line, L87 is a sending line, and IIRPP is collected to a 220kV step-up transformer grid through a 35kV ac line.
Fig. 3 is a schematic circuit diagram of a sending line according to an embodiment of the present application when a two-phase short circuit fault occurs. For convenience of description, the present application is described by taking an AB two-phase short-circuit fault as an example. In fig. 3, the equivalent system is the system structure except the outgoing line and IIRPP in fig. 2, Z s is the equivalent impedance of the opposite system, α is the fault location, Z 87 is the impedance of L 87, R ph is the phase-to-phase transition resistance, subscripts A, B, L and R respectively represent the a phase, the B phase, the local inverter side and the opposite side electric quantities, I AR is the opposite side a phase current, I BR is the opposite side B phase current, I AF is the fault point a phase current, I AL is the local inverter side a phase current, and I BL is the local inverter side B phase current. In connection with fig. 3, the measured impedance Z m of the AB phase distance relay at R 87 can be determined according to the following equation (1):
Wherein, U AL is a local inverter power side a-phase voltage, U BL is a local inverter power side B-phase voltage, and Z add is an additional impedance.
Because IIRPP short-circuit current amplitude is limited and is influenced by IIRPP reactive support strategy, short-circuit current phase is controlled, Z add amplitude is larger and an additional impedance angle is formedPossibly deviating seriously from 0 deg., the distance protection at R 87 is very subject to rejection. Similarly, when a two-phase short circuit fault occurs in the lower line L 79 of the outgoing line, there is a risk of malfunction in the distance protection at the R 87. The conventional distance protection scheme is applied with a great risk of failure when IIRPP is sent out of the line. Based on the above, the application provides a distance protection method for a circuit, and the embodiment of the application adjusts the detected negative sequence component of current data, so that the negative sequence impedance angle of an inverter power supply can be kept constant without being influenced by a fault position and a transition resistance during the two-phase short-circuit fault of the circuit, and is approximately equal to the impedance angle of a contralateral system; meanwhile, the protection scheme provided by the embodiment of the application only utilizes local measurement quantity, does not depend on communication, and improves the reaction speed and efficiency of distance protection; in addition, the protection scheme provided by the embodiment of the application only needs to adjust the negative sequence current and does not influence the positive sequence current to carry out reactive power support, so that the protection scheme can adapt to different IIRPP reactive power support strategies, accords with the grid-connected technical specification of a new energy station, and promotes the high-quality absorption of the new energy. The present application will be described in detail with reference to specific examples.
Fig. 4 is a schematic flow chart of a distance protection method for a circuit according to an embodiment of the present application, and as can be seen from fig. 4, the embodiment of the present application at least includes steps S401 to S405:
Step S401: and acquiring voltage data and current data of the grid-connected point installation protection place.
Step S402: and if the circuit fault type is a two-phase short circuit fault, adjusting the negative sequence component of the current data based on the voltage data, the current data, the inverter current data of the circuit and the opposite system impedance angle so that the difference between the inverter negative sequence impedance angle and the opposite system impedance angle is smaller than or equal to a preset threshold value.
In this step, it may be determined whether the line fails and whether the circuit failure type of the line is a two-phase short circuit failure. In an actual application scene, when a line has a fault, the voltage of any phase at the grid-connected point installation protection position is lower than a preset value, for example, the preset value is set to be 0.9p.u., the voltage value of the phase A in the voltage data of the grid-connected point installation protection position is set to be 0.8p.u., the voltage value of the phase B is set to be 1.0p.u., the voltage value of the phase C is set to be 0.9p.u., and the voltage value of the phase A is set to be less than 0.9p.u., so that the line has the fault can be judged. The circuit fault types of the circuit comprise single-phase ground fault, two-phase short circuit fault, two-phase ground short circuit fault, three-phase short circuit fault and the like, when the fault occurs, different fault types correspond to different manifestations, for example, aiming at the two-phase short circuit fault, when the circuit has A, B-phase short circuit fault, the current of the C phase is 0, the voltages of the A phase and the B phase are the same, and the directions of the A phase and the B phase are opposite, so that whether the circuit fault type of the circuit is the two-phase short circuit fault can be judged according to the voltage and the current characteristics of each phase.
After the two-phase short circuit fault of the line is determined, the negative sequence component of the current data can be adjusted according to the voltage data, the current data, the inversion power supply current data of the line and the opposite side system impedance angle, so that the difference between the inversion power supply negative sequence impedance angle and the opposite side system impedance angle is smaller than or equal to a preset threshold value. Specifically, in some embodiments of the present application, in the above method, the adjusting the negative sequence component of the current data based on the voltage data, the current data, the inverter current data of the line, and the opposite system impedance angle to make the difference between the inverter negative sequence impedance angle and the opposite system impedance angle smaller than or equal to a preset threshold value includes: determining negative sequence current data of the inverter power supply according to the power supply data and the inverter power supply current data; coordinate transformation is carried out on the negative sequence component of the voltage data and the negative sequence component of the current data respectively to obtain a first voltage component and a second voltage component, and a first current component and a second current component; performing logic operation on the negative sequence current data, the first voltage component, the second voltage component and the opposite side system impedance angle of the inverter power supply to obtain a first current component preset value and a second current component preset value; and adjusting the first current component by using a first current component preset value, and adjusting the second current component by using the first current component preset value so that the difference between the negative sequence impedance angle of the inverter power supply and the opposite system impedance angle is smaller than or equal to a preset threshold value.
In this embodiment, the negative sequence current data of the inverter can be determined according to the current data of the grid-connected point installation protection place and the current data of the inverter. Specifically, in some embodiments of the present application, in the above method, the determining the negative sequence current data of the inverter power supply according to the current data and the current data of the inverter power supply includes: determining the absolute value of the phase difference between the positive sequence current and the negative sequence current of the target phase to obtain phase difference data, wherein the target phase is the phase with the minimum phase difference between the positive sequence current and the negative sequence current in the current data; multiplying the positive sequence component of the inversion power supply current data and the sine value of the phase difference data to obtain first intermediate data; adding the square of the first intermediate data and the square of the maximum phase current data of the inversion power supply current data to obtain second intermediate data; multiplying the positive sequence component of the inversion power supply current data and the cosine value of the phase difference data to obtain third intermediate data; and determining the square root of the second intermediate data and the difference between the second intermediate data and the third intermediate data to obtain negative sequence current data of the inverter.
In this embodiment, a phase with the smallest phase difference between the positive sequence current and the negative sequence current in the current data of the grid-connected point installation protection part may be recorded as a target phase, and the absolute value of the phase difference between the positive sequence current and the negative sequence current of the target phase may be calculated to obtain the phase difference. According to the cosine law, the positive sequence component of the inverted power supply current data can be multiplied by the sine value of the phase difference to obtain first intermediate data; the square of the first intermediate data is added with the square of the maximum phase current amplitude of the inversion power supply data to obtain second intermediate data; multiplying the positive sequence component of the inversion power supply current data by the cosine value of the phase difference to obtain third intermediate data; and subtracting the square root of the second intermediate data from the third intermediate data to obtain the negative sequence current amplitude of the inverter power supply. Specifically, the negative sequence current amplitude I - of the inverter can be determined according to the following formula (2):
Wherein I + is the positive sequence component of the inverted supply current data, I max is the maximum phase current amplitude of the inverter power data, which is the phase difference. Illustratively, the positive sequence component I + of the inverter supply current data is 1, phase difference/>90 °, The maximum phase current amplitude I max of the inverter data is 2, I + =1,/>By substituting I max =2 into the above formula (2), the negative sequence current amplitude I - of the inverter can be obtained as/>
Fig. 5 shows a schematic diagram of a negative sequence impedance angle of a stabilized inverter power supply provided by the embodiment of the application, as shown in fig. 5, voltage data u abc and current data i abc at a grid-connected point installation protection place are converted into a two-phase rotation coordinate system dq coordinate system by using a three-phase stationary coordinate system abc coordinate system where a voltage data negative sequence component u abc - and a current data negative sequence component i abc - are located through a measuring unit by using an output omega of a phase-locked loop, and u abc - and i abc - are respectively filtered by using a wave trap with a frequency of 100Hz to obtain u d -、uq -、id -、iq - to replace corresponding u abc -、iabc -, so that coordinate transformation of the negative sequence component of the voltage data and the negative sequence component of the current data is realized, and a first voltage component u d -, a second voltage component u q -, a first current component i d - and a second current component i q - are obtained. Similarly, the output ω of the phase-locked loop can be used to transform the three-phase stationary coordinate system abc coordinate system in which the positive sequence component u abc + of the voltage data and the positive sequence component i abc + of the current data are located into the two-phase rotating coordinate system dq coordinate system to obtain u d +、uq +、id +、iq +.
And then, carrying out logic operation on the negative sequence current amplitude, the first voltage component, the second voltage component and the opposite side system impedance angle of the inverter power supply to obtain a first current component preset value and a second current component preset value. Specifically, in some embodiments of the present application, in the above method, performing a logic operation on the negative sequence current data, the first voltage component, the second voltage component, and the opposite side system impedance angle of the inverter power supply to obtain a first current component preset value and a second current component preset value, including: determining the ratio of the second voltage component to the first voltage component to obtain fourth intermediate data; determining the difference between the arctangent value of the fourth intermediate data and the impedance angle of the opposite system to obtain fifth intermediate data; determining the product of the negative sequence current data of the inverter and the cosine value of the fifth intermediate data to obtain a first current component preset value; and determining the product of the negative sequence current data of the inverter and the sine value of the fifth intermediate data to obtain a second current component preset value.
In this embodiment, a ratio of the second voltage component to the first voltage component may be determined to obtain fourth intermediate data; obtaining an arctangent value of the fourth intermediate data, and subtracting the arctangent value from the impedance angle of the opposite system to obtain fifth intermediate data; and multiplying the negative sequence current data of the inverter power supply by the cosine value of the fifth intermediate data to obtain a first current component preset value. Taking the first formula in the following equation set (1) as the formula (3), specifically, the first current component preset value i d-ref - may be determined according to the formula (3):
Wherein, Is the negative sequence impedance angle of the inverter.
And multiplying the negative sequence current data of the inverter power supply by the sine value of the fifth intermediate data to obtain a second current component preset value. Taking the second formula in the above equation set (1) as formula (4), specifically, the second current component preset value i q-ref - may be determined according to formula (4):
Fig. 6 shows a schematic diagram of a composite sequence network when a two-phase short-circuit fault occurs in a line according to an embodiment of the present application. In fig. 6, the superscript-represents the negative sequence component, the superscript + represents the positive sequence component, Z S + is the equivalent positive sequence impedance of the contralateral system, Z S - is the equivalent negative sequence impedance of the contralateral system, Z T + is the positive sequence impedance of the main transformer, Z T - is the negative sequence impedance of the main transformer, Z IBS - is the negative sequence impedance of the inverter, E SC is the equivalent voltage source of the contralateral system C, I CL + is the C-phase positive sequence current of the local inverter, I CL - is the C-phase negative sequence current of the local inverter, U CL + is the C-phase positive sequence voltage of the local inverter, U CL - is the C-phase negative sequence voltage of the local inverter, Z 87 + is the line positive sequence impedance, and Z 87 - is the line negative sequence impedance. I CF + is the fault point C phase positive sequence current, and I CF - is the fault point C phase negative sequence current.
Referring to fig. 6, the measured impedance Z AB of the AB phase-to-phase distance relay at the grid-tie point installation protection site may be determined according to the following equation (5):
In practice, as shown in FIG. 5, the negative sequence impedance angle of the inverter can be made In the negative sequence control system, i d - measured actually can be adjusted by i d-ref -, i q - measured actually can be adjusted by i q-ref - so that i q -、id - is respectively closer to i q-ref - and i d-ref -, u q -、ud - is controlled by linear controllers PI and ωl, and finally negative sequence voltage u abc-ref - is obtained and fused with output u abc-ref + of the positive sequence control system to obtain u abc-ref, so that the difference of the impedance angles at two sides of the fault point in the negative sequence network of fig. 6 is smaller than or equal to a preset threshold, for example, the preset threshold is 1 DEG even if the two sides of the fault point in the negative sequence network: the negative sequence impedance angle and the opposite system impedance angle of the inverter are approximately equal, and thus the phase relationship between I CF + and I CL - as shown in the following formula (6) can be obtained:
arg (I CL -)＝arg(ICF +) to 180℃formula (6);
where arg () represents the phase of the phasor.
Therefore, the I CF + in the formula (5) can be replaced by the formula (6), so that the local measurement quantity such as I AL、IBL、ICL - can be directly used for directly obtaining the additional impedance angle. By way of example, I - is 2,At 15 °, u q - is 2,u d - and 2, the result is obtained according to the above formula (3) and formula (4). u q -/ud - is 1, arctan (u q -/ud -) is 45 °, then i d-ref - is/>I q-ref - is 1.
Step S403: and determining an additional impedance angle of the measured impedance of the grid-connected point installation protection position according to the inversion power supply current data and the fault point non-fault phase negative sequence current data of the line.
As can be seen from the foregoing steps, when the negative sequence impedance angle of the inverter power supply on both sides of the fault point in the negative sequence network is approximately equal to the opposite system impedance angle, a fixed phase relationship exists between I CF + and I CL -, so that the above equation (5) and equation (6) are combined, and in this step, the additional impedance angle of the measured impedance at the grid-connected point installation protection can be determined according to the phase angle of the inverter power supply current data and the phase angle of the fault point non-fault phase negative sequence current data of the line.
Specifically, in some embodiments of the present application, in the above method, the determining, according to the inverter current data and the fault point non-fault phase negative sequence current data of the line, an additional impedance angle of the measured impedance at the grid-connected point installation protection includes: determining a current difference between two fault phases in the inverter current data; determining the ratio of the non-fault phase negative sequence current to the current difference in the inverter power supply current data; and determining the sum of the phase angle of the ratio and the preset angle to obtain the additional impedance angle.
In this embodiment, the current difference between two fault phases in the inverter current data may be determined first, that is, the a-phase current and the B-phase current of the inverter current data may be subtracted first to obtain the current difference; dividing the non-fault phase negative sequence current, namely the C phase negative sequence current, in the inverter power supply current data by the current difference to obtain a ratio; the phase angle of the ratio is determined and the obtained phase angle is added to a preset angle, for example, the preset angle is 90 degrees, so that an additional impedance angle is obtained. Specifically, in combination of the above formula (5) and formula (6), the additional impedance angle can be determined according to the following formula (7)
Illustratively, I CL - is 290, I AL-IBL is 2 45, thenIs 135 deg..
Step S404: and adjusting the action area of the circuit according to the additional impedance angle to obtain an adjusted action area.
After the additional impedance angle is calculated, the action area of the circuit can be adjusted according to the additional impedance angle, and the adjusted action area is obtained. Specifically, in some embodiments of the present application, in the above method, the adjusting the action area of the line according to the additional impedance angle to obtain the adjusted action area includes: taking the intersection point of the first impedance relay direction line and the second impedance relay direction line as a first vertex; taking the intersection point of the first impedance relay direction line and the reactance line as a second vertex; taking the intersection point of the reactance line and the resistance line as an initial third vertex; taking the intersection point of the resistance wire and the direction wire of the second impedance relay as an initial fourth vertex, wherein a quadrilateral area formed by the first vertex, the second vertex, the initial third vertex and the initial fourth vertex is an action area of the circuit; a line segment formed by connecting the second vertex and the initial third vertex rotates around the second vertex by an angle of an additional impedance angle to obtain a line segment formed by connecting the second vertex and the third vertex; a line segment formed by connecting the first vertex and the initial fourth vertex is rotated around the first vertex by an additional impedance angle to obtain a line segment formed by connecting the first vertex and the fourth vertex; and taking a quadrilateral area formed by the first vertex, the second vertex, the third vertex and the fourth vertex as an adjusted action area.
FIG. 7 is a schematic diagram of a build adjusted action region provided by an embodiment of the present application. The present embodiment is exemplarily described below with reference to fig. 7.
An intersection point of the first impedance relay direction line and the second impedance relay direction line can be used as a first vertex O; taking the intersection point of the direction line of the first impedance relay and the reactance line as a second vertex A; taking the intersection point of the reactance line and the resistance line as an initial third vertex B1; and taking an intersection point of the resistance wire and the second impedance relay direction wire as an initial fourth vertex C1, wherein a quadrilateral area formed by the first vertex, the second vertex, the initial third vertex and the initial fourth vertex is an action area of the circuit.
A segment connecting the second vertex and the initial third vertex, i.e. segment AB1, rotates around vertex AObtaining a line segment AB2 formed by connecting the second vertex and the third vertex B2; a segment connecting the first vertex and the initial fourth vertex, segment OC1, rotates around vertex O/>A line segment formed by connecting the first vertex and the fourth vertex C2, i.e., a line segment OC2, is obtained.
Finally, a quadrangular region formed by the vertex O, the vertex a, the vertex B2, and the vertex C2 is set as the post-adjustment operation region.
Step S405: and generating a protection action instruction according to the measured impedance and the adjusted action area.
After the adjusted action region is obtained, a protection action command may be generated based on the measured impedance and the adjusted action region. For example, if the measured impedance is in the adjusted action area, generating a protection action instruction and sending out a tripping signal; if the measured impedance is outside the adjusted operation region, no protection operation command is generated.
Specifically, in some embodiments of the present application, in the above method, the generating a protection action command according to the measured impedance and the adjusted action area includes: if the measured impedance meets the first criterion, generating a protection action instruction; the impedance angle of the line is a line segment formed by connecting the first vertex and the second vertex, the included angle between the impedance angle and the positive semi-axis of the horizontal axis is the ordinate data of the second vertex, and the impedance setting value is the length of the line segment formed by connecting the first vertex and the fourth vertex; the first criterion is determined according to the following method: measuring the imaginary part data of the impedance less than or equal to the product of the real part data of the impedance and the tangent of the line impedance angle; determining a first product of a remainder value of the line impedance angle and a reactance setting value; determining a first difference of the real data and the first product; determining a second product of the tangent value of the additional impedance angle and the first difference value; determining a first sum of the second product and the reactance setting value; the imaginary data is less than or equal to the first sum value; the imaginary data is greater than or equal to the product of the real data and the tangent of the additional impedance angle; determining a third product of the cosine value of the additional impedance angle and the resistance setting value; determining a second difference of the real data and the third product; determining a fourth product of the tangent value of the line impedance angle and the second difference value; determining a fifth product of the resistance setting value and the sine value of the additional impedance angle; determining a second sum of the fourth product and the fifth product; the imaginary data is greater than or equal to the second sum value.
As shown in fig. 7, line impedance angleThe included angle between the line segment OA formed by connecting the first vertex O and the second vertex A and the positive half axis OR of the transverse axis; the reactance setting value X set is an ordinate value of the second vertex a, and the reactance setting value can be set according to the line parameter and the protection range, so that the application is not limited; the resistance setting value R set is the length of a line segment OC2 formed by connecting the first vertex O and the fourth vertex C2, and the larger the resistance setting value is, the stronger the transition resistance protection capability is.
In this embodiment, if the measured impedance meets the first criterion, a protection action command is generated and a trip signal is sent. Wherein the first criterion comprises the following 4 inequality constraints: (1) Measuring the product of the real part data of the impedance and the tangent value of the line impedance angle; (2) The imaginary part data is smaller than or equal to a first sum value, wherein the residual value of the line impedance angle can be multiplied by the reactance setting value to obtain a first product; subtracting the real part data from the first product to obtain a first difference value; multiplying the tangent value of the additional impedance angle by the first difference value to obtain a second product; adding the second product and the reactance setting value to obtain a first sum value; (3) The imaginary data is greater than or equal to the product of the real data and the tangent of the additional impedance angle; (4) The imaginary part data is larger than or equal to the second sum value, wherein the cosine value of the additional impedance angle and the resistance setting value can be multiplied to obtain a third multiplication product; subtracting the third product from the real part data to obtain a second difference; multiplying the tangent value of the line impedance angle by the second difference value to obtain a fourth product; multiplying the resistance setting value by the sine value of the additional impedance angle to obtain a fifth product; and adding the fourth product and the fifth product to obtain the second sum. When the measured impedance simultaneously meets the 4 inequality constraints, the measured impedance enters the regulated action area, and the circuit has a two-phase short circuit fault.
Specifically, the first criterion may be determined according to the following set of inequalities (1):
Where X m is the imaginary data of the measured impedance and R m is the real data of the measured impedance.
Illustratively, a device is provided60 °,/>Is-60 DEG, X set is/>R set is 2,/>1.73,/>Is-1.73,/>Is 0.58/>Is 0.5,/>At-0.87, if the imaginary data X m of the measured impedance is 1 and the real data R m of the measured impedance is 1, then/>1.73,1.73 Is greater than X m; 1.74,1.74 is greater than X m; /(I) -1.73, -1.73 Being less than X m; The measured impedance of-1.74 and-1.74 is smaller than X m, so that the imaginary data is 1, and the real data is 1, and meanwhile, the 4 inequality constraints are met, which indicates that the measured impedance enters the regulated action area, and the circuit has a two-phase short circuit fault.
As can be seen from the method shown in fig. 4, the distance protection method for the line provided by the embodiment of the application obtains the voltage data and the current data of the installation protection place of the point of connection; judging the circuit fault type as a two-phase short circuit fault, if yes, adjusting the negative sequence component of the current data based on the voltage data, the current data, the inverter current data of the circuit and the opposite system impedance angle, so that the difference between the inverter negative sequence impedance angle and the opposite system impedance angle is smaller than or equal to a preset threshold value; determining an additional impedance angle of the measured impedance of the grid-connected point installation protection position according to the inversion power supply current data and the fault point non-fault phase negative sequence current data of the line; according to the additional impedance angle, the action area of the circuit is adjusted to obtain an adjusted action area; and finally, generating a protection action instruction according to the measured impedance and the adjusted action area.
It can be seen that the application adjusts the detected negative sequence component of the current data, so that the negative sequence impedance angle of the inverter power supply can be kept constant without being influenced by the fault position and the transition resistance during the two-phase short-circuit fault of the circuit, and is approximately equal to the impedance angle of the opposite system, and because the impedance angles at two sides of the fault point are approximately equal, the additional impedance angle can be accurately calculated only by using the local quantity, and the action area of the circuit is adaptively adjusted by using the additional impedance angle, thereby solving the problems of the protection rejection of the distance between the inversion side when the IIRPP outgoing circuit generates the nonmetallic two-phase short-circuit fault and the protection misoperation of the distance between the inversion side when the lower circuit of the outgoing circuit generates the nonmetallic two-phase short-circuit fault in the related technology, and the internal and external two-phase short-circuit faults in the correct reaction area can be accurately set; meanwhile, the protection scheme provided by the embodiment of the application only utilizes local measurement quantity, does not depend on communication, and improves the reaction speed and efficiency of distance protection; in addition, the protection scheme provided by the embodiment of the application only needs to adjust the negative sequence current and does not influence the positive sequence current to carry out reactive power support, so that the protection scheme can adapt to different IIRPP reactive power support strategies, accords with the grid-connected technical specification of a new energy station, and promotes the high-quality absorption of the new energy.
In a practical scenario, when a fault occurs at the protection exit or the transition resistance is small, the measured impedance may fall near the boundary of the adjusted action area, and therefore, the adjusted action area cannot cover all measured impedances, in order to solve the above problem, in some embodiments of the present application, the method further includes: taking the first vertex as a vertex, taking a first dead zone included angle which is multiple of a preset value as a vertex angle, and taking line segments of the first vertex and the second vertex as a high triangle area as a first dead zone action area; taking the first vertex as a vertex, taking a second dead zone included angle which is multiple of a preset value as a vertex angle, and taking line segments of the first vertex and the fourth vertex as a high triangle area as a second dead zone action area; taking the region formed by the first dead zone operation region and/or the second dead zone operation region and the adjusted operation region as a final operation region; and if the measured impedance meets at least one of the second criterion corresponding to the first dead zone action region and/or the third criterion corresponding to the second dead zone action region and the first criterion, generating a protection action instruction.
FIG. 8 illustrates a schematic diagram of constructing a final action region provided by an embodiment of the present application. The present embodiment is exemplarily described below with reference to fig. 8.
As can be seen from fig. 8, an isosceles triangle region with O as the vertex, a first dead zone angle β Y of 2 times as the vertex angle, and a line OA as the high value can be used as the first dead zone operation region; an isosceles triangle region with O as the vertex, a second dead zone included angle beta Z which is 2 times as the vertex angle, and a line segment of OC1 as the height is taken as a second dead zone operation region. Wherein, beta Y and beta Z are both larger than 0 degrees, and can be adjusted according to actual running conditions, and the application is not limited to this.
The first dead zone operation region and/or the second dead zone operation region, and the region constituted by the adjusted operation region may be used as the final operation region. For example, in some embodiments, the region formed by the first dead zone operation region and the adjusted operation region may be used as the final operation region. In other embodiments, the region formed by the second dead zone operation region and the post-adjustment operation region may be used as the final operation region. In still other embodiments, the region formed by the first dead zone operation region and the second dead zone operation region, and the post-adjustment operation region may be used as the final operation region.
And if the measured impedance meets at least one of the second criterion corresponding to the first dead zone action region and/or the third criterion corresponding to the second dead zone action region and the first criterion, generating a protection action instruction. In some embodiments, the final action region is configured to include a first dead zone action region, a second dead zone action region, and an adjusted action region, e.g., if the measured impedance meets a second criterion, i.e., the measured impedance enters the first dead zone action region, a guard action command may be generated. For another example, if the measured impedance meets a third criterion, i.e., the measured impedance enters the second deadband action region, a protection action command may be generated. For another example, if the measured impedance meets a first criterion, i.e., the measured impedance enters the post-adjustment action zone, a protection action command may be generated. For another example, if the measured impedance meets the first criterion and the second criterion, that is, the measured impedance enters an intersection region of the first dead zone action region and the adjusted action region, a protection action command may be generated. For another example, if the measured impedance satisfies the first criterion and the third criterion, that is, the measured impedance enters an intersection region of the second dead zone action region and the adjusted action region, a protection action command may be generated.
In some embodiments of the present application, in the above method, the second criterion may be determined according to the following method: determining a first tangent value of the sum of the line impedance angle and the first dead zone angle; determining a first ratio of the imaginary data to the first tangent value; the real part data is greater than or equal to the first ratio; determining a second tangent value of the difference between the line impedance angle and the first dead zone angle; determining a second ratio of the imaginary data to a second tangent value; the real part data is less than or equal to the second ratio; determining a sixth product of the reactance setting value and a remainder value of the line impedance angle; determining a third difference of the real data and the sixth product; determining a seventh product of the remainder of the line impedance angle and the third difference; determining a fourth difference value of the reactance setting value and the seventh product; the imaginary data is less than or equal to the fourth difference value;
In this embodiment, the second criterion includes the following 3 inequality constraints: (1) The real part data is larger than or equal to a first ratio, wherein the line impedance angle and the first dead zone included angle can be added, and the tangent value of the obtained sum is obtained to obtain a first tangent value; then, the ratio of the imaginary part data to the first tangent value is used as the first ratio; (2) The real part data is smaller than or equal to a second ratio, wherein the line impedance angle and the first dead zone included angle can be subtracted, and the tangent value of the obtained difference value is obtained to obtain a second tangent value; then, the ratio of the imaginary part data to the second tangent value is used as the second ratio; (3) The imaginary part data is smaller than or equal to the fourth difference value, wherein the reactance setting value and the residual value of the line impedance angle can be multiplied to obtain a sixth product; subtracting the real part data from the sixth product to obtain a third difference value; multiplying the remainder of the line impedance angle with the third difference value to obtain a seventh product; and subtracting the reactance setting value from the seventh product to obtain the fourth difference. When the measured impedance simultaneously meets the 3 inequality constraints, the measured impedance enters a first dead zone action area, and a two-phase short circuit fault exists in the line.
Specifically, the second criterion may be determined according to the following set of inequalities (2):
illustratively, a device is provided 60℃And beta Y ℃of 15℃and X set of/>Is 3.73,/>Is 1,/>0.58, If the imaginary data X m of the measured impedance is 1.5 and the real data R m of the measured impedance is 1, then0.40,0.40 Is less than R m; /(I)1.5,1.5 Is greater than R m; 1.73,1.73 is greater than X m, so that the measured impedance with the imaginary part data being 1.5 and the real part data being 1 simultaneously meets the 3 inequality constraints, which indicates that the measured impedance enters the first dead zone action area and the line has a two-phase short circuit fault.
The third criterion may be determined according to the following method: determining a third tangent value of the difference between the additional impedance angle and the second dead zone angle; determining an eighth product of the imaginary data and the third tangent value; the imaginary data is greater than or equal to the eighth product; determining a fourth tangent value of the sum of the additional impedance angle and the second dead zone angle; determining a ninth product of the imaginary data and the fourth tangent value; the imaginary data is less than or equal to the ninth product; determining a third ratio of the sine value to the cotangent value of the additional impedance angle; determining a third sum of the cosine value of the additional impedance angle and a third ratio; determining a fifth difference between the product of the resistance setting value and the third sum value and the imaginary data; the real data is less than or equal to the fifth difference.
In this embodiment, the third criterion includes the following 3 inequality constraints: (1) The imaginary part data is larger than or equal to the eighth product, wherein the additional impedance angle and the second dead zone included angle can be subtracted first, and the tangent value of the obtained difference value is obtained to obtain a third tangent value; multiplying the imaginary data by a third tangent value to obtain the eighth product; (2) The imaginary part data is smaller than or equal to the ninth product, wherein the additional impedance angle and the second dead zone included angle can be added first, and the tangent value of the obtained sum is obtained to obtain a fourth tangent value; multiplying the imaginary data with a fourth tangent value to obtain a ninth product; (3) The real part data is smaller than or equal to the fifth difference value, wherein the sine value of the additional impedance angle can be divided by the residual value of the additional impedance angle to obtain a third ratio; adding the cosine value of the additional impedance angle and the third ratio to obtain a third sum value; and multiplying the resistance setting value by the third sum value, and subtracting the obtained product from the imaginary data to obtain the fifth difference value. When the measured impedance simultaneously satisfies the 3 inequality constraints, it is indicated that the measured impedance enters the second dead zone action region, i.e. the line has a two-phase short circuit fault.
Specifically, the third criterion may be determined according to the following set of inequalities (3):
by way of example only, and in an illustrative, -45 °, Β Z ° 15 °, R set/>Is-1.73,/>Is-0.58,/>Is 0.71,/>Is-0.71,/>For-1, if the imaginary data X m of the measured impedance is-0.5 and the real data R m of the measured impedance is 0.5, then/>-0.87, -0.87 Less than X m; /(I)-0.29, -0.29 Being greater than X m; /(I)2.51,2.51 Is greater than R m. Therefore, the imaginary part data is-0.5, and the measured impedance of the real part data is 0.5 simultaneously meets the 3 inequality constraints, which indicates that the measured impedance enters the second dead zone action area, namely the line has a two-phase short circuit fault.
As can be seen from the above embodiments, by adding the first dead zone action region and the second dead zone action region on the basis of the post-adjustment action region, when a fault occurs at the protection exit or the transition resistance is small, the measured impedance can also fall within the action region, so that the distance protection scheme can operate normally.
In an actual application scenario, the line may cause two lines of wires to be lapped together due to some factors, such as strong wind, so that the target line shows an instantaneous fault, and the line is provided with reclosing for the instantaneous fault, and can be recovered by itself after the fault trips. Therefore, in order to ensure that the protection action occurs only when the permanent fault occurs at the fault point, in some embodiments of the present application, the protection installation point may be continuously sampled to obtain multiple sets of voltage data and current data, and according to the method in the steps S401 to S405, the measured impedances of the continuous multiple sampling points, for example, whether the measured impedances of the continuous 5 sampling points all meet at least one of the first criterion, the second criterion and the third criterion, and if yes, the fault point may be determined to be the permanent fault point, an action protection instruction may be generated, and a trip signal may be sent out.
Fig. 9 is a schematic flow chart of a distance protection method for a circuit according to another embodiment of the present application, and as can be seen from fig. 9, the distance protection method for a circuit according to the present embodiment includes the following steps S901 to S926:
Step S901: and acquiring voltage data and current data of the grid-connected point installation protection place.
Step S902: and judging whether the circuit fault type is a two-phase short circuit fault, if so, turning to step S903.
Step S903: and determining the absolute value of the phase difference between the target phase positive sequence current and the negative sequence current to obtain phase difference data. The target phase is the phase with the smallest phase difference between the positive sequence current and the negative sequence current in the current data.
Step S904: and multiplying the positive sequence component of the inversion power supply current data and the sine value of the phase difference data to obtain first intermediate data.
Step S905: and adding the square of the first intermediate data and the square of the maximum phase current data of the inversion power supply current data to obtain second intermediate data.
Step S906: and multiplying the positive sequence component of the inversion power supply current data and the cosine value of the phase difference data to obtain third intermediate data.
Step S907: and determining the square root of the second intermediate data and the difference between the second intermediate data and the third intermediate data to obtain negative sequence current data of the inverter.
Step S908: and respectively carrying out coordinate transformation on the negative sequence component of the voltage data and the negative sequence component of the current data to obtain a first voltage component and a second voltage component, and a first current component and a second current component.
Step S909: and determining the ratio of the second voltage component to the first voltage component to obtain fourth intermediate data.
Step S910: and determining the difference between the arctangent value of the fourth intermediate data and the impedance angle of the opposite system to obtain fifth intermediate data.
Step S911: and determining the product of the negative sequence current data of the inverter and the cosine value of the fifth intermediate data to obtain a first current component preset value.
Step S912: and determining the product of the negative sequence current data of the inverter and the sine value of the fifth intermediate data to obtain a second current component preset value.
Step S913: and adjusting the first current component by using a first current component preset value, and adjusting the second current component by using the first current component preset value so that the difference between the negative sequence impedance angle of the inverter power supply and the opposite system impedance angle is smaller than or equal to a preset threshold value.
Step S914: a current difference between two failed phases in the inverter current data is determined.
Step S915: and determining the ratio of the non-fault phase negative sequence current to the current difference in the inverter power supply current data.
Step S916: and determining the sum of the phase angle of the ratio and a preset angle to obtain an additional impedance angle.
Step S917: taking the intersection point of the first impedance relay direction line and the second impedance relay direction line as a first vertex; taking the intersection point of the first impedance relay direction line and the reactance line as a second vertex; taking the intersection point of the reactance line and the resistance line as an initial third vertex; and taking the intersection point of the resistance wire and the direction wire of the second impedance relay as an initial fourth vertex. The quadrilateral area formed by the first vertex, the second vertex, the initial third vertex and the initial fourth vertex is an action area of the circuit.
Step S918: a line segment formed by connecting the second vertex and the initial third vertex rotates around the second vertex by an angle of an additional impedance angle to obtain a line segment formed by connecting the second vertex and the third vertex; and rotating the line segment formed by connecting the first vertex and the initial fourth vertex by an angle of an additional impedance angle around the first vertex to obtain the line segment formed by connecting the first vertex and the fourth vertex.
Step S919: and taking a quadrilateral area formed by the first vertex, the second vertex, the third vertex and the fourth vertex as an adjusted action area.
Step S920: and taking the first vertex as a vertex, taking a first dead zone included angle which is multiple of a preset value as a vertex angle, and taking line segments of the first vertex and the second vertex as a triangular area with high value as a first dead zone action area.
Step S921: and taking the first vertex as a vertex, taking a second dead zone included angle which is multiple of a preset value as a vertex angle, and taking line segments of the first vertex and the fourth vertex as a high triangle area as a second dead zone action area.
Step S922: the region formed by the first dead zone operation region, the second dead zone operation region, and the adjusted operation region is used as a final operation region.
Step S923: judging whether the measured impedance meets a first criterion, if so, turning to step S926; if not, the process goes to step S924. The impedance angle of the line is a line segment formed by connecting the first vertex and the second vertex, the included angle between the impedance angle and the positive semi-axis of the horizontal axis is the ordinate data of the second vertex, and the impedance setting value is the length of the line segment formed by connecting the first vertex and the fourth vertex. The first criterion is determined according to the following method: measuring the imaginary part data of the impedance less than or equal to the product of the real part data of the impedance and the tangent of the line impedance angle; determining a first product of a remainder value of the line impedance angle and a reactance setting value; determining a first difference of the real data and the first product; determining a second product of the tangent value of the additional impedance angle and the first difference value; determining a first sum of a second product and the reactance setting value; the imaginary data is less than or equal to the first sum value; the imaginary data is greater than or equal to the product of the real data and the tangent of the additional impedance angle; determining a third product of the cosine value of the additional impedance angle and the resistance setting value; determining a second difference of the real data and the third product; determining a fourth product of the tangent value of the line impedance angle and the second difference value; determining a fifth product of the resistance setting value and the sine value of the additional impedance angle; determining a second sum of the fourth product and the fifth product; the imaginary data is greater than or equal to the second sum value.
Step S924: judging whether the measured impedance meets a second criterion, if so, turning to step S926; if not, the process goes to step S925. Wherein the second criterion may be determined according to the following method: determining a first tangent value of the sum of the line impedance angle and the first dead zone angle; determining a first ratio of the imaginary data to the first tangent value; the real part data is greater than or equal to the first ratio; determining a second tangent value of the difference between the line impedance angle and the first dead zone angle; determining a second ratio of the imaginary data to a second tangent value; the real part data is less than or equal to the second ratio; determining a sixth product of the reactance setting value and a remainder value of the line impedance angle; determining a third difference of the real data and the sixth product; determining a seventh product of the remainder of the line impedance angle and the third difference; determining a fourth difference value of the reactance setting value and the seventh product; the imaginary data is less than or equal to the fourth difference value.
Step S925: whether the measured impedance satisfies the third criterion is determined, and if so, the process goes to step S926. Wherein the third criterion may be determined according to the following method: determining a third tangent value of the difference between the additional impedance angle and the second dead zone angle; determining an eighth product of the imaginary data and the third tangent value; the imaginary data is greater than or equal to the eighth product; determining a fourth tangent value of the sum of the additional impedance angle and the second dead zone angle; determining a ninth product of the imaginary data and the fourth tangent value; the imaginary data is less than or equal to the ninth product; determining a third ratio of the sine value to the cotangent value of the additional impedance angle; determining a third sum of the cosine value of the additional impedance angle and a third ratio; determining a fifth difference between the product of the resistance setting value and the third sum value and the imaginary data; the real data is less than or equal to the fifth difference.
Step S926: generating a protection action instruction.
Fig. 10 shows a schematic structural diagram of a distance protection device for a line according to an embodiment of the present application, where the device 1000 includes:
The acquiring module 1001 is configured to acquire voltage data and current data at a grid-connected point installation protection place.
And a negative sequence impedance stabilizing module 1002, configured to adjust a negative sequence component of the current data based on the voltage data, the current data, the inverter current data of the line, and the opposite side system impedance angle if the circuit fault type is a two-phase short circuit fault, so that a difference between the inverter negative sequence impedance angle and the opposite side system impedance angle is less than or equal to a preset threshold.
And an additional impedance angle determining module 1003, configured to determine an additional impedance angle of the measured impedance at the grid-connected point installation protection location according to the inverter current data and the fault point non-fault phase negative sequence current data of the line.
And the region adjustment module 1004 is configured to adjust the operation region of the line according to the additional impedance angle, so as to obtain an adjusted operation region.
A protection instruction generating module 1005, configured to generate a protection action instruction according to the measured impedance and the adjusted action area.
In some embodiments of the present application, in the above apparatus, the negative sequence impedance stabilizing module 1002 is configured to determine negative sequence current data of the inverter power source according to the current data and the current data of the inverter power source; respectively carrying out coordinate transformation on the negative sequence component of the voltage data and the negative sequence component of the current data to obtain a first voltage component and a second voltage component, and a first current component and a second current component; performing logic operation on the negative sequence current data of the inverter power supply, the first voltage component, the second voltage component and the opposite side system impedance angle to obtain a first current component preset value and a second current component preset value; and adjusting the first current component by using the first current component preset value, and adjusting the second current component by using the first current component preset value so that the difference between the negative sequence impedance angle of the inverter power supply and the opposite system impedance angle is smaller than or equal to a preset threshold value.
In some embodiments of the present application, in the foregoing apparatus, the negative sequence impedance stabilization module 1002 is configured to determine an absolute value of a phase difference between a positive sequence current and a negative sequence current of a target phase, and obtain phase difference data, where the target phase is a phase in which a phase difference between the positive sequence current and the negative sequence current in the current data is the smallest; multiplying the positive sequence component of the inversion power supply current data and the sine value of the phase difference data to obtain first intermediate data; adding the square of the first intermediate data and the square of the maximum phase current data of the inverter power supply current data to obtain second intermediate data; multiplying the positive sequence component of the inversion power supply current data and the cosine value of the phase difference data to obtain third intermediate data; and determining the square root of the second intermediate data and the difference between the second intermediate data and the third intermediate data to obtain the negative sequence current data of the inverter.
In some embodiments of the present application, in the above apparatus, the negative sequence impedance stabilizing module 1002 is configured to determine a ratio of the second voltage component to the first voltage component, to obtain fourth intermediate data; determining the difference between the arctangent value of the fourth intermediate data and the opposite-side system impedance angle to obtain fifth intermediate data; determining the product of the negative sequence current data of the inverter power supply and the cosine value of the fifth intermediate data to obtain the first current component preset value; and determining the product of the negative sequence current data of the inverter and the sine value of the fifth intermediate data to obtain the second current component preset value.
In some embodiments of the present application, in the above apparatus, the additional impedance angle determining module 1003 is configured to determine a current difference between two fault phases in the inverter power current data; determining the ratio of the non-fault phase negative sequence current in the inverter power supply current data to the current difference; and determining the sum of the phase angle of the ratio and a preset angle to obtain the additional impedance angle.
In some embodiments of the present application, in the foregoing apparatus, the area adjustment module 1004 is configured to take an intersection point of the first impedance relay direction line and the second impedance relay direction line as a first vertex; taking the intersection point of the first impedance relay direction line and the reactance line as a second vertex; taking the intersection point of the reactance line and the resistance line as an initial third vertex; taking an intersection point of the resistance wire and the second impedance relay direction wire as an initial fourth vertex, wherein a quadrilateral area formed by the first vertex, the second vertex, the initial third vertex and the initial fourth vertex is an action area of the circuit; rotating the angle of the additional impedance angle around the second vertex to obtain a line segment formed by connecting the second vertex and the third vertex; rotating the angle of the additional impedance angle around the first vertex to obtain a line segment formed by connecting the first vertex and the fourth vertex; and taking a quadrilateral area formed by the first vertex, the second vertex, the third vertex and the fourth vertex as the adjusted action area.
In some embodiments of the present application, in the above apparatus, the protection instruction generating module 1005 is configured to generate a protection action instruction if the measured impedance meets a first criterion; the impedance angle of the line is a line segment formed by connecting the first vertex and the second vertex, the included angle between the impedance angle and the positive semi-axis of the horizontal axis is an ordinate data of the second vertex, and the impedance setting value is a length of the line segment formed by connecting the first vertex and the fourth vertex; the protection instruction generating module 1005 further includes a first criterion determining unit, configured to determine a first criterion according to the following method: the imaginary data of the measured impedance is less than or equal to the product of the real data of the measured impedance and the tangent of the line impedance angle; determining a first product of a remainder value of the line impedance angle and a reactance setting value; determining a first difference of the real data and the first product; determining a second product of a tangent value of the additional impedance angle and the first difference value; determining a first sum of the second product and the reactance setting value; the imaginary data is less than or equal to the first sum value; the imaginary data is greater than or equal to a product of the real data and a tangent of the additional impedance angle; determining a third product of the cosine value of the additional impedance angle and the resistance setting value; determining a second difference of the real data and the third product; determining a fourth product of the tangent of the line impedance angle and the second difference; determining a fifth product of the resistance setting value and the sine value of the additional impedance angle; determining a second sum of the fourth product and the fifth product; the imaginary data is greater than or equal to the second sum.
In some embodiments of the present application, the apparatus further includes a dead zone protection module, where the dead zone protection module is configured to use the first vertex as a vertex, a first dead zone included angle that is multiple of a preset value as a vertex, and a triangular area with line segments of the first vertex and the second vertex as high as a first dead zone action area; taking the first vertex as a vertex, taking a second dead zone included angle which is multiple of a preset value as a vertex angle, and taking line segments of the first vertex and the fourth vertex as a high triangle area as a second dead zone action area; taking the region formed by the first dead zone action region and/or the second dead zone action region and the adjusted action region as a final action region; and if the measured impedance meets at least one of the second criterion and/or the third criterion and the first criterion, generating a protection action instruction.
In some embodiments of the present application, in the above apparatus, the dead zone protection module further includes a second criterion determining unit and a third criterion determining unit, where the second criterion determining unit is configured to determine the second criterion according to the following method: determining a first tangent value of a sum of the line impedance angle and the first dead zone angle; determining a first ratio of the imaginary data to the first tangent value; the real data is greater than or equal to the first ratio; determining a second tangent value of a difference between the line impedance angle and the first dead zone angle; determining a second ratio of the imaginary data to the second tangent value; the real data is less than or equal to the second ratio; determining a sixth product of the reactance setting value and a remainder value of the line impedance angle; determining a third difference of the real data and the sixth product; determining a seventh product of the remainder value of the line impedance angle and the third difference value; determining a fourth difference value of the reactance setting value and the seventh product; the imaginary data is less than or equal to the fourth difference value; the third criterion determining unit is configured to determine a third criterion according to the following method: determining a third tangent value of a difference between the additional impedance angle and the second dead angle; determining an eighth product of the imaginary data and the third tangent value; the imaginary data is greater than or equal to the eighth product; determining a fourth tangent value of the sum of the additional impedance angle and the second dead zone angle; determining a ninth product of the imaginary data and the fourth tangent value; the imaginary data is less than or equal to the ninth product; determining a third ratio of the sine value to the cotangent value of the additional impedance angle; determining a third sum of the cosine value of the additional impedance angle and the third ratio; determining a fifth difference between the product of the resistance setting value and the third sum value and the imaginary data; the real data is less than or equal to the fifth difference.
It should be noted that the distance protection device of any one of the above-mentioned lines may be in one-to-one correspondence to implement the distance protection method of the above-mentioned line, which is not described herein again.
Fig. 11 shows a schematic structural diagram of an electronic device according to an embodiment of the present application. As shown in fig. 11, at the hardware level, the electronic device comprises a processor, optionally together with an internal bus, a network interface, a memory. The Memory may include a Memory, such as a Random-Access Memory (RAM), and may further include a non-volatile Memory (non-volatile Memory), such as at least 1 disk Memory. Of course, the electronic device may also include hardware required for other services.
The processor, network interface, and memory may be interconnected by an internal bus, which may be an ISA (Industry Standard Architecture ) bus, a PCI (PERIPHERAL COMPONENT INTERCONNECT, peripheral component interconnect standard) bus, or EISA (Extended Industry Standard Architecture ) bus, among others. The buses may be divided into address buses, data buses, control buses, etc. For ease of illustration, only one bi-directional arrow is shown in FIG. 11, but not only one bus or type of bus.
And the memory is used for storing programs. In particular, the program may include program code including computer-operating instructions. The memory may include memory and non-volatile storage and provide instructions and data to the processor.
The processor reads the corresponding computer program from the nonvolatile memory into the memory and then runs, and the distance protection device of the circuit is formed on the logic level. And the processor is used for executing the program stored in the memory and particularly used for executing the method.
The processor may be an integrated circuit chip having signal processing capabilities. In implementation, the steps of the above method may be performed by integrated logic circuits of hardware in a processor or by instructions in the form of software. The processor may be a general-purpose processor, including a central processing unit (Central Processing Unit, CPU), a network processor (Network Processor, NP), etc.; but may also be a digital signal Processor (DIGITAL SIGNAL Processor, DSP), application SPECIFIC INTEGRATED Circuit (ASIC), field-Programmable gate array (Field-Programmable GATE ARRAY, FPGA) or other Programmable logic device, discrete gate or transistor logic device, discrete hardware components. The disclosed methods, steps, and logic blocks in the embodiments of the present application may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in connection with the embodiments of the present application may be embodied directly in the execution of a hardware decoding processor, or in the execution of a combination of hardware and software modules in a decoding processor. The software modules may be located in a random access memory, flash memory, read only memory, programmable read only memory, or electrically erasable programmable memory, registers, etc. as well known in the art. The storage medium is located in a memory, and the processor reads the information in the memory and, in combination with its hardware, performs the steps of the above method.
The electronic device may execute the distance protection method of the line provided by the embodiments of the present application, and implement the function of the distance protection device of the line in the embodiment shown in fig. 10, which is not described herein.
The embodiments of the present application also provide a computer-readable storage medium storing one or more programs, the one or more programs including instructions, which when executed by an electronic device including a plurality of application programs, enable the electronic device to perform the method for protecting a distance of a line provided by the embodiments of the present application.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
In one typical configuration, a computing device includes one or more processors (CPUs), input/output interfaces, network interfaces, and memory.
The memory may include volatile memory in a computer-readable medium, random Access Memory (RAM) and/or nonvolatile memory, such as Read Only Memory (ROM) or flash memory (flash RAM). Memory is an example of computer-readable media.
Computer readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of storage media for a computer include, but are not limited to, phase change memory (PRAM), static Random Access Memory (SRAM), dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), read Only Memory (ROM), electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium, which can be used to store information that can be accessed by a computing device. Computer-readable media, as defined herein, does not include transitory computer-readable media (transmission media), such as modulated data signals and carrier waves.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The foregoing is merely exemplary of the present application and is not intended to limit the present application. Various modifications and variations of the present application will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the application are to be included in the scope of the claims of the present application.

Claims (12)

1. A method for protecting a line from distance, the method comprising:
Acquiring voltage data and current data of a grid-connected point installation protection place;
If the circuit fault type is a two-phase short circuit fault, adjusting a negative sequence component of the current data based on the voltage data, the current data, the inverter current data of the circuit and the opposite-side system impedance angle so that the difference between the inverter negative sequence impedance angle and the opposite-side system impedance angle is smaller than or equal to a preset threshold value;
Determining an additional impedance angle of the measured impedance of the grid-connected point installation protection position according to the inverter power supply current data and the fault point non-fault phase negative sequence current data of the line;
according to the additional impedance angle, an action area of the circuit is adjusted to obtain an adjusted action area;
and generating a protection action instruction according to the measured impedance and the adjusted action area.
2. The method of claim 1, wherein adjusting the negative sequence component of the current data based on the voltage data, the current data, the line inverter current data, and the opposite side system impedance angle such that a difference between the inverter negative sequence impedance angle and the opposite side system impedance angle is less than or equal to a preset threshold comprises:
Determining negative sequence current data of the inverter power supply according to the current data and the current data of the inverter power supply;
Respectively carrying out coordinate transformation on the negative sequence component of the voltage data and the negative sequence component of the current data to obtain a first voltage component and a second voltage component, and a first current component and a second current component;
performing logic operation on the negative sequence current data of the inverter power supply, the first voltage component, the second voltage component and the opposite side system impedance angle to obtain a first current component preset value and a second current component preset value;
And adjusting the first current component by using the first current component preset value, and adjusting the second current component by using the first current component preset value so that the difference between the negative sequence impedance angle of the inverter power supply and the opposite system impedance angle is smaller than or equal to a preset threshold value.
3. The method of claim 2, wherein said determining inverter negative sequence current data from said current data and said inverter current data comprises:
Determining the absolute value of the phase difference between the positive sequence current and the negative sequence current of a target phase to obtain phase difference data, wherein the target phase is the phase with the minimum phase difference between the positive sequence current and the negative sequence current in the current data;
multiplying the positive sequence component of the inverter power supply current data and the sine value of the phase difference data to obtain first intermediate data;
Adding the squares of the first intermediate data and the squares of the maximum phase current data of the inverter power supply current data to obtain second intermediate data;
multiplying the positive sequence component of the inversion power supply current data and the cosine value of the phase difference data to obtain third intermediate data;
and determining the difference between the square root of the second intermediate data and the third intermediate data to obtain the negative sequence current data of the inverter.
4. The method of claim 2, wherein performing a logic operation on the negative sequence current data of the inverter, the first voltage component, the second voltage component, and the opposite side system impedance angle to obtain a first current component preset value and a second current component preset value comprises:
Determining the ratio of the second voltage component to the first voltage component to obtain fourth intermediate data;
determining the difference between the arctangent value of the fourth intermediate data and the opposite system impedance angle to obtain fifth intermediate data;
determining the product of the cosine values of the negative sequence current data and the fifth intermediate data of the inverter power supply to obtain the first current component preset value;
And determining the product of the sine value of the negative sequence current data of the inverter and the fifth intermediate data to obtain the second current component preset value.
5. The method of claim 1, wherein determining an additional impedance angle of the measured impedance at the grid-tie point installation protection from the inverter supply current data and the fault point non-fault phase negative sequence current data of the line comprises:
Determining a current difference between two fault phases in the inverter current data;
Determining the ratio of the non-fault phase negative sequence current in the inverter power supply current data to the current difference;
and determining the sum of the phase angle of the ratio and a preset angle to obtain the additional impedance angle.
6. The method of claim 1, wherein adjusting the action area of the line according to the additional impedance angle to obtain an adjusted action area comprises:
Taking the intersection point of the first impedance relay direction line and the second impedance relay direction line as a first vertex; taking the intersection point of the first impedance relay direction line and the reactance line as a second vertex; taking the intersection point of the reactance line and the resistance line as an initial third vertex; taking an intersection point of the resistance wire and the second impedance relay direction wire as an initial fourth vertex, wherein a quadrilateral area formed by the first vertex, the second vertex, the initial third vertex and the initial fourth vertex is an action area of the circuit;
Rotating the angle of the additional impedance angle around the second vertex to obtain a line segment formed by connecting the second vertex and the third vertex; rotating the angle of the additional impedance angle around the first vertex to obtain a line segment formed by connecting the first vertex and the fourth vertex;
And taking a quadrilateral area formed by the first vertex, the second vertex, the third vertex and the fourth vertex as the adjusted action area.
7. The method of claim 6, wherein generating a protection action command based on the measured impedance and the adjusted action region comprises:
If the measured impedance meets a first criterion, generating a protection action instruction;
The impedance angle of the line is a line segment formed by connecting the first vertex and the second vertex, the included angle between the impedance angle and the positive semi-axis of the horizontal axis is an ordinate data of the second vertex, and the impedance setting value is a length of the line segment formed by connecting the first vertex and the fourth vertex;
The first criterion is determined according to the following method:
The imaginary data of the measured impedance is less than or equal to the product of the real data of the measured impedance and the tangent of the line impedance angle;
Determining a first product of a remainder value of the line impedance angle and a reactance setting value; determining a first difference of the real data and the first product; determining a second product of a tangent value of the additional impedance angle and the first difference value; determining a first sum of the second product and the reactance setting value; the imaginary data is less than or equal to the first sum value;
The imaginary data is greater than or equal to a product of the real data and a tangent of the additional impedance angle;
Determining a third product of the cosine value of the additional impedance angle and the resistance setting value; determining a second difference of the real data and the third product; determining a fourth product of the tangent of the line impedance angle and the second difference; determining a fifth product of the resistance setting value and the sine value of the additional impedance angle; determining a second sum of the fourth product and the fifth product; the imaginary data is greater than or equal to the second sum.
8. The method of claim 7, wherein the method further comprises:
taking the first vertex as a vertex, taking a first dead zone included angle which is multiple of a preset value as a vertex angle, and taking line segments of the first vertex and the second vertex as a high triangle area as a first dead zone action area;
Taking the first vertex as a vertex, taking a second dead zone included angle which is multiple of a preset value as a vertex angle, and taking line segments of the first vertex and the fourth vertex as a high triangle area as a second dead zone action area;
Taking the region formed by the first dead zone action region and/or the second dead zone action region and the adjusted action region as a final action region;
And if the measured impedance meets at least one of a second criterion corresponding to the first dead zone action region and/or a third criterion corresponding to the second dead zone action region and the first criterion, generating a protection action instruction.
9. The method of claim 8, wherein the second criterion is determined according to the following method:
determining a first tangent value of a sum of the line impedance angle and the first dead zone angle; determining a first ratio of the imaginary data to the first tangent value; the real data is greater than or equal to the first ratio;
Determining a second tangent value of a difference between the line impedance angle and the first dead zone angle; determining a second ratio of the imaginary data to the second tangent value; the real data is less than or equal to the second ratio;
Determining a sixth product of the reactance setting value and a remainder value of the line impedance angle; determining a third difference of the real data and the sixth product; determining a seventh product of the remainder value of the line impedance angle and the third difference value; determining a fourth difference value of the reactance setting value and the seventh product; the imaginary data is less than or equal to the fourth difference value;
determining the third criterion according to the following method:
Determining a third tangent value of a difference between the additional impedance angle and the second dead angle; determining an eighth product of the real data and the third tangent value; the imaginary data is greater than or equal to the eighth product;
determining a fourth tangent value of the sum of the additional impedance angle and the second dead zone angle; determining a ninth product of the real data and the fourth tangent value; the imaginary data is less than or equal to the ninth product;
Determining a third ratio of the sine value to the cotangent value of the additional impedance angle; determining a third sum of the cosine value of the additional impedance angle and the third ratio; determining a fifth difference between the product of the resistance setting value and the third sum value and the imaginary data; the real data is less than or equal to the fifth difference.
10. A distance protection device for a line, the device comprising:
the acquisition module is used for acquiring voltage data and current data of the grid-connected point installation protection place;
The negative sequence impedance stabilizing module is used for adjusting the negative sequence component of the current data based on the voltage data, the current data, the inverter current data of the circuit and the opposite side system impedance angle if the circuit fault type is a two-phase short circuit fault, so that the difference between the inverter negative sequence impedance angle and the opposite side system impedance angle is smaller than or equal to a preset threshold value;
The additional impedance angle determining module is used for determining an additional impedance angle of the measured impedance of the grid-connected point installation protection position according to the inverter power supply current data and the fault point non-fault phase negative sequence current data of the line;
The region adjustment module is used for adjusting the action region of the circuit according to the additional impedance angle to obtain an adjusted action region;
and the protection instruction generation module is used for generating a protection action instruction according to the measured impedance and the adjusted action area.
11. An electronic device, comprising:
A processor; and
A memory arranged to store computer executable instructions which when executed cause the processor to perform the steps of the distance protection method of a line as claimed in any one of claims 1 to 9.
12. A computer readable storage medium storing one or more programs, which when executed by an electronic device comprising a plurality of application programs, cause the electronic device to perform the steps of the distance protection method of a line according to any one of claims 1-9.
CN202311048520.5A 2023-08-18 2023-08-18 Circuit distance protection method and device, electronic equipment and readable storage medium Active CN117277232B (en)

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