CN117277230A - Single-phase grounding distance protection method and device, storage medium and computer equipment - Google Patents
Single-phase grounding distance protection method and device, storage medium and computer equipment Download PDFInfo
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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
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- 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
- H02H3/02—Details
- H02H3/021—Details concerning the disconnection itself, e.g. at a particular instant, particularly at zero value of current, disconnection in a predetermined order
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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
- H02H7/261—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 involving signal transmission between at least two stations
- H02H7/263—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 involving signal transmission between at least two stations involving transmissions of measured values
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Abstract
The application discloses a single-phase grounding distance protection method and device, a storage medium and computer equipment, wherein the method comprises the following steps: when the alternating current sending-out line of the soft direct current converter station is judged to be in single-phase grounding fault, a first measuring current corresponding to a preset protection device is obtained, a negative sequence current component and a zero sequence current component are extracted from the first measuring current, and the preset protection device is arranged on one side of an alternating current system; determining a current component ratio based on the negative sequence current component and the zero sequence current component; judging a fault section of the single-phase earth fault according to the current component ratio, wherein the fault section is one of an intra-zone fault, a forward extra-zone fault and a reverse extra-zone fault; and when the fault section is an intra-zone fault and a preset action condition is met, controlling the corresponding preset protection device to act. The method and the device can greatly improve the accuracy of the fault judgment result in the single-phase earth fault time zone and ensure the correct action of distance protection.
Description
Technical Field
The application relates to the technical field of power grid control protection, in particular to a single-phase grounding distance protection method and device, a storage medium and computer equipment.
Background
The alternating current outgoing line of the soft direct current converter station is a typical scene of a power electronic power supply at one end and a synchronous machine power supply at the other end, the fault characteristic on the line is affected by the soft direct current converter the most, and the adaptability of the traditional protection device is affected the most seriously. After the alternating current outgoing line of the soft direct current converter station fails, if the protection device cannot timely and correctly cut off the failure, the failure range is expanded, the power of the soft direct current transmission line is blocked, the soft direct current converter is possibly blocked when serious, and then the soft direct current transmission end and the power grid at the receiving end are impacted.
Single-phase earth faults are the most common fault types in transmission line operation, accounting for more than 90% of the total amount of all types of faults, and are usually accompanied by transition resistances. Distance protection is commonly used in the prior art to identify single phase earth faults in ac transmission lines.
However, when a single-phase ground fault occurs in the ac outgoing line of the soft direct current converter station, an error occurs in the measured impedance of the distance protection due to the existence of the transition resistor, and the measured impedance at this time cannot correctly reflect the fault position, so that the conventional distance protection cannot operate correctly.
Disclosure of Invention
In view of this, the present application provides a single-phase grounding distance protection method and apparatus, a storage medium, and a computer device, where when judging whether a fault section of a flexible direct current converter station ac outgoing line is an intra-area fault, no transition resistor is involved, and the influence of the size and the nature of the transition resistor on the judgment result is eliminated in principle, so that the accuracy of the intra-area fault judgment result in the single-phase grounding fault time zone can be greatly improved, and the correct action of distance protection is ensured.
According to one aspect of the present application, there is provided a single-phase grounding distance protection method applied to a soft direct current converter station ac outgoing line, including:
when the alternating current sending-out line of the soft direct current converter station is judged to be in single-phase grounding fault, a first measuring current corresponding to a preset protection device is obtained, a negative sequence current component and a zero sequence current component are extracted from the first measuring current, and the preset protection device is arranged on one side of an alternating current system;
determining a current component ratio based on the negative sequence current component and the zero sequence current component;
judging a fault section of the single-phase earth fault according to the current component ratio, wherein the fault section is one of an intra-zone fault, a forward extra-zone fault and a reverse extra-zone fault;
and when the fault section is an intra-zone fault and a preset action condition is met, controlling the corresponding preset protection device to act.
According to another aspect of the present application, there is provided a single-phase grounding distance protection device applied to a soft direct current converter station ac outgoing line, including:
the current component extraction module is used for obtaining a first measuring current corresponding to a preset protection device when the alternating current outgoing line of the flexible direct current converter station is judged to be in single-phase earth fault, and extracting a negative sequence current component and a zero sequence current component from the first measuring current, wherein the preset protection device is arranged at one side of an alternating current system;
the ratio determining module is used for determining a current component ratio based on the negative sequence current component and the zero sequence current component;
the fault section judging module is used for judging a fault section of the single-phase earth fault according to the current component ratio, wherein the fault section is one of an intra-zone fault, a forward extra-zone fault and a reverse extra-zone fault;
and the control module is used for controlling the corresponding preset protection device to act when the fault section is an intra-area fault and the preset action condition is met.
According to yet another aspect of the present application, there is provided a storage medium having stored thereon a computer program which when executed by a processor implements the above-described single-phase grounding distance protection method.
According to still another aspect of the present application, there is provided a computer device including a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor, the processor implementing the above-mentioned single-phase grounding distance protection method when executing the program.
By means of the technical scheme, the single-phase grounding distance protection method, the single-phase grounding distance protection device, the storage medium and the computer equipment can obtain the first measuring current of the preset protection device on the alternating-current sending-out line of the soft direct current converter station when judging that the alternating-current sending-out line of the soft direct current converter station has single-phase grounding faults, and further can extract the negative sequence current component and the zero sequence current component from the first measuring current. The current component ratio can then be calculated from the negative sequence current component and the zero sequence current component. Then, based on the ratio of the current components, it can be determined which fault section of the single-phase earth fault of the ac outgoing line of the soft direct current converter station specifically belongs, wherein the fault section can include an intra-zone fault, a forward-zone fault, a reverse-zone fault, and the like. If the fault section is judged to be the fault in the zone and the preset action condition is met, the action of the preset protection device can be controlled. According to the embodiment of the application, when judging whether the fault section of the alternating current outgoing line of the soft direct current converter station is an intra-area fault or not, the transition resistor is not involved, and the influence of the size and the property of the transition resistor on a judgment result is eliminated in principle, so that the accuracy of the intra-area fault judgment result in the single-phase grounding fault time zone can be greatly improved, and the correct action of distance protection is ensured.
The foregoing description is only an overview of the technical solutions of the present application, and may be implemented according to the content of the specification in order to make the technical means of the present application more clearly understood, and in order to make the above-mentioned and other objects, features and advantages of the present application more clearly understood, the following detailed description of the present application will be given.
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 application, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute an undue limitation to the application. In the drawings:
fig. 1 shows a schematic flow chart of a single-phase grounding distance protection method according to an embodiment of the present application;
fig. 2 is a schematic structural diagram of a flexible direct current converter station ac output line according to an embodiment of the present application;
FIG. 3 is a schematic flow chart of another single-phase grounding distance protection method according to an embodiment of the present application;
fig. 4 shows a schematic structural diagram of a single-phase grounding distance protection device according to an embodiment of the present application.
Detailed Description
The present application will be described in detail hereinafter with reference to the accompanying drawings in conjunction with embodiments. It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other.
In this embodiment, a single-phase grounding distance protection method is provided, which is applied to a soft direct current converter station ac output line, as shown in fig. 1, and the method includes:
step 101, when it is determined that an alternating current outgoing line of a soft direct current converter station is in a single-phase earth fault, obtaining a first measuring current corresponding to a preset protection device, and extracting a negative sequence current component and a zero sequence current component from the first measuring current, wherein the preset protection device is arranged at one side of an alternating current system;
the single-phase grounding distance protection method provided by the embodiment of the application can be applied to an alternating current transmission line of a soft direct current converter station, and particularly can be applied to the alternating current transmission line of the soft direct current converter station with single-phase grounding faults. Fig. 2 is a schematic structural diagram of a ac output line of a soft dc converter station, wherein the soft dc converter station is connected with an ac system through the ac output line of the soft dc converter station (soft dc output line in the figure), the ac output line of the soft dc converter station includes a preset protection device (R in the figure), and a measured current at a mounting position of the preset protection device is I gs The fault current of the soft direct current converter station side is I mmc The transition resistance is R g . The traditional distance protection scheme calculates the measured impedance reflecting the fault position through the measured current and the voltage at the installation position of the preset protection device, judges the fault occurrence area through the comparison of the measured impedance and the setting impedance, and performs time matching according to the protection range. The principle of a ground impedance relay for single-phase faults can be expressed asWherein U is gs For presetting the measured voltage at the installation site of the protection device, I gs For presetting the measured current at the installation of the protection device, Z gs And (3) for presetting the measured impedance of the protection device, comparing the measured impedance with the set action area to judge the position of the fault.
If the AC outgoing line has metallic single-phase earth fault, the fault point of the line is grounded, and the voltage of the fault point is zero, namely U f =0, the measured current at the installation place of the preset protection device is I gs The measurement voltage is U gs ＝αZ L ·I gs +U f ＝αZL·I gs Alpha is the distance between the fault point in the AC transmission line and the AC system side, at which time the impedance is measuredThe preset protection device can act correctly.
The traditional distance protection is reliable in principle when a metallic fault occurs, but the performance is obviously influenced by the transition resistance, and the transition resistance is mostly accompanied in the actual fault, and the measured impedance of the traditional distance protection and the actual fault impedance have larger errors in addition to the phase control characteristic of the fault current of the alternating current outgoing line of the flexible direct current converter station, so that the traditional distance protection performance is greatly influenced.
If the alternating current transmission line of the soft direct current converter station generates a transition resistance R g In which the line fault point voltage is not zero, i.e. U, due to the presence of transition resistance f ＝I f ·R g ＝(I mmc +I gs )·R g The measured current at the installation position of the preset protection device is I gs The fault current of the soft direct current converter station side is I mmc The measurement voltage is U gs ＝αZ L ·I gs +U f ＝αZ L ·I gs +(I mmc +I gs )·R g Measuring impedance at this timeExcept for the line impedance αz from the fault point to the installation of the predetermined protection device L In addition, the additional impedance caused by the transition resistance is also included>Under the influence of the phase-controlled characteristic of the output current of the soft direct current converter, the property of the additional impedance is more difficult to predict, the measured impedance at the moment cannot correctly reflect the fault position, and the traditional distance protection cannot correctly act.
Therefore, when the single-phase earth fault occurs to the alternating current sending-out line of the soft direct current converter station, the first measuring current of the preset protection device on the alternating current sending-out line of the soft direct current converter station can be obtained, and the negative sequence current component and the zero sequence current component can be further extracted from the first measuring current. The first measurement current of the preset protection device can be obtained by continuously monitoring a measurement device arranged at the preset protection device, and the measurement device can be a current transformer.
Step 102, determining a current component ratio based on the negative sequence current component and the zero sequence current component;
in this embodiment, after the negative sequence current component and the zero sequence current component are extracted, the current component ratio may be further calculated by the negative sequence current component and the zero sequence current component. For example, I gs For presetting a first measuring current corresponding to the protection device,and->Representing the zero sequence current component and the negative sequence current component, respectively, of the first measured current, the current component ratio y can be expressed as +.>
Step 103, judging a fault section of the single-phase earth fault according to the current component ratio, wherein the fault section is one of an intra-zone fault, a forward extra-zone fault and a reverse extra-zone fault;
in this embodiment, after the current component ratio is calculated, it may be determined, based on the current component ratio, which fault section of the single-phase earth fault of the ac output line of the soft direct current converter station specifically belongs to, where the fault section may include an intra-zone fault, a forward extra-zone fault, a reverse extra-zone fault, and the like, and the fault section may be one of them.
And 104, when the fault section is an intra-area fault and a preset action condition is met, controlling the corresponding preset protection device to act.
In this embodiment, if it is determined that the fault section is found to be an intra-zone fault, and at the same time, the result of the finding satisfies the preset action condition by calculating based on the measured current, the measured voltage value, and the like at the preset protection device, then the preset protection device may be controlled to act, specifically, the preset protection device outlet breaker trip signal may be controlled to control the corresponding breaker to trip.
By applying the technical scheme of the embodiment, when the single-phase grounding fault of the alternating current sending-out line of the soft direct current converter station is judged, the first measuring current of the preset protection device on the alternating current sending-out line of the soft direct current converter station can be obtained, and the negative sequence current component and the zero sequence current component can be further extracted from the first measuring current. The current component ratio can then be calculated from the negative sequence current component and the zero sequence current component. Then, based on the ratio of the current components, it can be determined which fault section of the single-phase earth fault of the ac outgoing line of the soft direct current converter station specifically belongs, wherein the fault section can include an intra-zone fault, a forward-zone fault, a reverse-zone fault, and the like. If the fault section is judged to be the fault in the zone and the preset action condition is met, the action of the preset protection device can be controlled. According to the embodiment of the application, when judging whether the fault section of the alternating current outgoing line of the soft direct current converter station is an intra-area fault or not, the transition resistor is not involved, and the influence of the size and the property of the transition resistor on a judgment result is eliminated in principle, so that the accuracy of the intra-area fault judgment result in the single-phase grounding fault time zone can be greatly improved, and the correct action of distance protection is ensured.
Further, as a refinement and extension of the specific implementation manner of the foregoing embodiment, in order to fully describe the specific implementation process of the embodiment, another single-phase grounding distance protection method is provided, which is applied to a soft direct current converter station ac output line, as shown in fig. 3, and the method includes:
step 201, when it is determined that the ac outgoing line of the soft direct current converter station is a single-phase earth fault, obtaining a first measurement current corresponding to a preset protection device, and extracting a negative sequence current component and a zero sequence current component from the first measurement current, where the preset protection device is disposed at one side of an ac system;
step 202, determining a current component ratio based on the negative sequence current component and the zero sequence current component;
step 203, comparing the absolute value of the current component ratio with a preset ratio threshold value to obtain a comparison result;
in this embodiment, after the current component ratio is calculated, the absolute value of the current component ratio and the preset ratio threshold may be compared, so that a comparison result may be obtained correspondingly. Specifically, the preset ratio threshold may be set to 1, and the magnitude relationship between γ and 1 may be compared.
Step 204, when the comparison result indicates that the absolute value is smaller than the preset ratio threshold, determining that the fault section is a reverse out-of-zone fault;
in this embodiment, if the absolute value of the current component ratio is found to be smaller than the preset ratio threshold value by comparison, then it may be determined directly that the fault section of the single-phase earth fault is a reverse out-of-zone fault. For example, if γ < 1, then the failure zone of the single-phase earth fault is directly judged to be the reverse out-of-zone fault.
Step 205, when the comparison result indicates that the absolute value is greater than the preset ratio threshold, obtaining target data, where the target data includes zero sequence impedance corresponding to the ac output line, zero sequence impedance of a transformer at a soft dc converter station side, zero sequence voltage component of the preset protection device, and the zero sequence current component;
in this embodiment, if the absolute value of the ratio of the current components is found to be greater than the preset ratio threshold value by comparison, then it is not possible to determine whether the fault section of the single-phase earth fault is an intra-zone fault or a forward-zone fault at this time, and further determination is required. For example, if γ > 1, it is necessary to further determine whether the failure zone of the single-phase earth failure is an intra-zone failure or a forward-out-of-zone failure. Specifically, target data including the zero-sequence impedance corresponding to the ac outgoing line, the zero-sequence impedance of the transformer at the soft dc converter station side, the zero-sequence voltage component of the preset protection device, and the zero-sequence current component can be acquired. The zero sequence impedance corresponding to the alternating current sending-out line is determined after the line construction is completed; the zero sequence impedance of the transformer at the side of the soft direct current converter station can be directly determined according to the selection of the transformer after the transformer at the side of the soft direct current converter station is installed; the zero sequence voltage component of the preset protection device can be obtained by extracting a first measurement voltage monitored by a voltage transformer arranged at the preset protection device, and it is noted that the first measurement current and the first measurement voltage are currents and voltages corresponding to the same sampling point.
Step 206, calculating a first fault point position based on the target data and the current component ratio;
in this embodiment, the first fault point location may then be calculated based on the target data and the current component ratio. Specifically, assume thatZero sequence impedance corresponding to AC outgoing line, < >>Zero sequence impedance of transformer at side of soft direct current converter station,/->Equivalent zero-sequence impedance of the back side of the alternating current system side can be achieved by +.>Calculated out of->For the zero sequence voltage component at the preset protection device, < >>For the zero sequence current component at the preset protection device, the first fault point position α' can be calculated by: />
Step 207, when the first fault point position is greater than a preset position, determining that the fault section is a positive out-of-zone fault;
in this embodiment, a predetermined location may be determined and the calculated first fault point location may be compared to the predetermined location to determine the fault section. Specifically, referring to the conventional distance protection setting protection range of 80% of the total line length, a preset position may be set to be α set =80%. Thus, if α' > α set I.e. the first fault point position is greater than the preset position, it may be determined that the faulty section is a positive out-of-zone fault.
Step 208, determining that the fault section is an intra-zone fault when the first fault point position is less than or equal to the preset position;
in this embodiment, if it is judged that the first failure point position is found to be less than or equal to the preset position, i.e., α' +.α set Then it may be determined that the failed segment is an intra-zone failure.
Step 209, when the fault section is an intra-area fault, obtaining second measurement currents corresponding to a preset number of sampling points, which are adjacent to the first measurement currents, of the preset protection device after the first measurement currents;
in this embodiment, if it is determined that the fault section is found to be an intra-zone fault, the second measurement current corresponding to the preset number of sampling points of the preset protection device after the first measurement current may also be obtained. For example, if the sampling point of the first measurement current of the preset protection device is the first sampling point and the preset number is 5, then the measurement currents from the second sampling point to the sixth sampling point may be acquired as the second measurement current.
Step 210, calculating a corresponding second fault point position based on each second measurement current;
in this embodiment, the second measurement current corresponding to each sampling point can be expressed by the formulaAnd calculating to obtain a second fault point position. Wherein, gamma in the formula can be calculated by the negative sequence current component and the zero sequence current component of the second measuring current, +.>The zero sequence voltage component extracted from the second measurement voltage corresponding to each sampling point by the preset protection device and the zero sequence current component extracted from the second measurement current corresponding to the sampling point can be calculated based on the zero sequence voltage component extracted from the second measurement voltage corresponding to the sampling point by the preset protection device.
Step 211, calculating a target standard deviation of a target set when the second fault point positions are smaller than or equal to the preset positions, wherein the target set comprises the first fault point positions and the second fault point positions;
in this embodiment, the target set may be composed of a first failure point location and a preset number of second failure point locations. For example, the preset number is 5, and each sampling point in the 5 sampling points corresponds to one second fault point position, so that the target set can include 6 fault point positions in total, namely, the first fault point position and the 5 second fault point positions. If the calculated positions of the second fault points corresponding to the preset number of sampling points are all smaller than or equal to the preset positions, the target standard deviation corresponding to the target set can be further calculated. For example, the first fault point location is α' 1 The positions of the 5 second fault points are alpha' 2 ～α′ 6 Then the target standard deviation can be expressed asWherein,
and step 212, when the target standard deviation is smaller than a preset standard deviation, determining that the preset action condition is met, and controlling the corresponding preset protection device to act.
In this embodiment, if the calculated target standard deviation is smaller than the preset standard deviation, it may be determined that the preset action condition is satisfied at this time, and the preset protection device may be controlled to act, and in particular, the preset protection device outlet breaker trip signal may be controlled to control the corresponding breaker to trip. According to the embodiment of the application, the fault position is obtained by utilizing the comprehensive sequence component ratio of the local negative sequence current and the zero sequence current on the alternating current system side of the alternating current transmission line of the soft direct current converter station, the inter-station communication is not needed, the influence of the communication problem is avoided, and the problem that the single-phase grounding distance protection performance is reduced in the alternating current transmission line scene of the single-ended large inverter power supply is solved. In addition, the intra-area fault judging method in the embodiment of the application does not relate to positive sequence current, eliminates the influence of grid-connected system strength on protection, and can adapt to grid-connected scenes of soft direct access to a weak power grid; meanwhile, the protection setting is simple and direct, and the accurate discrimination of faults in and out of the area can be realized.
In an embodiment of the present application, optionally, the method further includes: and when any one of the second fault point positions is larger than the preset position, determining that the preset action condition is not met.
In this embodiment, if any one of the calculated preset number of second fault point positions is greater than the preset position, that is, one or more second fault point positions are greater than the preset position, it may be determined that the preset action condition is not satisfied at this time, and the preset protection device is not controlled to act at this time.
It should be noted that, if, among the preset number of second fault point positions, a certain second fault point position is greater than the preset position, the second fault point positions of the subsequent sampling points are all smaller than or equal to the preset position, then the sampling point after the sampling point corresponding to the second fault point position greater than the preset position may be taken as the first sampling point, and if, in the following, the preset number of second fault point positions is smaller than or equal to the preset position, and the target standard deviation of the target set corresponding to the sampling points is smaller than the preset standard deviation, then the preset action condition may be determined to be satisfied as well. For example, the preset number is 5, the second fault point positions include 5, namely, the second fault point positions 1 to 5, and the sampling time of the 5 second fault point positions is from far to near, wherein the sampling point corresponding to the second fault point position 5 is closest to the current time. If the second fault point position 2 is greater than the preset position, the remaining 4 second fault point positions are less than or equal to the preset position, the sampling point corresponding to the second fault point position 3 may be used as the first sampling point, and since the second fault point position 4 and the second fault point position 5 satisfy the condition of less than or equal to the preset position, the second fault point positions corresponding to 3 sampling points are determined in addition, the second fault point positions corresponding to 3 sampling points may be recorded as the second fault point positions 6 to 8, and the sampling time is the time corresponding to the adjacent three sampling points after the sampling point corresponding to the second fault point position 5. If the second fault point position 6 to the second fault point position 8 are all smaller than or equal to the preset position, then the target set may include the second fault point position 3 to the second fault point position 8, and the target standard deviation may be calculated according to the 6 fault point positions.
In this embodiment of the present application, optionally, the preset protection device is provided with a current transformer, and the first measurement current and the second measurement current are acquired according to a preset sampling frequency based on the current transformer.
In this embodiment, the first measurement current, the second measurement current, and the like corresponding to the preset protection device may be obtained by monitoring a current transformer provided at the preset protection device, where the current transformer may collect the first measurement current and the second measurement current according to a preset sampling frequency. For example, the preset sampling frequency may be 1200Hz. Likewise, the first measured voltage and the second measured voltage may be obtained by monitoring a voltage transformer provided at a preset protection device, where the voltage transformer may collect the first measured voltage and the second measured voltage according to a preset sampling frequency.
In an embodiment of the present application, optionally, before step 201, the method further includes: and monitoring the current and the voltage of the alternating current outgoing line of the soft direct current converter station, and when monitoring that the preset protection device sends out a fault signal, identifying the fault type of the alternating current outgoing line of the soft direct current converter station by the complete phase selection element based on the current and the voltage.
In this embodiment, the fault signal, current, voltage and the like of the ac outgoing line of the soft direct current converter station may also be monitored in real time, where the preset protection device on the ac system side may monitor the fault of the ac outgoing line of the soft direct current converter station, and may correspondingly send a fault signal when the fault is monitored. If the preset protection device is monitored to send out a fault signal, the phase selection element set can judge what fault type the alternating current sending-out line is according to the current and the voltage, wherein the fault type can be one of a plurality of types such as single-phase grounding faults and the like. The phase selection kit may be arranged on the ac outlet line of the soft-dc converter station.
In an embodiment of the present application, optionally, the method further includes: returning to the step of monitoring a fault signal of the alternating current outgoing line of the flexible direct current converter station when the fault section is the positive out-of-zone fault or the reverse out-of-zone fault; and/or when the fault section is an intra-area fault and the preset action condition is not met, returning to the step of monitoring the fault signal of the alternating current outgoing line of the flexible direct current converter station.
In this embodiment, if it is judged that the single-phase earth fault is found not to be an intra-zone fault but to be a forward-out-of-zone fault or a reverse-out-of-zone fault, the preset protection device is not operated, and the monitoring of the fault signal of the ac outgoing line of the soft direct current converter station may be continued, and when the fault signal is monitored again, the above-described procedure of determining the fault section may be repeated. In addition, when the fault section is an intra-area fault but the preset action condition is not satisfied at this time, the preset protection device does not act at this time, and the fault signal of the ac outgoing line of the soft direct current converter station can be continuously monitored, and when the fault signal is monitored again, the above-mentioned flow of determining the fault section can be repeated.
Furthermore, in order to illustrate the implementation effect of the embodiment, a verification result is provided, and the result shows that when faults in the transition resistance generation areas with different sizes occur, the faults can be identified within 30ms by the protection provided by the embodiment of the application, and the protection has stronger transition resistance capability; when external faults occur through transition resistors with different sizes, the protection provided by the embodiment of the application can be reliable and non-action, and has stronger transition resistance capability; and the alpha calculated by the protection algorithm can accurately reflect the fault position, so that the accuracy of the fault position calculation in the application is further verified.
Further, as can be seen from table 1, the transition resistance exhibits inductive character, the protection provided can still operate correctly, and the calculated α of the protection after a fault can reflect the fault location correctly, so the protection provided is not affected by the nature of the transition resistance.
TABLE 1 protection action conditions of the present application under the influence of resistive-inductive transition resistance
As can be seen from table 2, under the system scene of soft direct grid connection and different intensities, if a metallic single-phase grounding fault occurs, the traditional protection and the application can act correctly; along with the increase of the transition resistance, the traditional distance protection measurement impedance criterion is influenced to generate large-amplitude non-resistive additional impedance, so that correct action cannot be performed, and the influence is more obvious in a weaker scene of the grid-connected system. The protection provided by the application can accurately act in different grid-connected system scenes.
TABLE 2 distance protection action conditions under different intensity grid connected systems
Further, as a specific implementation of the method of fig. 1, an embodiment of the present application provides a single-phase grounding distance protection device, which is applied to a flexible direct current converter station ac output line, as shown in fig. 4, and includes:
the current component extraction module is used for obtaining a first measuring current corresponding to a preset protection device when the alternating current outgoing line of the flexible direct current converter station is judged to be in single-phase earth fault, and extracting a negative sequence current component and a zero sequence current component from the first measuring current, wherein the preset protection device is arranged at one side of an alternating current system;
the ratio determining module is used for determining a current component ratio based on the negative sequence current component and the zero sequence current component;
the fault section judging module is used for judging a fault section of the single-phase earth fault according to the current component ratio, wherein the fault section is one of an intra-zone fault, a forward extra-zone fault and a reverse extra-zone fault;
and the control module is used for controlling the corresponding preset protection device to act when the fault section is an intra-area fault and the preset action condition is met.
Optionally, the fault section judging module is configured to:
comparing the absolute value of the current component ratio with a preset ratio threshold value to obtain a comparison result; when the comparison result indicates that the absolute value is smaller than the preset ratio threshold, determining that the fault section is a reverse out-of-zone fault; when the comparison result indicates that the absolute value is larger than the preset ratio threshold, target data are obtained, wherein the target data comprise zero sequence impedance corresponding to the alternating current sending line, zero sequence impedance of a transformer at a soft direct current converter station side, zero sequence voltage components of the preset protection device and zero sequence current components; calculating a first fault point location based on the target data and the current component ratio; when the position of the first fault point is larger than a preset position, determining that the fault section is a positive out-of-zone fault; and when the first fault point position is smaller than or equal to the preset position, determining that the fault section is an intra-area fault.
Optionally, the apparatus further comprises:
the current acquisition module is used for acquiring second measuring currents which are obtained by the preset protection device after the first measuring currents and correspond to a preset number of sampling points adjacent to the first measuring currents after the fault section is an intra-area fault;
a position calculation module, configured to calculate a corresponding second fault point position based on each of the second measurement currents;
the standard deviation calculation module is used for calculating a target standard deviation of a target set when the second fault point positions are smaller than or equal to the preset positions, wherein the target set comprises the first fault point positions and the second fault point positions;
and the judging module is used for determining that the preset action condition is met when the target standard deviation is smaller than a preset standard deviation.
Optionally, the judging module is further configured to:
and when any one of the second fault point positions is larger than the preset position, determining that the preset action condition is not met.
Optionally, the preset protection device is provided with a current transformer, and the first measurement current and the second measurement current are acquired according to a preset sampling frequency based on the current transformer.
Optionally, the apparatus further comprises:
and the monitoring module is used for monitoring the current and the voltage of the alternating current outgoing line of the flexible direct current converter station before judging that the alternating current outgoing line of the flexible direct current converter station is in single-phase grounding fault, and identifying the fault type of the alternating current outgoing line of the flexible direct current converter station based on the current and the voltage by the complete phase selection element when monitoring that the preset protection device sends out a fault signal.
Optionally, the apparatus further comprises:
the return module is used for returning to the step of monitoring the fault signal of the alternating current outgoing line of the flexible direct current converter station when the fault section is the positive out-of-zone fault or the reverse out-of-zone fault; and/or when the fault section is an intra-area fault and the preset action condition is not met, returning to the step of monitoring the fault signal of the alternating current outgoing line of the flexible direct current converter station.
It should be noted that, for other corresponding descriptions of each functional unit related to the single-phase grounding distance protection device provided in the embodiment of the present application, reference may be made to corresponding descriptions in the methods of fig. 1 to 3, which are not repeated herein.
Based on the above-mentioned method shown in fig. 1 to 3, correspondingly, the embodiment of the present application further provides a storage medium, on which a computer program is stored, which when executed by a processor, implements the above-mentioned single-phase grounding distance protection method shown in fig. 1 to 3.
Based on such understanding, the technical solution of the present application may be embodied in the form of a software product, which may be stored in a non-volatile storage medium (may be a CD-ROM, a U-disk, a mobile hard disk, etc.), and includes several instructions for causing a computer device (may be a personal computer, a server, or a network device, etc.) to perform the methods described in various implementation scenarios of the present application.
Based on the method shown in fig. 1 to 3 and the virtual device embodiment shown in fig. 4, in order to achieve the above object, the embodiment of the present application further provides a computer device, which may specifically be a personal computer, a server, a network device, etc., where the computer device includes a storage medium and a processor; a storage medium storing a computer program; a processor for executing a computer program to implement the single phase earth distance protection method as described above and shown in fig. 1 to 3.
Optionally, the computer device may also include a user interface, a network interface, a camera, radio Frequency (RF) circuitry, sensors, audio circuitry, WI-FI modules, and the like. The user interface may include a Display screen (Display), an input unit such as a Keyboard (Keyboard), etc., and the optional user interface may also include a USB interface, a card reader interface, etc. The network interface may optionally include a standard wired interface, a wireless interface (e.g., bluetooth interface, WI-FI interface), etc.
It will be appreciated by those skilled in the art that the architecture of a computer device provided in the present embodiment is not limited to the computer device, and may include more or fewer components, or may combine certain components, or may be arranged in different components.
The storage medium may also include an operating system, a network communication module. An operating system is a program that manages and saves computer device hardware and software resources, supporting the execution of information handling programs and other software and/or programs. The network communication module is used for realizing communication among all components in the storage medium and communication with other hardware and software in the entity equipment.
From the above description of the embodiments, it will be apparent to those skilled in the art that the present application may be implemented by means of software plus necessary general hardware platforms, or may be implemented by hardware. When it is determined that a single-phase earth fault occurs in the ac outgoing line of the soft-direct current converter station, a first measurement current of a preset protection device on the ac outgoing line of the soft-direct current converter station can be obtained, and a negative sequence current component and a zero sequence current component can be further extracted from the first measurement current. The current component ratio can then be calculated from the negative sequence current component and the zero sequence current component. Then, based on the ratio of the current components, it can be determined which fault section of the single-phase earth fault of the ac outgoing line of the soft direct current converter station specifically belongs, wherein the fault section can include an intra-zone fault, a forward-zone fault, a reverse-zone fault, and the like. If the fault section is judged to be the fault in the zone and the preset action condition is met, the action of the preset protection device can be controlled. According to the embodiment of the application, when judging whether the fault section of the alternating current outgoing line of the soft direct current converter station is an intra-area fault or not, the transition resistor is not involved, and the influence of the size and the property of the transition resistor on a judgment result is eliminated in principle, so that the accuracy of the intra-area fault judgment result in the single-phase grounding fault time zone can be greatly improved, and the correct action of distance protection is ensured.
Those skilled in the art will appreciate that the drawings are merely schematic illustrations of one preferred implementation scenario, and that the modules or flows in the drawings are not necessarily required to practice the present application. Those skilled in the art will appreciate that modules in an apparatus in an implementation scenario may be distributed in an apparatus in an implementation scenario according to an implementation scenario description, or that corresponding changes may be located in one or more apparatuses different from the implementation scenario. The modules of the implementation scenario may be combined into one module, or may be further split into a plurality of sub-modules.
The foregoing application serial numbers are merely for description, and do not represent advantages or disadvantages of the implementation scenario. The foregoing disclosure is merely a few specific implementations of the present application, but the present application is not limited thereto and any variations that can be considered by a person skilled in the art shall fall within the protection scope of the present application.
Claims (10)
1. A single-phase grounding distance protection method applied to a flexible direct current converter station alternating current outgoing line, characterized by comprising the following steps:
when the alternating current sending-out line of the soft direct current converter station is judged to be in single-phase grounding fault, a first measuring current corresponding to a preset protection device is obtained, a negative sequence current component and a zero sequence current component are extracted from the first measuring current, and the preset protection device is arranged on one side of an alternating current system;
determining a current component ratio based on the negative sequence current component and the zero sequence current component;
judging a fault section of the single-phase earth fault according to the current component ratio, wherein the fault section is one of an intra-zone fault, a forward extra-zone fault and a reverse extra-zone fault;
and when the fault section is an intra-zone fault and a preset action condition is met, controlling the corresponding preset protection device to act.
2. The method of claim 1, wherein said determining a fault section of said single phase-to-earth fault based on said current component ratio comprises:
comparing the absolute value of the current component ratio with a preset ratio threshold value to obtain a comparison result;
when the comparison result indicates that the absolute value is smaller than the preset ratio threshold, determining that the fault section is a reverse out-of-zone fault;
when the comparison result indicates that the absolute value is larger than the preset ratio threshold, target data are obtained, wherein the target data comprise zero sequence impedance corresponding to the alternating current sending line, zero sequence impedance of a transformer at a soft direct current converter station side, zero sequence voltage components of the preset protection device and zero sequence current components;
calculating a first fault point location based on the target data and the current component ratio;
when the position of the first fault point is larger than a preset position, determining that the fault section is a positive out-of-zone fault;
and when the first fault point position is smaller than or equal to the preset position, determining that the fault section is an intra-area fault.
3. The method of claim 1, wherein after the failed segment is an intra-zone failure, the method further comprises:
acquiring second measuring currents which are obtained by the preset protection device after the first measuring currents and correspond to a preset number of sampling points adjacent to the first measuring currents;
calculating a corresponding second fault point location based on each of the second measured currents;
when the second fault point positions are smaller than or equal to the preset positions, calculating a target standard deviation of a target set, wherein the target set comprises the first fault point positions and the second fault point positions;
and when the target standard deviation is smaller than a preset standard deviation, determining that the preset action condition is met.
4. A method according to claim 3, characterized in that the method further comprises:
and when any one of the second fault point positions is larger than the preset position, determining that the preset action condition is not met.
5. A method according to claim 3, wherein the preset protection device is provided with a current transformer, and the first measurement current and the second measurement current are acquired according to a preset sampling frequency based on the current transformer.
6. The method of claim 1, wherein prior to determining that the soft dc converter ac outgoing line is a single phase ground fault, the method further comprises:
and monitoring the current and the voltage of the alternating current outgoing line of the soft direct current converter station, and when monitoring that the preset protection device sends out a fault signal, identifying the fault type of the alternating current outgoing line of the soft direct current converter station by the complete phase selection element based on the current and the voltage.
7. The method of claim 6, wherein the method further comprises:
returning to the step of monitoring a fault signal of the alternating current outgoing line of the flexible direct current converter station when the fault section is the positive out-of-zone fault or the reverse out-of-zone fault; and/or the number of the groups of groups,
and when the fault section is an intra-area fault and the preset action condition is not met, returning to the step of monitoring the fault signal of the alternating current outgoing line of the soft direct current converter station.
8. A single-phase ground distance protection device applied to a flexible direct current converter station ac outgoing line, comprising:
the current component extraction module is used for obtaining a first measuring current corresponding to a preset protection device when the alternating current outgoing line of the flexible direct current converter station is judged to be in single-phase earth fault, and extracting a negative sequence current component and a zero sequence current component from the first measuring current, wherein the preset protection device is arranged at one side of an alternating current system;
the ratio determining module is used for determining a current component ratio based on the negative sequence current component and the zero sequence current component;
the fault section judging module is used for judging a fault section of the single-phase earth fault according to the current component ratio, wherein the fault section is one of an intra-zone fault, a forward extra-zone fault and a reverse extra-zone fault;
and the control module is used for controlling the corresponding preset protection device to act when the fault section is an intra-area fault and the preset action condition is met.
9. A storage medium having stored thereon a computer program, which when executed by a processor, implements the method of any of claims 1 to 7.
10. A computer device comprising a storage medium, a processor and a computer program stored on the storage medium and executable on the processor, characterized in that the processor implements the method of any one of claims 1 to 7 when executing the computer program.
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