CN111562424A - Voltage sag source identification method and system considering transformer propagation characteristics - Google Patents
Voltage sag source identification method and system considering transformer propagation characteristics Download PDFInfo
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R19/0084—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring voltage only
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R19/02—Measuring effective values, i.e. root-mean-square values
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- G—PHYSICS
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/62—Testing of transformers
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Abstract
The invention discloses a voltage sag source identification method considering the propagation characteristics of a transformer, which comprises the steps of judging whether voltage sag occurs or not according to monitored three-phase voltage; responding to the voltage sag, and calculating a half-wave true effective value, a positive sequence component, a negative sequence component and a zero sequence component of the three-phase voltage according to the monitored three-phase voltage; and identifying the voltage sag type according to the half-wave true effective value, the positive sequence component, the negative sequence component and the zero sequence component of the three-phase voltage and a preset judgment rule. A corresponding system is also disclosed. The method is based on the half-wave true effective value, the positive sequence component, the negative sequence component and the zero sequence component of the three-phase voltage, effectively identifies the voltage sag source type caused by the short-circuit fault, and can provide beneficial reference for operation management, accident investigation, fault location and the like of the power system.
Description
Technical Field
The invention relates to a voltage sag source identification method and system considering transformer propagation characteristics, and belongs to the technical field of power quality analysis.
Background
The voltage sag (voltage sag) refers to the problem of power quality that the effective value of the power supply voltage is rapidly reduced to 90% -10% of the rated voltage and then is recovered to the value close to the normal value, and the typical duration time is 10 ms-1 min. Power transmission and distribution line faults, transformer switching and large capacity induction motors or other equipment with large starting currents all cause voltage sags of different degrees. The voltage sag caused by the short-circuit fault is inevitable and possibly serious, and is a main reason of the false operation of sensitive equipment, so that the currently installed power quality monitoring device mostly has the voltage sag monitoring function. The voltage sag characteristics caused by different types of short-circuit faults are different, and the power quality monitoring device cannot determine the voltage sag type.
Disclosure of Invention
The invention provides a voltage sag source identification method and system considering transformer propagation characteristics, and solves the problem that a power quality monitoring device cannot determine the voltage sag type.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a voltage sag source identification method considering the propagation characteristics of a transformer comprises the following steps,
judging whether voltage sag occurs or not according to the monitored three-phase voltage;
responding to the voltage sag, and calculating a half-wave true effective value, a positive sequence component, a negative sequence component and a zero sequence component of the three-phase voltage according to the monitored three-phase voltage;
and identifying the voltage sag type according to the half-wave true effective value, the positive sequence component, the negative sequence component and the zero sequence component of the three-phase voltage and a preset judgment rule.
According to the half-wave true effective value, the positive sequence component, the negative sequence component and the zero sequence component of the three-phase voltage and the preset judgment rule, the process of identifying the voltage sag type comprises the following steps,
step 2, if the negative sequence component is 0, the voltage sag type is voltage sag caused by three-phase short-circuit fault; if the negative sequence component is not 0, turning to step 3;
step 3, if the zero sequence component is not 0, turning to step 4, and if the zero sequence component is 0, turning to step 5;
step 4, if the absolute value of the sum of the positive sequence component and the negative sequence component is greater than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by two-phase ground faults; if the absolute value of the sum of the positive sequence component and the negative sequence component is smaller than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by single-phase earth fault;
step 5, if the half-wave true effective value of one phase voltage is unchanged and the half-wave true effective values of the other phase voltages are reduced, acquiring a previous-stage voltage sag type, and turning to step 6; if the half-wave true effective values of the three-phase voltage are all reduced, turning to the step 7;
step 6, if the voltage sag is caused by the single-phase earth fault, the voltage sag type is the voltage sag caused by the transmission of the single-phase earth fault through a transformer; if not, continuing to obtain the previous voltage sag type, and repeating the step until the voltage sag type is judged;
step 7, if the absolute value of the sum of the positive sequence component and the negative sequence component is greater than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by the transmission of the two-phase ground fault through a transformer; if the absolute value of the sum of the positive sequence component and the negative sequence component is smaller than the absolute value of the difference between the positive sequence component and the negative sequence component, acquiring a previous-stage voltage sag type, and turning to the step 8;
step 8, if the voltage sag is caused by the single-phase earth fault, the voltage sag type is the voltage sag caused by the transmission of the single-phase earth fault through a transformer; if the voltage sag is caused by the two-phase ground fault or the voltage sag is caused by the two-phase ground fault propagating through the transformer, the voltage sag type is the voltage sag caused by the two-phase ground fault propagating through the transformer; otherwise, continuously acquiring the voltage sag type of the previous stage, and repeating the step until the voltage sag type is judged.
In response to no voltage sag occurring, the three phase voltages continue to be monitored.
And if the voltage of a certain phase meets the voltage sag condition, judging that the voltage sag occurs.
A voltage sag source identification system that takes into account transformer propagation characteristics, comprising,
a generation judgment module: judging whether voltage sag occurs or not according to the monitored three-phase voltage;
a calculation module: responding to the voltage sag, and calculating a half-wave true effective value, a positive sequence component, a negative sequence component and a zero sequence component of the three-phase voltage according to the monitored three-phase voltage;
a type identification module: and identifying the voltage sag type according to the half-wave true effective value, the positive sequence component, the negative sequence component and the zero sequence component of the three-phase voltage and a preset judgment rule.
The type-identifying module includes a type-identifying module,
a first judgment module: if the absolute value of the difference value of the true effective values of the half-wave of the three-phase voltage is smaller than the minimum value of the preset interval, the voltage sag type is the voltage sag caused by the three-phase short-circuit fault; if the absolute value of the difference value of the true effective values of the half-waves of the three-phase voltage is within the preset interval, the third judgment module is switched to;
a second judging module: if the negative sequence component is 0, the voltage sag type is voltage sag caused by three-phase short-circuit fault; if the negative sequence component is not 0, switching to a third judgment module;
a third judging module: if the zero sequence component is not 0, the fourth judgment module is switched to, and if the zero sequence component is 0, the fifth judgment module is switched to;
a fourth judging module: if the absolute value of the sum of the positive sequence component and the negative sequence component is greater than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by two-phase ground faults; if the absolute value of the sum of the positive sequence component and the negative sequence component is smaller than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by single-phase earth fault;
a fifth judging module: if the half-wave true effective value of one phase voltage is unchanged and the half-wave true effective values of the other phase voltages are reduced, acquiring a previous-stage voltage sag type, and switching to a sixth judgment module; if the half-wave true effective values of the three-phase voltage are all reduced, the seventh judgment module is switched to;
a sixth judging module: if the voltage sag is caused by the single-phase earth fault, the voltage sag type is the voltage sag caused by the transmission of the single-phase earth fault through the transformer; if not, continuing to obtain the previous voltage sag type, and repeating the module judgment process until the voltage sag type is judged;
a seventh judging module: if the absolute value of the sum of the positive sequence component and the negative sequence component is greater than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by the transmission of the two-phase ground fault through the transformer; if the absolute value of the sum of the positive sequence component and the negative sequence component is smaller than the absolute value of the difference between the positive sequence component and the negative sequence component, acquiring a voltage sag type of the previous stage, and turning to an eighth judging module;
an eighth judging module: if the voltage sag is caused by the single-phase earth fault, the voltage sag type is the voltage sag caused by the transmission of the single-phase earth fault through the transformer; if the voltage sag is caused by the two-phase ground fault or the voltage sag is caused by the two-phase ground fault propagating through the transformer, the voltage sag type is the voltage sag caused by the two-phase ground fault propagating through the transformer; otherwise, continuing to obtain the voltage sag type of the previous stage, and repeating the judgment process of the module until the voltage sag type is judged.
The three-phase voltage monitoring system is characterized by further comprising a monitoring module used for monitoring the three-phase voltage, the monitoring module sends the three-phase voltage to the generation judging module, the monitoring module receives feedback of the generation judging module, and if voltage sag does not occur in the feedback, the monitoring module continues to monitor the three-phase voltage.
If a certain phase voltage meets the voltage sag condition, the generation judgment module judges that the voltage sag occurs.
A computer readable storage medium storing one or more programs, the one or more programs comprising instructions, which when executed by a computing device, cause the computing device to perform a voltage sag source identification method that takes into account transformer propagation characteristics.
A computing device comprising one or more processors, memory, and one or more programs stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for performing a voltage sag source identification method that accounts for transformer propagation characteristics.
The invention achieves the following beneficial effects: the method is based on the half-wave true effective value, the positive sequence component, the negative sequence component and the zero sequence component of the three-phase voltage, effectively identifies the voltage sag source type caused by the short-circuit fault, and can provide beneficial reference for operation management, accident investigation, fault location and the like of the power system.
Drawings
Fig. 1(a) is a composite sequence network diagram when a single-phase earth fault occurs in an electric power system;
FIG. 1(b) is a composite sequence diagram of a two-phase ground fault in an electrical power system;
FIG. 1(c) is a composite sequence diagram of a two-phase short circuit fault occurring in an electrical power system;
FIG. 2 is a schematic diagram of a voltage sag type feature vector caused by a short-circuit fault of a neutral grounding system;
FIG. 3(a) is a zero sequence equivalent circuit of the transformer in the first connection mode;
FIG. 3(b) is a zero sequence equivalent circuit of the transformer in the second connection mode;
FIG. 3(c) is a zero sequence equivalent circuit of the transformer in the third connection mode;
FIG. 4 is a graph showing the propagation of voltage sag through a type 2 transformer due to short-circuit fault;
FIG. 5 is a graph showing the propagation of voltage sag through a type 3 transformer due to short-circuit fault;
fig. 6 is a flow chart of the present recognition.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
FIG. 1(a), FIG. 1(b) and FIG. 1(c) are composite sequence network diagrams respectively showing the occurrence of single-phase earth fault, two-phase earth fault and two-phase short-circuit fault in the power system, wherein ZSImpedance equivalent to the present voltage level, Z, of the systemFFor the line impedance at the short-circuit point to the Point of Common Coupling (PCC), the voltage sag caused by a three-phase short circuit will not have a phase angle jump, assuming that the impedance angle of the system impedance and the line impedance are equal.
For a single-phase earth fault, the composite sequence network is shown in fig. 1(a), and the expressions of the positive sequence component, the negative sequence component and the zero sequence component are as follows:
in (1),
respectively positive, negative and zero sequence components, ZS1、ZS2、ZS0Positive, negative and zero sequence impedances, Z, equivalent to the present voltage level, respectivelyF1、ZF2、ZF0Respectively, positive, negative and zero sequence impedances of the line from the short-circuit point to the Point of Common Coupling (PCC).
The expression of each phase voltage is as follows:
wherein the content of the first and second substances,
respectively are A phase voltage, B phase voltage and C phase voltage,
order to
For a two-phase ground fault, the composite sequence network is shown in fig. 1(b), and the expressions of the positive sequence component, the negative sequence component and the zero sequence component are:
the expression of each phase voltage is as follows:
wherein D ═ ZS1+ZF1)(ZS0+ZF0+ZS2+ZF2)+(ZS0+ZF0)(ZS2+ZF2)。
For a two-phase short-circuit fault, a composite sequence network is shown in fig. 1(c), and positive sequence components, negative sequence components and zero sequence components are expressed as follows:
the expression of each phase voltage is as follows:
the voltage sag caused by the three-phase short-circuit fault is approximately the same as the three-phase voltage amplitude value decrease, and the phase angle is kept unchanged, so that the fault belongs to a symmetrical fault.
The neutral points of the systems of 110kV and above and the 0.38kV system in China are generally directly grounded, except for the fact that Z may appear in the system of 500kV and above voltage classS0/ZS1General Z of < 1, 220kV and 110kV systemsS0/ZS1Greater than or close to 1. Thus, assume Z of an effective grounding systemS0＝ZS1Assuming infinite power supply capacity, ZS1＝ZS2. Will ZS1＝ZS2And ZS0/ZS1Substituting 1, the types of voltage sags caused by different short-circuit faults are summarized in table 1 below (in the formula, U is determined by the fault impedance and the system impedance), and the characteristic vector diagram is shown in fig. 2.
TABLE 1 INDUCTION TABLE FOR VOLTAGE SLIPPER TYPE CAUSED BY SHORT-CIRCUIT FAULT
After the voltage sag propagates through the transformer, the characteristic quantity may change, and the change varies with the wiring mode of the transformer. The transformers of Y0/Y-12, Y/Y0-12, Y/delta-11 and Y0/delta-11 connection modes do not allow zero-sequence components in the voltage sag characteristic quantity to pass through, and the transformers are divided into three connection modes according to the propagation condition of the zero-sequence components in the transformers.
The transformer has star-shaped connection on both sides and grounded neutral point, when zero-sequence current flows through the primary side, zero-sequence potential is induced in each winding on the secondary side, and a zero-sequence equivalent circuit is shown in figure 3(a) and named as a type 1 transformer, and the common connection model is Y0/Y0-12. The type 1 transformer allows positive, negative and zero sequence components to pass through, and no phase angle occursTherefore, the secondary side and the primary side have the same voltage sag, and the phase voltage transfer matrix is:
assuming that the per unit value transformation ratio of the primary side voltage and the secondary side voltage of the transformer is 1: the two sides of the 1, 2 type transformer are in star connection mode, at least one side of the transformer is not grounded, zero sequence current can not flow through the transformer, a zero sequence equivalent circuit is shown as a figure 3(b), common connection types are Y0/Y-12, Y/Y0-12 and Y/Y-12, and phase voltage transfer matrixes are as follows:
one side of the 3-type transformer is star-connected, the other side is delta-connected, when the zero-sequence current flows through the star-connected, each winding on the delta-connected will generate induced electromotive force, but because the three phases of the zero-sequence current are equal in size and same in phase, only a circular current is formed in the delta-connected, and the zero-sequence component cannot pass through the circuit except the winding, the zero-sequence equivalent circuit is shown as fig. 3(c), the common connection modes are Y/delta-11 and Y0/delta-11, and the phase voltage transfer matrix is as follows:
when voltage sag caused by single-phase ground fault and two-phase ground fault passes through the type 2 transformer, the amplitude and phase of the secondary side voltage are changed, two new types of voltage sag, which can be called D type and G type, are generated, and the vector diagram is shown in fig. 2.
When a two-phase ground fault occurs in a neutral point active grounding system, a new voltage sag type, which may be called F type, is generated after the two-phase ground fault passes through a type 3 transformer, and a vector diagram of the type F is shown in fig. 2. The new voltage sag types resulting from the propagation of different short-circuit faults through the transformer are summarized in table 2.
TABLE 2 summary of new voltage sag types due to propagation of different short-circuit faults through the transformer
The type 2 transformer can block the propagation of zero sequence components, when voltage sag caused by single-phase ground faults and two-phase ground faults passes through the transformer, the amplitude and the phase of secondary side voltage can be changed, and the propagation rule of the transformer is shown in figure 4.
After a single-phase ground fault (taking a-phase grounding as an example) passes through the primary 2-type transformer, the phase difference of a non-fault phase (B, C-phase) is increased, the amplitude is reduced and is recorded as D-type sag, and after the single-phase ground fault passes through the secondary 2-type transformer, the single-phase ground fault still remains as D-type sag, so that the single-phase ground fault still remains as D-type sag after being transmitted through any multi-stage 2-type transformer.
After a two-phase ground fault (taking B, C-phase ground as an example) passes through the type 2 transformer once, the phase difference of the two faulty phases is reduced, the amplitude of the non-faulty phase (a-phase) is also reduced, which is recorded as a G-type dip, and the second pass through the type 2 transformer still maintains the G-type dip.
And the voltage sag type of the three-phase short-circuit fault and the two-phase short-circuit fault is kept unchanged after passing through the 2-type transformer.
The type 3 transformer not only blocks the passage of the zero sequence component on the primary side, but also generates phase angle displacement on the secondary side, and the propagation law of the phase angle displacement is shown in fig. 5.
After a single-phase grounding fault (taking A-phase grounding as an example) passes through the 3-type transformer once, C-type voltage sag similar to that caused by two-phase short-circuit fault is obtained, the C-type voltage sag is converted into D-type sag after passing through the 3-type transformer again, and the D-type voltage sag is converted back into C-type sag after passing through the 3-type transformer for the third time, which indicates that phase angle displacement is generated.
The voltage sag caused by the two-phase short-circuit fault (for example, B, C-phase short-circuit) is transferred through the type 3 transformer, and then becomes D-type sag, and when the voltage sag passes through the type 3 transformer for the second time, it is changed back to C-type sag again.
The two-phase ground fault (for example, B, C phases are grounded) develops into an F-type temporary drop after passing through the type 3 transformer for the first time, and becomes a G-type temporary drop after passing through the type 3 transformer for the second time, and becomes an F-type temporary drop after passing through the type 3 transformer.
After voltage sag caused by three-phase short circuit passes through a 3-stage transformer, the voltage amplitude is unchanged, and the phase of each phase voltage leads the phase of the primary side by 30 degrees.
The transmission rule of the short circuit sag type of the effective neutral grounding system among different transformers is shown in table 3.
TABLE 3 transfer law of short circuit sag type of neutral point effective grounding system between different transformers
The identification of the voltage sag type needs to calculate the voltage sequence component, seven voltage sag types caused by different short-circuit faults of the effective grounding system of the neutral point are subjected to symmetrical component transformation, and the results of positive, negative and zero sequence voltage components obtained after the transformation, and the sum and difference of the positive and negative sequence voltage components are shown in a table 4.
TABLE 4 results table
Based on the analysis, the voltage sag source identification method considering the propagation characteristics of the transformer comprises the following steps:
s1) judging whether voltage sag occurs or not according to the monitored three-phase voltage, if a certain phase voltage meets the voltage sag condition, judging that the voltage sag occurs, and turning to S2, otherwise, continuing monitoring the three-phase voltage.
S2) calculating a half-wave true effective value, a positive sequence component, a negative sequence component and a zero sequence component of the three-phase voltage according to the monitored three-phase voltage; wherein the positive sequence component, the negative sequence component and the zero sequence component are respectively
S3) identifying the voltage sag type according to the half-wave true effective value, the positive sequence component, the negative sequence component and the zero sequence component of the three-phase voltage and a preset judgment rule.
As shown in fig. 6, the process of identifying the type of voltage sag is as follows:
step 2, if the negative sequence component is 0, the voltage sag type is voltage sag caused by three-phase short-circuit fault (namely type A); if the negative sequence component is not 0, turning to step 3;
step 3, if the zero sequence component is not 0, turning to step 4, and if the zero sequence component is 0, turning to step 5;
step 4, if the absolute value of the sum of the positive sequence component and the negative sequence component is greater than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by two-phase ground fault (namely, type E); if the absolute value of the sum of the positive sequence component and the negative sequence component is smaller than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is the voltage sag caused by the single-phase earth fault (namely B type);
step 5, if the half-wave true effective value of one phase voltage is unchanged and the half-wave true effective values of the other phase voltages are reduced, the C-type voltage sag is obtained, and the step 6 is switched to; if the half-wave true effective values of the three-phase voltage are all reduced, turning to the step 7;
step 6, if the voltage sag is caused by the single-phase earth fault, the voltage sag type is the voltage sag caused by the transmission of the single-phase earth fault through a transformer; if not, C-type or D-type sag, continuously acquiring the voltage sag type of the previous stage, and repeating the step until the voltage sag type is judged;
step 7, if the absolute value of the sum of the positive sequence component and the negative sequence component is greater than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag (G type) caused by the transmission of the two-phase ground fault through the transformer; if the absolute value of the sum of the positive sequence component and the negative sequence component is smaller than the absolute value of the difference between the positive sequence component and the negative sequence component, acquiring a previous-stage voltage sag type, and turning to the step 8;
step 8, if the voltage sag is caused by the single-phase earth fault, the voltage sag type is the voltage sag (D type) caused by the transmission of the single-phase earth fault through the transformer; if the voltage sag is caused by the two-phase ground fault or the voltage sag is caused by the two-phase ground fault propagating through the transformer, the voltage sag type is the voltage sag (F type) caused by the two-phase ground fault propagating through the transformer; otherwise, C, D or F type sag, continuously acquiring the voltage sag of the previous stage, and repeating the steps until the voltage sag type is judged.
The method is based on the half-wave true effective value, the positive sequence component, the negative sequence component and the zero sequence component of the three-phase voltage, comprehensively considers factors such as the sag type, the amplitude change, the transformer connection mode and the like, effectively identifies the voltage sag source type caused by the short-circuit fault, and can provide beneficial reference for operation management, accident investigation, fault location and the like of the power system.
The software system corresponding to the method, namely the voltage sag source identification system considering the propagation characteristics of the transformer comprises,
a monitoring module: for monitoring three-phase voltages; the monitoring module sends the three-phase voltage to the generation judging module, receives feedback of the generation judging module, and if voltage sag does not occur in the feedback, the monitoring module continues to monitor the three-phase voltage.
A generation judgment module: and judging whether voltage sag occurs or not according to the monitored three-phase voltage. If a certain phase voltage meets the voltage sag condition, the generation judgment module judges that the voltage sag occurs.
A calculation module: and responding to the occurrence of voltage sag, and calculating a half-wave true effective value, a positive sequence component, a negative sequence component and a zero sequence component of the three-phase voltage according to the monitored three-phase voltage.
A type identification module: and identifying the voltage sag type according to the half-wave true effective value, the positive sequence component, the negative sequence component and the zero sequence component of the three-phase voltage and a preset judgment rule.
The type recognition module comprises:
a first judgment module: if the absolute value of the difference value of the true effective values of the half-wave of the three-phase voltage is smaller than the minimum value of the preset interval, the voltage sag type is the voltage sag caused by the three-phase short-circuit fault; if the absolute value of the difference value of the true effective values of the half-waves of the three-phase voltage is within the preset interval, the third judgment module is switched to;
a second judging module: if the negative sequence component is 0, the voltage sag type is voltage sag caused by three-phase short-circuit fault; if the negative sequence component is not 0, switching to a third judgment module;
a third judging module: if the zero sequence component is not 0, the fourth judgment module is switched to, and if the zero sequence component is 0, the fifth judgment module is switched to;
a fourth judging module: if the absolute value of the sum of the positive sequence component and the negative sequence component is greater than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by two-phase ground faults; if the absolute value of the sum of the positive sequence component and the negative sequence component is smaller than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by single-phase earth fault;
a fifth judging module: if the half-wave true effective value of one phase voltage is unchanged and the half-wave true effective values of the other phase voltages are reduced, acquiring a previous-stage voltage sag type, and switching to a sixth judgment module; if the half-wave true effective values of the three-phase voltage are all reduced, the seventh judgment module is switched to;
a sixth judging module: if the voltage sag is caused by the single-phase earth fault, the voltage sag type is the voltage sag caused by the transmission of the single-phase earth fault through the transformer; if not, continuing to obtain the previous voltage sag type, and repeating the module judgment process until the voltage sag type is judged;
a seventh judging module: if the absolute value of the sum of the positive sequence component and the negative sequence component is greater than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by the transmission of the two-phase ground fault through the transformer; if the absolute value of the sum of the positive sequence component and the negative sequence component is smaller than the absolute value of the difference between the positive sequence component and the negative sequence component, acquiring a voltage sag type of the previous stage, and turning to an eighth judging module;
an eighth judging module: if the voltage sag is caused by single-phase earth fault or two-phase short circuit fault, the voltage sag type is the voltage sag caused by the transmission of the single-phase earth fault through the transformer; if the voltage sag is caused by the two-phase ground fault or the voltage sag is caused by the two-phase ground fault propagating through the transformer, the voltage sag type is the voltage sag caused by the two-phase ground fault propagating through the transformer; otherwise, continuing to obtain the voltage sag type of the previous stage, and repeating the judgment process of the module until the voltage sag type is judged.
A computer readable storage medium storing one or more programs, the one or more programs comprising instructions, which when executed by a computing device, cause the computing device to perform a voltage sag source identification method that takes into account transformer propagation characteristics.
A computing device comprising one or more processors, memory, and one or more programs stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for performing a voltage sag source identification method that accounts for transformer propagation characteristics.
As will be appreciated by one skilled in the art, 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 flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams 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.
The present invention is not limited to the above embodiments, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are included in the scope of the claims of the present invention which are filed as the application.
Claims (10)
1. A voltage sag source identification method considering transformer propagation characteristics is characterized in that: comprises that
Judging whether voltage sag occurs or not according to the monitored three-phase voltage;
responding to the voltage sag, and calculating a half-wave true effective value, a positive sequence component, a negative sequence component and a zero sequence component of the three-phase voltage according to the monitored three-phase voltage;
and identifying the voltage sag type according to the half-wave true effective value, the positive sequence component, the negative sequence component and the zero sequence component of the three-phase voltage and a preset judgment rule.
2. The method for identifying the source of the voltage sag considering the propagation characteristics of the transformer according to claim 1, wherein: according to the half-wave true effective value, the positive sequence component, the negative sequence component and the zero sequence component of the three-phase voltage and the preset judgment rule, the process of identifying the voltage sag type comprises the following steps,
step 1, if the absolute value of the difference value of the true effective values of the three-phase voltage half-waves is smaller than the minimum value of a preset interval, the voltage sag type is voltage sag caused by three-phase short-circuit faults; if the absolute value of the true effective value difference value of the three-phase voltage half-wave is within the preset interval, turning to the step 2, and if the absolute value of the true effective value difference value of the three-phase voltage half-wave is larger than the maximum value of the preset interval, turning to the step 3;
step 2, if the negative sequence component is 0, the voltage sag type is voltage sag caused by three-phase short-circuit fault; if the negative sequence component is not 0, turning to step 3;
step 3, if the zero sequence component is not 0, turning to step 4, and if the zero sequence component is 0, turning to step 5;
step 4, if the absolute value of the sum of the positive sequence component and the negative sequence component is greater than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by two-phase ground faults; if the absolute value of the sum of the positive sequence component and the negative sequence component is smaller than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by single-phase earth fault;
step 5, if the half-wave true effective value of one phase voltage is unchanged and the half-wave true effective values of the other phase voltages are reduced, acquiring a previous-stage voltage sag type, and turning to step 6; if the half-wave true effective values of the three-phase voltage are all reduced, turning to the step 7;
step 6, if the voltage sag is caused by the single-phase earth fault, the voltage sag type is the voltage sag caused by the transmission of the single-phase earth fault through a transformer; if not, continuing to obtain the previous voltage sag type, and repeating the step until the voltage sag type is judged;
step 7, if the absolute value of the sum of the positive sequence component and the negative sequence component is greater than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by the transmission of the two-phase ground fault through a transformer; if the absolute value of the sum of the positive sequence component and the negative sequence component is smaller than the absolute value of the difference between the positive sequence component and the negative sequence component, acquiring a previous-stage voltage sag type, and turning to the step 8;
step 8, if the voltage sag is caused by the single-phase earth fault, the voltage sag type is the voltage sag caused by the transmission of the single-phase earth fault through a transformer; if the voltage sag is caused by the two-phase ground fault or the voltage sag is caused by the two-phase ground fault propagating through the transformer, the voltage sag type is the voltage sag caused by the two-phase ground fault propagating through the transformer; otherwise, continuously acquiring the voltage sag type of the previous stage, and repeating the step until the voltage sag type is judged.
3. The method for identifying the source of the voltage sag considering the propagation characteristics of the transformer according to claim 1, wherein: in response to no voltage sag occurring, the three phase voltages continue to be monitored.
4. The method for identifying the source of the voltage sag considering the propagation characteristics of the transformer according to claim 1, wherein: and if the voltage of a certain phase meets the voltage sag condition, judging that the voltage sag occurs.
5. A voltage sag source identification system considering transformer propagation characteristics, characterized by: comprises that
A generation judgment module: judging whether voltage sag occurs or not according to the monitored three-phase voltage;
a calculation module: responding to the voltage sag, and calculating a half-wave true effective value, a positive sequence component, a negative sequence component and a zero sequence component of the three-phase voltage according to the monitored three-phase voltage;
a type identification module: and identifying the voltage sag type according to the half-wave true effective value, the positive sequence component, the negative sequence component and the zero sequence component of the three-phase voltage and a preset judgment rule.
6. The system of claim 5, wherein the system is configured to identify the source of the voltage sag by considering the propagation characteristics of the transformer: the type-identifying module includes a type-identifying module,
a first judgment module: if the absolute value of the difference value of the true effective values of the half-wave of the three-phase voltage is smaller than the minimum value of the preset interval, the voltage sag type is the voltage sag caused by the three-phase short-circuit fault; if the absolute value of the difference value of the true effective values of the half-waves of the three-phase voltage is within the preset interval, the third judgment module is switched to;
a second judging module: if the negative sequence component is 0, the voltage sag type is voltage sag caused by three-phase short-circuit fault; if the negative sequence component is not 0, switching to a third judgment module;
a third judging module: if the zero sequence component is not 0, the fourth judgment module is switched to, and if the zero sequence component is 0, the fifth judgment module is switched to;
a fourth judging module: if the absolute value of the sum of the positive sequence component and the negative sequence component is greater than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by two-phase ground faults; if the absolute value of the sum of the positive sequence component and the negative sequence component is smaller than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by single-phase earth fault;
a fifth judging module: if the half-wave true effective value of one phase voltage is unchanged and the half-wave true effective values of the other phase voltages are reduced, acquiring a previous-stage voltage sag type, and switching to a sixth judgment module; if the half-wave true effective values of the three-phase voltage are all reduced, the seventh judgment module is switched to;
a sixth judging module: if the voltage sag is caused by the single-phase earth fault, the voltage sag type is the voltage sag caused by the transmission of the single-phase earth fault through the transformer; if not, continuing to obtain the previous voltage sag type, and repeating the module judgment process until the voltage sag type is judged;
a seventh judging module: if the absolute value of the sum of the positive sequence component and the negative sequence component is greater than the absolute value of the difference between the positive sequence component and the negative sequence component, the voltage sag type is voltage sag caused by the transmission of the two-phase ground fault through the transformer; if the absolute value of the sum of the positive sequence component and the negative sequence component is smaller than the absolute value of the difference between the positive sequence component and the negative sequence component, acquiring a voltage sag type of the previous stage, and turning to an eighth judging module;
an eighth judging module: if the voltage sag is caused by the single-phase earth fault, the voltage sag type is the voltage sag caused by the transmission of the single-phase earth fault through the transformer; if the voltage sag is caused by the two-phase ground fault or the voltage sag is caused by the two-phase ground fault propagating through the transformer, the voltage sag type is the voltage sag caused by the two-phase ground fault propagating through the transformer; otherwise, continuing to obtain the voltage sag type of the previous stage, and repeating the judgment process of the module until the voltage sag type is judged.
7. The system of claim 5, wherein the system is configured to identify the source of the voltage sag by considering the propagation characteristics of the transformer: the three-phase voltage monitoring system is characterized by further comprising a monitoring module used for monitoring the three-phase voltage, the monitoring module sends the three-phase voltage to the generation judging module, the monitoring module receives feedback of the generation judging module, and if voltage sag does not occur in the feedback, the monitoring module continues to monitor the three-phase voltage.
8. The system of claim 5, wherein the system is configured to identify the source of the voltage sag by considering the propagation characteristics of the transformer: if a certain phase voltage meets the voltage sag condition, the generation judgment module judges that the voltage sag occurs.
9. A computer readable storage medium storing one or more programs, characterized in that: the one or more programs include instructions that, when executed by a computing device, cause the computing device to perform any of the methods of claims 1-4.
10. A computing device, characterized by: comprises the steps of (a) preparing a mixture of a plurality of raw materials,
one or more processors, memory, and one or more programs stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for performing any of the methods of claims 1-4.
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