CN106199152B - Voltage sag identification system and method - Google Patents
Voltage sag identification system and method Download PDFInfo
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- CN106199152B CN106199152B CN201610678019.0A CN201610678019A CN106199152B CN 106199152 B CN106199152 B CN 106199152B CN 201610678019 A CN201610678019 A CN 201610678019A CN 106199152 B CN106199152 B CN 106199152B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
- G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
- G01R19/16576—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing DC or AC voltage with one threshold
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/02—Measuring effective values, i.e. root-mean-square values
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Abstract
The invention provides a voltage sag identification system which comprises a voltage sag triggering and conducting module, a data recording module, a data processing module and a display module, wherein the voltage sag triggering and conducting module is respectively communicated with a voltage transformer and a current transformer, the data recording module is connected with the voltage sag triggering and conducting module, the data processing module is connected with the data recording module, and the display module is connected with the data processing module. The invention also provides an identification method corresponding to the voltage sag identification system. According to the voltage sag identification system and the identification method, the characteristics of the voltage effective value amplitude and the current effective value amplitude are subjected to collaborative analysis and judgment, and the amplitude deviation and the threshold value of the sag duration in the voltage sag process are revised according to actual specific conditions, so that judgment errors caused by only analyzing the voltage effective value amplitude can be reduced, meanwhile, the slope is introduced, the global process of the voltage sag can be better represented by introducing the slope, the error rate of analysis and judgment is effectively reduced, and the reliability of analysis and judgment results is improved.
Description
Technical Field
The invention relates to the technical field of power quality transient analysis, in particular to a voltage sag identification system and a voltage sag identification method.
Background
With the technology update of electric equipment, especially in the 80 s of the 20 th century, the voltage quality requirement of a power supply system is higher and higher, and the voltage sag is a common electric energy quality problem because of the large-scale application of sensitive electric equipment such as variable frequency speed regulating equipment, programmable logic controllers, various automatic production lines, computer systems and the like in industrial production. Voltage sag is generally caused by faults of a power grid and a power transformation facility or sudden large changes of loads, and can lead to reduction of enterprise productivity and product quality, increase of manufacturing cost and prevent normal production planning of enterprises. Meanwhile, customer complaints and economic disputes caused by voltage sag are increased for each power department, and the competitiveness of the electric power market environment is affected.
The identification of the voltage sag refers to identifying the generation reason of the voltage sag according to the detected data characteristics of the voltage sag, and is one of important evaluation indexes of the voltage sag. The accurate identification of the voltage sag is not only beneficial to evaluating regional power distribution systems and selecting reasonable treatment measures, but also can be used as an important basis for coordination disputes among power supply departments, users and equipment suppliers in the power market environment. Therefore, research on monitoring, analyzing, solving a series of problems of voltage sag disturbance is more important.
At present, a method for identifying voltage sag only through a voltage effective value is provided in the research of a voltage sag identification method, and the method extracts corresponding characteristic quantities according to different conditions of voltage sag caused by different voltage sags, such as the step of generating voltage jump at the end of the sag, the analysis and comparison of voltage change trend in the voltage sag process, whether three-phase voltage is balanced, whether voltage sag occurs or not, and the like, so as to realize the identification of the voltage sag caused by line faults, transformer switching and high-capacity induction motor starting. However, the method has the following defects that if only the amplitude characteristic of the effective value of the voltage is analyzed and judged, the amplitude characteristic of the effective value of the current is not cooperatively analyzed and judged when the voltage sag occurs, and the misjudgment rate of the analysis and judgment in the original method is increased; the voltage jump is used as a characteristic quantity to identify the voltage sag, and the global process of the voltage sag cannot be represented, so that the method has limitation in the process of identifying the voltage sag, and the misjudgment rate of analysis and judgment is increased; the method is inconsistent with actual engineering experience in the threshold setting of three-phase amplitude deviation and voltage sag duration.
Disclosure of Invention
The invention aims to provide a voltage sag identification system and a voltage sag identification method, which are used for solving the problem of high misjudgment rate of the existing voltage sag identification method in the background technology.
In order to solve the technical problems, the invention provides the following technical scheme:
a voltage sag identification system, the system comprising:
a voltage sag triggering and conducting module respectively communicated with the voltage transformer and the current transformer,
a data recording module connected with the voltage sag trigger conduction module,
a data processing module connected with the data recording module,
the display module is connected with the data processing module;
the data recording module comprises a data converter and a data recorder, wherein the data converter is connected with the voltage sag trigger conduction module, and the data recorder is respectively connected with the data converter and the data processing module;
the data processing module comprises a data processing device connected with the data recorder, the data processing device is respectively connected with a slope processing module, a duration processing module, a voltage effective value amplitude deviation processing module and a current effective value amplitude deviation processing module, and the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module are respectively connected with a result accumulation module;
the result accumulation module is connected with the display module.
Preferably, the data converter is an a/D converter, and the data processing device is a single-chip microcomputer.
Preferably, the slope processing module comprises a Δk comparator and an A/D converter A connected with the singlechip, wherein the Δk comparator is respectively connected with the A/D converter A and a Δk threshold memory.
Preferably, the duration processing module comprises a Δt comparator and an A/D converter B connected with the singlechip, wherein the Δt comparator is respectively connected with the A/D converter B and a Δt threshold memory.
Preferably, the voltage effective value amplitude deviation processing module comprises a Δu comparator and an a/D converter C connected with the single chip microcomputer, wherein the Δu comparator is respectively connected with the a/D converter C, a Δu threshold memory and a trigger switch.
Preferably, the current effective value amplitude deviation processing module comprises a delta I comparator and an A/D converter D connected with the singlechip, wherein the A/D converter D and the delta I comparator are connected through a controllable switch, the controllable switch is connected with the delta U comparator, and the delta I comparator is also connected with a delta I threshold memory and a NOT gate.
A voltage sag identification method, the identification method comprising:
the voltage slope difference delta k, the duration delta t, the voltage effective value amplitude deviation characteristic delta U and the current effective value amplitude deviation characteristic delta I are preset respectively;
measuring a voltage effective value and a current effective value;
judging whether the effective voltage value is lower than a normal value;
if the effective voltage value is not lower than the normal value, continuing to measure the effective voltage value and the effective current value;
if the effective voltage value is lower than the normal value, the voltage sag triggers the conduction module to conduct;
transmitting the voltage effective value and the current effective value to a data converter to be converted into digital quantity;
the digital quantity is sent to a data logger, which records U, I the corresponding time and forms (U i ，I i ，t i ) A data set;
the (U) i ，I i ，t i ) The data set is sent to a data processing device, and corresponding voltage slope difference delta k, duration delta t, voltage effective value amplitude deviation characteristic delta U and current effective value amplitude deviation characteristic delta I are calculated;
the data processing device respectively sends the voltage slope difference delta k, the duration delta t, the voltage effective value amplitude deviation characteristic delta U and the current effective value amplitude deviation characteristic delta I to a slope processing module, a duration processing module, a voltage effective value amplitude deviation processing module and a current effective value amplitude deviation processing module;
the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module respectively compare the calculated value and the threshold value and respectively obtain comparison results;
the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module respectively send the comparison result to a result accumulation module;
the result accumulation module accumulates the comparison results to obtain accumulated results;
judging whether the accumulated result is more than 2;
if the accumulated result is greater than 2, the voltage sag is the start of the induction motor or the switching of the transformer;
and if the accumulated result is less than or equal to 2, the voltage sag is short circuit.
Preferably, the preset thresholds for the voltage slope difference Δk, the duration Δt, the voltage effective value amplitude deviation characteristic Δu, and the current effective value amplitude deviation characteristic Δi respectively include:
setting the threshold value of the voltage slope difference delta k to be 0.05; the threshold value of the duration Δt is 0.1; the threshold value of the voltage effective value amplitude deviation characteristic delta U is 0.8; the threshold value of the current effective value amplitude deviation characteristic Δi is 4.
Preferably, the calculation formulas for calculating the corresponding voltage slope difference Δk, duration Δt, voltage effective value amplitude deviation characteristic Δu and current effective value amplitude deviation characteristic Δi are as follows:
Preferably, the comparing the calculated value and the threshold value respectively, and obtaining the comparison result respectively includes:
comparing the calculated value of the voltage slope difference delta k with the magnitude of the threshold value, outputting a comparison result as 1 if the calculated value of delta k is larger than the magnitude of the threshold value, otherwise outputting a comparison result as 0;
comparing the calculated value of the duration delta t with the magnitude of the threshold, outputting a comparison result as 1 if the calculated value of delta t is larger than the magnitude of the threshold, otherwise outputting a comparison result as 0;
comparing the amplitude deviation characteristic delta U of the effective value of the voltage with the magnitude of the threshold, outputting a comparison result as 0 if the calculated value of delta U is smaller than the magnitude of the threshold, otherwise, not outputting the result;
comparing the amplitude deviation characteristic delta I of the effective value of the current with the magnitude of the threshold, outputting a comparison result as 0 if the calculated value of delta I is larger than the magnitude of the threshold, otherwise outputting a comparison result as 1.
A voltage sag identification system, the system comprising: the device comprises a voltage sag trigger conduction module, a data recording module, a data processing module and a display module, wherein the voltage sag trigger conduction module is respectively communicated with a voltage transformer and a current transformer, the data recording module is connected with the voltage sag trigger conduction module, the data processing module is connected with the data recording module, and the display module is connected with the data processing module; the data recording module comprises a data converter and a data recorder, wherein the data converter is connected with the voltage sag trigger conduction module, and the data recorder is respectively connected with the data converter and the data processing module; the data processing module comprises a data processing device connected with the data recorder, the data processing device is respectively connected with a slope processing module, a duration processing module, a voltage effective value amplitude deviation processing module and a current effective value amplitude deviation processing module, and the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module are respectively connected with a result accumulation module; the result accumulation module is connected with the display module. The invention also provides a voltage sag identification method corresponding to the voltage sag identification system. According to the voltage sag identification system and the identification method, the characteristics of the voltage effective value amplitude and the current effective value amplitude are subjected to collaborative analysis and judgment, and the amplitude deviation and the threshold value of the sag duration in the voltage sag process are revised according to actual specific conditions, so that judgment errors caused by only analyzing the voltage effective value amplitude can be reduced, meanwhile, the slope is introduced, the global process of the voltage sag can be better represented by introducing the slope, the error rate of analysis and judgment is effectively reduced, and the reliability of analysis and judgment results is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it will be obvious to those skilled in the art that other drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a schematic diagram of a voltage sag identification system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a specific device of a voltage sag identification system according to an embodiment of the present invention;
fig. 3 is a flowchart of a voltage sag identification method according to an embodiment of the invention.
Detailed Description
The voltage sag identification system and the voltage sag identification method provided by the embodiment of the invention solve the problem of high misjudgment rate of the existing voltage sag identification method.
In order to better understand the technical solution in the embodiments of the present invention and make the above objects, features and advantages of the embodiments of the present invention more comprehensible, the technical solution in the embodiments of the present invention is described in further detail below with reference to the accompanying drawings.
Referring to fig. 1, fig. 1 is a schematic diagram illustrating a voltage sag identification system according to an embodiment of the invention.
As can be seen from fig. 1, the voltage sag identification system provided in the embodiment of the present invention includes: the voltage sag trigger conduction module is respectively communicated with the voltage transformer and the current transformer, the data recording module is connected with the voltage sag trigger conduction module, the data processing module is connected with the data recording module, and the display module is connected with the data processing module. The data recording module comprises a data converter and a data recorder, wherein the data converter is connected with the voltage sag trigger conduction module, and the data recorder is respectively connected with the data converter and the data processing module; the data processing module comprises a data processing device connected with the data recorder, the data processing device is respectively connected with a slope processing module, a duration processing module, a voltage effective value amplitude deviation processing module and a current effective value amplitude deviation processing module, and the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module are respectively connected with a result accumulation module; the result accumulation module is connected with the display module.
Specifically, the voltage transformer and the current transformer measure a voltage effective value U and a current effective value I, respectively.
When the effective voltage value U is lower than normal, a voltage dip occurs, which is typically 220V. When the voltage sag occurs, the voltage sag triggers the conduction module to conduct, and when the voltage sag does not occur or recovers, the voltage sag triggers the conduction module to cut off.
The data recording module comprises a data converterAnd a data recorder, wherein the data converter is used for converting the measured voltage effective value U and the current effective value I into digital quantity, the data recorder records the voltage effective value U and the current effective value I at regular intervals, the voltage effective value U, the current effective value I and the time forming (U i ，I i ，t i ) A data set.
The data processing module comprises a data processing device, a slope processing module, a duration processing module, a voltage effective value amplitude deviation processing module and a current effective value amplitude deviation processing module; wherein the data processing means are arranged for recording (U i ，I i ，t i ) The data set calculates a voltage slope difference delta k, a duration delta t, a voltage effective value amplitude deviation characteristic delta U and a current effective value amplitude deviation characteristic delta I; the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module respectively compare the calculated value and the threshold value, and further respectively obtain comparison results.
The result accumulation module is used for receiving the comparison result sent by the data processing module and accumulating the comparison result to obtain an accumulation result, and if the accumulation result is more than 2, the voltage sag is caused by starting the induction motor or switching the transformer; if the accumulated result is less than or equal to 2, the voltage sag is caused by a short circuit.
The display module is used for displaying the reason result of causing the voltage sag.
According to the voltage sag identification system, through collaborative analysis and judgment of the characteristics of the voltage effective value amplitude and the current effective value amplitude, judgment errors caused by only analyzing the voltage effective value amplitude can be reduced, meanwhile, the slope is introduced, the global process of the voltage sag can be better represented by introducing the slope, so that the error rate of analysis and judgment is effectively reduced, and the reliability of analysis and judgment results is improved.
The embodiment of the invention also provides a structural schematic diagram of a specific device of the voltage sag identification system, and particularly please refer to fig. 2. In the specific device of the voltage sag identification system provided by the embodiment of the invention, the data converter is preferably an A/D converter, and the data processing device is preferably a singlechip; the slope processing module comprises a delta k comparator and an A/D converter A which are connected with the singlechip, wherein the delta k comparator is respectively connected with the A/D converter A and a delta k threshold memory; the duration processing module comprises an A/D converter B connected with the singlechip, and the A/D converter B are respectively connected with a delta t threshold memory; the voltage effective value amplitude deviation processing module comprises a delta U comparator and an A/D converter C connected with the singlechip, wherein the delta U comparator is respectively connected with the A/D converter C, a delta U threshold memory and trigger conduction; the current effective value amplitude deviation processing module comprises a delta I comparator and an A/D converter D connected with the singlechip, wherein the A/D converter D and the delta I comparator are connected through a controllable switch, the controllable switch is connected with the delta U comparator, and the delta I comparator is also connected with a delta I threshold memory and a NOT gate.
Among them, the a/D converter A, A/D converter B, A/D converter C and a/D converter D function the same as the a/D converter as the data converter, except that the converted data are different; the Δk threshold memory, the Δt threshold memory, the Δu threshold memory and the Δi threshold memory store preset thresholds respectively; the Δk comparator, Δt comparator, Δu comparator, and Δi comparator compare the input calculated value with a threshold value, respectively, and output a comparison result. When the delta U comparator compares the amplitude deviation of the effective value of the voltage, triggering the conducting component to conduct when the calculated value of the delta U is smaller than a threshold value, and simultaneously turning off the controllable switch and outputting a comparison result of 0; when the calculated value of DeltaU is larger than or equal to the threshold value, the switching-on component is triggered to be switched off, and meanwhile, the controllable switch is switched on, and the comparison result is not output. When the delta I comparator compares the amplitude deviation of the current effective value, under the action of the NOT gate, when the delta I is larger than the threshold value, the comparison result is output as 0, and when the delta I is smaller than or equal to the threshold value, the comparison result is output as 1.
The specific working process of the specific device of the voltage sag identification system provided by the embodiment of the invention is as follows: voltage transformerThe current transformer respectively measures the voltage effective value and the current effective value, judges whether the voltage effective value is lower than a normal value, and continuously measures the voltage effective value and the current effective value until the voltage effective value is lower than the normal value when the voltage effective value is not lower than the normal value; when the effective voltage value is lower than the normal value, the voltage sag triggers the conduction module to conduct, so that the voltage transformer and the current transformer send the effective voltage value and the effective current value to the A/D converter to be converted into digital quantity, the converted digital quantity is sent to a data recorder, the data recorder records U, I at corresponding moment, and a U (U) is formed i ，I i ，t i ) A data set; will (U) i ，I i ，t i ) The data set is sent to a singlechip, and the singlechip calculates corresponding voltage slope difference delta k, duration delta t, voltage effective value amplitude deviation characteristic delta U and current effective value amplitude deviation characteristic delta I; the singlechip respectively sends the voltage slope difference delta k, the duration delta t, the voltage effective value amplitude deviation characteristic delta U and the current effective value amplitude deviation characteristic delta I to a slope processing module, a duration processing module, a voltage effective value amplitude deviation processing module and a current effective value amplitude deviation processing module; the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module respectively compare the calculated value and the threshold value, and respectively obtain comparison results; the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module respectively send comparison results to the result accumulation module, and the result accumulation module accumulates the comparison results to obtain accumulation results; when the accumulated result is more than 2, the voltage sag is caused by starting the induction motor or switching the transformer; when the accumulated result is less than or equal to 2, the voltage sag is caused by short circuit, and the display module displays the final identification result.
Referring to fig. 3, fig. 3 is a flow chart illustrating a voltage dip identification method according to an embodiment of the invention.
As can be seen from fig. 3, the voltage sag identification method provided by the embodiment of the present invention includes:
s01: the voltage slope difference delta k, the duration delta t, the voltage effective value amplitude deviation characteristic delta U and the current effective value amplitude deviation characteristic delta I are preset respectively;
s02: measuring a voltage effective value and a current effective value;
s03: judging whether the effective voltage value is lower than a normal value;
s04: if the effective voltage value is not lower than the normal value, continuing to measure the effective voltage value and the effective current value;
s05: if the effective voltage value is lower than the normal value, the voltage sag triggers the conduction module to conduct;
s06: transmitting the voltage effective value and the current effective value to a data converter to be converted into digital quantity;
s07: the digital quantity is sent to a data logger, which records U, I the corresponding time and forms (U i ，I i ，t i ) A data set;
s08: the (U) i ，I i ，t i ) The data set is sent to a data processing device, and corresponding voltage slope difference delta k, duration delta t, voltage effective value amplitude deviation characteristic delta U and current effective value amplitude deviation characteristic delta I are calculated;
s09: the data processing device respectively sends the voltage slope difference delta k, the duration delta t, the voltage effective value amplitude deviation characteristic delta U and the current effective value amplitude deviation characteristic delta I to a slope processing module, a duration processing module, a voltage effective value amplitude deviation processing module and a current effective value amplitude deviation processing module;
s10: the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module respectively compare the calculated value and the threshold value and respectively obtain comparison results;
s11: the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module respectively send the comparison result to a result accumulation module;
s12: the result accumulation module accumulates the comparison results to obtain accumulated results;
s13: judging whether the accumulated result is more than 2;
s14: if the accumulated result is greater than 2, the voltage sag is the start of the induction motor or the switching of the transformer;
s15: and if the accumulated result is less than or equal to 2, the voltage sag is short circuit.
The concrete description is as follows:
s01: the method comprises the steps of presetting voltage slope difference delta k, duration delta t, voltage effective value amplitude deviation characteristic delta U and current effective value amplitude deviation characteristic delta I threshold values respectively, and storing the set threshold values in a delta k threshold value memory, a delta t threshold value memory, a delta U threshold value memory and a delta I threshold value memory respectively to facilitate the calling of subsequent steps, wherein the voltage slope difference delta k threshold value is set to be 0.05; the threshold value of the duration Δt is 0.1; the threshold value of the voltage effective value amplitude deviation characteristic delta U is 0.8; the threshold value of the amplitude deviation characteristic delta I of the effective value of the current is 4;
s02: the voltage transformer and the current transformer respectively measure a voltage effective value and a current effective value;
s03: judging whether the effective voltage value is lower than a normal value, wherein the normal value is generally 220v;
s04: if the voltage effective value is not lower than the normal value, the voltage transformer and the current transformer continuously measure the voltage effective value and the current effective value until the voltage effective value is lower than the normal value;
s05: if the effective voltage value is lower than the normal value, the voltage sag triggers the conduction module to conduct;
s06: after the voltage sag triggering conduction module is conducted, the voltage effective value and the current effective value are sent to the data converter, and the voltage effective value and the current effective value are converted into digital values;
s07: the data converter sends the digital quantity to the data recorder, and the data recorder records the corresponding timeU, I of (A) and forming (U) i ，I i ，t i ) A data set;
s08: will (U) i ，I i ，t i ) The data set is sent to a data processing device, and corresponding voltage slope difference delta k, duration delta t, voltage effective value amplitude deviation characteristic delta U and current effective value amplitude deviation characteristic delta I are calculated;
specifically, the data set at the beginning of the voltage sag is (U 0 ,I 0 ,T 0 ) Voltage minimum U n ＝min(U j ) The corresponding data set at this time is (U) n ,I n ,T n ) Maximum value of current effective value I m ＝max(I j ) The corresponding data set at this time is (U) m ,I m ,T m ) The data set at the end of the voltage sag is (U) s ,I s ,T s ) The calculation formulas of the voltage slope difference delta k, the duration delta t, the voltage effective value amplitude deviation characteristic delta U and the current effective value amplitude deviation characteristic delta I are as follows
△t＝t s -t 0 ；
Wherein k is 1 、k 2 The voltage slopes at the beginning and end of the voltage sag are respectively; t is t 0 、t s The time when the voltage sag will start and the time when the voltage sag ends are respectively; u (U) 0 、U s Voltage values at which voltage sag will start and sag ends; i 0 、I m The current value and the maximum current value when the voltage pause starts are respectively; k (k) 1 、k 2 Is calculated as
S09: the data processing device respectively sends the voltage slope difference delta k, the duration delta t, the voltage effective value amplitude deviation characteristic delta U and the current effective value amplitude deviation characteristic delta I to the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module;
s10: the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module respectively compare the calculated value and the threshold value, and respectively obtain comparison results;
the method comprises the following steps: comparing the calculated value of the voltage slope difference delta k with the magnitude of the threshold value, outputting a comparison result as 1 if the calculated value of delta k is larger than the magnitude of the threshold value, otherwise outputting a comparison result as 0;
comparing the calculated value of the duration delta t with the magnitude of the threshold, outputting a comparison result as 1 if the calculated value of delta t is larger than the magnitude of the threshold, otherwise outputting a comparison result as 0;
comparing the amplitude deviation characteristic delta U of the effective value of the voltage with the magnitude of the threshold, outputting a comparison result as 0 if the calculated value of delta U is smaller than the magnitude of the threshold, otherwise, not outputting the result;
comparing the amplitude deviation characteristic delta I of the effective value of the current with the magnitude of the threshold, outputting a comparison result as 0 if the calculated value of delta I is larger than the magnitude of the threshold, otherwise outputting a comparison result as 1.
S11: the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module respectively send the comparison result to the result accumulation module;
s12: the result accumulation module accumulates the received comparison results to obtain accumulated results;
s13: judging whether the accumulated result is more than 2;
s14: if the accumulated result is greater than 2, the voltage sag is caused by starting the induction motor or switching the transformer;
s15: if the accumulated result is less than or equal to 2, the voltage sag is caused by a short circuit.
According to the voltage sag identification method, the characteristics of the voltage effective value amplitude and the current effective value amplitude are subjected to collaborative analysis and judgment, and the amplitude deviation and the threshold value of the sag duration in the voltage sag process are revised according to actual specific conditions, so that the judgment errors caused by only analyzing the voltage effective value amplitude can be reduced, meanwhile, the slope is introduced, the global process of the voltage sag can be better represented by introducing the slope, the error rate of analysis and judgment is effectively reduced, and the reliability of the analysis and judgment result is improved.
The embodiments of the present invention described above do not limit the scope of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of the present invention.
Claims (4)
1. The voltage sag identification method is characterized by being applied to a voltage sag identification system, and the voltage sag identification system comprises the following steps:
a voltage sag triggering and conducting module respectively communicated with the voltage transformer and the current transformer,
a data recording module connected with the voltage sag trigger conduction module,
a data processing module connected with the data recording module,
the display module is connected with the data processing module;
the data recording module comprises a data converter and a data recorder, wherein the data converter is connected with the voltage sag trigger conduction module, and the data recorder is respectively connected with the data converter and the data processing module;
the data processing module comprises a data processing device, a slope processing module, a duration processing module, a voltage effective value amplitude deviation processing module and a current effective value amplitude deviation processing module which are connected with the data recorder, wherein the data processing device is respectively connected with the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module, and the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module are respectively connected with the result accumulation module;
wherein the data processing means are arranged for recording (U i ，I i ，t i ) The data set calculates a voltage slope difference delta k, a duration delta t, a voltage effective value amplitude deviation characteristic delta U and a current effective value amplitude deviation characteristic delta I; the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module respectively compare the calculated value and the threshold value, and further respectively obtain comparison results;
the result accumulation module is connected with the display module;
the voltage sag identification method comprises the following steps:
the voltage slope difference delta k, the duration delta t, the voltage effective value amplitude deviation characteristic delta U and the current effective value amplitude deviation characteristic delta I are preset respectively;
measuring a voltage effective value and a current effective value;
judging whether the effective voltage value is lower than a normal value;
if the effective voltage value is not lower than the normal value, continuing to measure the effective voltage value and the effective current value;
if the effective voltage value is lower than the normal value, the voltage sag triggers the conduction module to conduct;
transmitting the voltage effective value and the current effective value to a data converter to be converted into digital quantity;
the digital quantity is sent to a data logger, which records U, I the corresponding time and forms (U i ，I i ，t i ) A data set;
the (U) i ，I i ，t i ) The data set is sent to a data processing device, and corresponding voltage slope difference delta k, duration delta t, voltage effective value amplitude deviation characteristic delta U and current effective value amplitude deviation characteristic delta I are calculated;
the data processing device respectively sends the voltage slope difference delta k, the duration delta t, the voltage effective value amplitude deviation characteristic delta U and the current effective value amplitude deviation characteristic delta I to a slope processing module, a duration processing module, a voltage effective value amplitude deviation processing module and a current effective value amplitude deviation processing module;
the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module respectively compare the calculated value and the threshold value and respectively obtain comparison results;
the slope processing module, the duration processing module, the voltage effective value amplitude deviation processing module and the current effective value amplitude deviation processing module respectively send the comparison result to a result accumulation module;
the result accumulation module accumulates the comparison results to obtain accumulated results;
judging whether the accumulated result is more than 2;
if the accumulated result is greater than 2, the voltage sag is the start of the induction motor or the switching of the transformer;
and if the accumulated result is less than or equal to 2, the voltage sag is short circuit.
2. The voltage sag identification method according to claim 1, wherein the pre-setting of the thresholds of the voltage slope difference Δk, the duration Δt, the voltage effective value amplitude deviation characteristic Δu, and the current effective value amplitude deviation characteristic Δi, respectively, includes:
setting the threshold value of the voltage slope difference delta k to be 0.05; the threshold value of the duration Δt is 0.1; the threshold value of the voltage effective value amplitude deviation characteristic delta U is 0.8; the threshold value of the current effective value amplitude deviation characteristic Δi is 4.
3. The voltage sag identification method according to claim 1, wherein the calculation formulas for calculating the corresponding voltage slope difference Δk, duration Δt, voltage effective value amplitude deviation characteristic Δu, and current effective value amplitude deviation characteristic Δi are as follows:
4. The voltage sag identification method according to claim 1, wherein comparing the calculated values and the threshold values, respectively, and obtaining comparison results, respectively, includes:
comparing the calculated value of the voltage slope difference delta k with the magnitude of the threshold value, outputting a comparison result as 1 if the calculated value of delta k is larger than the magnitude of the threshold value, otherwise outputting a comparison result as 0;
comparing the calculated value of the duration delta t with the magnitude of the threshold, outputting a comparison result as 1 if the calculated value of delta t is larger than the magnitude of the threshold, otherwise outputting a comparison result as 0;
comparing the amplitude deviation characteristic delta U of the effective value of the voltage with the magnitude of the threshold, outputting a comparison result as 0 if the calculated value of delta U is smaller than the magnitude of the threshold, otherwise, not outputting the result;
comparing the amplitude deviation characteristic delta I of the effective value of the current with the magnitude of the threshold, outputting a comparison result as 0 if the calculated value of delta I is larger than the magnitude of the threshold, otherwise outputting a comparison result as 1.
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| CN112114217B (en) * | 2020-09-22 | 2022-07-12 | 贵州大学 | Low-voltage transformer area identification method for distribution network voltage monitoring and management system |
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