CN111751647B - Differential flow anomaly detection method - Google Patents
Differential flow anomaly detection method Download PDFInfo
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- CN111751647B CN111751647B CN202010583819.0A CN202010583819A CN111751647B CN 111751647 B CN111751647 B CN 111751647B CN 202010583819 A CN202010583819 A CN 202010583819A CN 111751647 B CN111751647 B CN 111751647B
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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
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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
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
Abstract
The invention provides a differential flow abnormality detection method, which comprises the following steps of S1, detecting whether a single-phase or inter-phase short-circuit grounding fault exists in a power grid, if so, reading protection event data of the whole power grid when the power grid fault occurs, and obtaining a differential flow abnormality detection interval list; step S2, all the waveforms of the interval protection device and all the waveforms of the fault recorder are called in the differential stream abnormal detection interval list, and amplitude correction and phase correction are carried out; s3, selecting a protection interval from the fetched data, and intercepting a protection device current waveform and a fault recorder current waveform of the interval in a waveform comparison section; s4, waveform comparison, waveform amplitude, waveform distortion and harmonic characteristic calculation are carried out, and waveform characteristic vectors of the interval are obtained; and S5, calculating the characteristic vector of the waveform detection result of the interval, and calculating the waveform detection result of the interval according to a detection result decision table. The invention has high detection accuracy, strong engineering practicability and clear positioning of the reasons of the differential flow abnormality.
Description
Technical Field
The invention relates to the technical field of relay protection abnormality detection, in particular to a differential flow abnormality detection method.
Background
Relay protection is a first defense line of a power grid, can rapidly and selectively cut off primary equipment with faults, prevents the expansion of the fault range, and is crucial to guaranteeing safe and stable operation of the power grid. With the technical progress, the relay protection device is gradually perfected, and the operation reliability is extremely high. However, the operation and maintenance of the secondary circuit related to relay protection still keeps the traditional artificial operation and maintenance mode, and protection misoperation events caused by the abnormality of the secondary circuit are frequent due to the difference of personal skill level and working attitude. The differential current abnormality caused by the current loop abnormality or the protection device setting error becomes a main factor of protection malfunction caused by the secondary loop abnormality.
For a long time, an effective abnormal state detection method is not available for a current loop in operation, and the hidden trouble of setting errors of a current loop or a protection device left in the process of definite inspection or acceptance is difficult to find. With the deep advancement of digital power grid transformation, the information protection substation (or intelligent recorder) and the fault recorder can realize full coverage in fourteen-five planning periods, and the protection device record wave and the fault recorder record wave in the transformer substation can be sent to the information protection main station for centralized processing, thereby laying a solid foundation for automatic detection of differential flow abnormality. Some scholars have proposed to implement current loop anomaly detection by performing homology comparison on a fault recorder waveform and a protection device waveform, and the main disadvantages are as follows:
the existing method does not carry out comprehensive correction on the waveform, the situation that the comparison result is not in line with the actual situation frequently occurs, and the engineering practicability is poor. For example, if the fault recorder and the protection device current loop are often connected in reverse, the old protection device N-line polarity is often connected in reverse, the device time is often deviated, etc., the normal operation current loop is also detected as an abnormal loop if the waveform correction is not performed.
The existing method only gives out the result of whether the current loop is abnormal or not, does not give out the specific reason for the abnormal difference flow, needs manual further analysis and judgment, has small supporting effect on the on-site trip event analysis and risk early warning, and has low intelligent degree.
Disclosure of Invention
The technical problem solved by the embodiment of the invention is that the existing detection method has low detection accuracy and can not accurately locate the cause of the abnormality.
In one aspect of the present invention, there is provided a differential flow anomaly detection method including the steps of:
step S1, detecting whether single-phase or inter-phase short-circuit grounding faults exist in a power grid, if so, reading protection event data of the whole power grid when the power grid faults occur, screening interval data of all 110kV and above with starting protection events, and obtaining a differential flow abnormal detection interval list;
step S2, all the waveforms of the interval protection device and all the waveforms of the fault recorder are called in the differential flow abnormal detection interval list, and amplitude correction and phase correction are carried out on all the current waveforms;
s3, selecting a protection interval from the fetched data, and intercepting a protection device current waveform and a fault recorder current waveform of the interval in a waveform comparison section;
s4, performing waveform comparison, waveform amplitude, waveform distortion and harmonic characteristic calculation on the intercepted current waveform of the protection device and the current waveform of the fault recorder to obtain waveform characteristic vectors of the interval;
and S5, calculating the characteristic vector of the waveform detection result of the interval, calculating the waveform detection result of the interval according to the detection result decision table, and repeating until the waveform detection results of all the guard intervals are calculated.
In step S2, the method for correcting the amplitudes of all current waveforms specifically includes that the amplitudes of the current waveforms of the differential set are kept unchanged, the amplitudes of the three-phase currents and the N-line currents of the fault record set are corrected, the three-phase currents and the N-line currents of the fault record set are multiplied by a transformation ratio correction coefficient m, and then the non-periodic components of the three-phase currents and the N-line currents of the fault record set are filtered.
Further, the transformation ratio correction coefficient m is calculated according to the following formula:
wherein CT 1 CT is the CT transformation ratio of the current loop of the differential group 2 The CT transformation ratio of the current loop of the fault record wave group.
Further, in step S2, the method for performing phase correction on all current waveforms specifically includes:
the phase angle of the differential group phase current is kept unchanged, the phase of the three-phase current of the fault wave recording group is corrected, and the three-phase current of the fault wave recording group is multiplied by a phase correction coefficient n respectively 1 ；
The phase correction coefficient n 1 Calculated according to the following formula:
wherein θ 1 For correcting angle, when the polarity of the current loop of the fault record wave group is close to the bus, theta 1 Is 0; when (when)When the polarity of the fault record wave group current loop is close to the circuit, theta 1 180.
Further, in step S2, the method for performing phase correction on all current waveforms specifically includes:
correcting the polarity of the N-line currents of the differential current set, and multiplying the N-line currents of the differential current set by a phase correction coefficient N 2 ；
The phase correction coefficient n 2 Calculated according to the following formula:
wherein θ 2 For angle correction, θ is calculated when the N-wire is connected to the non-polar end of the N-wire sampling small CT of the protection device 2 Is 0; when N lines are connected with the polarity end of the N line sampling small CT of the protection device, theta 2 180.
Further, in step S2, the method for performing phase correction on all current waveforms specifically includes:
correcting the polarity of N line currents of the fault wave recording current group, and multiplying the N line currents of the fault wave recording current group by a phase correction coefficient N 3 ；
The phase correction coefficient n 3 The calculation is performed according to the following formula:
wherein θ 3 For correcting angle, when N line is connected to the non-polar end of the N line sampling small CT of the fault wave recording device and the polarity of the fault wave recording group current loop is close to the bus, N line is connected to the polar end of the N line sampling small CT of the fault wave recording device and the polarity of the fault wave recording group current loop is close to the line, θ 3 Is 0; when the N line is connected to the polarity end of the N line sampling small CT of the fault wave recording device and the polarity of the fault wave recording group current loop is close to the bus, the N line is connected to the non-polarity end of the N line sampling small CT of the fault wave recording device and the polarity of the fault wave recording group current loop is close to the line, the theta 3 180.
Further, in step S3, the intercepting the protection device current waveform and the fault recorder current waveform of the interval in the waveform comparison section specifically includes setting starting points and ending points of the protection device current waveform and the fault recorder current waveform according to the following manner:
the starting point of the waveform comparison section of the protection device is set as the starting time of the waveform comparison section of the protection device, whether the fault recorder and the protection device are consistent in time or not is judged, if the fault recorder and the protection device are consistent in time, the starting point of the waveform of the fault record group and the protection device are at the same time, and if the fault recorder and the protection device are inconsistent in time, the starting point is the time when the amplitude of the mutation quantity of the waveform of the fault record group reaches the amplitude of the mutation quantity of the protection device at the starting time for the first time;
the end points of the waveform comparison section of the fault recorder and the protection device are floating end points, and if the fault current disappears within 100ms after the start point, the moment of the disappearance of the fault current is taken as the end point; if the fault current does not disappear within 100ms after the start point, the end point is set to 100ms after the start point.
Further, in step S4, the method for performing waveform comparison, waveform amplitude, waveform distortion and harmonic feature calculation to obtain the waveform feature vector of the interval specifically includes:
when the current loop is normal, the currents of the phase A, the phase B, the phase C and the line N are the same, the virtual differential current is the same as the differential current of the protection device, and the protection device has no current distortion and harmonic wave;
when the protection device is set in error, the currents of the phase A, the phase B, the phase C and the line N are the same, and the virtual differential flow is different from the differential flow of the protection device;
when two points of the current loop are grounded, at least two current channels in A phase, B phase, C phase and N line are different, the differential current amplitude of the protection device is larger than a set value, the N line current amplitude of the protection device is larger than the set value, and the protection device has no current distortion and harmonic wave
When the neutral line resistance is increased, at least two current channels in the phase A, the phase B, the phase C and the line N are different, the differential current amplitude of the protection device is larger than a set value, the current amplitude of the line N of the protection device is larger than the set value, and the protection device has current distortion and harmonic waves;
when the neutral line is broken, at least three current channels in the phase A, the phase B, the phase C and the phase N are different, the differential current amplitude of the protection device is larger than a set value, and the current amplitude of the N line of the protection device is smaller than the set value;
when CT is saturated, the currents of the phase A, the phase B, the phase C and the line N are the same, the differential current amplitude of the protection device is larger than a set value, the current amplitude of the line N of the protection device is larger than the set value, and the protection device has current distortion and harmonic waves.
Further, in step S5, the waveform detection result feature vector for calculating the interval is specifically calculated according to the following formula:
X＝[x 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 ] T
Y＝[y 1 y 2 y 3 y 4 y 5 ] T
Y＝PX
wherein X is a waveform characteristic vector, P is a waveform characteristic matrix, Y is a waveform detection result vector; x is x 1 When the phase A current of the fault recorder is the same as the phase A current of the protection device, the value 1 is taken, and when the phase A current is different, the value 0 is taken; x is x 2 When the phase B current of the fault recorder is the same as the phase B current of the protection device, the value is 1, and when the phase B current is different, the value is 0; x is x 3 When the C-phase current of the fault recorder is the same as the C-phase current of the protection device, the value is 1, and when the C-phase current of the fault recorder is different from the C-phase current of the protection device, the value is 0; x is x 4 When the waveform of the N line current of the fault recorder is the same as that of the N line current of the protection device, the value 1 is taken, and when the waveform of the N line current of the fault recorder is different from that of the N line current of the protection device, the value 0 is taken; x is x 5 When the comparison result of the virtual differential stream and the differential stream of the protection device is the same, the value 1 is taken; if not, the value is 0; x is x 6 When the differential flow of the protection device is larger than 60A, the value is 1; otherwise, taking a value of 0; x is x 7 When the current of the N line of the protection device is larger than 60A, the value is 1; otherwise, taking a value of 0; x is x 8 If at least one phase of current in three-phase current of the protection device meets waveform distortion judgment, second harmonic component or third harmonicThe wave component is larger than 10%, and the value is 1; otherwise, the value 0 is taken.
Further, in step S5, the mode of calculating the waveform detection result of the interval according to the detection result decision table specifically includes:
when y is 1 Is 4, y 2 Is 1, y 5 When the value is 0, the waveform detection result is that the current loop is normal;
when y is 1 Is 4, y 2 When the value is 0, the waveform detection result is that the protection device is provided with a reason to cause the abnormality of the differential flow;
when y is 1 Is 2 to 4, y 3 Is 1, y 4 Is 1, y 5 When the current loop is 0, the waveform detection result is that the two points of the current loop are grounded, so that a differential current is abnormal;
when y is 1 Is 0 to 2, y 3 Is 1, y 4 Is 1, y 5 When the value is 1, the waveform detection result is that the neutral line resistance is increased to cause the differential current abnormality;
when y is 1 Is 0 to 1, y 3 Is 1, y 4 When the value is 0, the waveform detection result is that the neutral line is broken, so that the differential flow is abnormal;
when y is 1 Is 4, y 3 Is 1, y 4 Is 1, y 5 When the value is 1, the waveform detection result is that CT saturation causes differential flow abnormality.
In summary, the embodiment of the invention has the following beneficial effects:
according to the differential flow anomaly detection method provided by the invention, the protective interval list to be detected is automatically selected, and the calculation such as amplitude correction, phase correction, waveform comparison interval selection and the like is carried out on the waveforms of the protective device and the fault recorder at each interval in the list, so that the influence of inherent problems such as inconsistent loop polarity, time synchronization deviation, waveform compression and the like on the accuracy of waveform comparison results is avoided; performing waveform comparison, waveform amplitude characteristic calculation and waveform distortion characteristic calculation to form waveform characteristic vectors, and multiplying the waveform characteristic matrices by the waveform characteristic vectors to obtain waveform detection result vectors; substituting the waveform detection result vector into a waveform detection result decision table to obtain a differential flow abnormal detection result. The detection accuracy is high, and the engineering practicability is strong; and the reason of the abnormal difference flow is clear in positioning, the tripping event can be supported to be rapidly processed, the risk early warning of the abnormal difference flow is timely issued, and the method plays an important role in guaranteeing the safe and stable operation of the power grid.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are required in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that it is within the scope of the invention to one skilled in the art to obtain other drawings from these drawings without inventive faculty.
FIG. 1 is a schematic diagram of a main flow of the differential flow anomaly detection method according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings, for the purpose of making the objects, technical solutions and advantages of the present invention more apparent.
Fig. 1 is a schematic diagram of an embodiment of a differential flow anomaly detection method according to the present invention. In this embodiment, the method comprises the steps of:
and S1, detecting whether single-phase or inter-phase short-circuit grounding faults exist in the power grid, if so, reading protection event data of the whole power grid when the power grid faults occur, screening interval data of all 110kV and above with starting protection events, and obtaining a differential flow abnormal detection interval list.
Step S2, all interval protection device waveforms and all fault recorder waveforms are called in the flow abnormality detection interval list, and amplitude correction and phase correction are carried out on all current waveforms;
in a specific embodiment, due to the inherent problems of inconsistent transformation ratio, inconsistent polarity, and compressed current waveform of the protection device of the fault recorder set and the differential set current loop, if the fault recorder and the protection device waveform are directly used for comparison, the waveform comparison accuracy is very low. In order to improve the accuracy of waveform comparison, waveform amplitude correction and phase correction should be carried out before waveform comparison;
specifically, the waveform amplitude correction is to keep the amplitude of the current waveform of the differential group unchanged, correct the three-phase current and N-line current amplitude of the fault record group, and filter the non-periodic components of the three-phase current and N-line current of the fault record group by multiplying the three-phase current and N-line current of the fault record group by a transformation ratio correction coefficient m; the transformation ratio correction coefficient m is calculated according to the following formula:
wherein CT 1 CT is the CT transformation ratio of the current loop of the differential group 2 The CT transformation ratio of the current loop of the fault record wave group.
More specifically, the method for performing phase correction on the current waveform specifically includes:
the phase angle of the differential group phase current is kept unchanged, the phase of the three-phase current of the fault wave recording group is corrected, and the three-phase current of the fault wave recording group is multiplied by a phase correction coefficient n respectively 1 ；
The phase correction coefficient n 1 Calculated according to the following formula:
wherein θ 1 For correcting angle, when the polarity of the current loop of the fault record wave group is close to the bus, theta 1 Is 0; when the polarity of the fault record wave group current loop is close to the circuit, theta 1 180;
correcting the polarity of the N-line currents of the differential current set, and multiplying the N-line currents of the differential current set by a phase correction coefficient N 2 ；
The phase correction coefficient n 2 Calculated according to the following formula:
wherein θ 2 In order to correct the angle of the angle,when N lines are connected with the nonpolar end of the N line sampling small CT of the protection device, theta 2 Is 0; when N lines are connected with the polarity end of the N line sampling small CT of the protection device, theta 2 180;
correcting the polarity of N line currents of the fault wave recording current group, and multiplying the N line currents of the fault wave recording current group by a phase correction coefficient N 3 ；
The phase correction coefficient n 3 The calculation is performed according to the following formula:
wherein θ 3 For correcting angle, when N line is connected to the non-polar end of the N line sampling small CT of the fault wave recording device and the polarity of the fault wave recording group current loop is close to the bus, N line is connected to the polar end of the N line sampling small CT of the fault wave recording device and the polarity of the fault wave recording group current loop is close to the line, θ 3 Is 0; when the N line is connected to the polarity end of the N line sampling small CT of the fault wave recording device and the polarity of the fault wave recording group current loop is close to the bus, the N line is connected to the non-polarity end of the N line sampling small CT of the fault wave recording device and the polarity of the fault wave recording group current loop is close to the line, the theta 3 180.
S3, selecting a protection interval from the fetched data, and intercepting a protection device current waveform and a fault recorder current waveform of the interval in a waveform comparison section;
in a specific embodiment, the starting point and the ending point of the current waveform of the protection device and the current waveform of the fault recorder are set for interception according to the following modes: the starting point of the waveform comparison section of the protection device is set as the starting time of the waveform comparison section of the protection device, whether the fault recorder and the protection device are consistent in time or not is judged, if the fault recorder and the protection device are consistent in time, the starting point of the waveform of the fault record group and the protection device are at the same time, and if the fault recorder and the protection device are inconsistent in time, the starting point is the time when the amplitude of the mutation quantity of the waveform of the fault record group reaches the amplitude of the mutation quantity of the protection device at the starting time for the first time;
the end points of the waveform comparison section of the fault recorder and the protection device are floating end points, and if the fault current disappears within 100ms after the start point, the moment of the disappearance of the fault current is taken as the end point; if the fault current does not disappear within 100ms after the start point, the end point is set to 100ms after the start point.
S4, performing waveform comparison, waveform amplitude, waveform distortion and harmonic characteristic calculation on the intercepted current waveform of the protection device and the current waveform of the fault recorder to obtain a waveform characteristic vector X of the interval;
in the specific embodiment, the current differential protection principle is simple, the performance is excellent, and the current differential protection is the most widely applied main protection at present. When the current loop is not abnormal and the protection device is set correctly, the differential current value is always close to 0 under the condition of normal operation or out-of-zone fault, and misoperation is avoided; when the current loop is grounded at two points, the neutral line is broken, the neutral line resistance is increased, the CT is saturated or the protection device is set wrong, the protection differential current is abnormally increased, and the protection misoperation can be possibly caused.
Considering that two or more small probability events do not occur simultaneously, it is normal that at least one current loop exists in the current loops formed by the different secondary windings of the current transformer. Because the abnormal current loop of the fault recorder group does not cause protection misoperation, the group of current waveforms can be selected as reference comparison waveforms. Comparing the current waveform of the differential group current loop with the reference waveform, and if the comparison result is inconsistent, indicating that the differential group current loop is abnormal;
in order to distinguish specific reasons causing the abnormal difference flow, waveform characteristics of the current loop under the conditions of two-point grounding, neutral line disconnection, neutral line resistance increase, CT saturation and protection device setting error are analyzed in sequence, and analysis results are shown in the following table:
when the current loop is normal, the currents of the phase A, the phase B, the phase C and the line N are the same, the virtual differential current is the same as the differential current of the protection device, and the protection device has no current distortion and harmonic wave;
when the protection device is set in error, the currents of the phase A, the phase B, the phase C and the line N are the same, and the virtual differential flow is different from the differential flow of the protection device;
when two points of the current loop are grounded, at least two current channels in A phase, B phase, C phase and N line are different, the differential current amplitude of the protection device is larger than a set value, the N line current amplitude of the protection device is larger than the set value, and the protection device has no current distortion and harmonic wave
When the neutral line resistance is increased, at least two current channels in the phase A, the phase B, the phase C and the line N are different, the differential current amplitude of the protection device is larger than a set value, the current amplitude of the line N of the protection device is larger than the set value, and the protection device has current distortion and harmonic waves;
when the neutral line is broken, at least three current channels in the phase A, the phase B, the phase C and the phase N are different, the differential current amplitude of the protection device is larger than a set value, and the current amplitude of the N line of the protection device is smaller than the set value;
when CT is saturated, the currents of the phase A, the phase B, the phase C and the line N are the same, the differential current amplitude of the protection device is larger than a set value, the current amplitude of the line N of the protection device is larger than the set value, and the protection device has current distortion and harmonic waves.
Step S5, calculating a waveform detection result feature vector Y of the interval, and bringing the waveform detection result feature vector Y into a waveform detection result decision table to obtain a differential flow abnormal detection result of the guard interval, and continuously repeating the process until waveform detection results of all the guard intervals are calculated;
in a specific embodiment, the waveform detection result feature vector for calculating the interval is specifically calculated according to the following formula:
X＝[x 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 ] T
Y＝[y 1 y 2 y 3 y 4 y 5 ] T
Y＝PX
wherein X is a waveform characteristic vector, P is a waveform characteristic matrix, Y is a waveform detection result vector; x is x 1 When the phase A current of the fault recorder is the same as the phase A current of the protection device, the value 1 is taken, and when the phase A current is different, the value 0 is taken; x is x 2 When the phase B current of the fault recorder is the same as the phase B current of the protection device, the value is 1, and when the phase B current is different, the value is 0; x is x 3 When the C-phase current of the fault recorder is the same as the C-phase current of the protection device, the value is 1, and when the C-phase current of the fault recorder is different from the C-phase current of the protection device, the value is 0; x is x 4 When the waveform of the N line current of the fault recorder is the same as that of the N line current of the protection device, the value 1 is taken, and when the waveform of the N line current of the fault recorder is different from that of the N line current of the protection device, the value 0 is taken; x is x 5 When the comparison result of the virtual differential stream and the differential stream of the protection device is the same, the value 1 is taken; if not, the value is 0; x is x 6 When the differential flow of the protection device is larger than 60A, the value is 1; otherwise, taking a value of 0; x is x 7 When the current of the N line of the protection device is larger than 60A, the value is 1; otherwise, taking a value of 0; x is x 8 In the three-phase current of the protection device, if at least one phase of current meets waveform distortion judgment, and the second harmonic component or the third harmonic component is more than 10%, the value is 1; otherwise, the value 0 is taken.
More specifically, as shown in the following table, the mode of calculating the waveform detection result of the interval according to the detection result decision table specifically includes:
and (3) table notes: (1) "-" indicates that the waveform characteristic does not affect the corresponding row waveform detection result judgment.
(2) The virtual differential flow refers to differential current obtained by calculating the differential current by the differential flow abnormality detection program according to the differential flow calculation method by utilizing the current of the protection device on the side and the current of the protection device on the corresponding opposite side. The comparison of the virtual differential flow and the differential flow of the protection device refers to the comparison of the virtual differential flows and the corresponding differential flows of the protection device, and if the comparison results are the same, the comparison results are the same; if only one comparison result is different, the comparison result is judged to be different.
When y is 1 Is 4, y 2 Is 1, y 5 When the value is 0, the waveform detection result is that the current loop is normal;
when y is 1 Is 4, y 2 When the value is 0, the waveform detection result is that the protection device is provided with a reason to cause the abnormality of the differential flow;
when y is 1 Is 2 to 4, y 3 Is 1, y 4 Is 1, y 5 When the current loop is 0, the waveform detection result is that the two points of the current loop are grounded, so that a differential current is abnormal;
when y is 1 Is 0 to 2, y 3 Is 1, y 4 Is 1, y 5 When the value is 1, the waveform detection result is that the neutral line resistance is increased to cause the differential current abnormality;
when y is 1 Is 0 to 1, y 3 Is 1, y 4 When the value is 0, the waveform detection result is that the neutral line is broken, so that the differential flow is abnormal;
when y is 1 Is 4, y 3 Is 1, y 4 Is 1, y 5 When the value is 1, the waveform detection result is that CT saturation causes differential flow abnormality.
In summary, the embodiment of the invention has the following beneficial effects:
according to the differential flow anomaly detection method provided by the invention, the protective interval list to be detected is automatically selected, and the calculation such as amplitude correction, phase correction, waveform comparison interval selection and the like is carried out on the waveforms of the protective device and the fault recorder at each interval in the list, so that the influence of inherent problems such as inconsistent loop polarity, time synchronization deviation, waveform compression and the like on the accuracy of waveform comparison results is avoided; performing waveform comparison, waveform amplitude characteristic calculation and waveform distortion characteristic calculation to form waveform characteristic vectors, and multiplying the waveform characteristic matrices by the waveform characteristic vectors to obtain waveform detection result vectors; substituting the waveform detection result vector into a waveform detection result decision table to obtain a differential flow abnormal detection result. The detection accuracy is high, and the engineering practicability is strong; and the reason of the abnormal difference flow is clear in positioning, the tripping event can be supported to be rapidly processed, the risk early warning of the abnormal difference flow is timely issued, and the method plays an important role in guaranteeing the safe and stable operation of the power grid.
The above disclosure is only a preferred embodiment of the present invention, and it is needless to say that the scope of the invention is not limited thereto, and therefore, the equivalent changes according to the claims of the present invention still fall within the scope of the present invention.
Claims (6)
1. A differential flow anomaly detection method, comprising the steps of:
step S1, detecting whether single-phase or inter-phase short-circuit grounding faults exist in a power grid, if so, reading protection event data of the whole power grid when the power grid faults occur, screening interval data of all 110kV and above with starting protection events, and obtaining a differential flow abnormal detection interval list;
step S2, all the waveforms of the interval protection device and all the waveforms of the fault recorder are called in the differential flow abnormal detection interval list, and amplitude correction and phase correction are carried out on all the current waveforms;
s3, selecting a protection interval from the fetched data, and intercepting a protection device current waveform and a fault recorder current waveform of the interval in a waveform comparison section;
s4, performing waveform comparison, waveform amplitude, waveform distortion and harmonic characteristic calculation on the intercepted current waveform of the protection device and the current waveform of the fault recorder to obtain waveform characteristic vectors of the interval;
step S5, calculating the characteristic vector of the waveform detection result of the interval, and calculating the waveform detection result of the interval according to a detection result decision table;
in step S2, the method for correcting the amplitude of all current waveforms specifically includes that the amplitude of the current waveform of the differential set is kept unchanged, the amplitudes of the three-phase current and the N-line current of the fault record set are corrected, the three-phase current and the N-line current of the fault record set are multiplied by a transformation ratio correction coefficient m, and then non-periodic components of the three-phase current and the N-line current of the fault record set are filtered;
the method for carrying out phase correction on all current waveforms specifically comprises the following steps:
the phase angle of the differential group phase current is kept unchanged, the phase of the three-phase current of the fault wave recording group is corrected, and the three-phase current of the fault wave recording group is multiplied by a phase correction coefficient n respectively 1 ；
The phase correction coefficient n 1 Calculated according to the following formula:
wherein θ 1 For correcting angle, when the polarity of the current loop of the fault record wave group is close to the bus, theta 1 Is 0; when the polarity of the fault record wave group current loop is close to the circuit, theta 1 180;
correcting the polarity of the N-line currents of the differential current set, and multiplying the N-line currents of the differential current set by a phase correction coefficient N 2 ；
The phase correction coefficient n 2 Calculated according to the following formula:
wherein θ 2 For angle correction, θ is calculated when the N-wire is connected to the non-polar end of the N-wire sampling small CT of the protection device 2 Is 0; when N lines are connected with the polarity end of the N line sampling small CT of the protection device, theta 2 180; correcting the polarity of the N line current of the fault wave recording current group, and multiplying the N line current of the fault wave recording current group by a phase correction coefficient N 3 ；
The phase correction coefficient n 3 The calculation is performed according to the following formula:
wherein θ 3 For correcting the angle, when N lines are connected to the fault wave recording device, N lines are sampled to be small CT is a non-polar end, and when the polarity of the fault wave recording group current loop is close to a bus, and the N line is connected with the polarity end of the fault wave recording device N line sampling small CT, and the polarity of the fault wave recording group current loop is close to a line, theta 3 Is 0; when the N line is connected to the polarity end of the N line sampling small CT of the fault wave recording device and the polarity of the fault wave recording group current loop is close to the bus, the N line is connected to the non-polarity end of the N line sampling small CT of the fault wave recording device and the polarity of the fault wave recording group current loop is close to the line, the theta 3 180.
2. The method of claim 1, wherein the transformation ratio correction factor m is calculated according to the following formula:
wherein CT 1 CT is the CT transformation ratio of the current loop of the differential group 2 The CT transformation ratio of the current loop of the fault record wave group.
3. The method according to claim 2, wherein in step S3, the intercepting the protection device current waveform and the fault recorder current waveform of the interval in the waveform comparison section is specifically performed by setting starting points and ending points of the protection device current waveform and the fault recorder current waveform according to the following manner:
the starting point of the waveform comparison section of the protection device is set as the starting time of the waveform comparison section of the protection device, whether the fault recorder and the protection device are consistent in time or not is judged, if the fault recorder and the protection device are consistent in time, the starting point of the waveform of the fault record group and the protection device are at the same time, and if the fault recorder and the protection device are inconsistent in time, the starting point is the time when the amplitude of the mutation quantity of the waveform of the fault record group reaches the amplitude of the mutation quantity of the protection device at the starting time for the first time;
the end points of the waveform comparison section of the fault recorder and the protection device are floating end points, and if the fault current disappears within 100ms after the start point, the moment of the disappearance of the fault current is taken as the end point; if the fault current does not disappear within 100ms after the start point, the end point is set to 100ms after the start point.
4. The method of claim 3, wherein in step S4, the performing waveform comparison, waveform amplitude, waveform distortion and harmonic feature calculation to obtain the waveform feature vector of the interval specifically includes:
when the current loop is normal, the currents of the phase A, the phase B, the phase C and the line N are the same, the virtual differential current is the same as the differential current of the protection device, and the protection device has no current distortion and harmonic wave;
when the protection device is set in error, the currents of the phase A, the phase B, the phase C and the line N are the same, and the virtual differential flow is different from the differential flow of the protection device;
when two points of the current loop are grounded, at least two current channels in the A phase, the B phase, the C phase and the N line are different, the difference current amplitude of the protection device is larger than a set value, the N line current amplitude of the protection device is larger than the set value, and the protection device has no current distortion and harmonic wave;
when the neutral line resistance is increased, at least two current channels in the phase A, the phase B, the phase C and the line N are different, the differential current amplitude of the protection device is larger than a set value, the current amplitude of the line N of the protection device is larger than the set value, and the protection device has current distortion and harmonic waves;
when the neutral line is broken, at least three current channels in the phase A, the phase B, the phase C and the phase N are different, the differential current amplitude of the protection device is larger than a set value, and the current amplitude of the N line of the protection device is smaller than the set value;
when CT is saturated, the currents of the phase A, the phase B, the phase C and the line N are the same, the differential current amplitude of the protection device is larger than a set value, the current amplitude of the line N of the protection device is larger than the set value, and the protection device has current distortion and harmonic waves.
5. The method according to claim 1, wherein in step S5, the waveform detection result feature vector for calculating the interval is calculated according to the following formula:
X＝[x 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 ] T
Y＝[y 1 y 2 y 3 y 4 y 5 ] T
Y＝PX
wherein X is a waveform characteristic vector, P is a waveform characteristic matrix, Y is a waveform detection result vector; x is x 1 When the phase A current of the fault recorder is the same as the phase A current of the protection device, the value 1 is taken, and when the phase A current is different, the value 0 is taken; x is x 2 When the phase B current of the fault recorder is the same as the phase B current of the protection device, the value is 1, and when the phase B current is different, the value is 0; x is x 3 When the C-phase current of the fault recorder is the same as the C-phase current of the protection device, the value is 1, and when the C-phase current of the fault recorder is different from the C-phase current of the protection device, the value is 0; x is x 4 When the waveform of the N line current of the fault recorder is the same as that of the N line current of the protection device, the value 1 is taken, and when the waveform of the N line current of the fault recorder is different from that of the N line current of the protection device, the value 0 is taken; x is x 5 When the comparison result of the virtual differential stream and the differential stream of the protection device is the same, the value 1 is taken, and when the comparison result is different, the value 0 is taken; x is x 6 When the differential flow of the protection device is larger than 60A, the value is 1; otherwise, taking a value of 0; x is x 7 When the current of the N line of the protection device is larger than 60A, the value is 1; otherwise, taking a value of 0; x is x 8 In the three-phase current of the protection device, if at least one phase of current meets waveform distortion judgment, and the second harmonic component or the third harmonic component is more than 10%, the value is 1; otherwise, the value 0 is taken.
6. The method of claim 5, wherein in step S5, the mode of calculating the waveform detection result of the interval according to the detection result decision table specifically includes:
when y is 1 Is 4, y 2 Is 1, y 5 When the value is 0, the waveform detection result is that the current loop is normal;
when y is 1 Is 4, y 2 When the value is 0, the waveform detection result is that the protection device is provided with a reason to cause the abnormality of the differential flow;
when y is 1 Is 2 to 4, y 3 Is 1, y 4 Is 1, y 5 When the value is 0, the waveform detection result is that the two points of the current loop are connectedGround causes differential flow anomalies;
when y is 1 Is 0 to 2, y 3 Is 1, y 4 Is 1, y 5 When the value is 1, the waveform detection result is that the neutral line resistance is increased to cause the differential current abnormality;
when y is 1 Is 0 to 1, y 3 Is 1, y 4 When the value is 0, the waveform detection result is that the neutral line is broken, so that the differential flow is abnormal;
when y is 1 Is 4, y 3 Is 1, y 4 Is 1, y 5 When the value is 1, the waveform detection result is that CT saturation causes differential flow abnormality.
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