CN116706835B - Method, device, medium and equipment for identifying inrush current of transformer - Google Patents
Method, device, medium and equipment for identifying inrush current of transformer Download PDFInfo
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- CN116706835B CN116706835B CN202211714379.3A CN202211714379A CN116706835B CN 116706835 B CN116706835 B CN 116706835B CN 202211714379 A CN202211714379 A CN 202211714379A CN 116706835 B CN116706835 B CN 116706835B
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- 230000003442 weekly effect Effects 0.000 claims abstract description 3
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Classifications
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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
- H02H7/04—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 for transformers
- H02H7/045—Differential protection of transformers
-
- 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
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
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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
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- General Physics & Mathematics (AREA)
- Protection Of Transformers (AREA)
Abstract
The invention discloses a transformer inrush current identification method, a device, a medium and equipment. The method comprises the following steps: according to the collected three-phase current of the transformer at the high-voltage side and the three-phase current of the transformer at the low-voltage side of each weekly wave, determining the variation of a differential current sampling value of each sampling point and the cycle before the fault in the cycle at the current moment; calculating a reference comparison quantity in the cycle according to the variation quantity of the differential current sampling value of each sampling point in the cycle at the current moment; forming an adjacent set by each sampling point and the preset number of sampling points in the cycle, and calculating the differential value of each sampling point in all the adjacent sets; respectively carrying out accumulated addition on the absolute value of the sum of the variation of the differential current sampling value and the differential value of each sampling point in each adjacent set to determine a cycle frame of each adjacent set; and selecting the minimum value of all the immediately adjacent concentrated cycle frames, and determining the inrush current working condition of the transformer by using an inrush current identification working condition criterion formed by the reference comparison quantity, wherein the inrush current working condition is used for determining whether differential protection is opened or not.
Description
Technical Field
The present invention relates to the field of power system protection technologies, and in particular, to a transformer inrush current identification method, device, medium, and apparatus.
Background
Transformers are one of the important constituent elements of an electrical power system, the safe and reliable operation of which is critical to the electrical grid. And the transformer protection device is the most effective means for realizing the rapid and reliable isolation of the transformer faults. The transformer protection device takes differential protection as main protection, overcurrent protection, impedance protection and the like as backup protection. When the transformer is in no-load switching-on with a power system or external fault removal voltage recovery, or other transformers connected in parallel are in no-load switching-on, excitation surge current can be generated. When the excitation surge current is larger than the differential protection fixed value and enters the action zone, the false action of the differential protection can be caused. Therefore, for transformer differential protection, accurate identification of magnetizing inrush current is critical to avoid differential protection malfunction. The content of the second harmonic in the differential current is used in conventional differential protection to identify the magnetizing inrush current. When the second harmonic content in the differential current is greater than a certain threshold (typically 15%), the differential protection is blocked by the magnetizing inrush current. When the second harmonic content is less than the threshold value, the internal fault is considered, and differential protection is opened. However, because of the change of parameters such as ferromagnetic materials, capacity, remanence level and the like of the transformer, exciting inrush current working conditions with the second harmonic content less than 15% occur for a plurality of times in actual engineering, and misoperation of a protection device is caused. Therefore, a method for more effectively recognizing the excitation surge current is sought.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a transformer inrush current identification method, a device, a medium and equipment.
According to one aspect of the present invention, there is provided a transformer inrush current identification method, including:
according to the collected three-phase current of the transformer at the high-voltage side and the three-phase current of the transformer at the low-voltage side of each weekly wave, determining the variation of a differential current sampling value of each sampling point and the cycle before the fault in the cycle at the current moment;
calculating a reference comparison quantity in the cycle according to the variation quantity of the differential current sampling value of each sampling point in the cycle at the current moment;
forming an adjacent set by each sampling point and the preset number of sampling points in the cycle, and calculating the differential value of each sampling point in all the adjacent sets;
respectively carrying out accumulated addition on the absolute value of the sum of the variation of the differential current sampling value and the differential value of each sampling point in each adjacent set to determine a cycle frame of each adjacent set;
and selecting the minimum value of all the immediately adjacent concentrated cycle frames, and determining the inrush current working condition of the transformer by using an inrush current identification working condition criterion formed by the reference comparison quantity, wherein the inrush current working condition is used for determining whether differential protection is opened or not.
Optionally, each cycle includes 24 sampling points, and determining, according to the collected three-phase current of the transformer on the high-voltage side and the three-phase current of the transformer on the low-voltage side of each cycle, a variation of a differential current sampling value of each sampling point and a cycle before the fault in the cycle at the current moment includes:
collecting high-voltage side three-phase current and low-voltage side three-phase current of 24 sampling points of each cycle wave of a transformer;
determining the variation of differential current sampling value according to the differential current sampling value difference of high-voltage side three-phase current and low-voltage side three-phase current of 24 sampling points in the current time period and 24 sampling points in the previous fault period, wherein
i ∑i ＝i Hi +i L i*N T
δi ∑ i＝i ∑ i-i ∑(i-)
In the formula, δi ∑i For the variation of the differential current sampling value, i ∑i I is the sampling value of differential current in the current cycle ∑(i-) I is the differential current sampling value of the previous cycle of the fault Hi At t i Three-phase current at high voltage side at moment, i Li At t i Low-side three-phase current at time, N T Is the transformation ratio of the transformer.
Optionally, according to the variation of the differential current sampling value of each sampling point in the cycle at the current moment, the calculation formula for calculating the reference comparison amount in the cycle is as follows:
of which, 24 k As a reference comparison quantity, δi ∑i And k is the number of the current sampling point for the variation of the differential current sampling value.
Optionally, each sampling point and the previous predetermined number of sampling points in the cycle are formed into an adjacent set, and the formula for calculating the differential value of each sampling point in all the adjacent sets is as follows:
δdi ∑i ＝δi ∑i -δi ∑i-1
wherein δdi Σi Is a differential value, δi ∑i Delta i is the variation of the differential current sampling value of the current sampling point ∑i-1 The differential current sampling value variation amount of the previous sampling point of the current sampling point.
Optionally, the pre-reserved number of sampling points is 8 sampling points, the immediately adjacent set includes 9 sampling points, and the differential current sampling value variation amounts of the sampling points in each immediately adjacent set and the absolute value of the sum of the differential values are respectively added together in a cumulative way, so that the calculation formula of the cyclic frame of each immediately adjacent set is determined as follows:
wherein,delta i is a cyclic frame of the immediate neighbor set ∑i For the variation of the differential current sampling value δdi ∑i Is the differential value of the variation of the differential current sampling value.
Optionally, the operation of selecting the minimum value of all immediately adjacent concentrated cyclic frames includes:
correcting the cyclic frames of the adjacent set;
and selecting a minimum value according to the corrected cyclic frames of all the adjacent sets, wherein the selection formula of the minimum value is as follows:
where k is the current sample point number.
Optionally, the operation of correcting the cyclic frame of the immediate neighbor set includes:
when n= (k-15) -k, direct copying is performed without correction
When n= (k-23) to (k-16), the data cycle correction is as follows:
wherein n represents the serial numbers of 24 sampling points in the current frame, i ∑n Is the three-phase differential current sampling value of the nth sampling point.
Optionally, the inrush current identification condition criteria are:
wherein,
and selecting the minimum value of all the immediately adjacent concentrated cycle frames, and determining the inrush current working condition of the transformer by using the inrush current identification working condition criterion formed by the reference comparison quantity, wherein the method comprises the following steps:
under the condition that the minimum value of the circulating frame meets the inrush current identification working condition criterion, opening differential protection for a non-inrush current working condition;
under the condition that the minimum value of the circulating frame does not meet the inrush current identification working condition criterion, the differential protection is not opened for the inrush current working condition.
According to another aspect of the present invention, there is provided a transformer inrush current identification device, comprising:
the first determining module is used for determining the variation of the differential current sampling value of each sampling point and the cycle before the fault in the cycle at the current moment according to the collected high-voltage side three-phase current and low-voltage side three-phase current of the transformer in the cycle;
the first calculation module is used for calculating the reference comparison quantity in the current time according to the variation quantity of the differential current sampling value of each sampling point in the cycle;
the second calculation module is used for forming an adjacent set by each sampling point and the preset number of sampling points in the cycle, and calculating the differential value of each sampling point in all the adjacent sets;
the second determining module is used for respectively carrying out cumulative addition on the absolute value of the sum of the variation of the differential current sampling value and the differential value of each sampling point in each adjacent set to determine the cycle frame of each adjacent set;
and the third determining module is used for selecting the minimum value of all the immediately adjacent concentrated cycle frames, and determining the inrush current working condition of the transformer by using the inrush current identification working condition criterion formed by the reference comparison quantity, wherein the inrush current working condition is used for determining whether the differential protection is opened or not.
According to a further aspect of the present invention there is provided a computer readable storage medium storing a computer program for performing the method according to any one of the above aspects of the present invention.
According to still another aspect of the present invention, there is provided an electronic device including: a processor; a memory for storing the processor-executable instructions; the processor is configured to read the executable instructions from the memory and execute the instructions to implement the method according to any of the above aspects of the present invention.
Therefore, the invention can accurately and effectively identify the excitation surge current of the transformer through extracting the collapse characteristics of the differential current waveform. Therefore, misoperation of the transformer protection under the excitation surge working condition is avoided, and the safety of the transformer protection is improved.
Drawings
Exemplary embodiments of the present invention may be more completely understood in consideration of the following drawings:
fig. 1 is a schematic flow chart of a transformer inrush current identification method according to an exemplary embodiment of the present invention;
FIG. 2 is a schematic diagram of a close-proximity set loop calculation provided by an exemplary embodiment of the present invention;
FIG. 3 is a schematic diagram of waveform discontinuity identification provided by an exemplary embodiment of the present invention;
FIG. 4 is a schematic diagram of CT measurement current waveforms of three-phase bushings at the net side and the valve side of YD converter transformer according to an exemplary embodiment of the present invention;
FIG. 5 is a schematic diagram of a three-phase differential current provided by an exemplary embodiment of the present invention;
FIG. 6 is a schematic illustration of differential flow variation provided by an exemplary embodiment of the present invention;
FIG. 7 is a diagram of reference amounts of comparison of criteria provided by an exemplary embodiment of the present invention;
FIG. 8 is a schematic diagram of minima in a close-proximity set provided by an exemplary embodiment of the present invention;
FIG. 9 is a schematic diagram of a simulation result of criteria provided by an exemplary embodiment of the present invention;
fig. 10 is a schematic structural diagram of a transformer inrush current identification device according to an exemplary embodiment of the present invention;
fig. 11 is a structure of an electronic device provided in an exemplary embodiment of the present invention.
Detailed Description
Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. It should be apparent that the described embodiments are only some embodiments of the present invention and not all embodiments of the present invention, and it should be understood that the present invention is not limited by the example embodiments described herein.
It should be noted that: the relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise.
It will be appreciated by those of skill in the art that the terms "first," "second," etc. in embodiments of the present invention are used merely to distinguish between different steps, devices or modules, etc., and do not represent any particular technical meaning nor necessarily logical order between them.
It should also be understood that in embodiments of the present invention, "plurality" may refer to two or more, and "at least one" may refer to one, two or more.
It should also be appreciated that any component, data, or structure referred to in an embodiment of the invention may be generally understood as one or more without explicit limitation or the contrary in the context.
In addition, the term "and/or" in the present invention is merely an association relationship describing the association object, and indicates that three relationships may exist, for example, a and/or B may indicate: a exists alone, A and B exist together, and B exists alone. In the present invention, the character "/" generally indicates that the front and rear related objects are an or relationship.
It should also be understood that the description of the embodiments of the present invention emphasizes the differences between the embodiments, and that the same or similar features may be referred to each other, and for brevity, will not be described in detail.
Meanwhile, it should be understood that the sizes of the respective parts shown in the drawings are not drawn in actual scale for convenience of description.
The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods, and apparatus should be considered part of the specification.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.
Embodiments of the invention are operational with numerous other general purpose or special purpose computing system environments or configurations with electronic devices, such as terminal devices, computer systems, servers, etc. Examples of well known terminal devices, computing systems, environments, and/or configurations that may be suitable for use with the terminal device, computer system, server, or other electronic device include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients, hand-held or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network personal computers, small computer systems, mainframe computer systems, and distributed cloud computing technology environments that include any of the foregoing, and the like.
Electronic devices such as terminal devices, computer systems, servers, etc. may be described in the general context of computer system-executable instructions, such as program modules, being executed by a computer system. Generally, program modules may include routines, programs, objects, components, logic, data structures, etc., that perform particular tasks or implement particular abstract data types. The computer system/server may be implemented in a distributed cloud computing environment in which tasks are performed by remote processing devices that are linked through a communications network. In a distributed cloud computing environment, program modules may be located in both local and remote computing system storage media including memory storage devices.
Exemplary method
Fig. 1 is a schematic flow chart of a transformer inrush current identification method according to an exemplary embodiment of the present invention. The embodiment can be applied to an electronic device, as shown in fig. 1, the transformer inrush current identification method 100 includes the following steps:
step 101, determining the variation of differential current sampling values of each sampling point and the cycle before the fault in the cycle at the current moment according to the collected high-voltage side three-phase current and low-voltage side three-phase current of the transformer in the cycle;
102, calculating a reference comparison amount in a current time according to the variation of a differential current sampling value of each sampling point in the cycle;
step 103, forming each sampling point and the previous preset number of sampling points in the cycle into an adjacent set, and calculating the differential value of each sampling point in all the adjacent sets;
104, respectively carrying out accumulated addition on the variation of the differential current sampling value of each sampling point in each adjacent set and the absolute value of the sum of the differential values to determine a cycle frame of each adjacent set;
step 105, selecting the minimum value of all the immediately adjacent concentrated cycle frames, and determining the inrush current working condition of the transformer by using the inrush current identification working condition criterion formed by the reference comparison quantity, wherein the inrush current working condition is used for determining whether to open differential protection.
Optionally, each cycle includes 24 sampling points, and determining, according to the collected three-phase current of the transformer on the high-voltage side and the three-phase current of the transformer on the low-voltage side of each cycle, a variation of a differential current sampling value of each sampling point and a cycle before the fault in the cycle at the current moment includes:
collecting high-voltage side three-phase current and low-voltage side three-phase current of 24 sampling points of each cycle wave of a transformer;
determining the variation of differential current sampling value according to the differential current sampling value difference of high-voltage side three-phase current and low-voltage side three-phase current of 24 sampling points in the current time period and 24 sampling points in the previous fault period, wherein
i ∑i ＝i Hi +i Li *N T
δi ∑i ＝i ∑i -i ∑(i-)
In the formula, δi ∑i For the variation of the differential current sampling value, i ∑i I is the sampling value of differential current in the current cycle ∑(i-) I is the differential current sampling value of the previous cycle of the fault Hi At t i Three-phase current at high voltage side at moment, i Li At t i Low-side three-phase current at time, N T Is the transformation ratio of the transformer.
Optionally, according to the variation of the differential current sampling value of each sampling point in the cycle at the current moment, the calculation formula for calculating the reference comparison amount in the cycle is as follows:
of which, 24 k As a reference comparison quantity, δi ∑j And k is the number of the current sampling point for the variation of the differential current sampling value.
Optionally, each sampling point and the previous predetermined number of sampling points in the cycle are formed into an adjacent set, and the formula for calculating the differential value of each sampling point in all the adjacent sets is as follows:
δdi ∑i ＝δi ∑i -δi ∑i-1
wherein δdi Σi Is a differential value, δi ∑i Delta i is the variation of the differential current sampling value of the current sampling point ∑i-1 The differential current sampling value variation amount of the previous sampling point of the current sampling point.
Optionally, the pre-reserved number of sampling points is 8 sampling points, the immediately adjacent set includes 9 sampling points, and the differential current sampling value variation amounts of the sampling points in each immediately adjacent set and the absolute value of the sum of the differential values are respectively added together in a cumulative way, so that the calculation formula of the cyclic frame of each immediately adjacent set is determined as follows:
wherein,delta i is a cyclic frame of the immediate neighbor set ∑i For the variation of the differential current sampling value δdi ∑i Is the differential value of the variation of the differential current sampling value.
Optionally, the operation of selecting the minimum value of all immediately adjacent concentrated cyclic frames includes:
correcting the cyclic frames of the adjacent set;
and selecting a minimum value according to the corrected cyclic frames of all the adjacent sets, wherein the selection formula of the minimum value is as follows:
wherein k is the number of the current sampling point, each sampling point in the previous cycle from the current sampling point corresponds to one adjacent set, and the total number of the adjacent sets is 24.
Optionally, the operation of correcting the cyclic frame of the immediate neighbor set includes:
when n= (k-15) -k, direct copying is performed without correction
When n= (k-23) to (k-16), the data cycle correction is as follows:
wherein n represents the serial numbers of 24 sampling points in the current frame, i ∑n Is the three-phase differential current sampling value of the nth sampling point.
Optionally, the inrush current identification condition criteria are:
wherein,
and selecting the minimum value of all the immediately adjacent concentrated cycle frames, and determining the inrush current working condition of the transformer by using the inrush current identification working condition criterion formed by the reference comparison quantity, wherein the method comprises the following steps:
under the condition that the minimum value of the circulating frame meets the inrush current identification working condition criterion, opening differential protection for a non-inrush current working condition;
under the condition that the minimum value of the circulating frame does not meet the inrush current identification working condition criterion, the differential protection is not opened for the inrush current working condition.
Specifically, as known from the mechanism of transformer magnetizing inrush current generation, the essence of the magnetizing inrush current waveform generation is that the transformer generates reverse magnetic flux to counteract the magnetic flux generated by the instantaneously applied power supply during no-load closing, and the transformer core is saturated under the action of the reverse magnetic flux, so that a large exciting current is generated. This magnetizing inrush current has a larger "collapse" in waveform characteristics than the waveform of the internal fault of the transformer. The invention captures the characteristic by utilizing a mathematical processing method, thereby realizing the identification of the exciting surge.
(1) Acquisition of sample value variation
The method can take the sampling rate of mHz, namely, m/50 points of sampling per cycle. Taking a sampling rate of 1200Hz, i.e. 24 samples per cycle as an example.
i Σi For differential current sampling values, a specific calculation formula is as follows:
collecting the high voltage side of the transformer at t i Three-phase current i at time Hi And low pressure side at t i Three-phase current i at time Li Wherein i is a natural number;
according to the high-side three-phase current i Hi And low-side three-phase current i Li Calculating t i Three-phase differential current sampling value i of time transformer Σi ；
i Σi ＝i Hi +i Li *N T (1)
N in the above T Is the transformation ratio of the transformer.
δi Σi The specific calculation method for the variation of the differential current sampling value comprises the following steps:
differential current sampling value i at present moment Σi Subtracting the sampling value i of the cycle before the fault Σ(i-) I.e.
δi Σi ＝i Σi -i Σ(i-) (2)
(2) Benchmark comparative quantity extraction 24 k
Using the variation delta i of the differential current sampling value obtained in step (1) Σi The absolute value of the variation of the differential current sampling value in 1 cycle before the current sampling time is accumulated and summed to obtain the standard comparison quantity of the criterion, n k . Taking a 24-point cycle as an example, the absolute value of the variation of the differential current sampling value in 1 cycle is accumulated and summed to obtain the standard comparison quantity of the criterion, namely 24 k 。
(3) Close proximity cluster cycle detection 9 MIN
The δi obtained in the step (1) is then used Σi The differential value δdi is obtained by performing the following operation Σi
δdi Σi ＝δi Σi -δi Σi-1 (4)
The current sampling point and the first s sampling points are defined, and s+1 sampling points form a close-adjacent set. Taking s=8, a total of 9 sample points form a close-proximity set. For each sampling point in a certain sampling point close-proximity set, the following operation is performed:
(1) differential flow variation sampling value delta i Σi Differential delta di from differential flow variation sampling value Σi Summing and then obtaining an absolute value;
(2) the calculation results of (1) above are summed up for all 9 points within the immediate set (i.e., 7.5 ms).
It can be seen that for each sampling point there isIf the 24-point data of one week is regarded as one frame, the calculated data of all criteria do not exceed one frame, and the 24-point data of the current frame is limited. The present criterion requires to obtain 24 of the current frame kObviously there are 8 points +.>Exceeding the criteria of the current frame as shown in figure 2. In the figures, (1), (2) and (3) are the 1 st, 2 nd and 3 rd immediate neighbor sets, and so on. The 17 th immediate neighbor set starts the required calculation dataBeyond the current frame sample data.
To solve the problem that 8 points in one frame exceed the current frame data, the method is toCorrection to->
The specific method is to circularly supplement frame head data and frame tail data, so that 8 data of the current frame head are needed to be supplemented to the frame tail if 24 immediate sets of the current frame are to be calculated. That is, the 17 th immediate neighbor set starts using the 1 st sampling point of the current frame, the 18 th immediate neighbor set uses the 1 st and 2 nd sampling points of the current frame, the 19 th immediate neighbor set uses the 1 st, 2 nd and 3 rd sampling points … … of the current frame, and the 24 th immediate neighbor set uses the 1 st to 8 th sampling points of the current frame.
The immediate set of 24 points within the current frame is modified as follows:
the subscript n indicates the sequence number of 24 points within the current frame.
(1) When n= (k-15) -k, direct copying is performed without correction
(2) When n= (k-23) to (k-16), the data cycle correction is as follows:
after finishing the data correction of the 9-point immediate-neighbor set, the minimum value of the 9-point immediate-neighbor set can be taken, and the method is specifically expressed as follows:
inrush current identification open criterion (9 sampling points form a close-proximity set for example)
Wherein,
when the formula (8) is satisfied, the working condition is a non-inrush current working condition, and differential protection can be opened. And (3) judging the working condition as a surge current working condition when the formula (8) is not satisfied, and not opening differential protection.
As shown in FIG. 3, the simulation discrimination results of the internal turn-to-turn faults and the inrush current conditions are included in the graph. The method can effectively identify the turn-to-turn fault or the inrush current working condition of the transformer.
In addition, the implementation of the patent is carried out by taking the transformer air-drop excitation surge current in a certain practical project as an example, and the current waveforms measured by the three-phase sleeve CT at the net side and the valve side of the YD converter transformer are shown in fig. 4.
1) Acquisition of sample value variation
(1) Taking a sampling rate of 1200Hz, i.e. 24 samples per cycle as an example.
The differential current is calculated from sample point to sample point using equation (1). Wherein i is Hi The current is the current of A phase, B phase and C phase of the head end of the YD net side sleeve. i.e Li The current is the current of A phase, B phase and C phase of the head end of the YD valve side sleeve. Calculating to obtain three-phase differential current i Σi As shown in fig. 5.
(2) Calculating the differential current variation delta i of each phase by using the formula (2) for each sampling point differential current obtained in the step (1) Σi As shown in fig. 6.
2) Benchmark comparative quantity extraction 24 k
Using the formula (3) to change delta i of the differential current sampling value obtained in the step (1) Σi The absolute value of the variation of the differential current sampling value in one cycle before the current sampling time is accumulated and summed to obtain the standard comparison quantity of the criterion-24 k As shown in fig. 7.
3) Close proximity cluster cycle detection 9 MIN
The δi obtained in the step (1) is then used Σi The operation is carried out by utilizing the formula (4),obtaining the differential value delta di of the variation of the sampling value of the differential flow Σi 。
Obtaining a 9-point close-proximity set by using the formula (5) and the formula (6)And 9-point close-proximity set corresponding to 24 sampling points of one week after correction +.>
Then, the minimum value 9 in the immediate vicinity of the 9 points after 24 correction is obtained by using the formula (7) MIN . As shown in fig. 8.
4) Inrush current identification open criterion
24 obtained in the step (3) k And 9 obtained in the step (4) MIN And formula (8) performs inrush current identification. When the formula is not satisfied, the judgment result is a surge current; and judging that the fault exists when the formula is satisfied.
Because only the phase difference element B meets the action condition, the inrush current identification opening criterion only needs to pay attention to the phase B. The simulation result is shown in fig. 9 according to the criterion of the formula (8). As can be seen from fig. 9, equation (8) is not satisfied, i.e., the surge opening condition is not satisfied. And therefore is distinguished as a current surge rather than an internal fault.
Therefore, the invention can accurately and effectively identify the excitation surge current of the transformer through extracting the collapse characteristics of the differential current waveform. Therefore, misoperation of the transformer protection under the excitation surge working condition is avoided, and the safety of the transformer protection is improved.
Exemplary apparatus
Fig. 10 is a schematic structural diagram of a transformer inrush current identification device according to an exemplary embodiment of the present invention. As shown in fig. 10, the apparatus 1000 includes:
the first determining module 1010 is configured to determine, according to the collected high-voltage side three-phase current and low-voltage side three-phase current of the transformer on each cycle at the current moment, a variation of a differential current sampling value of each sampling point and a cycle before a fault;
the first calculating module 1020 is configured to calculate a reference comparison amount in the current cycle according to a variation of a differential current sampling value of each sampling point in the cycle;
a second calculation module 1030, configured to form each sampling point and a predetermined number of sampling points in the cycle into an immediately adjacent set, and calculate differential values of sampling points in all immediately adjacent sets;
a second determining module 1040, configured to add up the change amounts of the differential current sampling values of the sampling points in each adjacent set and the absolute values of the sum of the differential values, to determine a cycle frame of each adjacent set;
the third determining module 1050 is configured to select a minimum value of all immediately adjacent concentrated cycle frames, and determine an inrush current condition of the transformer according to an inrush current identification condition criterion formed by the reference comparison, where the inrush current condition is used to determine whether to open differential protection.
Optionally, each cycle includes 24 sampling points, and determining, according to the collected three-phase current of the transformer on the high-voltage side and the three-phase current of the transformer on the low-voltage side of each cycle, a variation of a differential current sampling value of each sampling point and a cycle before the fault in the cycle at the current moment includes:
collecting high-voltage side three-phase current and low-voltage side three-phase current of 24 sampling points of each cycle wave of a transformer;
determining the variation of differential current sampling value according to the differential current sampling value difference of high-voltage side three-phase current and low-voltage side three-phase current of 24 sampling points in the current time period and 24 sampling points in the previous fault period, wherein
i ∑i ＝i Hi +i Li *N T
δi ∑i ＝i ∑i -i ∑(i- )
In the formula, δi ∑i For the variation of the differential current sampling value, i ∑i I is the sampling value of differential current in the current cycle ∑(i-) I is the differential current sampling value of the previous cycle of the fault Hi At t i Three-phase current at high voltage side at moment, i Li At t i Low-side three-phase current at time, N T Is the transformation ratio of the transformer.
Optionally, according to the variation of the differential current sampling value of each sampling point in the cycle at the current moment, the calculation formula for calculating the reference comparison amount in the cycle is as follows:
of which, 24 k As a reference comparison quantity, δi ∑j And k is the number of the current sampling point for the variation of the differential current sampling value.
Optionally, each sampling point and the previous predetermined number of sampling points in the cycle are formed into an adjacent set, and the formula for calculating the differential value of each sampling point in all the adjacent sets is as follows:
δdi ∑i ＝δi ∑i -δi ∑i-1
wherein δdi Σi Is a differential value, δi ∑i Delta i is the variation of the differential current sampling value of the current sampling point ∑i-1 The differential current sampling value variation amount of the previous sampling point of the current sampling point.
Optionally, the pre-reserved number of sampling points is 8 sampling points, the immediately adjacent set includes 9 sampling points, and the differential current sampling value variation amounts of the sampling points in each immediately adjacent set and the absolute value of the sum of the differential values are respectively added together in a cumulative way, so that the calculation formula of the cyclic frame of each immediately adjacent set is determined as follows:
wherein,delta i is a cyclic frame of the immediate neighbor set ∑i For the variation of the differential current sampling value δdi ∑i Is the differential value of the variation of the differential current sampling value.
Optionally, the operation of selecting the minimum value of all immediately adjacent concentrated cyclic frames includes:
correcting the cyclic frames of the adjacent set;
and selecting a minimum value according to the corrected cyclic frames of all the adjacent sets, wherein the selection formula of the minimum value is as follows:
where k is the current sample point number.
Optionally, the operation of correcting the cyclic frame of the immediate neighbor set includes:
when n= (k-15) -k, direct copying is performed without correction
When n= (k-23) to (k-16), the data cycle correction is as follows:
wherein n represents the serial numbers of 24 sampling points in the current frame, i ∑n Is the three-phase differential current sampling value of the nth sampling point.
Optionally, the inrush current identification condition criteria are:
wherein,
and selecting the minimum value of all the immediately adjacent concentrated cycle frames, and determining the inrush current working condition of the transformer by using the inrush current identification working condition criterion formed by the reference comparison quantity, wherein the method comprises the following steps:
under the condition that the minimum value of the circulating frame meets the inrush current identification working condition criterion, opening differential protection for a non-inrush current working condition;
under the condition that the minimum value of the circulating frame does not meet the inrush current identification working condition criterion, the differential protection is not opened for the inrush current working condition.
Exemplary electronic device
Fig. 11 is a structure of an electronic device provided in an exemplary embodiment of the present invention. As shown in fig. 11, the electronic device 110 includes one or more processors 111 and a memory 112.
The processor 111 may be a Central Processing Unit (CPU) or other form of processing unit having data processing and/or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.
Memory 112 may include one or more computer program products that may include various forms of computer-readable storage media, such as volatile memory and/or non-volatile memory. The volatile memory may include, for example, random Access Memory (RAM) and/or cache memory (cache), and the like. The non-volatile memory may include, for example, read Only Memory (ROM), hard disk, flash memory, and the like. One or more computer program instructions may be stored on the computer readable storage medium that can be executed by the processor 111 to implement the methods of the software programs of the various embodiments of the present invention described above and/or other desired functions. In one example, the electronic device may further include: an input device 113 and an output device 114, which are interconnected by a bus system and/or other forms of connection mechanisms (not shown).
In addition, the input device 113 may also include, for example, a keyboard, a mouse, and the like.
The output device 114 can output various information to the outside. The output device 114 may include, for example, a display, speakers, a printer, and a communication network and remote output apparatus connected thereto, etc.
Of course, only some of the components of the electronic device relevant to the present invention are shown in fig. 11 for simplicity, components such as buses, input/output interfaces, and the like being omitted. In addition, the electronic device may include any other suitable components depending on the particular application.
Exemplary computer program product and computer readable storage Medium
In addition to the methods and apparatus described above, embodiments of the invention may also be a computer program product comprising computer program instructions which, when executed by a processor, cause the processor to perform steps in a method according to various embodiments of the invention described in the "exemplary methods" section of this specification.
The computer program product may write program code for performing operations of embodiments of the present invention in any combination of one or more programming languages, including an object oriented programming language such as Java, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computing device, partly on the user's device, as a stand-alone software package, partly on the user's computing device, partly on a remote computing device, or entirely on the remote computing device or server.
Furthermore, embodiments of the present invention may also be a computer-readable storage medium, having stored thereon computer program instructions which, when executed by a processor, cause the processor to perform the steps in a method of mining history change records according to various embodiments of the present invention described in the "exemplary methods" section above in this specification.
The computer readable storage medium may employ any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. The readable storage medium can include, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, or device, or a combination of any of the foregoing. More specific examples (a non-exhaustive list) of the readable storage medium would include the following: an electrical connection having one or more wires, a portable disk, a hard disk, random Access Memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
The basic principles of the present invention have been described above in connection with specific embodiments, however, it should be noted that the advantages, benefits, effects, etc. mentioned in the present invention are merely examples and not intended to be limiting, and these advantages, benefits, effects, etc. are not to be considered as essential to the various embodiments of the present invention. Furthermore, the specific details disclosed herein are for purposes of illustration and understanding only, and are not intended to be limiting, as the invention is not necessarily limited to practice with the above described specific details.
In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different manner from other embodiments, so that the same or similar parts between the embodiments are mutually referred to. For system embodiments, the description is relatively simple as it essentially corresponds to method embodiments, and reference should be made to the description of method embodiments for relevant points.
The block diagrams of the devices, systems, apparatuses, systems according to the present invention are merely illustrative examples and are not intended to require or imply that the connections, arrangements, configurations must be made in the manner shown in the block diagrams. As will be appreciated by one of skill in the art, the devices, systems, apparatuses, systems may be connected, arranged, configured in any manner. Words such as "including," "comprising," "having," and the like are words of openness and mean "including but not limited to," and are used interchangeably therewith. The terms "or" and "as used herein refer to and are used interchangeably with the term" and/or "unless the context clearly indicates otherwise. The term "such as" as used herein refers to, and is used interchangeably with, the phrase "such as, but not limited to.
The method and system of the present invention may be implemented in a number of ways. For example, the methods and systems of the present invention may be implemented by software, hardware, firmware, or any combination of software, hardware, firmware. The above-described sequence of steps for the method is for illustration only, and the steps of the method of the present invention are not limited to the sequence specifically described above unless specifically stated otherwise. Furthermore, in some embodiments, the present invention may also be embodied as programs recorded in a recording medium, the programs including machine-readable instructions for implementing the methods according to the present invention. Thus, the present invention also covers a recording medium storing a program for executing the method according to the present invention.
It is also noted that in the systems, devices and methods of the present invention, components or steps may be disassembled and/or assembled. Such decomposition and/or recombination should be considered as equivalent aspects of the present invention. The previous description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
The foregoing description has been presented for purposes of illustration and description. Furthermore, this description is not intended to limit embodiments of the invention to the form disclosed herein. Although a number of example aspects and embodiments have been discussed above, a person of ordinary skill in the art will recognize certain variations, modifications, alterations, additions, and subcombinations thereof.
Claims (9)
1. A method for identifying inrush current of a transformer, comprising:
according to the collected three-phase current of the transformer at the high-voltage side and the three-phase current of the transformer at the low-voltage side of each weekly wave, determining the variation of a differential current sampling value of each sampling point and the cycle before the fault in the cycle at the current moment;
calculating a reference comparison amount in the cycle according to the variation of the differential current sampling value of each sampling point in the cycle at the current moment;
forming an adjacent set by each sampling point and the preset number of sampling points in the cycle, and calculating the differential value of each sampling point in all the adjacent sets;
respectively carrying out accumulated addition on the absolute value of the sum of the variation of the differential current sampling value and the differential value of each sampling point in each adjacent set to determine a cycle frame of each adjacent set;
selecting the minimum value of the circulating frames in all the close-adjacent sets, and determining the inrush current working condition of the transformer by using an inrush current identification working condition criterion formed by the reference comparison quantity, wherein the inrush current working condition is used for determining whether differential protection is opened or not; wherein,
according to the variation of the differential current sampling value of each sampling point in the cycle at the current moment, the calculation formula for calculating the reference comparison quantity in the cycle is as follows:
of which, 24 k As a reference comparison quantity, δi Σi The variation of the differential current sampling value is represented by k, which is the number of the current sampling point;
the inrush current identification working condition criteria are as follows:
wherein,
and selecting the minimum value of the circulating frames in all the close-adjacent sets, and determining the inrush current working condition of the transformer by using the inrush current identification working condition criterion formed by the reference comparison quantity, wherein the method comprises the following steps:
under the condition that the minimum value of the circulating frame meets the inrush current identification working condition criterion, opening differential protection for a non-inrush current working condition;
and under the condition that the minimum value of the circulating frame does not meet the inrush current identification working condition criterion, the differential protection is not opened for an inrush current working condition.
2. The method of claim 1, wherein each cycle comprises 24 sampling points, and wherein determining the differential current sample value change for each sampling point and the cycle prior to the fault in the cycle at the present time based on the collected high side three-phase current and the low side three-phase current of the transformer in each cycle comprises:
collecting the high-voltage side three-phase current and the low-voltage side three-phase current of 24 sampling points of each wave of the transformer;
determining the variation of the differential current sampling value according to the differential current sampling value difference between the high-voltage side three-phase current and the low-voltage side three-phase current of 24 sampling points in the current time period and 24 sampling points in the previous fault period, wherein
i Σi ＝i Hi +i Li *N T
δi Σi ＝i Σi -i Σ(i-)
In the formula, δi Σi For the variation of the differential current sampling value, i Σi I is the sampling value of differential current in the current cycle Σ(i-) I is the differential current sampling value of the previous cycle of the fault Hi At t i Three-phase current at high voltage side at moment, i Li At t i Low-side three-phase current at time, N T Is the transformation ratio of the transformer.
3. The method of claim 1 wherein each sample point and a predetermined number of preceding sample points within the cycle are grouped into an immediate vicinity, and wherein the formula for calculating the differential value for each sample point within all of said immediate vicinity is:
δdi Σi ＝δi Σi -δi Σi-1
wherein δdi ∑i Is a differential value, δi ∑i Delta i is the variation of the differential current sampling value of the current sampling point ∑i-1 The differential current sampling value variation amount of the previous sampling point of the current sampling point.
4. The method of claim 1, wherein the pre-reserved number of sampling points is 8 sampling points, the immediate neighboring set includes 9 sampling points, and the differential current sampling value variation amounts of the sampling points in each immediate neighboring set and the absolute value of the sum of the differential values are respectively added together in a cumulative manner, and a calculation formula for determining the cyclic frame of each immediate neighboring set is as follows:
wherein,delta i is a cyclic frame of the immediate neighbor set ∑i For the variation of the differential current sampling value δdi ∑i Is the differential value of the variation of the differential current sampling value.
5. The method of claim 4, wherein selecting the minimum of all of the cyclic frames in the immediate vicinity comprises:
correcting the cyclic frames of the immediate neighbor set;
and selecting a minimum value according to the corrected circulating frames of all the adjacent sets, wherein the selection formula of the minimum value is as follows:
where k is the current sample point number.
6. The method of claim 5, wherein modifying the cyclic frames of the immediate neighbor set comprises:
when n= (k-15) -k, direct copying is performed without correction
When n= (k-23) to (k-16), the data cycle correction is as follows:
wherein n represents the serial numbers of 24 sampling points in the current frame, i ∑n Is the three-phase differential current sampling value of the nth sampling point.
7. A transformer inrush current identification device, comprising:
the first determining module is used for determining the variation of the differential current sampling value of each sampling point and the cycle before the fault in the cycle at the current moment according to the collected high-voltage side three-phase current and low-voltage side three-phase current of the transformer in the cycle;
the first calculation module is used for calculating the reference comparison quantity in the current time according to the variation quantity of the differential current sampling value of each sampling point in the cycle;
the second calculation module is used for forming an adjacent set by each sampling point and the preset number of sampling points in the cycle, and calculating the differential value of each sampling point in all the adjacent set;
the second determining module is used for respectively carrying out cumulative addition on the absolute value of the sum of the variation of the differential current sampling value and the differential value of each sampling point in each adjacent set to determine the cycle frame of each adjacent set;
the third determining module is used for selecting the minimum value of the circulating frames in all the close-adjacent sets, and determining the inrush current working condition of the transformer by using the inrush current identification working condition criterion formed by the reference comparison quantity, wherein the inrush current working condition is used for determining whether differential protection is opened or not; wherein,
according to the variation of the differential current sampling value of each sampling point in the cycle at the current moment, the calculation formula for calculating the reference comparison quantity in the cycle is as follows:
of which, 24 k As a reference comparison quantity, δi Σi The variation of the differential current sampling value is represented by k, which is the number of the current sampling point;
the inrush current identification working condition criteria are as follows:
wherein,
and selecting the minimum value of the circulating frames in all the close-adjacent sets, and determining the inrush current working condition of the transformer by using the inrush current identification working condition criterion formed by the reference comparison quantity, wherein the method comprises the following steps:
under the condition that the minimum value of the circulating frame meets the inrush current identification working condition criterion, opening differential protection for a non-inrush current working condition;
and under the condition that the minimum value of the circulating frame does not meet the inrush current identification working condition criterion, the differential protection is not opened for an inrush current working condition.
8. A computer readable storage medium, characterized in that the storage medium stores a computer program for executing the method of any of the preceding claims 1-6.
9. An electronic device, the electronic device comprising:
a processor;
a memory for storing the processor-executable instructions;
the processor is configured to read the executable instructions from the memory and execute the instructions to implement the method of any of the preceding claims 1-6.
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