CN116298580A - Transformer inrush current identification method and system based on waveform deviation and interruption characteristics - Google Patents
Transformer inrush current identification method and system based on waveform deviation and interruption characteristics Download PDFInfo
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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- G—PHYSICS
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
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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
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Abstract
The invention discloses a transformer inrush current identification method and system based on waveform deviation and interruption characteristics. Wherein the method comprises the following steps: collecting high-voltage side three-phase current
And low-side three-phase current
According to the collected high-voltage side three-phase current
And low-side three-phase powerFlow of
Calculating t j Three-phase differential current sampling value of time transformer
Sampling value waveform according to differential current
Determining excitation surge current identification based on waveform asymmetry offset characteristics; sampling value waveform according to differential current
Determining excitation surge current identification based on waveform discontinuity characteristics; determining the square wave index eta according to the excitation surge identification based on the waveform asymmetry deviation characteristic and the excitation surge identification based on the waveform discontinuity characteristic<1 or waveform discontinuity index lambda<1, identified as a current surge waveform.
Description
Technical Field
The invention relates to the technical field of power system protection and control, in particular to a transformer inrush current identification method and system based on waveform deviation and interruption characteristics.
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, along with the change of parameters such as capacity, remanence level and the like of the ferromagnetic material of the transformer, exciting inrush current working conditions with the second harmonic content less than 15% appear repeatedly in actual engineering, and the exciting inrush current working conditions are difficult to identify.
Disclosure of Invention
According to the invention, a transformer inrush current identification method and a system based on waveform deviation and interruption characteristics are provided, so that the technical problem that the excitation inrush current working condition with the second harmonic content less than 15% is difficult to identify in actual engineering is solved along with the change of parameters such as the ferromagnetic material, the capacity, the remanence level and the like of the transformer.
According to a first aspect of the present invention, there is provided a transformer inrush current identification method based on waveform offset and discontinuity characteristics, comprising:
collecting high-voltage side three-phase current
And low-side three-phase current->
According to the collected high-voltage side three-phase current
And low-side three-phase current->
Calculating t j Three-phase differential current sampling value of time transformer +.>
Sampling value waveform according to differential current
Determining excitation surge current identification based on waveform asymmetry offset characteristics;
sampling value waveform according to differential current
Determining excitation surge current identification based on waveform discontinuity characteristics;
and determining that the excitation surge based on the waveform asymmetry deviation characteristic and the excitation surge based on the waveform discontinuity characteristic are recognized as a surge waveform when the square wave index eta <1 or the waveform discontinuity index lambda < 1.
Optionally, collecting high-side three-phase current
And low-side three-phase current->
Comprising the following steps:
collecting the high-voltage side of the converter transformer at t j Three-phase current at time
And low pressure side at t j Three-phase current at time
Wherein (1)>
A, B, C three phases, t, of a converter transformer j J is a natural number for the current sampling instant.
Optionally, according to the collected high-side three-phase current
And low-side three-phase current->
Calculating t j Three-phase differential current sampling value of time transformer +.>
Comprising the following steps:
calculating t according to the following formula j Three-phase differential current sampling value of time transformer
Where ratio is the transformation ratio of the transformer.
Optionally, determining the excitation surge current identification based on the waveform asymmetry deviation feature according to the sampling value waveform of the differential current includes:
waveform of sampling value of differential current
Shaping into square wave +.>
Setting shaping threshold constant value i set ，
When in use, let->
Time, order
When in use, let->
(Continuous)
The pulse consisting of the sampling points of (a) is called positive pulse; continuous->
The pulse consisting of the sampling points of (a) is called a negative pulse; />
For no pulse, the number of sampling points in the pulse is called pulse width and is denoted by N;
when the differential flow waveform is positive and negative symmetrical, the square wave
A symmetrical square wave pulse sequence with positive and negative phases, when the differential flow waveform is shifted, +.>
Appears as a single sided square wave pulse train biased to one side,
p represents the polarity of the pulse, p=1 in the positive pulse and p= -1 in the negative pulse;
assuming that the current sampling point is located at the ith pulse, p i Representing the polarity of the pulse, p i-1 Representing the polarity of the previous adjacent pulse, at the same time N i Representing the number of sampling points of the ith pulse where the current sampling is located, namely, stopping the pulse width to the current sampling point, N i-1 Representing the number of samples in the previous adjacent pulse, i.e. the pulse width;
the pulse has the dual properties of polarity and width, and the square wave index eta is obtained by calculating the two immediately adjacent pulses:
when eta >1, reflect
Positive and negative symmetry, namely non-excitation surge current waveform characteristics; otherwise, if eta is less than 1, reflecting +.>
Asymmetric offset, i.e., excitation surge waveform characteristics.
Alternatively, the waveform of the sampled value according to the differential current
Determining excitation surge current identification based on waveform discontinuity characteristics, comprising:
for differential current
Processing the sampling points to obtain a point differential filtering result di diffΦ The calculation formula is as follows:
di diffΦ (k)＝i diffΦ (k)-i diffΦ (k-1)
in the above formula, k represents the kth sampling point of the differential current, and the differential operation result of the differential current sampling value is obtained through the operation of the above formula;
differential sampling value di using differential currents of each phase diffΦ (k) The following calculation was performed to obtain the waveform discontinuity index λ:
when lambda is more than 1, the waveform is identified as uninterrupted characteristic, namely non-excitation surge waveform characteristic; when λ <1, the waveform is identified as having a discontinuous characteristic, i.e., having a surge waveform characteristic.
According to another aspect of the present invention, there is also provided a transformer inrush current identification system based on waveform offset and discontinuity characteristics, including:
the three-phase current collecting module is used for collecting high-voltage side three-phase current and low-voltage side three-phase current;
the differential current sampling value calculating module is used for calculating t according to the collected high-voltage side three-phase current and low-voltage side three-phase current j Three-phase differential current sampling values of the transformer at the moment;
the waveform deviation characteristic inrush current identification module is used for determining excitation inrush current identification based on waveform asymmetry deviation characteristics according to the sampling value waveform of the differential current;
the waveform interruption characteristic inrush current identification module is used for determining excitation inrush current identification based on waveform interruption characteristics according to the sampling value waveform of the differential current;
and the inrush current identification waveform module is used for determining to identify an inrush current waveform when the square wave index eta <1 or the waveform break index lambda <1 according to the excitation inrush current identification based on the waveform asymmetry deviation characteristic and the excitation inrush current identification based on the waveform break characteristic.
Optionally, the collecting three-phase current module includes:
the collecting three-phase current sub-module is used for collecting the high-voltage side of the converter transformer at t j Three-phase current at time
And low pressure side at t j Three-phase current->
Wherein (1)>
A, B, C three phases, t, of a converter transformer j J is a natural number for the current sampling instant.
Optionally, the differential current sampling module includes:
calculating t according to the following formula j Three-phase differential current sampling value of time transformer
Where ratio is the transformation ratio of the transformer.
Optionally, determining the waveform offset characteristic inrush current identification module includes:
a waveform shaping sub-module for shaping sampling value waveform of differential current
Shaping into square wave +.>
Setting shaping threshold constant value i set ，
When in use, let->
Time, order
When in use, let->
(Continuous)
The pulse consisting of the sampling points of (a) is called positive pulse; continuous->
The pulse consisting of the sampling points of (a) is called a negative pulse; />
For no pulse, the number of sampling points in the pulse is called pulse width and is denoted by N;
when the differential flow waveform is positive and negative symmetrical, the square wave
A symmetrical square wave pulse sequence with positive and negative phases, when the differential flow waveform is shifted, +.>
Appears as a single sided square wave pulse train biased to one side,
p represents the polarity of the pulse, p=1 in the positive pulse and p= -1 in the negative pulse;
assuming that the current sampling point is located at the ith pulse, p i Representing the polarity of the pulse, p i-1 Representing the polarity of the previous adjacent pulse, at the same time N i Representing the number of sampling points of the ith pulse where the current sampling is located, namely, stopping the pulse width to the current sampling point, N i-1 Representing the number of samples in the previous adjacent pulse, i.e. the pulse width;
the square wave index determination submodule is used for obtaining square wave index eta by calculating two immediately adjacent pulses, wherein the square wave index submodule is used for pulse having dual properties of polarity and width:
when eta >1, reflect
Positive and negative symmetry, namely non-excitation surge current waveform characteristics; otherwise, if eta is less than 1, reflecting +.>
Asymmetric offset, i.e., excitation surge waveform characteristics.
Optionally, determining the waveform discontinuity characteristic inrush current identification module includes:
obtaining a differential filtering result submodule for differential current
Processing the sampling points to obtain a point differential filtering result di diffΦ The calculation formula is as follows:
di diffΦ (k)＝i diffΦ (k)-i diffΦ (k-1)
in the above formula, k represents the kth sampling point of the differential current, and the differential operation result of the differential current sampling value is obtained through the operation of the above formula;
a waveform interruption index sub-module is obtained for utilizing the differential sampling value di of the differential current of each phase diffΦ (k) The following calculation was performed to obtain the waveform discontinuity index λ:
when lambda is more than 1, the waveform is identified as uninterrupted characteristic, namely non-excitation surge waveform characteristic; when λ <1, the waveform is identified as having a discontinuous characteristic, i.e., having a surge waveform characteristic.
Therefore, the characteristics of the excitation surge waveform, namely asymmetry (offset) and discontinuity, are fully utilized, and the characteristics are extracted by an effective means, so that the identification of the excitation surge is realized. And further can be applied to differential protection to realize blocking of the inrush current. Thus, misoperation of the differential protection in the occurrence of exciting inrush current is avoided, and the overall performance 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 diagram of a transformer inrush current identification method based on waveform offset and discontinuity characteristics according to the present embodiment;
fig. 2 is a schematic diagram illustrating waveform discontinuity feature recognition according to the present embodiment;
fig. 3 is a schematic diagram of the maximum phase differential current of the transformer empty-charge surge waveform according to the present embodiment;
fig. 4 is a schematic diagram of a square wave pulse after shaping the maximum phase difference flow of the transformer empty charge surge waveform according to the present embodiment;
fig. 5 is a schematic diagram of an η value obtained by calculation of a transformer air-charge inrush current waveform according to the present embodiment;
fig. 6 is a schematic diagram of a graph of a maximum phase difference current of a transformer empty-charge surge waveform according to the present embodiment after a point differential filtering;
fig. 7 is a schematic diagram of a lambda value obtained by calculating a transformer empty charge surge waveform according to the present embodiment;
fig. 8 is a schematic diagram of the maximum phase differential current of the transformer with inter-turn short circuit fault in the internal winding according to the present embodiment;
fig. 9 is a schematic diagram of a square wave pulse after shaping the maximum phase difference flow of the inter-turn short circuit fault of the internal winding of the transformer according to the present embodiment;
fig. 10 is a schematic diagram of a calculated η value of an inter-turn short circuit fault of an internal winding of a transformer according to the present embodiment;
fig. 11 is a schematic diagram of a graph of a maximum phase difference current of an inter-turn short circuit fault of an internal winding of a transformer according to the present embodiment after a differential filtering;
fig. 12 is a schematic diagram of a calculated lambda value of an inter-turn short circuit fault of an internal winding of a transformer according to the present embodiment;
fig. 13 is a schematic diagram of a transformer inrush current identification system based on waveform offset and discontinuity characteristics according to the present embodiment.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the examples described herein, which are provided to fully and completely disclose the present invention and fully convey the scope of the invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like elements/components are referred to by like reference numerals.
Unless otherwise indicated, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, it will be understood that terms defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
According to a first aspect of the present invention there is provided a method 100, as shown with reference to fig. 1, the method 100 comprising:
s101, collecting high-voltage side three-phase current
And low-side three-phase current->
S102, according to the collected high-voltage side three-phase current
And low-side three-phase current->
Calculating t j Three-phase differential current sampling value of time transformer +.>
S103, sampling value waveform according to differential current
Determining excitation surge current identification based on waveform asymmetry offset characteristics;
s104, sampling value waveform according to differential current
Determining excitation surge current identification based on waveform discontinuity characteristics;
and S105, determining that the excitation surge based on the waveform asymmetry deviation characteristic and the excitation surge based on the waveform discontinuity characteristic are recognized as a surge waveform when the square wave index eta <1 or the waveform discontinuity index lambda < 1.
Specifically, the high-voltage side of the converter transformer is collected at t j Three-phase current at time
And three-phase current +.>
Wherein (1)>
A, B, C three phases, t, of a converter transformer j J is a natural number for the current sampling time;
according to the high-voltage side three-phase current
And low-side three-phase current->
Calculating three-phase differential current sampling value +.>
In the above formula, ratio is the transformation ratio of the transformer.
(1) Excitation surge current identification based on waveform asymmetry offset feature
First, the sampling value waveform of the differential current is obtained
Shaping into square wave +.>
Setting shaping threshold constant value i set ，
When in use, let->
Time, order
When in use, let->
(Continuous)
The pulse consisting of the sampling points of (a) is called positive pulse; continuous->
The pulse consisting of the sampling points of (a) is called a negative pulse; />
Is pulse-free. The number of samples in a pulse is referred to as the pulse width and is denoted by N.
When the differential flow waveform is positive and negative symmetrical, the square wave
And the pulse sequence is a symmetrical square wave pulse sequence with alternately positive and negative. When the differential stream waveform is shifted, < >>
Appears as a single sided square wave pulse train biased to one side.
p represents the polarity of the pulse, p=1 in the positive pulse and p= -1 in the negative pulse.
Assuming that the current sampling point is located at the ith pulse, p i Representing the polarity of the pulse, p i-1 Representing the polarity of the previous adjacent pulse. At the same time N i Represents the number of sampling points (pulse width up to the current sampling point) of the ith pulse where the current sampling is located, N i-1 Representing the number of samples (pulse width) in the previous adjacent pulse.
The pulse has the dual properties of polarity and width, and the square wave index eta is obtained by calculating the two immediately adjacent pulses:
when eta >1, reflect
Positive and negative symmetry, namely non-excitation surge current waveform characteristics; otherwise, if eta is less than 1, reflecting +.>
Asymmetric offset, i.e., excitation surge waveform characteristics.
(2) Excitation surge current identification based on waveform discontinuity characteristics
First, to differential current
Processing the sampling points to obtain a point differential filtering result di diffΦ . The specific calculation formula is as follows:
di diffΦ (k)＝i diffΦ (k)-i diffΦ (k-1)
in the above equation, k represents the kth sampling point of the differential current. The differential operation result of the differential current sampling value is obtained through the above operation.
Then, differential sampling value di of differential current of each phase is used diffΦ (k) The following calculation was performed to obtain the waveform discontinuity index λ:
referring to fig. 2, the left integration interval is from the current time to the first 5ms (the sampling rate of 24 points per week is equivalent to 6 sampling points, and the sampling rate of 32 points per week is equivalent to 8 points); the right is the maximum value of the differential absolute value of the differential sampling value of the difference stream in the time period from the starting to the current time minus 5ms time.
When lambda is more than 1, the waveform is identified as uninterrupted characteristic, namely non-excitation surge waveform characteristic; when λ <1, the waveform is identified as having a discontinuous characteristic, i.e., having a surge waveform characteristic.
When applied, the lambda value may be stretched for 20ms and then returned once it has been satisfied to less than 1.
(3) Comprehensive discrimination
And combining the results of the symmetry and discontinuity characteristic discrimination of the differential current waveform.
When the square wave index eta <1 or the waveform discontinuity index lambda <1, the surge waveform is identified.
Example 1
The implementation of the patent is carried out by taking a transformer empty charging surge waveform as an example in a certain practical engineering.
First, the maximum phase difference current is sampled. The waveforms of the sampled values of the differential currents of the respective phases are shown in fig. 3.
Secondly, square wave pulse shaping is carried out on the obtained differential stream sampling value waveform. Resulting in square wave pulses as shown in fig. 4.
Then, the square wave index η is calculated for the square wave pulse by the expression (1). The η value curve shown in fig. 3 is obtained. And using the relation between the value of eta and 1, the result in FIG. 5 shows that the condition of eta <1 is satisfied.
Then, a point difference filtering process is performed on the maximum phase difference stream, and a curve as shown in fig. 6 is obtained.
Then, the waveform interruption index λ is obtained by calculating the differential value using the formula (2). And waveform characteristics are identified by using the relation between lambda value and 1, and the result of fig. 7 shows that the condition lambda <1 is satisfied.
And finally, judging the working condition corresponding to the current waveform as the working condition of the inrush current waveform by utilizing the judging results of eta <1 and lambda < 1.
Example two
The implementation of the patent is carried out by taking the turn-to-turn short circuit fault of the internal winding of the transformer in a certain practical project as an example.
First, the maximum phase difference current is sampled. The waveforms of the sampled values of the differential currents of the respective phases are shown in fig. 8.
Secondly, square wave pulse shaping is carried out on the obtained differential stream sampling value waveform. Resulting in square wave pulses as shown in fig. 9.
Then, the square wave index η is calculated for the square wave pulse by the expression (1). An η value curve as shown in fig. 8 is obtained. The result in FIG. 10 shows that the condition of η >1 is satisfied by using the relationship between the value of η and 1.
Then, a point difference filter process is performed on the maximum phase difference stream, resulting in a curve as shown in fig. 11.
Then, the waveform interruption index λ is obtained by calculating the differential value using the formula (2). And waveform characteristics are identified by using the relation between lambda value and 1, and it is found from the result of fig. 12 that the condition lambda >1 is satisfied.
And finally, judging the working condition corresponding to the current waveform to be a non-inrush current waveform working condition by utilizing the judging results of eta & gt 1 and lambda & gt 1.
Therefore, the characteristics of the excitation surge waveform, namely asymmetry (offset) and discontinuity, are fully utilized, and the characteristics are extracted by an effective means, so that the identification of the excitation surge is realized. And further can be applied to differential protection to realize blocking of the inrush current. Thus, misoperation of the differential protection in the occurrence of exciting inrush current is avoided, and the overall performance of the transformer protection is improved.
Optionally, collecting high-side three-phase current
And low-side three-phase current->
Comprising the following steps:
collecting the high-voltage side of the converter transformer at t j Three-phase current at time
And low pressure side at t j Three-phase current at time
Wherein (1)>
A, B, C three phases, t, of a converter transformer j J is a natural number for the current sampling instant.
Optionally, according to the collected high-side three-phase current
And low-side three-phase current->
Calculating t j Three-phase differential current sampling value of time transformer +.>
Comprising the following steps:
calculating t according to the following formula j Three-phase differential current sampling value of time transformer
Where ratio is the transformation ratio of the transformer.
Optionally, determining the excitation surge current identification based on the waveform asymmetry deviation feature according to the sampling value waveform of the differential current includes:
waveform of sampling value of differential current
Shaping into square wave +.>
Setting shaping threshold constant value i set ，
When in use, let->
Time, order
When in use, let->
(Continuous)
The pulse consisting of the sampling points of (a) is called positive pulse; continuous->
The pulse consisting of the sampling points of (a) is called a negative pulse; />
Is pulse-free, sampling point in pulseThe number is called pulse width and is denoted by N;
when the differential flow waveform is positive and negative symmetrical, the square wave
A symmetrical square wave pulse sequence with positive and negative phases, when the differential flow waveform is shifted, +.>
Appears as a single sided square wave pulse train biased to one side,
p represents the polarity of the pulse, p=1 in the positive pulse and p= -1 in the negative pulse;
assuming that the current sampling point is located at the ith pulse, p i Representing the polarity of the pulse, p i-1 Representing the polarity of the previous adjacent pulse, at the same time N i Representing the number of sampling points of the ith pulse where the current sampling is located, namely, stopping the pulse width to the current sampling point, N i-1 Representing the number of samples in the previous adjacent pulse, i.e. the pulse width;
the pulse has the dual properties of polarity and width, and the square wave index eta is obtained by calculating the two immediately adjacent pulses:
when eta >1, reflect
Positive and negative symmetry, namely non-excitation surge current waveform characteristics; otherwise, if eta is less than 1, reflecting +.>
Asymmetric offset, i.e., excitation surge waveform characteristics.
Alternatively, the waveform of the sampled value according to the differential current
Determining excitation surge current identification based on waveform discontinuity characteristics, comprising:
for differential current
Processing the sampling points to obtain a point differential filtering result di diffΦ The calculation formula is as follows:
di diffΦ (k)＝i diffΦ (k)-i diffΦ (k-1)
in the above formula, k represents the kth sampling point of the differential current, and the differential operation result of the differential current sampling value is obtained through the operation of the above formula;
differential sampling value di using differential currents of each phase diffΦ (k) The following calculation was performed to obtain the waveform discontinuity index λ:
when lambda is more than 1, the waveform is identified as uninterrupted characteristic, namely non-excitation surge waveform characteristic; when λ <1, the waveform is identified as having a discontinuous characteristic, i.e., having a surge waveform characteristic.
Therefore, the characteristics of the excitation surge waveform, namely asymmetry (offset) and discontinuity, are fully utilized, and the characteristics are extracted by an effective means, so that the identification of the excitation surge is realized. And further can be applied to differential protection to realize blocking of the inrush current. Thus, misoperation of the differential protection in the occurrence of exciting inrush current is avoided, and the overall performance of the transformer protection is improved.
In accordance with another aspect of the present invention, there is also provided a transformer inrush current identification system 1300 based on waveform offset and discontinuity characteristics, as shown with reference to fig. 13, the system 1300 comprising:
the three-phase current collection module 1310 is used for collecting three-phase current of a high-voltage side and three-phase current of a low-voltage side;
calculating differential currentSampling value module 1320 for calculating t based on the collected high-side three-phase current and low-side three-phase current j Three-phase differential current sampling values of the transformer at the moment;
a waveform-shifting-feature-determining inrush current identification module 1330 for determining an excitation inrush current identification based on a waveform asymmetry-shifting feature from a sampling value waveform of the differential current;
a waveform discontinuity characteristic inrush current identification module 1340 for determining an excitation inrush current identification based on waveform discontinuity characteristics from the waveform of the sampling value of the differential current;
the inrush current identification waveform module 1350 is configured to determine, according to the inrush current identification based on the waveform asymmetry deviation feature and the inrush current identification based on the waveform discontinuity feature, to identify as an inrush current waveform when the square wave index η <1 or the waveform discontinuity index λ < 1.
Optionally, the collecting three-phase current module includes:
the collecting three-phase current sub-module is used for collecting the high-voltage side of the converter transformer at t j Three-phase current at time
And low pressure side at t j Three-phase current->
Wherein (1)>
A, B, C three phases, t, of a converter transformer j J is a natural number for the current sampling instant.
Optionally, the differential current sampling module includes:
calculating t according to the following formula j Three-phase differential current sampling value of time transformer
Where ratio is the transformation ratio of the transformer.
Optionally, determining the waveform offset characteristic inrush current identification module includes:
a waveform shaping sub-module for shaping sampling value waveform of differential current
Shaping into square wave +.>
Setting shaping threshold constant value i set ，
When in use, let->
Time, order
When in use, let->
(Continuous)
The pulse consisting of the sampling points of (a) is called positive pulse; continuous->
The pulse consisting of the sampling points of (a) is called a negative pulse; />
For no pulse, the number of sampling points in the pulse is called pulse width and is denoted by N;
when the differential flow waveform is positive and negative symmetrical, the square wave
A symmetrical square wave pulse sequence with positive and negative phases, when the differential flow waveform is shifted, +.>
Appears as a single sided square wave pulse train biased to one side,
p represents the polarity of the pulse, p=1 in the positive pulse and p= -1 in the negative pulse;
assuming that the current sampling point is located at the ith pulse, p i Representing the polarity of the pulse, p i-1 Representing the polarity of the previous adjacent pulse, at the same time N i Representing the number of sampling points of the ith pulse where the current sampling is located, namely, stopping the pulse width to the current sampling point, N i-1 Representing the number of samples in the previous adjacent pulse, i.e. the pulse width;
the square wave index determination submodule is used for obtaining square wave index eta by calculating two immediately adjacent pulses, wherein the square wave index submodule is used for pulse having dual properties of polarity and width:
when eta >1, reflect
Positive and negative symmetry, namely non-excitation surge current waveform characteristics; otherwise, if eta is less than 1, reflecting +.>
Asymmetric offset, i.e., excitation surge waveform characteristics.
Optionally, determining the waveform discontinuity characteristic inrush current identification module includes:
obtaining a differential filtering result submodule for differential current
Processing the sampling points to obtain a point differential filtering result di diffΦ The calculation formula is as follows:
di diffΦ (k)＝i diffΦ （k)-i diffΦ (k-1)
in the above formula, k represents the kth sampling point of the differential current, and the differential operation result of the differential current sampling value is obtained through the operation of the above formula;
a waveform interruption index sub-module is obtained for utilizing the differential sampling value di of the differential current of each phase diffΦ (k) The following calculation was performed to obtain the waveform discontinuity index λ:
when lambda is more than 1, the waveform is identified as uninterrupted characteristic, namely non-excitation surge waveform characteristic; when λ <1, the waveform is identified as having a discontinuous characteristic, i.e., having a surge waveform characteristic.
In accordance with another aspect of the present invention, there is also provided a transformer inrush current identification system 1300 based on waveform offset and discontinuity characteristics, as shown with reference to fig. 13, the system 1300 comprising:
a transformer inrush current identification system 1300 based on waveform shifting and interruption features according to an embodiment of the present invention corresponds to a transformer inrush current identification method 100 based on waveform shifting and interruption features according to another embodiment of the present invention, and is not described herein.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. The solutions in the embodiments of the present application may be implemented in various computer languages, for example, object-oriented programming language Java, and an transliterated scripting language JavaScript, etc.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the spirit or scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims and the equivalents thereof, the present application is intended to cover such modifications and variations.
Claims (10)
1. A transformer inrush current identification method based on waveform deviation and interruption characteristics is characterized by comprising the following steps:
collecting high-voltage side three-phase current
And low-side three-phase current->
According to the collected high-voltage side three-phase current
And low-side three-phase current->
Calculating t j Three-phase differential current sampling value of time transformer +.>
Sampling value waveform according to differential current
Determining excitation surge current identification based on waveform asymmetry offset characteristics;
sampling value waveform according to differential current
Determining excitation surge current identification based on waveform discontinuity characteristics;
and determining that the excitation surge based on the waveform asymmetry deviation characteristic and the excitation surge based on the waveform discontinuity characteristic are recognized as a surge waveform when the square wave index eta <1 or the waveform discontinuity index lambda < 1.
2. The method of claim 1, wherein high side three phase current is collected
And low-side three-phase current->
Comprising the following steps:
collecting the high-voltage side of the converter transformer at t j Three-phase current at time
And low pressure side at t j Three-phase current at time
Wherein (1)>
A, B, C three phases, t, of a converter transformer j J is a natural number for the current sampling instant.
3. The method according to claim 1, wherein, based on the collected high-side three-phase current
And low-side three-phase current->
Calculating t j Three-phase differential current sampling value of time transformer +.>
Comprising the following steps:
calculating t according to the following formula j Three-phase differential current sampling value of time transformer
Where ratio is the transformation ratio of the transformer.
4. The method of claim 1, wherein determining the identification of the magnetizing inrush current based on the waveform asymmetry offset feature from the sampled value waveform of the differential current comprises:
waveform of sampling value of differential current
Shaping into square wave +.>
Setting shaping threshold constant value i set ，
When in use, let->
When in use, let->
When in use, let->
(Continuous)
The pulse consisting of the sampling points of (a) is called positive pulse; continuous->
The pulse consisting of the sampling points of (a) is called a negative pulse; />
For no pulse, the number of sampling points in the pulse is called pulse width and is denoted by N;
when the differential flow waveform is positive and negative symmetrical, the square wave
A symmetrical square wave pulse sequence with positive and negative phases, when the differential flow waveform is shifted, +.>
Appears as a single sided square wave pulse train biased to one side,
p represents the polarity of the pulse, p=1 in the positive pulse and p=1 in the negative pulse;
assuming that the current sampling point is located at the ith pulse, p i Representing the polarity of the pulse, p i-1 Representing the polarity of the previous adjacent pulse, at the same time N i Representing the number of sampling points of the ith pulse where the current sampling is located, namely, stopping the pulse width to the current sampling point, N i-1 Representing the number of samples in the previous adjacent pulse, i.e. the pulse width;
the pulse has the dual properties of polarity and width, and the square wave index eta is obtained by calculating the two immediately adjacent pulses:
When eta >1, reflect
Positive and negative symmetry, namely non-excitation surge current waveform characteristics; otherwise, if eta is less than 1, reflecting +.>
Asymmetric offset, i.e., excitation surge waveform characteristics.
5. The method of claim 1, wherein the waveform of the sampled value is based on differential current
Determining excitation surge current identification based on waveform discontinuity characteristics, comprising:
for differential current
Processing the sampling points to obtain a point differential filtering result di diffΦ The calculation formula is as follows:
di diffΦ (k)＝i diffΦ (k)-i diffΦ (k-1)
in the above formula, k represents the kth sampling point of the differential current, and the differential operation result of the differential current sampling value is obtained through the operation of the above formula;
differential sampling value di using differential currents of each phase diffΦ (k) The following calculation was performed to obtain the waveform discontinuity index λ:
when lambda is more than 1, the waveform is identified as uninterrupted characteristic, namely non-excitation surge waveform characteristic; when λ <1, the waveform is identified as having a discontinuous characteristic, i.e., having a surge waveform characteristic.
6. A transformer inrush current identification system based on waveform shifting and discontinuity characteristics, comprising:
the three-phase current collecting module is used for collecting high-voltage side three-phase current and low-voltage side three-phase current;
the differential current sampling value calculating module is used for calculating t according to the collected high-voltage side three-phase current and low-voltage side three-phase current j Three-phase differential current sampling values of the transformer at the moment;
the waveform deviation characteristic inrush current identification module is used for determining excitation inrush current identification based on waveform asymmetry deviation characteristics according to the sampling value waveform of the differential current;
the waveform interruption characteristic inrush current identification module is used for determining excitation inrush current identification based on waveform interruption characteristics according to the sampling value waveform of the differential current;
and the inrush current identification waveform module is used for determining to identify an inrush current waveform when the square wave index eta <1 or the waveform break index lambda <1 according to the excitation inrush current identification based on the waveform asymmetry deviation characteristic and the excitation inrush current identification based on the waveform break characteristic.
7. The system of claim 6, wherein collecting the three-phase current module comprises:
the collecting three-phase current sub-module is used for collecting the high-voltage side of the converter transformer at t j Three-phase current at time
And low pressure side at t j Three-phase current->
Wherein (1)>
A, B, C three phases, t, of a converter transformer j J is a natural number for the current sampling instant.
8. The system of claim 7, wherein the means for calculating differential current samples comprises:
calculating t according to the following formula j Three-phase differential current sampling value of time transformer
Where ratio is the transformation ratio of the transformer.
9. The system of claim 6, wherein determining a waveform offset characteristic inrush current identification module comprises:
a waveform shaping sub-module for shaping sampling value waveform of differential current
Shaping into square wave +.>
Setting shaping threshold constant value i set ，
When in use, let->
When in use, let->
When in use, let->
(Continuous)
The pulse consisting of the sampling points of (a) is called positive pulse; continuous->
The pulse consisting of the sampling points of (a) is called a negative pulse; />
For no pulse, the number of sampling points in the pulse is called pulse width and is denoted by N;
when the differential flow waveform is positive and negative symmetrical, the square wave
A symmetrical square wave pulse sequence with positive and negative phases, when the differential flow waveform is shifted, +.>
Appears as a single sided square wave pulse train biased to one side,
p represents the polarity of the pulse, p=1 in the positive pulse and p= -1 in the negative pulse;
assuming that the current sampling point is located at the ith pulse, p i Representing the polarity of the pulse, p i-1 Representing the previous adjacentPolarity of pulses, at the same time, N i Representing the number of sampling points of the ith pulse where the current sampling is located, namely, stopping the pulse width to the current sampling point, N i-1 Representing the number of samples in the previous adjacent pulse, i.e. the pulse width;
the square wave index determination submodule is used for obtaining square wave index eta by calculating two immediately adjacent pulses, wherein the square wave index submodule is used for pulse having dual properties of polarity and width:
When eta >1, reflect
Positive and negative symmetry, namely non-excitation surge current waveform characteristics; otherwise, if eta is less than 1, reflecting +.>
Asymmetric offset, i.e., excitation surge waveform characteristics.
10. The system of claim 6, wherein determining a waveform discontinuity characteristic inrush current identification module comprises:
obtaining a differential filtering result submodule for differential current
Processing the sampling points to obtain a point differential filtering result di diffΦ The calculation formula is as follows:
di diffΦ (k)＝i diffΦ (k)-i diffΦ (k-1)
in the above formula, k represents the kth sampling point of the differential current, and the differential operation result of the differential current sampling value is obtained through the operation of the above formula;
a waveform interruption index sub-module is obtained for utilizing the differential sampling value di of the differential current of each phase diffΦ (k) The following calculation was performed to obtain the waveform discontinuity index λ:
when lambda is more than 1, the waveform is identified as uninterrupted characteristic, namely non-excitation surge waveform characteristic; when λ <1, the waveform is identified as having a discontinuous characteristic, i.e., having a surge waveform characteristic.
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