CN113311289A - Multi-stage power supply system ground fault positioning method based on wide area current transient component - Google Patents
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Abstract
The invention discloses a ground fault positioning method of a multilevel power supply system based on wide-area current transient components, which belongs to the field of power system fault transient analysis and relay protection. The method has the advantages that when the single-phase earth fault occurs in the multi-stage power supply system, the waveform does not need to be converted from a time domain to a frequency domain, so that the operation time can be greatly reduced, meanwhile, the complexity of the relay protection device can be reduced because zero sequence voltage does not need to be acquired, and the operation workload and time can be reduced by adopting logic operation for the calculation of the fault line.
Description
Technical Field
The invention belongs to the field of power system modeling and transient fault analysis, particularly relates to a method for positioning an electric leakage fault of an underground power supply system based on wide-area current transient components, and particularly relates to a method for obtaining the position of a fault line by performing logic operation after processing a current waveform by using mathematical morphology when a single-phase earth fault occurs in a multistage power supply system.
Background
The underground power supply systems such as coal mines and the like have high reliability requirements and severe working environments, and power supply cables on the working face of the coal mine are frequently dragged and moved, so that electric leakage faults are frequently caused. In order to ensure the underground safety, once the underground power supply system has an electric leakage fault, the fault line can be cut off quickly and accurately, the fault influence range is reduced to the minimum, and the normal work of the non-fault line is ensured. However, the protection override trip occurs after the leakage fault of the underground coal mine power supply system, the selectivity of leakage fault protection is improved, and the avoidance of override trip accidents has important significance.
The underground power supply system is a multi-stage power supply system, only a protection device is arranged at an outlet of each line, and the structure can also cause that the conventional leakage protection cannot ensure the selectivity and override action. At present, the reason of the leakage fault is mainly that the line selection device only judges according to the magnitude direction of the zero sequence power of the zero sequence current of the line selection device, so that protection misoperation can be caused, and the main methods at present are a steady state method and a transient state method for identifying the fault line under the leakage fault. The steady state method comprises the following steps: (1) the principle of the method is that when a power supply system has a fault, the amplitude of zero-sequence current flowing through a fault line is larger than that of a normal line, and the fault line can be selected through the characteristic. (2) The zero sequence current phase comparison method is characterized in that when a power supply system has a fault, the flowing direction of zero sequence current for a fault circuit flows from a fault circuit to a bus, and the flowing direction of zero sequence current for a normal circuit flows from the bus to the normal circuit. (3) The zero sequence current group amplitude-comparison phase method is characterized by combining an amplitude comparison method and a phase comparison method, selecting 3 lines with the maximum zero sequence current amplitude, screening out a line with zero sequence current lagging zero sequence voltage by using the phase comparison method, wherein the line is a fault line. The transient method comprises the following steps: the method comprises the following steps that (1) a first half-wave method is adopted, the zero-sequence current of a fault line has the same polarity with the voltage of a fault phase at the moment of fault occurrence, the polarity of the zero-sequence current of a normal line is opposite to that of a fault phase voltage, the fault line can be selected through the method, the TDFT asynchronous sampling is adopted to study the first half-wave method, the first half-wave method has obvious line selection effect on a neutral point arc suppression coil grounding system, but the time of a transient process is usually short, and the line selection failure condition can be caused by the influence of a plurality of uncertain factors such as a fault initial phase angle, line parameters and the like. (2) According to the energy method, after a power system has a fault, instantaneous zero-sequence power of a line is integrated so as to obtain an energy function of each line, wherein the amplitude of the zero-sequence energy function of the fault line is the largest and is opposite to the direction of a normal line. The characteristic that energy components decomposed by integration of the product of zero-sequence voltage and zero-sequence current at the moment of fault occurrence contain zero-sequence current resistance information is adopted, so that the influence of arc suppression coils on capacitive components of a line is eliminated, and line selection of a fault line is realized.
With the continuous and deep research, the number of line selection methods for single-phase earth faults is increasing, and methods such as an injection signal method, a zero sequence admittance method, an artificial neural network method and the like are provided. Although there are many fault line selection methods for anti-leakage protection, the accuracy in actual operation is not high, and related documents explain that the protection rejection malfunction exists in the underground power supply system, and the reason for these situations is that the underground environment is complex, so that the installation of the protection equipment is difficult, and meanwhile, when the underground power supply system belongs to a multi-stage power supply system and has a fault, the magnitude of the zero sequence current flowing through the fault line may be the same as that of the normal line, so that the line cannot be protected according to the traditional leakage protection setting method. This makes it more difficult to identify faulty lines when the downhole power supply network experiences a leakage fault.
Based on the research, the underground power supply system leakage fault positioning method based on the wide-area current transient component is provided, the waveform of the zero-sequence current with the fault is processed by a mathematical morphology method, the fault characteristics of the zero-sequence current are extracted, then the zero-sequence current fault characteristic information of each outgoing line of the power supply system is concentrated, the selection of a single-phase earth fault line is realized by using the logical coordination relationship between the upper outgoing line and the lower outgoing line, and the correctness of the method is verified by simulation calculation.
Disclosure of Invention
The invention aims to provide a method for positioning leakage fault of an underground power supply system based on wide-area current transient component, which is characterized in that when a short-circuit fault occurs in a multi-stage power supply system, after morphological processing is carried out on the waveform characteristics of zero-sequence current of each stage of circuit to obtain the transient direction of the zero-sequence current, the output results of each line are compared to position the fault line. The method comprises the following steps:
(1) and judging that the system has a plurality of line records of n according to the structure diagram of the multi-stage power supply system. As shown in fig. 2, the multi-stage power supply system has three stages of lines, so that the output n is 3.
(2) And outputting the XOR operation output result Di by each stage of line protection element. As shown in the figure, when a single-phase earth fault occurs in the line 3, and the zero-sequence current waveform of each line is as shown in fig. 3, the mathematical morphology method is first developed by Matheron and Serra based on an integral geometry for processing time-domain signals. The change of the zero sequence current direction is tracked through mathematical morphology. In power systems, mathematical morphology is commonly used to detect transients or any abnormal changes in power system signals. The two basic operations of mathematical morphology are dilation and erosion. By detecting transients in power system signals through the application of mathematical morphology, swell and corrosion can be mathematically expressed as:
for (n-m) is not less than 0 and m is not less than 0
ye(n)＝(f！g)(n)＝min[f(n+m)-g(m)]
for (n + m) is not less than 0 and m is not less than 0
Wherein,yd(n) and ye(n) is the expansion and corrosion operation output of the signal f (n) processed by the structural element g (m), respectively.
Opening and closing are two other blending operations based on two basic operations of mathematical morphology. y iso(n) and yc(n) represents the expansion operation after the etching operation and the etching operation after the expansion operation, respectively, and can be expressed by a mathematical formula as:
yc(n)＝(f·g)(n)＝(ye！g)(n)＝((f⊕g)！g)(n)
another operation known as the Closing Opening Difference Operation (CODO) may be used to detect transients in the signal, which may be defined as:
yCODO(n)＝yc(n)-yo(n)
because the zero-sequence current phase of the fault line and the zero-sequence current phase of the tie line are the same as the polarity of the fault phase voltage at the moment of fault, the formula for processing the zero-sequence current of the line through mathematical morphology can be defined as follows:
yout(n)＝yCODO(n)
the output result obtained by processing the zero-sequence current signal through mathematical morphology is shown in fig. 4, where the data is processed as follows:
and then carrying out XOR operation on the output results of all the lines on each stage of lines to obtain a result:
(3) summing the operation results of the lines at each stage, i.e. S ═ Sigma BiNumber of lines in which a fault occursNamely S.
(4) Judging whether S is equal to n or not, if S is equal to n, indicating that the fault occurs in the last-stage line, carrying out XOR operation on the output quantity of each protection element on the last-stage line and the connecting line of the upper-stage line, and then judging whether the output quantity is 1, wherein the line where the protection element is located is the fault line.
(5) And if s is not equal to n, performing exclusive-OR operation on the output of each protection element of the line of the stage with the fault and the tie line output Di of the next stage line to select the protection element with the output of 1, wherein the line where the protection element is located is the fault line.
3. The method for positioning the electric leakage fault of the underground power supply system based on the wide-area current transient component is specifically explained according to the attached drawings.
A multi-stage power supply system is shown in the figure. The structural matrix of the line can be obtained according to the figure:
when the line 3 has a single-phase earth fault, the fault line is processed by mathematical morphology for analysis. The obtained zero-sequence current waveform is shown in fig. 3, and the current waveform characteristics obtained by performing opening and closing operations on the zero-sequence current waveform of each line through mathematical morphology are shown in fig. 4, wherein the logical output of the line with the upward peak is judged to be 1, and the logical output of the line with the downward peak is judged to be 0.
Then, the corresponding fault discrimination matrix is obtained as:
[0 1 1 0 0 0 0]
since the summation can be S-2, it is determined that a fault has occurred on the second-stage line, and since the second-stage line is not the end line, the exclusive-or operation is performed on all protection elements on the second-stage line and the tie line of the next-stage line, so that:
since the logic output of the protection element 3 is 1, it can be determined from this that a single-phase ground fault has occurred in the line 3.
The method has the advantages that when the single-phase earth fault occurs in the multi-stage power supply system, the waveform of the zero-sequence current is processed by morphology, so that the waveform does not need to be converted from a time domain to a frequency domain, the operation time can be greatly reduced, meanwhile, the complexity of a relay protection device can be reduced because zero-sequence voltage does not need to be obtained, the method is easier to install for the underground power supply system, and the operation time can be reduced by adopting logic operation for the calculation of the fault line.
Description of the drawings:
FIG. 1 is a flow chart of a multi-stage power supply system fault line determination;
FIG. 2 is a block diagram of a multi-stage power supply system;
fig. 3 is a zero sequence current waveform diagram for a line 3 single phase earth fault;
fig. 4 is a waveform diagram of an output of zero-sequence current waveform data after mathematical morphology processing.
The specific implementation mode is as follows:
the invention belongs to the field of power system modeling and transient fault analysis, particularly relates to a method for positioning an electric leakage fault of an underground power supply system based on wide-area current transient components, and particularly relates to a method for obtaining the position of a fault line by performing logic operation after processing a current waveform by using mathematical morphology when a single-phase earth fault occurs in a multistage power supply system.
Fig. 1 is a flowchart illustrating a fault line locating process when a single-phase ground fault occurs in a multi-stage power supply system. The method specifically comprises the following steps:
(1) and judging that the system has a plurality of line records of n according to the structure diagram of the multi-stage power supply system. As shown in the drawing, the multi-stage power supply system has three stages of lines, so that the output n is 3.
(2) And calculating the output result Di of each line.
As shown in fig. 2, when a single-phase ground fault occurs in the line 3, and the zero-sequence current waveform of each line is as shown in fig. 3, the mathematical morphology method is first developed by Matheron and Serra based on an integral geometry for processing a time-domain signal. The change of the zero sequence current direction is tracked through mathematical morphology. In power systems, mathematical morphology is commonly used to detect transients or any abnormal changes in power system signals. The two basic operations of mathematical morphology are dilation and erosion. By detecting transients in power system signals through the application of mathematical morphology, swell and corrosion can be mathematically expressed as:
for (n-m) is not less than 0 and m is not less than 0
ye(n)＝(f！g)(n)＝min[f(n+m)-g(m)]
for (n + m) is not less than 0 and m is not less than 0
Wherein, yd(n) and ye(n) is the expansion and corrosion operation output of the signal f (n) processed by the structural element g (m), respectively.
Opening and closing are two other blending operations based on two basic operations of mathematical morphology. y iso(n) and yc(n) represents the expansion operation after the etching operation and the etching operation after the expansion operation, respectively, and can be expressed by a mathematical formula as:
yc(n)＝(f·g)(n)＝(ye！g)(n)＝((f⊕g)！g)(n)
another operation known as the Closing Opening Difference Operation (CODO) may be used to detect transients in the signal, which may be defined as:
yCODO(n)＝yc(n)-yo(n)
because the zero-sequence current phase of the fault line and the zero-sequence current phase of the tie line are the same as the polarity of the fault phase voltage at the moment of fault, the formula for processing the zero-sequence current of the line through mathematical morphology can be defined as follows:
yout(n)＝yCODO(n)
the output result obtained by processing the signal of the zero-sequence current through mathematical morphology is shown in the attached figure, and the data is processed as follows:
(3) and outputting the XOR operation output operation result Bi by each stage of line protection element.
And carrying out XOR operation on the output results of all the lines on each stage of lines to obtain a result:
(4) summing the operation results of the lines at each stage, i.e. S ═ Sigma BiAt this time, the number of line stages where the fault occurs is S.
(5) Judging whether S is equal to n or not, if S is equal to n, indicating that the fault occurs in the last-stage line, carrying out XOR operation on the output quantity of each protection element on the last-stage line and the connecting line of the upper-stage line, and then judging whether the output quantity is 1, wherein the line where the protection element is located is the fault line.
(6) And if s is not equal to n, performing exclusive-OR operation on the output of each protection element of the line of the stage with the fault and the tie line output Di of the next stage line to select the protection element with the output of 1, wherein the line where the protection element is located is the fault line.
4. The method for positioning the electric leakage fault of the underground power supply system based on the wide-area current transient component is specifically explained according to the attached drawings.
A multi-stage power supply system is shown in the figure. The structural matrix of the line can be obtained according to the figure:
when the line 3 has a single-phase earth fault, the fault line is processed by mathematical morphology for analysis. The obtained zero sequence current waveform is shown in the figure, and the current waveform characteristics obtained after the zero sequence current waveform of each line is subjected to opening operation and closing operation through mathematical morphology are shown in the figure, and the logic output of the line with the upward peak is judged to be 1, and the logic output of the line with the downward peak is judged to be 0.
Then, the corresponding fault discrimination matrix is obtained as:
[0 1 1 0 0 0 0]
since the summation can be S-2, it is determined that a fault has occurred on the second-stage line, and since the second-stage line is not the end line, the exclusive-or operation is performed on all protection elements on the second-stage line and the tie line of the next-stage line, so that:
since the logic output of the protection element 3 is 1, it can be determined from this that a single-phase ground fault has occurred in the line 3.
The simulation model of the attached figure is a three-level power supply system network, and the three-level power supply system network comprises three 10kV buses which are respectively marked from left to right: the bus comprises a first-stage bus (bus 1), a second-stage bus (bus 2) and a third-stage bus (bus 3). There are 7 outgoing lines denoted as L1, L2,.., L7.
(1) Line 3 single phase earth fault
The simulation results are shown in the following table:
TABLE 1 zero sequence current and power direction of each line in single-phase earth fault of line 3
| Line | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| Zero sequence current A | 0.248 | 0.248 | 0.745 | 0.248 | 0.248 | 0.248 | 0.248 |
| Zero sequence power phase | -90° | 90° | 90° | -90° | -90° | -90° | -90° |
(2) Line 7 single phase earth fault
The simulation results are shown in the following table:
TABLE 2 zero sequence current and power direction of each line in single-phase earth fault of line 7
| Line | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| Zero sequence current A | 0.248 | 0.248 | 0.745 | 0.248 | 0.248 | 0.248 | 1.49 |
| Zero sequence power phase | -90° | 90° | 90° | -90° | -90° | -90° | 90° |
From the simulation results, it can be known that in a multi-stage power supply system, when a single-phase earth fault occurs in an intermediate-stage line such as line 3, a zero-sequence current I flows through line 330＝I10+I20+I30When a single-phase earth fault occurs in a terminal line, such as line 7, the zero-sequence current flowing through line 3 is also I30＝I10+I20+I30And in both fault situations the magnitude and phase of the zero sequence power flowing through the line 3 is the same. Therefore, the protection setting is performed by the traditional zero sequence current setting method, and the risk of override tripping can occur under the condition that the middle level has a fault.
The method of mathematical morphology was first developed by Matheron and Serra based on integrating geometry for processing time domain signals. The change of the zero sequence current direction is tracked through mathematical morphology. In power systems, mathematical morphology is commonly used to detect transients or any abnormal changes in power system signals. The two basic operations of mathematical morphology are dilation and erosion. By detecting transients in power system signals through the application of mathematical morphology, swell and corrosion can be mathematically expressed as:
for (n-m) is not less than 0 and m is not less than 0
ye(n)＝(f！g)(n)＝min[f(n+m)-g(m)]
for (n + m) is not less than 0 and m is not less than 0
Wherein, yd(n) and ye(n) is the expansion and corrosion operation output of the signal f (n) processed by the structural element g (m), respectively.
Opening and closing are two other blending operations based on two basic operations of mathematical morphology. y iso(n) and yc(n) respectively represent the expansion operation after the etching operationAnd the erosion operation after the expansion operation, can be expressed by the mathematical formula:
yc(n)＝(f·g)(n)＝(ye！g)(n)＝((f⊕g)！g)(n)
another operation known as the Closing Opening Difference Operation (CODO) may be used to detect transients in the signal, which may be defined as:
yCODO(n)＝yc(n)-yo(n)
because the zero-sequence current phase of the fault line and the zero-sequence current phase of the tie line are the same as the polarity of the fault phase voltage at the moment of fault, the formula for processing the zero-sequence current of the line through mathematical morphology can be defined as follows:
yout(n)＝yCODO(n)
the signal of the zero sequence current is processed through mathematical morphology, so that the characteristics of a fault line and a non-fault line can be obtained and distinguished.
The mathematical morphology processing of the zero sequence current waveforms of the line 5 and the line 1 obtained above is shown in the figure. After the zero sequence current waveforms of the fault line and the non-fault line are processed by mathematical morphology, the first peak directions of the obtained output waveforms are different, the peak direction of the mathematical morphology output of the fault line is upward, the peak direction of the mathematical morphology output of the normal line is downward, the peak directions of the fault line and the normal line are opposite, and accordingly fault characteristics of the lines can be identified.
Different output values can be obtained by processing the zero sequence current in the fault as follows:
a multi-stage power supply system is illustrated. When the line 3 has a single-phase earth fault, the fault line is processed by mathematical morphology for analysis. And judging the logic output of the circuit with the upward peak as 1 and the logic output of the circuit with the downward peak as 0 according to the current waveform characteristics obtained by opening and closing the zero sequence current waveform of each circuit through mathematical morphology. Then, the corresponding fault discrimination matrix is:
[0110000]
(1) as can be seen from fig. 2, the power supply system has 3 stages, so n is 3;
(2) the output values of the protection elements on the buses of all levels are subjected to exclusive-OR operation to obtain the following results:
(3) and adding the output values of the circuits at all stages to obtain a result:
S＝∑Bi＝B1+B2+B3＝2
s is 2, so that the second-stage line can be judged to be in fault
(4) And performing exclusive-or operation on all the protection elements on the second-stage bus and the connecting line of the lower-stage line to obtain:
(5) the logic output of the protection element 3 is therefore 1, from which it can be determined that a single-phase earth fault has occurred in the line 3.
Claims (2)
1. A multi-stage power supply system earth fault positioning method based on wide area current transient component is characterized in that the method collects zero sequence current waveform data of each stage of circuit through a protection device when a short circuit fault occurs in an underground multi-stage power supply system, performs switching operation on the collected zero sequence current data by using a mathematical morphology method so as to obtain fault characteristics of each circuit, and determines the position of a fault circuit through logic operation by combining the connection relation of each circuit;
the method comprises the following steps:
(1) judging that the system has n lines recorded in the total number of several levels according to the structure of the multi-level power supply system, and as shown in fig. 2, it can be known that the multi-level power supply system has n =3 lines recorded in the total number of three levels;
(2) processing zero sequence current data of each line by using a mathematical morphology method to obtain fault characteristics Di of each line;
y o (n)andy c (n)the expansion operation after the erosion operation and the erosion operation after the expansion operation are expressed respectively, and can be expressed by mathematical formulas as:
another operation known as the Closing Opening Difference Operation (CODO) may be used to detect transients in the signal, which may be defined as:
the formula for processing the zero sequence current of each line by a mathematical morphology method can be defined as:
the data was then processed as follows:
(3) and performing exclusive-or operation on the output result of each stage of circuit protection element to obtain an output result Bi:
(4) summing the operation results of the lines at each stage
At this time, the number of the line stages where the fault occurs is S;
(5) judging whether S is equal to n or not, if S = n, indicating that a fault occurs in the last-stage line, carrying out XOR operation by using the output quantity of each protection element on the last-stage line and a connecting line of a higher-stage line, and then judging whether the output quantity is 1, wherein the line where the protection element is located is the fault line;
(6) and if s is not equal to n, performing exclusive-OR operation on the output of each protection element of the line of the stage with the fault and the tie line output Di of the next stage line to select the protection element with the output of 1, wherein the line where the protection element is located is the fault line.
2. Specifically explaining a method for positioning the electric leakage fault of the underground power supply system based on the wide-area current transient component according to the attached drawings;
the multi-stage power supply system is shown in fig. 2, and a structural matrix of lines can be obtained according to the diagram:
when a single-phase earth fault occurs in the line 3, the fault line is processed by mathematical morphology for analysis, the obtained zero-sequence current waveform is shown in fig. 3, the current waveform characteristics obtained after the zero-sequence current waveform of each line is subjected to opening operation and closing operation by the mathematical morphology are shown in the figure, the logic output of the line with the upward peak is judged to be 1, and the logic output of the line with the downward peak is judged to be 0;
then, the corresponding fault discrimination matrix is obtained as:
[0 1 1 0 0 0 0]
the summation can be S =2, so that it is judged that the fault occurs on the secondary line due to the secondary lineThe path is not the end path, so that xoring all protection elements on the second stage path with the tie line of the next stage path yields:
since the logic output of the protection element 3 is 1, it can be determined from this that a single-phase ground fault has occurred in the line 3.
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| CN101154807A (en) * | 2007-10-11 | 2008-04-02 | 天津大学 | Self-adaption route selection method for single-phase ground fault of power distribution network based on transient zero sequence current |
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| CN110780158A (en) * | 2019-11-29 | 2020-02-11 | 广州航海学院 | Power system overhead line fault detection method based on mathematical morphology |
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