CN114280422B - High-resistance single-phase grounding line selection method and system for resonant grounding distribution network - Google Patents
High-resistance single-phase grounding line selection method and system for resonant grounding distribution network Download PDFInfo
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Abstract
The invention discloses a high-resistance single-phase grounding line selection method and a system for a resonant grounding distribution network. The method fully utilizes signal modulation and related detection to realize weak fault feature detection, can effectively improve single-phase grounding detection sensitivity, realizes high-resistance grounding accurate line selection, and ensures the power supply reliability of the power distribution network.
Description
Technical Field
The invention belongs to the technical field of single-phase grounding fault processing of a power distribution network, and particularly relates to a high-resistance single-phase grounding line selection method and system of a resonant grounding power distribution network.
Background
At present, a small-current grounding mode is adopted in most of the power distribution networks, the problem of low-resistance grounding fault line selection of the medium-low voltage power distribution networks is solved, but single-phase grounding detection and line selection are still difficult when high-resistance grounding occurs. The single-phase grounding caused by the broken wire of the insulated wire, the discharge of the wire to the branch, the contact of the human body with the line and the like has the characteristic of high transitional resistance, the hidden trouble of personal injury is large, the grounding fault exists for a long time and even causes multipoint faults and interphase faults, but the conventional line selection method is not applicable to the grounding fault due to weak voltage and current characteristics caused by high-resistance grounding.
Many studies have been made in the field of single-phase ground fault detection, such as: group ratio amplitude-phase method, fifth harmonic method, energy function method, zero sequence admittance method, wavelet method, current abrupt variable method, active component method, first half-wave method, residual increment method, and the like. While using zero sequence components to select lines, many experts have proposed line selection methods that do not use zero sequence components, including negative sequence current methods, traveling wave methods, and "S" signal injection methods. Besides, some students have studied comprehensive criterion line selection methods based on various criteria, such as: an artificial neural network method, a fuzzy theory method, a D-S evidence theory, a rough set theory and the like.
When the high-resistance grounding is performed, the fault characteristics such as zero-sequence voltage and zero-sequence current are weak, so that great difficulty is brought to single-phase grounding detection and line selection.
Disclosure of Invention
The invention aims to provide a high-resistance single-phase grounding line selection method and a system for a resonant grounding distribution network, which are used for solving the problem of high-resistance grounding faults.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a high-resistance single-phase grounding line selection method of a resonant grounding power distribution network comprises the following steps:
(1) Real-time monitoring bus zero sequence voltage amplitude U (0) When the zero sequence voltage amplitude U of the bus (0) Reaching the protection setting value U 0set When the single-phase grounding fault line selection device is started, a low-frequency square wave with the period of T is adopted
Modulating the compensation current of the arc suppression coil, wherein A is the amplitude of a square wave, and n is a positive integer;
(2) Collecting bus zero sequence voltage u modulated by low-frequency square wave 0 (t) and zero sequence current i of each outgoing line 0i (t), i=1, 2, …, k, i being the line number, k being the total number of lines; zero sequence voltage u for bus 0 (t) performing calculation and analysis to obtain zero sequence voltage envelope amplitude; zero sequence current i for each outgoing line 0i (t)Dividing by zero sequence voltage envelope amplitude, taking absolute value and demodulating to obtain demodulation signal i' 0i (t) further performing normalization processing to obtain normalized signal i " 0i (t)；
(3) Sinusoidal signal with period T
As reference signal and normalized signal i' of each line 0i (t) performing cross-correlation detection using a cross-correlation function of
Obtaining the cross-correlation function value of each line, wherein theta is the reference signal f 2 Is τ is the reference signal f 2 Delay difference from the demodulated signal;
(4) Comparing the cross-correlation function values of the lines and finding the maximum value, assuming the cross-correlation function value R of the ith line 2,i Maximum, i.e. R 2,max ＝R 2,i Then calculate the cross-correlation function value R of the ith line 2,i Cross-correlation function value R of remaining all lines 2,j The ratio ρ of
Where j=1, 2, …, k, j+.i, by setting a criterion threshold ρ set If ρ between two lines is not less than ρ set When the fault occurs on the line with the large cross correlation function in the two lines, judging that the fault occurs on the line with the large cross correlation function in the two lines; if ρ < ρ between two lines set When it is determined that neither of the two lines is a faulty line.
Further, the frequency of the low frequency square wave is not greater than 4Hz.
Further, the protection setting value U 0set ＝KU N Wherein U is N The rated voltage of the bus is 15 percent.
Further, the criterion threshold value ρ in the step (4) is set ＝1.2。
A resonant grounded distribution network high-resistance single-phase grounded line selection system, comprising:
and a modulation module: real-time monitoring bus zero sequence voltage amplitude U (0) When the zero sequence voltage amplitude U of the bus (0) Reaching the protection setting value U 0set When the single-phase grounding fault line selection device is started, a low-frequency square wave with the period of T is adopted
Modulating the compensation current of the arc suppression coil, wherein A is the amplitude of a square wave, and n is a positive integer;
normalized signal acquisition module: bus zero sequence voltage u after low-frequency square wave modulation 0 (t) and zero sequence current i of each outgoing line 0i (t), i=1, 2, …, k, i being the line number, k being the total number of lines; zero sequence voltage u for bus 0 (t) performing calculation and analysis to obtain zero sequence voltage envelope amplitude; zero sequence current i for each outgoing line 0i (t) dividing the amplitude of the zero sequence voltage envelope by the amplitude of the zero sequence voltage envelope, and taking the absolute value to perform demodulation processing to obtain a demodulation signal i' 0i (t) further performing normalization processing to obtain normalized signal i " 0i (t)；
The cross-correlation function value acquisition module: sinusoidal signal with period T
As reference signal and normalized signal i' of each line 0i (t) performing cross-correlation detection using a cross-correlation function of
Obtaining the cross-correlation function value of each line, wherein theta is the reference signal f 2 Is τ is the reference signal f 2 Delay difference from the demodulated signal;
and a line selection module: for comparing the cross-correlation function values of the lines and finding the maximum value, the cross-correlation function value R of the ith line is assumed 2,i Maximum, i.e. R 2,max ＝R 2,i Then calculate the cross-correlation function value R of the ith line 2,i Cross-correlation function value R of remaining all lines 2,j The ratio ρ of
Where j=1, 2, …, k, j+.i, by setting a criterion threshold ρ set If ρ between two lines is not less than ρ set When the fault occurs on the line with the large cross correlation function in the two lines, judging that the fault occurs on the line with the large cross correlation function in the two lines; if ρ < ρ between two lines set When it is determined that neither of the two lines is a faulty line.
Further, the frequency of the low frequency square wave is not greater than 4Hz.
Further, the protection setting value U 0set ＝KU N Wherein U is N The rated voltage of the bus is 15 percent.
Further, the criterion threshold value ρ in the step (4) is set ＝1.2。
A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor implementing the steps of a resonant grounded distribution network high-impedance single-phase grounding line selection method when the computer program is executed.
A computer readable storage medium storing a computer program which when executed by a processor implements the steps of a resonant grounded distribution network high resistance single phase grounding line selection method.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention utilizes low-frequency square waves to modulate the compensation current of the cancellation coil, divides the zero sequence current of each line by the zero sequence voltage envelope amplitude value respectively, adjusts the zero sequence voltage envelope amplitude value, and then carries out demodulation and correlation detection, thus constructing a single-phase grounding line selection criterion based on a cross correlation function. The method can realize weak fault characteristic detection, further improve the transition resistance of single-phase grounding line selection, and ensure the power supply reliability of the power distribution network.
Furthermore, the invention performs adjustment measures to divide the zero sequence current of each circuit by the zero sequence voltage envelope amplitude, so that the components of the low-frequency square wave signal only exist in the analysis signal of the single-phase grounding circuit, and the fault characteristics are further highlighted.
Furthermore, due to the adoption of modulation and related detection, the single-phase grounding detection sensitivity can be effectively improved, and high-resistance grounding accurate line selection is realized.
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The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
Fig. 1 is a flow chart of a high-resistance single-phase grounding line selection method of a resonant grounding power distribution network based on correlation detection.
Fig. 2 is a simulation model diagram of a resonant ground system.
Fig. 3 is a simulation calculation of the measured neutral point zero sequence voltage when a single phase earth fault occurs.
Fig. 4 is zero sequence current at the outlet of a single phase earth fault line.
Fig. 5 is zero sequence current at the outlet of a non-faulty line.
Fig. 6 is a single phase earth fault line analysis signal.
Fig. 7 is a non-faulty line analysis signal.
Detailed Description
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
As shown in fig. 1, the invention discloses a high-resistance single-phase grounding line selection method of a resonant grounding power distribution network based on correlation detection, which comprises the following steps:
(1) Real-time monitoring bus zero sequence voltage amplitude U (0) When the zero sequence voltage amplitude U of the bus (0) Reaching the protection setting value U 0set Time (U) 0set ＝KU N Wherein U is N For the rated voltage of the bus, K is generally 15%. ) Starting single-phase grounding fault starting line selection by adopting low-frequency square wave with period of T
And modulating the compensation current of the arc suppression coil, wherein A is the amplitude of a square wave, n is a positive integer, and the frequency of the low-frequency square wave is not more than 4Hz.
(2) Collecting bus zero sequence voltage u modulated by low-frequency square wave 0 (t) and zero sequence current i of each outgoing line 0i (t), i=1, 2, …, k, i being the line number, k being the total number of lines. Zero sequence voltage u for bus 0 (t) performing calculation and analysis to obtain zero sequence voltage envelope amplitude; zero sequence current i for each outgoing line 0i (t) dividing the amplitude of the zero sequence voltage envelope by the amplitude of the zero sequence voltage envelope, and taking the absolute value to perform demodulation processing to obtain a demodulation signal i' 0i (t), i=1, 2, …, k, and further performing normalization processing to obtain i "" 0i (t)，i＝1,2,…,k；
(3) Sinusoidal signal with period T
Normalization as reference signal with each lineSignal i 0i (t) performing cross-correlation detection with a cross-correlation function of +.>
Obtaining each line cross-correlation function value, wherein i=1, 2 … is k, i is the line number, k is the total number of lines, and θ is the reference signal f 2 Is τ is the reference signal f 2 And the delay of the demodulated signal.
(4) Comparing the cross-correlation function values of the lines and finding the maximum value, assuming the cross-correlation function value R of the ith line 2,i Maximum, i.e. R 2,max ＝R 2,i Then calculate the cross-correlation function value R of the ith line 2,i Cross-correlation function value R of remaining all lines 2,j The ratio ρ of (j=1, 2, …, k, j+.i), i.e.
A criterion threshold value ρ can be set set Criterion threshold value ρ set =1.2, if ρ is not less than ρ between two lines set When the fault occurs on the line with the large cross correlation function in the two lines, judging that the fault occurs on the line with the large cross correlation function in the two lines; if ρ < ρ between two lines set When it is determined that neither of the two lines is a faulty line.
The invention provides a high-resistance single-phase grounding line selection method of a resonance grounding distribution network based on correlation detection, which is characterized in that low-frequency square waves are utilized to modulate compensating currents of a cancellation arc ring, zero sequence currents of all lines are respectively divided by zero sequence voltage envelope amplitude values to be adjusted, then demodulation and correlation detection are carried out, and a single-phase grounding line selection criterion based on a cross correlation function is constructed. The method fully utilizes modulation and related detection to realize weak fault feature detection, can effectively improve single-phase grounding detection sensitivity, realizes high-resistance grounding accurate line selection, and ensures the power supply reliability of the power distribution network.
Examples
FIG. 2 shows a typical resonant grounding system with 7 wires, WL 3-WL 6 each 10km in length. WL1 length is 2.5km, WL2 length is 13km, WL7 length is 5.52km, WL8 length is 1.01km. Wherein WL1, WL 5-WL 8 are overhead lines, WL 2-WL 4 are cable lines.
The positive sequence resistance, inductive reactance and capacitive reactance parameters of the cable line are respectively as follows: 0.157 Ω/km, 0.076 Ω/km, 8kΩ/km; the zero sequence resistance, inductive reactance and capacitive reactance parameters are respectively as follows: 0.157 Ω/km, 0.076 Ω/km, 8kΩ/km. The positive sequence resistance, inductive reactance and capacitive reactance parameters of the overhead line are respectively as follows: 0.132 Ω/km, 0.4 Ω/km, 300kΩ/km; the zero sequence resistance, inductive reactance and capacitive reactance parameters are respectively as follows: 0.132 Ω/km, 0.4 Ω/km, 300kΩ/km.
A simulation model is built through PSCAD/EMTDC, the arc suppression coil adopts a capacity-adjusting arc suppression coil, five groups of capacitor groups C1-C5 are adopted, and the capacitance sizes are 372 mu F, 744 mu F, 1.488mF, 2.977mF and 5.955mF respectively. The arc suppression coil winding resistance is 6Ω.
Assuming a single-phase earth fault in the system at 2s, the fault occurs on line WL3 with a transition resistance of 5kΩ. The arc suppression coil is put into the capacitor banks C1 and C2. And C1 is switched by a square wave control thyristor with the frequency of 4Hz and the duty ratio of 0.5 at 0.125 s. And taking the zero sequence current and zero sequence voltage data with the window length of 2s through 1s delay, and selecting lines according to the method.
When the single-phase earth fault does not occur, the simulation calculation inputs the cross-correlation function value of each line measured by the line selection device as shown in table 1.
TABLE 1 maximum values of the cross-correlation functions of the circuits during normal operation
| Circuit arrangement | WL1 | WL2 | WL3 | WL6 | WL7 | WL8 |
| Cross correlation function | 0.0085 | 0.0074 | 0.0077 | 0.0077 | 0.0077 | 0.0080 |
It can be found that the cross-correlation function ratio ρ of each line at this time min Less than 1.2, no single phase earth fault can be considered to occur.
The simulation calculation of the measured neutral point zero sequence voltage when a single phase earth fault occurs is shown in figure 3. The zero sequence current at the outlet of the single phase earth fault line is shown in figure 4. The zero sequence current at the outlet of the non-faulty line is shown in figure 5.
It can be seen from fig. 3 to 5 that when the transitional resistor is connected to the earth by a single phase, the neutral point voltage has a 4Hz amplitude change due to the compensation capacity of the arc suppression coil adjusted by 4Hz, so that the zero sequence currents at the outlets of the fault line and the non-fault line both have 4Hz frequency components.
Normalized zero sequence current signals of the sound circuit and the fault circuit obtained after the zero sequence current is processed are shown in fig. 6 and fig. 7 respectively.
As can be seen by comparing fig. 6, 7 with fig. 4, 5: the interference of the zero sequence voltage is basically removed after the processing. The cross-correlation function value pairs obtained by correlation detection of the normalized signal are shown in table 2.
TABLE 2 maximum values of the cross-correlation functions of the lines at failure
| Circuit arrangement | WL1 | WL2 | WL3 | WL6 | WL7 | WL8 |
| Cross correlation function | 0.0441 | 0.0466 | 0.0785 | 0.0456 | 0.0460 | 0.0444 |
The cross-correlation function value of the feed line WL3 is the largest, and ρ min Greater than 1.2, the line WL3 may be judged to be a faulty line.
The simulation results are shown in table 3 according to various conditions such as different fault lines, different fault points, different compensation degrees, different transition resistances and the like.
TABLE 3 line selection results under various fault conditions
The circuits corresponding to the correlation functions in the table are WL 1-WL 3 and WL 6-WL 8 in sequence. Through the analysis, the fault line cross-correlation function value is found to be the largest, and the minimum value of the cross-correlation function ratio rho of the fault line and the non-fault line is larger than 1.2 under various conditions. The result shows that the line selection method can accurately select lines under various grounding conditions; has better transitional resistance.
It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention 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 present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. 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.
Finally, it should be noted that: the foregoing embodiments are merely for illustrating the technical aspects of the present invention and not for limiting the scope thereof, and although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that various changes, modifications or equivalents may be made to the specific embodiments of the present invention after reading the present invention, and these changes, modifications or equivalents are within the scope of the invention as defined in the appended claims.
Claims (10)
1. The high-resistance single-phase grounding line selection method for the resonant grounding power distribution network is characterized by comprising the following steps of:
(1) Real-time monitoring bus zero sequence voltage amplitude U (0) When the zero sequence voltage amplitude U of the bus (0) Reaching the protection setting value U 0set When the single-phase grounding fault line selection device is started, a low-frequency square wave with the period of T is adopted
Modulating the compensation current of the arc suppression coil, wherein A is the amplitude of a square wave, and n is a positive integer;
(2) Collecting bus zero sequence voltage u modulated by low-frequency square wave 0 (t) and zero sequence current i of each outgoing line 0i (t), i=1, 2, …, k, i being the line number, k being the total number of lines; zero sequence voltage u for bus 0 (t) performing calculation and analysis to obtain zero sequence voltage envelope amplitude; zero sequence current i for each outgoing line 0i (t) dividing the amplitude of the zero sequence voltage envelope by the amplitude of the zero sequence voltage envelope, and taking the absolute value to perform demodulation processing to obtain a demodulation signal i' 0i (t) further performing normalization processing to obtain normalized signal i " 0i (t)；
(3) In weeks ofSinusoidal signal with period T
As reference signal and normalized signal i' of each line 0i (t) performing cross-correlation detection using a cross-correlation function of
Obtaining the cross-correlation function value of each line, wherein theta is the reference signal f 2 Is τ is the reference signal f 2 Delay difference from the demodulated signal;
(4) Comparing the cross-correlation function values of the lines and finding the maximum value, assuming the cross-correlation function value R of the ith line 2,i Maximum, i.e. R 2,max ＝R 2,i Then calculate the cross-correlation function value R of the ith line 2,i Cross-correlation function value R of remaining all lines 2,j The ratio ρ of
Where j=1, 2, …, k, j+.i, by setting a criterion threshold ρ set If ρ between two lines is not less than ρ set When the fault occurs on the line with the large cross correlation function in the two lines, judging that the fault occurs on the line with the large cross correlation function in the two lines; if ρ < ρ between two lines set When it is determined that neither of the two lines is a faulty line.
2. The method for high-resistance single-phase grounding wire selection of a resonant grounded power distribution network according to claim 1, wherein the frequency of the low-frequency square wave is not more than 4Hz.
3. The method for selecting a high-resistance single-phase grounding line of a resonant grounding power distribution network according to claim 1, wherein the protection setting value U is as follows 0set ＝KU N Wherein U is N The rated voltage of the bus is 15 percent.
4. A resonant grounded distribution network high impedance as recited in claim 1The single-phase grounding line selection method is characterized in that the criterion threshold value rho in the step (4) is as follows set ＝1.2。
5. The utility model provides a resonance ground connection distribution network high resistance single-phase ground connection line selection system which characterized in that includes:
and a modulation module: real-time monitoring bus zero sequence voltage amplitude U (0) When the zero sequence voltage amplitude U of the bus (0) Reaching the protection setting value U 0set When the single-phase grounding fault line selection device is started, a low-frequency square wave with the period of T is adopted
Modulating the compensation current of the arc suppression coil, wherein A is the amplitude of a square wave, and n is a positive integer;
normalized signal acquisition module: bus zero sequence voltage u after low-frequency square wave modulation 0 (t) and zero sequence current i of each outgoing line 0i (t), i=1, 2, …, k, i being the line number, k being the total number of lines; zero sequence voltage u for bus 0 (t) performing calculation and analysis to obtain zero sequence voltage envelope amplitude; zero sequence current i for each outgoing line 0i (t) dividing the amplitude of the zero sequence voltage envelope by the amplitude of the zero sequence voltage envelope, and taking the absolute value to perform demodulation processing to obtain a demodulation signal i' 0i (t) further performing normalization processing to obtain normalized signal i " 0i (t)；
The cross-correlation function value acquisition module: sinusoidal signal with period T
As reference signal and normalized signal i' of each line 0i (t) performing cross-correlation detection using a cross-correlation function of
Obtaining the cross-correlation function value of each line, wherein theta is the reference signal f 2 Is τ is the reference signal f 2 Delay difference from the demodulated signal;
and a line selection module: for comparison ofThe cross-correlation function value of each line is found and the maximum value is found, assuming the cross-correlation function value R of the ith line 2,i Maximum, i.e. R 2,max ＝R 2,i Then calculate the cross-correlation function value R of the ith line 2,i Cross-correlation function value R of remaining all lines 2,j The ratio ρ of
Where j=1, 2, …, k, j+.i, by setting a criterion threshold ρ set If ρ between two lines is not less than ρ set When the fault occurs on the line with the large cross correlation function in the two lines, judging that the fault occurs on the line with the large cross correlation function in the two lines; if ρ < ρ between two lines set When it is determined that neither of the two lines is a faulty line.
6. The resonant grounded distribution network high-impedance single-phase grounded line selection system of claim 5, in which the frequency of the low frequency square wave is no greater than 4Hz.
7. The resonant grounded distribution network high-resistance single-phase grounding line selection system according to claim 5, wherein the protection setting value U is 0set ＝KU N Wherein U is N The rated voltage of the bus is 15 percent.
8. The resonant grounded distribution network high-impedance single-phase ground line selection system according to claim 5, wherein the criterion threshold value ρ in step (4) is set ＝1.2。
9. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that the processor, when executing the computer program, carries out the steps of a resonant grounded power distribution network high impedance single phase grounding line selection method as claimed in any one of claims 1 to 4.
10. A computer readable storage medium storing a computer program, wherein the computer program when executed by a processor implements the steps of a resonant grounded distribution network high impedance single phase grounding line selection method as claimed in any one of claims 1 to 4.
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