CN111487508A - Single-phase high-resistance grounding fault identification device for power distribution network - Google Patents
Single-phase high-resistance grounding fault identification device for power distribution network Download PDFInfo
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- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- 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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Abstract
The invention discloses a single-phase high-resistance earth fault identification device for a power distribution network, which comprises a central control decision module, a frequency modulation current signal injection module, a wavelet packet energy ratio calculation module, a wavelet packet decomposition module and a zero sequence voltage analysis module, wherein the central control decision module is used for carrying out zero sequence voltage analysis on a power distribution network; the central control decision module is respectively and electrically connected with the frequency modulation current signal injection module and the wavelet packet energy ratio calculation module; the frequency modulation current signal injection module is connected with and injected into the power distribution network; the wavelet packet energy ratio calculation module is electrically connected with the wavelet packet decomposition module; the wavelet packet decomposition module is electrically connected with the zero sequence voltage analysis module; and the zero sequence voltage analysis module is connected with a voltage transformer. The method can accurately identify the single-phase high-resistance fault of the power distribution network.
Description
Technical Field
The invention belongs to the technical field of power distribution network fault identification, and particularly relates to a single-phase high-resistance grounding fault identification device for a power distribution network.
Background
The accurate and fast identification of the power distribution network faults is an important link for improving the operation reliability of the power distribution network and ensuring the power quality of users. However, the fault characteristics of the single-phase high-resistance earth fault of the power distribution network are not obvious, the requirements of the traditional protection scheme cannot be met, and the fault identification difficulty is increased. If the fault exists for a long time, the fault is enlarged, and the safety of the power grid is influenced.
The running state of the power distribution network can be roughly divided into a normal state, a short-circuit fault and a disconnection fault; the short-circuit fault can be divided into a single-phase earth fault, a two-phase short circuit and a three-phase short circuit. The disconnection fault, the single-phase low-resistance earth fault and the residual three short-circuit faults of the power distribution network have obvious characteristic quantities and can be easily identified through a protection device. And the single-phase high-resistance earth fault is easy to be missed to be judged as a normal state. Therefore, it is necessary to extract the identification feature of the high resistance fault to distinguish it from the normal state.
The research difficulty of the high-resistance fault of the power distribution network is the extraction of the high-resistance fault characteristics. The fault current is weak when the high-resistance fault occurs, the three-phase voltage and current are almost the same as those before the fault, the steady-state characteristic is not obvious, and the detection difficulty is increased. Aiming at the problem of high-resistance faults of a power distribution network, experts and scholars at home and abroad carry out a series of researches, and the current high-resistance fault identification technology mainly comprises a high-resistance grounding fault judgment method based on projected quantity differential of neutral point current and zero sequence current of a line, a method for judging a fault section based on a correlation coefficient of a phase current sudden change and a phase voltage sudden change derivative, fault positioning based on transient zero sequence current signal analysis and processing and the like. In general, the current research on high-resistance fault feature extraction lacks a stable fault feature quantity irrelevant to the size of fault resistance, and lacks the research on the influence of other operation states on the feature quantity, so that the accurate identification of the high-resistance fault of the power distribution network is still very difficult.
Therefore, there is a need to develop a single-phase high-resistance ground fault identification device for a power distribution network.
Disclosure of Invention
The invention aims to provide a single-phase high-resistance grounding fault identification device for a power distribution network, which can extract the identification characteristics of high-resistance faults, distinguish the high-resistance faults from normal states and accurately identify the single-phase high-resistance faults of the power distribution network.
The invention relates to a single-phase high-resistance earth fault identification device for a power distribution network, which comprises a central control decision module, a frequency modulation current signal injection module, a wavelet packet energy ratio calculation module, a wavelet packet decomposition module and a zero sequence voltage analysis module, wherein the central control decision module is used for carrying out zero sequence voltage analysis on a power distribution network; the central control decision module is respectively and electrically connected with the frequency modulation current signal injection module and the wavelet packet energy ratio calculation module; the frequency modulation current signal injection module is connected with and injected into the power distribution network; the wavelet packet energy ratio calculation module is electrically connected with the wavelet packet decomposition module; the wavelet packet decomposition module is electrically connected with the zero sequence voltage analysis module; the zero sequence voltage analysis module is connected with a voltage transformer;
the frequency modulation current signal injection module is used for generating a characteristic frequency current signal and injecting the characteristic frequency current signal into the power distribution network through an injection transformer;
the zero sequence voltage analysis module is used for extracting a zero sequence voltage signal according to the voltage signal acquired from the voltage transformer;
the wavelet packet decomposition module is used for carrying out frequency domain analysis on the zero sequence voltage by using a wavelet packet decomposition method,extracting energy from the nodes to calculate the high-frequency band energy ratio E of the zero-sequence voltageh_％And the energy ratio E of the low frequency bandl_％The frequency range of the low frequency band is 0 Hz-125 Hz, and the frequency range of the high frequency band is 125 Hz-1000 Hz;
the wavelet packet energy ratio calculation module is used for calculating zero sequence voltage low-frequency band energy ElAnd energy E of high frequency bandhThe ratio is used as the identification characteristic quantity of the high-resistance fault, namely the energy ratio of the zero-sequence voltage wavelet packet
The energy ratio of the wavelet packet of the zero sequence voltage
And comparing the single-phase high-resistance fault with the zero-sequence voltage wavelet packet energy ratio in the normal operation state to judge whether the power distribution network has the single-phase high-resistance fault.
Further, the frequency modulation current signal injection module comprises a pulse driving circuit and an inverter electrically connected with the pulse driving circuit;
the pulse driving circuit is electrically connected with the central control decision module, the pulse driving circuit is used for sending out a trigger pulse signal and controlling an output signal of the inverter, and the output end of the inverter is connected to the injection transformer.
The power distribution network single-phase high-resistance grounding fault identification device further comprises a human-computer interaction module which is used for being an operation platform of the power distribution network single-phase high-resistance grounding fault identification device and allowing operation personnel to carry out fault data calling and inquiring operations, and the human-computer interaction module is electrically connected with the central control decision module.
And the historical database module is connected with the central control decision module, and stores the acquired voltage and current data and the judgment result into the historical database module to provide data support for optimizing the operation of the power distribution network.
The invention has the following advantages: the system can accurately identify the single-phase high-resistance fault characteristics of the power distribution network, realize accurate identification of the single-phase high-resistance fault of the power distribution network, has high identification precision, and cannot influence the normal operation of the power distribution network. In addition, the invention has the characteristics of simple structure, safe and efficient operation, convenience, rapidness and the like, and is suitable for large-scale popularization and application.
Drawings
FIG. 1 is a functional block diagram of the present embodiment;
FIG. 2 is a schematic block diagram of a FM current signal injection module according to the present embodiment;
FIG. 3 is a schematic diagram illustrating the decomposition of a 3-layer wavelet packet in this embodiment;
in the figure: the system comprises a 1-central control decision module, a 2-frequency modulation current signal injection module, a 2 a-pulse drive circuit, a 2 b-inverter, a 3-wavelet packet energy ratio calculation module, a 4-wavelet packet decomposition module, a 5-zero sequence voltage analysis module, a 6-voltage transformer, a 7-human-computer interaction module and an 8-historical database module.
Detailed Description
The invention will be further explained with reference to the drawings.
As shown in fig. 1, in this embodiment, a single-phase high-resistance ground fault identification device for a power distribution network includes a central control decision module 1, a frequency modulation current signal injection module 2, a wavelet packet energy ratio calculation module 3, a wavelet packet decomposition module 4, and a zero sequence voltage analysis module 5. The central control decision module 1 is respectively and electrically connected with the frequency modulation current signal injection module 2 and the wavelet packet energy ratio calculation module 3. And the frequency modulation current signal injection module 2 is connected with an injection power distribution network. The wavelet packet energy ratio calculation module 3 is electrically connected with the wavelet packet decomposition module 4. The wavelet packet decomposition module 4 is electrically connected with the zero sequence voltage analysis module 5. And the zero sequence voltage analysis module 5 is connected with a voltage transformer. The frequency modulation current signal injection module 2 is used for generating a characteristic frequency current signal and injecting the characteristic frequency current signal into the injection transformerTo the distribution network. The zero sequence voltage analysis module 5 is configured to extract a zero sequence voltage signal according to the voltage signal collected from the voltage transformer. The wavelet packet decomposition module 4 is used for performing frequency domain analysis on the zero sequence voltage by using a wavelet packet decomposition method, extracting energy of nodes in the zero sequence voltage, and calculating the high-frequency band energy proportion E of the zero sequence voltageh_％And the energy ratio E of the low frequency bandl_％The frequency range of the low frequency band is 0 Hz-125 Hz, and the frequency range of the high frequency band is 125 Hz-1000 Hz. The wavelet packet energy ratio calculation module 3 is used for calculating zero sequence voltage low-frequency band energy ElAnd energy E of high frequency bandhThe ratio is used as the identification characteristic quantity of the high-resistance fault, namely the energy ratio of the zero-sequence voltage wavelet packet
The energy ratio of the wavelet packet of the zero sequence voltage
And comparing the single-phase high-resistance fault with the zero-sequence voltage wavelet packet energy ratio in the normal operation state to judge whether the power distribution network has the single-phase high-resistance fault.
As shown in fig. 2, in the present embodiment, the fm current signal injection module 2 includes a pulse driving circuit 2a and an inverter 2b electrically connected to the pulse driving circuit 2 a. The pulse driving circuit 2a is electrically connected with the central control decision module 1, the pulse driving circuit 2a is used for sending out a trigger pulse signal and controlling an output signal of the inverter 2b, and the output end of the inverter 2b is connected to the injection transformer.
In this embodiment, a single-phase high resistance earth fault identification device for distribution network still includes historical database module 8, historical database module 8 links to each other with central control decision module 1. In this embodiment, the collected voltage and current data and the judgment result are stored in the historical database module 8, so as to provide data support for optimizing the operation of the power distribution network.
In this embodiment, the single-phase high-resistance ground fault identification device for the power distribution network further includes a human-computer interaction module 7, and the human-computer interaction module 7 is electrically connected with the central control decision module 1. The human-computer interaction module 7 is an operation platform of the power distribution network single-phase high-resistance earth fault identification device and is used for operators to carry out fault data calling and inquiring operations.
In the embodiment, the zero sequence voltage signal of the monitoring point of the power distribution network is an original signal S,
to decompose the jth node of the ith layer of the tree, m is the number of the node in the wavelet packet tree, and fig. 3 is a schematic diagram of the decomposition of the 3-layer wavelet packet.
In this embodiment, the wavelet skin analysis is used to perform feature extraction on the zero sequence voltage signal at the monitoring point, and the implementation steps are as follows:
(1) carrying out p-layer wavelet packet decomposition on the zero sequence voltage at the monitoring point, wherein the recurrence formula of the wavelet packet decomposition is as follows:
wherein the content of the first and second substances,
wavelet packet decomposition coefficients respectively; h is(2p-k)Low pass filter coefficients for wavelet packet decomposition; g(2p-k)High pass filter coefficients for wavelet packet decomposition; the above coefficient obtaining method is a conventional technique in the art, that is, the obtaining method can be selected by a person skilled in the art, and the calculation is also a routine operation by a person skilled in the art, and the coefficient obtaining method is not described here. Wherein i is the ith layer; 2n is used to refer to low frequency coefficients, 2n +1 is used to refer to high frequency coefficients; k refers to the kth decomposition coefficient in the wavelet packet decomposition coefficient sequence; z is used to refer to an integer;
is a wavelet packet decomposition coefficient sequence positioned at the (i + 1) th layer 2n node
The kth low frequency decomposition coefficient of (1);
is a wavelet packet decomposition coefficient sequence positioned at the (i + 1) th layer 2n +1 node
The kth high frequency decomposition coefficient.
(2) Performing single-branch reconstruction on the wavelet packet decomposition coefficient, and extracting wavelet coefficients of all frequency bands of the p-th layer, wherein a wavelet packet reconstruction recurrence formula is as follows:
wherein h is(p-2k)Low pass filter coefficients reconstructed for the wavelets; g(p-2k)High pass filter coefficients reconstructed for the wavelets; the above coefficient obtaining method is a conventional technique in the art, that is, the obtaining method can be selected by those skilled in the art, and the calculation is also a routine operation by those skilled in the art, and the obtaining method of the coefficient is not described here.
(3) Determining the energy of each frequency band signal, and setting E as the input signal is random and the output signal is also a random signalp,jFor wavelet packet decomposition coefficient sequence of j node at p layer
The energy of (c) is obtained by the following equation:
in the formula (d)j,kWavelet packet decomposition coefficient sequence for p-layer j node
K-th wavelet packet coefficient of (1), 1, …,2p-1；k＝1,2,…,n；
The wavelet packet decomposition coefficient sequence of the j node at the p layer of the decomposition tree is shown, and m is the number of the node in the decomposition tree; the above coefficient obtaining method is a conventional technique in the art, that is, the obtaining method can be selected by those skilled in the art, and the calculation is also a routine operation by those skilled in the art, and the obtaining method of the coefficient is not described here.
The node energy of the signal is then:
in this embodiment, the greater the number of wavelet packet decomposition layers, the higher the resolution accuracy of the signal frequency, and the more complicated the calculation. Considering the frequency range which can be reached in engineering sampling, the sampling frequency of the system at the monitoring point is 2kHz, 4 layers of wavelet packet decomposition are carried out on the zero sequence voltage signal, 16 nodes are obtained, and the bandwidth of each frequency band is 62.5 Hz.
Energy extraction is carried out on the bottom layer node to obtain node energy of the signal
Compared with the normal condition, the high-frequency content of the high-resistance fault zero-sequence voltage is rich, and the energy of the high-frequency section accounts for Eh_％＝Eh(E) is relatively large, and the energy ratio of the low-frequency band is El_％＝El(E) smaller.
In this embodiment, the high-band energy ratio E of the zero-sequence voltage is calculatedh_％The formula of (1) is:
calculating the energy ratio E of the low-frequency band of the zero sequence voltagel_％The formula of (1) is:
wherein: sum (E) is the total zero sequence voltage energy. In this embodiment, the energy ratio of the zero sequence voltage wavelet packet is used
Comparing with the energy ratio of the zero sequence voltage wavelet packet under the normal operation state, and when the energy ratio of the zero sequence voltage wavelet packet is
And when the energy ratio of the wavelet packet of the zero sequence voltage is larger than that in the normal operation state, the single-phase high-resistance fault of the power distribution network is represented.
Claims (4)
1. The utility model provides a single-phase high resistance earth fault discernment device for distribution network which characterized in that: the device comprises a central control decision module (1), a frequency modulation current signal injection module (2), a wavelet packet energy ratio calculation module (3), a wavelet packet decomposition module (4) and a zero sequence voltage analysis module (5); the central control decision module (1) is respectively and electrically connected with the frequency modulation current signal injection module (2) and the wavelet packet energy ratio calculation module (3); the frequency modulation current signal injection module (2) is connected with and injected into the power distribution network; the wavelet packet energy ratio calculation module (3) is electrically connected with the wavelet packet decomposition module (4); the wavelet packet decomposition module (4) is electrically connected with the zero sequence voltage analysis module (5); the zero sequence voltage analysis module (5) is connected with a voltage transformer;
the frequency modulation current signal injection module (2) is used for generating a characteristic frequency current signal and injecting the characteristic frequency current signal into the power distribution network through an injection transformer;
the zero sequence voltage analysis module (5) is used for extracting a zero sequence voltage signal according to the voltage signal collected from the voltage transformer;
the wavelet packet decomposition module (4) is used for carrying out frequency domain analysis on the zero sequence voltage by using a wavelet packet decomposition method, carrying out energy extraction on nodes in the zero sequence voltage, and calculating the high-frequency band energy proportion E of the zero sequence voltageh_％And the energy ratio E of the low frequency bandl_％The frequency range of the low frequency band is 0 Hz-125 Hz, and the frequency range of the high frequency band is 125 Hz-1000 Hz;
the wavelet packet energy ratio calculation module (3) is used for calculating zero sequence voltage low-frequency band energy ElAnd energy E of high frequency bandhThe ratio is used as the identification characteristic quantity of the high-resistance fault,i.e. zero sequence voltage wavelet packet energy ratio
The energy ratio of the wavelet packet of the zero sequence voltage
And comparing the single-phase high-resistance fault with the zero-sequence voltage wavelet packet energy ratio in the normal operation state to judge whether the power distribution network has the single-phase high-resistance fault.
2. The single-phase high-resistance ground fault identification device for the power distribution network according to claim 1, wherein: the frequency modulation current signal injection module (2) comprises a pulse drive circuit (2a) and an inverter (2b) electrically connected with the pulse drive circuit (2 a);
the pulse driving circuit (2a) is electrically connected with the central control decision module (1), the pulse driving circuit (2a) is used for sending out a trigger pulse signal and controlling an output signal of the inverter (2b), and the output end of the inverter (2b) is connected to the injection transformer.
3. The single-phase high-resistance ground fault identification device for the power distribution network according to claim 1 or 2, wherein: the power distribution network single-phase high-resistance grounding fault identification device is characterized by further comprising a human-computer interaction module (7) which is an operation platform of the power distribution network single-phase high-resistance grounding fault identification device and used for operation personnel to carry out fault data calling and inquiring operations, wherein the human-computer interaction module (7) is electrically connected with the central control decision module (1).
4. The single-phase high-resistance ground fault identification device for the power distribution network according to claim 3, wherein: the power distribution network power supply system is characterized by further comprising a historical database module (8), wherein the historical database module (8) is connected with the central control decision module (1), collected voltage and current data and judgment results are stored in the historical database module (8), and data support is provided for optimizing the operation of the power distribution network.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111487507A (en) * | 2020-06-01 | 2020-08-04 | 南方电网调峰调频发电有限公司西部检修试验分公司 | Power distribution network high-resistance fault identification method based on wavelet packet energy ratio |
| CN112234579A (en) * | 2020-10-28 | 2021-01-15 | 天生桥二级水力发电有限公司天生桥水力发电总厂 | Injection type stator grounding protection method and system of large hydraulic generator |
| CN112485714A (en) * | 2020-11-30 | 2021-03-12 | 云南电网有限责任公司电力科学研究院 | High-sensitivity ground fault detection and identification method and device |
| CN112946414A (en) * | 2020-12-19 | 2021-06-11 | 国网河南省电力公司电力科学研究院 | Zero-sequence residual voltage suppression-based method for identifying grounding phase and transition resistance of power distribution network |
| CN112986858A (en) * | 2021-01-26 | 2021-06-18 | 国网浙江杭州市萧山区供电有限公司 | Ground fault judgment method based on zero sequence wavelet decomposition calculation |
| CN114089218A (en) * | 2021-10-19 | 2022-02-25 | 广东电网有限责任公司东莞供电局 | Power distribution network high-resistance grounding fault identification method, device, terminal and medium |
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2020
- 2020-06-01 CN CN202010486268.6A patent/CN111487508A/en active Pending
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111487507A (en) * | 2020-06-01 | 2020-08-04 | 南方电网调峰调频发电有限公司西部检修试验分公司 | Power distribution network high-resistance fault identification method based on wavelet packet energy ratio |
| CN112234579A (en) * | 2020-10-28 | 2021-01-15 | 天生桥二级水力发电有限公司天生桥水力发电总厂 | Injection type stator grounding protection method and system of large hydraulic generator |
| CN112485714A (en) * | 2020-11-30 | 2021-03-12 | 云南电网有限责任公司电力科学研究院 | High-sensitivity ground fault detection and identification method and device |
| CN112485714B (en) * | 2020-11-30 | 2022-08-19 | 云南电网有限责任公司电力科学研究院 | High-sensitivity ground fault detection and identification method and device |
| CN112946414A (en) * | 2020-12-19 | 2021-06-11 | 国网河南省电力公司电力科学研究院 | Zero-sequence residual voltage suppression-based method for identifying grounding phase and transition resistance of power distribution network |
| CN112946414B (en) * | 2020-12-19 | 2022-06-14 | 国网河南省电力公司电力科学研究院 | Zero-sequence residual voltage suppression-based method for identifying grounding phase and transition resistance of power distribution network |
| CN112986858A (en) * | 2021-01-26 | 2021-06-18 | 国网浙江杭州市萧山区供电有限公司 | Ground fault judgment method based on zero sequence wavelet decomposition calculation |
| CN112986858B (en) * | 2021-01-26 | 2023-12-19 | 国网浙江杭州市萧山区供电有限公司 | Ground fault judging method based on zero sequence wavelet decomposition calculation |
| CN114089218A (en) * | 2021-10-19 | 2022-02-25 | 广东电网有限责任公司东莞供电局 | Power distribution network high-resistance grounding fault identification method, device, terminal and medium |
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