Disclosure of Invention
The invention aims to provide a medium-voltage grounding fault intelligent diagnosis system and a control method thereof, which aim to solve the problems that a medium-voltage circuit is possibly influenced by environmental factors, such as increase of transition resistance, so that high-resistance grounding faults occur, the detection precision of the traditional fault diagnosis method for the high-resistance grounding faults is not high, and particularly, the precise fault identification is difficult to realize under various complex environmental conditions.
In order to achieve the above purpose, the present invention provides the following technical solutions:
the intelligent medium-voltage grounding fault diagnosis system comprises a data acquisition module, a signal processing module, a characteristic extraction module, a fault diagnosis module and a display and alarm module;
The data acquisition module is used for acquiring transient current signals in the medium-voltage distribution line, adopts a rogowski coil and is provided with a temperature compensation function;
The signal processing module is used for decomposing the acquired transient current signals through multi-resolution wavelet transformation, and extracting time-frequency characteristics of the signals;
the feature extraction module is used for calculating energy moment Q j under each decomposition scale so as to represent the energy distribution of fault signals in different frequency bands;
the fault diagnosis module adopts a least square multistage support vector machine, takes the extracted time-frequency characteristics as input, performs classification diagnosis of high-resistance ground faults and outputs fault diagnosis results;
the display and alarm module is used for displaying fault diagnosis results in real time and triggering alarm when detecting high-resistance ground faults, and the alarm module comprises a plurality of alarm modes of sound, light, short messages or APP pushing.
The invention is further optimized, wherein the signal processing module uses orthogonal wavelet transformation to carry out multi-scale decomposition on the transient current signal, the decomposition layer number is J, and the signal obtained under each decomposition scale comprises a detail signal and a discrete smooth approximation value.
As a further optimization of the invention, the feature extraction module calculates the energy moment Q j at each decomposition scale by:
Wherein M is the number of sampling points, D j [ n ] is the discrete detail signal under j decomposition scale, gamma j is the corresponding weight factor, and Deltat is the sampling time interval.
The invention further optimizes the content, wherein a least square multistage support vector machine in the fault diagnosis module adopts a kernel function K (x i,xj) and performs parameter optimization on the kernel function K by a Lagrange optimization method, and the optimization targets are as follows:
where w is the weight vector, C is the penalty parameter, and ζ i is the relaxation factor.
The invention further optimizes the content, wherein the fault diagnosis module trains the least square multistage support vector machine by utilizing historical fault data, and updates model parameters thereof through real-time signals so as to realize online learning and dynamic fault diagnosis.
The display and alarm module comprises an alarm threshold setting unit, and when the predicted fault occurrence probability exceeds a preset threshold, the system automatically triggers an alarm signal.
As a further optimization of the invention, the method comprises the following steps:
s1, signal acquisition, namely acquiring transient current signals in a medium-voltage distribution line in real time through a data acquisition module;
S2, signal processing, namely performing multi-scale decomposition on the acquired transient current signal by utilizing orthogonal wavelet transformation to acquire a detail signal and a discrete smooth approximation value under each decomposition scale;
s3, extracting the time-frequency characteristics of fault signals by calculating energy moment under each decomposition scale;
s4, fault diagnosis, namely inputting the extracted time-frequency characteristics into a least square multistage support vector machine to perform fault classification diagnosis, and obtaining probability or classification result of fault occurrence;
And S5, displaying and alarming results, namely displaying and triggering an alarm in real time according to the fault diagnosis results.
As a further optimization of the invention, in the feature extraction step, the calculated energy moment Q j characterizes the energy distribution of the signal in each frequency band and is used for identifying high-resistance ground faults in combination with the nonlinear features of the signal.
The invention further optimizes the content, wherein the fault diagnosis step adjusts parameters of the support vector machine through a Lagrange optimization method to realize the fine classification diagnosis of different fault types.
As the content of further optimization of the invention, the system utilizes the data acquired in real time to perform online learning and model updating, thereby ensuring the timeliness and accuracy of fault diagnosis.
Compared with the prior art, the invention has the beneficial effects that:
1. According to the invention, the time-frequency characteristics of transient signals are extracted through wavelet transformation, and a least square multistage support vector machine is combined, so that high-resistance ground faults in a complex environment can be effectively identified, the accuracy and reliability of diagnosis are improved, and the parameters of the support vector machine are optimized by adopting a least square method and a Lagrange optimization technology, so that a diagnosis system can maintain high-efficiency fault identification capability under various environmental conditions, and a real-time signal processing and online learning mechanism can rapidly respond and process new fault signals, thereby ensuring that the power distribution network can timely and accurately diagnose and alarm when faults occur, and ensuring the safe operation of the system;
2. According to the invention, through integrating the multi-resolution wavelet transformation and the least square multi-stage support vector machine, the high-resistance grounding fault signal in the medium-voltage direct-current power distribution network is effectively extracted and analyzed, and the time-frequency characteristics of the fault signal can be captured by the system by utilizing the multi-scale analysis capability of the wavelet transformation, so that the accurate diagnosis of complex nonlinear faults is realized;
3. According to the invention, the system can adjust the diagnosis model in real time, dynamically adapt to the continuously-changing fault mode and operation condition, ensure that the high-efficiency fault identification capability can be maintained under different environments, reduce the downtime of the power system, reduce the operation and maintenance cost and prolong the service life of equipment.
Detailed Description
Referring to fig. 1, the present invention provides a technical solution:
the intelligent medium-voltage grounding fault diagnosis system comprises a data acquisition module, a signal processing module, a characteristic extraction module, a fault diagnosis module and a display and alarm module;
The data acquisition module is used for acquiring transient current signals in the medium-voltage distribution line, adopts a rogowski coil and is provided with a temperature compensation function;
The signal processing module is used for decomposing the acquired transient current signals through multi-resolution wavelet transformation, and extracting time-frequency characteristics of the signals;
the feature extraction module is used for calculating energy moment Q j under each decomposition scale so as to represent the energy distribution of fault signals in different frequency bands;
the fault diagnosis module adopts a least square multistage support vector machine, takes the extracted time-frequency characteristics as input, performs classification diagnosis of high-resistance ground faults and outputs fault diagnosis results;
The display and alarm module is used for displaying fault diagnosis results in real time and triggering alarm when high-resistance ground faults are detected, the alarm module comprises a plurality of alarm modes of sound, light, short messages or APP pushing, and through the cooperative work of the modules, the system can realize rapid and accurate diagnosis of the medium-voltage ground faults and ensure safe operation of an electric power system.
According to the technical scheme further implemented by the scheme, the signal processing module carries out multi-scale decomposition on the transient current signal by using orthogonal wavelet transformation, the decomposition layer number is J, the signals obtained under each decomposition scale comprise detail signals and discrete smooth approximation values, the orthogonal wavelet transformation provides multi-scale analysis on fault signals, fault characteristics in different frequency bands can be effectively captured, and the accuracy and reliability of diagnosis are enhanced;
As a further implementation of the solution, the feature extraction module calculates the energy moment Q j under each decomposition scale according to the following formula:
Wherein M is the number of sampling points, D j n is the discrete detail signal under j decomposition scale, gamma j is the corresponding weight factor, deltat is the sampling time interval, and the calculation of energy moment can quantify the energy distribution of the signal in each frequency band, thereby providing refined fault feature extraction and supporting more accurate fault diagnosis;
As a further implementation technical scheme of the scheme, a least square multistage support vector machine in the fault diagnosis module adopts a kernel function K (x i,xj), and performs parameter optimization on the kernel function K by a Lagrange optimization method, wherein the optimization targets are as follows:
Wherein w is a weight vector, C is a punishment parameter, xi i is a relaxation factor, and the system can optimize the decision boundary of a support vector machine through a Lagrangian optimization method, so that the accuracy and the robustness of fault classification are ensured;
According to the technical scheme further implemented by the scheme, the fault diagnosis module trains the least square multistage support vector machine by utilizing historical fault data, model parameters of the least square multistage support vector machine are updated through real-time signals, online learning and dynamic fault diagnosis are achieved, and the system can adapt to continuously-changing operation environments and improves the instantaneity and accuracy of fault diagnosis through online learning and model updating;
According to the technical scheme further implemented by the scheme, the display and alarm module comprises an alarm threshold setting unit, when the predicted fault occurrence probability exceeds a preset threshold, the system automatically triggers an alarm signal, and the set alarm threshold can ensure that an alarm is sent out in time when a high-probability fault occurs, so that the system downtime is reduced and the accident risk is reduced;
example 1
The method is characterized in that a medium-voltage direct-current power distribution network is subjected to high-resistance grounding fault risks due to photovoltaic energy access, and particularly when environmental conditions change, the traditional fault detection method is difficult to accurately identify the faults, so that the intelligent medium-voltage grounding fault diagnosis system based on the method is implemented for improving the accuracy and timeliness of fault detection;
The implementation steps are as follows:
The method comprises the following steps of S1, signal acquisition, namely installing a high-precision current sensor at a key node of the power distribution network, wherein the high-precision current sensor is used for acquiring transient current signals in real time, and a data acquisition module transmits the signals to a signal processing module;
S2, performing multi-scale decomposition on the acquired transient current signal by using orthogonal wavelet transformation, and obtaining a detail signal and a discrete smooth approximation value under each decomposition scale by assuming that the signal is decomposed into 4 scales, wherein high-frequency and low-frequency characteristics in the signal are effectively separated through the process;
S3, extracting features, namely calculating energy moments Q j for each decomposition scale, wherein the energy moments Q j reflect the energy distribution of signals in each frequency band, and the extracted features show that significant energy concentration exists at the 3 rd decomposition scale, so that high-resistance ground faults possibly exist;
S4, fault diagnosis, namely inputting the extracted time-frequency characteristics into a least square multistage support vector machine for classification diagnosis, accurately identifying high-resistance ground faults by a system through an optimized kernel function and weight, and giving out a fault probability of 85%;
s5, displaying and alarming results, namely immediately triggering an alarm signal by a display and alarm module and displaying a fault position and possible fault types on a monitoring interface to inform operation and maintenance personnel to process because the fault probability exceeds a 70% alarm threshold preset by the system;
as a result, through the implementation, the system successfully detects and diagnoses the high-resistance ground fault in the medium-voltage distribution network, ensures that the fault is identified and processed in an early stage, and avoids more serious power accidents, thereby proving the high efficiency and accuracy of the invention in the detection of the high-resistance ground fault.
Example two
In another project, a medium-voltage direct current power distribution network is adopted in one industrial park to provide power support for a plurality of production workshops, transient current fluctuation often occurs in the power distribution network due to high-frequency start-stop operation of production equipment, and the risk of high-resistance ground faults is increased.
The implementation steps are as follows:
S1, signal acquisition, wherein an installed sensor network covers key power nodes of the whole industrial park, transient current signals of all the nodes are acquired in real time, and the signals are collected to a central processing unit by a data acquisition module;
s2, signal processing, namely carrying out 6-layer decomposition on the acquired signals by adopting orthogonal wavelet transformation, successfully extracting signal details containing high-frequency and low-frequency characteristics by a system through decomposition, and particularly focusing on abnormal signals appearing in decomposing the 5 th layer and the 6 th layer;
S3, extracting characteristics, namely calculating an energy moment Q j for each signal of the decomposition scale, wherein in the analysis process, the energy moment Q j of the 5 th layer is found to be obviously higher than that of other layers, which implies that the possibility of high-resistance ground faults exists in the frequency band;
s4, fault diagnosis, namely inputting the extracted characteristic of the energy moment Q j into a least square multistage support vector machine to perform fault diagnosis, wherein the system has the capability of classifying complex fault types after online learning, and a diagnosis result shows that a high-resistance ground fault exists on an electric power line of a specific workshop, and the fault probability is 92%;
S5, result display and alarm, namely, according to the diagnosis result, the system gives an alarm in a control room, and highlights the specific position and type of the fault on a monitoring screen, so that maintenance personnel can rapidly position and solve the fault according to the system prompt, and the production continuity is ensured;
In practical application, the intelligent diagnosis system successfully identifies and diagnoses the high-resistance ground fault in the complex environment, ensures the stability of the power distribution network of the industrial park, and further proves the applicability and reliability of the intelligent diagnosis system in various environmental conditions.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the method of the present invention and its core ideas. The foregoing is merely illustrative of the preferred embodiments of the invention, and it will be appreciated that numerous modifications, adaptations and variations of the invention can be made by those skilled in the art without departing from the principles of the invention, and that other features and advantages of the invention can be combined in any suitable manner, and that no improvement in the design or design of the invention is intended to be applied directly to other applications.