Power distribution network high resistance earthing fault detection method based on wavelet transformation and neural network
Technical field
The present invention relates to distribution net work earthing fault detections, and in particular to a kind of distribution based on wavelet transformation and neural network
Net high resistance earthing fault detection method.
Background technique
High resistance earthing fault (HIF) refers to that power circuit is situated between by the way that road, soil, branch or cement works object etc. are conductive
The ground fault that matter is occurred, it may occur however that in each voltage class, influence power distribution network normal operation.Due to radio frequency
The high-impedance behavior of medium, when high resistance earthing fault occurs for power distribution network, fault current very little, and it is frequently accompanied by electric arc, commonly
Zero-sequence current protection be difficult to detect.In the high resistance earthing fault of small current neutral grounding system especially resonant earthed system, arc
Light ground fault accounts for very big a part.Due to the reason of free of air, the impedance ground variation of arc grounding very greatly, makes existing
Protection starts repeatedly, restores, and may result in the protection overstepping of adjacent lines, equipment, can also cause total system overvoltage,
And then electrical equipment is damaged, make fault spread, reduces the power supply reliability of power grid.Route operates with failure and may make for a long time
Fault point temperature is excessively high, to cause fire, causes the permanent damages of electrical equipment, and step voltage is reachable around grounding point
To several kilovolts, power system stability operation and personal safety are seriously threatened.It can be to connect that high impedance ground fault, which is effectively detected,
The route selection and positioning got off provide criterion, so the high resistance earthing fault detection of power distribution network is particularly significant.
Summary of the invention
In view of this, the purpose of the present invention is to provide a kind of power distribution network high resistants based on wavelet transformation and neural network to connect
Earth fault detection method can effectively detect power distribution network high resistance earthing fault.
To achieve the above object, the present invention adopts the following technical scheme:
A kind of power distribution network high resistance earthing fault detection method based on wavelet transformation and neural network, comprising the following steps:
Step S1: power distribution network line current signal to be detected is acquired;
Step S2: using db4 small echo as morther wavelet, wavelet transform is carried out to line current signal, and reconstructed
Waveform;
Step S3: the neural network parameter of evolution is set;
Step S4: using reconfiguration waveform as the input quantity of the neural network to develop, k-th of mind of input quantity and evolution layer is calculated
The error of activation degree and output quantity and desired value through manhatton distance, k-th neuron between member;
Step S5: if the activation degree of k-th of neuron is less than preset threshold or output quantity and the error of desired value is more than
One new neuron is placed on a position (k+1), otherwise updates weight by preset threshold;
Step S6: the manhatton distance between o-th of neuron and p-th of neuron is calculatedWith
Step S7: ifWithRespectively less than threshold value Dthr, then the two neurons are polymerize;
Step S8: repeating step S4-S7, until all input quantities are disposed, the neural network output developed
As a result, and judging power distribution network to be detected with the presence or absence of high resistance earthing fault according to output.
Further, the wavelet transform sample frequency 10kHz, sampling time 0.5s.
Further, the neural network parameter of the evolution includes neuronal activation level thresholds Athr, error threshold
Ethr, two neurons manhatton distance threshold value Dthr, learning rate α1And α2。
Further, the step S4 parameter calculates specifically:
J-th of input quantity IjManhatton distance between k-th of neuron of evolution layer is
The activation degree A of k-th of neuronk=1-Djk, WikFor weight;
Output quantity O1With desired valueError
Further, the step S5 specifically: if AkLess than AthrOr E1More than Ethr, a new neuron is placed
In a position (k+1), weight W is otherwise updatedik(t+1)=Wik(t)+α1(Ii(t+1)-Wik(t)) and Wk1(t+1)=Wk1(t)+α2(AkE1)。
Further, describedWithSpecifically:
Wherein Wio、Wip、Wo1And Wp1For weight.
Compared with the prior art, the invention has the following beneficial effects:
1, the topological structure that the neural network that the present invention develops is not fixed, can drill online after carrying out data processing
Turn to new structure.
2, the neural network that develops of the present invention can by incremental training Fast Learning, have good abstract ability with
And network model is reassembled as to the ability of continually changing environment, wherein structure and parameter adapts to simultaneously.
3, the side that the neural network that the present invention develops passes through addition online and the connection weight for deleting neuron, adjustment neuron
The generation that averting a calamity property of formula is forgotten, increases the detection reliability and efficiency of power distribution network high resistance earthing fault.
Detailed description of the invention
Fig. 1 is the method for the present invention flow chart;
Fig. 2 is the structural schematic diagram of the neural network to develop in the embodiment of the present invention.
Specific embodiment
The present invention will be further described with reference to the accompanying drawings and embodiments.
Fig. 1 is please referred to, the present invention provides a kind of based on wavelet transformation and the inspection of the power distribution network high resistance earthing fault of neural network
Survey method, comprising the following steps:
Step S1: power distribution network line current signal to be detected is acquired;
Step S2: using db4 small echo as morther wavelet, wavelet transform is carried out to line current signal, and reconstructed
Waveform;
Step S3: the neural network parameter of evolution is set;
Step S4: using reconfiguration waveform as the input quantity of the neural network to develop, k-th of mind of input quantity and evolution layer is calculated
The error of activation degree and output quantity and desired value through manhatton distance, k-th neuron between member;
Step S5: if the activation degree of k-th of neuron is less than preset threshold or output quantity and the error of desired value is more than
One new neuron is placed on a position (k+1), otherwise updates weight by preset threshold;
Step S6: the manhatton distance between o-th of neuron and p-th of neuron is calculatedWith
Step S7: ifWithRespectively less than threshold value Dthr, then the two neurons are polymerize;
Step S8: repeating step S4-S7, until all input quantities are disposed, the neural network output developed
As a result, and judging power distribution network to be detected with the presence or absence of high resistance earthing fault according to output.
In the present embodiment, the wavelet transform sample frequency 10kHz, sampling time 0.5s.
In the present embodiment, the neural network parameter of the evolution includes neuronal activation level thresholds Athr, error threshold
Ethr, two neurons manhatton distance threshold value Dthr, learning rate α1And α2。
Further, the step S4 parameter calculates specifically:
J-th of input quantity IjManhatton distance between k-th of neuron of evolution layer is
The activation degree A of k-th of neuronk=1-Djk, WikFor weight;
Output quantity O1With desired valueError
In the present embodiment, the step S5 specifically: if AkLess than AthrOr E1More than Ethr, by a new neuron
It is placed on a position (k+1), otherwise updates weight Wik(t+1)=Wik(t)+α1(Ii(t+1)-Wik(t)) and Wk1(t+1)=Wk1(t)+α2
(AkE1)。
In the present embodiment, describedWithSpecifically:
Wherein Wio、Wip、Wo1And Wp1For weight.
The foregoing is merely presently preferred embodiments of the present invention, all equivalent changes done according to scope of the present invention patent with
Modification, is all covered by the present invention.