Background technique
In the construction of urban distribution network, power cable replaces overhead line gradually at trend, compared with overhead line, has without ground
Upper space, the advantages such as power supply reliability is high, electric shock possibility is small, particularly suitable for urban electricity supply.Electric power in urban distribution network
There is cable run distance not grow, and the characteristics of more electric power distributions for being used to fix two places.But underground power cable inconvenience is examined
It repairs, once breaking down, needs basis to measure fault distance and remove failure in time, avoid influencing line security stable operation.
Currently, travelling wave ranging on overhead transmission line more application, but in power cable, velocity of wave is difficult to determine, zero mould passes
Broadcast characteristic it is difficult to predict.If be directly used in city cable with the signal analysis method and ranging formula of traditional travelling wave ranging,
Range error is larger.Therefore, research selects the urban electric power of more preferably signal processing method, design unrelated velocity of wave and zero _exit
Cable fault localization method is very necessary.
Summary of the invention
In order to realize the quick and precisely positioning of current urban electric power cable fault, the purpose of the present invention is to propose to one kind to be based on
The urban electric power cable Two-terminal Fault Location method of VMD-Hilbert transformation.
To achieve the above object, the technical solution adopted by the present invention are as follows:
A kind of city cable Two-terminal Fault Location method based on VMD-Hilbert transformation, includes the following steps:
(1) cable head and end measurement point is respectively indicated with head end M point and end N point, F point indicates fault point;Electric power electricity
After cable line failure, head end M point and end N point primary current travelling wave signal are extracted respectively, phase moding then is carried out to it
It changes, obtains original line mould current failure travelling wave signal, be denoted as respectivelyWherein subscript M indicates head end M point, subscript N table
Show that end N point, subscript (1) indicate line mould;
(2) the original line mould current traveling wave signal that head end M point and end N point measure is obtainedUtilize variation mould
It is series of discrete modal components that state, which decomposes (VMD) for signal decomposition,;
(3) Hilbert transformation is carried out to first modal components obtained after the signal decomposition of both ends respectively, is obtained corresponding
T/F relational graph, the time that the high frequency demarcated in time-frequency figure sports the fault initial wave head arrival both ends M, N are denoted as respectively
(4) judged by the polarity examination of each modulus maximum in variation mode decomposition (VMD) afterwards first modal components
The wavefront for reaching the both ends M, N is reflected through fault point, is found out the wave head corresponding high frequency mutation and is occurred the moment and is denoted as respectively
(5) obtained wave head arrival time is substituted into following equation (1), (2)
Wherein, L indicates half wavelength line overall length;
(6) D that will be obtainedMF1、DMF2Substitute into the distance D that following equation (3) calculate accurate fault distance endpoint MMF。
The invention has the advantages that:
VMD-Hilbert is converted signal analysis method and both-end TRAVELING WAVE FAULT LOCATION connected applications to electric power by the present invention
Cable run.Only need the line mould signal for decaying weaker in measurement communication process, fault localization formula used not by velocity of wave shadow simultaneously
It rings.Range error caused by avoiding because of the uncertain measurement with its zero _exit of velocity of wave in power cable.In power cable line
In have good engineering practice value.
Specific embodiment
The embodiment of the present invention is provided below with reference to attached drawing, and technical solution of the present invention is carried out into one by embodiment
Clear, the complete explanation of step.Obviously, the embodiment is only a part of the embodiments of the present invention, rather than whole implementation
Example.
As shown in Fig. 2, a kind of city cable Two-terminal Fault Location method based on VMD-Hilbert transformation, including it is as follows
Step:
(1) cable head and end measurement point is respectively indicated with head end M point and end N point, F point indicates fault point;Electric power electricity
After cable line failure, head end M point and end N point primary current travelling wave signal are extracted respectively, phase moding then is carried out to it
It changes, obtains original line mould current failure travelling wave signal, be denoted as respectivelyWherein subscript M indicates head end M point, subscript N table
Show that end N point, subscript (1) indicate line mould;
(2) the original line mould current traveling wave signal that head end M point and end N point measure is obtainedUtilize variation mould
It is series of discrete modal components that state, which decomposes (VMD) for signal decomposition,;
(3) Hilbert transformation is carried out to first modal components obtained after the signal decomposition of both ends respectively, is obtained corresponding
T/F relational graph, the time that the high frequency demarcated in time-frequency figure sports the fault initial wave head arrival both ends M, N are denoted as respectively
(4) judged by the polarity examination of each modulus maximum in variation mode decomposition (VMD) afterwards first modal components
The wavefront for reaching the both ends M, N is reflected through fault point, is found out the wave head corresponding high frequency mutation and is occurred the moment and is denoted as respectively
(5) obtained wave head arrival time is substituted into following equation (1), (2)
Wherein, L indicates half wavelength line overall length;
(6) D that will be obtainedMF1、DMF2Substitute into the distance D that following equation (3) calculate accurate fault distance endpoint MMF。
Various methods involved in the present invention are as follows:
1. the initial wave head recognition methods of line fault pressure-wire mould
After power cable line breaks down, the current traveling wave that fault point generates can reach both ends measurement point along route.
Signal decomposition is series of discrete modal components first with variation mode decomposition (VMD) by this method, is obtained to after signal decomposition
To first modal components carry out Hilbert transformation respectively, obtain corresponding T/F relational graph, demarcate in time-frequency figure
First high frequency sport fault initial wave head reach both ends time.
2. the method for line fault point reflection wave head
After being decomposed by VMD, n-th modulus maximum polarity in first modal components for the first time with first mould pole
Big value polarity is identical, then in the transformed time-frequency figure of Hilbert, as fault point is anti-at the time of the mutation of n-th high frequency is corresponding
Ejected wave head arrival time.
Simulating, verifying
In order to verify effectiveness of the invention and reliability, power cable line model is built on PSCAD/EMTDC, such as
Shown in Fig. 1.Using the circuit model for meeting practical line mould frequency dependent character, using three-core cable model, voltage class 6KV.Cause
It is the most common short trouble for single-phase grounding fault, accounts for about the 70% of total failare, so failure of the present invention is set as single
Phase ground short circuit failure.Route head end and end are equipped with current traveling wave measuring device, respectively in different fault distances, failure
Fault simulation emulation is carried out under the influence of resistance, payload size.According to context of methods, relevant parameter is calculated using MATLAB software
And fault distance.Fault localization error e is defined by the formula:
In above formula, XcFor the fault distance being calculated, XrFor physical fault distance, L=10km is total line length.Therefore
It is as shown in table 1 below to hinder location Calculation result.As space is limited, in table 1 fault distance be distance line head end M point distance.Under
In table 1, S is bearing power, and RFL is physical fault distance, RfFor fault resstance.
Fault location calculated result in the case of 1 different faults of table
The above is only a preferred embodiment of the present invention, it should be pointed out that: for the ordinary skill people of the art
For member, various improvements and modifications may be made without departing from the principle of the present invention, these improvements and modifications are also answered
It is considered as protection scope of the present invention.