CN104914352A - NUGS single-phase grounding fault location method based on harmonic difference distinguishing - Google Patents

Abstract

Provided is an NUGS single-phase grounding fault location method based on harmonic difference distinguishing. When a fault occurs, a sampling request is sent to all fault indicators, current signals in a period before the occurrence of the fault and in a period after the occurrence of the fault are recorded, and the recorded current signals are decomposed into direct-current components, fundamental harmonics and higher harmonics through FFT transform. The higher harmonics are retained, and subtraction operation is carried out on the content value of harmonic acquired by each fault indicator and the content value of harmonic of the same order acquired by the following fault indicator to form a matrix deltaU of operation results corresponding to all harmonics. The maximum values of all lines of the matrix deltaU are selected line by line to form a difference matrix deltaUmax. A line section which goes out the most in the deltaUmax is judged as a faulty section. The fault location method provided by the invention is simple in structure and easy to implement, and the deployment cost of complete equipment can be reduced greatly. The original grounding property of a distribution network is not changed, and the reliability of a distribution network of a small-current grounding system is not reduced. Moreover, injection of additional non-stationary signals is not needed, and the risk to safe and stable operation of the distribution network is not increased.

Description

A kind of NUGS method for locating single-phase ground fault differentiated based on harmonic wave difference

Technical field

The invention belongs to distribution network failure field of locating technology, especially design a kind of small current neutral grounding system based on harmonic wave diagnostic method (NUGS) method for locating single-phase ground fault.

Background technology

Neutral point not solidly grounded system is widely used in the power distribution network of below 66kV, and the power distribution network advantage of this form is its high reliability of powering, and especially can operate with failure in short-term under singlephase earth fault situation.But the current characteristic of single-phase fault is very not obvious in this type of power distribution network, cannot be fixed a breakdown by the means of trip protection, be merely able under the prerequisite selecting fault wire, utilize fault detector to make an inspection tour investigation trouble spot along the line.

At present, the fault detector implementation method that technology is comparatively ripe comprises " S injection method " and " middle electric-resistivity method ", and both to some extent solve the problem of localization of fault difficulty.But the former realization needs additional high-pressure Coupling device, hardware investment higher and to high resistant and electric arc jitterbug insensitive; The latter is also higher to the requirement of auxiliary hardware devices, and its enforcement simultaneously destroys the original neutral ground character of power distribution network.Both all belong to active location method, need initiatively in electrical network, to inject non-stationary signal, to the safe and stable operation of power distribution network and unfavorable.

Summary of the invention

The object of the invention is, for overcoming the defect of existing fault detector implementation algorithm, the present invention adopts a kind of passive algorithm, namely utilize single-phase fault that the moment occurs, the otherness feature of the high-frequency harmonic feature that power distribution network itself produces content before and after trouble spot, proposes a kind of NUGS method for locating single-phase ground fault differentiated based on harmonic wave difference targetedly.

For solving above-mentioned technical matters, the present invention by the following technical solutions:

Based on a single-phase grounded malfunction in grounded system of low current localization method for harmonic wave difference diagnostic method, comprise the following steps:

1, be distributed at a certain distance on faulty line by several fault detectors, indicator should be able to measure three-phase current; Be deployed on bus by comprehensive distinguishing unit, this comprehensive distinguishing unit should be able to measure three-phase voltage, and can carry out simple information interaction with every platform fault detector.

2, comprehensive distinguishing unit measures bus three-phase voltage in real time, drops to below 0.8pu, other two-phases are raised to more than 1.2pu for according to determining fault initial time and fault phase, and send sample request to all fault detectors with single-phase voltage.

3, each fault detector measures phase current in real time, and the current signal of a period of time before and after the moment occurs record trouble after receiving comprehensive distinguishing unit requests, and length is that each two cycles before and after the moment occur fault.

4, each fault detector utilizes FFT to convert and the current signal of record in step 3 is decomposed into DC component, first-harmonic and higher hamonic wave, and wherein higher hamonic wave comprises the harmonic wave of secondary to seven time.

5, the DC component in step 4 and first-harmonic is given up; From the fault detector near bus, the frequency domain transformation results of the time-domain signal that this TV station fault detector obtains is subtracted each other with immediately following fault detector homogeneous harmonic conversion result thereafter, form the matrix Δ U of the operation result corresponding to each harmonic.Namely

$\mathrm{\ΔU}=\left[\begin{array}{cccc}\mathrm{\Δ}{M}_{1-2}^2& \mathrm{\Δ}{M}_{2-3}^2& ...\mathrm{\Δ}{M}_{(j-1)-j}^2...& \mathrm{\Δ}{M}_{(k-1)-k}^2\\ \mathrm{\Δ}{M}_{1-2}^3& \mathrm{\Δ}{M}_{2-3}^3& ...\mathrm{\Δ}{M}_{(j-1)-j}^3...& \mathrm{\Δ}{M}_{(k-1)-k}^3\\ .& & & \\ .& & & \\ .& & & \\ \mathrm{\Δ}{M}_{1-2}^7& \mathrm{\Δ}{M}_{2-3}^7& ...\mathrm{\Δ}{M}_{(j-1)-j}^7...& \mathrm{\Δ}{M}_{(k-1)-k}^7\end{array}\right]$

In subscript, operational symbol "-" represents the difference of the harmonic content value of two adjacent fault detectors; K represents total number of units of the fault detector that target line is disposed, M _jfor distribution fault detector on the line.M _(j-1)-jfor the part of path between adjacent two fault detectors.If singlephase earth fault F occurs in M ₂and M ₃between, now corresponding fault wire section is M _2-3.

6, choose the row maximum value of matrix Δ U line by line, and form matrix of differences $\mathrm{\Δ}{U}_{\max }={\left[\begin{array}{cccc}\mathrm{\Δ}{M}_{(j-1)-j}^2& \mathrm{\Δ}{M}_{(j-1)-j}^3& ...& \mathrm{\Δ}{M}_{(j-1)-j}^7\end{array}\right]}^T,$ Each element represents the differentiation result of second harmonic to the seventh harmonic difference respectively.It differentiates that part of path corresponding to result is the faulty section that this subharmonic judges.

7, in step 6 matrix of differences, the maximum part of path of occurrence number, is fault wire section.

The invention has the beneficial effects as follows: proposed by the invention is simply easy to realize based on harmonic component Fault Locating Method, significantly can reduce the lower deployment cost of its set of equipments; Do not change the original ground property of power distribution network, do not reduce the advantage of low current grounding system power distribution network reliability; Simultaneously without the need to injecting non-stationary signal separately, do not increase the stable operation risk of power distribution network yet.

Accompanying drawing explanation

Fig. 1 is that the present invention tries routine line assumption diagram;

Fig. 2 is the invention process process flow diagram;

Fig. 3 is that fault phase differentiates logical diagram.

Embodiment

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.

Fig. 1 is after small current neutral grounding system breaks down, and certain faulty line chosen in advance by failure line selection technology determines the concrete position of fault for utilizing fault detector.M _jfor distribution fault detector on the line.M _(j-1)-1for the part of path between adjacent two measurement points.If singlephase earth fault F occurs in M ₂and M ₃between, now corresponding fault wire section is M _2-3.

Fig. 2 carries out the implementing procedure of localization of fault for the present invention under the power network wiring condition shown in Fig. 1: the small current neutral grounding system single-phase fault localization method differentiated based on harmonic wave difference, comprises the following steps:

1, comprehensive distinguishing unit Real-time Collection bus three-phase phase voltage signal, is designated as U _a, U _band U _c.If certain phase phase voltage drops to below 0.8pu, simultaneously in addition two-phase rises to more than 1.2pu, and that is then fallen by voltage is separately judged as fault phase, as shown in Figure 3.Send sample command and the separate information of fault to each fault detector immediately simultaneously.

2, each two cycle data before and after faulted phase current collected immediately by each fault detector after receiving information.

3, each fault detector utilizes FFT conversion that the signal decomposition of intercepting is become DC component, first-harmonic and higher hamonic wave.

4, retain higher hamonic wave, and from second harmonic, to the seventh harmonic, form the matrix U of each harmonic content value that each fault detector records, namely

$U=\left[\begin{array}{cccc}{M}_1^2& M_2^2& ...M_j^2...& M_k^2\\ M_1^3& M_2^3& ...M_j^3...& M_k^3\\ .& & & \\ .& & & \\ .& & & \\ M_1^7& M_2^7& ...M_j^7...& M_k^7\end{array}\right]$

In formula represent the nth harmonic content value that jth platform fault detector records.K is the total quantity of fault detector on the line of distributing

5, from the fault detector near bus, the frequency domain transformation results of the time-domain signal that this TV station fault detector obtains is subtracted each other with immediately following fault detector homogeneous harmonic conversion result thereafter, obtains $\mathrm{\Δ}{M}_{(j-1)-j}^n(2\≤n\≤7).$ That is:

$\mathrm{\Δ}{M}_{(j-1)-j}^n=|M_{j-1}^n-M_j^n|$

And form each harmonic matrix Δ U.Namely

$\mathrm{\ΔU}=\left[\begin{array}{cccc}\mathrm{\Δ}{M}_{1-2}^2& \mathrm{\Δ}{M}_{2-3}^2& ...\mathrm{\Δ}{M}_{(j-1)-j}^2...& \mathrm{\Δ}{M}_{(k-1)-k}^2\\ \mathrm{\Δ}{M}_{1-2}^3& \mathrm{\Δ}{M}_{2-3}^3& ...\mathrm{\Δ}{M}_{(j-1)-j}^3...& \mathrm{\Δ}{M}_{(k-1)-k}^3\\ .& & & \\ .& & & \\ .& & & \\ \mathrm{\Δ}{M}_{1-2}^7& \mathrm{\Δ}{M}_{2-3}^7& ...\mathrm{\Δ}{M}_{(j-1)-j}^7...& \mathrm{\Δ}{M}_{(k-1)-k}^7\end{array}\right]$

6, choose the row maximum value of matrix Δ U line by line, and form matrix of differences Δ U _max, that is:

$\mathrm{\Δ}{U}_{\max }={\left[\begin{array}{cccc}\mathrm{\Δ}{M}_{(j-1)-j}^2& \mathrm{\Δ}{M}_{(j-1)-j}^3& ...& \mathrm{\Δ}{M}_{(j-1)-j}^7\end{array}\right]}^T$

Wherein represent the maximal value of difference in nth harmonic.Part of path corresponding to this value is the fault segment occurred judged by nth harmonic, using this faulty section as the differentiation result produced by this subharmonic.

7, differentiate in result at n-1 that produces, adopt the principle of " the minority is subordinate to the majority ".Part of paths maximum for outlet number of times is judged to be the section that trouble spot occurs.

The above is preferred embodiment of the present invention, but the present invention should not be confined to the content disclosed in this example and accompanying drawing.The equivalence completed under not departing from spirit disclosed in this invention so every or amendment, all fall into the scope of protection of the invention.

Claims (2)

1. the NUGS method for locating single-phase ground fault differentiated based on harmonic wave difference, it is characterized in that, utilize single-phase fault that the moment occurs, the otherness feature of the high-frequency harmonic that power distribution network itself produces content before and after trouble spot, proposes a kind of localization method of the single-phase grounded malfunction in grounded system of low current based on the differentiation of harmonic wave difference targetedly;

Said method comprising the steps of:

(1) be distributed at a certain distance on faulty line by several fault detectors, indicator should be able to measure three-phase current; Be deployed on bus by comprehensive distinguishing unit, described comprehensive distinguishing unit should be able to measure three-phase voltage, and can carry out simple information interaction with every platform fault detector;

(2) comprehensive distinguishing unit measures bus three-phase voltage in real time, drops to below 0.8pu, other two-phases are raised to more than 1.2pu for foundation, determine fault initial time and fault phase, and send sample request to all fault detectors with single-phase voltage;

(3) each fault detector measures phase current in real time, and the current signal of a period of time before and after the moment occurs record trouble after receiving comprehensive distinguishing unit requests, and length is that each two cycles before and after the moment occur fault;

(4) each fault detector utilizes FFT to convert and the current signal of record in step (3) is decomposed into DC component, first-harmonic and higher hamonic wave, and wherein higher hamonic wave comprises the harmonic wave of secondary to seven time;

(5) DC component in step (4) and first-harmonic is given up; From the fault detector near bus, the frequency domain transformation results of the time-domain signal that this TV station fault detector obtains is subtracted each other with immediately following fault detector homogeneous harmonic conversion result thereafter, form the matrix Δ U of the operation result corresponding to each harmonic; That is:

$\mathrm{\ΔU}=\left[\begin{array}{cccccc}{\mathrm{\ΔM}}_{1-2}^2& {\mathrm{\ΔM}}_{2-3}^2& ...& {\mathrm{\ΔM}}_{(j-1)-j}^2& ...& {\mathrm{\ΔM}}_{(k-1)-k}^2\\ {\mathrm{\ΔM}}_{1-2}^3& {\mathrm{\ΔM}}_{2-3}^3& ...& {\mathrm{\ΔM}}_{(j-1)-j}^3& ...& {\mathrm{\ΔM}}_{(k-1)-k}^3\\ .& & & & & \\ .& & & & & \\ .& & & & & \\ {\mathrm{\ΔM}}_{1-2}^7& {\mathrm{\ΔM}}_{2-3}^7& ...& {\mathrm{\ΔM}}_{7j-1)-j}^7& ...& {\mathrm{\ΔM}}_{(k-1)-k}^7\end{array}\right]$

In formula, in subscript, operational symbol "-" represents the difference of the harmonic content value of two adjacent fault detectors; K represents total number of units of the fault detector that target line is disposed, M _jfor distribution fault detector on the line.M _(j-1)-jfor the part of path between adjacent two fault detectors; If singlephase earth fault F occurs in M ₂and M ₃between, now corresponding fault wire section is M _2-3;

(6) choose the row maximum value of matrix Δ U line by line, and form matrix of differences ${\mathrm{\ΔU}}_{\max }={\left[\begin{array}{cccc}{\mathrm{\ΔM}}_{(j-1)-j}^2& {\mathrm{\ΔM}}_{(j-1)-j}^3& ...& {\mathrm{\ΔM}}_{(j-1)-j}^7\end{array}\right]}^T,$ Each element represents the differentiation result of second harmonic to the seventh harmonic difference respectively; It differentiates that part of path corresponding to result is the faulty section that this subharmonic judges;

(7) in step (6) matrix of differences, the maximum part of path of occurrence number, is fault wire section.

2. a kind of NUGS method for locating single-phase ground fault differentiated based on harmonic wave difference according to claim 1, it is characterized in that, described method gives clear and definite computing method to harmonic content difference, and according to phase current in bus measuring voltage and feeder line, give clear and definite criterion to the differentiation of faulty section.