CN101192752B - High-voltage arc grounding recognition method based on spectrum analysis - Google Patents

Abstract

The invention relates to a method for recognizing high voltage arc light grounding based on spectrum analysis. The method conducts instantaneous sampling at multipoint for a three phase voltage waveform, and calculates the voltage virtual value by time domain. The method also conducts the fast Fourier transformation (FFT) for the sampled time domain waveform, calculates the Fourier series in the frequency domain to calculate general waveform distortion content, so as to make sure whether high voltage arc light grounding is generated or not. The invention solves the technical problem in which the time domain analysis method fails to identify high voltage arc light grounding accurately and provides a more advanced method for recognizing high voltage arc light grounding.

Description

High pressure arc light ground recognition method based on spectrum analysis

Technical field

The invention belongs to electric field, more specifically, relate to the arc grounding recognition methods of high-voltage fence, particularly a kind of high pressure arc light ground recognition method based on spectrum analysis.

Background technology

In China 6-35kV electric power system, major part is an isolated neutral system, during this system generation single-phase earthing, the electrical network certain hour (being generally 0.5-2 hour) that still can operate with failure, this just greatly reduces operating cost, improved the reliability of electric power system, but this supply power mode is easy to generate unsettled arc grounding, promptly the electric arc of earth point is that intermittence ground extinguishes and restrikes.Owing to have electric capacity and inductance in the system, very easily vibrate, at electrical network mutually sound and fault mutually on the very high overvoltage of meeting generation.This overvoltage spread area is wider, and longer duration can cause great harm to power supply unit.In addition, place, arc grounding fault point electric arc local temperature is very high, causes short circuit and fire hazard easily.

In recent years, domestic engineering circle proposes a kind of new extinguishing arc and overvoltage protection notion on the basis of the various arc suppression coils of research; promptly when arc grounding occurring; by one group can phase-splitting the vacuum contactor or the circuit breaker of control, make fault phase metal ground connection, reach the purpose of thorough elimination arc light.This kind equipment is the indispensable down overvoltage protective device of the comparatively abominable mine of some environment, Lime Factory and dust, smog, wet condition.And the prerequisite of this equipment operate as normal is that to analyze electrical network in time, exactly unusual, the arc grounding of identification fault phase.

In the prior art, the amplitude of three-phase voltage when analyzing arc grounding normally, other amplitude of two-phase normal phase waveform that comprises the undesired phase waveform that produces arc grounding and arc grounding do not take place is judged definite.It is only judged from the amplitude of voltage waveform, so can only to ambiguous doubtful voltage arc grounding carry out " reconnaissance by firing " one by one with doubtful use the direct ground connection of short circuit metal method mutually after, spending several seconds disconnects again, thereby judge whether arc grounding is eliminated, if eliminate, then former doubtful be that instantaneous non-arc grounding disturbs mutually, if still existence, then be judged to arc grounding, must once more fault be used metal ground connection mutually.This method abbreviates temporal analysis as.

Though temporal analysis can reflect actual condition to a certain extent, but during owing to break down, situation is ever-changing, the waveforms amplitude that causes is also far from each other, sometimes fault phase waveform amplitude is higher than or near the normal phase waveforms amplitude, but fault phase waveform amplitude again may be less than the normal phase amplitude sometimes.Therefore, in real work, it is inadequate only relying on the time domain analysis method, and accuracy is not high.

Summary of the invention

The temporal analysis just that the present invention will solve provides a kind of more advanced high pressure arc light ground recognition method to the not accurate enough technical problem of the identification of high pressure arc grounding.

The inventor finds in practice, when arc grounding takes place, certainly leads to the non-linear high frequency arc light that frequency is higher than 50 hertz far away.And work as electrical network just often, the fundamental frequency of its voltage is generally about 50 hertz.Based on this principle, the technical solution used in the present invention is such:

High pressure arc light ground recognition method based on spectrum analysis, it is the instantaneous sampling that the three-phase voltage waveform is carried out many time points, and by the time domain operation calculate its voltage effective value, it is characterized in that: it also carries out rich fast reason leaf transformation to the time domain waveform of gathering, calculate the Fu Shi progression in the frequency domain, calculate total wave distortion content with this, thereby determine whether to produce the high pressure arc grounding.

Further, the high pressure arc light ground recognition method based on spectrum analysis comprises the steps:

A gathers three-phase voltage with the mode of instantaneous sampling, in the fixing collection 2 of each wave period ^MA power data, wherein the M value is an integer;

B to the data that collect, goes out the real effective of each phase voltage and voltage transformer open delta voltage with the root-mean-square value algorithm computation, and the Mathematical Modeling of its computing is seen formula 1;

C, to the voltage waveform of power frequency period sampling N time and through rich reason leaf transformation fast, calculate the interior Fu Shi progression of frequency domain, the Mathematical Modeling of its computing is seen formula 2;

D calculates total wave distortion content, and the Mathematical Modeling of its computing is seen formula 3;

E is as total wave distortion U of a certain phase _THD〉=40% and the voltage magnitude U of this phase _RMSBe lower than other two-phases, judge that then this is the fault phase mutually;

$U_{\mathrm{RMS}}=\sqrt{1/N\underset{K=1}{\overset{\mathrm{<figure-callout\; id="2"\; label="N\; U\; K"\; filenames="H061F4933120061220E000011.png"\; state="\{\{state\}\}">N</figure-callout>}}{\mathrm{\&Sigma;}}}{U}_K^{}{}_2^{}}$ Formula 1

In the formula 1: U _RMS... ... real available value of voltage

U _K... ... ... the aanalogvoltage sampled instantaneous value

N................ phase sampling number weekly

$U=U_O+\underset{n=1}{\overset{N/2}{\mathrm{\&Sigma;}}}\mathrm{UnmSin}(\mathrm{n\&omega;}+\mathrm{\&Phi;n})$ ... ... ... ... formula 2

In the formula 2: U............... time domain voltage analog

U _O... .... DC component

Unm............ the sinusoidal wave peak value of nth harmonic

Ф n.............. nth harmonic initial phase angle

N............... phase sampling number weekly

$U_{\mathrm{THD}}=\sqrt{\underset{K=1}{\overset{N/2}{\mathrm{\&Sigma;}}}{\mathrm{<figure-callout\; id="2"\; label="U\; K"\; filenames="H061F4933120061220E000011.png"\; state="\{\{state\}\}">U</figure-callout>}}_K^{}}/U_1\&times;100<figure-callout\; id="3"\; label="\%\; Formula"\; filenames="H061F4933120061220E000011.png"\; state="\{\{state\}\}">\%</figure-callout>$ Formula 3

In the formula 3: U _THD... ... ... ... voltage waveform distortion content

U _K... ... ... ... the K time voltage harmonic amplitude

U ₁... ... ... ... the fundamental voltage amplitude

From formula 1 as can be known, for voltage, phase sampling N point weekly is with every bit numerical value U _KAdd again after square and add up, to adding up and extracting square root again afterwards divided by N.Thus, can embody measured real effective.This processing method precision is high and not influenced by Harmonic Interference.

When mutually arc grounding taking place, fault all can distort with non-fault waveform mutually mutually when a certain, but aberration rate has nothing in common with each other, in the present invention, as main basis for estimation, be to

From formula 2 as can be known, for N time-domain sampling signal, after the FFT processing, can obtain N corresponding frequency samples.0-N/2 represents the 0-N/2 subharmonic respectively in the formula.All the other half conjugation for the former.

Further, the M=7 among the step a, promptly the phase is gathered 128 points weekly; Simultaneously, adopt phase-locked loop hardware synchronization Sampling techniques, the phase that can guarantee is weekly just in time adopted full 128 data.

In step a, gather the data in 4 cycles at every turn, get its mean value then.

Original temporal analysis, only the amplitude from voltage waveform judges whether to take place arc grounding, therefore needs rule of thumb, set three-phase voltage U a artificially, Ub, the different limit values of the opening voltage U Δ of Uc and PT, when voltage exceeds limit value, judge arc grounding has taken place.But only analyze from waveforms amplitude, non-arc grounding is to be difficult to difference on amplitude with arc grounding.

The present invention is based on frequency-domain analysis, is auxilliaryly to judge that analysis result is more short and sweet with each phase voltage waveform amplitude of time domain analysis, have disturbed little, advantage accurately rapidly.When the time domain instantaneous sampling, gather 4 cycles at every turn, average then, can suppress the spike of line voltage effectively and disturb.

Description of drawings

Fig. 1 is a FB(flow block) of the present invention.

Fig. 2 is the system block diagram of hardware of the present invention.

Fig. 3 is arc grounding over-voltage waveform figure in the documents and materials.

Fig. 4 a is the three-dimensional coordinate analysis diagram of the embodiment of the invention.

Fig. 4 b is the spectrum curve histogram of the embodiment of the invention.

Embodiment

Referring to Fig. 1.Behind system initialization 1, the three-phase voltage waveform is carried out weekly phase 128 instantaneous sampling, and calculate its voltage effective value 2, can judge according to switching value numerical value therebetween, fuse failure 3 whether, according to the effective value calculated value, can judge whether PT broken string 4, metal ground connection 5, then through FFT computing 6, in frequency domain, judge whether arc grounding 7, if transfinite, read in clock afterwards, start to do instruction 8, after waiting for a period of time, and try to recover action 9, the calculating voltage effective value of sampling once more, each phase FFT10, judge whether to transfinite 11 once more according to result of calculation,, enter the handling procedure 12-14 that transfinites if also transfinite.

Fig. 2 is the hardware system block diagram of the present invention's one specific embodiment.Wherein, the input analog signal has 4, is respectively three-phase voltage U a, Ub, U _cWith voltage transformer open delta voltage U Δ, the input switch amount has 6, is respectively three-phase disconnecting link signal and three-phase fuse alarm signal.In Fig. 2, the each several part relation of connecting is; Three-phase voltage 201, voltage transformer open delta voltage 202, totally 4 analog signals after preamplifier and A/D conversion 204, are sent into singlechip microcontroller 205; In addition, fuse and disconnecting link signal 203 (switching value) directly enter singlechip microcontroller 205 input interfaces; The other functional module that links with singlechip microcontroller 205 has: real-time clock 207; RS232/485/GPRS communication interface 208; Output executive's interface 09.Human-computer dialogue parameter setting 2010; LCD display 2011.

Fig. 3 comes from " for the distribution safe practice ", and Mu Longhua, Meng Qinghai write, China Machine Press's in August, 2003 version.This figure is arc grounding over-voltage waveform figure, is the typical arc grounding over-voltage waveform of record under the different electrical network parameters among the figure.Arc grounding when test, all carry out on mutually at electrical network A.Voltage waveform is respectively C, B, A phase from top to bottom among the figure, and next bar in four lines is the neutral point voltage to earth, and wherein going up several the 3rd curves is the arc grounding phase.

As seen from Figure 3, if only analyze from waveforms amplitude, the more non-arc discharge of amplitude that only shows the arc grounding phase is mutually for low, and both are difficult to difference.

Oscillogram a) is carried out quick Fourier (FFT) computing of formula 2 and total irregularity of wave form THD computing of formula 3 to Ua, Ub, Uc three-phase voltage during according to the arc discharge among Fig. 3.

Draw respectively as table 1, table 2, the listed three groups of spectrum curve numerical value of table 3.

This shows, for arc discharge phase a mutually and the non-arc discharge of other two-phase mutually b phase and c mutually, widely different on the numerical value of frequency spectrum computing, wherein the most tangible performance is exactly the THD numerical value of Ua phase, be far longer than other two-phase.Three-phase numerical value when simultaneously, the THD value of these three groups of data also is far longer than non-arc discharge.Ua-THD Ub-THD Uc-THD table 1Ua harmonic wave

h	1	5	7	11	13	17	19	23	25
										Ua h (％)	100	24.5	45.2	56.7	38.4	36.2	23.9	14.5	10.9
h	29	31	35	37	41	43	47	49	％THD I
										Ua h (％)	6.7	7.8	6.5	7.0	4.3	3.2	4.0	1.6	121.7

[0049]Table 2Ub harmonic wave

h	1	5	7	11	13	17	19	23	25
										Ubh(％)	100	24.7	7.5	5.1	2.9	1.8	1.6	0.9	0.7
h	29	31	35	37	41	43	47	49	％THD 1
										Ubh(％)	0.6	0.6	0.4	0.3	0.2	0.4	0.2	0.2	27.52

Table 3Uc harmonic wave

h	1	5	7	11	13	17	19	23	25
										Uch (％)	100	26.7	7.8	5.4	3.4	1.8	1.7	0.9	0.8
h	29	31	35	37	41	43	47	49	％THD 1
										Uch (％)	0.7	0.6	0.4	0.4	0.3	0.3	0.2	0.2	28.69

Annotate: Yin Biaoge limits, and goes back some harmonic value in the table 1,2,3 and does not list.

Referring to Fig. 4 a, Fig. 4 b.From frequency domain, the time domain waveform of a distortion can be decomposed into the histogram that contains n high order harmonic component; Obviously, compare with the time domain determination methods, frequency-domain analysis is more short and sweet.

Claims (3)

1. based on the high pressure arc light ground recognition method of spectrum analysis, it is the instantaneous sampling that the three-phase voltage waveform is carried out many time points, and by the time domain operation calculate its voltage effective value; It also carries out rich fast reason leaf transformation to the time domain waveform of gathering, calculate the Fu Shi progression in the frequency domain, calculate total wave distortion content with this, thereby determine whether to produce the high pressure arc grounding, it is characterized in that: specifically comprise the steps:

A gathers three-phase voltage with the mode of instantaneous sampling, in the fixing collection 2 of each wave period ^MA power data, wherein the M value is an integer;

B to the data that collect, goes out the real effective of each phase voltage and voltage transformer open delta voltage with the root-mean-square value algorithm computation, and the Mathematical Modeling of its computing is seen formula 1;

C, to the voltage waveform of power frequency period sampling N time and through rich reason leaf transformation fast, calculate the interior Fu Shi progression of frequency domain, the Mathematical Modeling of its computing is seen formula 2;

D calculates total wave distortion content, and the Mathematical Modeling of its computing is seen formula 3;

E is as total wave distortion U of a certain phase _THD〉=40% and the voltage magnitude U of this phase _RMSBe lower than other two-phases, judge that then this is the fault phase mutually;

Formula 1

In the formula 1: U _RMS... ... real available value of voltage

U _K... ... ... the aanalogvoltage sampled instantaneous value

N................. phase sampling number weekly

... ... ... ... formula 2

In the formula 2: U............... time domain voltage analog

U _O... .... DC component

Unm............ the sinusoidal wave peak value of nth harmonic

Φ n.............. nth harmonic initial phase angle

N............... phase sampling number weekly

Formula 3

In the formula 3: U _THD... ... ... voltage waveform distortion content

U _K... ... ... ... the K time voltage harmonic amplitude

U ₁... ... ... ... the fundamental voltage amplitude.

2. method as claimed in claim 2 is characterized in that: the M=7 among the step a, and promptly the phase is gathered 128 points weekly; Simultaneously, adopt phase-locked loop hardware synchronization Sampling techniques, the phase that can guarantee is weekly just in time adopted full 128 data.

3. method as claimed in claim 2 is characterized in that: in step a, gather the data in 4 cycles at every turn, get its mean value then.

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