CN1232834C - Online detection method for vacuum circuit breaker contact on-off time based on vibration analysis - Google Patents

Abstract

The present invention discloses an on-line detection method for the on-off moments of a vacuum circuit breaker contacts based on vibration analysis. The method comprises the following steps: 1, selecting the installation position and the installation direction of a vibration sensor; 2, setting a sampling order, a sampling frequency, a sampling length and a triggering mode and storing sampled data; 3, preprocessing vibration data; 4, selecting the type and the length of moving window functions and adopting a short time energy algorithm for analysis; 5, selecting a threshold value and confirming the on-off moments of the three-phase contacts; 5, calculating closing simultaneity and closing time according to the on-off moments of the three-phase contacts. The present invention analyzes the types and the lengths of the window functions and enhances the event identification capability and the interference rejection capability of vibration signal analysis through selecting the installation position and the short time energy of the vibration sensor so as to realize the detection of the on-off moments of the three-phase contact in an on-line state.

Description

Online test method based on the contacts for vacuum-break switches on-off time of vibration analysis

Technical field

The present invention relates to electrical technology field, relate in particular to a kind of online test method of the contacts for vacuum-break switches on-off time based on vibration analysis.

Background technology

The on-off time of vacuum circuit breaker three-phase contact is an important parameter describing its mechanical movement state.The calculating of many mechanical property parameters such as closing time, closing speed and switching synchronization all depends on determining of contact on-off time.The detection of this some ratio is easier under the off-line, generally all is to realize by add the auxiliary electrical loop on the three-phase fracture, and most breaker mechanic property proving installation of countries in the world development at present can both detect exactly to the contact on-off time under the zero load.Yet when isolating switch works in load condition following time, the three-phase contact is under the noble potential, therefore can't detect with electric approach traditional under the off-line.All be to utilize the stroke characteristic of moving contact probably to estimate the on-off time of contact in the isolating switch on-line monitoring in the past, error is bigger, and is very unfavorable to the computational accuracy that improves whole mechanical parameter.

Vibration analysis is a kind of detection method of non-intrusion type, because vibration transducer is installed in the grounded part of isolating switch, therefore is highly suitable for the status monitoring under the line situation, has obtained in recent years using comparatively widely.Isolating switch is in the breaking-closing operating process, because phase mutual friction and collision between inner each parts can produce the time series by a plurality of impact-attenuating wave components on the mechanism surface.Can determine the generation moment of different vibration events by the starting point of extracting these decaying waves.Accompanying drawing 2 is the vibration signals that arrive at mechanism's acquisition surface in the ZN12 type vacuum circuit breaker making process, has wherein comprised 6 typical vibration events: incident 1 is that making electromagnet bump closes a floodgate and holds up son and cause; Incident 2 is that cam and leverage collision cause; Incident 3,4,5th, the collision of three-phase contact causes in the making process; Incident 6 is that separating brake is held up the son motion collision when putting in place and caused.The method of existing definite vibration event zero-time comprises median filtering method, temporal envelope method, amplitude method and correlation method.These methods all are confined to analyze the single vibration event that can obviously distinguish owing to be subjected to the restriction of incident time resolution and antijamming capability in time domain, as the incident in the accompanying drawing 21, and incident 2 and incident 6.The three-phase contact of vacuum circuit breaker adopts same operating mechanism usually, and in making process, the vibration event that the collision of three-phase contact causes is very approaching in time, generally only poor each other several milliseconds (being switching synchronization).When the vibration wave that is produced propagates in the mechanism thus in time domain mutual superposition, and amplitude quite (incident 3 in the accompanying drawing 2, incident 4 and incident 5).Mix the vibration signal that forms for this by a plurality of incidents, traditional analytical approach can only obtain an initial moment, but on behalf of the vibration of which phase contact, this moment be difficult to know actually.When switching synchronization during in normal condition (in the allowed band of the maximum time difference of three-phase on-off time in normal operation of circuit breaker), approximately constantly replace on-off time of isolating switch to be fine with this; But when taking place than cataclysm because of the variation of mechanism's state, just must know the on-off time of three-phase contact respectively, could carry out correct assessment the mechanical movement state of isolating switch when switching synchronization.In the list of references at home and abroad, the relevant report of also vacuum circuit breaker three-phase contact on-off time not being carried out on-line measurement so far.

Summary of the invention

The object of the present invention is to provide a kind of online test method of the contacts for vacuum-break switches on-off time based on vibration analysis, in order to be implemented in the detection of vacuum circuit breaker three-phase contact on-off time under the line states.

Technical conceive of the present invention is: choose suitable vibration transducer installation site, the outstanding vibration signal of measuring the phase contact reduces the influence of other two-phase contact vibrations.The vibration signal of gathering is carried out the limit filtration pre-service, adopt the algorithm of short-time energy to extract the on-off time of each phase contact then.

The state-detection of isolating switch is an important content of intelligent electrical apparatus.In order to improve the serviceable life of vacuum circuit breaker, reduce its daily servicing expense, just must constantly improve the content of the online detection of mechanical property.The correctness of state-detection depends on the measuring accuracy of each mechanical parameter, and wherein, three-phase contact on-off time is extremely important for the calculating of combined floodgate parameter.From the prior art of above-mentioned isolating switch vibration detection, seek a kind of event time resolution characteristic height, method for detecting vibration that antijamming capability is strong is the key that realizes the online detection of three-phase contact on-off time.

Purpose of the present invention realizes by the following technical solutions: the online test method based on the contacts for vacuum-break switches on-off time of vibration analysis comprises the steps:

1) installation site and the installation direction of selection vibration transducer, the sensor installation site is the end P point that A, B, C three phase isolated pull bar and circuit interrupter grounding partly are connected, the vibration acceleration sensor of three same models of employing obtains the vibration signal of three-phase contact simultaneously, and installation direction is parallel with insulated tension pole;

2) set sampling order, sample frequency, sampling length and triggering mode and sampled data stored;

3) to the vibration data pre-service, the catastrophe point that adopts the limit filtration algorithm that noise in the vibration signal is caused is carried out smoothly;

4) choose the type and the length of mobile window function, adopt the short-time energy algorithm to analyze;

5) select threshold value, determine the on-off time of three-phase contact;

6) on-off time according to the three-phase contact calculates switching synchronization and closing time.

The order of above-mentioned setting sampling is A phase-B phase-C phase; Sample frequency is 〉=25kHz; Rising edge with the closing coil electric current starts sampling, and sampling length is the twice of breaker closing time.

Described limit filtration algorithm is as follows: the envelope of asking for the vibration signal absolute value earlier, by comparing the envelope amplitude y (n) and the y (n-1) of two sampled points of adjacent moment, if their difference has surpassed the amplitude limit value that sets, then think mutation disturbance has taken place, and look current sampled value x (n) for illegal value, rejected, and replaced x (n) with x (n-1); Amplitude limit value is by the maximum rate of change V of envelope at the vibration signal section start _MaxProduct decision with sampling period T.

Choose the type and the length of mobile window function, adopt the short-time energy Algorithm Analysis to be:

If oscillating sequence is x (i), i=0 ..., N-1, then short-time energy function S (n) is defined as:

$S\left(n\right)=\underset{i=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{x}^2\left(i\right)w(n-i)=\underset{i=n-M+1}{\overset{n}{\mathrm{\Σ}}}{x}^2\left(i\right)w(n-i)=x^2\left(n\right)*w\left(n\right)$

W in the formula (n), n=0 ..., M-1 is mobile window function, M is the length of window function.S (n) has represented the local energy of signal at moment n.Select the hamming window for use when analyzing vacuum circuit breaker combined floodgate vibration signal, when sample frequency was determined, the long M of window got 50～100.The hamming window function is defined as:

$w\left(n\right)=0.54-0.46\cos \left(\frac{2\mathrm{\πn}}{M-1}\right)$ 0≤n≤M-1

The threshold value range of choice is: first peak value (E in 0～vibration signal short-time energy analysis waveform _s) half.Thereby obtain the zero-time of three-phase contact vibration event, respectively the on-off time of each phase contact of corresponding isolating switch; If the short-time energy of outside noise analysis maximal value is N before the vibration event _Max, threshold T then _hBe chosen as:

$T_h=\left\{\begin{array}{cc}10\×N_{\max }& 10\×N_{\max }\≤0.5\×E_s\\ 0.5\×E_s& 10\×N_{\max }>0.5\×E_s\end{array}\right.$

Being calculated as follows of switching synchronization, closing time: judge that according to the sequencing of on-off time head closes phase and closes mutually with last closing, the mistiming between them is switching synchronization; With the moment that the starting point of coil current arrives as reclosing command, it and last mistiming of closing between the on-off time that closes phase are the closing time of isolating switch.

The present invention is applied to the thought of short-time energy in the analysis of vacuum circuit breaker combined floodgate vibration signal, by the installation site of choose reasonable vibration transducer and the time window function of short-time energy analysis, improve the event time resolution characteristic and the antijamming capability of analysis of vibration signal, thereby realized the detection of three-phase contact on-off time under the presence.

Description of drawings

Fig. 1 is a software processes process flow diagram of the present invention;

Vibration signal figure when Fig. 2 closes a floodgate for vacuum circuit breaker;

Fig. 3 is the front elevation of vacuum circuit breaker;

Fig. 4 is the installation site P point synoptic diagram of vibration transducer;

Fig. 5 is the influence figure of window function length M to the short-time energy analysis result;

Fig. 6 is the combined floodgate transposition signal and the combined floodgate vibration signal figure of vacuum circuit breaker three-phase contact;

Fig. 7 carries out the figure as a result that short-time energy is analyzed for the combined floodgate vibration signal to Fig. 6.

The switching synchronization that Fig. 8 obtains for analysis of vibration signal of the present invention and the comparative graph of actual value;

Embodiment

The present invention will be described in more detail below in conjunction with accompanying drawing.

The flow process of vibration signal processing software is as shown in Figure 1:

1) sets sampling order, sample frequency, sampling length and triggering mode;

2) gather vibration signal and storage;

3) absolute value of vibration signal is asked for envelope;

4) find out the position of noise catastrophe point and in original signal, make smoothing processing by the limit filtration algorithm;

5) choose the type and the length of window function;

6) adopt the short-time energy algorithm to analyze;

7) select suitable threshold value, determine the on-off time of vacuum circuit breaker;

8) calculate machine performance parameters such as switching synchronization, closing time and closing speed.

In order to obtain the on-off time of three-phase contact respectively, at first must reasonably select the installation site of vibration transducer.Referring to the vacuum circuit breaker front elevation of Fig. 3 and the vibration transducer installation site P point synoptic diagram of Fig. 4, at the four-bar mechanism that present vacuum circuit breaker generally adopts, the vibration acceleration sensor (inner integrated charge amplifier) of three same models of employing detects the vibration signal of three-phase contact simultaneously.The end that the selected insulated tension pole of the present invention and circuit interrupter grounding partly link to each other is as measuring position (in the accompanying drawing 4 shown in the P point), and installation direction is parallel with insulated tension pole.In order not destroy the insulating property of insulated tension pole itself, mounting means adopts the mode of epoxy resin stickup, obtains the vibration signal of each phase contact thus.Considered three factors when selecting the P point: one, this point is in the grounded part of isolating switch, meets the requirement of online detection; Its two because insulated tension pole promptly will be done translation and rotates again in making process, therefore this peripheral free space is bigger, is convenient to the installation of vibration transducer.Its three, this is nearest from vibration source of measuring the phase contact, and far away from the vibration source of all the other two-phase contacts, therefore can at utmost give prominence to the vibration signal of measurement phase contact.A large amount of contrast tests show that after buffering and decay through operating mechanism, the frequency of all the other two-phase contact vibration signals and amplitude all reduce greatly at this point, thereby highly beneficial to extracting the contact vibration event of measuring phase.

The signal that obtains from vibration transducer after the conversion through the sensor signal conditioning device, is collected in the computing machine by data collecting card and to handle.The mode that the collection of vibration data adopts external interrupt to trigger, look-at-me is produced by the closing coil electric current.From the rising edge of switching current, acquisition order A phase, B phase and C contact vibration signal mutually.Spectrum analysis shows that vacuum circuit breaker combined floodgate vibration signal main frequency component concentrates in the 10kHz, according to sampling thheorem, and considers certain nargin, and sample frequency can be made as 25kHz.Sampling length is the breaker closing time of twice.

In measurement, transmission and the recording process of test figure, be subjected to serious external interference sometimes suddenly, make and introduce some unusual catastrophe points in the signal of record.When these catastrophe points are concentrated, be equivalent to improve total noise level, thereby therefore the analysis of interfering data need carry out pre-service to the raw data of being gathered.Adopt the algorithm of limit filtration to find out the position at catastrophe point place in the software, in addition level and smooth in raw data then.The algorithm of limit filtration is as follows: by the envelope amplitude y (n) and the y (n-1) of more adjacent two sampled points, if their difference has surpassed the amplitude limit value that sets, then think mutation disturbance has taken place, and look current sampled value x (n) for illegal value, rejected, and replaced x (n) with x (n-1).Amplitude limit value is by the maximum rate of change V of envelope at the vibration signal section start _MaxProduct decision with sampling period T.

Pretreated signal adopts the algorithm of short-time energy to analyze, and establishing oscillating sequence is x (i), i=0 ..., N-1, then short-time energy function S (n) is defined as:

$S\left(n\right)=\underset{i=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{x}^2\left(i\right)w(n-i)=\underset{i=n-M+1}{\overset{n}{\mathrm{\Σ}}}{x}^2\left(i\right)w(n-i)=x^2\left(n\right)*w\left(n\right)$

W in the formula (n), n=0 ..., M-1 is mobile window function, M is the length of window function.S (n) has represented the local energy of signal at moment n.Can see that the short-time energy analysis is handled with the method for segmentation or the stack of branch frame then to the advanced row index conversion of signal.Divide the frame can be continuous, also can overlap, be weighted with finite length window movably and realize.

During on-the-spot the detection,, therefore from the signal that vibration transducer obtains, unavoidably there is a large amount of random noises because isolating switch is operated in the complex electromagnetic environments.Comprising the low-frequency interference signal that mechanism's parts move and friction is produced, the HF noise signal that also has shelf depreciation and arc discharge to cause.These undesired signals have very big randomness, and are very unfavorable to the extraction in the initial moment of contact vibration event.After original sampled signal was analyzed through short-time energy, the bigger useful signal of energy had been given prominence in square processing of signal, and the less noise signal of value then can be ignored.In addition, because impact signal has local continuity, all bigger in the value that begins to locate continuously some, and noise has randomness, the probability of what time getting higher value continuously is very low, so, thereby improved signal to noise ratio (S/N ratio) effectively through the further influence of attenuating noise of energy accumulation of window function.

Different window function (shape, length) will determine the result that short-time energy is analyzed.Therefore must select the type and the length of suitable window function at the characteristics of vibration signal.There are two kinds of window types commonly used available in the program: rectangular window and hamming window.Relative rectangular window, hamming window have bigger bandwidth and attenuation outside a channel speed faster, and be less to the distortion of input signal, therefore selected the hamming window for use in the process of processing vacuum circuit breaker combined floodgate vibration signal.Signal among extraction Fig. 2 near the incident 1 2ms scope is done the short-time energy analysis, referring to the window function length M of Fig. 5 the figure that influences to the short-time energy analysis result, horizontal ordinate is a time shaft among the figure, ordinate is short-time energy, article 4, the corresponding respectively hamming window function of curve length is 10,50,100 and 150 o'clock short-time energy analysis result, can see when sample frequency one timing T time lag that the long short more then short-time energy of window is analyzed _Di(i=1,2,3,4) more little, the event time that obtains is also more near actual value; Analyze the high characteristics of signal to noise ratio (S/N ratio) but be unfavorable for bringing into play simultaneously short-time energy again, must weigh both in the application and be selected.Under the sampling rate of 25kHz, it is 50～100 comparatively suitable to get through comparison window length repeatedly.Concrete window length depends on the form of the isolating switch vibration signal that obtains under the different site environments.When contained noise was more weak, choosing was long than short window, to reduce the time lag that short-time energy is analyzed; When contained noise is strong, select long window length to improve signal to noise ratio (S/N ratio).

Select suitable threshold value (first peak value (E in 0～vibration signal short-time energy analysis waveform according to the amplitude of vibration signal short-time energy analysis result and the power of noise _s) half).Thereby obtain the zero-time of three-phase contact vibration event, respectively the on-off time of each phase contact of corresponding isolating switch.If the short-time energy of outside noise analysis maximal value is N before the vibration event _Max, threshold T then _hFor:

$T_h=\left\{\begin{array}{cc}10\×N_{\max }& 10\×N_{\max }\≤0.5\×E_s\\ 0.5\×E_s& 10\×N_{\max }>0.5\×E_s\end{array}\right.$

Judge that according to the sequencing of on-off time head closes phase and closes mutually with last closing, the mistiming between them is switching synchronization.Joint line loop current curve, with the moment that the starting point of coil current arrives as reclosing command, it and last mistiming of closing between the on-off time that closes phase are the closing time of isolating switch.

Embodiment

The acceleration transducer that three models of employing are M353B18 in testing laboratory detects the combined floodgate vibration signal of ZN12 type vacuum circuit breaker.Measure the transposition signal of three-phase contact before this earlier with the method under the off-line, in order to the effect of checking vibration detection.Referring to the combined floodgate transposition signal and the combined floodgate vibration signal waveforms of ZN12 type vacuum circuit breaker three-phase contact shown in Figure 6, horizontal ordinate is a time shaft among the figure, X _a, X _b, X _cBe respectively that corresponding A, B, C three-phase contact are closed the vibration signal that closes, C _a, C _b, C _cIt is respectively the transposition signal of A phase in the making process, B phase, C phase contact.C is that head closes phase mutually as can be seen, be successively then A mutually with B mutually.Mistiming dt between B, the C two-phase has represented the switching synchronization of vacuum circuit breaker.

Vibration signal among Fig. 6 is carried out the short-time energy analysis, and referring to the oscillogram that ZN12 type vacuum circuit breaker combined floodgate vibration signal short-time energy shown in Figure 7 is analyzed, horizontal ordinate is a time shaft among the figure, S _a, S _b, S _cBe respectively the short-time energy analysis result of A, B, C three-phase contact vibration signal, and be that benchmark aligns on time shaft with the starting point of closing coil current i.Compare with original vibration signal, short-time energy is analyzed and has been improved signal to noise ratio (S/N ratio) greatly, makes the starting point of three-phase contact vibration event appear suddenly out significantly.Select suitable threshold value, thereby obtain the zero-time t of three-phase contact vibration event ₁, t ₂And t ₃, the on-off time of respectively corresponding each phase contact.t ₂-t ₃Represented the switching synchronization of isolating switch.The starting point of closing coil electric current is similar to the moment that reclosing command arrives, and B is that last closing closed phase so t mutually ₂Just represented the closing time of isolating switch.After having obtained the on-off time of isolating switch, in conjunction with the stroke curve of moving contact, equally can be in the hope of closing speed.In order to verify the stability of this method, under the identical mechanism state, made revision test five times, analysis result is as shown in table 1.

Absolute error between the contact transposition signal that data representation analysis result in table 1 bracket and off-line are measured down can see that maximum error is 0.2ms.The machine performance of this error against vacuum isolating switch detects, and has been enough to distinguish the change of the contact on-off time that causes owing to mechanism's state variation.When being used for the calculating of other mechanical parameter such as closing time, closing speed and switching synchronization, can reach the higher detection precision equally.

Referring to Fig. 8, for ZN12 type vacuum circuit breaker, open the distance and the excess of stroke by what the length of regulating insulated tension pole can be adjusted the three-phase contact, the three-phase synchronism also can change thereupon, therefore can be used for the variation of mimic-disconnecting switch switching synchronization.Regulate the length of C phase insulated tension pole in the test, every increase 2mm measures the vibration signal of a three-phase contact on the basis of original length.With the switching synchronization under every kind of state of vibration analysis method calculating of the present invention, the switching synchronization that obtains with the transposition of the contact under off-line signal is that actual value compares simultaneously, obtain switching synchronization and actual value comparative graph that vibration analysis shown in Figure 8 obtains, horizontal ordinate is the length of ZN12 type vacuum circuit breaker insulated tension pole among the figure, and ordinate is represented switching synchronization.

As seen from Figure 8, along with the growth of C phase insulated tension pole, the three-phase switching synchronization increases thereupon.And having kept good consistance by switching synchronization and the actual value that vibration analysis method calculates, maximum relative error is 4.3%.

The short-time energy analysis result that table 1 ZN12 type vacuum circuit breaker closes a floodgate and tests

Test number (TN)	t 1/ms	t 2/ms	t 3/ms	(t 2-t 3)/ms	(t 2-t 1)/ms
						1	66.04 (-0.01)	67.08 (-0.09)	65.34 (-0.09)	1.74 (0.00)	1.04 (-0.08)
2	66.08 (-0.01)	67.24 (-0.09)	65.70 (0.11)	1.54 (-0.20)	1.16 (-0.08)
						3	66.02 (-0.09)	67.18 (-0.09)	65.60 (0.11)	1.58 (-0.20)	1.16 (0.00)
4	66.08 (0.03)	67.16 (-0.05)	65.42 (-0.01)	1.74 (-0.04)	1.08 (-0.08)
						5	66.08 (0.07)	67.12 (-0.05)	65.34 (-0.05)	1.78 (0.00)	1.04 (-0.12)
Mean value	66.06	67.16	65.48	1.68	1.10

Claims (4)

1, a kind of online test method of the contacts for vacuum-break switches on-off time based on vibration analysis is characterized in that comprising the steps:

1) installation site and the installation direction of selection vibration transducer, the sensor installation site is the end P point that A, B, C three phase isolated pull bar and circuit interrupter grounding partly are connected, the vibration transducer of three same models of employing obtains the vibration signal of three-phase contact simultaneously, and installation direction is parallel with insulated tension pole;

2) set sampling order, sample frequency, sampling length and triggering mode and sampled data stored;

3) to the vibration data pre-service, the catastrophe point that adopts the limit filtration algorithm that noise in the vibration signal is caused is carried out smoothly;

Above-mentioned limit filtration algorithm is as follows:

Ask for the envelope of vibration signal absolute value earlier, by comparing the envelope amplitude y (n) and the y (n-1) of two sampled points of adjacent moment, if their difference has surpassed the amplitude limit value that sets, then think mutation disturbance has taken place, and look current sampled value x (n) for illegal value, rejected, and replaced x (n) with x (n-1); Amplitude limit value is by the maximum rate of change V of envelope at the vibration signal section start _MaxProduct decision with sampling period T;

4) choose the type and the length of mobile window function, adopt the short-time energy algorithm to analyze;

Above-mentioned short-time energy Algorithm Analysis is:

If oscillating sequence is x (i), i=0 ..., N-1, then short-time energy function S (n) is defined as:

$S\left(n\right)=\underset{i=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{x}^2\left(i\right)w(n-i)=\underset{i=n-M+1}{\overset{n}{\mathrm{\Σ}}}{x}^2\left(i\right)w(n-i)=x^2\left(n\right)*w\left(n\right)$

In the formula, w (n), n=0 ..., M-1 is mobile window function, M is the length of window function; S (n) has represented the local energy of signal at moment n; Select the hamming window for use when analyzing vacuum circuit breaker combined floodgate vibration signal, when sample frequency was determined, the long M of window got 50～100; The hamming window function is defined as:

$w\left(n\right)=0.54-0.46\cos \left(\frac{2\mathrm{\πn}}{M-1}\right),0\≤n\≤M-1;$

5) select threshold value, determine the on-off time of three-phase contact;

6) on-off time according to the three-phase contact calculates switching synchronization and closing time.

2, the online test method of the contacts for vacuum-break switches on-off time based on vibration analysis according to claim 1 is characterized in that described setting sampling order is A phase-B phase-C phase; Sample frequency is 〉=25kHz; Rising edge with the closing coil electric current starts sampling, and sampling length is the twice of breaker closing time.

3, the online test method of the contacts for vacuum-break switches on-off time based on vibration analysis according to claim 1 is characterized in that described threshold value range of choice is: first peak E in 0～vibration signal short-time energy analysis waveform _sHalf; Thereby obtain the zero-time of three-phase contact vibration event, respectively the on-off time of each phase contact of corresponding isolating switch; If the short-time energy of outside noise analysis maximal value is N before the vibration event _Max, threshold T then _hBe chosen as:

$T_h=\left\{\begin{array}{cc}10\×N_{\max }& 10\×N_{\max }\≤0.5\×E_s\\ 0.5\×E_s& 10\×N_{\max }>0.5\×E_s\end{array}\right.$

In the formula, E _sBe first peak value in the vibration signal short-time energy analysis waveform.

4, the online test method of the contacts for vacuum-break switches on-off time based on vibration analysis according to claim 1, it is characterized in that being calculated as follows of described switching synchronization, closing time: judge that according to the sequencing of on-off time head closes phase and closes mutually with last closing, the mistiming between them is switching synchronization; With the moment that the starting point of coil current arrives as reclosing command, it and last mistiming of closing between the on-off time that closes phase are the closing time of isolating switch.

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