CN101246043B - On-line monitoring method for vibration and noise of AC power transformer influenced by DC magnetic biasing - Google Patents
On-line monitoring method for vibration and noise of AC power transformer influenced by DC magnetic biasing Download PDFInfo
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Abstract
The present invention relates to a method for on-line monitoring the vibration and noise of the alternating-current power transformer which is affected by the direct-current magnetic biasing, and the method belongs to the electric power safety monitoring technique in the electric field, and the method comprises the following steps: when the direct-current magnetic biasing does not exist collecting the noise acoustic pressure signal of the noise sound pressure meter at the transformer position to confirm the vibration signal monitoring point, and recording the principal character data of vibration of transformer body when no direct-current magnetic biasing exists at the monitoring point; when the direct-current magnetic biasing state appears executing on-line monitoring according to the sampling interval, sampling frequency and monitoring period, and setting the monitoring threshold value of the maximum vibration amplitude; after each monitoring period analyzing the preserved raw data, when the early warning state appears steadily for more than one day continuously, the transformer body is needed to be further detected, otherwise, the operation state of the transformer is taken for excellent; the invention can realize the judgment to the vibration state of the transformer at the state of direct-current magnetic biasing and guarantee the safe and stable operation of the power transformer through long-period on-line monitoring.
Description
Technical field
The invention belongs to electrical field electric power safety monitoring technology, particularly a kind of method of monitoring the AC power transformer running status of influenced by DC magnetic biasing by monitoring power transformer tank surface vibration and noise state and then realization.
Background technology
Power transformer is the nucleus equipment in the AC electric power systems, and its iron core excitation family curve presents typical nonlinear.Under normal operation, transformer mainly operates near this characteristic saturation point, but under the influence of straight-flow system one pole line residual current, the DC current that flows into the earth will have the part electric current to flow near the AC power transformer of the neutral ground of direct current grounding pole, the DC current that flows into can reach tens amperes, therefore transformer fe the direct current flux component will occur in the heart, magnetic flux moves to a certain lateral deviation, equipment work point very easily enters saturated section of exciting characteristic curve, the generation half-wave is saturated, and this phenomenon just is referred to as DC magnetic biasing.DC magnetic biasing will cause the box house leakage flux to increase, the winding current distortion obviously, and then cause unshakable in one's determination and the basket vibration aggravation, tank surface vibration and noise obviously increase, vibration amplitude can reach original vibrational state more than 5 times, may produce for the structure of transformer and damage, power transformer runnability and serviceable life are produced serious influence.
Transformer body vibration mainly causes by the magnetostriction and the basket vibration of iron core, the situation that compresses of the vibration on power transformer device body surface and Transformer Winding and iron core, the displacement of winding and be out of shape closely related.Magnetostriction and transformer port voltage unshakable in one's determination have close ties, and the vibration of winding and winding current and transformer working load are closely connected.After the DC magnetic biasing state occurs, if distortion, displacement or avalanche are taking place in one of high-low pressure winding, compressing of winding is not enough, difference in height between the high-low pressure winding is enlarged gradually, cause the uneven aggravation of winding ampere-turn, the axial force that leakage field is caused increases, thus the vibration of winding aggravation; If the core pressing degree is affected, siliconized plate takes place loosening, when perhaps the deadweight of siliconized plate will make bending unshakable in one's determination or distortion, it is big that slit between the siliconized plate becomes, and it is big that the leakage field between siliconized plate seam crossing and the lamination becomes, and caused electromagnetic attraction to become big, so it is big that vibration unshakable in one's determination becomes, when there was the fault of multipoint earthing in iron core, the siliconized plate heating can cause that also the flexible iron coring vibration that causes of magnetic hysteresis becomes big in addition.These are in particular in being characterized as on the vibration signal: rumble spectrum changes, and the more harmonic components of high order occurred, and the amplitude of vibration becomes big.
Present research for transformer body vibration and noise, to probe into the character of vibration of transformer body and noise, be to be attached to vibration transducer on the diverse location of transformer tank surface by magnet base, near transformer, arrange the noise sound pressure meter, extract and analyze the vibration acceleration signal of tank surface according to field demand by sampling apparatus, and then realization is for the monitoring of transformer core and winding physical state, monitoring system and whole electric system are not electrically connected, and can not exert an influence to the normal operation of whole electric system.But it only can realize the monitoring of interior noise acoustic pressure waveform of short time and vibration amplitude, do not possess continuity on time, lack description intuitively for vibrational waveform, can't realize synchronous monitoring and result's comparison of noise and vibration, do not judge the variation of rumble spectrum quantitatively, can't realize under the Under Direct Current Bias judgement by long-term on-line monitoring for the transformer vibrational state.
Summary of the invention
The objective of the invention is for overcoming the weak point of prior art, AC power transformer vibration and noise on-line monitoring method under a kind of DC magnetic biasing state is proposed, can pass through long-term on-line monitoring, for the judgement of transformer vibrational state, ensure the power transformer safe and stable operation under the realization Under Direct Current Bias.
The vibration and noise on-line monitoring method of AC power transformer behind the DC magnetic biasing state that the present invention proposes is characterized in that, may further comprise the steps:
1) when not having DC magnetic biasing, at transforming plant main transformer depressor scene, 3 or 4 above vibration transducers are attached on the transformer tank surface, arrange apart from transformer one segment distance place that in the positive midpoint of transformer-cabinet (general spacing is a 1-3 rice to a noise sound pressure meter, the far and near change influence for relative quantity of distance is little, but it is excessive for noise contribution to cross the sound source that closely will cause near part, crosses the interference that far then can not ignore other noise source); In the time of setting, (be generally 1-3 days, load variations situation according to the locality is determined, as long as can determine the vibration amplitude scope of tank surface when transformer normally moves under the non DC bias condition), (sampling interval got final product less than 5 minutes, 5 minutes or can guarantee complete record transformer vibration variation tendency for a comparatively long period of time less than 5 minutes sampling interval according to the sampling interval of setting, sample frequency; Sample frequency generally is set at 2.5kHz-5kHz, because the transformer rumble spectrum is distributed in the scope of 50-1000Hz, according to sampling thheorem, what sample frequency will reach this frequency range at least is about 2.5kHz more than 2 times, but because the restriction of collecting device, the highest 5kHz that is set in), the noise sound pressure signal of the noise sound pressure meter of collection position, and the vibration signal of gathering the vibration transducer behind the conversion diverse location, determine position that vibration signal changes maximum vibration transducer as the vibration signal monitoring point according to sampled data, and the principal character data of transformer body vibration when writing down this monitoring point non DC bias;
2) after the DC magnetic biasing state occurred, according to described sampling interval, sample frequency, and monitoring periods carries out on-line monitoring, and (monitoring periods was generally 1-7 days, to observe obvious and lasting variation tendency, kept small amount of data simultaneously.Monitoring), the monitoring threshold of setting the maximum vibration amplitude is (when threshold value can be made as non DC bias 120% of the maximum vibration amplitude, monitoring threshold is crossed the young pathbreaker and is noted a large amount of invalid datas, monitoring threshold is excessive then may to cause the starting stage in time to pinpoint the problems), have only when vibration amplitude surpasses this threshold value and in database, preserve raw data, otherwise only in database, write down each time spectral magnitude in vibration peak valley and the corresponding frequencies scope;
3) every through a monitoring periods, the raw data that analysis is saved when the early warning situation appears in (continuous more than 1 day) steady in a long-term, then needs the transformer body is further detected (suspecting that the transformer inner structure may go wrong), otherwise, think that the transformer running status keeps good;
Above-mentioned steps 1) in during the monitoring point non DC bias principal character data of transformer body vibration comprise: (1) monitoring point vibrational waveform and noise waveform; (2) the tank surface vibration amplitude of different operating load correspondences, and draw the interior vibration amplitude curve of setting-up time, determine the maximal value of vibration amplitude under the normal condition and the scope of minimum value; (3) internal vibration of 50-1400Hz scope and noise spectrum distribute; (4) ratio of corresponding amplitude of each time frequency spectrum and time domain vibration amplitude.
Any of following four kinds of situations the early warning situation appears above-mentioned steps 3) is;
(1) vibration amplitude exceeds more than 20% of scope of the maximal value and the minimum value of vibration amplitude;
(2), and, do not cause the transformer operating load because of having obvious change as if the maximal value that exceeds vibration amplitude of described vibration amplitude and more than 20% of scope of minimum value;
(3) there is the high order frequency spectrum to occur in the spectral range;
(4) ratio of corresponding amplitude of each time frequency spectrum and time domain vibration amplitude has exceeded 20% variation range.
The beneficial effect of patent of the present invention is, can monitor bigger DC magnetic biasing (as under the DC line one pole line residual current method of operation or sun magnetic storm time appears) to the adverse effect of AC electric power systems and main power equipment, ensure the power transformer safe and stable operation, have crucial economic benefit.
Description of drawings
Fig. 1 is preceding measuring point place vibration acceleration time domain waveform of the DC magnetic biasing of present embodiment and frequency-domain analysis figure, and wherein, Fig. 1 (a) is the vibration time domain waveform, and Fig. 1 (b) is a vibration frequency specturm analysis.
Fig. 2 is time internal vibration crest and a corresponding time relationship curve map in the present embodiment.
Fig. 3 is an each harmonic spectrum component change curve in time.Wherein curve 1 is the frequency component change curve in time of 350Hz, and curve 2 is the frequency component change curve in time of 450Hz.
Fig. 4 is measuring point place vibration acceleration time domain waveform and frequency-domain analysis figure in the DC magnetic biasing process, and wherein, Fig. 4 (a) is the vibration time domain waveform, and Fig. 4 (b) is a vibration frequency specturm analysis.
Fig. 5 is measuring point place vibration acceleration time domain waveform and frequency-domain analysis figure after the DC magnetic biasing of present embodiment, and wherein, Fig. 5 (a) is the vibration time domain waveform, and Fig. 5 (b) is a vibration frequency specturm analysis.
Embodiment
The AC power transformer influenced by DC magnetic biasing vibration and noise on-line monitoring method that the present invention proposes reaches embodiment in conjunction with the accompanying drawings and is described in detail as follows:
The method of present embodiment may further comprise the steps:
When not having DC magnetic biasing, at transforming plant main transformer depressor scene, 3 vibration transducers are attached to by magnet base on the diverse location of transformer tank surface, arrange a noise sound pressure meter in the positive midpoint of transformer-cabinet apart from 1 meter distance of transformer; In 1 day time, gather the noise sound pressure signal of the noise sound pressure meter of described position with the sample frequency of 5.2kHz, and the vibration signal of gathering the vibration transducer behind the conversion diverse location, determine that according to sampled data vibration signal changes the position of maximum vibration transducer as the vibration signal monitoring point, present embodiment monitors the time domain waveform of this point shown in Fig. 1 (a), and waveform is clear, and is obviously regular, in a certain moment in monitoring periods, its vibration wave peak maximum is 7.5m/s
2Vibration trough minimum value is-10.0m/s, its maximum vibration amplitude is carried out spectrum analysis to the vibrational waveform of this point, its result is shown in Fig. 1 (b), visible spectrum mainly is distributed in the 200-600Hz scope, wherein the component of 350-450Hz is the most obvious, and results of spectral shows the frequency component that does not almost have 800Hz above in this vibration signal.
Present embodiment is made as 5.2kHz with the sample frequency of vibration signal, signal sampling is made as per 2 minutes once sampling at interval, in the Access database, write down the peak value of each vibration and the spectrum distribution in automatic analysis and the 50-1400Hz scope, in 1 day time range, monitor the time dependent curve of tank surface vibration amplitude, and determined the maximal value of vibration amplitude under the normal condition and the scope of minimum value thus.As shown in Figure 2, the crest maximal value of this some vibration is 17m/s
2, minimum is 1m/s
2, the meritorious ordinate of the data presentation correspondence that obtains from Control Room is respectively 460 and 200, also is respectively the maximal value and the minimum value of load.Think the following 1m/s of being limited to of vibration amplitude thus
2, on be limited to 17m/s
2
Also monitor for the amplitude of main spectrum component and the ratio of vibration amplitude because the component of 350Hz and 450Hz accounts for main part, here weight analysis the situation of change of these two kinds of components once, as shown in Figure 3.Curve 1 is the spectral magnitude of 350Hz correspondence and the ratio curve of time domain vibration amplitude, between 9%-11%; Curve 2 is the spectral magnitude of 400Hz correspondence and the ratio of time domain vibration amplitude, between 28%-32%.
When DC magnetic biasing occurring, shown in Fig. 4 (a), this measuring point vibration signal amplitude rises rapidly, and it is very irregular that waveform becomes, and the vibration wave peak maximum reaches 50m/s
2, the trough minimum value reaches-20m/s
2, shown in Fig. 4 (b), the above high fdrequency component of 800-1200Hz occurs.Under Under Direct Current Bias, because external condition has obvious change, can't be according to changing the state of determining the transformer inner structure this moment, in addition, because it is a process of aggravation gradually that the inner structure of transformer is destroyed, so need further analyze after DC magnetic biasing and monitor.
Fig. 5 has provided the DC magnetic biasing time domain waveform and the frequency-domain analysis figure of the vibration signal of this measuring point afterwards, can intuitively find out from Fig. 5 (a), and vibrational waveform does not have to change substantially, and its vibration wave peak maximum is 6.0m/s
2Vibration trough minimum value is-8.0m/s, vibrational waveform to this point carries out spectrum analysis, its result is as Fig. 5. (b), frequency spectrum still mainly is distributed in the 200-600Hz scope, component with 350-450Hz is the most obvious, and the above frequency component of 800Hz almost disappears in this vibration signal, can think consistent with the vibrational state before the DC magnetic biasing.
After occurring, DC magnetic biasing compares with appearance vibration before, if magnetic bias 20% the scope before that surpasses steady in a long-term of the vibration under the same load after the magnetic bias, such as, if ordinate is in 200 or when following, the amplitude of this monitoring point has the long-term 1.2m/s that significantly surpasses
2Ordinate is in 460 or when following, the amplitude of this monitoring point has the long-term 20m/s that significantly surpasses
2We think that transformer inside may go wrong, and need to determine in conjunction with other measuring point and on-the-spot actual investigation.In this process of the test, after Under Direct Current Bias, the vibration amplitude of having monitored when corresponding maximum is meritorious to be 460 left and right sides is 17.3m/s
2, to compare during with the non DC bias condition, its variation range is about 2%, less than 20%; Minimum vibration amplitude of gaining merit when being 200 left and right sides is 1m/s
2, compare basic not variation during with the non DC bias condition.
In addition, in the frequency range of 50-1400Hz, whether monitoring has a large amount of and long-term appearance of higher hamonic wave on the one hand, and whether the ratio of monitoring interior humorous wave amplitude of 300-450Hz and crest on the other hand can also return and be stabilized within the original scope after the of short duration fluctuation.If the variation of this ratio range for a long time greater than 20%, also is necessary to carry out suitable detection to investigate transformer state.In this process of the test, still between 9%-11%, the ratio of the spectral magnitude of 400Hz correspondence and time domain vibration maximum amplitude is still between 28%-32% for the ratio of the spectral magnitude of 350Hz correspondence and time domain vibration maximum amplitude after DC magnetic biasing.Measuring point is similar therewith for the signal of other vibration measuring points and noise measuring point, in this specific implementation process, in conjunction with the result of all measuring points, can think that running status is good in the short time range of this transformer after DC magnetic biasing, but still need further long-time on-line monitoring.
Claims (4)
1. the vibration and noise on-line monitoring method of AC power transformer behind the DC magnetic biasing state is characterized in that, may further comprise the steps:
1) when not having DC magnetic biasing, at transforming plant main transformer depressor scene, 3 or 4 above vibration transducers are attached on the transformer tank surface, arrange a noise sound pressure meter apart from transformer one segment distance place in the positive midpoint of transformer-cabinet; In the time of setting, according to sampling interval, the sample frequency set, the noise sound pressure signal of acquisition noise sound pressure meter, and the vibration signal of gathering the vibration transducer behind the conversion diverse location, determine position that vibration signal changes maximum vibration transducer as the vibration signal monitoring point according to sampled data, and the principal character data of transformer body vibration when writing down this monitoring point non DC bias;
2) after the DC magnetic biasing state occurs, according to described sampling interval, sample frequency, and monitoring periods carries out on-line monitoring, set the monitoring threshold of maximum vibration amplitude, have only when vibration amplitude surpasses this threshold value and in database, preserve raw data, otherwise only in database, write down each time spectral magnitude in vibration peak valley and the corresponding frequencies scope;
3) every through a monitoring periods, analyze the raw data that is saved, when the early warning situation appears in continuous stablizing more than 1 day, then need the transformer body is further detected, otherwise, think that the transformer running status keeps good;
2. method according to claim 1 is characterized in that, in the described step 1) during non DC bias of monitoring point the principal character data of transformer body vibration comprise: (1) monitoring point vibrational waveform and noise waveform; (2) the tank surface vibration amplitude of different operating load correspondences, and draw the interior vibration amplitude curve of setting-up time, determine the maximal value of vibration amplitude under the normal condition and the scope of minimum value; (3) internal vibration of 50-1400Hz scope and noise spectrum distribute; (4) ratio of corresponding amplitude of each time frequency spectrum and time domain vibration amplitude.
3. method according to claim 1 is characterized in that occurring the early warning situation described in the described step 3) is one of following three kinds of situations:
(1) vibration amplitude exceeds the maximal value and the minimum value 20% of vibration amplitude;
(2) there is the high order frequency spectrum to occur in the spectral range;
(3) ratio of corresponding amplitude of each time frequency spectrum and time domain vibration amplitude has exceeded 20% variation range.
4. method according to claim 1 is characterized in that, described sampling interval is 2.5kHz-5kHz less than 5 minutes, sample frequency, when the monitoring threshold of described maximum vibration amplitude is non DC bias 120% of the maximum vibration amplitude.
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