CN101556299A - Method for detecting micro deformation of transformer winding - Google Patents

Abstract

The invention discloses a method for detecting micro deformation of a transformer winding, which comprises the following steps: a pulse signal with a frequency higher than 1KHz is input into a transformer and the signals of an input terminal and an output terminal of the transformer are acquired by a sensor, after the signals acquired are processed, the transmission functions of the output terminal and the input terminal are computed, a correlation coefficient is computed by utilizing the transmission functions computed and a transmission function prior to the initial use of the transformer, if the correlation coefficient is judged to be smaller than the threshold value, an alarm signal of winding deformation is sent; and if the correlation coefficient is judged to be bigger than or equal to the threshold value, the acquired signals are processed and then saved into a database. The method for detecting micro deformation of transformer winding has simple measuring procedure, is easy to realize, can adjust measure precision on transformer deformation by adjusting the threshold value of the correlation coefficient and overcome the technology difficulty of deformation detection of the transformer for long time, and is easy to popularize.

Description

Detect the method for micro deformation of transformer winding

Technical field

The present invention relates to detection technique, be meant the method that detects micro deformation of transformer winding especially.

Background technology

In the various device of electric system, transformer is one of expensive and important equipment of comparison, and its security row is for guaranteeing that power grid security is significant.The calendar year statistics data of relevant transformer shows that all national 110kV and above grade power transformer reach 50% of total number of accident because of the external short circuit fault causes the accident of damage.From the strip inspection situation, the overwhelming majority is (to be changed as axial and radial dimension by winding deformation, the displacement of device body, winding distortion, bulge etc.) cause, and the main cause that causes these distortion to be transformer insulated thermal-electrical aging in the long-time running process cause that performance descends even damage, and the electric power the during external short circuit that causes thus, mechanical force are to the effect of winding.Transformer insulated four aging major influence factors are mechanical force, heat, electric field and oil contamination.The electric power that transformer outlet short-circuit current and inrush phenomenon produce is the transformer insulated aging main mechanical force factor of influence, powerful short-circuit current can cause the destruction of winding deformation and paper oil insulation, less short-circuit current or inrush phenomenon electric power can cause miniature deformation and progressively quicken this process, the paper oil insulation local defect that causes thus can produce shelf depreciation in electric field, further quicken the deterioration of minor insulation; Heat ageing is the principal mode of transformer oil Aging of Oil-paper Insulation in Oil, it causes paper oil insulation chemical degradation slowly, thereby cause the decline of insulating property, the highest hot(test)-spot temperature permissible value of power transformer can reach 140 ℃ at present, to paper oil insulation Effect on Performance highly significant.

Traditional transformer test method comprises: no-load voltage ratio measurement, winding resistance, short-circuit impedance and loss, excitatory impedance, dielectric loss etc.Other dedicated experiments also has: little water, infrared detection, recovery voltage and the insulating paper degree of polymerization etc. in shelf depreciation, frequency response, vibration analysis, the oil.

The conventional test method is used to detect transformer overall performance index; In the dedicated experiments, frequency response method and vibration analysis method can detect winding deformation, and the former has effect preferably, are extensively adopted by power industry at present, but can't detect the miniature deformation of winding.Above-mentioned for transformer deformation detection, bigger deformation can be detected, but the miniature deformation of winding can't be detected.

Summary of the invention

In view of this, the invention reside in the method that detects micro deformation of transformer winding that provides, above-mentioned to solve for transformer deformation detection, can't detect the problem of the miniature deformation of winding.

For addressing the above problem, the invention provides the method that detects micro deformation of transformer winding, comprising:

Adopt frequency to be higher than the pulse signal input transformer of 1KHZ, by the input end of sensor acquisition transformer and the signal of output terminal, after the signal that collects handled, calculate the transport function of output terminal and input end, use preceding transport function to calculate related coefficient first by transport function and the transformer that calculates, less than threshold value, then send the alerting signal of winding deformation if judge related coefficient.

Preferably, the described signal that collects is handled comprises:

Adopt small echo to window the signal of gathering is carried out denoising, the signal after the denoising is carried out time-frequency conversion, obtain frequency function.

Preferably, described threshold value is 0.6.

Preferably, also comprise: if judge related coefficient more than or equal to threshold value, the data storage after then the described signal that collects being handled is to database.

Method measuring process of the present invention is simple, is easy to realize, the threshold value of scalable related coefficient realizes the measuring accuracy of transformer deformation is regulated, and has overcome the technical difficulty that transformer deformation for a long time detects, and is easy to promote.

Description of drawings

Fig. 1 is the equivalent network figure of Transformer Winding;

Equipment connection diagram when Fig. 2 is detection;

Fig. 3 is the process flow diagram of detection method.

Embodiment

For clearly demonstrating the scheme among the present invention, provide preferred embodiment below and be described with reference to the accompanying drawings.

At first set forth the principle of the inventive method, for transformer, when frequency when higher (surpass 1kHz), transformer core is inoperative basically, and each winding all can be considered a passive linear two-port network that is made of distribution parameters such as resistance, electric capacity, inductance.The passive linear two-port network of equivalence can be referring to Fig. 1, if the distributed inductance of winding unit length, vertical electric capacity and ground capacitance are respectively L, K, C, and the resistance (very little usually) of ignoring winding, this equivalent network can be analyzed its characteristic by transfer function H (j ω).If mechanically deform phenomenons such as winding has taken place axially, radial dimension variation will certainly change the distribution parameter such as L, K, C of network, cause the zero point and the pole distribution of its transfer function H (j ω) to change.By this characteristic, can be when transformer not to use, the zero point and the pole distribution that detect transfer function H (j ω) change, and in the regular detection after transformer uses, the zero point and the pole distribution that detect transfer function H (j ω) once more change.By relatively testing the H (j ω) that obtains 2 times, just may judge whether the state of Transformer Winding deformation takes place.Generally speaking, the frequency response analysis analytic approach is the transport function of measuring transformer winding on the frequency band of broad, and analyzes the frequency response characteristic of winding, judges the method for winding state.

It is very little that Transformer Winding generation miniature deformation and insulation ag(e)ing cause the variable quantity of network parameter, for the accuracy that guarantees to measure, require the pulse signal of input to have higher amplitude and steeper wavefront (nanosecond), and general signal generator is difficult to satisfy simultaneously, so the parameter of pulse signal generator is as shown in table 1:

Output voltage ± 0.1～2kV ± 5%

Pulse polarity just/negative

Pulse repetition rate 0.1～999.9kHz ± 10%

Burst length standard 15ms 2.5kHz/5kHz

The adjustable pulse number of pulse can be selected 1～200

Pulse front edge 5ns ± 30%

Pulse width (at 50 Ω) 50ns ± 30%

Pulse width (at 1K Ω) 35ns～150ns

Burst periods 300ms

Internal resistance 50 Ω ± 20%

Physical dimension (mm) 440 * 430 * 180 (D * W * H)

Complete machine weight＜15kg

The single-phase AC220V of power supply ± 10%, 50/60Hz

Table 1

Pulse producer is arranged on an end of transformer, as shown in Figure 2, two voltage clamps of transformer connect correspondent voltage sensor (voltage probe) respectively, arrive voltage sensor after the voltage dividing potential drop, the voltage sensor measuring voltage of gathering high voltage signal is 6kV, input impedance 50M Ω, bandwidth 400MHz.So that the voltage signal acquisition of input transformer winding head and end is got off, is input to analysing terminal.

Because the basic functions that the rising edge very steep (5ns ± 30%) of the pulse signal of input transformer winding, analysing terminal are realized is exactly to get off by the pulse collection that this rising edge is extremely steep, sampling rate is greater than 2GS/S.Analysing terminal carries out denoising with the method that the signal that collects adopts small echo to window, and removes some outside undesired signals.Then the signal after the denoising is done time-frequency conversion, obtain the function of transformer head and end signal about frequency, end is: V _o(f), the function of head end (input end) is: V _i(f).Calculating transport function is the frequency response characteristic of winding, and formula is: $H\left(f\right)=\frac{V_o\left(f\right)}{V_i\left(f\right)}.$ Measurement is calculated the frequency response characteristic H (f) of Transformer Winding, compare with the frequency characteristic under its kilter (initial measurement that transformer carries out before dispatching from the factory or putting into operation), calculate the two conforming related coefficient, judge by related coefficient whether transformer has the winding miniature deformation, because therefore different transformer electrical specification differences, can preferably select for use related coefficient less than 0.6, then think to have deformation, otherwise the data that will test deposit database in.

The flow process of test can comprise referring to Fig. 3:

Step 1: set sample frequency, adopt number of times, reach the relevant setting of preserving sampled data;

Step 2: gather the transformer data;

Step 3: constantly judge sampling number, if do not arrive pre-determined number, execution in step 1, otherwise execution in step 4;

Step 4: preserve and adopt data;

Step 5: the signal of gathering is carried out calculation of transfer function after small echo denoising, Fourier transform, the spectrum analysis;

Step 6: the transport function of extracting the measurement before transformer uses;

Step 7: the data of step 5 and step 6 are compared, and calculate related coefficient;

Step 8: whether judge related coefficient less than threshold value, threshold value is set to 0.6 usually, and the precision of Ce Lianging is higher if desired, then regulates corresponding related coefficient; If then report to the police; Otherwise deposit the data of step 5 in database.

Method measuring process of the present invention is simple, is easy to realize, the threshold value of scalable related coefficient realizes the measuring accuracy of transformer deformation is regulated, and has overcome the technical difficulty that transformer deformation for a long time detects, and is easy to promote.

For the method for being set forth among each embodiment of the present invention, within the spirit and principles in the present invention all, any modification of being done, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (4)

1, detects the method for micro deformation of transformer winding, it is characterized in that, comprise: adopt frequency to be higher than the pulse signal input transformer of 1KHZ, by the input end of sensor acquisition transformer and the signal of output terminal, after the signal that collects handled, calculate the transport function of output terminal and input end, use preceding transport function to calculate related coefficient first by transport function and the transformer that calculates, less than threshold value, then send the alerting signal of winding deformation if judge related coefficient.

2, method according to claim 1 is characterized in that, the described signal that collects is handled comprises:

Adopt small echo to window the signal of gathering is carried out denoising, the signal after the denoising is carried out time-frequency conversion, obtain frequency function.

3, method according to claim 1 is characterized in that, described threshold value is 0.6.

4, method according to claim 1 is characterized in that, also comprises: if judge related coefficient more than or equal to threshold value, the data storage after then the described signal that collects being handled is to database.

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