CN106772152A - A kind of measuring method of transformer core remanent magnetism - Google Patents
A kind of measuring method of transformer core remanent magnetism Download PDFInfo
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- CN106772152A CN106772152A CN201611050411.7A CN201611050411A CN106772152A CN 106772152 A CN106772152 A CN 106772152A CN 201611050411 A CN201611050411 A CN 201611050411A CN 106772152 A CN106772152 A CN 106772152A
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R33/12—Measuring magnetic properties of articles or specimens of solids or fluids
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Abstract
The present invention relates to a kind of measuring method of transformer core remanent magnetism, the method is comprised the following steps：1) magnetization curve of transformer core is obtained, the magnetization curve discloses the DC component of no-load current and the relation of iron core remanent magnetism；2) 380V ac test voltages are loaded in Transformer Winding, measurement obtains no-load current；3) DC component of the no-load current is obtained；4) iron core remanent magnetism is obtained according to the magnetization curve and DC component.Compared with prior art, the present invention has the advantages that simple and feasible, can quantitative determine the remanent magnetism amount of master iron core, instructs the formulation of the demagnetization scheme of master iron core remanent magnetism, assesses erasure effect, is main transformer experiment and runs and providing technical support.
Description
Technical field
The present invention relates to transformer test and operation field, more particularly, to a kind of measurement side of transformer core remanent magnetism
Method.
Background technology
Transformer acts on operation by electromagnetic induction, using magnetic field as coupled field.Transformer core typically selects magnetic conductivity
Ferromagnetic material higher, such as silicon steel sheet.The magnetic conductivity of ferromagnetic material is nonlinear, and its numerical value is with the change of magnetic field intensity
And change.Why ferromagnetic material has magnetic property high, is that there are many very littles due to Ferromagnetic Material, have determination magnetic pole
Property and with the magnetic domain of very hard magnetization intensity, as shown in Figure 1.Under extraneous magnetic fields, magnetic domain has again along outer magnetic field direction
It is regularly arranged, so that the actual magnetic field for producing is more much bigger than magnetic field in nonferromagnetic material.
The polarization of magnetic domain needs to experience a process, therefore in magnetic history, magnetic induction density B in ferromagnetic material
Change lags behind the change of external magnetic field strength H, i.e. hysteresis.Under alternation external magnetic field, iron-core magnetic induction intensity B is with outer magnetic
The change curve of field intensity H turns into hysteresis curve.Different hysteresis curves can be measured with different Bm values, by all hysteresis curves
Coupled together on the summit of I quadrants, the magnetization curve for obtaining is called fundamental magnetization curve, as shown in Figure 2.Due to most of iron
The hysteresis curve of magnetic material is all very narrow, therefore, in engineer applied, hysteresis curve can be replaced to solve to ask with fundamental magnetization curve
Topic, its error is allowed by engineering.
After transformer is cut off the electricity supply, the magnetic linkage for retaining in the core referred to as remanent magnetism.When remanent magnetism can increase main transformer combined floodgate
Excitation surge current, the harmonic wave in increase exciting current, increases transformer power consumption, it is also possible to cause protective relaying maloperation to be made, to main transformer
Operation adversely affect, meanwhile, remanent magnetism is also possible to make follow-up test results abnormity.
The way of production of remanent magnetism be mainly D.C. resistance experiment, its remanent magnetism number depending on Transformer Winding pass through it is straight
Stream current strength and the time.In transformer directly hinders experiment, to improve certainty of measurement, shortening time of measuring, high current is generally used
Tester, more than exciting current, makes core sataration, can produce serious remanent magnetism.In addition, can also be produced in no-load transformer separating brake
Raw remanent magnetism, but master iron core uses soft magnetic materials at present, and remanent magnetism amount is less, and corresponding harm is also smaller.
In order to the accurate and main transformer for ensureing follow-up test runs safety, it is desirable to did after D.C. resistance is tested to enter main transformer
Row demagnetization, but erasure effect cannot check.In follow-up low-voltage no-load test, often there is result of the test and often differ with delivery test
The situation of cause, it is impossible to true reflection inside transformer state.Needs scene carries out secondary demagnetization, increases experiment work amount and work
Time.In addition, in super-pressure main transformer closes a floodgate experiment, also occurring, due to the influence of iron core remanent magnetism, causing main transformer excitation surge current
Excessive, the thing for triggering main transformer grave gas protection act occurs.
In summary, the e measurement technology of main transformer remanent magnetism amount is tested main transformer and safe operation important in inhibiting.Comprehensive mesh
Demagnetization technology is concentrated in preceding domestic and international present Research, the at present research for main transformer remanent magnetism, is related to for the measurement of remanent magnetism less.
The content of the invention
The purpose of the present invention is exactly to provide a kind of simple and feasible change for the defect for overcoming above-mentioned prior art to exist
The measuring method of depressor iron core remanent magnetism.
The purpose of the present invention can be achieved through the following technical solutions：
A kind of measuring method of transformer core remanent magnetism, the method is comprised the following steps：
1) magnetization curve of transformer core is obtained, the magnetization curve discloses the DC component and iron core remanent magnetism of no-load current
Relation；
2) 380V ac test voltages are loaded in Transformer Winding, measurement obtains no-load current；
3) DC component of the no-load current is obtained；
4) iron core remanent magnetism is obtained according to the magnetization curve and DC component.
The magnetization curve of the transformer core is converted by main transformer no-load characteristic.
When main transformer no-load characteristic is converted into the magnetization curve of transformer core, hypothesis below is set：
A) magnetic hysteresis and eddy-current loss in iron core are ignored；
B) winding resistance is ignored；
C) pointwise forms magnetization curve.
During the formation magnetization curve, the current value of each point in magnetization curve is calculated by trapezoidal integration.
The step 3) in, by carrying out FFT decomposition to the no-load current, DC component is obtained, and by following public affairs
Formula obtains DC component perunit value：
In formula, IdcIt is the DC component of the no-load current of actual measurement,It is DC component perunit value, I0It is the specified electricity of main transformer
The virtual value of stream.
Compared with prior art, the present invention has advantages below：
(1) relation by studying no-load current and iron core remanent magnetism of the invention, proposes that simple and feasible transformer core is remained
The measuring method of magnetic.
(2) present invention can quantitative determine the remanent magnetism amount of master iron core, to instruct the demagnetization scheme of master iron core remanent magnetism
Formulate, assess erasure effect, test and run providing technical support for main transformer.
(3) present invention can be effectively measured iron core remanent magnetism amount, facilitate the inspection of erasure effect, so as to improve main transformer
The security of operation.
Brief description of the drawings
Fig. 1 is the magnetic domain schematic diagram in ferromagnetic material, wherein, (1a) is schematic diagram before magnetization, and (1b) is for after fully magnetising
Schematic diagram；
Fig. 2 is the hysteresis curve and fundamental magnetization curve in ferromagnetic material, wherein, (2a) is hysteresis curve, and (2b) is basic
Magnetization curve；
Fig. 3 is that iron core magnetizes curve synoptic diagram；
Fig. 4 is have no-load current schematic diagram in the case of remanent magnetism；
Fig. 5 is iron core magnetization curve and no-load current DC component and the Relationship Comparison schematic diagram of remanent magnetism curve；
Fig. 6 is schematic flow sheet of the invention；
Fig. 7 is no-load transformer current waveform schematic diagram under small voltage, wherein, (7a) is that (low pressure is non-linear for Br=-25
Area) when oscillogram, (7b) be Br=-100 (low pressure inelastic region) when oscillogram, (7c) be Br=-495.17 (low pressure is non-
Linear zone) when oscillogram.
Specific embodiment
The present invention is described in detail with specific embodiment below in conjunction with the accompanying drawings.The present embodiment is with technical solution of the present invention
Premised on implemented, give detailed implementation method and specific operating process, but protection scope of the present invention is not limited to
Following embodiments.
The typical fundamental magnetization curve of transformer is as shown in figure 3, three parts can be divided into：Low pressure inelastic region, linear zone, height
Pressure inelastic region.Low pressure being operated in the case of no remanent magnetism, when low-voltage no-load test is carried out at scene, iron core non-linear more
Area.If there is remanent magnetism in iron core, the test voltage of low-voltage, magnetic induction intensity and residual magnetic induction in iron core are loaded on winding
Intensity is superimposed, and the magnetic induction intensity in iron core just occurs biasing, and accordingly, no-load current also occurs direct current biasing, such as Fig. 4
It is shown.Therefore, the DC component in no-load current is the direct reaction of remanent magnetism amount in iron core, the zero load electricity under measurement small voltage
Stream, can indirectly measure iron core remanent magnetism.
From principle, the DC component in the small no-load current of small voltage observes the basic of the transformer with iron core remanent magnetism amount
Magnetization curve is constrained, i.e. iron core remanent magnetism amount and the DC component in no-load current is one-to-one.
To verify this corresponding relation, by taking certain 110kV main transformer winding as an example, simulation model is set up using EMTP, in iron core
Upper loading 380V sinusoidal voltages, calculate the no-load current under different iron core remanent magnetism amounts, and apply Fourier analysis, calculate sky
Carry the DC component in electric current.As shown in table 1-2, in table, a reference value of electric current is the sky under main transformer rated voltage to result of calculation
Set current value (1.78A), a reference value of magnetic flux is the magnetic flux (495.17Wb) under rated voltage.Magnetic induction intensity point in iron core
Not at low pressure inelastic region, linear zone and high pressure inelastic region, no-load current waveform is as shown in Figure 5 respectively.
It can be seen that, the DC component in no-load current under small voltage it is corresponding with iron core remanent magnetism amount on the transformer
Fundamental magnetization curve is basically identical.
In fact, experiment and operations staff can only learn main transformer no-load characteristic from Transformer Plant Test report, due to
The stray capacitance influences of transformer, there is certain error in it, but error is in engineering allowed band with the excitation curve of iron core.
In the present invention, iron core fundamental magnetization curve is substituted using main transformer no-load characteristic.
As shown in fig. 6, the measuring method of transformer core remanent magnetism of the invention is comprised the following steps：
1) main transformer no-load characteristic is obtained, the magnetization curve of transformer core is converted into, the magnetization curve is disclosed
The DC component of no-load current and the relation of iron core remanent magnetism；
2) 380V ac test voltages are loaded in Transformer Winding, measurement obtains no-load current；
3) by carrying out FFT decomposition to the no-load current, DC component is obtained；
In the method, DC component is recorded using perunit value form, is obtained by below equation：
In formula, IdcTo survey the DC component of main transformer no-load current,Based on become the perunit value of unloaded current dc component,
I0It is the virtual value of the rated current of main transformer；
4) iron core remanent magnetism is obtained according to the magnetization curve and DC component.
It is critical only that no-load transformer characteristic is converted into substantially using the no-load current measurement measurement of residual magnetism under small voltage
The degree of accuracy of magnetization curve.In transfer process, do it is assumed hereinafter that：
1st, the magnetic hysteresis and eddy-current loss in iron core are ignored；
2nd, winding resistance is ignored；
3rd, pointwise forms magnetization curve.
Voltage in power system can regard ideal voltage source as, i.e. standard sine voltage, therefore iron core magnetic flux is：
(in the formula, urms, ω what is represented respectively)
In formula, urmsIt is system voltage virtual value, ω is system voltage angular frequency, and ω=2 π f, f are system voltage frequency,
In China f=50Hz.
CTR current transfer ratio is more complicated, and in transfer process, it is reference point to choose first point, is partly thought below reference point
It is the range of linearity.
Current value of the reference point in magnetization curve sees below formula
In formula, irms,1In for electric current conversion, first point is the current effective value of reference point.
The equal recursion of remaining each point is tried to achieve.Assuming that inIt is next value to be asked, and then assumes sinusoidal magnetic linkage just in maximum
Value reaches φn.Current curve uses Piecewise, and each known point is it has been determined that only final stage is because of inIt is unknown uncertain.
Then i is calculated with integration methodnVirtual value：
Using trapezoidal integration, can calculate
In formula, a, b are respectively the constant coefficient of trapezoidal integration, can calculate gained according to main transformer magnetization curve.
Separately have, In=irms,n
The current value i of nth point in magnetization curve can then be obtainedn, so that pointwise forms magnetization curve.
Claims (5)
1. a kind of measuring method of transformer core remanent magnetism, it is characterised in that the method is comprised the following steps：
1) magnetization curve of transformer core is obtained, the magnetization curve discloses the DC component of no-load current and the pass of iron core remanent magnetism
System；
2) 380V ac test voltages are loaded in Transformer Winding, measurement obtains no-load current；
3) DC component of the no-load current is obtained；
4) iron core remanent magnetism is obtained according to the magnetization curve and DC component.
2. the measuring method of transformer core remanent magnetism according to claim 1, it is characterised in that the transformer core
Magnetization curve is converted by main transformer no-load characteristic.
3. the measuring method of transformer core remanent magnetism according to claim 2, it is characterised in that main transformer no-load characteristic is bent
When line is converted to the magnetization curve of transformer core, hypothesis below is set：
A) magnetic hysteresis and eddy-current loss in iron core are ignored；
B) winding resistance is ignored；
C) pointwise forms magnetization curve.
4. the measuring method of transformer core remanent magnetism according to claim 3, it is characterised in that the formation magnetization curve
During, the current value of each point in magnetization curve is calculated by trapezoidal integration.
5. the measuring method of transformer core remanent magnetism according to claim 1, it is characterised in that the step 3) in, lead to
Crossing carries out FFT decomposition to the no-load current, obtains DC component, and obtain DC component perunit value by below equation：
In formula, IdcIt is the DC component of the no-load current of actual measurement,It is DC component perunit value, I0It is the rated current of main transformer
Virtual value.
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107910157A (en) * | 2017-11-30 | 2018-04-13 | 国家电网公司 | Universal intelligent main transformer demagnetization instrument |
| CN108107384A (en) * | 2017-12-18 | 2018-06-01 | 国网新疆电力公司检修公司 | 750kV auto-transformers directly hinder remanent magnetism amount computational methods after experiment |
| CN109490729A (en) * | 2018-12-07 | 2019-03-19 | 国网四川省电力公司电力科学研究院 | A kind of remanent magnetism appraisal procedure and system becoming domain integral based on voltage attenuation process |
| CN109541506A (en) * | 2018-10-16 | 2019-03-29 | 中国电力科学研究院有限公司 | A kind of measurement of power transformer iron core magnetic characteristic and analytical equipment |
| CN110208725A (en) * | 2019-06-19 | 2019-09-06 | 国家电网有限公司 | A method of judging power transformer iron core, whether there is or not remanent magnetism |
| CN112068050A (en) * | 2020-09-10 | 2020-12-11 | 云南电网有限责任公司电力科学研究院 | Transformer residual magnetism quantitative evaluation and elimination method |
| CN113325345A (en) * | 2021-06-02 | 2021-08-31 | 云南电网有限责任公司电力科学研究院 | Device and method for testing residual magnetism of transformer core |
| CN115032577A (en) * | 2022-08-10 | 2022-09-09 | 之江实验室 | Low-noise residual magnetism detection device and method for annular ferrite material |
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Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107910157A (en) * | 2017-11-30 | 2018-04-13 | 国家电网公司 | Universal intelligent main transformer demagnetization instrument |
| CN107910157B (en) * | 2017-11-30 | 2023-12-15 | 国家电网公司 | Universal intelligent main transformer demagnetizing instrument |
| CN108107384A (en) * | 2017-12-18 | 2018-06-01 | 国网新疆电力公司检修公司 | 750kV auto-transformers directly hinder remanent magnetism amount computational methods after experiment |
| CN109541506A (en) * | 2018-10-16 | 2019-03-29 | 中国电力科学研究院有限公司 | A kind of measurement of power transformer iron core magnetic characteristic and analytical equipment |
| CN109490729A (en) * | 2018-12-07 | 2019-03-19 | 国网四川省电力公司电力科学研究院 | A kind of remanent magnetism appraisal procedure and system becoming domain integral based on voltage attenuation process |
| CN109490729B (en) * | 2018-12-07 | 2020-12-22 | 国网四川省电力公司电力科学研究院 | Residual magnetism assessment method and system based on variable region integration in voltage attenuation process |
| CN110208725A (en) * | 2019-06-19 | 2019-09-06 | 国家电网有限公司 | A method of judging power transformer iron core, whether there is or not remanent magnetism |
| CN112068050A (en) * | 2020-09-10 | 2020-12-11 | 云南电网有限责任公司电力科学研究院 | Transformer residual magnetism quantitative evaluation and elimination method |
| CN112068050B (en) * | 2020-09-10 | 2023-10-13 | 云南电网有限责任公司电力科学研究院 | Transformer remanence quantitative evaluation and elimination method |
| CN113325345A (en) * | 2021-06-02 | 2021-08-31 | 云南电网有限责任公司电力科学研究院 | Device and method for testing residual magnetism of transformer core |
| CN113325345B (en) * | 2021-06-02 | 2024-04-09 | 云南电网有限责任公司电力科学研究院 | Device and method for testing residual magnetism of transformer core |
| CN115032577A (en) * | 2022-08-10 | 2022-09-09 | 之江实验室 | Low-noise residual magnetism detection device and method for annular ferrite material |
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