CN110031736B - Transformer insulation defect analysis method based on subsection dielectric loss test - Google Patents
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2605—Measuring capacitance
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2688—Measuring quality factor or dielectric loss, e.g. loss angle, or power factor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/14—Circuits therefor, e.g. for generating test voltages, sensing circuits
Abstract
The invention discloses a transformer insulation defect analysis method based on a subsection dielectric loss test. The dielectric loss test is widely applied to the analysis and diagnosis work of the insulation state of the transformer, but the traditional dielectric loss test method only tests the dielectric loss of a winding, an iron core, a clamping piece and the ground, and because the main transformer grounding is limited by a reverse connection method, the test accuracy is poor, and the defect of a specific position is difficult to effectively judge. According to the typical structure of a large-scale power transformer, the invention adopts a voltage-reducing positive connection method to carry out subsection test on dielectric loss among a transformer winding-iron core, a winding-clamping piece and different windings, and combines the analysis of the electric field coupling effect among insulating media of each part to carry out accurate analysis and defect positioning on the insulation defects among all parts of the transformer. The transformer insulation defect analysis method provided by the invention has higher defect detection efficiency and positioning accuracy.
Description
Technical Field
The invention relates to diagnosis of insulation defects of a transformer, in particular to a detection and diagnosis method of insulation defects of a winding, an iron core and a clamping piece of the transformer based on a subsection dielectric loss test.
Background
As an important item in the handover, pre-test, routine and diagnostic tests of the transformer, the dielectric loss and capacitance test has important significance for judging the overall moisture, oil degradation and serious local defects among windings of the transformer. But different wiring modes have a great influence on the test result of dielectric loss capacitance. Standards such as DL/T474.3-2006 'field insulation test implementation guide rule dielectric loss factor tan delta' test and JB/T501-2006 'power transformer test guide rule' and the like stipulate that the iron core and the clamping piece need to be grounded in a short circuit mode during testing, the insulation among the winding, the iron core, the clamping piece and the ground is considered as a whole, and the result of the testing is the weighted average value among all parts of the insulation according to the capacitance. However, for a large-scale power transformer, the insulation structure between the winding and the iron core and between the winding and the clamping piece is complex, the insulation of each part is independent relatively, and a complex capacitive coupling effect exists, and the insulation of the part with relatively small capacitance has defects under most conditions.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects of the existing detection and analysis technology and provides a method for detecting and diagnosing insulation defects of a winding, an iron core and a clamping piece of a transformer based on a subsection dielectric loss test.
Therefore, the technical scheme adopted by the invention is as follows: a transformer insulation defect analysis method based on a subsection dielectric loss test comprises the following steps:
a) the method comprises the following steps of performing subsection testing on dielectric loss between a winding and an iron core of the transformer and between the winding and a clamping piece by adopting a positive connection method, and respectively obtaining dielectric loss capacitance test values of the winding to the clamping piece/the iron core when the iron core/the clamping piece are grounded;
b) analyzing the electric field coupling effect among insulating media of the transformer winding, the iron core and the clamp, determining the actual difference of the insulation between the iron core and the clamp according to the test values and the mutual difference of the dielectric loss and the capacitance of the iron core and the clamp by the winding, and eliminating the coupling effect among the insulating parts and the influence of the capacitance of the insulating parts on the test result;
c) and obtaining the defect state of each insulating part by combining the typical structure of the large power transformer according to the corresponding relation between the test results of dielectric loss and capacitance of the winding pair iron core and the winding pair clamping piece and each insulating part of the transformer.
According to the typical insulation structure of a large-scale power transformer, the invention combines the capacitive coupling effect among all insulation parts during the subsection dielectric loss test to deeply analyze the subsection dielectric loss test result and the internal physical meaning under different wiring modes, and can effectively avoid the capacitive coupling and weighted average effect of the dielectric loss test result among all the insulation parts through the test analysis of the dielectric loss capacitance of the transformer winding-iron core (clamp grounding or shielding) and the winding-clamp (iron core grounding or shielding), thereby realizing the effective detection and positioning of the tiny insulation defect between the transformer winding and the iron core clamp.
The transformer insulation defect analysis method provided by the invention has higher defect detection efficiency and positioning accuracy.
Further, in the step a), when the dielectric loss capacitance of the winding-core and the winding-clamping piece of the transformer is tested by adopting a positive connection method, the selected test voltage is between 2kV and 2.5 kV.
Further, in the step a), dielectric loss and capacitance of the inner winding of the transformer closest to the iron core and the clamping piece are tested, and the outer winding of the transformer is in short circuit or suspension with the inner winding during the test, but the outer winding and the inner winding are not grounded.
Further, in the step b), the insulation among the inner side winding of the transformer, the iron core and the clamping piece forms a triangular loop structure, and the obvious T-shaped network interference coupling effect among the inner side winding, the iron core and the clamping piece is obtained through the equivalent transformation of the triangular-star loop structure.
Further, after the triangular loop structure is converted into the star-shaped loop structure, the dielectric loss values of three branches in the star-shaped loop structure are equivalently expressed as:
in the formula, subscripts "1", "2" and "3" are three nodes in a triangular loop and a star loop, and respectively represent a winding, an iron core and a clamping piece; c12、C13、C23Nodes 1-2, 1-3, and 2-3, respectively, that is, the capacitance between winding-core, winding-clamp, and core-clamp; delta12、δ13、δ23Respectively are nodes 1-2, 1-3 and 2-3, namely dielectric loss values among a winding-iron core, a winding-clamping piece and an iron core-clamping piece; delta1、δ2、δ3The dielectric loss values of three branches in the star-shaped loop are respectively.
Furthermore, when the subsection dielectric loss test is adopted, the test value of the dielectric loss under the winding-iron core connection mode is delta2The test value of dielectric loss in the winding-clamping piece wiring mode is delta3。
Further, in step b), the value of dielectric loss between the winding and the iron core is delta12Dielectric loss value delta between winding and clamping piece13The difference is the difference between the insulation dielectric loss test values of the winding-iron core and the winding-clamping piece, namely:
δ12-δ13＝δ2-δ3。
further, in step b), when one of the insulation of the winding-core or the winding-clamping piece has defects to cause large dielectric loss, delta2And delta3At least one value is obviously reduced or even negative; and delta2-δ3Is obviously larger; dielectric loss exceeding value not less than | delta for insulation of defective portion2-δ3|。
Further, in step c), when delta is greater than2Greater delta3When the voltage is smaller or even negative, the insulation dielectric loss between the inner side winding and the iron core of the transformer exceeds the standard, and the whole or part of insulation in the screen and the iron core binding belt between the inner side winding and the iron core has defects; when delta3Greater delta2When the voltage is smaller or even negative, the insulation dielectric loss between the inner winding of the transformer and the clamping piece exceeds the standard, and the whole or part of the insulation in the laminated board, the end ring and the ground screen between the inner winding and the upper and lower iron yokes has defects.
The method for detecting and diagnosing the insulation defects of the transformer winding, the iron core and the clamping piece based on the subsection dielectric loss test has extremely high detection and diagnosis precision on the tiny insulation defects among the transformer winding, the iron core and the clamping piece.
Drawings
FIG. 1 is a partial diagram of an equivalent capacitance of a large power transformer according to an embodiment of the present invention;
fig. 2 is an equivalent test circuit diagram under different wiring modes in an embodiment of the present invention (fig. 2a is winding-core (clip grounding or shielding), and fig. 2b is winding-clip (core grounding or shielding));
fig. 3 is a circuit diagram of an equivalent star structure in different connection modes according to an embodiment of the present invention (fig. 3a is winding-core (clip grounding or shielding), and fig. 3b is winding-clip (core grounding or shielding));
fig. 4 is an equivalent transformation diagram of the delta-star loop structure in the embodiment of the present invention (fig. 4a is delta connection, and fig. 4b is star connection).
Detailed Description
The invention is described in further detail below with reference to the figures and the detailed description of the invention.
Examples
A transformer insulation defect analysis method based on a subsection dielectric loss test comprises the following steps:
a) the method comprises the following steps of performing subsection test on dielectric loss between a transformer winding and an iron core (a clamping piece is grounded or shielded) and between the transformer winding and the clamping piece (the iron core is grounded or shielded) by adopting a positive connection method, and respectively obtaining dielectric loss and capacitance test values of the clamping piece/the iron core by the winding when the iron core/the clamping piece is grounded;
b) analyzing the electric field coupling effect among insulating media of each component of a transformer winding, an iron core and a clamping piece, determining the real difference of the insulation concrete dielectric loss among the winding, the clamping piece and each component of the iron core through the testing values and the mutual difference of the dielectric loss of the winding to the iron core (grounding or shielding of the clamping piece) and the winding to the clamping piece (grounding or shielding of the iron core), and eliminating the coupling effect among the insulating components and the influence of the capacitance of each insulating component on the testing result;
c) and obtaining the defect state of each insulating part by combining the typical structure of a large-scale power transformer according to the corresponding relation between the dielectric loss and capacitance test results of winding-to-core (clamp grounding or shielding) and winding-to-clamp (core grounding or shielding) and each insulating part of the transformer.
In the step a), dielectric loss and capacitance of the inner winding of the transformer closest to the iron core (the clamping piece is grounded or shielded) and capacitance of the clamping piece (the iron core is grounded or shielded) are respectively tested, and the outer winding of the transformer can be in short circuit or suspension with the inner winding during testing but should not be grounded. The dielectric loss test is carried out by adopting a direct connection method to ensure the test precision, but in order to ensure that the plus and minus insulation of the iron core is not damaged, the selected test voltage is between 2kV and 2.5 kV.
In the step b), the internal insulation structure of the transformer is shown in figure 1; the insulation among the inner side winding, the iron core and the clamping piece of the transformer forms a triangular loop structure in a dielectric loss and capacitance test loop, as shown in figure 2; the triangle loop structure has obvious capacitive coupling effect among branches in the test circuit, and is difficult to perform quick and effective numerical analysis, but the triangle structure can be equivalently converted into a star structure, as shown in fig. 3.
The equivalent conversion of the triangular loop structure and the star loop structure is shown in fig. 4, and for each branch, the following relationship exists:
For convenience of illustration, note:
m＝a+c+e，n＝b+d+f； (4)
then there are:
Z12＝a-jb；Z13＝c-jd；Z23＝e-jf (5)
the dielectric loss value of each branch can be expressed as:
δ12＝ωC12R12＝a/b；δ13＝ωC13R13＝c/d；δ23＝ωC23R23＝e/f； (6)
meanwhile, the dielectric loss value after all the branches in the triangular loop are connected in series is delta, and then:
according to the impedance equivalence principle, the following are provided:
substituting formula (5) to obtain:
for a series branch, the dielectric loss can be expressed as real/imaginary impedance, so there is:
in the above formula, delta12δ13、(δ12+δ13) δ is much less than 1, so the equation can be simplified as:
δ1≈δ12+δ13-δ (11)
substituting the formula (4) and the formula (7) to obtain:
substituting formula (3) to obtain:
the same can be obtained:
when the subsection dielectric loss test is adopted, the test result of the dielectric loss under the wiring mode of winding-iron core (clamping piece grounding or shielding) is delta2The dielectric loss test result in the winding-clamp (core grounding or shielding) connection mode is delta3. Subtracting the two test results to obtain:
δ12-δ13＝δ2-δ3 (16)
the above formula shows that the dielectric loss value delta between the winding and the iron core12With winding-clampsDielectric loss value delta between parts13The difference is the difference between the insulation dielectric loss test value of winding-core (grounding or shielding of the clamping piece) and winding-clamping piece (grounding or shielding of the core).
Delta when dielectric loss is large due to a defect in one of the winding-core or winding-clamp insulation2And delta3At least one numerical value is obviously reduced or even negative; and delta2-δ3Will be significantly larger; dielectric loss exceeding specific value of insulation of defective portion not less than | δ2-δ3|。
When delta2Greater delta3When the voltage is smaller or even negative, the insulation dielectric loss between the winding and the iron core inside the transformer exceeds the standard, and the whole or part of insulation in the screen and the iron core binding belt between the winding and the iron core has defects; when delta3Greater delta2When the voltage is smaller or even negative, the insulation dielectric loss between the winding inside the transformer and the clamping piece exceeds the standard, and the whole or part of the insulation in the laminated board, the end ring and the ground screen between the winding and the upper and lower iron yokes has defects.
Application example
The invention is further explained by taking an example of a +/-800 kV converter transformer and combining the drawings and the detailed description of the specification.
When the pole I high-end Y/delta A phase change current of a certain +/-800 kV extra-high voltage converter station is in a power failure maintenance period, the value of dielectric loss of a grid side winding to a valve side winding and the ground is found to reach 0.540 percent (18 ℃), the value is increased to a certain extent compared with the handover value, and other tests including transformer oil dielectric loss, oil chromatographic analysis, winding deformation and other data meet the requirements of regulations. The dielectric loss value of the network side winding of the converter transformer is a critical attention value, and whether insulation has defects is difficult to judge, so that a partial dielectric loss test is further carried out on the converter transformer, and the test results are shown in table 1.
TABLE 1 dielectric loss test results
Tab.1 Resultsofpartdielectriclosstest
The results of the subsection dielectric loss test show that the dielectric loss value of the grid side winding to the iron core insulation is seriously higher, and the dielectric loss value of the grid side winding to the clamp insulation even has a negative abnormal phenomenon. From the foregoing analysis, it is concluded that the dielectric loss test result is δ when the condition corresponds to the testing mode of the winding-core (clip grounding) on the grid side2Greater, delta3The severity is smaller, indicating C12Namely, the insulation dielectric loss of the winding to the iron core is obviously abnormal, namely, the dielectric loss value of the insulation material between the net side winding and the iron core is larger. The difference between the dielectric loss test results of the two following modes is about 32.5%, which shows that the insulation dielectric loss value between the winding and the iron core at the net side is at least greater than 32.5%, the insulation dielectric loss value is seriously beyond the standard required value, and the possibility of local moisture or aging is extremely high.
Considering that the valve side winding has normal dielectric loss test value to the iron core clamp, the insulation of the laminated plate, the end ring and the like between the winding and the upper and lower iron yokes does not have obvious abnormality. The larger dielectric loss value may be caused by two layers of screens or iron core binding bands between the net side winding and the iron core.
Analysis of data on the partial dielectric loss abnormality of the iron core and the clamping piece by the grid side winding shows that the possibility of large dielectric loss value caused by the defects of moisture or aging and the like existing in the two layers of shielding between the grid side winding and the iron core and the insulation on the iron core binding belt is high.
And subsequently, the moisture content of the converter transformer network side winding on the iron core insulation is further evaluated by adopting a frequency domain dielectric spectroscopy (FDS) and other modes, and the result shows that the moisture content between the converter transformer network side winding and the iron core is 1.7%, the moisture content (0.6-0.9%) of the rest insulation of the converter transformer and the insulation at the same position of other converter transformers in the same group is obviously increased, and the detection conclusion of the partial dielectric loss test is verified.
According to the actual test result, compared with the traditional dielectric loss test, the method for detecting and diagnosing the insulation defects of the transformer winding, the iron core and the clamping piece based on the subsection dielectric loss test has extremely high detection and diagnosis precision on the insulation defects among the transformer winding, the iron core and the clamping piece.
Claims (8)
1. A transformer insulation defect analysis method based on a subsection dielectric loss test is characterized by comprising the following steps:
a) the method comprises the following steps of performing subsection testing on dielectric loss between a winding and an iron core of the transformer and between the winding and a clamping piece by adopting a positive connection method, and respectively obtaining dielectric loss and capacitance testing values of the winding to the clamping piece/the iron core when the iron core/the clamping piece are grounded;
b) analyzing the electric field coupling effect among insulating media of the transformer winding, the iron core and the clamp, determining the actual difference of the insulation between the iron core and the clamp according to the test values and the mutual difference of the dielectric loss and the capacitance of the iron core and the clamp by the winding, and eliminating the coupling effect among the insulating parts and the influence of the capacitance of the insulating parts on the test result;
the mutual difference value refers to the mutual difference value between dielectric loss test values and the mutual difference value between capacitance test values;
c) obtaining the defect state of each insulating part by combining the typical structure of a large-scale power transformer and according to the corresponding relation between the test results of dielectric loss and capacitance of the winding pair iron core and the winding pair clamp and each insulating part of the transformer;
in the step b), the insulation among the inner side winding of the transformer, the iron core and the clamping piece forms a triangular loop structure, and the obvious T-shaped network interference coupling effect among the inner side winding, the iron core and the clamping piece is obtained through the equivalent transformation of the triangular-star loop structure.
2. The method for analyzing insulation defects of transformers according to claim 1, wherein in step a), the selected test voltage is between 2kV and 2.5kV when the dielectric loss capacitance of the winding-core and winding-clamp of the transformer is tested by using the forward connection method.
3. The method for analyzing insulation defects of transformers according to claim 1, wherein in step a), dielectric loss and capacitance of the inner winding of the transformer closest to the core and the clamping members are respectively tested, and the outer winding of the transformer is short-circuited or suspended with the inner winding but should not be grounded during the test.
4. The transformer insulation defect analysis method according to claim 1, wherein after the triangular loop structure is converted into the star-shaped loop structure, the dielectric loss values of three branches in the star-shaped loop structure are equivalently expressed as:
in the formula, subscripts "1", "2" and "3" are three nodes in a triangular loop and a star loop, and respectively represent a winding, an iron core and a clamping piece; c12、C13、C23Nodes 1-2, 1-3, and 2-3, respectively, that is, the capacitance between winding-core, winding-clamp, and core-clamp; delta12、δ13、δ23Respectively are nodes 1-2, 1-3 and 2-3, namely dielectric loss values among a winding-iron core, a winding-clamping piece and an iron core-clamping piece; delta1、δ2、δ3The dielectric loss values of three branches in the star-shaped loop are respectively.
5. The method of claim 4, wherein the step of testing the dielectric loss in the winding-core connection mode is δ2The test value of dielectric loss in the winding-clamping piece wiring mode is delta3。
6. The insulation defect analysis method for transformer according to claim 5, wherein in step b), the value of insulation dielectric loss between winding and core is δ12Dielectric loss value delta between winding and clamping piece13The difference is the difference between the insulation dielectric loss test values of the winding-iron core and the winding-clamping piece, namely:
δ12-δ13＝δ2-δ3。
7. the transformer insulation defect analysis method of claim 6, wherein in step b), when one of the insulation of the winding-core or the insulation of the winding-clamping piece has a defect, which causes dielectric loss to be large, δ2And delta3At least one value is obviously reduced or even negative; and delta2-δ3Is obviously larger; dielectric loss exceeding value not less than | delta for insulation of defective portion2-δ3|。
8. The transformer insulation defect analysis method according to claim 6, wherein in step c), when delta is greater than or equal to2Greater delta3When the voltage is smaller or even negative, the insulation dielectric loss between the inner side winding and the iron core of the transformer exceeds the standard, and the whole or part of the insulation between the screen between the inner side winding and the iron core binding belt has defects; when delta3Greater delta2When the voltage is smaller or even negative, the insulation dielectric loss between the inner winding of the transformer and the clamping piece exceeds the standard, and the whole or part of the insulation in the laminated board, the end ring and the ground screen between the inner winding and the upper and lower iron yokes has defects.
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Citations (5)
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| SU1023254A1 (en) * | 1980-12-26 | 1983-06-15 | Предприятие П/Я Г-4816 | Device for automatic measuring of capacitor and dielectric loss angle tangent |
| CN101833043A (en) * | 2010-03-30 | 2010-09-15 | 广元电业局 | Method for measuring electric capacity and dielectric loss of capacitance type voltage transformer |
| CN103018576A (en) * | 2012-12-03 | 2013-04-03 | 杭州西湖电子研究所 | Method for measuring dielectric loss factor and insulation resistance of power transformer |
| CN103336186A (en) * | 2012-12-18 | 2013-10-02 | 辽宁省电力有限公司检修分公司 | Method for testing transformer equipment without disassembling lead |
| CN203720273U (en) * | 2014-02-28 | 2014-07-16 | 国家电网公司 | Transformer dielectric loss and insulation resistor tester |
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- 2019-03-12 CN CN201910184852.3A patent/CN110031736B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU1023254A1 (en) * | 1980-12-26 | 1983-06-15 | Предприятие П/Я Г-4816 | Device for automatic measuring of capacitor and dielectric loss angle tangent |
| CN101833043A (en) * | 2010-03-30 | 2010-09-15 | 广元电业局 | Method for measuring electric capacity and dielectric loss of capacitance type voltage transformer |
| CN103018576A (en) * | 2012-12-03 | 2013-04-03 | 杭州西湖电子研究所 | Method for measuring dielectric loss factor and insulation resistance of power transformer |
| CN103336186A (en) * | 2012-12-18 | 2013-10-02 | 辽宁省电力有限公司检修分公司 | Method for testing transformer equipment without disassembling lead |
| CN203720273U (en) * | 2014-02-28 | 2014-07-16 | 国家电网公司 | Transformer dielectric loss and insulation resistor tester |
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