CN113009286A - Method for diagnosing insulation defect at end part of stator wire rod of generator - Google Patents
Method for diagnosing insulation defect at end part of stator wire rod of generator Download PDFInfo
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- CN113009286A CN113009286A CN201911332697.1A CN201911332697A CN113009286A CN 113009286 A CN113009286 A CN 113009286A CN 201911332697 A CN201911332697 A CN 201911332697A CN 113009286 A CN113009286 A CN 113009286A
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- stator
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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
Abstract
The invention relates to the field of power generation equipment, in particular to a method for diagnosing insulation defects at the end parts of stator bars of a generator. The method comprises the steps of marking joints of the upper end part and the lower end part of the stator bar, and marking according to the position of the stator bar, so that the defect position is conveniently determined. And hand-wrapping insulation at two ends of the stator bar is wrapped with tin foil paper. The test voltage is generally selected as the rated voltage of the stator. The invention makes up the defect that the insulation defect of the end part of the line bar far away from the iron core is found in the direct current voltage withstand test or the alternating current voltage withstand test, not only can the defect of the insulation of the stator be found, but also the specific position of the defect can be determined. During testing, the winding bar does not need to be taken out of the stator core, so that damage to the winding bar possibly caused is avoided, the engineering efficiency is improved, the cost is reduced, and the running safety of the generator is better ensured.
Description
Technical Field
The invention relates to the field of power generation equipment, in particular to a method for diagnosing insulation defects at the end parts of stator bars of a generator.
Background
In the prior art, a stator winding of a generator belongs to a core component of the generator, and the insulation state of the stator winding is a key factor for determining the service life and the operation reliability of the generator. The insulation of the stator winding has certain voltage resistance, heat resistance, mechanical force resistance, corona prevention and other performances. There are generally two types of insulation defects in generators: one is a concentrated defect caused by partial discharge, moisture, aging, mechanical damage, etc.; and another type of distributed defects caused by moisture, aging and deterioration of the whole insulation needs to timely find and solve the insulation hidden trouble of equipment through a factory test, a handover test or a preventive test.
However, the dc withstand voltage test and the stator ac withstand voltage test, which are conventionally used at present, have some disadvantages. The stator winding leakage current and direct current withstand voltage test can effectively judge whether the insulation of the stator winding is affected with damp or has local defects, and particularly can effectively find the defects of the end part of the stator winding and the terminal board of the outgoing line. The alternating-current withstand voltage test can effectively find the integral degradation of the stator winding insulation and the local defects of the stator winding slot part. For the insulation of the end part far away from the iron core, no matter direct current voltage or alternating current voltage is applied, the voltage born by the insulation is greatly reduced under the action of the insulation resistance of the surface of the end part. Therefore, when there is a defect in insulation, even if both insulation resistance and capacitance resistance are greatly reduced, the insulation defect of the insulated end portion cannot be found effectively by both the dc withstand voltage test and the ac withstand voltage test under the influence of the insulation resistance of the end portion surface. Although the defects of the stator insulation can be found according to the serious unbalance of the three-phase leakage current when the leakage current of the stator winding is measured under the direct-current voltage, the specific positions of the defects cannot be determined, and the smooth elimination of the insulation defects of the stator bar by the method is still difficult.
Disclosure of Invention
The invention aims to provide a method for diagnosing the insulation defect of the end part of the stator wire rod of the generator aiming at the defects. The insulation performance and the position of the joint part at the end part of the stator are judged according to the potential level of the surface of the stator bar after rated direct current voltage is simultaneously applied to the three-phase winding of the stator.
The technical solution of the invention is as follows: a system for diagnosing the insulation defect of the end part of a stator wire rod of a generator is characterized by comprising a stator wire rod to be detected, wherein the stator wire rod is provided with a measuring rod shell, the measuring rod shell is connected with a measuring rod handle with a certain safe length, a detection probe is connected to the end part of the stator wire rod wrapped with tin foil paper or aluminum foil paper, and the measuring rod handle 4 is connected with an electrostatic voltmeter and a microammeter on a control console through a lead.
A method for diagnosing the insulation defect of the end part of a stator wire rod of a generator is characterized by comprising a stator wire rod to be detected, wherein the stator wire rod is provided with a measuring rod shell, the measuring rod shell is connected with a measuring rod handle with a certain safe length, a detection probe is connected to the end part of the stator wire rod wrapped with tin foil paper or aluminum foil paper, and the measuring rod handle is connected with an electrostatic voltmeter and a microammeter on a control console through a lead; the detection method comprises the following steps:
(1) and the joints of the upper end part and the lower end part of the stator bar are marked, and the labels are marked according to the positions of the stator bars, so that the defect positions are conveniently determined.
(2) When in measurement, high-voltage live working safety measures are required to be executed, and a measurer wears an insulating boot and an insulating glove, stands on an insulating pad and is monitored by a specially-assigned person.
(3) Wrapping tin foil paper outside the hand-wrapped insulation at two ends of the stator bar; the tin foil paper is tightly wrapped at the measuring part, and meanwhile, the tin foil paper cannot collide with the adjacent measured part, so that the error breakage caused by the increase of the measuring branch is avoided; keeping the distance between the tinfoil paper and the ground to be more than 3 cm.
(4) Adjusting a test power supply: the test power supply adopts full-wave or bridge circuit as much as possible for rectification, and the test voltage is usually selected as the rated voltage of the stator.
(5) Adjusting the measuring range of the microammeter and the electrostatic voltmeter according to the test voltage: the microammeter range should be larger than the ratio of the test voltage to the insulation resistance element, and usually 100 and 150 muA are selected firstly; the range of the electrostatic voltmeter should be larger than the test voltage.
(6) Overlapping a detection probe on the tin foil paper at the end part of the wire rod to be detected, turning on a test power supply, reading after the indexes of the electrostatic voltmeter and the microammeter are stabilized, and considering that insulation has defects when the voltage or the current is abnormally large or exceeds a standard value; after the corresponding record is made, the detection of the next line bar can be carried out.
(7) If the experimental result is not obvious enough, the specific position of the insulation defect can be determined by moving the position wrapped by the tin foil.
(8) And after the test is finished, the power supply of the instrument is turned off, the stator coil fully discharges to the ground, and then the wrapped tin foil paper is removed.
The invention has the advantages that: 1. the invention makes up the defects of the direct current voltage withstand test or the alternating current voltage withstand test in the aspect of finding the insulation defect of the end part of the line bar far away from the iron core, not only can find the defect of the stator insulation, but also can determine the specific position of the defect. 2. During testing, the winding bar does not need to be taken out of the stator core, so that damage to the winding bar possibly caused is avoided, the engineering efficiency is improved, the cost is reduced, and the running safety of the generator is better ensured.
Embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
Drawings
FIG. 1 is a schematic diagram of a diagnostic system of the present invention.
Fig. 2 is a schematic diagram of a measurement system of the present invention.
Detailed Description
Referring to fig. 1, the part names are as follows: the device comprises a stator bar 1, a detection probe 2, a measuring bar shell 3, a measuring bar handle 4, an electrostatic voltmeter 5, a microammeter 6, a left-handed knob 7, a right-handed knob 8 and a console 9.
The left side is a measuring rod of the surface potential of the bar, and the right side is a control console 9 of the system. In fig. 1, a detection probe 2 is connected to the end part of a stator bar 1 to be detected wrapped with tin foil or aluminum foil. The measuring rod shell 3 is internally provided with a 100M psi insulation resistance element. When a higher test voltage is used, the measuring rod housing 3 can be removed and the resistance element with a larger capacity can be replaced. In order to avoid endangering the tester when the insulation resistance element is punctured or flashes, the measuring rod shell 3 is provided with a certain safety length. The measuring rod shell 3 is connected with a measuring rod grip 4. The control station is internally composed of an electrostatic voltmeter 5 and a microammeter 6, the readings of which are used to determine the insulation state of the ends of the stator bars 1. The measuring ranges of the two electric meters can be adjusted through the left rotating knob 7 and the right rotating knob 8 respectively according to the test voltage. The microammeter is connected in series with an insulation resistance element in the measuring housing 3 and then connected in parallel with the electrostatic voltmeter.
Referring to fig. 2, the part names are as follows: DC test voltage U0Volume insulation resistance Rv of a wire rod, surface insulation resistance Rp of the wire rod, insulation resistance R, microammeter uA, electrostatic voltmeter V, wire rod part to be measured 10, measuring rod part 11, console part 12
The end part of the stator wire rod is insulated under the action of direct-current test voltage, when the end part is insulated normally, the insulation resistance of the insulation volume of the end part is far larger than the insulation resistance of the surface of the end part, the voltage drop born by the end part insulation is close to the test voltage, the surface of the end part is lower to the ground voltage, and the leakage current is smaller; when the end insulation has defects, the volume resistance of the end insulation is reduced, the voltage drop born by the insulation is correspondingly reduced, the voltage of the end surface to the ground is higher, and the leakage current is larger. When the insulation is defective, the phenomenon that the insulation surface increases to the ground potential, that is, the potential moves outward. In the detection process, a forward connection method or a reverse connection method can be adopted according to actual conditions. The positive wiring means that a direct current test voltage is applied to a stator winding, and the position of the insulated tin-coated paper is connected with a microampere meter in series through a 100M psi resistor and grounded. The reverse connection method is that the stator winding is connected in series with microampere meter grounding through 100M psi resistance, and is pressed at the insulated tin-coated paper. The positive connection method is suitable for the conditions that the positions to be measured are more and insulation defects are not clear, is safer and requires larger test capacity. The reverse connection method is suitable for the condition that a few parts are measured after maintenance.
Referring to fig. 1 and 2, the specific implementation flow of the method for diagnosing the insulation defect at the end of the stator bar of the generator is as follows:
(1) in order to effectively detect insulation defects, the insulation should generally be tested before cleaning the end insulation. The joints of the upper end part and the lower end part of the stator bar 1 are marked, and the labels are marked according to the position of the stator bar 1, so that the defect position is conveniently determined, the disorder of the recording is avoided, and the repeated work is reduced.
(2) And safety measures of high-voltage live working are required to be executed during measurement. Before testing, a measurer should wear the insulating boot and wear the insulating gloves, stand on the insulating pad, and set up a special person for monitoring.
(3) Tin foil paper is wrapped outside the hand-wrapped insulation at the two ends of the stator bar 1. The measuring part is tightly wrapped with the tin foil paper (the thickness is 0.01-0.02 mm), and meanwhile, the tin foil paper cannot collide with the adjacent measured part, so that the error breakage caused by the increase of measuring branches is avoided. For convenience of comparison, the wrapping lengths of the measurement parts are not suitable to be too different, because the wrapping surface distance is large, the volume insulation resistance is small, and the surface is large relative to the ground potential. The distance between the tinfoil paper and the ground is kept to be more than 3 cm, and when the end insulation has a penetrating defect, the surface to ground potential is equivalent to a test voltage, and the phenomenon of discharge is easily caused when the distance between the tinfoil paper and the ground is too small.
(4) And adjusting the test power supply. The test power supply adopts full-wave or bridge circuit as much as possible for rectification, and the test voltage is usually selected as the rated voltage of the stator. Sometimes, a higher test voltage may be used to find the cause of the leakage current imbalance or to find the defect site, but the test time is not suitable to be too long.
(5) The measuring ranges of the microammeter 6 and the electrostatic voltmeter 5 are adjusted according to the test voltage. The measuring range of microammeter 6 should be larger than the ratio of test voltage to insulation resistance element, usually 100-; the range of the electrostatic voltmeter 5 is larger than the test voltage.
(6) And overlapping the detection probe 2 on the tin foil paper at the end part of the stator bar 1 to be detected, and turning on a test power supply to read. When test data are read, the data are recorded after being displayed stably, and marks are made for finding abnormal stator bars. And after the experimental result is recorded, the next line bar can be detected.
(7) If the experimental result is not obvious enough, the specific position of the insulation defect can be determined by moving the position wrapped by the tin foil.
(8) And after the test is finished, the power supply of the instrument is turned off, the stator coil fully discharges to the ground, and then the wrapped tin foil paper is removed. Care should be taken to prevent the tinfoil paper from falling into the generator stator bore.
Case implementation
The power plant No. 3 generator has the capacity of 32.6MW, the rated voltage of 10.5kV and the rated current of 1792.5A. And during maintenance, carrying out forward pressurization surface potential test on the insulation boxes at the two ends of the winding bar, and adopting 12kV test voltage according to the actual running condition of the generator. It was found that the upstream side rod end 46 th, 98 th, 123 th, 148 th, 149 th, 150 th slot box leakage current exceeded the manufacturer's requirement of 10 mu. By looking carefully at the bar it is found that: oil stains are accumulated on the surface of the insulation box, and the insulation strength is reduced. Secondly, the epoxy clay is not filled and obvious gaps exist, wherein the No. 98 box epoxy clay has obvious holes. Thirdly, the epoxy clay is not well cured, individual boxes have cracks, and the surface has overheating traces. Fourthly, the notch part of the line bar is electrically corroded, and the insulating paint on the surface layer falls off. Fifthly, the surface of the washing glass rope for reinforcing the end part is dirty, and the hand-wrapped insulation of partial positions is loose. After the defects are detected and processed, the positive pressure potential test and the surface potential test are carried out.
The results are shown in Table 1. The corresponding values in the table are compared, and the surface potential method is proved to be capable of effectively detecting and removing the insulation defects at the end parts of the stator coil.
Watch (A)
Surface potential test data of No. 3 generator in certain factory
The foregoing description is only exemplary of the invention and is not intended to limit the spirit of the invention.
Claims (1)
1. A method for diagnosing insulation defects at the end parts of a stator bar of a generator is characterized by comprising a stator bar (1) to be detected, a detection probe (2), a measuring bar shell (3) is connected with a measuring bar handle (4) with a certain safe length, the detection probe (2) is connected to the end part of the stator bar (1) wrapped with tin foil paper or aluminum foil paper, and the measuring bar handle (4) is connected with an electrostatic voltmeter (5) and a microammeter (6) on a control console (9) through leads; the detection method comprises the following steps:
(1) the joints of the upper end part and the lower end part of the stator bar (1) are marked, and the labels are marked according to the position of the stator bar (1), so that the defect position is conveniently determined;
(2) during measurement, high-voltage live working safety measures are required to be executed, and a measurer wears an insulating boot and insulating gloves, stands on an insulating pad and is monitored by a specially-assigned person;
(3) the two ends of the stator bar (1) are wrapped with tin foil paper in a hand-wrapping insulation mode; the tin foil paper is tightly wrapped at the measuring part, and meanwhile, the tin foil paper cannot collide with the adjacent measured part, so that the error breakage caused by the increase of the measuring branch is avoided; keeping the distance of the tin foil paper to the ground to be more than 3 cm;
(4) adjusting a test power supply: the test power supply adopts a full-wave or bridge circuit for rectification, and the test voltage is selected as the rated voltage of the stator;
(5) adjusting the measuring range of the microammeter (6) and the electrostatic voltmeter (5) according to the test voltage: the measuring range of the microammeter (6) is larger than the ratio of the test voltage to the insulation resistance element, and 100-; the measuring range of the electrostatic voltmeter (5) is larger than the test voltage;
(6) overlapping the detection probe (2) on the tin foil paper at the end part of the stator bar (1) to be detected, turning on a test power supply, reading after the indexes of the static voltmeter (5) and the microammeter (6) are stable, and considering that insulation has defects when the voltage or current is abnormally large or exceeds a standard value; after the corresponding record is made, the detection of the next line bar can be carried out;
(7) if the experimental result is not obvious enough, the specific position of the insulation defect is determined by moving the position wrapped by the tin foil;
(8) and after the test is finished, the power supply of the instrument is turned off, the stator coil fully discharges to the ground, and then the wrapped tin foil paper is removed.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911332697.1A CN113009286A (en) | 2019-12-22 | 2019-12-22 | Method for diagnosing insulation defect at end part of stator wire rod of generator |
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| CN201911332697.1A CN113009286A (en) | 2019-12-22 | 2019-12-22 | Method for diagnosing insulation defect at end part of stator wire rod of generator |
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| CN113009286A true CN113009286A (en) | 2021-06-22 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116953036A (en) * | 2023-07-14 | 2023-10-27 | 珠海杨杋科技有限公司 | Charging roller detection method and system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116953036A (en) * | 2023-07-14 | 2023-10-27 | 珠海杨杋科技有限公司 | Charging roller detection method and system |
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