Casing and the insulation of the high voltage insulator test method a, casing insulation test preventive test project mainly include: main insulation and capacitance type casing at the end of the screen to ground insulation resistance test and the tanδ
After overhaul or when it is necessary for dissolved gas in transformer oil chromatographic analysis, ac withstand voltage test and partial discharge test.
1, insulation resistance test of measuring insulation resistance for a preliminary inspection of casing pipe insulation, before and after the ac withstand voltage test shall be performed.
Before you measured in dry clean cloth wipe the surface dirt, and check whether there is any crack and burn on casing.
Application of 2500 v megohmmeter is measured, the two end of the megohmmeter button respectively in the casing of the guide bar and flange.
2 measurement of capacitance and dielectric loss tangent and measuring 20 kv and above the pure porcelain bushing dielectric loss tangent and the capacitance value is an important indicator of high voltage insulation casing.
Because casing degradation, be affected with damp be affected with damp, etc will lead to the increase of its dielectric loss Angle tangent, so according to the change of dielectric loss Angle tangent is more sensitive to reflect the degradation of the insulation and other local defects.
Installed on the power equipment of high pressure casing, the metal shell flange and equipment directly connected and grounded.
Measure these tan&delta casing;
Value, the * should be connected to the casing first fuses or winding disconnect.
In addition to the grounding screen by small casing raises available are wiring method to measure the reverse connection method is commonly used in measurement.
When measuring casing of dielectric loss tangent, sometimes tend to measure capacitance core of dielectric loss tangent, or only measuring casing conductive grease paper core of pumped or tan&delta between measuring terminal;
Without measuring terminal or dielectric loss tangent pump pressure terminal.
Due to internal casing early water be affected with damp be affected with damp, humidity and moisture into the near the screen at the end of the insulating layer, only accounts for the proportion of the total volume is very small, often reflect not to come out, it gives the safe operation of the electrical equipment.
3, ac withstand voltage test tube after the handover, or overhaul is needed to test transformer equipment to carry out ac withstand voltage test, the test should first will be tried casing surface clean.
For oil filled transformer or oil circuit breaker or device on the sleeve, bottom should be immersed in the insulating oil, flange connected to the tank shell and grounding, grounding screen earthing at the same time, the test voltage applied on the guide bar.
4, partial discharge measurement of 66 kv and above capacitance type casing can be measured after overhaul as auxiliary partial discharge test.
Second, the high voltage insulator insulation test and post insulator suspension insulator preventive test items include: zero insulator detection, measuring insulation resistance, ac withstand voltage test, the equivalent of insulator surface unclean salt density measurement, etc.
1, insulation resistance testing good high voltage insulator of clean and dry, the insulation resistance is very high.
Electrical porcelain have crack, insulation resistance in general, not significantly lower.
When electric porcelain cracking in moisture and dust and dirt intrusion, insulation resistance will be decreased significantly, only for hundreds or even tens of ohms, use can be clearly detected by megger.
Measure the multielement post insulator insulation resistance of each component, should be in the layered agglutination round copper wire, and then to the megohmmeter, lest in different position of the insulation resistance measured numerical differ is too big, causing false judgment.
'Regulations' regulation, with 2500 v, when measuring insulation resistance by megger are multielement post insulator and every piece of suspension insulator insulation resistance should not be less than 300 m & Omega;
500 kv suspension insulator insulation resistance of not less than 500 m & Omega;
2, ac withstand voltage test for post insulator unit parts, ac withstand voltage is effective, * * a simple test method.
Preventive test, ac withstand voltage test can substitute for measuring voltage distribution and the insulation resistance, or use it to * after the judgment in the detection of the insulator.
For all levels of high voltage insulator ac withstand voltage test, the voltage of post insulator and suspension insulator ac withstand voltage test, according to the test voltage standard pressure for 1 min, does not occur in the process of pressure and pressure jump arc as qualified.
Within the 35 kv substation running on post insulator, can undertake whole pressure along with the bus, test voltage is 100 kv, the time for 1 min.
After the pressure, must be measuring insulation resistance of each agglutination component, in order to check out the unqualified components.
For wall bushing, pressure should be according to actual condition.
For transformer wire casing, such as system, 35 kv voltage grade casing should be full of oil, when testing the bottom half should be immersed in the insulating oil pressure again.
3, contour surface unclean quantitative evaluation of high voltage insulator salt density measurement & other;
Dirty & throughout;
The degree of use * to a wide range of a kind of method.
Salt density method is equivalent to high voltage insulator surface filth density according to the conductivity converted to NaCl content on unit area of a representation.
In particular is to use 300 ml of distilled water, cleaning and dissolved the next piece of filth on the surface of the high voltage insulator, gradually into the NaCl in another glass of 300 ml of distilled water, until 2 cups of water, the electrical conductivity of the same are used in the amount of NaCl divided by the area of the high voltage insulator, and the result is called the equivalent of the high voltage insulator salt density.
When the salt density value in excess of the prescribed, measures should be take appropriate cleaning according to particular case.
Equivalent * big advantage of salt density method is intuitive and easy to understand, easy to promote.
Its defect is don't reflect the impurity composition, does not reflect the content of electrical material, does not reflect the distribution of impurity on the insulator.
Filth and filth is divided into four stages: sedimentary, be affected with damp be affected with damp, the formation and the development of local electric arc of dry area, so the equivalent salt density method of measuring results only reflect the result of the accumulated filth, does not reflect the process.
Can't reflect the status of the development of local electric arc.
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