Introduction of preventive project detection before voltage transformer is put into use
Preventive testing is an important link in the operation and maintenance of power equipment, and it is one of the effective programs to ensure the safe operation of power equipment.
Transformer
In order to better ensure that the various technical indicators of voltage transformers meet the standards, power engineering construction companies will carry out preventive tests on transformers before they are put into use, which is of great significance to ensure the safe and reliable operation of power plants.
One, measure the insulation resistance of the winding
Purpose To check whether the transformer as a whole is damp or deteriorated. The operation is that a 2500V megohmmeter is used for the primary winding, and a 1000V or 2500V megohmmeter is used for the secondary winding, and the non-tested winding should be grounded. Consider the influence of various external factors such as air humidity and dirt on the surface of the casing during measurement. Temperature has a great influence on insulation resistance. The temperature should be recorded during operation for easy calibration. You can also wait until the temperature of the winding under test is stable before performing the test.
2. Dielectric loss factor tgδ
Measuring the dielectric loss factor tgδ of the primary winding of a voltage transformer of 20KV and above together with the bushing can quickly find problems such as damp insulation or damage to the bushing.
3. Chromatographic analysis of dissolved gas in oil
Dissolution chromatography analysis in oil plays an important role in diagnosing electrical discharge defects. The index values to be noted are: hydrogen 150pm; acetylene 2ppm: total hydrocarbon 100pm. When the new voltage transformer oil contains acetylene. There are two situations for abnormal acetylene content: the first is the floating potential discharge of the core screw, and the second is the discharge defect of the winding insulation. In the triple frequency induction withstand voltage test, the acetylene content in general oil can reach 10ppm. The acetylene content should be tracked during operation. If the acetylene content continues to increase, other tests, such as partial discharge, induction withstand voltage test, etc., should be used to find out the cause of the acetylene gas.
Four, AC withstand voltage test
There are two ways to pressurize the AC withstand voltage test of electromagnetic voltage transformer. The first method of external construction frequency test voltage is suitable for the AC withstand voltage test of fully insulated voltage transformers with a voltage of 35kv and below in the second store. This test is the same as the AC withstand voltage of current transformers. For 110kv and above cascade type or graded insulation type voltage transformers, the test should be conducted in the way of double-frequency induction withstand voltage.
5. Partial discharge test
According to the national standard "Measurement of Partial Discharge of Transformers" (GB5583-8W for partial discharge measurement of current transformers, the preload voltage applied to the high-voltage end of the current transformer under test is more than 2 times the normal operating voltage. This pair Current transformer tests are allowed. For electromagnetic voltage transformers, the iron core has begun to saturate under the rated voltage of the rated frequency. For the JCC2-220 type transformer, the iron core is even below 80% of the rated voltage. Start to saturate.
