Views: 5 Author: Site Editor Publish Time: 2019-10-11 Origin: Site
Analysis of The Standard Operation Method of The Leakage Tracking Tester
The Tracking Indices of Solid Insulating Material is used for simulating the tracking index and the tracking index of the leakage resistance of the electrical insulation products and the products of the household electrical appliances and the products. It is simple, accurate, reliable and practical.
Experimental principle: The leakage tracking test is carried out on the surface of a solid insulating material, between a platinum electrode of a specified size(2 mm*5 mm), applying a certain voltage and timing (30 s) a fixed height (35 mm) to drip the specified droplet volume. Liquid (0.1% NH 4CL) was used to evaluate the resistance of the surface of solid insulating materials under the combined action of electric field and contaminated medium, and its Comparative Tracking Index (CTI) and Proof Tracking Index (PTI) were determined.
1. Operation Steps
Test of sample
The electrode should be cleaned before each test, check the distance between the two electrodes. (Corrected with the supplied width correction plate. The calibration plate is engraved with two scale lines, 30 mm and 40 mm respectively. This is used to correct the height of the drop needle from the sample, which is usually corrected by the factory.)
1) Place the sample to be tested on the support plate. The surface of the test piece is uneven (the height adjustment rod is installed at the bottom of the support plate), and then the blades of the two electrodes are pressed against the sample according to the specified force.
2) Check the distance between the two electrodes to ensure good contact between the electrode and the sample. If the edges of the two electrodes are corroded, they should be sharpened again. The voltage is adjusted to a suitable value that is divisible by 25, and the resistance of the circuit is adjusted so that the short circuit current is within a given deviation. The electrolyte was then allowed to drip on the surface of the test until electrical tracking was formed to cause damage or until 50 drops of electrolyte were dropped.
3) If a current of 0.5 A or more flows through a conductive path between the two electrodes on the surface of the sample for at least 2 s, then the overcurrent relay operates or if the relay does not operate and the sample burns, the sample is considered to have occurred damage.
4) If multiple tests are performed on the same sample, care should be taken to have sufficient spacing between the test points so that the splashed dirt on the test points does not contaminate the other test surfaces.
5) Harmful or toxic gases may be generated due to testing. Therefore, press the “Exhaust” button before the test to remove these gases.
2. Determination of CTI
1) Adjust the voltage to a pre-selected value and perform 50 drops of the test sample without damage or within 50 drops until damage occurs. A lower or higher voltage is then applied to the other test points of the sample for testing until the maximum voltage at which the 50 drops are not destroyed at five different points. The maximum voltage is CTI ( For example CTI 425). It means that the maximum voltage value is lowered by 25 V and the other five points are tested one more step, and the sample is not damaged under 100 drops. Some materials may not meet the following requirements. For these materials, it is necessary to determine the maximum voltage value at which the sample can withstand 100 drops or more of the solution at five test points and attach this voltage value to the CTI, for example CTI 425(375).
2) If the performance of the material is not known, the starting voltage can be selected from the middle of the test range, for example 300V. If the sample withstands 50 drops, increase the voltage and test again; if less than 50 drops of the sample break, lower the voltage and test again. The increase or decrease of this voltage should be a multiple of 25V or 25V. The test was continued until five samples were obtained to withstand the highest voltage value of 50 drops.
3) For most materials, a voltage of 50 drops (the sample withstands 50 drops at this voltage without forming a trace) is considered to be close to the asymptotic value. The test, which is 25V lower than the voltage of 50 drops, is to further demonstrate the fact that the voltage at which the material is subjected to 100 drops without electrical tracking is lower than the voltage of 50 drops, and the voltage is further away from the asymptote.
Note: At higher voltages and more than 50 drops, the sample may be destroyed by the accumulation of solutions and contaminants on the dents and small holes in the surface of the sample (as indicated by the action of the overcurrent relay), rather than Caused by a conductive path. At this point, the test must be repeated. If the results specified in the definition are not obtained, they are explained in the test report.
3. Determination of PTI (electric trace resistance)
1) In the standards of material specifications or electrical equipment specifications, or other standards, if only one tracking resistance test is required, the test shall be carried out according to 1, but the test is carried out only at a specified voltage. A specified number of samples shall withstand 50 drops without damage.
2) It is recommended to use five samples. In special cases, fewer samples may be specified.
3) The preferred test voltage is: 175V, 250V, 300V, 375V, or 500V. The tracking index is abbreviated as PTI.
4. Determination of erosion
1) Samples that do not have electrical traces should be cleaned of debris adhering to their surface or decomposed material loosely attached to them, and then placed on a flat gauge plate. The maximum erosion depth of each sample was measured with a probe having a hemispherical end and a diameter of 1 mm, accurate to 0.1 mm. The maximum value of five measurements should be noted in the test report.
2) When the test is performed according to 2, the depth of erosion shall be measured on five samples tested under the voltage corresponding to CTI.
3) When tested in accordance with 3, the depth of erosion should be measured on a sample that withstands 50 drops at a specified voltage.
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