BS EN IEC 62961:2018 pdf free download

BS EN IEC 62961:2018 pdf free download Insulating liquids – Test methods for the determination of interfacial tension of insulating liquids – Determination with the ring method
7.3 Determination of the surface tension of water used for the test
Start the measurement according to the manufacturer instructions.
Introduce water into a clean vessel to a level of 20 mm to 30 mm. Slowly raise the platform and the measurement vessel until the ring is immersed in the water phase. The ring shall be at least 3 mm below the water surface and centred in the vessel. Ensure that the ring is properly wetted and not repelled from the water surface.
Depending on the test temperature, a value of 70 mN/m to 73 mN/m shall be obtained. If lower values are found, repeat cleaning of the sample vessel and the ring. Check the source of the sample water in respect to surface active contaminants. In exceptional cases, search for a fresh sample of water from another source (see also 6.3).
If the water quality (according to 6.3) and the cleanliness of vessels (according to 6.1 ) and the ring (according to 6.2) are validated in the testing laboratory by an established and reproducible procedure, it is not necessary to carry out the determination of the surface tension of water (according to 7.3) prior to each sample, but once in a daily successive series of tests.
7.4 Determination of interfacial tension between water and insulating liquid
Introduce water into a clean vessel to a level of 20 mm to 30 mm. Slowly raise the platform and the measurement vessel until the ring is immersed in the aqueous phase. The ring shall be at least 3 mm below the water surface and centred in the vessel.
• Then overlay the water with a 1 5 mm to 20 mm layer of insulating liquid using a pipette or a clean narrow beaker with spout (if plastic single use syringes are used it shall be verified that the material does not interact with the liquid). No bubbles shall be present. Complete this process within 30 s.
• Begin the time counting.
• Measurement shall be completed within 1 80 s ± 30 s.
• The measurement value shall be taken at the time closest to 1 80 s (this time shall not differ from 1 80 s by more than 30 s).
• Ascertain whether the obtained value is to be corrected or if the correction factor has already been implemented in the software.
NOTE 1 Some instruments can automatize the procedures above.
NOTE 2 A series of several consecutive measurements on the same sample interface (different surface age) within the given time frame can be made.