IEC 60112-2020 pdf download.Method for the determination of the proof and the comparative tracking indices of solid insulating materials
Méthode de determination des indices de résistance et de tenue au cheminement des matériaux isolants solides.
11.3 Determination of the maximum 50 drop withstand voltage
By inference from the sceening data, repeat the test procedure at an appropriate test voltage. using a new test specimen or site and determine whether the specimen withstands the test for the period up to at least 25 s after the fiftieth drop has fallen.
If the over-current device operated due to the occurrence of an air arc above the test specimen, the test was invalid, Repeat the test procedure at the same voltage using a new test specimen or site after cleaning the apparatus and following the procedure as described in Clause 8. If the same event occurs, repeat the test at lower voltages until a valid failure or pass occurs. Report the details of the tests (see 11.5).
NOTE I It can be impossible to determine the CTI of some materials because a valid failure cannot be achieved, the characteristic behaviour moving directly from withstanding the test period at one voltage to exhibiting air arcs at the next highest test voltage.
If the over-current device operated due to the passage of an excessive current across the surface of the test specimen, or if a persistent flame occurred, the specimen tailed the test at that voltage. Repeat the test on a new test specimen or site using a lower test voltage after cleaning the apparatus. etc. as described in Clause 8.
If none of the above occurred and at least 25 s elapsed after the fiftieth drop had fallen without the over-current device operating, the test is valid and the test specimen is considered to have passed.
If a hole has not formed through the test specimen during the test, repeat the test on a new test specimen or site, at higher voltages until the maximum voltage is established at which no failure occurred during the test period of up to at least 25 s after the fiftieth drop has fallen in the first five tests at that voltage. Five separate specimens or five sites on one plaque may be used for the tests after cleaning the apparatus and following the procedure described in Clause 8.
If a hole appeared through the test specimen, record the result, noting both that a hole was formed and the depth of the hole (the thickness of the test specimen or stack), and then continue the tests as described above.
NOTE 2 Where a hole is generated during a test, the further tests can be made on thicker specimens (up to a
maximum thickness of 10 mm) to gain additional information after cleaning the apparatus, etc. as described in
Clause &
The result of tests where a hole formed, irrespective of the test specimen thickness, are considered to be valid, but the formation of the hole shall be reported together with the depth of the hole (the thickness of the test specimen stack).IEC 60112-2020 pdf download.Method for the determination of the proof and the comparative tracking indices of solid insulating materials