Power transformers - Part 3: Insulation levels, dielectric tests and external clearances in air
- Three categories of transformer are clearly identified together with the relevant test requirements, these are summarised in Table 1.
- Switching impulse levels are defined for values of Um > 72,5 kV.
- The procedure for Induced voltage tests with PD has been revised to ensure adequate phase to phase test voltages.
- The AC withstand test has been redefined (LTAC instead of ACSD).
- Induced voltage tests are now based on Ur rather than Um. - New requirements for impulse waveshape (k factor) have been introduced.
- Tables of test levels have been merged and aligned with IEC 60071-1:2010.
- Additional test levels have been introduced for Um > 800 kV.
- A new Annex E has been introduced, which sets out the principles used in assigning the tests, test levels and clearances in air.
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