ČSN EN 61643-351

Surge isolation transformers (SITs) are used for signal transformer applications with signal levels up to 400 V peak to peak. SITs are transformers, with or without an internal-winding screen, with a rated impulse withstand voltage greater than the peak voltage of the expected common-mode surge environment. SITs are applicable to components for surge protection against indirect and direct effects of lightning or other transient overvoltage. SITs are used to mitigate the onward propagation of common-mode voltage surges. This part of IEC 61643 defines test circuits and test methods for determining and verifying the SIT surge parameters. Preferred performance values for key parameters are given. This part of IEC 61643 does not cover SIT operation under differential-mode lightning surge conditions.