Low-voltage switchgear and controlgear - Part 6-1: Multiple function equipment - Transfer switching equipment (IEC 60947-6-1:2005 + A1:2013) (english version)
Electricity metering equipment (AC) - General requirements, tests and test conditions -- Part 21: Tariff and load control equipment (IEC 62052-21:2004 + A1:2016) (english version)