The size of the device is determined by the amperage rating. IEC 309 plugs and sockets are widely used for industrial purposes. Also known as CEE 17. IG insulates the grounding of the sensitive load equipment from the conduit and raceway grounding system and controls the connection to the power grounding system. Because those wiring documents consider the sitation in Finland most of the documents listed in this section are written in Finnish.
Many books mention any impurities only in passing.
But it's not that simple. The mains power can contain radio frequency interference, fluctuations in the voltage, high voltage spikes and even short breaks in power distribution.