Galvanic isolation

From HvWiki

Galvanic isolation is a barrier between two systems that stops a direct current from flowing from one system to the other.

Transformers and optocouplers are typical galvanic isolators, normal capacitors are not typical galvanic insulators since they are not made for that purpose and are usually not reliable enough for that application.

An autotransformer does not provide galvanic isolation and must be combined with an isolation transformer when appropriate.