This work presents an overview of radiation protection at high-energy electron accelerator facilities. By 'high-energy' we mean the energy domain beyond few tens of MeV, where electromagnetic showers are the determining and dominant factor in beam interactions with matter. We describe basic components of electron accelerators and their potential impact on radiation safety. We then concentrate mainly on sources of prompt radiation which distinguish these machines from other accelerator facilities. In other areas we only mention details relevant to electron machines. More comprehensive description of these aspects, such as shielding or safety systems, can be found elsewhere in this issue. General concepts presented in this review are complemented and illustrated by more specific examples in our follow-up work in this issue.