This standard provides the principal design criteria, design features, and testing requirements for the protection of Class 1E power systems and equipment supplied from those systems. It identifies special protection features that are needed where the requirements of nuclear power generating stations necessitate supplementing accepted industry practices. Revision Standard - Superseded. Criteria that establish protection requirements for Class 1E power systems and equipment are prescribed in this standard. The purpose of and the means for obtaining protection from electrical and mechanical damage, or failures that can occur within a time period that is shorter than that required for operator action, are described. Testing and surveillance requirements are included. Plant physical design requirements to protect against events such as pipe whip, fire, dropped load, etc., are not included.