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 Revision Standard - Superseded. Revision of IEEE Std 741-1997. This standard prescribes criteria that establish protection requirements for Class 1E power systems and equipment. It describes 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. It includes testing and surveillance requirements. It does not include plant physical design requirements to protect against events such as pipe whip, fire, dropped load, etc.