Transient protection is used in electrical and electronic systems primarily to achieve a required level of system reliability - to minimise life cycle cost and maximise system utility. Unfortunately, conventional transient protection techniques do not permit their contribution to system reliability to be confidently assessed.The thesis uses the reliability based design objective, an objective common to all modem electrical design processes, as a framework for research. In the first chapters, the application of reliability based design using conventional protection techniques is studied. The main conclusion is that although the reliability of some conventional protection devices (eg the gas arrester) may be able to be managed with what can be realistically predicted about transients in the field, the reliability of the important group known as the clamping devices, cannot.The thesis goes on to analysis the deficiencies in clamping device design which prevent their reliability being managed and propose an alternative protection strategy - a strategy which is based on a shunt/series protection configuration which over-comes the deficiencies of clamping device designs. The thesis includes a theoretical analysis of the new concept and documentation of its testing.The thesis concludes with a summary of the theoretical and proven advantages of the new approach.The thesis includes appendices covering supplementary work completed as part of the thesis research. These appendices document the development of a transient waveshape generator for the reliability testing of low power transient protection devices with novel transient waveshapes, the novel waveshape testing and failure analysis of commercial avalanche diodes, and the theoretical analysis of lightning induced transients in short transmissions lines.