Dr Greenwood is presently Philip Sporn Professor of Engineering at Rensselaer, the oldest engineering school in North America. His professional career, which started with a B.T.-H. apprenticeship in 1940, has been spent about equally in industry and university environments. His particular interests are in power switching equipment and the interactions of such equipment with power systems. He was one of the small team that developed the first high power vacuum interrupters for the General Electric Co. (USA) in the 1950s and has been involved with this technology ever since. He holds many patents and has published widely on this subject. He is the author of Electrical transients in power systems (John Wiley & Sons, 2nd edn, 1991).

Dr Greenwood is a life Fellow of the IEEE, an Attwood Associate of CIGRE and a former Visiting Fellow of Churchill College, Cambridge.