February 7, 2018 We conducted a wide survey of frequency and ROCOF measurement challenges, across a range of network owners/operators/managers, equipment manufacturers, and academics. The most useful responses we had were from National Grid and Scottish and Southern Energy Networks (SSEN). As a result we have worked closely with them during the early stages of the project. In particular, we obtained useful real datasets captured during difficult network events which occurred on their systems in the past year(s). These have led to new insights into some of the real-time issues and problems that frequency and ROCOF-assessing relays need to deal with. As a result of this, we are producing a library of useful waveforms, and waveform generators, that enable us to reproduce, in simulation, some of the types of difficult waveforms which occur with high penetrations of renewables, during bad weather / storms, and close to difficult loads such as arc furnaces.