“…It requires enhanced relay technologies allowing frequent updates of the frequency threshold assigned to each relay. They may also use additional ‘richer’ measurements such as rate of change of frequency [16–18], the second‐derivative of frequency [19], a forecast of the frequency evolution [20, 21] and/or voltage measurements [22, 23]. Indeed, improving the adequacy between the amount of load shed on one hand, and the initial power imbalance on the other hand, may require: - Additional measurements, to better estimate the appropriate UFLS action to apply at any given time (ex ante), and also to find out the appropriate reaction to a given power imbalance in near real‐time when it occurs ( ex post );
- A control infrastructure, including a communication system, that will apply and automatically update some new ‘dynamic’ UFLS scheme;
- A proper distribution of UFLS relays into the transmission system in order to take into account the entire load of the EPS.
By comparison with this futuristic view on the topic of UFLS technology, recall that our assumption in the remainder of this paper is that the parameters of existing UFLS relays may currently not realistically be updated more than about once a year.…”