Apparatus for use in disturbance evaluation systems based on disturbance extraction from an electrical network

摘要

Apparatus (1) for use in disturbance evaluation systems based on disturbance extraction, which apparatus (1) comprises measuring means for obtaining signal frequency both before (4) and after a disturbance (3) in an electricity network but excluding use of the disturbance transient itself, and interpolation means (5) for interpolating frequency across the disturbance interval to reflect the underlying frequency trend (9) uninfluenced by the disturbance transient. The apparatus (1) may include: (i) at least one delay means (2) for receiving at least one analogue or digital signal (6) from the electricity network; (ii) at least one first access point (P) at a first part of the delay means (2); (iii) at least one second access point (Q) at a second part of the delay means (2), and the apparatus (1) being such that: (iv) the measuring means comprises: (a) a first frequency derivation means (3) for processing a set of access point outputs from the first access point and providing at least one measure of frequency (7) after the disturbance; and (b) a second frequency derivation means (4) for processing a set of access point outputs from the second access point or a delayed output means, for providing at least one measure of frequency (8) before the disturbance; and the interpolation means (5) receives the measure of frequency (7) after the disturbance and the measure of frequency (8) before the disturbance, and provides a measure of frequency (9) as a function of time over a period of interest, which comprises the disturbance interval and either side of the disturbance interval.