Identifying power fluctuations in mains supply - preventing undesired release of remote protective circuit breakers from transient deviations by generating blocking signal from measured impedance values

摘要

A blocking signal for the remote protection unit is produced by a timed derivation of a power-related electrical value, the sign (positive or negative) of which-depending on the direction of the transient power swings is determined from the flow passage direction of the impedance local curve in the complex plane. The block signal- as a derivation of the electrical value which is proportional to the difference between the wattless and the useful power at the measurement place- is determined by an equation using alterations in these values. ADVANTAGE - Improves reliability of electrical supply mains by protecting distance protection units against unnecessary switch off during power swings.