New protection co-ordination methods in the presence of distributed generation

During the recent past, the share of renewable power generation in the total production is increasing. Wind energy takes as a big part of the distributed generation. Dedicated wind farm networks are developing. These are characterized of extensive radial or closed ring networks with a high number of subunits connecting the wind mills to the network. As a consequence, conventional selective protection concepts lead to high fault clearing times or unselective trippings which become unacceptable under operational and economical aspects. This paper shows new protection grading principles which reduce the fault clearing times ensuring selectivity nevertheless.