Improving power quality by optimizing the protection of distribution systems

This paper discusses the effects of different short circuit faults on the voltage profile across the distribution system. The behavior of typical distribution feeder protection or substation protection systems is analyzed from the perspective of the definitions of voltage related power quality events. Multi-functional protective intelligent electronic devices (IED) are then considered and it is demonstrated that by using all available advanced distribution protection schemes and programmable logic functions the user can reduce the effect of short circuit faults on sensitive loads supplied from the distribution substation. Combinations of instantaneous, definite time and inverse time-delayed phase, ground and negative sequence elements will result in a significant reduction in the duration of the fault. This will lead to changes in the voltage level/time characteristics of the fault condition and reduced the probability for the costly interruption of voltage sensitive processes.