Abstract:
Due to dependency on Plug Setting (PS), Time Dial Setting (TDS), size of the network, more than one back-up relays for one primary relay and other technical constraints, coordination of Directional Overcurrent Relays (DOCRs) is an extremely constrained and nonlinear optimization problem. Here a new Gravitational Search (GS) based algorithm is presented for achieving optimal coordination of directional overcurrent relays. This algorithm utilizes user defined characteristic for inverse time overcurrent relays than the predefined standard curves. The user defined relay characteristic deals with constants that control the shape of the characteristics as variable adjustable values which are optimally chosen along with TDS and Plug Setting Multiplier (PSM). The performance of the proposed scheme has been evaluated for near end faults on 8-bus & 15-bus test systems and for different fault locations (near-end, far-end and middle point) on IEEE 30-bus distribution network. The time of operation of some of the primary relays at different fault locations on IEEE 30-bus distribution network is also shown. At the end, comparative evaluation of this GS based algorithm with other optimization algorithms proposed in the literature clearly indicates its effectiveness and superiority in terms of the sum of total primary relays operating time.
