Improvement of non-standardized directional overcurrent relay coordination by invasive weed optimization

The use of non-standardized inverse time curves for improving overcurrent relay coordination performance is presented in this paper. Since the use of same curve type does not guarantee curve-intersection-free in meshed systems, numerous violations of coordination constraints may appear. Hence, non-conventional time curves offer altenative solution as time curve design is determined for each relay coordination pair problem. The model and implementation of optimization algorithm for coordination must be capable of handling increased problem dimension and constraints. Also, different short circuit currents must be taken into account to guarantee the relay coordination over the entire coordination interval. The invasive weed optimization (IWO) algorithm has been adapted for the high dimension coordination problem and has been tested on several IEEE systems. Overall results expose the enhancement of relay coordination when using non-standardized inverse time curves and IWO.