Abstract:
Typically, when fault occurs, DG must be disconnected within 0.1 s due to the Grid Code of the utility in Thailand. This DG disconnecting time is specified to prevent the impact of DG on power systems, e.g. Reach Reduction, Islanding, Out-of-Phase, etc. One of the most severe impacts is Out-of-Phase. However, if DG remains connected in the system during a fault occurrence, it may provide some advantages for DG owner and load especially the reduction of voltage sag on sensitive equipment. This thesis analyzes the impacts of DG disconnecting time on protection system and voltage sag. The analysis is based on the operating time of utility protective device, the automatic reclosing time of utility protective device, fault duration and DG disconnecting time. In addition, the thesis analyzes the impacts of DG location, DG protective device settings and DG operating characteristics by comparing with PEA Grid Code. In DG protective device setting, this thesis focuses on both Pickup Current and Time Dial Setting. In DG operating characteristic, this thesis considers Operation Modes, Power Factor, Terminal Voltage and Transformer Connection Type. Furthermore, this thesis determines an appropriate DG protective device setting and DG operating characteristics by using Genetic Algorithm.