An special protection system implementation-based on an isolated and longitudinal power system

Special protection systems or system protection schemes (SPS) is art for power system, i.e. there is no standard SPS solution for different systems. This paper presents SPS concept to solve transient instability problem in an isolated and longitudinal power system. In this power system, usually, the flow direction is south to north (STN), which means northern area is load center. The power system will encounter transient unstable situation as bulk STN power flow. In order to confirm the relation between transient instability and STN power flow, small signal stability (SSS) and voltage stability (VS) are studied. A result is obtained that STN power flow is the main factor to affect transient instability after comparing the results of SSS and VS. The approach is to analyze relation among STN power flow and stabilities. These results are tabulated a look-up table. The control mechanism has to be made by altering relay settings of STN transmission lines. The function of SPS can assist operators to maintain system stable against N-3 contingency.