30-07-2009, 04:12 PM
A high degree of security for normal operation of larger inter connected power system is required one of the requirements of reliable service in electrical power system is to maintain the synchronous machines running in parallel with adequate capacity to meat the low demand with the growing stress on present days power systems, the potential impact of faults and other disturbances on their security is increasing.
Protective relays in the power system detect faults and trigger the opening of circuit to isolate the fault.The power system can be considered to go through changes in configuration in three stages, from a prefault, faulted to a post faults system. The analysis required knowing whether following a contingency, the power system will survive the transients and moving to a stable operating condition is referred to as dynamic security assessment. The transient stability assessment of power system is done to appraise the system capability to with stand major contingencies and to suggest remedial actions i.e., means to enhance this capability.