The transient stability is greatly affected by the type and fault location. A three phase is generally more sever from point of view of the power transfer.
In the case of one machine connected to infinite bus an increase in the inertia constant M of the machine reduce the angle through which it swings in a given time interval offering there by a method of improving stability.
Following are the methods of improving the transient stability limit of a power system.
- Increase of the system voltages use of AVR.
- Use of high speed exciting system.
- Reduction in system transfer reactaence.
- Use of high speed re closing breakers.
Increase in the number of parallel lines between transmission points is quite often used to reduce the transfer renascences. It adds at the same time to stability of the transmission system.
As a majority of faults are transient in nature, rapid switching and isolation of unhealthy lines followed by re closing has been a great help in improving the stability margins.