Control techniques for power system stabilisation

The conventional PSS was first proposed earlier based on a linear model of the power system to damp the low frequency oscillations in the system. But they are designed to be operated under fixed parameters derived from the system linearized model. Due to large interconnection of power system to meet the load demand brings in deviations of steady-state and non-linearity to power system. The main problem is that PSS includes the locally measured quantities only neglecting the effect of nearby generators. This is the reason for the advent of Wide area monitoring for strong coupling between the local modes and the inter-area modes which would make the tuning of local PSSs for damping all modes nearly impossible when there is no supervisory level controller. Wide area control addresses these problems by proposing smart topology changes and control actions. Dynamic islanding and fast load shedding are schemes available to maintain as much as possible healthy transmission system. It is found that if remote signals from one or more distant locations of the power system can be applied to local controller design, system dynamic performance can be enhanced. In order to attain these goals, it is desirable to systematically build a robust wide area controller model within an autonomous system framework

Study of Surface Potential and Electric Stress on Traction Insulators

Optimal performance of traction insulators is essential to ensure reliability of railway traction electrification system. They are exposed to environmental degradation and vandalism due to the overhead erection in railway lines. The likely damages that can take place are cracks in the sheds, or shorting of sheds due to formation of conducting dust and moisture layer on the surface. Fault in one shed increases the stress on the healthy sheds, resulting in an undesirable deviation of the electric field and potential profiles of the insulator from the normal ones, which may also lead to a flashover across the healthy portions. Surface charge simulation method (SCSM) is used to find the potential and electric field for the most widely used traction insulators in the country, and the stress increment is studied. The simulation results obtained for both healthy and fault-imposed insulators are presented, The experimental results of dry and wet withstand tests are presented along with the leakage current performance for the traction insulators

Estimation of electric stress and surface potential for traction insulators

Traction insulators are solid core insulators widely used for railway electrification. Constant exposure to detrimental effects of vandalism, and mechanical vibrations begets certain faults like shorting of sheds or cracks in the sheds. Due to fault in one/two sheds, stress on the remaining healthy sheds increases, owing to atmospheric pollution the stress may lead to a flashover of the insulator. Presently due to non availability of the electric stress data for the insulators, simulation study is carried out to find the potential and electric field for most widely used traction insulators in the country. The results of potential and electric field stress obtained for normal and faulty imposed insulators are presented.Accepted versio