Power System Stability

Power Systems broadly comprises of interconnected utility synchronous machines via transmission systems and utility/consumer loads supplied through transmission and distribution network. For stable and reliable operation the following conditions must be satisfied

- The power supply and power demand in the system must always be satisfied and be in equilibrium conditions during normal and dynamic changes in the system. Particularly during pre- and post dynamic events, the system voltage, frequency and equipment loadings shall be within normal limits ensuring quality of power supply and acceptability of system operation. Quality is mainly determined from the system frequency, system bus voltages, equipment loadings and harmonics.

- The operating limits of the equipments shall remain within normal operating limits or shall quickly return to normal limits following dynamic events. These dynamic events can be large disturbances following which the system should be able to continue and service the loads without loss of quality, loss of load. The response of the system to large disturbances and its ability to return to normal operating conditions is generally termed transient stability or large signal performance of the system. (http://www.powerapps.org/PAES_TStability.aspx )

- The heterogeneous system of synchronous machines and their controllers together with load and other system dynamic characteristics shall be stable, so that the system can transit from one operating condition to another without sustained oscillations limiting power transfers. This is generally referred to us small signal stability. (http://www.powerapps.org/PAES_Dynamic Stability Or Small Signal Stability Studies.aspx )

- The load characteristics and the power supply characteristics of the system shall be in tune with each other so that the load voltages are always healthy without any significant low voltage problems and its consequences which may lead to loss of system load and service. This problem is generally termed voltage stability problem.(http://www.powerapps.org/PAES_VoltageStability.aspx )