Application of Synchronous Power Coefficient to Assess Steady State Stability in a Multi-Machine Power System

Abstract

Operation of interconnected power system network involves connection of many generators. It is required that all the generators must remain synchronized at all times when operating within their rated capacity. Unabated continuous grow in system loading may lead to machine running out of synchronism. This paper assessed steady state stability of power system employing synchronous power coefficient (SPC) using the Nigerian 28-bus, system. Variation in system loading will result in variation of output power for each generator. SPC is the criterion that determines whether generators remain in synchronism whenever there is a variation in load using the kinetic energy stored in its rotating masses. It is a measure of safety of operation of power system steady state stability (SSS). To determine the SPC, power flow was carried out using Newton-Ralphson method with varying loads. The reduced admittance matrix (RAM) for Yீீ was formulated from the bus admittance matrix. The voltages behind steady state reactance of the generators were determined and used in conjunction with RAM to determine power transfer between generator-generator. Power flow was repeated with variation of loads in step of 30%. SPC was simulated with consideration of 130%, 160% and 190% of active load. Utilizing MATLAB programming language, the results revealed that the system is stable for 130% and 160% load variation and unstable when 190% of rated load is suddenly applied to the network. This work is a pointer to the percentage of sudden load that can be connected without the system running out of synchronism