Modal estimates from normal operation of power systems

Oscillation frequency and damping of interconnected power systems have traditionally been determined from line switching or generator tripping. In a competitive environment, scheduling generation and limiting transfers to ensure the system remains stable bring cost impacts for the test. Another factor influencing the test is that the resulting oscillation must be significantly above the noise level from customer load variations. Examination of normal operation angle measurements across 1200 km in Queensland and power measurements in Victoria show that frequencies and damping of the modes can be determined. This paper presents a method for extraction of impulse response parameters with particular emphasis on separation of the modes close in frequency.