This paper deals with a detection system of the inter-area oscillation between central and southern areas of Thailand power system using GPS-based synchronized phasor measurement units (PMUs). The PMUs are installed at two universities representing both areas. The phasor data of a single phase voltage 220 V are measured by PMU via power outlet. The proposed system not only requires low capital cost but uses internet for data transmission. The wavelet decomposition and least-squares error are applied to identify the eigenvalue corresponding to inter-area mode.
