This paper investigates and analyzes the measured power-quality results of an onshore wind farm with three wind-turbine generators connected to the power grid of Taiwan Power System. The three 2-MW wind permanent-magnet synchronous generators of the studied Taichung Power Plant's onshore wind farm are connected to the extra-high-voltage bus of 161 kV through a step-up three-winding distribution transformer of 161/23.9/11.9 kV, 60/30/30 MVA. The measured results were recorded from October 8th, 2015 to November 13th, 2015 for total 37 days. The recorded power-quality results include current harmonics, voltage flickers, and voltage variations. Special output-limitation outcomes of the studied wind farm were also recorded. According to the analyzed long-term measurement results, the power-quality indices such as system frequency, voltage variations, voltage flickers based on ΔV10, and total demand distortion of current at the point of common coupling can meet the grid code of Taiwan Power Company.