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The integration of numerous small-scale generators into existing power systems is anticipated to impact the operation, control and protection of such systems. In particular, maintaining voltage and frequency stability within defined limits is more onerous and requires investigation. The effect of protective limiters and characteristics such as the genuine inertia of the generation set must be taken into consideration in planning studies in order to accurately represent the overall dynamic characteristics of distributed generators. This paper focuses on the investigation of these issues by studying a small-scale reciprocating engine/generator set. The experimental procedures used to determine the genuine inertia of the test rig are described, and the influence and importance of considering the action of protective limiters such as voltage-per-hertz (V/Hz) in stability studies is demonstrated. This work is directly relevant to the review of current UK stability limits, and to the generation planning framework supported by the Scottish Executive.