A description is given of a technique which has been developed for the investigation of the electrical properties of oil-impregnated paper, with special reference to the type of lapped-paper dielectric used in power cables.The equipment described is versatile, permitting a wide range of electrical tests to be made on one type of specimen and enabling the effect of variations in construction or component dielectric materials to be assessed rapidly and conveniently. The system is well suited for routine quality control as well as for research or development.