This paper deals with the results of testing an electric field measurement system - completely designed by the authors - for monitoring voltage Flicker and harmonics in aerial power systems. To prove the viability of this technique, an electric field sensor (EFS) was installed in our University High Voltage Laboratory, and in the HV network near a steel mill. Using the output of the electric field sensor, the voltage perturbations in any of the mentioned scenarios were determined. The deduced voltage perturbations agreed with direct measurements using conventional capacitive and resistive voltage dividers and voltage transformers. This technique can be used where cost or physical location drawbacks make the use of conventional methods difficult.Instituto de Investigaciones Tecnológicas para Redes y Equipos Eléctricos (IITREE)