The fact that the average service field of most insulating polymers used in high voltage systems is only a fraction (typically ~10%) of their breakdown strength has lead to the belief that the existence of space charges within the insulation may well be the key factor for its long-term electrical degradation. There has been a growing interest nowadays to investigate further the energy dissipation of these mobile and trapped charges and this dissipation process is associated with the emission of visible photons, a process known as electroluminescence (EL). Optical emission has been generally regarded as a direct proof of excited and chemically reactive states within the molecules so the study of the phenomenon could give a better understanding on the processes leading to polymer degradation. The aim for this project is to investigate the factors that influence the occurrence of EL under uniform electric field with the application of 50Hz ac stresses. EL intensity level was observed using a CCD camera and a set of filers were used to examine the spectral characteristics of this light emission. In addition to this, phase-resolved EL measurements were also obtained in order to see how the charge injection processes affect EL behaviour. A dynamic bipolar charge recombination model has been developed in order to allow the simulation of the phenomenon in a plane-plane electrode system.