For electricity suppliers, a very important goal is to have a stable operation and to consistently and reliably deliver electricity. A big threat to that operation is obviously equipment breakdown that could cause downtime. In high voltage equipment, its insulation could arguably be considered one of the most important component. When electrical insulation deteriorates, small cracks and voids will start to appear within the material. These voids have less insulating ability and will eventually not be able to withstand the high voltage and become conductive and cause equipment breakdown. Before this critical situation occurs, when the deterioration is not enough for the voids and voltage to cause a full arc, there will be small sparks or partial discharges occurring. There are already methods for sensing these partial discharges but this thesis focuses on a new promising method utilizing optical fiber Bragg Gratings as sensors. An advantage with optical sensor being their immunity to electromagnetic interference, making it theoretically possible for them to be placed in harsh environments where conventional methods could not be used. The project started with researching previously written material on this relatively uncharted area of application and continued on to successfully constructing an optical sensor for ultrasound. The techniques used for that sensor could then be brought into a high voltage lab to conduct testing on generated partial discharges. A new method of mounting the fiber Bragg grating inside an insulation material for testing with partial discharges was created. The results were not final but showed promising potential in this kind of application for optical fiber Bragg gratings to exist.