There are several Competence range AEG ovens as well as a number of Electrolux branded built in oven and cooker models that all use a little thermostat, marked as a "ZN Limitor" controls the cooling fan on the oven models listed below. When the limit thermostat goes faulty the cooling fan will normally fail to run causing the oven to overheat and cut out. When this happens the oven will go totally dead after about ten to fifteen minutes, no lights, no clock or anything else will power up.
The cure is, almost 100% of the time, to simple replace this little thermal limiter and you're back in business again.
The part is easy to replace for most competent DIY capable people and available from this link along with photos of where the limiter can be found and is mounted.
Models affected are as shown on the replacement spare part page form the link above although