Analys av åldrande på reläskydd : På Forsmarks kärnkraftverk

Sammanfattning: Forsmark's nuclear power plant have expensive and important machines, which means that good relay protection is a must. But as the plant ages, the relay protection need to be revised and replaced as a preventative measure. Through analyzes of old replaced relays, a status can be given for the older relay protection that are still used inside the plant. By measuring and comparing the relays with the manufacturer’s specifications, the status of relays can be given. This includes switch-on and switch-off times, switch-on and switch-off values, resistance in coils, voltage strength tests, etc. Just by visually inspecting the relays, a brief status of the relay can usually be given. The results show that only some of the manufacturer’s specifications are affected by aging. Of the relays tested, only the voltage strength tests had changed with age and that was on the oldest relays. Results also show that heat affects the aging of relay protection in a negative way. The protection relays show some aging and the project that is ongoing at Forsmark to replace old protection relays with new ones is recommended to continue as planned with some modification. None of the relays that were replaced as a preventive measure had any type of malfunction and were not in an urgent position to be replaced. The ones recommended to be replaced first are relay protection units that are constantly on because they age faster due to heat.