Voltage sag assessment and installation of the sag compensator for HANARO

Electric power is essential for all industrial plants and also for nuclear facilities. HANARO is a research reactor which produces a 30 MW thermal power. HANARO is designed to be tripped automatically when interruptions or some extent of sags occur. The reactor experiences a nuisance trip as often as the unexpected voltage sag and/or momentary interruption occurs. HANARO research reactor has four SORs and four CARs. The SORs and CARs are neutron absorbing rods. The SOR is a part of the reactor protection system(RPS). The RPS is a safety class system and it is used to shutdown the reactor by dropping the SORs if certain parameters exceed their safety limits. The CAR is a part of the reactor regulating system (RRS) which is used to attain and maintain specified power level by control the reactivity of core in the HANARO reactor. The four CARs are connected to a driver through a magnetic clutch and driven by four independent stepping motors. We installed the voltage sag compensator to the power supply for the shut-off rods (SORs) and control absorber rods (CARs) to prevent an unwanted trip. We undertook voltage sag assessment of the AC coil contactor which is a component of the power supply unit for the SORs. The compensation time is determined to be less than 1 sec in consideration of the reactor safety. This paper is concerned with the impact of a momentary interruption on the reactor and the effect of a voltage sag compensator.