APR1400 NRC(Nuclear Regulatory Commission) DC(Design Certification) project was undertaken as a part of the UAE Nuclear Business. Nonetheless, The project is a key factor to construct and operate nuclear plant in the USA. If APR1400 acquires DC from the NRC, KHNP will be possible to take firm foothold in the USA, and to increase significantly in the technical competitiveness in overseas export of korea-type nuclear power plant. APR1400's electrical power system is designed as follows. Not only Offsite but also onsite power systems are supplied to provide electrical power to unit auxiliaries that are necessary during normal operation and the RPS(Reactor Protection System) and ESF(Engineered Safety Feature)s that are necessary in abnormal and accident conditions. The offsite power system comprises of transmission lines, transmission line towers, switchyard components and a control system, transmission tie lines, main generator, generator circuit breaker(GCB), main transformer, unit auxiliary transformers(UATs), and standby auxiliary transformers(SATs). Under normal operating conditions, the main generator supplies power to the main transformer and UATs through an isolated phase bus and the GCB. The UATs are linked to the isolated phase bus between the GCB and main transformer. The onsite power system for the unit auxiliaries consists of four emergency diesel generators(EDGs), an alternate alternating current(AAC) gas turbine generator(GTG), and two onsite power distribution systems. The onsite power distribution system is linked to the site-specific switchyard via two separate and independent transmission tie circuits. One circuit is linked to the switchyard through the main transformer and UATs, and the other circuit is linked to the switchyard via the SATs. During normal operation, onsite power is supplied from the main generator through the UATs. During startup and shutdown, the GCB is open, and the onsite power is supplied from the transmission system through the main transformer and UATs.