Study of Forsmark-Type Voltage Transient on Power UPS in Nuclear Power Plants

Abstract

The uninterrupted power supply (UPS) system used in Indian Nuclear Power Plants (NPP) provides 415V three-phase four-wire supply to most critical loads. These loads are required for safe reactor operation, reactor shutdown as well as during accident conditions. Hence these UPS systems have very stringent qualification requirements. The newly proposed transient test as a part of qualification given in IEEE-650 is studied in this paper. This is based on the transient incident reported at the NPP of Forsmark, Sweden. The analysis presented here brings out the possible difficulties in carrying out this transient test. It also suggests possible design modifications that need to be addressed during the design of a power UPS.