Abstract

Open phase events, when undetected in a timely manner, can be detrimental to motors; and therefore, could result in loss of safety functions that are necessary for ensuring safe plant shutdown. Sargent & Lundy specializes in identifying, designing, and installing comprehensive solutions to address the issue of open phase conditions (OPC).

An area of advancement detailed in the following white paper is the detection of the OPC via implementation of various relaying schemes. The relays provide the mechanisms for actuating circuit breakers and isolate auxiliary loads in the event of an open phase protection trip. Load isolation generally consists of transferring the loads from the faulted source to a healthy source.

Load transfer can be accomplished through different transfer schemes; however, this paper focusses on the fast bus transfer method, as it is the most common transfer type at nuclear power plants. Using the Electromagnetic Transient Program – Restructured Version (EMTP-RV), this paper addresses a fast bus transfer scheme from a primary source of power to an alternate source, following an open phase protection trip, and compares to a non-open phase transfer.

Authors: Fatou Thiam, Michael Urbina, Jan Wisniewski

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