Large mill power outages caused by potential transformer ferroresonance

Abstract

Investigative procedures relating to a subtle 30 Hz ferroresonant instability of high-voltage potential transformers, which has caused several costly power outages to a large paper mill are reported. Included are unusual field oscillograms of this instability. Corrective measures were developed which have been implemented. An alternate recommended approach is to be incorporated in a similar high-voltage supply to a new mill to eliminate this instability as a possible jeopardy to selective ground-relay protection.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>