This document is attached in pdf format and is intended to illustrate the possibilities of integration between ABB medium and low voltage protection trip units, paying particular attention to the protection and control unit type REF542 (for MV) and the protection trip unit PR123 (for LV).
A White Paper is a document which describes, in a clear and detailed way, a product or a particular function of a product, with reference to its application and highlighting the strength and the advantages deriving form its use.
This White Paper describes the possibilities of integration between ABB medium and low voltage protection trip units, paying particular attention to the protection and control unit type REF542 (for MV) and the protection trip unit PR123 (for LV).
Two different application fields are taken into consideration:
- coordination with the medium voltage for an earth fault upstream the
relevant protection on the low voltage side - selectivity between two MV and LV protection unit
A fault between the windings of a transformer secondary or in the section immediately on the supply side of the LV circuit-breaker (also called “restricted earth fault”) cannot be easily detected by the protections on the primary of the MV/LV transformer. As a consequence, it could be necessary to provide for a dedicated protection against this kind of fault, so that fire hazard is limited as much as possible and people’s safety is guaranteed.
Achieving correct MV/LV selectivity may sometimes be complicated. The difficulties can be solved by means of suitable coordination strategies.
Be sure to read the rest of ABB's White Paper by clicking on the pdf attachment below.