Transformers are high capital cost assets in electrical power systems. Elimination of all electrical and mechanical stresses, although desirable to preserve transformer life, is impractical. Adaptive techniques to measure and alarm (or trip) in such instances and advise on cumulative service duty can help to schedule preventive maintenance – before a costly failure occurs.

Internal faults are a risk for all transformers, with short-circuits dissipating the highest localised energy. Unless cleared quickly, the possibility to rewind windings reduces and core damage may become irreparable.

The MiCOM Alstom P642, P643 and P645 address all these issues - preserving service life and offering fast protection for transformer faults. A transient bias technique has been included, enhancing relay stability and CT requirements.

Hosted on an advanced IED platform, the P64x incorporate differential, REF, thermal, and overfluxing protection, plus backup protection for uncleared external faults. Model variants cover two and three-winding transformers (including auto-transformers), with up to five sets of 3-phase CT inputs.

Basic description:

• Comprehensive protection for 2 or 3 winding transformers, with dual breaker feeding on up to two sides 
• High and low impedance restricted earth fault (REF) boosts trip sensitivity 
• Fast reset (less than 1 cycle) circuit breaker failure elements 
• Integral asset management capability:  transformer thermal overload (IEEE Standard C57.91), loss of life (LOL) and through fault monitoring