Transformer Phasing Standards
There are two major phasing standards used worldwide for transformers.
The ANSI/IEEE Standard C57.12.00–2000 was developed by North American transformer manufacturers and is used in the United States, Canada, and many other countries.
The IEC phasing standard IEC60076-1 was developed by European transformer manufacturers and is used in Europe and countries worldwide whose electrical systems were influenced by European manufacturers. Transformer protective relays that are sold worldwide must be able to handle both IEEE/ANSI and IEC phasing standards. Being able to handle both of these phasing standards has added to the complexity of digital transformer relays. Properly communicating the ase shift introduced by delta-wye transformers to a digital relay is the biggest source of setting errors in digital transformer relays.
The level of complexity required to communicate transformer phase shift to a digital relay is one of the design features that differentiates one relay manufacturer’s product from another.