Transformer Protective Zones
Traditionally, the protection of medium-voltage power transformers at industrial facilities has been relegated to the application of transformer phase differential and backup overcurrent relays to provide short-circuit protection.
With the advent of modern multifunction transformer relay packages, phase differential and overcurrent are only two of the many protection functions that are incorporated into these relays.
Figure 1 illustrates the various protection zones that can be part of a digital
transformer protection relay.