ABSTRACT
A zone of protection is the area where a protective relaying scheme is expected to detect faults and initiate isolation of failed components in order to minimize damage, to prevent consequential damage, and to prevent system collapse. Zones of protection are discussed in the first part of this chapter. Usually protective relays that detect faults within a zone of protection are designated in a manner that uniquely ties the protective function to the component, as the same protective function may be required for multiple, similar components. For example, a transformer differential relay that protects Transformer 1 could be referred to as Transformer 1 Differential or Tr. 1 Diff. or T1-87.
