The eduPerson schema added the eduPersonOrcid attribute in its February 2016 update.
As per the eduPerson specification:
RFC4512 definition
( 1.3.6.1.4.1.5923.1.1.1.16
NAME 'eduPersonOrcid'
DESC 'ORCID researcher identifiers belonging to the principal'
EQUALITY caseIgnoreMatch
SYNTAX '1.3.6.1.4.1.1466.115.121.1.15' )
Note that the format for this field is the ORCID-preferred URI representation of the iD, i.e. https://orcid.org/0000-0001-5727-2427.
Further information about the format of the ORCID iD can be found in Structure of the ORCID identifier.