Hello Himanshu

EWS is a  nationally certified document, acclaimed to be used in reference to the  recruitment in government posts and admission in colleges; with 10% reservation for people not belonging  to other categories like SC,ST,OBC etc.

Thus, 10% seats are reserved for economically weaker section irrespective of the state where one belongs to in every centrally affiliated service and institution.

Delhi Police recruits through SSC examination, which is coordinated centrally, hence your EWS certificate will be valid for Delhi police vacancy.