IS: 3231 (Part3/Sec.3) - 1987 (Reaffirmed 1992); Specification for electrical relays for power system protection Part 3 requirement for particular group of relays Section 3 Biased (percentage) differential realys 

 - New Delhi  BIS  1987 
 - 16p 
<br/><br/><label>Universal Decimal Class. No.: </label> /