IS: 3231 (Part 2/Sec. 2) - 1987 (Reaffirmed 1992); Specification for electrical relays for power system protection Part 2 requirements for principal families Section 2 general requirements for measuring relays 

 - New Delhi  BIS  1987 
 - 35p 
<br/><br/><label>Universal Decimal Class. No.: </label> /