BIS <br/><br/>
IS: 3231 - Part 3 - Section - 4 - 1987; Specification forElectrical Relays for Power systems protection Part 3; Requirements for Particular Group of Relays Section 4; Directional Relays and power relays 

 - New Delhi  BIS  1987 
 - 19p 
<br/><br/><label>Universal Decimal Class. No.: </label> /