DIRECTIONAL OVERCURRENT RELAY FUNTION How to calculate the Operating region for Directional over current relay ?

Relay characterstic Angle (RCA)

The Relay characterstic value is used to define the region to operate the relay in thespecified direction.

Example :-

Let RCA = 45 In normal condition angles between Current & Voltages

IR IY IB0 120 240 VR VY VB0 120 240 VRY VYB VBR120 360 240

If any fualt occure in any phase the voltage will be drop and heavy current will flow.

So to see the direction of the current flow relay will take other helth phase voltages.

Operating region = ( Phase displaced + RCA) to ( Phase displaced + RCA +180 )

Let's take R phase grounded and relay will take VYB voltage value is referanceVYB displaced 0 or 360 from IROperating region = ( 0 + 45 to 45 + 180 )= 45 to 225

Let's take Y phase grounded and relay will take VBR voltage value is referanceVYB displaced 240 from IR

= (240 + 45 ) = 285 and= 285 + 180 = 465= 465 - 360 = 105 Operating regien = 105 to 285

Let's take B phase grounded and relay will take VBR voltage value is referanceVRY displaced 120 from IB

= (120 + 45 ) = 165 and= 165 + 180 = 345 Operating regien = 165 to 345