Question

The current from neutral to ground connection is 12 A. Calculate the zero phase sequence component current in each phase.
1. 2 A
2. 4 A
3. 6 A
4. None of these

Answer 1

Correct Answer - Option 2 : 4 A

Zero sequence component:

• These component vectors consist of three phases equal in magnitude and with zero phase displacement from each other.
• For the flow of zero sequence current under fault conditions, the ground path is mandatory.
• In-ground overcurrent relay, as the ground is present, zero sequence current can flow easily & the fault can be sensed with the relay.

IRo = IYo = IBo

NOTE: Zero sequence current will flow in the neutral grounded system.

IN = 3IRo

In neutral, zero sequence current flows three times. 

Calculations:

I_N = 12 A

\(I_{R0}=\dfrac {I_N}{3}=\dfrac{12}{3} = 4 A\)

Zero phase sequence component current in each phase is 4 A