A 3-phase transformer rated for 33 kV/11 kV is connected

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A 3-phase transformer rated for 33 kV/11 kV is connected in delta/star as shown in figure. The current transformers (CTs) on low and high voltage sides have a ratio of 500 / 5. Find the currents i₁ and i₂ , if the fault current is 300A as shown in figure.

1. i₁ = 1 / √3 A , i₂ = 0A
2. i₁ = 0 A , i₂ = 0 A
3. i₁ = 0 A , i₁ = 1 / √3 A
4. i₁ = 1 / √3 A , i₂ = 1 / √3 A

Correct Option: A

i₂ = 0 (∵ entire current flows through fault)
Now, Primary kVA = Secondary kVA

∴ √3 × I_L = √3 × 11000 ×		300 ×	5
			500

I _L = 1A
Now, I_L = √3 I_Ph

∴ I_Ph =	I_L	=	1	A
	√3		√3