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Question
For a power system:
Line to line fault current=−j2.5 p.u.
3−ϕ fault current =−j5 p.u.
The positive and negative sequence reactances are
For a power system:
Line to line fault current=−j2.5 p.u.
3−ϕ fault current =−j5 p.u.
The positive and negative sequence reactances are
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Solution
The correct option is B X1=0.2 p.u., X2=0.49 p.u.
3−ϕ fault current:
Let system is under no load condition before fault,
∴ E=1∠0∘p.u.
3−ϕ fault current,If=EX1
⇒ X1=1−j5=j0.2 p.u.
Line−line fault current:If=√3EX1+X2
⇒X1+X2=√3−j2.5
⇒j0.2+X2=j0.69 p.u
⇒ X2=j0.49 p.u
3−ϕ fault current:
Let system is under no load condition before fault,
∴ E=1∠0∘p.u.
3−ϕ fault current,If=EX1
⇒ X1=1−j5=j0.2 p.u.
Line−line fault current:If=√3EX1+X2
⇒X1+X2=√3−j2.5
⇒j0.2+X2=j0.69 p.u
⇒ X2=j0.49 p.u
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