题目内容

For a Y connection, the line current IL is( )

A. Equal to phase current IL=Ip
B. Equal to square root 3 times phase current IL=1.73Ip
C. Equal to phase current divided by square root three IL=Ip/1.73

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When ac current flows in a conductor, the current distribution is not uniform over the conductor cross sectional area and the current density is greatest at the surface of the conductor. This causes the ac resistance to be higher than the dc resistance. This behavior is known as ( )。

A. Corona discharge
B. Skin effect
C. Ferranti effect
D. Phase angle

( ) is an electric discharge brought on by the ionization of a fluid/air surrounding a conductor。

A. Corona discharge
B. Skin effect
C. Ferranti effect
D. Phase angle

A Y connected balanced impedance has value ZY=5+j30Ω. Convert this to an equivalent Δ connected impedance and the impedance ZΔ is( )。

A. 5+j30Ω.
B. 30+j5Ω.
C. 15+j90Ω

A transformer has reactance 0.25 pu given on a 230 kV, 75 MVA base. The reactance on a 345 kV, 100 MVA base is ( )。

A. 0.15 pu.
B. 0.20 pu.
C. 0.12 pu.

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