How much is the current flowing in the transmission line?

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Homework Help Overview

The discussion revolves around a problem involving electrical transmission lines, specifically focusing on the current flowing in a transmission line after a voltage step-up from a power plant to a substation. The scenario includes parameters such as voltage, current, and resistance of the transmission line.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relationship between primary and secondary currents and voltages using transformer equations. There is a question regarding the relevance of Ohm's law in this context, and some participants express uncertainty about the layout of the system, particularly the placement of the resistance in relation to the transformer and substation.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem setup. Some guidance has been offered regarding the relationship between the parameters, but there is no explicit consensus on the relevance of certain information provided in the problem.

Contextual Notes

There is a noted ambiguity regarding the placement of the 75 ohm resistance and its impact on the calculations, which participants are attempting to clarify.

golriz
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Asmall power plant produces a voltage of 6.0kV and a current of 150A. The voltage is stepped up to 240kV by a transformer before being sent to a substation. The resistance of the transmission line between the power plant and the substation is 75 ohm. How much is the current flowing in the transmission line?


I(p)/I(s)= V(s)/V(p) s= stationary P= primary
V= IR


I(p) = 150 , V(p) = 6.0kV , V(s) = 240kV , I(s) = ?
 
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golriz said:
I(p)/I(s)= V(s)/V(p) s= stationary P= primary

I(p) = 150 , V(p) = 6.0kV , V(s) = 240kV , I(s) = ?

Plug in the numbers and solve. V = IR is not needed here.
 
oh, why?
I don't know why V = IR is not needed here?
 
It occurred to me (after discussing this with somebody else) that I may not understand the layout here.

Perhaps you have a figure you can look at to answer this question: is the 75 ohm line in between the power plant and the transformer, or is it between the transformer and the substation?
 
I think it is between the transformer and the substation.
 
In that case, the 75Ω will affect the voltage at the substation, but not at the transformer. It is irrelevant here.

I'm not sure why they included that information, maybe just to throw you off?
 
Last edited:

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