- #1

Joe85

- 29

- 3

- Homework Statement
- Figure shows a 50 Hz, high-voltage, transmission line. The relationships between the sending and receiving end voltages and currents are given by the complex ABCD equations:

- Relevant Equations
- .

V

I

Given the parameter values in TABLE C and an open-circuit received voltage measured as 88.9 kV, calculate the values of V

V

Table C Values:

A

A

B

B

C

C

D

D

Transmission Line is Open Circuit, thus:

I

I seem to be coming up with the correct answer but I'm getting a negative value for

I

V

∴ V

∴ V

V

And:

I

∴ I

∴ I

I

= J9273312.066 + J

= (-1)*377627.8609 + J9273312.066

= -377627.8609 Watts

I've seen that other answers using a similar method are positive, does this mean i disregard it being a negative value as it's a 'Total Power absorbed' so must a positive quantity?

Any help much appreciated.

Joe.

_{S}=V_{R}(A_{1}+jA_{2})+I_{R}(B_{1}+jB_{2})I

_{S}=V_{R}(C_{1}+jC_{2})+I_{R}(D_{1}+jD_{2})Given the parameter values in TABLE C and an open-circuit received voltage measured as 88.9 kV, calculate the values of V

_{S}and I_{S}and hence the power (P_{SO}) absorbed from the supply by the transmission line on open circuit.V

_{R}= 88.9×10^{3}Table C Values:

A

_{1}= 0.8698A

_{2}= 0.03542B

_{1}= 47.94ΩB

_{2}= 180.8ΩC

_{1}= 0 SC

_{2}= 0.001349 SD

_{1}= 0.8698D

_{2}= 0.03542Transmission Line is Open Circuit, thus:

I

_{R}= 0Hi all,I seem to be coming up with the correct answer but I'm getting a negative value for

**P**. Just wanted to be sure I'm not making an error with my numbers._{SO}I

_{R}= 0V

_{S}=V_{R}(A_{1}+jA_{2})+I_{R}(B_{1}+jB_{2})∴ V

_{S}=V_{R}(A_{1}+jA_{2})∴ V

_{S}= 88.9×10^{3}(0.8698 +J 0.03542)V

_{S}= 77325.22 + J3148.838 VoltsAnd:

I

_{S}=V_{R}(C_{1}+jC_{2})+I_{R}(D_{1}+jD_{2})∴ I

_{S}=V_{R}(C_{1}+jC_{2})∴ I

_{S}= 88.9×10^{3}(0 + J0.001349)I

_{S}= J119.9261 Amps**P**= Re{V_{SO}_{S}I_{S}*}**∴ P**= Re{(77325.22 + J3148.838)(J119.9261)_{SO}= J9273312.066 + J

^{2}377627.8609= (-1)*377627.8609 + J9273312.066

= -377627.8609 Watts

I've seen that other answers using a similar method are positive, does this mean i disregard it being a negative value as it's a 'Total Power absorbed' so must a positive quantity?

Any help much appreciated.

Joe.