| Topic: |
Science > Physics |
| User: |
"" |
| Date: |
22 May 2007 03:04:22 PM |
| Object: |
Help a liberal arts graduate out |
Hi everyone, I'm on vacation with my family, I just graduated from
college. Unfortunately my degree is in psychology, and I haven't had a
physics class since high school. Here's a problem my sister is working
on for her honors physics class that she asked me to look at:
Power is generated at 24kV at a generating plant located 118 km from a
town that requires 50 MW of power at 12 kV. Two transmission lines
from the plant to the town each have a resistance of 0.10 Ohm/km. What
should the output voltage of the transformer at the generating plant
be for an overall transmission efficiency of 98.5%, assuming a perfect
transformer?
I can get the answer, and she doesn't care whether she gets it or not.
I just want to see how it is done now. I'd really appreciate it, it's
driving me nuts.
.
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| User: "Greg Neill" |
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| Title: Re: Help a liberal arts graduate out |
22 May 2007 03:36:53 PM |
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<powelljm2@gmail.com> wrote in message
news:1179864262.857816.190100@k79g2000hse.googlegroups.com...
Power is generated at 24kV at a generating plant located 118 km from a
town that requires 50 MW of power at 12 kV. Two transmission lines
from the plant to the town each have a resistance of 0.10 Ohm/km. What
should the output voltage of the transformer at the generating plant
be for an overall transmission efficiency of 98.5%, assuming a perfect
transformer?
It's not clear what the actual circuit is supposed to look like.
Are we to assume that the transmission lines form independent
feeds and that the return circuits are via ground? If so, what
is the ground resistance for the return path? Or, are the two
transmission lines used to form the complete circuit? Are we
allowed to have transformers at each end of the transmission
lines?
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| User: "Sam Wormley" |
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| Title: Re: Help a liberal arts graduate out |
22 May 2007 04:48:26 PM |
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wrote:
Hi everyone, I'm on vacation with my family, I just graduated from
college. Unfortunately my degree is in psychology, and I haven't had a
physics class since high school. Here's a problem my sister is working
on for her honors physics class that she asked me to look at:
Power is generated at 24kV at a generating plant located 118 km from a
town that requires 50 MW of power at 12 kV. Two transmission lines
from the plant to the town each have a resistance of 0.10 Ohm/km. What
should the output voltage of the transformer at the generating plant
be for an overall transmission efficiency of 98.5%, assuming a perfect
transformer?
I can get the answer, and she doesn't care whether she gets it or not.
I just want to see how it is done now. I'd really appreciate it, it's
driving me nuts.
Ohm's Law to figure the loss.
.
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| User: "H. Wabnig .... .-- .- -... -. .. --. @ .- --- -. DOT .- -" |
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| Title: Re: Help a liberal arts graduate out |
22 May 2007 03:13:29 PM |
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On 22 May 2007 13:04:22 -0700, "powelljm2@gmail.com"
<powelljm2@gmail.com> wrote:
Hi everyone, I'm on vacation with my family, I just graduated from
college. Unfortunately my degree is in psychology, and I haven't had a
physics class since high school. Here's a problem my sister is working
on for her honors physics class that she asked me to look at:
Power is generated at 24kV at a generating plant located 118 km from a
town that requires 50 MW of power at 12 kV. Two transmission lines
from the plant to the town each have a resistance of 0.10 Ohm/km. What
should the output voltage of the transformer at the generating plant
be for an overall transmission efficiency of 98.5%, assuming a perfect
transformer?
I can get the answer, and she doesn't care whether she gets it or not.
I just want to see how it is done now. I'd really appreciate it, it's
driving me nuts.
Your sister is driving you nuts?
w.
.
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| User: "" |
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| Title: Re: Help a liberal arts graduate out |
23 May 2007 09:08:47 AM |
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On May 22, 1:04 pm, "powell...@gmail.com" <powell...@gmail.com> wrote:
Hi everyone, I'm on vacation with my family, I just graduated from
college. Unfortunately my degree is in psychology, and I haven't had a
physics class since high school. Here's a problem my sister is working
on for her honors physics class that she asked me to look at:
Power is generated at 24kV at a generating plant located 118 km from a
town that requires 50 MW of power at 12 kV. Two transmission lines
from the plant to the town each have a resistance of 0.10 Ohm/km. What
should the output voltage of the transformer at the generating plant
be for an overall transmission efficiency of 98.5%, assuming a perfect
transformer?
I can get the answer, and she doesn't care whether she gets it or not.
I just want to see how it is done now. I'd really appreciate it, it's
driving me nuts.
The effective current at the receiver end is 50MW/12kV=4166A
The voltage drop on the line is 4166A*118km*0.1 Ohm/km=50KV*.
983=49.15kV
Therefore, the voltage at transformer secondary is 12KV+49.15=61.15kV
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| User: "Greg Neill" |
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| Title: Re: Help a liberal arts graduate out |
23 May 2007 10:49:12 AM |
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<karandash2000@yahoo.com> wrote in message
news:1179929326.287381.78580@q75g2000hsh.googlegroups.com...
On May 22, 1:04 pm, "powell...@gmail.com" <powell...@gmail.com> wrote:
Hi everyone, I'm on vacation with my family, I just graduated from
college. Unfortunately my degree is in psychology, and I haven't had a
physics class since high school. Here's a problem my sister is working
on for her honors physics class that she asked me to look at:
Power is generated at 24kV at a generating plant located 118 km from a
town that requires 50 MW of power at 12 kV. Two transmission lines
from the plant to the town each have a resistance of 0.10 Ohm/km. What
should the output voltage of the transformer at the generating plant
be for an overall transmission efficiency of 98.5%, assuming a perfect
transformer?
I can get the answer, and she doesn't care whether she gets it or not.
I just want to see how it is done now. I'd really appreciate it, it's
driving me nuts.
The effective current at the receiver end is 50MW/12kV=4166A
The voltage drop on the line is 4166A*118km*0.1 Ohm/km=50KV*.
983=49.15kV
Therefore, the voltage at transformer secondary is 12KV+49.15=61.15kV
There are two transmission lines.
Calculate the efficiency for your scheme.
.
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