All About Circuits Forum 3phase double circuit trasmission line
 User Name Remember Me? Password
 Register Blogs FAQ Members List Today's Posts Search Today's Posts Mark Forums Read

 Homework Help Stuck on a textbook question or coursework? Cramming for a test and need help understanding something? Post your questions and attempts here and let others help.

#1
03-30-2012, 06:49 AM
 Jess_88 Senior Member Join Date: Apr 2011 Location: Australia Posts: 174
3phase double circuit trasmission line

Hey guys

I'm trying to work out this question, using an equivalent Pi circuit, but that fact that it is a "double circuit" is confusing me.

Here is the background.
A 3-Phase, 50Hz, 330kV, 360MW at 0.82 PF is supplied by:
-330kV, 50Hz, Length (L) = 160km, 3-Phase double circuit.
Each circuit has per-phase
Resistance (R) = 120x10^-6 per-unit/km
Reactance (X) = 990x10^-6 per-unit/km
Shunt Susceptance to Neutral (jB) = 461.7x10^-3 per-unit/km
Neglecting Shunt Conductance.

All units have been given in Vbase = 330kV, Sb = 100MVA

So what I think so far:
Because its a balanced and double
-both transmission line circuits will have the same voltage and current
-Thus we can calculate perimeters of just one line
But -The receiving current will be multiplied by two

Can I do these things?
Dose this effect the values used for each line impedance and the Shunt Susceptance?

With the Pi network
Z(line) = L x(R + jB)
=160((120x10^-6)+j(990x10^-6))

Do I need to convert this from phase resistance

I understand I may also need to determine the load impedance and add this to the line impedance for the equivalent circuit.?

What do you guys think?

thanks heaps
__________________
Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.
-Archimedes

Last edited by Jess_88; 03-30-2012 at 07:09 AM.
#2
03-30-2012, 11:35 AM
 Jess_88 Senior Member Join Date: Apr 2011 Location: Australia Posts: 174

ok, so I have a little bit more direction i think.
theta = cos^(-1)(PF)
Ir(line-toline) = Pr/[(sqr(3)*Vr(line-to-line)*PF]

Because it is a medium length
A=D=(1 + (YZ)/2)--- p.u
C = Y(1+(YZ)/4) ---S
AD -BC = 1
Vs = AVr + BIr
Is = CVr + DIr

From my calculations, AD - BC = 1 seem to hold true. So i'm pretty sure that part is right.
But when I use
Is = CVr + DIr, I seem to get 85.86<89.702 (kA)
which seems way to big.

Am a suposed to do anything because it is a double connection?
__________________
Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.
-Archimedes
#3
03-31-2012, 10:27 AM
 Jess_88 Senior Member Join Date: Apr 2011 Location: Australia Posts: 174

Can anyone confirm weather the equations I'm using for this circuit are correct?
__________________
Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.
-Archimedes

 Tags 3phase, circuit, double, line, trasmission

 Related Site Pages Section Title Worksheet AC network analysis Worksheet Series-parallel combination AC circuits Worksheet Series and parallel AC circuits Worksheet Phasor mathematics Worksheet Trigonometry for AC circuits Worksheet Impedance Textbook Susceptance and Admittance : Reactance And Impedance -- R, L, And C Textbook Series-parallel R, L, and C : Reactance And Impedance -- R, L, And C Textbook Review of R, X, and Z : Reactance And Impedance -- R, L, And C Textbook AC inductor circuits : Reactance And Impedance -- Inductive

 Similar Threads Thread Thread Starter Forum Replies Last Post MoC General Electronics Chat 4 03-18-2010 12:33 PM reevery The Projects Forum 2 06-23-2009 11:05 AM AWSariti General Electronics Chat 14 02-27-2009 11:44 AM relicmarks General Electronics Chat 5 11-03-2008 12:32 AM shelly50 General Electronics Chat 27 01-23-2006 04:02 AM

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Electronics Forums     General Electronics Chat     The Projects Forum     Homework Help     Electronics Resources Software, Microcomputing, and Communications Forums     Programmer's Corner     Embedded Systems and Microcontrollers     Computing and Networks     Radio and Communications Circuits and Projects     The Completed Projects Collection Abstract Forums     Math     Physics     General Science All About Circuits Commmunity Forums     Off-Topic     The Flea Market     Feedback and Suggestions

All times are GMT. The time now is 09:08 PM.