Voltage at load of distribution network

In summary, the voltage at points B and C should be 3.2*10^6/3*11*10^3=167.96 and 134.37-j100.85=134.37-j100.85 or 134.37-j100.85=134.37-j100.85=0.
  • #1
ClimberTom
2
0
Please bare with me, this is my first post here (although I've read a lot on here over the past few months)
Hopefully I've used the correct formatting etc.
I've got to a sticking point on the final point of the question below (2iii) I'm pretty happy with my answers to 2i and 2ii so I've not shown them so as to not confuse the situation, the only parts carried over are the total current drawn (It) and the total load (S).
In case the attachment isn't very clear, the load at 'C' is 0.6pf lead.

I have omitted the volt drop part of the calculations as I cannot get the calculated current at the end to be close to the estimated current at the beginning. I am happy with the volt drop part once the currents make sense.

Details below and attached.

1. Homework Statement

Determine the load voltage levels for the following distribution feeder systems.
(see image attached for the sketches)

Homework Equations


## B=3.2 ∠-36.9° \text {MVA}\ ##
## B= 2.56-j1.92 \text {MVA}\ ##
## C=1.8 ∠53.1° \text {MVA}\ ##
## C=1.08+j1.44 \text {MVA}\ ##
## S=3.67 ∠-7.5° \text {MVA}\ ##
## S=3.64-j0.48 \text {MVA}\ ##
##I_t≈192.63∠-7.5° \text {A}\ ##
##I_t ≈ 192.78-j2.23 \text {A}\ ##

(I_t and S are both calculated from question 2i as shown on the attached sheet.

The Attempt at a Solution



Estimating Current drawn at points B and C:

##I_{BE} = {\frac{3.2*10^6}{\sqrt{3}*11*10^3}} ##
##I_{BE}=167.96∠-36.9° \text {A}\ ##
##I_{BE}=134.37-j100.85 \text {A}\ ##

##I_{CE} = {\frac{1.8*10^6}{\sqrt{3}*11*10^3}} ##
##I_{CE}=94.48∠53.1° \text {A}\ ##
##I_{CE}=56.69+j75.55 \text {A}\ ##

Assuming the lowest voltage will be at load 'B' (drawing the most current) therefore, 'B' should be fed from both sides as current will flow from highest potential to lowest potential.

Volt drop around ACBA = 0
Therefore:

## 0=-2.7I_{z2}-5.4(I_{z2}-94.48∠53.1°)+4.6(192.63∠-7.5°-I_{z2}) ##
##=-2.7I_{z2}-5.4I_{z2}+306.126-j407.97+886.788-j10.258-4.6I_{z2}##
##=-12.7I_{z2}+1192.914-j418.228##
##12.7I_{z2}=1192.914-j418.228##
##=1264.10∠-19.3°##
##I_{z2}=99.54∠-19.3° \text {A}\ ##
##I_{z2}=93.95-j32.9 \text {A}\ ##

##I_{z1}= I_t-I_{z2}##
##=192.78-j2.23-93.95-j32.9##
##I_{z1}=98.83-j35.13 \text {A}\ ##
##I_{z1}=104.89∠-19.6° \text {A}\ ##

##I_{z3}=I_{z2}-I_ce##
##=93.95-j32.9-56.69+j75.55##
##I_{z3}=37.26+j42.65 \text {A}\ ##
##I_{z3}=56.63∠48.9° \text {A}\ ##

##I_b=I_{z1}+I_{z3}##
##=98.83-j35.13+37.26+j42.65##
##I_b=136.09+j7.52\text {A}\ ####
##I_b=136.3∠3.16° \text {A}\ ##I feel sure that I have overlooked something simple here. I'm pretty confident that I'm correct in assuming B to be the lower voltage. That said, I have tried working the volt drop around the loop as ABCA = 0 and still not got the correct answer.

Can anyone offer any pointers on where I am going wrong?

Many thanks
 

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  • #2
Ignore the above, After lots of tea and scrap paper, I realized that my equation for the voltage around the loop was wrong and also due to some rounding and conversion errors, other values were also incorrect.

I've now sussed it out and submitted it so just waiting for it to be marked.
 

1. What is the voltage at load of a distribution network?

The voltage at load of a distribution network refers to the amount of electrical potential difference present at the point where power is being delivered to the end user. It is usually measured in volts (V) and can vary depending on the location, time of day, and demand for electricity.

2. How is the voltage at load of a distribution network determined?

The voltage at load of a distribution network is determined by the amount of power being generated, the distance of the load from the power source, and the characteristics of the distribution system. It is also regulated by power companies to ensure that it remains within a safe and acceptable range for electrical devices to operate.

3. What is the ideal voltage at load for a distribution network?

The ideal voltage at load for a distribution network is typically between 110-120 V for residential and small commercial use, and 220-240 V for larger commercial and industrial use. This range ensures that electrical devices can operate safely and efficiently without the risk of damage.

4. What happens if the voltage at load of a distribution network is too high?

If the voltage at load of a distribution network is too high, it can cause damage to electrical devices and appliances. This can result in shorter lifespans, malfunctions, and even safety hazards. Power companies continuously monitor and regulate the voltage at load to ensure it remains within a safe range.

5. How does voltage drop affect the voltage at load of a distribution network?

Voltage drop refers to the decrease in voltage as electricity travels through a distribution network. This can happen due to the resistance of the wires and other components in the system. If voltage drop is significant, it can result in a lower voltage at load, which can cause electrical devices to not function properly. Power companies use various methods to minimize voltage drop and maintain a stable voltage at load.

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