Note : For the utilisation of Table 2 : the material used for all the designs is the aluminum (All
conduit)
Exercise 1 ) Design of the main for an uniform distribution
A 13kv feeder has a length`` l=1km``. It is feeding 40 3-phases loads as presented in the
schematic bellow. Assume that each load has the same pick power of 125kvar.The power
factor is 0.85.
1) Calculate the sending main current
2) Calculate the effective Z of the main
3) Calculate the voltage drop of the main
Exercise 2) Design of the laterals for uniform distribution
Each lateral of the feeder of the previous example has a length of 2.5km.
1) Calculate the sending current of each lateral
2) Calculate the effective Z of the lateral
3) Calculate the voltage drop of the lateral
4) Calculate the voltage drop of the feeder
1
Exercise 3: Design of non uniform distribution feeder
Consider the feeder in the figure bellow with VL-N=13kV
The variation of the current of the main in function of the distance is given by the equation:
The sending current for main is 150A and its length is 2km. The operating power factor is 0.95.


Calculate the section and the voltage drop of the main
Calculate the copper losses per phase of the main
Exercise 4: Design of random symmetric distribution feeder
Consider the feeder of the figure bellow. Note that all the loads are the same and each load has
pick power of 150kvar. The system is operating at 0.9 PF. The distance between each lateral is
the same
The length of the main is : 1km. The length of the laterals 1, 2,3 and 4 : are 500m, 1km, 1.5km
and 2km receptively.
2
1. Calculate the sending currents in each lateral
2. Design : ( find the section and the voltage drop ) of each lateral. For each lateral take the
same section of the lateral 4.
3. Calculate the sending current of the main
4. Design : ( find the section and the voltage drop ) of the main
5. Calculate the voltage drop of the feeder
Exercise 5 ) Design of a feeder with uniform distribution in the future
The loads of the feeder of exercise 1 will doubled after 10 years. Design the feeder ( main and
lateral) after 7 years if the feeder is suppose to work with a power factor of 0.9.
In the market you have this list of transformers :
Witch transformer do you want to select for your design
Transformer
1
2
3
4
5
Rang
13kv/220v/60Hz
13kv/220v/60Hz
13kv/220v/60Hz
13kv/220v/60Hz
13kv/220v/60Hz
Power kvar
100
150
200
250
300
3