EGE ÜNİVERSİTESİ MÜHENDİSLİK FAKÜLTESİ

ELEKTRİK-ELEKTRONİK MÜHENDİSLİĞİ

GÜÇ SİSTEMLERİ ANALİZİ-1 DERSİ

UYGULAMALARI

Hazırlayan: Arş. Gör. Faruk UGRANLI

EXPERIMENT 5

Per Unit and Transmission Line Parameters

1. Objective

The objective of this experiment is to show the per unit representation of the circuit quantities

such as power, voltage, current and impedance. Change of the base also will be demonstrated

with an example. After, the transmission line parameters such as resistance, inductance and

capacitance will be calculated for single and three phase transmission lines, bundled

conductors, and double circuit lines.

2. Pre-Experiment

What is the advantages of the per unit system?

What is the skin effect?

How can the inductance and capacitance of transmission lines be calculated?

What is the concept of GMD and GMR?

What is the advantages of the bundled conductors?

3. Procedure

A) The per unit value of complex power and voltage,

Write the base impedance according to the circuit law.

The relation between the old and the new per-unit values is

Find the pu values of power system in Figure 1 for 100 MVA base and choose

20-kV as the voltage base for generator.

Figure 1. 2 bus power system

Draw the impedance diagram.

B) The inductance of the single phase lines as shown in Figure 2.

where is the geometric mean radius (GMR) which is

.

Figure 2. Single-phase two-wire line

The flux linkages of each conductor can be calculated as follows

For symmetrical spacing of three-phase transmission lines as shown in Figure

3, the inductance per phase per kilometer is the same with the above equation.

Figure 3. Three-phase line with symmetrical spacing

For asymmetrical spacing of three-phase transmission lines as shown in Figure

4,

where

Figure 4. Three-phase line with asymmetrical spacing

If the composite conductors (stranded conductors) are used as shown in Figure

5, the GMD and GMRX can be calculated as follow

where

Figure 5. Single phase line with two composite conductor

Evaluate the value of GMD and GMR for x and y conductors.

Find the GMD, GMRX, GMRY and inductance of the complete line in

milihenry per kilometer of single phase circuit shown in Figure 6 by writing a

matlab code. X conductor has three solid 0.5 cm radius wires. The return

circuit is composed of two solid 2.5-cm radius wires.

Figure 6. Conductor layout

C) For bundled conductors as shown in Figure 7, The GMR of the equivalent single

conductors as follows

Figure 7. Examples of Bundled arrangements

A three phase transposed line as shown in Figure 8 has one conductor with 8 m

spacing. The GMR of each conductor is 1.515 cm.

Figure 8. Conductor layout for one conductor case

Determine the inductance of system by writing a matlab code

If the line is to be replaced by a two conductor bundle with 8 m spacing as

shown in Figure 9, determine the GMR of each new conductor in bundle. The

spacing between conductors in the bundle is 40 cm and line inductance should

be 77 percent of not bundle case.

Figure 9. The layout of conductors for bundled case.

D) The capacitance of the single phase line

where r is the actual radius of the conductors.

The capacitance of the three phase lines

If the bundle conductor is used, the r will be changed as follows

E) A 500-kV three-phase transposed line as shown in Figure 10 is composed of one

conductor. The conductors have a diameter of 1.345 in and a GMR of 0.5328 in. Find

the inductance and capacitance by executing the chp4ex2 in Matlab.

Figure 10. Conductor layout

The line is replaced by two bundled conductors as shown in Figure 11. Find

the new inductance and capacitance by executing chp4ex3 and compare the

two results.

Figure 11. Conductor layout

F) To compute of transmission line parameters, execute acsr and gmd2lc function and

solve the following problems.

A single-circuit three-phase transmission transposed line is composed of four

ACSR conductor per phase with horizantal configuration as shown in Figure

12. The conductor code is ‘pheasant’. Determine the inductance and

capacitance per phase per kilometer.

Figure 12. The conductors layout

A double circuit three-phase transposed line is composed of two ACSR kiwi

conductor per phase with vertical configuration as shown in Figure 13. The

bundle spacing is 45 cm. Find the inductance and capacitance per phase per

kilometer of the line.

If the circuit arragement is a1b1c1, a2b2c2, find the values again and compare the

results.

Figure 13. Conductor layouts