power systems loss

PROBLEM:   A 230kV transmission line has impedance of 50 angle 78 ohms and a capacitive reactance of 1200ohms. It transmits the power of a base load plant. On a certain dry season the sending end power is 100MW at 235kV and 95% power factor continuously for a period of one month. If cost of generation is 1.3dollars per kW-hr, what is the cost of the line losses for the one month period? SOLUTION: In analyzing this problem, we assume a nominal pi equivalent circuit. Also, assume the sending voltage as the reference and with a lagging power factor.  Nominal pi equivalent circuit

PROBLEM: A 15MW, 132kV, 80% power factor three phase load is to be served by a transmission line having conductors whose resistance is 0.5ohm/km. if the losses on the line shall not exceed 4.5%, how long must this line be? SOLUTION: To better understand the problem,let us first draw the figure that the problem would like to emphasize.

PROBLEM:   A 10-km, three phase transmission line delivers power to a load rated 2000kW, 6.9kV and at 80% lagging power factor. The resistance and reactance of each line are 0.2 and 1.2 ohms per kilometer, respectively. What percentage of the power generated is lost in the transmission line? SOLUTION: Similar to the previous problem , we should first draw the figure for us to understand clearly what is required for us to solve.

PROBLEM:  A 3-kilometer, 336ACSR, 3-wire short transmission line has an impedance of 2 + j5 ohms per wire. At the receiving end, a balanced 3-phase load and capacitor bank draws 3000kVA, 0.71 power factor lagging and 600kVAR respectively at 8000 volts per phase to neutral. Determine the power loss of the transmission line. SOLUTION: The first thing that we should do in analyzing any problem is to illustrate our interpretation of the problem into a figure which will make us better understand what is needed.