power systems loss

POWER AND DISTRIBUTION TRANSFORMER TERMS DEFINITION 1 accessories: Devices that perform a secondary or minor duty as an adjunct or refinement to the primary or major duty of a unit of equipment. alternating current: A periodic current the average value of which over a period is zero. ambient temperature: The temperature of the medium such as air, water, or earth into which the heat of the equipment is dissipated. ampacity: Current-carrying capacity expressed in amperes, of a wire or cable under stated thermal conditions. autotransformer: A transformer in which at least two windings have a common section.

BASIC TRANSFORMER PRINCIPLES Transformer has been one of the most significant inventions of human kind in relation to electricity. Its construction became a breakthrough to all other discoveries that has elevated man kind's way of living. At present, it is almost unimaginable to think if transformers have not even been around. Two key principles has been the main reason for its existence; that a magnetic field can be produced from electric current termed as electromagnetism and the other one is that voltage can be induced at the ends of a coil whenver a changing magnetic field within a coil of wire also termed as electromagnetic induction. Today, various forms of transformers exist at our disposal, from the smallest size to the gigantic forms also known as power transformers all for the purpose of serving man's needs. Before we discuss the losses that exist in the transformers found in our power system, let us first have the time to review its basic principles of operation. W

HISTORY-EARLY TRANSFORMERS 1895-1920  A tour of the three generations of transformers that helped make possible early power transmission. These step up transformers sent power 22 miles to Sacramento with a 10% loss. The first transformers at Folsom(1895) were air cooled and made by William Stanley - pioneer of the transformer. The second generation was made by Westinghouse, and the third by Alice Calmers (1920).

Beside Transmission Lines , the distribution of electrical power from one place to another would be impossible without the use of transformers. It would be very impractical if not impossible to transmit a usable voltage level say 240V over a long distance transmission. With the help of transformers, power transmission in the modern era has been very successful. Various forms of transformers exist today each with its own purpose and function. The development of this human invention, the transformer, has come a long way from the day of its inception. One may see the evolution that occurred which makes it a very fascinating device that has help human kind since time immemorial.

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.