Tài liệu Power Transmission and Distribution docx

[...]... electrical connections to utility companies’ 1 2 Power Transmission and Distribution transmission and distribution systems is referred to as “cogeneration,” and will be discussed more fully later in this work The invention of the transformer in 1883 in England by John Gibbs and Lucien Gaullard, together with the invention of the alternating current induction motor and the development of polyphase circuitry... technology, revised codes and standards, inflation, new reliability and environmental requirements, etc The final decision must also satisfy the electrical and mechanical design requirements These criteria apply to both the transmission and distribution systems Referring to the diagram in Figure 1-1, although it has been customary to consider generation, transmission and distribution as three interdependent... conductor and its resistance: I current = E voltage from which, E = IR R resistance Energy loss is the product of power and time; power, however, is the product of the voltage imposed on the conductor and the current flowing through it Again, from Ohm’s Law, this can be derived into the 6 Power Transmission and Distribution product of the square of the current flowing through the conductor and its resistance:... current and the rapid expansion of electrical transmission and distribution systems Transmission of electric power dates from 1886 when a line was built at Cerchi, near the city of Turin in Italy, to transmit some 100 kilowatts 30 kilometers, employing transformers, to raise and lower a 100 volt source to 2000 volts and back to 100 volts for utilization In the same year, the first alternating current distribution. .. total of the maximum demands of each of the members of the group, and this ratio is known as the diversity factor, Figure 1-3 For example, a transformer may supply six consumers whose individual maximum demands total 150 kVA, but whose combined maximum demand may be only 75 kVA The diversity 8 Power Transmission and Distribution factor is 150/75 or 2 It should be noted that the demand factor is defined... the current Power factor, then, is the ratio of power (watts or kilowatts) to the product of voltage and current (in volt-amperes or kilovolt-amperes) It is sometimes defined as the ratio of real power to apparent power From Figure 1-5 Power factor = watts = cos θ EI where E = effective voltage, I = effective current, and θ is their angular displacement in phase Figure 1 -5 Power Factor A power factor... of the maximum demands of each of the consumers connected to it, but a “new” maximum demand of the whole; this is because the maximum demands of each of the individual consumers do not occur at the same time Figure 2-1 Typical Method of Connecting Distribution Transformers Between Feeders and Radial Secondary Circuits (Courtesy Westinghouse Electric Co.) 13 14 Power Transmission and Distribution The... together with instantaneous power, and vector representation of these quantities, are shown in Figure 1-5 When loads are designated in kilowatts, it is essential also to know the power factor as the capacities of transformers, 10 Power Transmission and Distribution capacitors, etc., whose ratings are in kilovolt-amperes Also, line losses are proportional to the square of the current, and voltage drop proportional... general type and is used at the same time and at the same capacity, such as may be found in some manufacturing plants, in water or sewer treatment plants, or in street lighting circuits The ratio of maximum power demand to total connected load is called the “demand factor.” The method of determining the demand factor is also applied to the loads of a group of consumers Here, the combined maximum demand of... closest) to the annual cost of 4 Power Transmission and Distribution losses associated with one of the systems under study This relationship is known as Kelvin’s Law Many factors intrude, however, to modify the applicable conditions These factors pertain generally to safety and environmental requirements as well as provision for possible future demands for electric power, creating changes that may . y0 w0 h0" alt="" i Power Transmission and Distribution 2nd Edition This page intentionally left blank iii Power Transmission and Distribution 2nd Edition Anthony. (electronic) 1. Electric power transmission. 2. Electric power distribution. I. Title. TK3001.P29 2005 621.319 dc22 2004056439 Power transmission and distribution,