TÀI LIỆU HAY VỀ HỆ THỐNG ĐIỆN (Electrical Power Systems)

This book will give readers a thorough understanding of the fundamentals of power system analysis and their applications. Both the basic and advanced topics have been thoroughly explained and supported through several solved examples.; Important Features of the Book; Load Flow and Optimal System Operation have been discussed in detail.; Automatic Generation Control (AGC) of Isolated and Interconnected Power Systems have been discussed and explained clearly.; AGC in Restructured Environment of Power System has been Introduced.; Sag and Tension Analysis have been discussed in detail.; Contains over 150 illustrative examples; practice problems and objectivetype questions; that will assist the reader.; With all these features; this is an indispensable text for graduate and postgraduate electrical engineering students. GATE; AMIE and UPSC engineering services along with practicing engineers would also find this book extremely useful.

[...]... utilities insist the industrial consumers to maintain a power factor 0.80 or above The power tariffs are devised to penalize the consumers with low lagging power factor and force them to install power factor correction devices for example shunt capacitors 1.10 VARIOUS CAUSES OF LOW POWER FACTOR 1 Most of the induction motors operate at lagging power factor The power factor of these motor falls with the decrease... is required for transmission line, feeders and cables to deliver the same load but at low power factor 3 Power loss is proportional to the square of the current and hence inversely proportional to the square of the power factor More power losses incur at low power factor and hence poor efficiency 4 Low lagging power factor results in large voltage drop which results in poor voltage regulation Hence,... .(1.21) Loss Factor: It is the ratio of the average power loss to the peak-load power loss during a specified period of time Therefore, the loss factor (LLF) is defined as: LLF = Average power loss Power loss at peak load .(1.22) Equation (1.22) is applicable for the copper losses of the system but not for iron losses 8 Electrical Power Systems Example 1.1: A power station supplies the load as tabulated... 600 Structure of Power Systems and Few Other Aspects 15 1.9 DISADVANTAGES OF LOW POWER FACTOR For a three-phase balanced system, if load is PL, terminal voltage is V and power factor is cos f, then load current is given by IL = PL 3V cos f (1.38) If PL and V are constant, the load current IL is inversely proportional to the power factor, i.e., if cos f is low, IL is large The poor power factor of the... Rating of generators and transformers are inversely proportional to the power factor Thus, generators and transformers are required to deliver same load (real power) at low power factor Hence, system kVA or MVA supply will increase 2 At low power factor, the transmission lines, feeders or cable have to carry more current for the same power to be transmitted Thus, conductor size will increase, if current... give 230 volt single-phase supply to houses and similar loads Figure 1.3 shows a typical distribution system 2 Electrical Power Systems Figure 1.2 shows part of a typical power system Fig 1.1: Schematic diagram of a power supply system Fig 1.2: Part of a power system Structure of Power Systems and Few Other Aspects 3 Fig 1.3: Typical distribution system 1.2 REASONS FOR INTERCONNECTION Generating stations... 465 Index 467 Structure of Power Systems and Few Other Aspects 1 1 Structure of Power Systems and Few Other Aspects 1.1 POWER SYSTEMS Generation, Transmission and Distribution systems are the main components of an electric power system Generating stations and distribution systems are connected through transmission lines Normally, transmission lines implies the bulk transfer of power by high-voltage links... magnetizing current of inductive reactances increase and power factor of the electrical plant as a whole comes down 3 Very low lagging power factor of agriculture motor pump-set 4 Arc lamps, electric discharge lamps and some other electric equipments operate at low power factor 5 Arc and induction furnaces operate on very low lagging power factor The average power factors of some of the electrical equipments... Loads: This type of load is mainly motor pump-sets load for irrigation purposes Load factor for this load is very small, e.g., 0.15–0.20 1.4 POWER FACTOR OF VARIOUS EQUIPMENTS Total kVA (or MVA) demand depends on the power factor of various equipments and lagging power factor of some of the equipments are tabulated below: Induction motors : 0.6 –0.85 Fractional HP motors : 0.5–0.80 Fluorescent lamps...x Electrical Power Systems 5 6 7 8 4.4 Power Angle Characteristics 4.5 Salient Pole Synchronous Generators 4.6 Transients of Synchronous Machine 4.7 Simplified Representation of Synchronous Machine for Transient Analysis 4.8 DC Components of Stator Currents 4.9 Effect of Load Current Power System Components and Per Unit System 5.1 Introduction 5.2 . distribution system. 2 Electrical Power Systems Fig. 1.2: Part of a power system. Fig. 1.1: Schematic diagram of a power supply system. Figure 1.2 shows part of a typical power system. Structure of Power Systems. 463 Bibliography 465 Index 467 xii Electrical Power Systems Structure of Power Systems and Few Other Aspects 1 1 Structure of Power Systems and Few Other Aspects 1.1 POWER SYSTEMS Generation, Transmission. Electrical Power Systems Contents Preface vii 1. Structure of Power Systems and Few Other Aspects 1 1.1 Power Systems 1 1.2 Reasons for Interconnection 3 1.3 Load Characteristics 3 1.4 Power Factor