Chapter 8. Step-Voltage Regulators

Chapter 8. Step-Voltage Regulators - 8 Step-Voltage...

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8 Step-Voltage Regulators Craig A. Colopy Cooper Power Systems 8.1 Introduction. ........................................................................ 8 -1 8.2 Power Systems Applications. .............................................. 8 -3 8.3 Ratings. ................................................................................. 8 -7 8.4 Theory . ................................................................................. 8 -7 8.5 Auto-Booster± 1 ................................................................... 8 -15 8.6 Three-Phase Regulators . ................................................... 8 -15 8.7 Regulator Control. ............................................................. 8 -17 Set Voltage . Bandwidth . Time Delay . Line-Drop Resistive and Reactive Compensation 8.8 Unique Applications . ........................................................ 8 -20 8.1 Introduction Requirements for electrical power become more challenging every day in terms of both quality and quantity. ‘‘Quality’’ means that consumers need stable voltage without distortions and interruptions. ‘‘Quantity’’ means that the user can draw as much load as needed without reducing the quality of the supply. These requirements come from industry as well as from domestic consumers, and each requirement influences the other. Maintaining voltage magnitude within a specified range is an import- ant component of power quality. Power transformers and feeders impose their own impedance, and the amount of voltage drop depends on the loads and, consequently, the currents that flow through them. Voltage magnitudes decrease along the feeder, which means that consumers at the end of the feeder will have the lowest voltage. Distribution systems must be designed in such a way that voltage magnitudes always remain within a specified range as required by standards. This is accomplished through the use of voltage-control equipment and effective system design. Regulating power transformers (load-tap-changing transform- ers, or LTCs), three-phase step-voltage regulators, single-phase step-voltage regulators, and Auto- Boosters± 1 are typical transformer-type equipment used to improve the voltage ‘‘profile’’ of a power system. Most of this section is dedicated to the single-phase step-voltage regulator, shown in Figure 8.1 , that is used in substations and on distribution system feeders and laterals. Figure 8.2 shows the locations on a power system where voltage regulators are commonly applied. Single-phase step-voltage regulators maintain a constant voltage by on-load voltage regulation wherever the voltage magnitude is beyond specified upper and lower limits. A common practice among utilities is to stay within preferred voltage levels and ranges of variation as set forth by ANSI 84.1, Voltage Rating for Electric Power Systems and Equipment, as shown in Table 8.1 . ß 2006 by Taylor & Francis Group, LLC.
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Electric supply systems are to be designed and operated so that most service voltages fall within the range A limits. User systems are to be designed and operated so that, when the service voltages are within range A, the utilization voltages are within range A. Utiliza- tion equipment is to be designed and rated to give fully satisfactory performance within the range A limits for utilization voltages.
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This note was uploaded on 10/19/2010 for the course ENGINEERIN ELEC121 taught by Professor Tang during the Spring '10 term at University of Liverpool.

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Chapter 8. Step-Voltage Regulators - 8 Step-Voltage...

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