Chapter 13. Load Tap Changers - 13 Load Tap Changers 13.1...

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13 Load Tap Changers Dieter Dohnal Maschinenfabrik Reinhausen GmbH 13.1 Introduction. .................................................................. 13 -1 13.2 Switching Principle . ...................................................... 13 -2 13.3 Design Concepts of Today’s Load Tap Changers . ...... 13 -3 Oil-Type Load Tap Changers . Vacuum-Type Load Tap Changers . Tap Position Indication 13.4 Applications of Load Tap Changers . ......................... 13 -17 Basic Arrangements of Regulating Transformers . Examples of Commonly Used Winding Arrangements 13.5 Phase-Shifting Transformers (PSTs). ......................... 13 -20 13.6 Rated Characteristics and Requirements for Load Tap Changers . .................................................... 13 -21 13.7 Selection of Load Tap Changers . ............................... 13 -23 General Selection Criteria . Voltage Connection of Tap Winding during Change-Over Operation . Effects of the Leakage Inductance of Coarse Winding = Tap Winding during the Operation of the Diverter Switch (Arcing Switch) When Passing the Mid-Position of the Resistor-Type Load Tap Changer 13.8 Protection Devices for Load Tap Changers . ............. 13 -28 13.9 Maintenance of Load Tap Changers. ......................... 13 -30 13.10 Refurbishment and Replacement of Load Tap Changers . .............................................................. 13 -31 13.11 Summary. ..................................................................... 13 -31 Today, both the IEEE term ‘‘load tap changer (LTC)’’ and the IEC term ‘‘on-load tap-changer (OLTC)’’ are in the terminology of international standards, but the term ‘‘load tap changer (LTC)’’ is used primarily in this chapter. Load tap changers are one of the indispensable components for the regulation of power transformers used in electrical energy networks and industrial application. This contribution explains the technological developments of resistor-type LTCs as well as of reactor-type LTCs. The general switching principles for LTCs are discussed and applications of LTCs are introduced. Today’s design concepts of LTCs are described including the new generation of vacuum-type LTCs. The vacuum switching technology—used in LTCs—is the ‘‘state-of-the-art’’ design at the present time and for the foreseeable future. Examples of LTC designs and the associated switching principles show the variety of the use of vacuum interrupters. 13.1 Introduction For many decades, power transformers equipped with LTCs have been the main components of electrical networks and industry. The LTC allows voltage regulation and = or phase shifting by varying the transformer ratio under load without interruption. ß 2006 by Taylor & Francis Group, LLC.
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From the beginning of LTC development, two switching principles have been used for the load- transfer operation, the high-speed-resistor-type and the reactor-type. Over the decades, both principles have been developed into reliable transformer components available in a broad range of current and voltage applications to cover the needs of today’s network and industrial-process transformers as well as ensuring optimum system and process control (Goosen, 1996). The majority of resistor-type LTCs are installed inside the transformer tank (in-tank LTCs) whereas the reactor-type LTCs are in a separate compartment, which is normally welded to the transformer tank (Figure 13.1).
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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 13. Load Tap Changers - 13 Load Tap Changers 13.1...

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