EXCITATION SYSTEMS

Presented By:Anurag AgrawalRochak DwivediRohit Akiwatkar

CONTENTS1. Objectives2. Importance of Excitation 3. Basic Generator Control Loops4. Types of Excitation Systems

(a) D.C. Excitation System(b) Static Excitation System(c) Brushless Excitation System.

4. Generator Excitation Scheme of the 330 MWunits.

5. Conclusion

OBJECTIVES

1. To explain the requirement of Excitation System

2. To explain the working of various excitation systems

IMPORTANCE OF EXCITATION

• Regulation of terminal voltage, MVAR and power factor.

• Regulation of load angle.• Ensuring protection of generator.

BASIC GENERATOR CONTROL LOOP

Automatic voltage regulator loop controls the magnitude of terminal voltage.

The excitation is Controlling terminal voltage, MVAR and PF with suitable accuracy.

AVR

Converter

PT

CT

Controller

DC-Discharge

TYPES OF EXCITATION SYSTEM

1. D.C. Excitation System

2. High Frequency (Rotating) Excitation System

3. Static Excitation System

4. Brushless Excitation System

D.C. Excitation SystemIn this system exciter is d.c. commutator generator.Exciter can be driven by direct coupling or through reduction gear.Firstly a relatively small rated output pilot exciter supplies the excitation for main exciter. Secondly the main exciter in turn supplies excitation to main generator rotor.Pilot exciter’s output is regulated by variable resistance through motor driven rheostat, which is controlled via AVR .

~=

SM =

DC Exciter

A.C. Excitation System

Types of A.C. Excitation System:

1. High Frequency Excitation (HFEX) System

2. Static Excitation System

3. Brushless Excitation System

STATIC EXCITATION SYSTEM

1. Main equipments: a. Rectifier transformer.

b. Thyristor rectifier banks.

c. Excitation startup and field discharge equipment.

d. Regulation and operation control circuit.

2. Advantages:

a. Fast Response

b. More efficient and low maintenance

Excitation system main components

AVR

Automatic voltage regulator (AVR)

Thyristor converter

Crowbar

Field breaker

1)

2)

3)

4)

Excitation transformer

BRUSHLESS EXITATION SYSTEM

• No slip rings and brushes.• PMG can be used as the pilot exciter.• Less maintenance required.

• Generator Excitation Scheme of our 330 MW units.

CONCLUSION

• Excitation system is an integral part of generator and thus of a power plant. So it knowledge is of utmost for every engineer working in the plant.