2. 1:-Excitation current determines the strength of the magnetic field of the coil
(along with speed of the rotor). This magnetic field then induces voltage at the
generator terminals.
2:-If the generator is not connected to the load , there is no power flow, but
voltage is even established with this magnetic field.
3:-The generator voltage will be strictly a function of rotor speed and excitation
current .
4:- When load is connected, the generator voltage drops, with the increasing
load.
5:-Voltage regulator however will increase excitation current to maintain
constant generator voltage .
Introduction of synchronous generator excitation
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3. FUNCTIONS OF EXCITATION SYSTEMS
Provide direct current to the synchronous generator field winding,
Perform control and protective functions essential to the satisfactory
operation of the power system
The performance requirements of the excitation system areThe performance requirements of the excitation system are
determined bydetermined by
A )Generator considerations:
supply and adjust field current as the generator output varies within its
continuous capability
respond to transient disturbances with field forcing consistent with the
generator short term capabilities
rotor insulation failure due to high field voltage
rotor heating due to high field current
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4. contribute to effective control of system voltage and Flow of
reactive power
Maintain the power systems stability with (PSS)
Elements of an Excitation System
1.Exciter:
2.Regulator
3.Terminal voltage transducer and load compensator::
4.Power system stabilizer::
5.Limiters and protective circuits
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6. Classified into three broad categories based on the excitation power source:
1.DC excitation systems
2.AC excitation systems
3.Static excitation systems
4.Digital excitation systems
Type of excitation systems
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7. DC excitation system with amplidyne voltage regulators
DC excitation systems
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8. AC Excitation SystemsAC Excitation Systems::
Field controlled alternator rectifier excitation system
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9. AC Excitation SystemsAC Excitation Systems
: Alternator supplied controlled-rectifier excitation system
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10. AC Excitation SystemsAC Excitation Systems
: Brushless excitation system
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14. DIGITAL AVR
The digital AVR is based on the analog AVR’S control functions and makes
use of the advantages of digital equipment such as easier processing
,transmission and recording of information . Its hardware being compact the
digital AVR has high reliability equal to that of the analog AVR.
FUNCTION:
The digital AVR function is same as the analog AVR that is has AVR to
control generator voltage ,UEL(under excitation limit),OEL(over excitation
limit) and PSS. as to the maintenance service functions, the digital AVR has
such function as operation /fault status indication, self diagnostic generation
of generator reference voltage setter step signals for verification of dynamic
characteristics and recording of transient. It is possible to calculate bode
diagram indicate transient responses and calculate rise times by feeding
the recorded transient data to a personal computer via RS232C.
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15. 0-20A DECS-250N
0-2,500Adc DECS-400
0-10,000Adc DECS-2100
Benefits
The DECS family product line offers many integrated features and
functions for regulation, limiting, protection, and data analysis to
make your product selection easy.
DECS products are available for standard or custom solutions to be
utilized on pan chassis or in cubicles as part of a complete system to
fit in your application.
EXCITATION CURRENT IN SPECIAL DECS MODALS
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16. BE1-40Q Loss of Excitation Relay
Protection of loss of excitation
These relays provide protection for
synchronous generators from extensive
damage by detecting loss-of-field excitation.
BENEFIT
Accurate protection provided by true var
measurement.
Minimized CT and PT costs as a result of
low sensing burden.
Reduced battery load with low burden
power supply.
Accurate, repeatable, and reliable
operation.
Simple HMI provides clear and intuitive
settings for easy configuration.
LED targets provide clear annunciation
of status.
Easily perform in-case system and www.basler.com/Products/Protective
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17. Excitation System Application
:
Digital Exciter has Replaced of Brushless Exciter
Digital Exciter has Replaced of Shunt Exciters
Digital Exciters Replacement for ALTERREX
Digital Exciters have very high response that way systems is
more stable
Have very less rotating part for controlling side that way less
rotational loss
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