INTELLIGENT
LOAD SHEDDING
PRESENTED BY
SUGANDHA SHARMA
WHAT IS LOAD SHEDDING
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Excess of load over available generation
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Drop in frequency
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Casacading effect
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To avoid this, some load is shed
CONCEPT OF LOADSHEDDING
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Excitation / Generator – Reactive Power –
Voltage
Drainage of reactive power
Call its over excitation capibility
Prime Mover / Generator – Real Power Frequency
Frequency drainage
Stored energy varies
TYPE OF ACTION REQUIRED
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Require fast response
Longer delays,require more load to be shed
Generation control cannot act fast enough
Disturbance type and location
System response different depending on location
of disturbance
Different load shedding strategy
Normal and abnormal operating conditions
CONVENTIONAL TECHNIQUES
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BREAKER INTERLOCK SCHEME
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UNDER FREQUENCY RELAY SCHEME
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PLC BASED LOAD SHEDDING
BREAKER INTERLOCK SCHEME
DISADVANTAGES
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Difficult to change load priority
Only one stage of load shedding is
available
More loads are shed than necessary
UNDER FREQUENCY RELAY
SCHEME
DISADVANTAGES
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Slow response time of frequency relays
Incorrect Load may be Dropped Causing
Undesirable Blackouts
Analysis knowledge is lost
PLC BASED LOAD SHEDDING
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circuit breaker tripping programmed
Modification of the logic requires changing programmed
logic
ADVANTAGE: access to actual operating status of the
power system
DISADVANTAGE: pre-defined load priority tables in the
PLC
“load shedding system uses real
time system-wide data acquisition
that continually updates a
computer based real-time system
model”
BLOCK DIAGRAM OF ILS
COMPONENTS OF ILS
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LOAD PRESERVATION
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LOAD RESTORATION
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LOAD SHEDDING VALIDATION
LOAD PRESERVATION
 Calculates minimum
required power to be
shed
 Selects optimal
combination of loads
 Different load priority
tables, load groups,
options, calculation
method etc.
LOAD RESTORATION
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Available spinning reserve
Starting voltages
Operating voltages
User-defined logic
Alternate source
detection
System configuration
status
system frequency
interlock and switching
sequence logics
LOAD SHEDDING VALIDATION
IMPLEMENTATION CONFIGURATION OF ILS
SOFTWARE IMPLEMENTATION OF
ILS
SOFTWARE IMPLEMENTATION OF
ILS
SOFTWARE IMPLEMENTATION OF
ILS
SOFTWARE IMPLEMENTATION OF
ILS
SOFTWARE IMPLEMENTATION OF
ILS
SOFTWARE IMPLEMENTATION OF
ILS
SOFTWARE IMPLEMENTATION OF
ILS
SOFTWARE IMPLEMENTATION OF
ILS
SOFTWARE IMPLEMENTATION OF
ILS
KEY FETURES OF ILS
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Hardware independent
Supports large number of protocols and standards
User-defined load priority
User defined load groups
Unlimited load shedding schedules
Operator friendly interface
On-line testing to validate ILS actions
Load restoration
Eliminate unnecessary load shedding
Reduction of downtime for critical loads
Reduction of spinning reserve requirements
Reliable load preservation system
Fast response to electrical & mechanical disturbances
Robust calculation method
Operator alerts for marginal operating conditions
Reliable
COMPARISON OF ILS WITH OTHER
TECHINQUES
APPLICABLE SYSTEMS
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Oil and chemical refineries
Oil production fields
Oil platforms
Mining
Cement and paper facilities
Manufacturing plants
Generation plants
Distribution system
REFERENCES
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Edward Kimbark, Power System Stability, Wiley-IEEE,
February 1, 1995.
Warren C. New, Load Shedding, Load Restoration and
Generator Protection using Solid State
andElectromechanical Underfrequency Relays,
GeneralElectric.
Tom Wilson, PLC Based Substation Automation andSCADA
Systems; Selecting a Control SystemIntegrator, Western
Electric Power Institute, March 1999.
Kevin Warwick, Arthur O., Ekwue and Raj
Aggarwal,Artificial Intelligence Techniques in Power
Systems
www.etap.com
QUERIES???