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INTELIGENT LOAD SHEDDING(ILS).pptx (Size: 219.32 KB / Downloads: 589)
INTELIGENT LOAD SHEDDING(ILS)
AN EFFECTIVE APPROACH TO LOAD SHEDDING
INTRODUCTION
¢ Load shedding is a process in which a suitable amount load is thrown off
in order to maintain system stability during over loaded condition
¢ Generation- load unbalance problems
¢ Load shedding in industrial units
Problems of frequency decay
¢ Frequency is propotional to speed
¢ Gas turbines are sensitive to frequency
¢ Low frequency problem with thermal power plants
¢ Frequency decay affects quality of industrial products
¢ Frequency below 49.5Hz make s/m unstable
¢ Is load shedding necessary
Conventional load shedding schems
1.Breaker interlock load shedding
2.Under frequecy relay load shedding
3.PLC based load shedding
Breaker interlock load shedding
¢ Load shedding based on hard-wire signal &circuit-breakers
¢ Fast load shedding
¢ Load shedding based on worst case scenario
¢ Only one stage load shedding
¢ Excessive load shedding
¢ Modification costlier
Under frequency relay load shedding
¢ Used to drop load automatically in accordance with the pre determined
schedule
¢ Fixed load reduction at fixed frequency level
¢ Upon reaching the set point &pre-specified time delay the relay trips load
breakers
¢ Cycle repeats until s/m frequency recovered
¢ Slow response time
¢ Incorrect or excessive load shedding
¢ Analysis knowledge is lost
PLC based load shedding
¢ Load shedding based on Load vs num of generator online or under
frequency detection
¢ Shed a preset sequence of load
¢ Use of distributed n/w via power management s/m
¢ Automatic load relief
¢ Monitoring of power s/m is limited to portion of n/w
¢ s/m wide operating condition is missing from decision making process result
in incorrect load shedding
¢ Priority load list doesn™t
take into account the dynamic behaviour of the s/m
INTELLIGENT LOAD SHEDDING
¢ Requirements of ILS s/m
1.Pre-disturbance operating conditions
2.post-disturbance operating conditions
3.Nature and duration of disturbance
4.s/m transient response to a disturbance
Functions of blocks
¢ Knowledgebase-possess s/m dynamic behavior
¢ Advanced Monitoring
¢ Network Models
¢ Trigger List
¢ Load Shed Optimizer- computes optimal load shedding
¢ tables corresponding to system changes.
¢ Distributed Controls -utilize PLCs to rapidly execute the load shedding
actions
¢ With the architecture described above, an ILS
¢ scheme provides the following benefits:
¢ ¢ Time-variant load shedding tables, which reflect
¢ true status, and loading conditions for the
¢ sheddable loads.
¢ ¢ Optimal combination of sheddable loads to
¢ maximize load preservation.
¢ ¢ Fast response to disturbance triggers (less than
¢ 100 ms in most cases).
¢ ¢ Environment to accelerate operator training with
¢ the ability to simulate and validate load shed decicion
¢ The internal electrical network supplies a total load
¢ of about 45 MW, and is constituted by the following:
¢ ¢ Substation interconnecting the internal electrical
¢ system to the power grid by two, three-winding
¢ transformers 34.5/13.8 kV rated at 20 MVA,
¢ supplying three main switchboards.
¢ ¢ Internal distribution system operating at 60 hertz
¢ organized into main distribution switchboards,
¢ rated at 13.8 kV and 4.16 kV, which supplies
¢ large MV motors and/or distribution feeders as
¢ well as several low voltage distribution
¢ switchboards.
¢ ¢ Total generation of 15 MW obtained from one
¢ generator (Genset C).
¢ ¢ The plant is normally importing 23 MW from the
¢ utility, is supplemented by an onsite generator.
¢ ¢ Frequency relays are located throughout the
¢ system including the terminal bus of an onsite generator
conclusion
¢ ILS is better than any of the conventional load shedding scheme
¢ ILS is essential for indusrial application