27975171 Inteligent Load Ils

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INTELIGENT LOADSHEDDING(ILS) A N E F FE C T IV E A P P R O A C H T O LO A D

S H E D D IN G



INTRODUCTION

• Load shedding is a process in whicha suitable amount load is thrownoff in order to maintain system

stability during over loadedcondition

• 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/munstable

• Is load shedding necessary



Conventional load sheddingschems

1.Breaker interlock load shedding

2.Under frequecy relay load shedding

3.PLC based load shedding



Breaker interlock loadshedding

• Load sheddingbased on hard-wire signal

&circuit-breakers• Fast load shedding

•

• Load sheddingbased on worstcase scenario

• Only one stageload shedding

• Excessive loadshedding

• Modificationcostlier



Under frequency relay loadshedding

• Used to drop loadautomatically inaccordance withthe pre

determinedschedule

• Fixed load reductionat fixed frequencylevel

• Upon reaching theset point &pre-specified timedelay the relaytrips load breakers

• Cycle repeats until

• Slow responsetime

• Incorrect orexcessive loadshedding

• Analysis knowledgeis lost



PLC based load shedding

• Load sheddingbased on Loadvsnum of generatoronline orunder frequencydetection

• Shed a preset

sequence of load

• Use of distributedn/w via power

managements/m

• Monitoring of power s/m islimited to portionof n/w

• s/m wide operatingcondition ismissing fromdecision makingprocess result inincorrect loadshedding

•

Priority load list’



INTELLIGENT LOADSHEDDING

• Requirements of ILS s/m1.Pre-disturbance operating conditions

2.post-disturbance operatingconditions3.Nature and duration of disturbance

4.s/m transient response to adisturbance



ILS block diagram



Functions of blocks

• Knowledgebase-possess s/m dynamicbehavior

• 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



, W ith th e a rch ite ctu re d e scrib e d a b o v e a n

ILS

sch e m e p ro v id e s th e fo llo w in g b e n e fits:

- ,Tim e v a ria n t lo a d sh e d d in g ta b le s w h ich

re fle ct

,tru e sta tu s a n d lo a d in g co n d itio n s fo r th e

.sh e d d a b le lo a d s

O p tim a l co m b in a tio n o f sh e d d a b le lo a d s to

.m a x im ize lo a d p re se rv a tio n

(Fa st re sp o n se to d istu rb a n ce trig g e rs le ss

than

).1 0 0 m s in m o st case s



O n e lin e d ia g ra m o f o il re fin e ry



T h e in te rn a l e le ctrica l n e tw o rk su p p lie s a to ta l

lo a d

,o f a b o u t 4 5 M W a n d is con stitu te d b y th e

:fo llo w in g

S u b sta tio n in te rco n n e ctin g th e in te rn a le le ctrica l

, -syste m to th e p o w er g rid b y tw o th re e w in d in g

. / . ,tra n sfo rm e rs 3 4 5 1 3 8 kV ra te d a t 2 0 M V A

.su p p ly in g th re e m a in sw itch b o a rd s

In te rn a l d istrib u tio n syste m o p e ra tin g a t 6 0

h e rtz

,o rg a n ize d in to m a in d istrib u tio n sw itch b o a rd s

. . ,ra te d a t 1 3 8 kV a n d 4 1 6 kV w h ich su p p lies

/la rg e M V m o to rs a n d o r d istrib u tio n fe e d e rs a s w e ll a s se ve ra l lo w v o lta g e d istrib u tio n

.sw itch b o a rd s

To ta lg e n e ra tio n o f 1 5 M W o b ta in e d fro m o n e

( ).g en erator G en set C

T h e p la n t is n o rm a lly im p o rtin g 2 3 M W fro m th e



H a rd w a re co n fig u ra tio n o f P LC

/b a se d S m



TABLE I SHEDDABLE LOAD PRIORITY LIST

Load Shed Priority Load ID

MW Shed- ( )1 Aux B Pump

.1 20( % )MCC24AB 30 Load

.2 55( )Aux A Pump

.2 00( % )MCC24AB 30 Load

.2 55

#Desalter 1.4 25

#2 Distillation Unit 1.3 40

#Distillation Unit 3.2 55

#Desalter 2

.4 25( % )3 MCC24AB 40 Load

.4 25#Distillation Unit 5

.2 55 Total Load Shed

.29 55

Frequency response



ILS communication architecture



TABLE II LOADS SHED BY ILS SCHEME Load Shed

Priority Load ID MW Shed

- ( )1 Aux B Pump.1 20( )MCC24AB LV Motors 1

.2 55 ( )Aux A Pump.2 00( )MCC24AB LV Motors

.2 55

#Desalter 1.4 25 2 Distillation

# .Unit 1 3 40 Distillation Unit

# .3 2 55

#3 Desalter 2



conclusion

• ILS is better than any of theconventional load shedding scheme

• ILS is essential for indusrialapplication

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27975171 Inteligent Load Ils