pow sys ope & con - m rajkuamr - iii eee

7/21/2019 Pow Sys Ope & Con - M Rajkuamr - III EEE

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EE 6603 – POWER SYSTEM OPERATION AND CONTROL SEM & BRANCH: 06 & EEE

UNIT-1

INTRODUCTION

1. What ! "#a$ %'()*

Load curve is the curve drawn between the variations of load on the power

station with reference to time.

+. What ! $a", "#a$ %'()*

Daily load curve is the curve drawn between the variations of load with

reference to various time period of day.

3. What ! #th", "#a$ %'()*

Monthly load curve is plotted from the average value of the power at a

month for a different time periods. It is obtained from daily load curve.

/. What ! ,)a'", "#a$ %'()*

Yearly load curve is obtained from monthly load curve which is used to find

annual load factor.

. What ! %#)%t)$ "#a$*

Connected load is the sum of continuous ratings of all the equipments

connected to supply systems.

6. What ! a $)a$*

Maximum demand is the greatest demand of load on the power station

during a given period.

2. What ! $)a$ a%t#'*

Demand factor is the ratio of maximum demand to connected load.

Demand factor !max demand"# !connected load"

4. What ! a()'a5) $)a$*

$verage demand is the average of loads occurring on the power station in a

given period !day or month or year".

Daily average demand !no of units generated per day"# !%& hours"

Monthly average demand !no of units generated in month"# !no of

hours in a month"

in the order of descending magnitudes.

M. RA7UMAR8 AP – EEE + & 16 Ma'9! & A Pa5) 1




;.What ! "#a$ a%t#'*

Load factor the ratio of average load to the maximum demand during a given

period.

10. What ! $()'!t, a%t#'*

Diversity factor is the ratio of the sum of individual maximum demand on power

station.

11. What ! %a<a%t, a%t#'*

Capacity factor is the ratio of actual energy produced to the maximum possible

energy that could have been produced during a given period.

1+. What ! <"at !) a%t#'*

'lant use factor is the ratio of units generated to the product of plant capacity and

the number of hours for which the plant was in operation.

13. What ! "#a$ $'at# %'()*

Load duration curve is the curve obtained when the load elements of a load curve are

arranged.

1/. D)) "#a$ a$ "!t #t th) t,<)! # "#a$!.

Load is a device that taps energy from networ(.

)ypes*

+. Lighting and heating loads.

%. Induction motors. ,. -lectronic devices

1. Wh, th) ')=)%, a$ (#"ta5) a') t# >) ')5"at)$ <#?)' !,!t)*

oltage regulation*

oltage regulation helps in maintaining the voltage at the load terminals within

prescribed limits under conditions/ by employing suitable voltage control equipment.

16.What ! )at >, ')) 5#()'#' #<)'at#*

0nly governor control is called as free governor action. It can be obtained by deactivating

the integral controller.

12.M)t# th) %#$t#! #' #<)'at5 t?# !,%h'##! a%h)! <a'a"")".

!i" )erminal voltage must be same.

!ii" 1ystem frequency must be same.

!iii" 'hase sequence must be same

14.D)) $a",8 #th",8 aa" "#a$ %'().$a", "#a$ %'().

M. RA7UMAR8 AP – EEE + & 16 Ma'9! & A Pa5) +




3. What a') th) %#<#)t! # !<))$ 5#()'#' !,!t) # a a"t)'at#'* D)'() a

t'a!)' %t# a$ !9)t%h a >"#%9 $a5'a

Load frequency control

-conomic dispatch control

$utomatic voltage regulator

/. Wth )at !9)t%h $)!%'>) th) P- a$ - %#t'#" !t'%t')

- C0<)=0L L00'

'28 C0<)=0L L00'

'rimary $L8C

1econdary $L8C:

. B')", $!%!! th) %"a!!%at# # "#a$! a$ "!t #t th) <#'tat %ha'a%t)'!t%!

# (a'#! t,<)! # "#a$!

1ystem load variation

'lant Capacity 8actor*

'lant 7se 8actor

M. RA7UMAR8 AP – EEE + & 16 Ma'9! & A Pa5) /




UNIT-II

REAL POWER –REUENCY CONTROL

1. What ! th) a#' %#t'#" "##<! !)$ "a'5) 5))'at#'!*

)he ma>or control loops used in large generators are

i. $utomatic voltage regulator !$="

ii. $utomatic load frequency control !$L8C".

+. What ! th) !) # !)%#$a', "##<*

1econdary loop is used to maintain the fine ad>ustment of the frequency/ and also

by reset action maintains proper M: interchange with other pool members. )his loop is

insensitive to rapid load and frequency changes but focuses instead on drift li(e changeswhich ta(e place over periods of minutes.

3. What ! th) a$(ata5) # AR "##< #()' ALC*

)he advantage of $= loop over $L8C is very fast and therefore there is a

tendency/ for the $= dynamics to settle down before they can ma(e themselves felt in

the slower load frequency control channel.

/. What ! th) $)')%) >)t?)) "a'5) a$ !a"" !5a" aa",!!*

)he difference between large and small signal analysis is given below.Large signal analysis is used where voltage and power may undergo sudden

changes of magnitude that may approach +44 percent of operating values.7sually this type of analysis leads to differential equations of non2linear type.

.What ! th) )%t)'*

)he exciter is the main component in $= loop. It delivers the DC power to the

generator field. It must have adequate power capacity and sufficient speed of response

!rise time less than 4.+ sec".

6. What ! th) %t# # AR*

)he function of the $= is to provide constancy of the generator terminal voltage

during normal/ small and slow changes in the load.

2. E<"a a>#t !tat% AR "##<.

In a static $= loop/ the execution power is obtained directly from the generator

M. RA7UMAR8 AP – EEE + & 16 Ma'9! & A Pa5)




terminals or from the station service bus. )he $C power is rectified by thyristor bridges

and fed into the main generator field via slip rings. 1tatic exciters are very fast and

contribute to improved transient stability.

4. W't) th) !tat% <)'#'a%) # AR "##<.

1tatic performance of $= loop is to regulate the terminal ?? to within required

static accuracy limit/ have sufficient speed of response and be stable.

;. What ! th) $!a$(ata5) # h5h "##< 5a* H#? t ! t# >) )"at)$*

)he disadvantage of high loop gain is that it causes undesirable dynamic

response/ possibly instability. 3y adding series $<D#0= feedbac( stability compensation

to the $= loop/ this conflicting situation can be resolved.

10. What a') th) ))%t! # 5))'at#' "#a$5 AR "##<*

-ffects of generator loading in $= loop is given below. $dded load does not change the basic

features of the $= loop@ it will however affect the values of both gain factor Af and the field

constant. Bigh loading will ma(e the generator wor( at higher magnetic saturation levels. )his

means smaller changes in ?-? for incremental increases in if/ translating into the reduction of A8.

)he field time constant will li(ewise decrease as generator loading closing the armature current

paths. )his circumstance permits the formation of transient stator currents the existence of which

yields a lower effective field induction

11. What a') th) %t#! # ALC*

8unction of $L8Cs is to maintain desired M: output of a generator unitand assist in controlling the frequency of large interconnection. )he $L8C also helps to

(eep the net interchange of power between pool members at predetermined values.

Control should be applied in such a fashion that highly differing response characteristics

of units of various types are recognied. $lso unnecessary power output changes should

be (ept at a minimum in order to reduce wear of control valves.

1+. S<)%, th) $!a$(ata5) # ALC "##<.

)he disadvantage of $L8C loop is that it will control only during normal changes

in load and frequency. It is unable to provide adequate control during emergency

situations/ when large M: imbalances occur.

13. H#? ! th) ')a" <#?)' a <#?)' !,!t) %#t'#"")$*

)he real power in a power system is being controlled by controlling the driving

torque of the individual turbines of the system.





1/. What ! th) ))$ #' "a'5) )%ha%a" #'%)! !<))$-5#()'5 !,!t)*

ery large mechanical forces are needed to position the main valve against the

high stream pressure and these forces are obtained via several stages of hydraulic

amplifiers

PART-B

1. U!5 a !<")$ %t#a" $a5'a )<"a th) #<)'at5 )at')! # a !<))$

5#()'5 !,!t).

+. D)()"#< a ")a' ath)at%a" #$)" # a !<))$ 5#()'5 !,!t).

3. E<"a th) t)%h=) (#"()$ "#a$ ')=)%, %#t'#" @LC# a !5") a')a

!,!t)./. E<"a th) <'%<")8 (#"()$ t) ") ')=)%, %#t'#" %a!) # t?# a')a

!,!t).

. D)t)') th) <'a', ALC "##< <a'a)t)' #' a %#t'#" a')a ha(5 th)

#""#?5

Data :

T#ta" 'at)$ a')a %a<a%t,8 P' F+000MW

N#'a" O<)'at5 L#a$8 P$F1000MW

I)'ta %#!tat8 HF !)%

RF+./HG<.. MW @a"" a')a 5))'at#'!

W) !ha"" a!!) that th) "#a$ ')=)%, $)<)$)%, a! ")a' )a5 that th) #"$ "#a$?#"$ %')a!) 1 #' 1 ')=)%, %')a!)!

UNIT-III

REACTIE POWER – OLTAE CONTROL





1. What a') th) !#'%)! # ')a%t() <#?)'* H#? t ! %#t'#"")$*

)he sources of reactive power are generators/ capacitors/ and reactors.

)hese are controlled by field excitation.

+. () !#) )%tat# !,!t) a<")'.

)he excitation system amplifiers are/

i. Magnetic amplifier

ii. =otating amplifier

iii. Modern electronic amplifier.

3. Wh) ! ))$>a%9 !ta>"t, %#<)!at# !)$*

8eedbac( stability compensation is used to resolve the effect of high loop gain in

$=. Bigh loop gain is needed for static accuracy but this causes undesirable dynamic

response/ possibly instability.

/. () th) %ha'a%t)'!t%! # ") %#<)!at#'!.

)he characteristics of line compensators are/

i. 8erranti effect is minimied.

ii. 7nder excited operation of synchronous generator is not required.

. What ! 9#? a! >a9 # %a<a%t#'!* H#? t ! a$!t)$*

3an( of capacitors is the arrangement of number of capacitors connected in

parallel to get the desired capacitance. )hese can be ad>usted in steps by switching

!mechanical".

6. What ! th) $!a$(ata5) # !?t%h)$ %a<a%t#'! a') )<"#,)$ #' %#<)!at#*

:hen switched capacitors are employed for compensation/ these should

be disconnected immediately under light load conditions to avoid excessive voltage rise

and 8erro resonance in presence of transformers.

2. What a') th) ))%t! # %a<a%t#' !)')! %#<)!at# %'%t*

)he effects of capacitor in series compensation circuit are/





i. oltage drop in the line reduces.

ii. 'revents voltage collapse.

iii. 1teady state power transfer increases.

iv. )ransient stability limit increases.

4. () t?# 9$! # %a<a%t#'! !)$ !ht %#<)!at#'.

)he two (inds of capacitors used in shunt compensator are/

i. 1tatic ar Compensator !1C"

ii. )hyristor 1witched Capacitor

;. What ! !,%h'##! %#$)!)'*

1ynchronous condenser is a synchronous motor running at no2load and having

excitation ad>ustable over a wide range. It feeds positive $=s into the line under

overexcited conditions and negative $=s when under excited.

10. W't) a>#t !tat% AR %#<)!at#' @SC.

1tatic $= Compensator !1C" comprise capacitor ban( fixed or switched or

fixed capacitor ban( and switched reactor ban( in parallel. )hese compensators draw

reactive power from the line thereby regulating voltage/ improve stability !steady state

and dynamic"/ control overvoltage and reduce voltage and current unbalances. In BDCapplication these compensators provide the required reactive power and damp out sub

harmonic oscillations.

11. What a') !tat% AR !?t%h)! #' !,!t)!*

1tatic $= switches or systems are 1tatic $= compensators which use

switching for $= control. It means that terminology wise 1C11.

1+. () !#) # th) !tat% %#<)!at#'! !%h))!.

1chemes of static compensators

i. 1aturated reactor

ii. )hyristor2 Controlled =eactor !)C="

iii. )hyristor 1witched capacitor !)1C"

iv. Combined )C= and )1C compensator.

M. RA7UMAR8 AP – EEE + & 16 Ma'9! & A Pa5) ;




13. What ! ta< %ha55 t'a!#')'!*

)ap changing transformers are the power transformers and many distribution

transformers which have taps in one or more windings for changing the turns ratio.

1/. W't) th) t,<)! # ta< %ha55 t'a!#')'!.

)ypes of tap changing transformers

i. 0ff2 load tap changing transformers.

ii. )ap changing under load transformers.

1. What ! th) !) # #-"#a$ ta< %ha5)' a$ TCUL*

)he off2 load tap changers are used when it is expected that the ratio will need to be changed only infrequently/ because of load growth or some seasonal change. )C7L is

used when changes in ratio may be frequent or when it is undesirably to de2energie the

transformer to change the tap.

PART - B

1. D'a? th) %'%t $a5'a #' a t,<%a" )%tat# !,!t) a$ $)'() th) t'a!)'

%t# #$)" a$ $'a? th) >"#%9 $a5'a.

+. D!%!! 5))'at# a$ a>!#'<t# # ')a%t() <#?)'.

3. E<"a $)')t t,<)! # !tat% AR %#<)!at#'! ?th a <ha!#' $a5'a.

/. D!%!! a>#t th) (a'#! )th#$! # (#"ta5) %#t'#".

. D)'() th) ')"at#! >)t?)) (#"ta5)8 <#?)' a$ ')a%t() <#?)' at a #$) #'

a<<"%at#! <#?)' !,!t) %#t'#"





UNIT-I

UNIT COMMITMENT AND ECONOMIC DISPATCH

PART-A

1. D)) )%##% $!<at%h <'#>").

-conomic dispatch problem is defined as the problem which minimies the

operating cost of active power generation.

+. D)) %'))ta" %#!t.

Incremental cost is defined as the rate of change of fuel cost with active power generation.

3. W't) th) "#a$ >a"a%) )=at#.

Load balance equation is given below.

'g2'd2'L4.

/. D)) >a!) <#t.

3ase point is defined as the present operating point of the system.

. D)) <a't%<at# a%t#'.

'articipation factor is defined as the change in generation required to meet power

demand.

6. D)) h,$'#th)'a" !%h)$"5 <'#>").

Bydrothermal scheduling problem is defined as the problem of minimiing the

thermal generation cost with the constraints of water availability.

2. D)) t %#t)t.

7nit commitment is defined as the commitment of minimum generator to meet

the required demand.





4. D)) !<5 ')!)'().

1pinning =eserve is defined as the term that describes the total amount of

generation availability from all units synchronied on the system.

;. What ! )at >, !%h)$")$ ')!)'()*

1cheduled reserve include quic( start diesel turbine units as well as most

hydro units and pumped storage hydro units that can be brought online/ synchronied and

brought up to full capacity quic(ly.

10. What a') th) th)'a" t %#!t'at!*

)he thermal unit constraints are

i. Minimum up time

ii. Minimum down time

iii. Crew constraints.

11. What a') th) t?# a<<'#a%h)! t# t')at a th)'a" t t# #<)'at5 t)<)'at')*

)he two approaches to treat a thermal unit to operating temperature are given

below.

i. $llows the unit boiler to cool down and then heat bac(up to operating

temperature in time for a scheduled turn on.

ii. =equires that sufficient energy be input to the boiler to >ust maintain

operating temperature.

1+. What a') th) t)%h=)! #' th) !#"t# # th) t %#t)t <'#>")*

)he techniques for the solution of the unit commitment problem are

i. 'riority list method

ii. Dynamic programming

iii. Lagrange relation

13. What a') th) a!!<t#! a$) $,a% <'#5'a5 <'#>")*

)he assumptions made in dynamic programming problem are given

below.

M. RA7UMAR8 AP – EEE + & 16 Ma'9! & A Pa5) 1+




i. $ state consists of an array of units with specified units operating and the

rest of the time.

ii. )he startup cost of a unit is independent of the time it has been offline.

iii. )here are no costs for shutting down the units.

1/. D)) "#5 'a5) h,$'# !%h)$"5 <'#>").

Long range hydro scheduling problem is defined as the problem involves the long

range of water availability and scheduling of reservoir water releases. 8or an interval of

time that depends on the reservoir capacities.

1. What a') th) #<tGat# t)%h=)! #' "#5 'a5) h,$'# !%h)$"5 <'#>")*

)he optimiation techniques for long range hydro scheduling problem arei. Dynamic programming

ii. Composite hydraulic simulation methods

iii.1tatistical production cost

16. D)) !h#'t 'a5) h,$'# !%h)$"5 <'#>").

1hort range hydro scheduling problem is defined as the hour by hour scheduling

of all generators on a system to achieve minimum production condition for the given

time period.

12. D)) !,!t) >"a%9#t <'#>").

1ystem blac(out problem is defined as the event occurs on a system that leaves it

operating with limits violated@ the event may be followed by a series of further actions

that switch other equipment out of service. If the process of cascading failures continues/

the entire system of it may completely collapse.

14. What ! )at >, %a!%a$5 #ta5)!*

Cascading outages are the process if one of the remaining lines is now too heavily

loaded/ it may open due to relay action/ thereby causing even more load on the remaining

lines.

PART-B





1. D)'() th) %##'$at# )=at# ?th "#!!)! )5")%t)$.

+. D)'() th) %##'$at# )=at# # a JK >! <#?)' !,!t) ta95 t# a%%#t th)

))%t #

!,!t) "#!!)!.

3. D)'() th) )<')!!# #' >a!) <#t a$ <a't%<at# )th#$.

/. Stat) th) t %#t)t <'#>"). Wth th) h)"< # "#?%ha't )<"a #'?a'$

$,a%

<'#5'a5 !#"t# )th#$.

. E<"a P'#'t, "!t )th#$ !5 "" L#a$ a()'a5) <'#$%t# %#!t. Stat) th)

)'t! a$

$))'t!.

M. RA7UMAR8 AP – EEE + & 16 Ma'9! & A Pa5) 1/




UNIT-

COMPUTER CONTROL O POWER SYSTEM

1. What a') th) %t#! # %#t'#" %)t)'*

)he functions of control center are

. 1ystem monitoring

ii. Contingency analysis

iii. 1ecurity constrained optimal power flow.

+. What ! th) %t# # !,!t) #t#'5*

a. 8unction of system monitoring is to provide updated information about the power

system.

3. What ! SCADA !,!t)*

1C$D$ stands for supervisory control and data acquisition system. It allows a

few operators to monitor the generation and high voltage transmission systems and to

ta(e action to correct overloads.

/. What a') th) !tat)! # <#?)' !,!t)*

)he states of power system are

i. <ormal state

ii. $lert mode

iii. Contingency mode

iv. -mergency mode.

. D)) #'a" #$).

<ormal mode is defined as the mode of operation if the system is in secure even

the occurrence of all possible outages has been simulated the system remain secure.

6. D)) a")'t #$).





$lert mode is defined as the mode of operation of the system that it does not

remain in the secure for the occurrence of all possible outages.

2. What a') th) $!t'>t# a%t#'!*

)he distribution factors are

i. Line outage distribution factor

ii. 9eneration outage distribution factor.

4. D)) !tat) )!tat#.

1tate estimation is defined as the process of assigning a value to an un(nown

system state variable based on measurements from that system according to some criteria.

;. D)) a "9)"h##$ %'t)'#.

Maximum li(elihood criterion is defined as the problem of maximiing the

probability that estimate the state variable x/ is the true value of the state variable vector

!i.e/ to maximie the '!x" x".

10. D)) ?)5ht)$ ")a!t-!=a')! %'t)'#.

:eighted least2squares criterion is defined as the problem of minimiing the sumof the squares of the weighted deviations of the estimated measurements/ from the actual

measurement.

11. D)) (a'a%) %'t)'#.

Minimum variance criterion is defined as the problem of minimiing the expected

value of the squares of the deviations of the estimated components of the state variable

vector from the corresponding components of the true state variable vector.

1+. D)) !t ' %#!t'at.

Must run constraint is defined as the condition that some units are given a must

run status during certain times of the year for reason of voltage support on the

transmission networ(.

13. D)) )" %#!t'at.





8uel constrain is defined as the condition if a system in which some units have

limited fuel or else have constraints that require them to burn aspecified amount of fuel in

a given time.

1/. What a') th) a!!<t#! a$) <'#'t, "!t )th#$*

)he assumptions made in priority list method are

i. <o load cost is ero

ii. 7nit input2output characteristics are linear between ero output and full

load

iii. )here are no other restrictions startup cost are affixed amount.

1. Stat) th) a$(ata5)! # #'?a'$ $,a% <'#5'a5 a<<'#a%h.

$dvantage of forward D' approach is given below. If the start up cost of a unit is

a function of the unit is a function of the time it has been offline/ then a forward dynamic

program approach is more suitable since the previous history of the unit can be computed

at each stage.

16. Stat) th) $!a$(ata5)! # $,a% <'#5'a5 )th#$.

)he disadvantage of dynamic programming method is that it has the necessity of forcing the dynamic programming solution to search over a small number of commitment

states to reduce the number of combinations that must be tested in each period.

12. What a') th) 9#? (a")! !h#'t t)' h,$'# !%h)$"5 <'#>")*

Anown values in short term hydro scheduling problem are

i. )he load

ii. Bydraulic inflows

iii. 7nit availabilities.

14. What ! )at >, t)"))t', !,!t)*

)elemetry system is the process of measurement of state of the system and





transmission of these states to a control center.

1;. What a') th) %t#! # !)%'t, %#!t'a)$ #<ta" <#?)' "#?*

)he functions of security constrained optimal power flow are

i. Contingency analysis is combined with an optimal power flow which

see(s to ma(e changes to the optimal dispatch of generation

ii. $s well as other ad>ustments/ so that when a security analysis is run/ no

contingency result in violations.

+0. D)) th) !tat) # #<ta" $!<at%h.

)he state of optimal dispatch is defined as the state that the power system is in prior to any contingency. It is optimal with respect to economic operation but may not be

secure.

+1. D)) <#!t %#t5)%,.

'ost contingency is defined as the state of the power system after a contingency

has occurred.

++. D)) !)%') $!<at%h.

1ecure dispatch is defined as the state of the power system with no contingency

outages/ but with correction to the operating parameters to account for security violations.

'$=)23

1. B')", $!%!! th) (a'#! %t#! # ))'5, %#t'#" %)t')

+. E<"a th) $)')t #<)'at5 !tat)! # <#?)' !,!t) ?th !tat) t'a!t# $a5'a.

3. E<"a th) ha'$?a') %#<#)t! # SCADA ?th )at $a5'a a$ a"!# )t#

th) %t#! # t.

/. E<"a a>#t <#?)' !,!t) !)%'t,





. What ! EMS* What a') t! a#' %t#! <#?)' !,!t) #<)'at# a$ %#t'#"*

M. RA7UMAR8 AP – EEE + & 16 Ma'9! & A Pa5) 1;

pow sys ope & con - m rajkuamr - iii eee

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