power system simulation lab - questions

7/30/2019 POWER SYSTEM SIMULATION LAB - QUESTIONS

1/13

1.a) :-

A three-phase transposed line composed of one ACSR, 1,43,000 cmil,47/7 Bobolink conductor per phase with flat horizontal spacing of11m between phases a and b and between phases b and c. Theconductors have a diameter of 3.625 cm and a GMR of 1.439 cm.

The spacing between the conductors in the bundle is 45 cm.

1.b) :-The line is to be replaced by a three conductor bundle of ACSR477,000-cmil, 26/7 Hawk conductors having the same cross sectionalarea of aluminum as the single- conductor line. The conductors have adiameter of 2.1793 cm and a GMR of 0.8839 cm. The new line will alsohave flat horizontal configurations, but it is to be operated at ahigher voltage and therefore the phase spacing is increased to 14mas measured from the centre of the bundles. The spacing betweenthe conductors in the bundle is 45 cm.

(i) Determine the inductance and capacitance per phase perkilometer of the above two lines.

(ii) Verify the results using the available program.

Write the following questions answer:-

1. What is conductor?2. How power system studies are carried out?3. What are the different arrangements of conductors of the transmission lines?4. What is the purpose of transmission lines?5. What is the difference between conductors and insulators?


2/13

A 345 kV double circuit three phase transposed line is composed oftwo ACSR, 1,431, 000cmil, 45/7 bobolink conductors per phase withvertical conductor configuration as shown in Figure. The conductorshave a diameter of 1.427 inch and the bundle spacing is 18 inch.

i) Find the inductance and capacitance per phase per kilometer of the

line.

ii) Verify the results using the available program.

a 15m c

7m 18

b 20.5m b

6.5m

c 16.5m a


1. Which type of conductor is used in high voltage transmission?

2. What is the major advantage of a double circuit tower?3. What happens if the capacitance of a transmission line is high?4. How will you compare copper with aluminium as a conductor?5. Which type of conductor is used in high voltage transmission?


3/13

Using AU power software for formation of bus admittance matrixY ofa power network using the Two Rule Method.

3-BUS, 3-LINES POWER SYSTEM Single-Line Diagram

Transmission Line Data:

LineID.No

Send BusNo. ReceiveBus No. ResistP.U ReactanceP.U.

Half LinechargingSuscept

RatingMVA

1 1 6 0.125 0.500 0.0 502 1 4 0.080 0.300 0.0 603 4 6 0.075 0.400 0.0 30


1. What is single line diagram (or) one line diagram?2. Mention the advantages of bus admittance matrix Y Bus.3. What are the methods available for forming bus impedance matrix?4. Define the way of representation of power system quantities.5. How the network equations can be formed?

1

2

3


4/13

(i) Prepare the data for the 6-bus system described in the Annexure.

( i i ) S p e c i f y the convergence tolerance of 0.01 MW

(iii) Run the GSLF program with an acceleration factor of 1.4 and a

convergence for voltage tolerance of 0.0001 p.u and plot the

convergence characteristics, P versus iteration number.

ANNEXURE

6-BUS, 7-LINES / TRANSFORMER POWER SYSTEM Single-Line

Diagram

Buses : 6, numbered serially from 1 to 6Lines : 5, numbered serially from L1 to L5Transformers: 2, numbered serially as T1 and T2Shunt Load : 2, numbered serially as s1 and s2Base MVA : 100

Bus Data P-V Buses:

Bus IDNo.

Generation, MW Demand Gen. LimitMVAR

ScheduledVolt ( .u)Schedul Max Min MW MVAR Max Min

1 ? 200 40 0.0 0.0 100.0 -50.0 1.022 50.0 100 20 0.0 0.0 50.0 -25.0 1.02


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Bus Data P-Q Buses

Bus ID No Demand Volt. Mag.AssumedMW MVAR

3 55.0 13.0 1.04 0.0 0.0 1.05 30.0 18.0 1.0

6 50.0 5.0 1.0

Transmission Line Data:LineID.

No

Send BusNo.

ReceiveBus No.

ResistP.U

Reactance

P.U.


RatingMVA

1 1 6 0.123 0.518 0.0 552 1 4 0.080 0.370 0.0 653 4 6 0.087 0.407 0.0 30

4 5 2 0.282 0.640 0.0 555 2 3 0.723 1.050 0.0 40

Transformer Data:TransformerID.No

Send (*)Bus No.

ReceiveBus No.

Resist.P.U

ReactanceP.U.

Tap Ratio RatingMVA

1 6 (*) 5 0.0 0.300 1.000 30

2 4 (*) 3 0.0 0.133 1.000 55

(*) Note: The sending end bus of a transformer should be the tap side.

Shunt Element Data:Shunt ID No. Bus ID. No. Rated Capacity

MVAR *1 4 2.02 6 2.5

(*) Note: Sign for capacitor : +veSign for Inductor : -ve


1. Why power flow analysis is made?2. States the major steps involved in load flow studies.3. What are the different types of buses in a power system?4. What is an acceleration factor?5. What do you mean by a flat voltage start?


6/13

a.Prepare the data for the 6-bus system described in the Annexure.

b . S p e c i f y the convergence tolerance of 0.01 MW

c. Run the GSLF program

ANNEXURE

6-BUS, 7-LINES / TRANSFORMER POWER SYSTEM Single-Line

Diagram

Buses : 6, numbered serially from 1 to 6Lines : 5, numbered serially from L1 to L5Transformers: 2, numbered serially as T1 and T2Shunt Load : 2, numbered serially as s1 and s2Base MVA : 100

Bus Data P-V Buses:

Bus IDNo.

Generation, MW Demand Gen. LimitMVAR

ScheduledVolt ( .u)Schedul Max Min MW MVAR Max Min

1 ? 200 40 0.0 0.0 100.0 -50.0 1.022 50.0 100 20 0.0 0.0 50.0 -25.0 1.02


7/13

Bus Data P-Q Buses

Bus ID No Demand Volt. Mag.AssumedMW MVAR

3 55.0 13.0 1.04 0.0 0.0 1.0

5 30.0 18.0 1.06 50.0 5.0 1.0

Transmission Line Data:LineID.

No

Send BusNo.

ReceiveBus No.

ResistP.U

Reactance

P.U.


RatingMVA

1 1 6 0.123 0.518 0.0 552 1 4 0.080 0.370 0.0 653 4 6 0.087 0.407 0.0 304 5 2 0.282 0.640 0.0 555 2 3 0.723 1.050 0.0 40

Transformer Data:TransformerID.No

Send (*)Bus No.

ReceiveBus No.

Resist.P.U

ReactanceP.U.

Tap Ratio RatingMVA

1 6 (*) 5 0.0 0.300 1.000 302 4 (*) 3 0.0 0.133 1.000 55

(*) Note: The sending end bus of a transformer should be the tap side.

Shunt Element Data:Shunt ID No. Bus ID. No. Rated Capacity

MVAR *1 4 2.02 6 2.5

(*) Note: Sign for capacitor : +veSign for Inductor : -ve

Write the following questions answer:-1. What is the need of load flow solution?2. Mention the advantages of Newton Raphson method?3. Compare Gauss Seidel & Newton Raphson method of load flow solution.4. When the generator bus is treated as load bus?5. Why do we go for iterative methods to solve load flow problems?


8/13

It is proposed to conduct fault analysis on two alternative configurations ofthe 4 - bus system given in Figure.

Figure: Four Bus System

G1, G2 : 100MVA, 20kV, x+

= x-= xd = 20%; x

0= 4%; xn = 5%

T1, T2 : 100MVA, 20kV/345kV ; xleak = 8%

L1, L2 : x+

= x-= 15% ; x

0= 50% on a base of 100MVA

The first configuration, case (a), comprises star-star transformers and thesecond configuration, case (b), comprises star-delta transformers.

(i) For a three phase to ground (solid) fault at bus 4, determine thefault current and MVA at faulted bus, post fault bus voltages, faultcurrent distribution in different elements of the network usingThevenins equivalent circuit. Draw a single-line diagram showing theabove results.

(ii) Check the results obtained in (i) using available fault analysissoftware.


1. Define power invariance?

2. What is an unsymmetrical fault? List the various unsymmetrical faults.3. What is the need for short circuit studies or fault analysis?4. What are symmetrical components?5. What are the assumptions made in short circuit analysis?


9/13

A power system comprising a thermal generating plant with four 555 MVA, 24kV,and 60HZ units supplies power to an infinite bus through a transformer and twotransmission lines

FIG: Single Machine Infinite Bus System

The data for the system in per unit on a base of 2220 MVA, 24 kV is given below:

An equivalent generator representing the four units, characterized by classical modXd = 0.3 p.u ; H= 3.5 MW-s/MVA ; Transformer: X = 0.15 p.u

Line 1 : X = 0.5 p.u ; Line 2 : X = 0.93 p.u

Plant operating condition:

P = 0.9 p.u ; Power factor: 0.9 lagging; Et = 1.0 p.u

It is proposed to examine the transient stability of the system for a three-phase-tground fault at the end of line 2 near H.T bus occurring at time t= 0 sec. The fault i

cleared at 0.07 sec. by simultaneous opening of the two circuit breakers at both theends of line 2.


1. Define transient stability.2. Write any three assumptions made upon transient stability.3. What the methods are considered for improving transient stabilitylimit?4. What is Voltage Collapse?5. Define critical clearing angle.


10/13

A power system comprising a thermal generating plant with four 555MVA, 24kV, 60HZ units supplies power to an infinite bus through atransformer and two transmission lines

FIG : Single Machine Infinite Bus System

The data for the system in per unit on a base of 2220 MVA, 24 kV is

given below:An equivalent generator representing the four units, characterized byclassical model:Xd = 0.3 p.u ; H= 3.5 MW-s/MVATransformer: X = 0.15 p.u ; Line 1 : X = 0.5 p.u ; Line 2 : X = 0.93 p.uPlant operating condition:

P = 0.9 p.u ; Power factor: 0.9 lagging; Et = 1.0 p.u

It is proposed to examine the small-signal stability characteristics of

the system given in this problem about the steady-state operating conditionfollowing the loss of line 2; Assume the damping coefficient KD = 1.5 p.utorque / p.u speed deviation.

(a) Write the linearized swing equation of the system. Obtain thecharacteristic equation, its roots, damped frequency of oscillation in Hz,damping ratio and undamped natural frequency. Obtain also the force-freetime response (t) for an initial condition perturbation (0) = 5 and(0)=0,using available software.

Write the following questions answer:

1. Define power system stability.2. What is meant by an infinite bus?3. Define interia constant (H).4. What are the assumptions made by solving swing equation?5. What are the methods of maintaining stability?


11/13

It is proposed to simulate using the software available the load-frequencydynamics of a single-area power system whose data are given below:

Rated capacity of the area = 2000 MWNormal operating load = 1000 MW

Nominal frequency= 50 HzInertia constant of the area = 5.0 s

Speed regulation (governor droop)of all regulating generators = 4percent Governor time constant = 0.08 sTurbine time constant = 0.3 s

Assume linear loadfrequency characteristics which means the connectedsystem load increases by one percent if the system frequency increases by

one percent.

The area has a governor control but not a load-frequency controller. Thearea is subjected to a load increase of 20 MW.

(a) Simulate the load-frequency dynamics of this area using availablesoftware and check the following:

(i) Steady state frequency deviation fs in Hz. compare it with the

hand-calculated value using Area Frequency Response Coefficient (AFRC).

(ii) Plot the time response of frequency deviation f in Hz and changein turbine power PT in p.u MW upto 20 sec. What is value of the peak

overshoot in f?


1. What is area control error?2. What is the function of load frequency control?3. Define per unit droop.4. What is a need of speed changer?5. What are the assumptions made in dynamic response of uncontrolled case?


12/13

In a power system with negligible transmission loss, the system loadvaries from a peak of 1200 MW to a valley of 500 MW. There arethree thermal generating units which can be committed to take thesystem load. The fuel cost data and generation operation limit dataare given below.

In hundreds of rupees per hour:

F1 = 392.7 + 5.544 P1 + 0.001093 P12

; P1 in MW

F2 = 217.0 + 5.495 P2 + 0.001358 P22

; P2 in MW

F3 = 65.5 + 6.695 P3 + 0.004049 P32

; P3 in MW

Generation limits:

150 P1 600 MW

100 P2 400 MW

50 P3 200 MW

There are no other constraints on system operation. Obtain an optimum(minimum fuel cost) unit commitment table for each load level taken insteps of 100 MW from 1200 to 500. Adopt brute force enumerationtechnique. For each load level obtain economic schedules using theEconomic Dispatch Program developed in exercise 10.5.1 for eachfeasible combination of units and choose the lowest fuel cost scheduleamong these combinations.

Show the details of economic schedule and the component and total costs ofoperation for each feasible combination of units for the load level of 900MW.


1. What is the purpose of economic dispatch?2. Draw incremental fuel cost curve.3. What is meant by total generator operating cost?

4. List the various constraints in the modern power systems.5. Name the methods of finding economic dispatch.


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power system simulation lab - questions

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