Rr320203-modelling-of-power-system-components

Set No. 1

Code No: RR320203

III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008 MODELLING OF POWER SYSTEM COMPONENTS (Electrical & Electronic Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. Write short notes on the following. (a) An oriented graph and relevant matrices. (b) Cut-set schedule and tie-set schedule.

[8+8]

2. Derive the expressions for Bus admittance and impedance matrices by singular transformation. [16] 3. Describe the procedure of modification of Zbus by adding mutually coupled branch from existing buses (p) and (k). [16] 4. (a) (a) Two branches connected between buses 2-3 and 3-1 having impedances equal to j0.25 pu are coupled through mutual impedance Zm = j0.15 pu. Find the nodal admittance matrix for the mutually coupled branches and write the corresponding nodal admittance equations. (b) What is primitive admittance and impedance matrix. Bring out the significance of system admittance matrix. [8+8] 5. (a) Explain the primitive network three phase representation of a component in admittance form. (b) For a rotating element, find the sequence impedance matrix from phase impedance matrix using symmetrical component transformation matrix. 012 (c) Find zpq given   j0.4 j0.1 j0.1 abc zpq =  j0.2 j0.6 j0.2  j0.3 j0.3 j0.8

[4+6+6]

6. Derive the relevant models for steady state and transient modes of operation of synchronous generator with relevant phasor diagrams and equations. Take saliency into consideration. [16] 7. (a) Develop the mathematical model of hydraulic value actuator in speed governing system. (b) Two generators rated 200Mw and 400Mw are operating in parallel. The droop characteristics of their governors are 4% and 6% respectively from no-load to full-load. Assuming that the generator are operating at 50Hz, how a load of 500Mw be shared between them. [8+8] 8. (a) Explain about the various performance requirements of excitation system. 1 of 2

Set No. 1

Code No: RR320203 (b) Explain the elements of an excitation system. ⋆⋆⋆⋆⋆

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[8+8]

Set No. 2

Code No: RR320203

III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008 MODELLING OF POWER SYSTEM COMPONENTS (Electrical & Electronic Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) For the power system shown in figure 1a. Obtain the bus incidence matrix A. Take ground as reference. Is this matrix unique? Explain.

figure 1a (b) For the same system shown above, obtain branch path incidence matrix k, and basic cut-set matrix B. [8+8] 2. Derive the expressions for Bus admittance and impedance matrices by singular transformation. [16] 3. Describe the procedure of modification of Zbus by adding mutually coupled branch from existing buses (p) and (k). [16] 4. (a) What is nominal and off-nominal transformer tap settings? Derive the relationships between primary inputs and secondary outputs of a transformer on nominal ratio using admittances in matrix form. (b) What is phase shifting transformer? Bring out its significance in power system. Draw basic equivalent circuit of phase shifting transformer with nominal tap ratio and solve this circuit for terminal currents bringing out their relationship with input and output voltages. [8+8] 5. Develop the expressions for formation of three phase ZBU S for the element which is added between two existing buses in a partial network. [16] 6. (a) For basic types of loads at a bus, develop the mathematical models and represent their characteristics. (b) A 2 pole 50 Hz, Turbo generator has a rating of 60 MVA. The Rotor has a mass moment of inertia of 9000 Kgm2 . Calculate its inertia constant in MJ/MVA and its angular momentum in MJ-sec/elec. degree. [10+6]

1 of 2

Set No. 2

Code No: RR320203

7. (a) Develop the mathematical model of hydraulic value actuator in speed governing system. (b) Two generators rated 200Mw and 400Mw are operating in parallel. The droop characteristics of their governors are 4% and 6% respectively from no-load to full-load. Assuming that the generator are operating at 50Hz, how a load of 500Mw be shared between them. [8+8] 8. (a) Why AVR is required for Generator? (b) Give alternator voltage regulator scheme with the help of a neat schematic diagram. Explain the importance of all the components in an AVR. (c) Give block diagram of automatic voltage regulator scheme and hence explain various blocks in it. [4+6+6] ⋆⋆⋆⋆⋆

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Set No. 3

Code No: RR320203

III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008 MODELLING OF POWER SYSTEM COMPONENTS (Electrical & Electronic Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Define the following terms with suitable example: Basic i. ii. iii. iv. v.

tree branches links co-tree loop.

(b) Write the relation among the number of nodes, number of branches, number of Links and number of elements. (c) For the graph given in figure 1, draw the tree and the corresponding co-tree. Choose a tree of your choice, and hence write the cutest schedule. [5+2+9]

figure 1 2. (a) For the network shown below, draw its graph and mark also a tree. Give the total number of edges (i.e. elements), nodes, buses and branches for this graph. Write also its nodal equations and determine the elements of YBus matrix directly by inspection. (b) For the same network, write the loop equations and hence determine the elements of Zloop matrix directly by inspection. Values shown are currents & admittances Figure 2. [12+4]

Figure 2 1 of 3

Set No. 3

Code No: RR320203

3. (a) Explain why inverse technique is not suitable for predetermination of ZBus from YBus of a large power system. (b) The ZBus matrix for the network shown Figure 3 below is found to be  j0.183 j0.078 j0.141  ZBus = j0.078 j0.148 j0.106 . The line between busses 1 and 3 with j0.141 j0.106 j0.267 Z13 =j0.56 is removed by the simultaneous opening of CBs at both ends of the line. Determine ZBus new matrix. [4+12]

Figure 3 4. (a) What is nominal and off-nominal transformer tap settings? Derive the relationships between primary inputs and secondary outputs of a transformer on nominal ratio using admittances in matrix form. (b) What is phase shifting transformer? Bring out its significance in power system. Draw basic equivalent circuit of phase shifting transformer with nominal tap ratio and solve this circuit for terminal currents bringing out their relationship with input and output voltages. [8+8] 5. (a) Explain the primitive network three phase representation of a component in impedance form. (b) Show that for a stationary element, the phase impedances matrix of a component is diagonalised using symmetrical component transformation. (c) Define the bus incidence matrix of a Power system network whose graph is shown in figure 5. [6+6+4]

2 of 3

Set No. 3

Code No: RR320203

Figure 5 6. Derive the relevant models for steady state and transient modes of operation of synchronous generator with relevant phasor diagrams and equations. Take saliency into consideration. [16] 7. (a) Develop the mathematical model of hydraulic value actuator in speed governing system. (b) Two generators rated 200Mw and 400Mw are operating in parallel. The droop characteristics of their governors are 4% and 6% respectively from no-load to full-load. Assuming that the generator are operating at 50Hz, how a load of 500Mw be shared between them. [8+8] 8. Explain the functional blocks of Automatic voltage regulator. ⋆⋆⋆⋆⋆

3 of 3

[16]

Set No. 4

Code No: RR320203

III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008 MODELLING OF POWER SYSTEM COMPONENTS (Electrical & Electronic Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Obtain the oriented graph of the network whose fundamental cut set matrix is given below. (b) Define primitive network and network. Show the representation of a network component both impedance form and admittance form and give the performance equations both in impedance and admittance form. [8+8] Elements BASIC CUT SETS A B C D

1 1 0 0 0

Branches 3 5 6 0 0 0 1 0 0 0 1 0 0 0 1

Links 2 4 7 0 -1 -1 1 1 1 1 1 0 0 0 -1

2. Derive the expressions for Bus admittance and impedance matrices by singular transformation. [16] 3. Describe the procedure of modification of Zbus by adding mutually coupled branch from existing buses (p) and (k). [16] 4. (a) Write a detail note on tap-changing and regulating transformer. (b) Explain the necessity of transformer modelling for power system studies. [10+6] 5. (a) Explain the primitive network three phase representation of a component in impedance form. (b) Show that for a stationary element, the phase impedances matrix of a component is diagonalised using symmetrical component transformation. (c) Define the bus incidence matrix of a Power system network whose graph is shown in figure 5. [6+6+4]

Figure 5 1 of 2

Set No. 4

Code No: RR320203

6. Clearly explain how a synchronous generator is modeled for steady state analysis. Draw the phasor diagram and obtain the power angle equation for a non salient pole synchronous generator connected to an infinite bus. Sketch the power angle curve. [16] 7. (a) Develop the mathematical model of primary and secondary Control Loops and derive the transfer functions of each block. (b) Determine the primary Automatic load frequency control loop parameters for the following system data: Total rated area capacity = 2000 Mw Normal operating load = 1000 Mw Inertia constant = 5 sec. Regulation = 2.4 hz/ p.u. Mw Assume load frequency depending is linear. [10+6] 8. Explain the functional blocks of Automatic voltage regulator. ⋆⋆⋆⋆⋆

2 of 2

[16]