NARAYANA ENGINEERING COLLEGE::NELLORE
DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING
QUESTION BANK
UNIT I
LOAD MODELING AND CHARACTERISTICS
1. Relate the relationship between the load factor and loss factor (BL=1)
2. Explain the characteristics of residential, Agricultural, industrial and commercial loads. (BL=2)
3. (A) Explain briefly classification of loads? How is load modeling done in distribution networks? (BL=2)
(B) A power supply is having the following loads: (BL=5)
Type of load Maximum demand Diversity of group Demand factor
Domestic 1500 KW 1.2 0.80
Commercial 200 KW 1.1 0.80
Industrial 1000 KW 1.25 1.0
If the overall system diversity factor is 1.35, determine:
(i) Maximum demand
. (ii) Connected load of each type
4. (A)Define Load factor and Loss factor (BL=1)
(B) Assume that the annual peak load of a primary feeder is 2500 kW, at which the power is 70 kW per three
phases. Assuming an annual loss factor of 0.15. Determine: (i) The average annual power loss
(ii) The total annual energy loss due to the copper losses of the feeder. (BL=5)
5. (A)Explain the following term: (BL=2)
(i) Maximum demand. (ii) Coincident demand. (iii) Contribution factor.
(B) Assume that the annual peak load of a primary feeder is 2000 kW, at which the power is 80 kW per three phases.
Assuming an annual loss factor of 0.15. Determine: (i) The average annual power loss
(ii) The total annual energy loss due to the copper losses of the feeder. (BL=5)
6. (A) Define Coincidence Factor and Contribution Factor(BL=1)
(B) A 120 MW substation delivers 120 MW for 4 Hrs, 60 MW for 10 Hrs and shut down for rest of each day.
It is also shut down for the maintenance for 30 days each year. Calculate its annual load factor. (BL=1)
7. (A) Write short notes on load modeling and its characteristics(BL=1)
(B) A generating station has the following daily load cycle. (BL=1)
Time(hrs) 0-6 6-10 10-12 12-16 16-20 20-24
Load(mw) 30 40 20 70 50 40
Draw the load curve and find:i)Maximum demand ii)Units generated per day iii)Average load iv)Load factor
8. (A) The maximum demand of a generating station is 200mw.The annual load factor being 60%.calculate the
total electrical energy generated per year? (BL=1)
(B) The annual peak load on a 30mw power station is 25 mw. The power station supplies loads having
maximum demands of 10mw,8.5mw,5mw,and 4.5mw.The annual load factor is 45%.
Find i)Average load ii)Energy supplied per year iii)Demand factor iv)Diversity factor(BL=1)
UNIT II
CLASSIFICATION OF DISTRIBUTION SYSTEMS
1.Draw the single line diagram of radial type primary feeder and mention the factors that influence the selection
of primary feeder. (BL=5)
2.Explain basic design practice of secondary distribution system and also discuss about secondary banking. (BL=2)
3.(A) List the factors affecting the primary feeder voltage levels and primary feeder loading. (BL=4)
(B) Consider a three phase, 3 wire, 240 V secondary system with balanced loads at A, B and C as shown in figure below.
Determine the voltage drop in one phase of laterals. (BL=5)
4.(A)Compare DC and AC distribution systems. (BL=2)
(B) A 2-wire DC distributor AB, 600 m long as loaded as under:
Distance from 150 300 350 450
(mts):
100 150 250 300
Loads(amps
)
The feeding point A is maintained at 440 V and that of B at 430 V. If each conductor has a resistance of 0.02 per 100 m, Find: (i)
The current supplied from A to B. (ii) The power dispatched in the distributor. (BL=1)
5.(A) Discuss the design consideration of loop type primary feeders. ((BL=6)
(B) Discuss the requirements and design features of distribution systems(BL=6)
6.(A) compare underground and overhead distribution systems(BL=2)
(B) Discuss the various factors effecting the selection of the primary feeder rating. (BL=6)
7. A single phase distributor 2 km long supplies a load of 120A at 0.8 p.f. lagging at its far end and a load of 80A at 0.9 p.f
lagging at its mid point.Both power factors are referred to the voltage at the far end.The resistance and reactance per km are
0.05Ώ and 0.1 Ώ respectively.If the voltage at the far end is maintained at 230v, Find 1)voltage at the sendind end 2)phase
angle between voltages at the two ends. (BL=1)
8. Consider the singe phase radial distributor shown in the figure below. The magnitude of load currents, p.fs and distances are
indicated in the figure. The resistance and reactance of each wire are 0.1 Ω per km and 0.2 Ω per km respectively. It is required to
maintain voltage at point B as 230∠00 volts. Find voltage drop in the three sections and total voltage drop in the feeder. The p.f.
angles of individual loads are w.r.t. voltage at point B.
(BL=1)
UNIT III
SUBSTATIONS
1.(A) Explain the classification of substations according to design. (BL=2)
(B) Compare the four and six feeder patterns of substation service area if they are thermally loaded. (BL=2)
2.(A) What are the factors considered when selecting a location for a substation? .
(BL=1)
(B) List the benefits obtained through optimal location of substation. (BL=1)
3.(A)How do you analyze a substation service area with ‘n’ primary feeders? ((BL=4)
(B)Discuss the features, advantages and disadvantages of main and transfer bus bar arrangement and one and half breaker system
arrangement. (BL=6)
4.(A) Explain the single bus bar system with sectionalization and what are its merits and demerits
(BL=2)
(B) Give a detailed analysis of square shaped and hexagonal shaped distribution substation areas and compare their loading
problem. (BL=4)
5.(A) Show that if the voltage drops are limited, six feeders can carry only 1.25 times as much load as the four feeders.?
(BL=1)
(B) Make a comparison between indoor and outdoor substations (BL=2)
6.(A) Explain how to decide the rating of distribution substation? (BL=2)
(B) Mention the various factors that are to be considered in selecting the ideal substations(BL=1)
7.(A) Explain the Double bus-Single breaker scheme? (BL=2)
(B) Explain the Double bus-double breaker scheme? (BL=2)
8.(A) Show that six feeders can carry 1.50 times as much load as the four feeders if they are thermally loaded
(BL=1)
(B) Explain the Ring bus scheme? (BL=2)
UNIT IV
POWER FACTOR IMPROVEMENT
1.(A) Explain the manual method of solution for radial distribution system(BL=2)
(B) Find the equation for load power factor for which the voltage drop is maximum (BL=1)
2. A 3 Phase, 500 H.P, 50 Hz, 11 kV star connected induction motor has a full load efficiency of 85% at a lagging p.f. of 0.75 and
Connected to a feeder. If it is desired to correct it to a p.f. of 0.9 lagging load. Determine the following: (i) The size of the
Capacitor bank. (ii) The capacitance of each unit if the capacitors are connected in star as well as delta
(BL=5)
3. (A) Explain the procedure employed to determine the best capacitor location. (BL=2)
(B)A 40 kW induction motor has power factor 0.95 and efficiency 0.85 at full1oad, power factor 0.7 and efficiency 0.65 at half-
Load. At no-load, the current is 20% of the full-load current and power factor 0.2. Capacitors are supplied to make the line
Power factor 0.9 at half-load. With these capacitors in circuit, find the line power factor at: (i) Full load. (ii) No-load. (BL=1)
4.(A) Explain the role of shunt and series capacitors in power factor correction. Compare their performance in power factor
Correction. (BL=2)
(B) Discuss the need of power factor improvement in distribution system. (BL=6)
5. (A) Explain the effect of shunt compensation on distribution system. (BL=2)
(B) A synchronous motor improves the power factor of a load of 300 kW from 0.8 lagging to 0.9 lagging. Simultaneously the
Motor carries a load of 150 kW. Determine: (i) The leading kVAR taken by the motor. (ii) kVA rating of the motor. (iii)
Power factor at which the motor operates(BL=5).
6. Show that power loss due to load currents of the two phase, 3 wire lateral with full capacity neutral is exactly equal to
2.25 times larger than the one in which equivalent three phase lateral is used. Also prove that VD pu, 2 =2.1xVDpu, 3 for the
above system. (BL=1)
7. Consider a three phase, 3 wire, 440 V secondary system with balanced loads at A, B and C shown in figure. Determine:
(BL=5)
(i) Total voltage drop.
(ii) Real power / phase for each load.
(iii) Reactive power / phase for each load.
(iv) The kVA output and load p.f. of the distribution transformer
8.(A) Explain the disadvantages of low power factor. (BL=2)
(B) A single-phase motor connected to a 240V, 50 Hz supply takes 20 A at p.f. of 0.75 lag. A capacitor is shunted across
the motor terminals to improve the p.f to 0.9 lag. Determine the capacitance of the capacitor to be used. (BL=5)
UNIT V
DISTRIBUTION AUTOMATION
1. (A) Explain the benefits of Distribution Automation as applied to:(a) Substation automation
(b) Feeder automation
2.What are the components of SCADA in distribution automation. (BL=1)
3.Discuss about consumer information service and automatic meter reading. (BL=6)
4.(A) Discuss the communication requirements for distribution system automation (BL=6)
(B)Discuss the role of geographical information system in distribution system automation. (BL=6)
5.Discuss about (a)Distribution Automation(BL=6)
(b) Project Planning
6. Discuss about Automation Systems. (BL=6)
7. Explain the SCADA system for distribution system automation. (BL=2)
8. Discuss about consumer information service and geographical information system. (BL=6)
Signature of Staff HOD PRINCIPAL
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