Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech IV ELECTRICAL DISTRIBUTION SYSTEMS Previous Question Paper (July/August - 2022 - R18)
Answer any five questions. All questions carry equal marks.
Main
Explain the various factors affecting the distribution system planning.
Answer
Distribution system planning is a complex process aimed at providing reliable and economical power. Key factors include:
- Load Forecasting: Accurate estimation of future load growth, including residential, commercial, and industrial demands, is essential for sizing equipment.
- System Reliability: Planning must account for redundancy and contingency measures to minimize downtime during faults.
- Voltage Regulation: Maintaining voltage within statutory limits is critical, requiring the strategic placement of capacitors and voltage regulators.
- Economic Constraints: The total cost, including capital investment, operation, maintenance, and energy losses, must be optimized.
- Geographical and Environmental Factors: The layout of the distribution network is constrained by existing infrastructure, right-of-way issues, and environmental regulations.
- Technological Advancements: Integration of smart grid technologies, distributed generation, and automation systems significantly influences planning strategies.
Assume that a load of 120 kW is connected at the Riverside substation. The 15-min weekly maximum demand is given by 70 kW, and the weekly energy consumption is 4100 kWh. Assuming a week is 7 days; determine the demand factor and the 15-min weekly load factor of the substation.
Answer
Given: Connected Load = 120 kW, Maximum Demand = 70 kW, Weekly Energy Consumption = 4100 kWh, Time = 7 days.
1. Demand Factor:
2. Load Factor:
First, calculate the total possible energy if the maximum demand were constant over the week:
The demand factor is 0.5833 and the weekly load factor is 0.3486.
Given the A, B, C, D constant of a radial feeder, illustrate how the receiving end voltage can be computed, for a specified load.
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Explain the various factors that are to be considered in selecting primary feeder rating? Give a neat sketch of typical primary distribution feeder.
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How do you fix the rating of a distribution sub-station? Explain.
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Explain the optimal location of sub-stations by perpendicular bisector rule.
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Derive the expression for the total series voltage drop and total copper loss per phase of a uniformly distributed load. Give the assumption made, if any.
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Explain the method to analyze distribution feeder cost.
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What are the objectives of distribution system protection? Discuss.
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Describe the principle of operation of fuse with neat diagram? List out its merits and demerits.
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Explain the general coordination procedure of protective devices.
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Explain the protection coordination of fuse-fuse.
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Illustrate the economic justification of shunt capacitors for distribution systems.
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A sub-station supplies power to the following, lighting load 100-kW, a 3-phase induction motor 400 h.p. (298.4 kW), power factor 0.8, efficiency 0.92, a 3-phase synchronous motor giving 100 A at 500 V at an efficiency of 0.94. What must be the power factor of the synchronous motor in order that the power factor of the supply station may be unity?
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Explain the importance of voltage control for distribution systems.
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Describe the effect of series capacitors on voltage control for distribution systems.
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