JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV ELECTRICAL DISTRIBUTION SYSTEMS Previous Question Paper (September - 2020 - R16)
Answer any five questions. All questions carry equal marks.
Main
What is load factor? How is it related to load factor? Explain its significance.
Answer
Load factor is defined as the ratio of the average load over a designated period of time to the maximum peak load occurring in that same period. It is expressed as:
The average load is calculated by dividing the total energy consumed during the period by the number of hours in that period. The load factor is always less than or equal to unity, as the average load can never exceed the peak load.
The significance of the load factor lies in its role as a measure of the utilization of the distribution system capacity. A high load factor indicates that the load is relatively constant, which allows for more efficient use of equipment and reduces the cost per unit of electricity generated and distributed. Conversely, a low load factor implies that the system is underutilized for most of the time, leading to higher capital costs per unit of energy delivered. Improving the load factor is essential for minimizing losses and optimizing the return on investment for distribution infrastructure.
The load curves of two different categories of loads and system peak load are as follows. Determine the diversity factor and coincidence factor for the system. Peak load for industrial load = 2000 kW; Peak load for residential load = 3000 kW and System peak load = 2500 kW.
Answer
Given:
- Peak load of industrial load (P_ind) = 2000 kW
- Peak load of residential load (P_res) = 3000 kW
- System peak load (P_sys) = 2500 kW
The diversity factor is the ratio of the sum of individual maximum demands to the maximum demand of the entire system:
The coincidence factor is the reciprocal of the diversity factor:
How do you choose the secondary feeder arrangement from reliability point of view? Discuss the arrangements with suitable diagrams.
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Give a line diagram of loop (ring) type primary feeder system and mention the different component parts. What are the considerations for planning loop (ring) feeders?
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What are the factors to be considered for location of a Substation? What are the benefits obtained from optimal location of a Substation?
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Explain how do you calculate the rating of a distribution substation?
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Discuss the method to analyze the distribution feeder cost.
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Show that the power loss due to the load currents in conductors in a single phase two wire ungrounded system with full capacity neutral (3-wire system) is six times more than that in the equivalent 3-phase 4 wire system.
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Explain the co-ordination procedure between a main fuse and a sectional fuse?
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A single phase, 3-wire distribution line 120V-0-120V, feeds a load of 10KVA line to line and 3KVA on each line to ground. The Transformer is 7620V/240V, 25KVA with 5% impedance. The line impedance is j0.05 per wire. Calculate the fault current and fault MVA for the following: i) L-L fault and ii) L-G fault, 1 km from Transformer.
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Explain the coordination procedure between a fuse and auto-recloser.
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Explain the principle of operation of Circuit breaker.
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Compare and explain role of shunt and series capacitors in p.f correction.
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An industry has a total induction motor load of 100 h.p, efficiency 90% and power factor 0.82 lagging. It is necessary to correct the p.f to 0.92 lagging. Determine the capacitor bank needed. If the capacitor bank has 3% losses, find the % increase in power take and the p.f with capacitors.
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Explain the different methods for voltage control in distribution systems.
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